Sino Petrochemical Corporation Standard

Power Design Specification For Petrochemical Enterprise Units

SHJ38-91

1991 Beijing

Chapter I General

Article 1.0.1 This specification applies to the power design of up to 10 KV for newly built, reformed or expanded large and medium size production units of petrochemical enterprises (including oil refining, chemical and chemical fiber units, called “the unit(s)” hereunder).

Article 1.0.2 The following principles shall be observed for the power design of the units.I. The technical and economic policies of the state shall be earnestly implemented, so as to provide cost effective and rational designs that use sophisticated technology and ensure personal safety and reliable power supply.II. The relationship between short term construction and long term development shall be so properly handled in line with the features, sizes and development plans of projects that the two can be well combined, with the short term construction to be given the first place and proper rooms and conditions to be reserved for future expansion and development.III. Reasonable arrangement and design plans shall be worked out through overall planning and all-around consideration based on the load nature, capacity and environmental conditions, etc.IV. Saving of energy shall be paid attention to and the non-ferrous metal and materials shall be rationally saved.

Article 1.0.3 In implementation of this specification, relevant stipulations and requirements under state and sector standards and codes shall also be conformed with.

Chapter II Load Classification & Power Supply Requirements

Section I Load Classification

Article 2.1.1 The power loads of the units shall be classified, according to their importance in the production process and their reliability and continuity requirements for power supply, into class 0 load (security load), class1 load (essential continuous operation load), class2 load (normal continuous operation load) and class 3 load (normal load).

Article 2.1.2 A class 0 load means a load for which the power supply must be guaranteed at a sudden failure of power supply for the unit, to ensure safety shutdown of the unit and avoid explosion, fire, intoxication, personal injury or damage of key equipment, or in an emergency, to allow prompt handling of the emergency, prevent expansion of the accident, protect the key equipment and rescue and evacuate the operators.There are normally the following types of class 0 load:I. At a power failure, the automatic program control equipment and their actuators and accessory equipment that ensure safety shutdown, such as the computers, instruments, relay protection devices, essential material inlets/outlets and drainage valves for the units;II. At a power failure, the automatic feeding and mixing equipment for quickly adding in the necessary assistants to stop the chemical reaction when a quick interruption of the chemical reaction need be ensured but the reactants in the equipment can not or should not be drained immediately, and the spinning head electrical heater in chemical fiber production, etc.;III. During the operation or coasting at power failure of large size key units, the safety measures to protect the equipment from damage, such as the lube oil pump, etc.;IV. To ensure safety operation, emergency handling and personnel rescue and evacuation, the emergency lighting, communication, industrial TV, fire alarm and other systems that are necessary for the units.

Article 2.1.3 A class 1 load means the power load of such a large or medium size unit whose sudden loss of operation power supply will upset the key continuous production process, resulting in major economic losses, such as rejection and loss of large quantity of products and stocks, carbonation of catalysts and intoxication, blocking of material lines or equipment and so on, and which can only resume operation a long time after the power supply is resumed, and the power load of the utilities serving to ensure its normal operation.

Article 2.1.4 A class 2 load means the power load of such a unit whose sudden loss of operation power supply will result in significant economic losses, such as reduction of output or stopping of production, and which will resume normal operation shortly after the power supply is resumed, and the power load of the utilities serving to ensure its normal operation.

Article 2.1.5 A class 3 load means any other power load that does not fall into class 0, class 1 or class 2 loads.

Section II Power Supply Requirements of Different Classes of Load

Article 2.2.1 class 0 load shall have the power supplied from an independent safety power supply system. It is strictly forbidden to connect any non class 0 load into the safety power supply system.

Article 2.2.2 Wherever safety measures are necessary during operation, non electrical safety measures shall be adopted first in the process and equipment design and the load may only be listed into class 0 loads when the said measures can not meet the requirements. The use of class 0 load shall be strictly controlled to the minimum.

Article 2.2.3 The safety power supply includes the following commonly used types:I. Uninterrupted power supply unit1. DC battery unit;2. Static type uninterrupted power supply unit;3. Rotating type uninterrupted power supply unit.II. Fast self-started diesel generator unit or other types of generator unit.III. External independent power supply induced in for the production unit, which meets the safety requirements.

Article 2.2.4 The operation equipment supplied from the safety power supply shall have the power supplied by the operating power supply under normal conditions and by the safety power supply only at a failure of the operating power.

Article 2.2.5 class 1 load shall have the power supplied from two power sources, which shall meet one of the following conditions:I. The two power sources are independent from each other;II. Although the two power sources are associated with each other, one can automatically and quickly cut off the connection at a failure to let the other one ensure normal power supply.

Article 2.2.6 When the production unit is provided with a generator unit, it shall be determined, according to the power load, the type and capacity of the generator and the operating mode during normal operation, etc., whether the generator may be used as an independent operating power source. If it may be so used and achieving of two external power sources is really difficult, class 1 load may also have the power supplied by a single external power source.

Article 2.2.7 The power for class 2 load should be supplied by two power sources and, when it is difficult to obtain two, may also be supplied by one power source.

Article 2.2.8 Class 3 load may have the power supplied by a single power source.

Article 2.2.9 When the power for the unit is supplied through two or more circuits that are in simultaneous operation and on standby for each other under normal conditions, the power supply line shall be so designed that at a failure of one of the circuits, the remaining circuit(s) can still maintain normal power supply for the whole unit and can satisfy the restart-up of the motor.

Article 2.2.10 In power design for the units, no consideration is to be taken of such a case that, when one circuit fails or is under maintenance, the other circuit fails at the same time.

Chapter III Automatic Power Switchover & Motor Restart System

Section I Automatic Power Switchover

Article 3.1.1 The power sources for both class 0 and class 1 loads of the production units shall be provided with automatic power switchover units.

Article 3.1.2 The power supply and distribution system for the units should have automatic power switchover unit(s) installed at one or more of the following locations: I. The incoming line and bus sectionalized breaker for a 6 ~ 10KV substation;II. Sectionalized breakers for 380V/220V incoming line and bus with class 0 and class 1 loads;III. The mains incoming line for emergency lighting.

Article 3.1.3 Wiring of the automatic power switchover unit shall meet the following requirements:I. At loss of power or power failure caused by any other reasons than action of the current protection for the mains incoming line breaker, the other power supply shall be automatically switched on when its voltage level can meet the requirement;II. The switchover time shall be shortened on condition that the non-synchronous impulse is avoided;III. It shall be ensured that the automatic power switchover unit act only once;IV. When any of the fuses of the potential transformer (PT) is burnt, the low voltage start-up element shall not mal-operate.

Article 3.1.4 When the automatic power switchover unit is used, the overload capacity of the backup power supply and the conditions for motor restart shall be checked. In case the overload capacity of the backup power supply is not sufficient or the motor restart conditions can not be ensured, a part of the secondary load may be cut out when the power supply is automatically switched over.

Article 3.1.5 The automatic power switchover units shall be selectively matched with the relay protection devices:I. When an outgoing feeder is provided with a reactance, the starting voltage of the automatic power switchover unit shall be lower than the bus residual voltage at a short circuit that occurs after the outgoing feeder’s reactance.II. The starting time of the automatic power switchover unit shall exceed the maximum time limit of the outgoing feeder’s short circuit protection by one time step when the outgoing feeder is not provided with a reactance; and shall also exceed the maximum time limit of the upper level substation’s outgoing feeder short circuit protection by one time step when the outgoing feeder of the upper substation is not provided with a reactance either;III. In case of an essential motor that is not allowed to restart, the start time limit of the automatic power switchover unit shall be greater than the action time limit of the said motor’s low voltage protection;IV. The automatic power switchover units for a substation with a synchronous motor, which might be hit by non-synchronous impulse hazard without any measures taken against the non-synchronous impulse, shall not be put into service until the synchronous motor is cut out.

Article 3.1.6 The automatic power switchover units shall be selectively matched with each other and their

action time limits shall be increased by one time step gradually backward from the power supply side. If an automatic recloser is provided on the power supply side, the start time limit of the first step of automatic power switchover unit shall be one time step greater than the action time limit of the said automatic recloser.

Article 3.1.7 In case the selective matching of the automatic power switchover units renders the start time limit too long to satisfy the motor restart requirements, the following measures may be taken:I. The number of steps of the automatic power switchover units may be reduced;II. Quick-acting protections should be adopted for the power supply system to reduce the protection time limit;III. Current blocking should be adopted for the incoming line and, if quick restart is required by the process, it is allowed for the automatic power switchover unit not to be matched with the upper step relay protection and automatic device.

Section II Motor Restart System

Article 3.2.1 The motor restart system means the restart process during the operation in which all the squirrel-cage induction motors (called “the motor(s)” hereunder) provided with restart units can be restarted according to the preset time and batches at restoration of the power supply after a short time of interruption, excluding the automatic putting in of the backup electrical equipment as required by variation in process parameters.

Article 3.2.2 There are the following motor restarting modes:I. Number of motor sets involved in the restart1. All or most of the motors on the bus are involved in the restart;2. Some of the motors on the bus are involved in the restart.II. Conditions of the restart1. Simultaneous restart, namely all the motors requiring restart will be restarted at the same time; 2. Restart in batches, namely all the motors requiring restart will be restarted in batches according to the requirements of the production process and the capacity of the electrical system;3. Restart in steps, namely the restart command will be passed step by step, from the higher step of motor at the time of its restart to the lower step with a time delay, so that all the motors complete the restart process in steps. This mode normally applies to high voltage (HV) motors.III. Action time of restart1. True jump restart, namely the control circuit of the motor keeps the main contact of the starter closed during the entire power failure period and the motor will be restarted upon restoration of the power supply, with the duration of disappearance of the motor’s normal power supply voltage equal to the action time of the automatic device;2. Quasi jump restart, namely the main contact of the starter will be opened when the motor’s power supply voltage disappears and will be closed immediately without any artificial delay to restart the motor when the normal power supply voltage is restored or nearly restored, with the duration of disappearance of the motor’s normal power supply voltage equal to the action time of the automatic device plus the inherent closing time of the starter;3. Delayed restart, namely the main contact of the starter will be opened when the motor’s power supply voltage disappears and will be closed after a certain length of preset time to restart the motor when the normal power supply voltage is restored or nearly restored, with the duration of disappearance of the motor’s normal

power supply voltage equal to the sum of action time of the automatic device, the inherent closing time of the starter and the preset time.

Article 3.2.3 One or more of the following alternatives may be selected according to the specific situations of the engineering design for use singly or in combination as the method of restart:I. Low voltage (LV) asynchronous motors:1. The restarting method composed of time relays It will bring about a longer delay time (30s) and applies to restart in batches or with a diesel generator as the safety power supply;2. The restarting method composed of restarting relays It uses less relays, with simple wiring and short delay (3~4s), and applies to restart of motors in one or two batches;3. The group and batch restarting method composed of time relays it applies to restart in groups and batches;4. The time trunk type restarting method DC power supply, uninterrupted power supply unit (UPS) and AC power supply in automatic switchover will be used as the control power supply and 3 restarting small buses with which the time delays can be adjusted are utilized to flexibly adjust the restarting times and batches of the motors for various production units after restoration of the power supply (in 20s), in order to reduce the impact of the restarting current on the system. This method applies to restart of multiple sets of motors for large size production units.II. For HV asynchronous motors, other than those that are not allowed or not necessary to be restarted and will be cut out at the time of automatic power switchover, the remaining motors shall be restarted with the following 3 methods:1. Time trunk type restarting method it is the same as the above I. 4.;2. Restart in steps It applies to less sets of motors with greater capacity in the production unit; when there are quite a number of motor sets, those with smaller capacities may be combined into one step for restart;3. Simultaneous restarting method It may be adopted according to the conditions of the power supply system if the quantity of motors to be restarted is quite small and the single set capacity and total capacity are not so big.

Article 3.2.4 The conditions necessary for realizing motor restart are as follows:I. During the whole restart process, the total restarting current of the motor group being restarted plus the load current of other power consumption equipment shall not exceed the calculated peak current allowed by the external power supply circuit, normally no greater than 2 times of the secondary side rated current of the workshop distribution transformer or 1.1 times of the rated current of the emergency diesel generator, otherwise, calculations and calibrations shall be made;II. During restarting, the moment of the motor shall be greater than the resistance moment at corresponding mechanical speed;III. During restarting, the minimum allowable value of the bus voltage shall be 85% of the rated voltage while that of the motor end voltage should be 70% of the same and, if explicitly specified otherwise by the manufacturer, they shall meet the requirements of the manufacturer;IV. After one time of hot restart, the temperature rise of the stator winding of a restarted large size HV motor shall not exceed the value specified under the motor manufacture standard.

Article 3.2.5 Selective coordination between motor restart and the relay protection and automatic units are described as follows:

I. For HV motors to be restarted with time delay restarting method, its low voltage trip setting shall be lower than the minimum voltage required for restart;II. The over current protection setting of the incoming line breaker shall be calibrated with the most severe restarting current;III. In order to avoid non-synchronous impulse, the real jump restart should not be switched on till the residual bus voltage falls lower than 40% of the rated voltage; and when the method of restart in batches is adopted for the quasi-jump restart, those motors with greater capacities should be grouped into the second and third batches of restart;IV. The selective coordination between various steps of automatic power switchover units shall meet the special requirements of restart.

Article 3.2.6 Motor restart shall be coordinated with the process conditions as follows:I. All the motors required by continuity of production shall be restarted;II. Restart of motors shall be in coordination with the automatic control level, the water and gas supply conditions and so on;III. The quantity and sequence of motors to be restarted and the special requirements for specific motors shall be determined by the process specialty and electrical specialty through discussion;IV. The characteristics of the machinery driven by the motor shall be taken into account for restart of motors;V. For a process equipment with restarting measures which has interlock between the main and auxiliary machines, the auxiliary machine shall also be provided with a restarting measure;VI. For utilities equipment that have important functions in process production (e.g. air compressors, pumps and so on), it is also necessary to consider taking restarting measures if otherwise the normal process production is impacted.

Article 3.2.7 The following points shall be paid attention to in calculation of the restarting current:I. No matter what restarting method is used, the restarting current of LV motors with medium or small capacity may be calculated as 6 times of the rated current;II. The restarting currents of HV motors and LV motors with large capacity are related to the duration of power failure and the method of restart and the following values may be taken as the equivalent restarting current’s multiple Ks:Power failure duration 2s Ks = 5.1 5.4Power failure duration 2 ~ 4s Ks = 5.4 6Power failure duration 4s Ks = 6III. When restart is adopted for both HV and LV motors, the summed restarting current shall be calculated according to the most severe conditions in terms of restarting method, restarting interval, failure interval and so on of the HV and LV motors;IV. When one section of HV bus supplies different LV buses, the restarting time of motors on different sections shall be alternated first before the restarting current is calculated according to the total number of motors to be restarted in one batch.

Article 3.2.8 The following points shall be paid attention to in calculation of the restarting voltage:I. For restart in groups, a total equivalent restarting current multiple shall be calculated for all of the motors in one group;II. For restart in batches, respective calculations shall be made for different loads pre-connected to the bus;

III. For restart in steps, it is also necessary to consider, under certain conditions, summing of the restarting currents of all motors;IV. The negative deviation of the normal power supply voltage shall be taken into account for calculation;V. In case of simultaneous restart of both HV and LV motors, the most severe conditions in restarting process need be considered.VI. The system capacity value under the minimum operation mode shall be taken as the basis for calculation of the system impedance.

Article 3.2.9 The following points shall be paid attention to in batching of LV motors for restart in groups:I. According to the requirements of the power supply system and for the restart, coordination of the restarting time of LV motors with that of HV motors and coordination of the restart of motors on different LV buses shall be considered;II. Depending on the ratio between the total capacity of the restarted motors and the rated capacity of the transformer, the restarted motors may be batched in the following ways:1. They should be divided into 3 batches when the total rated capacity of the restarted motors is greater than or equal to 50% of the transformer’s rated capacity;2. They may be divided into 2 batches when the total rated capacity of the restarted motors is 30% ~ 50% of the transformer’s rated capacity;3. Batching may be omitted when the total rated capacity of the restarted motors is less than or equal to 30% of the transformer’s rated capacity.

Article 3.2.10 The time interval for restart of motors in batches should be 2 ~ 3s and the time interval for restart of HV motors in steps should be no more than 1s;For the time trunk type restart using small bus method, the time interval between every two small buses shall be 2 ~ 6s for LV motors and 6 ~ 8s for HV motors.

Article 3.2.11 The requirements for control and signals of the restarting system are described as follows:I. The control circuit of the restarting system shall be provided with control mode selector switch;II. The control mode selector switch should be mounted in the control room and shall have obvious symbol word marking, with indicator lights showing the operation conditions to be provided on the process mimic panel or at other proper locations;III. The control circuit of the restarting control system shall be provided with an automatic canceling measure against exceeding of the allowable restarting time limit.

Chapter IV Explosion & Fire Hazard Environments

Section I General rules

Article 4.1.1 The following principles shall be observed for implementation of this specification:I. During the engineering design, the classes and ranges of the explosion hazard environments shall be determined through analysis and judgment based on the specific situations, especially on the operational practice and working experience;II. When Addendum I, the Petrochemical Unit Explosion Hazard Environment Zoning Table, is used, the zoning in this table shall not be taken as fixed and unchangeable and different operation methods, process flows and production scales shall be taken account of.

Article 4.1.2 It is necessary to use explosion proof electrical equipment that have been tested and accepted by a state explosion protection test institution. A new trial product or a non-approved explosion proof equipment may not be used unless it is provided with an application permit that is equivalent to the explosion proof certificate.

Article 4.1.3 The explosion hazard zones and fire hazard zones shall be divided according to the frequency and duration of occurrence of the explosive mixtures and the hazardous degree and physical status of the fire hazard substances to occur. Based on this, the electrical equipment shall be selected and corresponding precautions shall be taken for substations, electrical lines, grounding and so on, in order to reduce the probability of the explosion and fire disasters caused by sparks, arcs and high temperature of the electrical equipment and lines.

Section II Division of gas or vapor explosion hazard zones

Article 4.2.1 The following substances might form an explosive mixture with air:I. Under atmospheric conditions, such inflammable substances as the vapor or mist of inflammable gas or liquid will form with air an explosive gas mixture;II. The vapor or mist of flammable liquid with its flashing point lower than or equal to the ambient temperature will form with air an explosive gas mixture;III. In case of a possible leakage of the flammable liquid when the material operating temperature is higher than the flashing point of the flammable liquid, the vapor of the same liquid will form with air an explosive gas mixture.

Article 4.2.2 The following conditions must exist simultaneously for occurrence of an explosion in an explosive gas environment:I. There exists the vapor or fist of inflammable gas or liquid, with its concentration exceeding the explosion limit;II. There exist the spark, arc or high temperature that is enough to ignite the explosive gas mixture.

Article 4.2.3 The following explosion protection precautions shall be taken in an explosive gas environment:I. The possibility of simultaneous occurrence of all the conditions leading to an explosion shall be minimized;

II. Measures shall be taken in the process design to eliminate or reduce the production and accumulation of inflammable substances;1. Lower pressure and temperature should be adopted in the process flow to restrict the inflammable substances in the range of the airtight vessel;2. In the process arrangement, the range of the explosion hazard zone shall be limited and reduced, different classes of explosion hazard zones or explosion hazard zones and non explosion hazard zones should be separated and limited within respective buildings or battery limits and the equipment with open fire or high temperature should be arranged at the edge of the battery limit;3. The measure of covering with nitrogen or other inert gases may be taken within the equipment;4. Such measures as safety interlock or addition of polymerization inhibitor in emergency should be taken.III. The following precautions should be taken to prevent formation or reduce the retention duration of the explosive gas mixture:1. Outdoor or open type arrangement should be adopted for the process units;2. Mechanical ventilation equipment shall be provided;3. A plenum shall be provided in an explosive hazard environment;4. Locations in a zone where the explosive gas mixture is easily formed and accumulated shall be provided with automatic measurement instruments and devices which, when the gas or vapor concentration approaches 50% of the lower explosion limit, shall be able to reliably give alarm signals or cut off the power.IV. Measures shall be taken in the zone to eliminate or control the sparks, arcs or high temperature produced by the electrical equipment and lines.

Article 4.2.4 The releasing sources shall be classified by the frequency and duration of releasing of the inflammable substances and shall meet the following requirements:I. Continuous class releasing source: a releasing source expected of long time release or short time frequent release. Those similar to the following cases may be classed under the continuous class releasing source:1. The surface of the inflammable liquid in a storage tank with fixed top cover which is not covered by any inert gas;2. The surface of the inflammable liquid in oil or water separators which is in direct contact with the air; 3. Free vents or other openings that release inflammable gas or vapor into the air frequently or for long periods of time.II. Class 1 releasing source: a releasing source expected of periodic or occasional releasing during normal operation. Those similar to the following cases may be classed under class 1 releasing source:1. The sealing points of pumps, compressors and valves where inflammable substances will be released during normal operation;2. The water drainage system installed on a vessel storing inflammable liquid, which will release inflammable substances into the air during draining in normal operation;3. Sampling points that will release inflammable substances into the air during normal operation. III. Class 2 releasing source: a releasing source expected of no releasing during normal operation or of occasional short releasing if any. Those similar to the following cases may be classed under class 2 releasing source:1. The sealing points of pumps, compressors and valves where no inflammable substances can be released during normal operation;2. Safety valves, air vents and other openings that can not release any inflammable substances into the air

during normal operation;3. Sampling points that can not release any inflammable substances into the air during normal operation.IV. Multi-class releasing source: a releasing source composed of two or three of the above mentioned classes of releasing source.

Article 4.2.5 The explosive gas environment shall be zoned according to the following rules, depending on the frequency and duration of occurrence of the explosive gas mixture:I. Zone 0: an environment where the explosive gas mixture occurs continuously or for a long period of time;II. Zone 1: an environment where the explosive gas mixture might occur during normal operation;III. Zone 2: an environment where the occurrence of explosive gas mixture is impossible or only for a short time, if any, during normal operation.Note: Normal operation refers to normal startup, operation and shut down, handling of inflammable substance products, opening and closing of the covers of airtight vessels, and the status of safety valves, drainage valves and all other plant equipment operating in the ranges of their respective design parameters.

Article 4.2.6 Those conforming to one of the following conditions may be classed under the non explosion hazard zone:I. A zone where no releasing source exists and no intrusion of inflammable substances is possible; II. Where the highest possible concentration of the inflammable substances is not over 10% of the lower limit of explosion, such as the water cooling tower, etc.;III. In the vicinity of the equipment that uses open fire during the operation or in the 1.5m range around the equipment that has the surface temperature of its hot parts exceeding the ignition temperature of the inflammable substances within the zone;

Article 4.2.7 The ventilation in an explosion hazard zone can be accepted as good ventilation when the airflow can quickly dilute the inflammable substances to under 25% of the lower explosion limit.In case mechanical ventilation is adopted, the following requirements shall be met:I. Enclosed or semi-enclosed buildings shall be provided with independent ventilation systems;II. Precautions against releasing of inflammable substances, such as automatic stopping of the process flow and so on, or the precaution of cutting off the electrical equipment shall be taken to cope with failure of the ventilation equipment.

Article 4.2.8 Division of the explosion hazard zones shall be based on the releasing source classes and the ventilation conditions and in accordance with the following rules:I. The zones shall be divided according to the following classes of releasing source:1. A zone with continuous class releasing source may be classed under zone 0;2. A zone with class 1 releasing source may be classed under zone 1;3. A zone with class 2 releasing source may be classed under zone 2.II. Zoning shall be adjusted according to the ventilation conditions:1. In case of natural ventilation and common mechanical ventilation, the explosion hazard zone shall be degraded when the ventilation is good and upgraded when the ventilation is poor;2. In case local mechanical ventilation is more effective than natural or common mechanical ventilation in reducing the concentration of the explosive gas mixture, local mechanical ventilation may be used to degrade the explosion hazard zone;3. The explosion hazard zone shall be upgraded locally at barriers, pits and corner pockets;

4. The range of the explosion hazard zone can be reduced by limiting, with such barriers as dams or walls, the diffusion of the explosion gas mixture that is heavier than the air.

Article 4.2.9 Ventilation may be divided into the following types:I. Natural ventilation1. In outdoor unit areas, including outdoor pump stations and pipe racks, etc.;2. Open or semi-open type buildings and structures. Proper openings or windows shall be arranged on the roof when the relative density of the hazardous gas is less than and equal to 0.75 and the building shall be open at the bottom when the same density is more than 0.75, both of the cases being natural ventilation environments.II. Common mechanical ventilationWith mechanical ventilation equipment provided at proper locations, the air circulation of the zone can be improved and the hazardous grade of the environment can be lowered.III. Local mechanical ventilation1. The air extraction system on process equipment and storage vessels that release inflammable gas or vapor continuously or periodically;2. The exhaust system in local areas where the ventilation is not good;3. Such locations as the air exhaust tank in the laboratory.IV. No-ventilation area or barrier areaWhen the releasing source is in an environment without ventilation, the hazard zone might be upgraded. The local grade shall be raised and the range of the hazard zone shall be enlarged at pits and corner pockets. Such barriers as dams or walls can prevent the explosive gas from diffusion and reduce the range of the hazard zone.In case there are pits, corner pockets and barriers, the density of the gas or vapor shall be considered in determining the grade and range of the hazard zone. In a zone where the relative density of gas or vapor is less than or equal to 0.75, the lower place is less hazardous as the explosive mixture does not tend to accumulate there, but the higher place shall be paid attention to; while in a zone where the relative density of gas or vapor is greater than 0.75, the higher place is less hazardous as the explosive mixture does not tend to accumulate there, but the lower place, especially the depressed locations with poor air circulation, shall be paid attention to.

Section III Ranges of Gas or Vapor Explosion Hazard Zones

Article 4.3.1 The following factors shall be taken into account for determining the range of an explosive gas hazard zone:I. Explosive gas heavier than air1. The vapor of liquefied petroleum gas with 1.5 ~ 2 relative density released above or near the ground can spread very far along the surface of the ground, if the air flow is not strong enough to diffuse it, and its hazardous range shall be considered cautiously.2. A liquid with its flashing point lower than 28C tends to have its vapor volatilized naturally into the atmosphere and, especially under a high temperature, can give off large volume of vapor which is diffused quite far.3. A liquid with its flashing point between 28C and 45C (including kerosene oil and multiple types of solvents) can give off large volume of vapor when heated, increasing the hazard of the adjacent releasing

location, but its diffusion range will not extend very far as it will condense when cooled down by the air. 4. If the inflammable liquid’s flashing point is lower than its own maximum temperature, the explosive gas mixture and hence the explosion hazard zone will exist.5. Please refer to Fig. 4.3.1-1 ~ 4.3.1-3, Fig. 4.3.1-7 and Fig. 4.3.1-8 for the hazard zone range for the explosive gas heavier than air.II. Explosive gas lighter than air1. These gases include hydrogen gas, methane and hydrocarbon with low molecular weight, in which the hydrogen gas shall be paid special attention to as it is characterized by greater explosion range, higher flame propagation speed, lower density, lower ignition energy and higher fire temperature. 2. The hazardous range of these gases is smaller under good ventilation conditions. Natural or mechanical ventilation measures adopted in the upper space on the top of the buildings and structures will be effective.3. Please refer to Fig. 4.3.1-4 and 4.3.1-6 for the hazard zone range for the explosive gas lighter than air.

Article 4.3.2 In an explosion hazard zone, a local part can be turned into a non explosion hazard zone if the barotropic or continuous delusion measure is taken. But the following requirements shall be met:I. The air source to be induced into the plenum room shall be safe and reliable, without any inflammable substances, corrosive medium or mechanical foreign matters. For gas and vapor heavier than the air, the air inlet shall be set over 1.5m above the space range of the explosion hazard zone;II. The forced draught system used for the plenum shall have a backup fan. The pressure in the plenum shall be maintained at 20Pa ~ 60Pa (2mm ~ 6mm water column) and an alarm shall be given when it falls below this value;III. The building shall be provided with enclosed non-combustible solid walls, non-opening fire-resistant sealed windows and automatically airtight fire-resistant sealed doors;IV. The inflammable gas concentration detector shall be provided, which shall give an alarm when the concentration reaches 50% of the lower explosion limit of the explosive hazard mixture;V. All the openings and trenches leading to the outside of the room shall be isolated and sealed with non-combustible materials.

Article 4.3.3 For a production unit as a class 2 releasing source with the process equipment’s volume no greater than 95m3, the pressure no more than 3.5 MPa and the flow no greater than 38L/s, the ranges of its explosion hazard zones shall be determined according to the following rules (Fig. 4.3.1-1 ~ 9) based on the practical experiences:I. The pits and trenches below the ground in the explosion hazard zone shall be classed under zone 1;II. The range centered at the releasing source, with a radius of 4.5m or to above the ground shall be classed under zone 2.

[图见原文 1160014 ~ 1160017页。]

① Class 2 releasing source ② ground ③ pits & trenches, etc., below the ground ④ zone 1 ⑤ zone2 ⑥ Additional zone 2

(It is recommended to consider this only where releasing of large volume of inflammable substances is possible.) ⑦ Not zoned

Fig. 4.3.1-1 Operation area with explosive gas heavier than air and good ventilation(releasing source near the ground)

① Class 2 releasing source ② ground ③ pits & trenches, etc., below the ground ④ zone 1 ⑤ zone2 ⑥ Additional zone 2

(It is recommended to consider this only wherereleasing of large volume of inflammable substances is possible.) ⑦ Not zoned

Fig. 4.3.1-2 Operation area with explosive gas heavier than air and good ventilation(releasing source above the ground)

① Releasing source in closed object ①-2 Poor ventilation zone ② ground ③ pits & trenches, etc., below the ground ④ zone 1 ⑤ zone2

⑥ Additional zone 2 (It is recommended to consider this only wherereleasing of large volume of inflammable substances is possible.) ⑦ Not zoned

Fig. 4.3.1-3 Operation area with explosive gas heavier than air and poor ventilationNote: Either 15m from the releasing source or 3m outward from the exterior wall, whichever is greater.

① Releasing source ② ground ③ Bottom of closed zone ④ Max. 4.5m or to the ground ⑤ zone2 ⑥ Not zoned

Fig. 4.3.1-4 Compressor building with explosive gas lighter than air and good ventilation

① Releasing source ② ground ③ Bottom of closed zone ④ Max. 4.5m or to the ground ⑤ Zone 1 ⑥ Zone 2 ⑦ Not

zoned ⑧ Not zoned

Fig. 4.3.1-5 Compressor building with explosive gas lighter than air and poor ventilation

① Releasing source ② ground ③ Max. 4.5m or to the ground ④ Zone 2 ⑤ Not zoned

Fig. 4.3.1-6 Operation area with explosive gas lighter than air and good ventilation

① Storage tank inside dam ② Storage tank without dam ③ Dam ④ pits & trenches, etc., below the ground ⑤ Ground ⑥ Zone 1 ⑦ Zone 2 ⑧ Zone 0 ⑨ Not zoned ⑩ Liquid level 11. 1.5m radius range 12. Zone 0 13. Vent

Fig. 4.3.1-7 Outdoor storage tank above the ground (fixed) with explosive gas heavier than air

① Storage tank inside dam ② Storage tank without dam ③ Dam ④ pits & trenches, etc., below the ground ⑤ Ground ⑥ Zone 1 ⑦ Zone 2 ⑧ Not zoned

Fig. 4.3.1-8 Outdoor storage tank above the ground (floating roof) with explosive gas heavier than air

① Class 2 releasing source ② ground ③ pits & trenches, etc., below the ground ④ Zone 1 ⑤ Zone 2

Fig. 4.3.1-9 Inflammable liquid, inflammable liquefied gas, inflammable compressed gas and low temperature liquid releasing sources above outdoor ground

Section IV Electrical units in gas or vapor explosion hazard environment

Article 4.4.1 Selection of explosion-proof electrical equipment shall be adapted to zoning of the explosion hazard environment.

The class and group of the selected explosion-proof electrical equipment shall not be lower than those of the explosive medium in the environment. When there exist two or more media which occupy certain proportions, the electrical equipment shall be selected according to the class and group of the most hazardous medium. The selected electrical equipment shall be marked with explosion-proof symbols.

Article 4.4.2 Please refer to Table 4.4.2 for selection of the explosion-proof structure of the electrical equipment.

I. Classification of explosion-proof electrical equipment

Class I: electrical equipment used down the pits of coal mines

Class II: electrical equipment used in factories

II. Explosion-proof symbols of electrical equipment

1. The explosive gases are divided into 3 classes of IIA, IIB and IIC according to the greatest test safety gap and into 6 groups of T1 to T6 according to the ignition temperature (refer to Addendum 2 for details).

The symbols in the table mean: 0 ---- applicable; △ — to be avoided as much as possible; * --- not applicable; no symbol---not possible in structure or normally avoided.

Note: ① means the part producing sparks is a flame-proof or barotropic structure and the main body is a enhanced safety type explosion-proof structure.

2. Various types of explosion-proof structures are as follows:

Flame-proof type d

Enhanced safety type e

Intrinsic safety type ia, ib

Barotropic type p

Oil filled type o

Sand filled type q

Sparkles type n

Special type s

Enclosed type m

Table 4.4.2 Selection of the explosion-proof structures of electrical equipment

No. Explosion hazard zone

Explosion-proof structure

Electrical equipment

Zone 0 Zone 1 Zone 2

Intrinsic

safety

Flame-

proof

Baro-

tropic

Oil

filled

Enhanced

safety

Intrinsic

safety

Intrinsic

safety

Flame-

proof

Baro-

tropic

Oil

filled

Enhance

d safety

Spark-

less

1 Motor

Squirrel cage induction motor 0 0 △ 0 0 0 0Wound rotor induction motor △ △ 0 0 0 ① *Synchronous motor 0 0 * 0 0 0 ①DC motor △ △ 0 0Electromagnetic slip clutch (brushless) 0 △ * 0 0 0 △

2LV

transformer

Transformer (including startup) △ △ * 0 0 0 0Reactance coil (including startup) △ △ * 0 0 0 0Transformer used for instrument △ * 0 0 0

3 Electrical device

Control switch and button 0 0 0 0 0 0Operating box (pole) 0 0 0 0Circuit breaker, blade 0 0Fuse 0Electromagnet used for solenoid valve 0 0Control panel, distribution panel 0 0

4Lighting fixture

Fixed lighting fixture 0 * 0Movable lighting fixture △ 0Portable battery light 0 0Indicator light 0 * 0Ballast 0 △ 0

5 Miscellaneous

Signal alarm device 0 0 * 0 0 0Socket 0 0Terminal box 0 △ 0Electrical measurement meter 0 0 * 0 0

3. The explosion-proof symbol of the electrical equipment shall be composed of such 3 parts as the type of explosion-proof structure and the class and group of the explosive gas.

1) Other explosion-proof electrical equipment than the flame-proof intrinsic safe ones shall not be marked with IIA, IIB or IIC

2) In case of combination of more than one types, the explosion-proof type of the main body shall be marked first and the other explosion-types next. For example, class II enhanced safety type main body with group T4 barotropic part: ep II T4.

3) For an electrical equipment in an environment where only one kind of media is allowed for use, its mark may be represented with the chemical molecular formula or name of the said medium and the class and group may be omitted. For example, class II flame-proof for ammonia environment (button): d II (NH) or d II ammonia.

4) For class II electrical equipment, the temperature group or the maximum surface temperature or both may be marked. For example, enhanced safety type used in factory with 125C maximum surface temperature: e II T5 or e II (125C) or e II (125C) T5.

Article 4.4.4 General rules for electrical lines in an explosion hazard environment are as follows:

I. The electrical lines shall be laid in a less hazardous environment or at a location far from the releasing resource:

1. When the gas and vapor are heavier than air, the electrical lines shall be laid at higher places or directly embedded; cable trays shall be used for overhead arrangement; and the cable trenches shall be filled with sand and provided with effective drainage;

2. When the gas and vapor are lighter than air, the electrical lines shall be laid at lower places or in cable trenches.

II. The electrical lines should be laid outside the wall of explosion hazardous buildings and structures;

III. The holes and openings on walls or floors between different zones where the trenches, cable or tubing for laying electrical lines pass through shall be tightly blocked with noncombustible materials;

IV. Places where the electrical lines are subject to mechanical damage, vibration, corrosion or heating should be avoided for laying of the lines and, if it is not possible to avoid them, corresponding precautions shall be taken;

V. The rated voltage of the cables or conductors used for LV power and lighting lines shall be less than the operating voltage and no less than 500V; the operating neutral line shall have the rated voltage of its insulation equal to that of the phase line and shall be laid together with the phase line in the same bushig or conduit;

VI. Both the phase line and neutral line in the single phase network of Zone 1 shall be provided with short circuit protection and also with a double-pole switch for cutting off the phase and neutral lines simultaneously.

Article 4.4.5 Copper core cable shall be used in Zone 1 and the same should be used in Zone 2. In case an aluminum core cable is used, the connection between the cable and the equipment shall be made with an reliable copper-aluminum transit connector.

Article 4.4.6 The 6 ~ 10KV cable lines should be provided with residual current protections, which shall act upon a trip in Zone 1 and at a signal in Zone 2.

Article 4.4.7 Except for the circuits in an intrinsic safety system, the technical requirements for cable and conduit lines in Zone 1 and Zone 2 shall meet the specifications in Table 4.4.7-1 and 4.4.7-2.

Technical requirements for cable lines in explosion hazard environment Table 4.4.7-1

Item Technical

requirements

Explosion hazard zone

Min. sections of open cables or cables in trenches

Terminal boxMovable

cablePower Lighting Control

Zone 1Copper core of 2.5mm2 & above

Copper core of 2.5mm2 & above

Copper core of 2.5mm2 & above

Flame-proof Heavy

Zone 2

Copper core of

1.5mm2 & above or

aluminum core of

4mm2 & above

Copper core of

1.5mm2 & above or

aluminum core of

2.5mm2 & above

Copper core of

1.5mm2 & aboveFlame-proof

Enhanced safety

medium

Technical requirements for conduit lines in explosion hazard environment Table 4.4.7-2

Item Technical

requirements

Explosion hazard zone

Min. sections of open cables or cables in trenches Terminal box

Branch box

Flexible box

Conduit connection

requirementsPower Lighting Control

Zone 1Copper core of 2.5mm2 & above

Copper core of 2.5mm2 & above

Copper core of 2.5mm2 & above

Flame-proof

No less than 5

turns for conduit

thread connection

up to Dg 25mm

& no less than 6

turns for others

Zone 2

Copper core of

1.5mm2 & above or

aluminum core of

4mm2 & above

Copper core of

1.5mm2 & above or

aluminum core of

2.5mm2 & above

Copper core of

1.5mm2 & aboveFlame-proof

Enhanced safety

Ditto

Unarmored cable may be used when the plastic bushing cables are to be laid on cable bridges or cable trays. The connection between aluminum core insulated conductors or cables shall be made by crimping, welding or soldering.

Galvanized steel tubes used for delivery of low pressure fluid shall be adopted. The threaded part of the conduit connection shall be applied with lead oil or phosphorized grease. Sealed connections with drainage of condensate shall be provided on the pipeline where water might be condensed. Flexible connection pipes should be used at connections with the electrical equipment.

Article 4.4.8 The sections of cables and insulated conductors in zone 1 and zone 2 shall be selected in accordance with the following requirements:

I. The allowable current-carrying capacity of the conductor shall be no less than 1.25 times the rated current of the fuse or 1.25 times the set current of the automatic switch long delay over current tripper (except for the case described in 4.4.8II);

II. The long term allowable current-carrying capacity of the line leading to a squirrel induction motor with voltage under 1000V shall be no less than 1.25 times the rated current of the motor.

Article 4.4.9 The electrical lines run in explosion-proof steel conduits in zone 1 and 2 shall be well sealed and shall meet the following requirements:

I. It is necessary to provide isolating seals at the following locations in zone 1 and 2:

1. Between the conductor and the connecting part of the electrical equipment (in case of no isolating seal in the connecting part of the electrical equipment);

2. Within 450mm from the terminal box on steel conduits over 50mm in size and in 15m spaces on steel conduits over 50mm;

3. Between adjacent zone 1 and 2; between zone 1 / 2 and other adjacent hazardous environments or normal environments;

4. Fibers shall be used in the seal as the bottom or interlayer of the packed layer; the effective thickness of the packed layer must be greater than the inner diameter of the conduit in order to prevent the sealing mixture from flowing out.

II. The connecting part used for isolating seal shall not be used as the connection or branch of the conductor.

Article 4.4.10 The following requirements shall be met for grounding:

I. It is stipulated in the technical specification for electrical equipment grounding design that the following parts for which grounding is not necessary shall still be grounded:

1. On ground where the conductivity is poor, the normally dead metal enclosure of electrical equipment with AC rated voltage up to 660V and DC rated voltage up to 440V ;

2. In a dry environment, the normally dead metal enclosure of electrical equipment with AC rated voltage up to 127V and DC rated voltage up to 110V ;

3. Electrical equipment installed on metal structures already grounded.

II. Special grounding lines shall be used for all electrical equipment in zone 1 and all other electrical equipment than the lighting fixtures in zone 2. The grounding line (PE line) should be an insulated wire and shall be laid where easy checks can be made;

III. Metal tubing with reliable electrical connections may be utilized as the grounding for the lighting fixtures in zone 2, but no piping for delivering explosion hazardous materials is allowed to be used for the same purpose;

IV. The main grounding line shall be connected in different directions and in no less than two places in the explosion hazard zone with the grounding conductor;

V. The grounding device of the electrical equipment shall be separated from the grounding device of the independent lightning-rod for protection against direct thunder stroke; shall be combined with the grounding device of the lightning arrester on building for protection against direct thunder stroke; and may also be combined with the grounding device for lightning induction protection and static electricity protection. The grounding resistance shall take the lowest value.

Section V Dust explosion hazard environment

Article 4.5.1 The following substances, when able to form an explosive mixture with air, may be classed under dust explosion hazardous substance:

I. Explosive dust, such as magnesium, aluminum and aluminum bronze dust, etc.;

II. Flammable conductive dust, such as graphite, carbon black, coke, coal, iron, zinc and titanium dust, etc.;

III. Flammable nonconductive dust and fiber, such as polyethylene, phenol and sulfur dust and cotton, linen, silk and wool fiber dust, etc.

Article 4.5.2 Precautions against dust explosion are as follows:

I. Corresponding precautions shall be taken against explosion hazard in accordance with the different characteristics of the explosive dust or flammable dust. The lower explosion limit of the explosive dust or flammable dust varies with the dispersity and humidity of the dust, its content of volatile substances and ash, and the nature and temperature of the fire source;

II. The explosive dust and flammable dust and fiber easy to suspend in the air are more hazardous, for which the following precautions shall be taken:

1. The hazardous substances should be enclosed in vessels to prevent leakage;

2. When the substance can not be processed in an enclosed status, its humidity shall be increased to prevent the dust from flying and reduce the volume of suspended dust in the air;

3. The precipitated dust shall be removed regularly to prevent it from becoming suspending and leading to a secondary explosion;

4. Occurrence of ignition energy and high temperature shall be restricted.

III. Outdoor or open type arrangement should be adopted; in case of an indoor arrangement, mechanical dust removal and mechanical ventilation measures shall be taken and shall be accompanied by corresponding power failure interlock;

IV. The range of the explosion hazard zone shall be limited and reduced and the equipment tending to have leakage of explosive and flammable dusts shall be concentrated in a separate area;

V. An explosion hazard zone shall have at least two accesses, which shall lead to the non explosion hazard zone, and shall have its doors opened to the less hazardous side;

VI. The automation level shall be enhanced and necessary emergency interlocks shall be adopted to prevent mal-operation.

Article 4.5.3 Based on the frequency and duration of the occurrence of explosive or flammable dust environment, the dust explosion hazard zones are classified as follows:

Zone 10: a zone where the explosive dust mixture environment occurs continuously or for long periods;

Zone 11: a zone where the explosive dust mixture environment occasionally occurs due to raising of the accumulated dust from time to time.

Article 4.5.4 A zone meeting one of the following conditions may be classed under the non explosion hazard zone:

I. Where a precipitator with good dust removal effect is provided and, in case of a shutdown of the said precipitator, the process unit can be stopped by interlock;

II. A forced draft (FD) fan room serving the explosion hazard zone and partitioned with wall, without any possible intrusion of flammable dust or fiber (if provided with an one-way air duct and fire retarding safety devices);

III. Where the amount of explosion hazard substances used is not so big and the operation is carried out in an exhaust cabinet or under an exhaust hood.

Article 4.5.5 The exhaust fan room that serves the explosion hazard zone shall be under the same hazard class as the exhausted zone.

Article 4.5.6 When the range of an explosion hazard zone is determined, the volume, releasing rate, concentration and physical features of the explosive or flammable dust and the practical experiences of similar enterprises in similar industrial buildings shall be taken into consideration.

Article 4.5.7 The ranges of explosion hazard zones inside buildings shall be divided in the unit of room.

Article 4.5.8 The electrical units in dust explosion hazard environments shall meet the following stipulations:

I. The electrical equipment and lines, especially the electrical equipment that produce sparks during normal operation, shall be arranged far from the releasing source and it is not recommended to use portable electrical equipment;

II. The max. allowable surface temperature of the electrical equipment shall meet the requirements in Table 4.5.8;

Max. allowable surface temperature of electrical equipment Table 4.5.8

Ignition temperature group Equipment without overload Equipment with overload

T11 215C 195C

T12 160C 145C

T13 120C 110C

III. The selection and arrangement of the electrical equipment and lines shall meet not only the dust explosion proof requirements but also the corrosion proof, weather proof and mechanical strain proof environmental conditions, etc.;

IV. The operating button for the emergency exhaust fan motor shall be mounted where it can be easily operated

in case of an emergency;

V. Less sockets and local lighting fixtures shall be installed in a dust explosion hazard environment; the sockets should be arranged where the explosive and flammable dust do not tend to accumulate and the local lighting fixtures should be arranged where they will not be subject to the impact of air flow during an emergency;

VI. Any electrical equipment that might have overload in a dust explosion hazard environment shall be provided with a reliable overload protection;

VII. Selection of the explosion–proof electrical equipment: except that dust explosion-proof electrical equipment with dust-proof structure (marked with DP) shall be used for a zone 11 environment with flammable nonconductive dust and flammable fiber, dust explosion-proof electrical equipment with dust-tight structure (marked with DT) shall be used for the environments in both zone 10 and zone 11.

Article 4.5.9 The electrical lines shall meet the following requirements:

I. Copper core cables shall be used for the HV line in zone 10, while aluminum core cables may be used for the HV line in zone 11 except for the cases of severe vibration on the power consumption equipment and line;

Copper core insulated conductors or cables shall be used for all the lines in zone 10 and for the lines under 1000V for the power consumption equipment with severe vibration in zone 11;

II. In zone 10, both the phase and neutral lines in the double line single phase network shall be provided with short circuit protection and also with a double-pole switch for cutting off the phase and neutral lines simultaneously.

III. The cable lines in zone 10 and zone 11 shall have no intermediate connections;

IV. The 6 ~ 10KV cable lines shall be provided with residual current protections, which shall act upon a trip in zone 10 and at a signal in zone 11.

V. The cable and conduit lines under 1000V shall meet the requirements in Table 4.5.9;

VI. For running of insulated conductors in zone 10, it is necessary to make isolation sealing between the conductor and the connection part of the electrical equipment and between the same zone and other adjacent areas. The connection part used for isolation sealing shall not be used as connection with or branch of the conductor.

Article 4.5.10 The grounding requirements of the dust explosion hazard environment are the same as those under Article 4.4.10.

Technical requirements for cable and conduit lines in dust explosion hazard environment Table 4.5.9

ItemTechnical

requirements

Explosion hazard zone

Min. sectional area of wire

(mm)

Terminal box, branch box

Conduit connection requirements

Movable cable

Zone 12.5mm2& above Copper core

Dust tight5 turns & above of engagement

Heavy

Zone 2

1.5mm2 & above Copper core or 2.5mm2 & above aluminum core

Dust tight

Dust-proof type is also allowed.

5 turns & above of engagement

medium

Note: 1) Galvanized steel tubes for delivering low pressure fluid shall be used;2) The threaded part of the conduit connection shall be applied with lead oil or phosphorized grease.; 3) Sealed connections with drainage of condensate shall be provided where water might be condensed.

Section VI Fire hazard environment

Article 4.6.1 The following materials may be classed under fire hazardous substance:I. The flammable liquid with its flashing point higher than the ambient temperature; the flammable liquid that might be leaked but can not form an explosive mixture in case of higher operating temperature of the material than the flashing point of the flammable liquid (such as the diesel oil, lube oil and transformer oil, etc.);II. Flammable dust or fiber in suspended or stacked state which can not form an explosive dust mixture, such as aluminum powder, coke powder, coal powder, synthetic resin powder and so on;III. Solid state flammable substance, such as coal, timber and so on.

Article 4.6.2 Zoning of the fire hazard environmentThe fire hazard environment are divided into zone 21, zone 22 and zone 23, in which respective flammable substances described in Article 4.6.1 I, II and III exist and are in enough quantity and configuration to cause a fire hazard.

Article 4.6.3 The electrical equipment in the fire hazard zone shall meet the following requirements:I. Electrical equipment with sparks and high surface temperature of enclosure during normal operation shall be arranged for from the flammable substances;II. Distribution substations up to 10KV should not be arranged over or under fire hazard zones and, if they are adjacent to any fire hazard zone, they shall meet the following requirements:1. A distribution substation may be connected with the fire hazard zone through a corridor or an inner room, the door of which shall be flame retardant and, except in zone 23, shall be provided with an automatic closing device; Distribution substations under 1000V may be connected with the fire hazard zone through a fire retardant door;2. The partition wall and floor slab commonly used by a distribution substation and a fire hazard zone shall be made of dense nonflammable material; the openings where piping and trenches pass through walls or floors shall be tightly blocked with noncombustible materials;3. The door of a transformer room and the window of a distribution room shall lead to a non fire hazard zone.III. In case the gabarit of an outdoor transformer or power distribution unit is within 10m from the exterior wall of the fire hazard zone building, the following requirements shall be met:1. The wall on the side of the transformer or distribution unit shall be a nonflammable body;2. In the range of the transformer’s or distribution unit’s height plus 3m and 3m from both sides of the

gabarit, there shall be no door, window or opening on the wall;3. Above the horizontal line of the transformer’s or distribution unit’s height plus 3m (with the width of 3m from both sides of the gabarit of the transformer or distribution unit), fixed window with metal wire glasses made of noncombustible material may be installed on the wall.IV. In a fire hazard environment, proper types of electrical equipment shall be selected for use according to Table 4.6.3 and based on the class of the zone and application conditions.

Table 4.6.3 Selection of protection structures of electrical equipment

No. Fire hazard zone

Protection structure

Electrical equipment

Zone 21 Zone 22 Zone 23

1 motorFixed installation IP44①

IP54IP21②

Movable and portable IP54 IP54

2Electrical devices & instrument

Fixed installation Oil filled IP54, IP44③

IP54IP44

Movable and portable IP54 IP44

3Lighting fixtures

Fixed installation IP2X

IP5XMovable and portable

IP54 IP2X4 Power distribution unit

5 Terminal box

Note: ① In zone 21, it is not recommended to use motors with IP44 structure for components that have sparks during normal operation ② In zone 23, IP44 structure instead of IP21 structure shall be adopted for motors of components that have sparks during normal operation.③ In zone 21, it is not recommended to adopt IP44 structure for electrical devices and instruments that have sparks during normal operation.

Chapter V Distribution Substation

Section I Location

Article 5.1.1 The location of a distribution substation shall be selected on the basis of comprehensive consideration of the following requirements:

I. Near the load center;

II. Close to the power line;

III. Convenient for outgoing line and suitable for future development;

IV. The following places or pollution sources shall be avoided:

1. Places with high temperature, severe vibration and accumulated water;

2. The pollution sources or emission points of dust, vapor, mist or corrosive gases, etc.

Article 5.1.2 The distribution substation shall not be located in an explosion hazard zone.

In case the distribution substation is partially located in an explosion hazard zone, the part in the explosion hazard zone shall meet the following requirements:

1. It shall be provided with air-tight noncombustible solid walls, without any door;

2. When windows are necessary, air-tight windows made of fire-retardant materials and not able to be opened shall be adopted.

Section II Power Supply & Distribution System

Article 5.2.1 The voltage of the generator for a production unit shall be at the same level as the distribution voltage of the same unit.

Article 5.2.2 AC 400V/230V three phase four wire system shall be adopted for the voltage of the emergency generator.

Article 5.2.3 For large size motors, large size electrical furnaces and other large-capacity loads, the instantaneous voltage fluctuation caused by their cutting into the power distribution network shall be checked. When the voltage fluctuation on the distribution bus go beyond the allowable range, the following measures shall be taken:

I. Separate the power supply circuits with a reasonable power supply method;

II. Limit the starting current by step-down startup, etc.;

III. Reduce the simultaneous self-start capacity;

IV. Use motors with smaller starting current;

V. Reduce the line impedance;

VI. Increase the short circuit capacity of the power supply system;

VII. Use dynamic reactive power compensator;

VIII. Provide the generator with a fast automatic excitation regulator.

Article 5.2.4 6 ~ 10KV power network voltage distortion limit (phase voltage) shall not exceed the value specified in the Provisional Specification for Power System Harmonic Management (SD126-84). When the specified value is exceeded, measures shall be taken to restrain the high harmonic wave.

Article 5.2.5 For 6 ~ 10KV power distribution for the distribution substation of the production unit, a radioactive system and no more than 2 power distribution steps should be adopted.

Article 5.2.6 For 6 ~ 10KV buses, single bus or single bus sectionalized connection should be adopted. The process flow and other conditions shall be taken into consideration for sectionalization of the bus and the power consumers in the same production section should be connected to the same section of bus.

Article 5.2.7 6 ~ 10KV distribution outgoing feeders should be controlled with circuit breakers, but the electric furnace transformer and motor circuits without big capacity may be controlled with fuses ---- vacuum contactors.

Article 5.2.8 For fixed switch cabinets with possible power feedback on the 6 ~ 10KV outgoing circuits, disconnectors shall be added to the line side of the circuit breakers.

Article 5.2.9 Where the single phase grounding capacity current in a 6 ~ 10KV network is over 30A, compensation measures shall be taken.

Article 5.2.10 380V/220V three phase four wire or three phase five wire system should be adopted for LV distribution voltage.

Article 5.2.11 Single bus or single bus sectionalized connection should be adopted on the LV side of the substation. The LV distribution system shall be adapted to the process flow and all the power consumers in the same production section should be supplied by the same bus. The LV auxiliary power supply for an HV power consumer shall be in the same system as the HV power supply.

Article 5.2.12 The quantity and capacity of transformers shall be determined according to the nature and size of the loads and the cost effectiveness of power supply. When motor restart is considered, the said quantity and capacity shall also be checked against the restart capacity.

Article 5.2.13 When the production unit is provided with a special lighting transformer, the maintenance load may share a common transformer with it.

Article 5.2.14 Single phase power consumers should be distributed equally among the three phases. The neutral line current caused by unbalanced single phase loads must not exceed the valued specified for the transformer selected for use.

Article 5.2.15 When the power factor on the 6 ~ 10KV side of the unit’s substation is lower than 0.9, it is recommended to provide an reactive power compensator.

Article 5.2.16 The reactive power compensation measures are described as follows:

I. Use a synchronous motor;

I. Use a parallel capacitor group;

III. Utilize the generator of the unit.

Article 5.2.17 When the parallel capacitor is used for compensation, local compensation near the place with greater reactive load is recommended. On the basis of technical and economic comparison, centralized compensation combined with distributed local compensation may also be adopted.

Section III Operation Power Supply

Article 5.3.1 For 6 ~ 10KV distribution substation, silicon rectified nickel-cadmium battery should be used as the operation power supply and AC power operation power supply may also be used.

Article 5.3.2 AC operation power supply is normally used for an LV distribution substation. Silicon rectified nickel-cadmium battery may also be used as the operation power supply, according to the requirements of the automatic unit and relay protection.

Section IV Selection of 6 ~ 10KV Major Electrical devices

Article 5.4.1 The following principles shall be observed in selection of major electrical devices:

I. The maximum allowable operating voltage of the electrical device shall not be lower than the maximum operating voltage of the circuit it is connected to;

II. The rated current of the electrical device shall not be lower than the continuous operating current of the circuit it is connected to under all possible operating modes;

III. The short circuit current used for checking the electrical device’s dynamic / hot stability and breaking current shall be calculated according to the designed capacity of the power system and considering the development prospect of 5 ~ 10 years;

IV. The short circuit current used for checking the electrical devices shall be calculated as follows:

1. The attenuation time constant of short circuit and the short circuit of LV network shall be calculated, but the resistance of all the elements shall be omitted in calculation;

2. The feedback current of a motor with feedback function shall be calculated.

V. On a circuit without any reactor, the point with the biggest short circuit current under normal operation wiring conditions shall be selected as the short circuit calculation point;

On a circuit with reactors, except that a point before the reactor shall be selected as the short circuit calculation point for the lead and bush before the spacer between the bus and the disconnector, a point after the reactor should be selected for all the other conductors and electrical devices;

VI. Calculation of the dynamic/hot stability and breaking current of electrical devices may be checked with three phase short circuit current and, in case a self-supply generator is provided and the two phase short circuit current at its outlet is greater than the three phase short circuit current, may also be checked with two phase short circuit current;

VII. The conductors and electrical devices with fuse protection may be omitted from checking of the hot

stability, and the dynamic stability of naked conductors and electrical devices shall still be checked except for those protected by fuses with current limiting function;

Checking of the dynamic and hot stability may be omitted for potential transformer (PT) circuit with fuse protection;

VIII. When the electrical devices are selected, the above mentioned shall be checked according to the local atmospheric temperature, humidity, altitude and seismic conditions.

Article 5.4.2 The following principles shall be observed in selection of HV circuit breakers:

I. When the current breaking capability of the circuit breaker is checked, the breaking current shall be used instead of the breaking capacity. The actual breaking time (the sum of relay protection acting time and circuit breaker opening time) and the short circuit current should be used as the checking conditions;

II. For a circuit breaker with an automatic recloser, the influence of reclosing on the rated breaking current shall be taken into consideration;

III. The closing current of the circuit breaker shall be no less than the maximum impulse value of the short circuit current;

IV. For a circuit breaker used for cutting in the parallel compensation capacitor group, the multiple of the operating over-voltage shall be checked and corresponding measures shall be taken to restrain the over-voltage; the rated current of the circuit breaker shall be no less than 1.35 times that of the capacitor group;

V. It is recommended to adopt vacuum circuit breakers and for circuits that are operated frequently, vacuum circuit breakers shall be adopted.

Article 5.4.3 Power capacitor

I. The stable over-voltage on the capacitor shall not exceed 1.1 times its rated voltage.

II. To select the capacity of a single set of single phase capacitor, the capacitor with lager capacity should be selected, on condition that the capacity is equally distributed among three phase and approaches the calculated total compensation capacity.

III. For capacitors with single set capacity of 100kvar and above, those with internal discharge resistors shall be selected.

Article 5.4.4 The following principles shall be observed in selection of serial reactors:

I. The reactance value of the serial reactor used for limiting the closing surge current shall be selected according to the surge current allowed by the circuit breaker, current transformer (CT) and other equipment;

II. The reactance of the serial reactor used for limiting the high harmonic wave and surge current shall render the circuit’s total impedance to the restrained harmonic inductive, with (5% ~ 6%) Xc to be selected for harmonics that are restrained 5 times or more and (12% ~ 13%) Xc to be selected for those restrained 3 times or more;

III. When the secular max. allowable current of the serial reactor is equal to 1.35 times the rated current of the capacitor, the actual reactance shall not be less than 90% of the rated capacitance.

Article 5.4.5 The following principles shall be observed in selection of current transformers (CT)

I. For a 6 ~ 10KV indoor distribution unit, it is recommended to adopt the CT with resin casted insulation structure;

II. The rated primary current of the CT at the neutral point of a power transformer shall be greater than the unbanlanced current allowed by the transformer;

The dynamic stability multiple shall be checked with the short circuit current that flows through the transformer’s neutral point at a single phase short circuit;

III. The zero sequence CT for a neutral point non-direct grounding system shall be selected and checked according to the following requirements:

1. The starting current of the primary circuit shall be determined according to the secondary current and protection sensitivity;

2. The window diameter of the cable type zero sequence CT shall be selected according to the number and outer diameter of the cables;

3. The bus section of the bus type zero sequence CT shall be selected according to the rated current;

IV. The dimension of the bus allowed to pass through the window shall be checked for the bus type CT;

V. Selection of CT’s shall meet the stipulations under relevant standard for secondary wiring.

Article 5.4.6 The following principles shall be observed in selection of potential transformers (PT)

I. For a 6 ~ 10KV indoor distribution unit, it is recommended to adopt a electromagnetic type PT with resin cast insulation structure;

II. Wiring of the PT should be made simple as long as the secondary voltage and load requirements are met and, when zero sequence voltage is required, 3 sets of single phase three winding PT’s should be used;

III. For the PT in a neutral point non-direct grounding system, harmonic extinguishing measures shall be taken;

IV. The voltage of the third winding shall be 100V for the PT in a neutral point direct grounding system and shall be 100V/3 for the PT in a neutral point non-direct grounding system;

V. An electromagnetic type PT can be used concurrently as the energy discharge equipment for the parallel compensation capacitor group, but there shall be no breaking point between the PT and the capacitor group;

VI. Selection of PT’s shall meet the stipulations of relevant standard for secondary wiring.

Article 5.4.7 The following principles shall be observed in selection of lightning arresters:

I. The continuous operating voltage of the metallic oxide lightning arrester shall not be lower than the secular operating voltage applied on the terminal of the lightning arrester;

II. The arc extinguishing of the valve lightning arrester shall not be lower than the power frequency over-voltage occurring in the system; the rated voltage of the metallic oxide lightning arrester should be selected according to the power frequency over-voltage occurring in the system, taking into account its duration and initial energy;

In the neutral point non-direct grounding system, the arc extinguishing voltage or rated voltage shall be no lower than the maximum operating line voltage;

III. For a common valve lightning arrester providing only protection against atmospheric over-voltage, the lower peak limit of its power frequency discharge voltage shall be higher than the expected operating over-voltage level at its installation location;

IV. The impulse discharge voltage and residual voltage of the lightning arrester, added with a proper margin, shall be lower than the reference impulse insulation level of the distribution equipment; it is recommended to take the residual voltage under the following impulse currents as the basis for insulation matching;

1. Lightning arrestor for protection of rotating machines: 3KA;

2. 6 ~10KV valve lightning arrester: 5KA;

V. For a valve lightning arrester providing protection against operating over-voltage, its rated through current capacity shall be no less than the impulse current that flows through the lightning arrester during system operation; the operating impulse current to occur when the no load line and the parallel capacitor group are cut in shall be so calculated that all the accumulated energy can be discharged through the lightning arrester;

For metallic oxide lightning arresters, the energy absorbed by the lightning arrester at the installation location under the influence of one time of operating over-voltage shall be checked first;

VI. Plateau type lightning arresters shall be adopted in high altitude regions;

VII. For a lightning arrester providing protection of the rotating motor neutral point insulation, the magnetic blow-out arrester or metallic oxide arrester should be adopted, whose rated voltage shall be no lower than the maximum operating phase voltage of the motor.

Section V Arrangement of Transformers & Distribution Units

Article 5.5.1 The type and architectural arrangement of the distribution substation shall meet the following requirements:

I. Indoor distribution substation is recommended;

II. The distribution substation shall be provided with necessary accessory buildings according to the actual requirements and on the principle of cost saving;

The attended distribution substations shall be provided with separate duty room and maintenance room,, as well as rest rooms and toilets for men and women;

III. The transformer room and reactor and capacitor room should avoid western exposure;

IV. The control room should avoid western exposure and face a good direction;

V. Cable trench wiring is recommended for the distribution unit room. In case of a big quantity of cables, cable room wiring may be adopted, with the clear height under the beam in a cable room to be no lower than 1.8m. The bottom floor cable room may be underground, semi-underground or above-ground type depending on the actual under ground water level;

VI. The ground level of a distribution unit room shall meet the following requirements:

1. In case of a higher underground water level, the bottom of the cable trench should not be lower than the said water level;

2. When not limited by the underground water level, it should be over 300mm higher than the outdoor ground level;

3. When adjacent to an explosion hazard zone, it shall be over 600mm higher than the outdoor ground level.

Article 5.5.2 The arrangement of transformers shall meet the following requirements:

I. The distribution transformer in a substation may be installed indoor, outdoor or semi-outdoor, depending on the specific environmental conditions;

II. The shall be no less than the values listed in Table 5.5.2:

Table 5.5.2 Min. clearance between gabarit of transformer and walls &

door of transformer room (m)

Transformer capacity (kVA)

Description

100 ~ 1000 1250 and above

Clearance between transformer and rear/side walls

0.6 0.8

Clearance between transformer and door 0.8 1.0

III. Outdoor or semi-outdoor transformers shall be surrounded with fixed rails, with the clearance from the gabarit of the transformer to the external wall of the building no less than 0.8m, the bottom of the transformer no less than 0.3m from the ground, the clearance between the gabarit of adjacent transformers no less than 1.5m and the fire protection clearance between adjacent transformers no less than 10m in case of a class 1 load; when it is difficult to meet these requirements, fire protection walls shall be provided;

IV. The core lifting equipment, if any, in a transformer room may be considered according to the weight of the transformer’s core.

Article 5.5.3 The arrangement of the distribution units shall meet following requirements:

I. The HV and LV distribution units may be arranged in different columns in the same room and, in case of less HV switch cabinets, may also be arranged in the same column, but with the clearance between them to be no less than 2m;

II. For HV distribution units, 1 ~ 2 backup cabinets and empty positions of 10% ~20% in backup cabinets shall be reserved for each section of bus and rooms for development should be left;

III. For LV distribution units, backup outgoing circuits of no less than 20% shall be provided for each bus section and there should be no less than one backup circuit for each capacity level of outgoing circuits, with backup positions to be reserved at the same time;

IV. The arrangement dimension of an HV switch cabinet shall not be less than that listed in Table 5.5.3-1;

V. The arrangement dimension of an HV distribution panel shall not be less than that listed in Table 5.5.3-2;

VI. The arrangement dimensions of various panels in the control room shall not be less than those listed in Table 5.5.3-3;

Table 5.5.3-1 Arrangement dimensions of hv switch cabinets (mm)

Type of switch cabinets

Operating walkwayMaintenance

walkway

Arranged against wall

Single column arrangement

Double column arrangement

back side

Fixed type 1800 2300 1000 50 200

Cart type Single cart L+1200 Double cart L+900 1000 -- --

Table 5.5.3-1 Arrangement dimensions of lv distribution panels (mm)

Type of distribution

panels

Operating walkwayMaintenance

walkway

Arranged against wall

Single column arrangement

Double column arrangement

back side

Fixed type 1500 2000 1000 50 200

Drawer type 1600 2000 1000 -- --

Table 5.5.3-1 Arrangement dimensions of various panels (mm)

Opposite sides Panel front Panel back Wall

Panel front

Panel back

Panel sides

1800

--

--

1500

1000

--

1500

1200

1200

VII. The distribution unit and control room should be provided with two accesses, which shall be arranged at the two ends. In case of two floors or more, the access on the upper floor should lead to the platform of the outdoor staircase, which is also used as the equipment lifting platform and whose bearing capacity and dimension shall suffice the weight and dimension of the largest equipment to be handled.When the LV distribution unit is longer than 6m, its maintenance walkway shall be provided with two accesses leading to the same room or the other rooms and, in case the distance between the two accesses exceeds 15m, more access shall be added.When the HV distribution unit room on the ground floor is shorter than 7m and the LV distribution unit room on the ground floor is shorter than 8m, one access may be provided;VIII. Protection measures against closing of magnetic conducting circuit shall be taken for through wall bushes with over 1500A of current and through wall spacers for CT;IX. HV distribution unit room with oil circuit breakers should be provided with an emergency exhaust fan, whose ventilation frequency shall be no less than 6 times per hour.

Article 5.5.4 The arrangement of parallel capacitor units shall meet the following requirements:I. The indoor HV capacitor unit shall be installed in a separate room and the LV capacitor panel with

centralized compensation may be installed in the LV distribution unit room;II. The arrangement of outdoor concentrated capacitors shall meet same requirements as described under 5.5.2 III.

Section VI Relevant Requirements for Buildings

Article 5.6.1 The roof of a substation located in a hot region shall be provided with a thermal insulation layer and shall be properly increased in height. When western exposure can not be avoided for the control room, sun shading measures shall be taken. The roof of a substation in a cold region shall also be provided with a thermal insulation layer.

Article 5.6.2 Terrazzo floors should be adopted for the control room and HV/LV distribution room of a substation.

Article 5.6.3 The internal wall surfaces of a substation shall be treated according to the following requirements:I. The walls and the non-suspended ceiling of the control room should be coated with paint;II. The walls of the distribution unit room, capacitor room and transformer room shall be plastered and whitened and their ceilings shall be whitened but not plastered.

Article 5.6.4 The doors and windows of a substation shall be arranged according to the following requirements:

I. The doors of the control room, distribution unit room, capacitor room and transformer room shall all be opened to the outside and the doors between the first three, if any, shall be opened to both directions;

II. The doors of the distribution unit room and capacitor room leading outdoors shall be installed with spring locks;

III. The ventilation windows of the distribution unit room, capacitor room and transformer room shall be protected against entry of petty animals;

IV. The doors leading outdoors and the windows able to be opened in the control room shall be provided with screen doors and windows.

Article 5.6.5 Natural lighting shall be adopted for the control room and should be adopted for the distribution unit room and capacitor room.

Article 5.6.6 Effective water proof measures shall be taken for the cable trenches and cable room of the distribution substation.

A distribution substation with operators on duty and a maintenance room shall be provided with washbasins and a mob sink.

Article 5.6.7 The heating and ventilation of a distribution substation shall meet the following requirements:

I. The values listed in Table 5.6.7 should be taken for the temperature conditions of various rooms in the distribution substation;

Table 5.6.7 Temperature conditions of various rooms in a distribution substation (c)

No. Description

Temperatures in winter/summerAir outlet temperature & temp.

difference in summer

Winter Summer max. Outlet temp.Inlet/outlet temp.

difference

1

2

3

4

5

6

Control room

Battery room

Capacitor room

Reactor room

Transformer room

Distribution unit room

16 ~ 18

10 ~ 15

5 ~ 10*

32

40

40

--

--

40

55

45

--

--

30

15

Note: *indicates when the distribution unit is under non-centralized control in the heating area.

II. Natural ventilation is normally adopted for the substation and mechanical ventilation may be adopted for the capacitor unit room, reactor room and HV distribution unit room;

In case of mechanical ventilation, the air duct shall be made from nonflammable materials;

In case of high dust content in the ambient air, the air to be sent into the room shall be purified;

III. The distribution unit room shall be heated with light tube radiator, the tubing of which shall be welded, without any valve.

Article 5.6.8 There shall be no irrelevant piping passing through the control room, distribution unit room, capacitor room and transformer room and the holes and openings where the relevant pipes go through the walls and floors shall be tightly blocked.

Article 5.6.9 The cable trenches should be provided with reinforced concrete slab covers. Chequered plate covers may be used where they need be frequently opened for maintenance. The covers shall be smooth and steady, light and convenient, and covers with lifting rings shall be properly arranged.

Section VII Fire Protection Requirements

Article 5.7.1 Except that the oil-immersed transformer room is under grade 1 fire protection, all the other buildings in a distribution substation are under grade II fire protection.

Article 5.7.2 In one of the following cases, the doors of the transformer room shall be fire protection doors:

I. The transformer room is located in the workshop;

II. The transformer room is located where flammable dust and fibers tend to deposit;

III. The transformer room is located on the second floor and above of a building.

Article 5.7.3 When the gabarit of an outdoor oil-immersed transformer is within 5m from the external wall of the building, there shall be no door/window and vents on the wall in the range of the transformer ’s total height

gabarit plus 3m on both sides (1.5m on both sides when the transformers oil is under 1000kg).

Article 5.7.4 In one of the following cases, the transformer room shall be provided with an oil retaining facility that can accommodate 100% of the transformer oil or a drainage measure for draining the oil to a safe place:

I. The transformer room is located where flammable dust and fibers tend to deposit;

II. The transformer room is located on the second floor and above of a building.

Article 5.7.8 In an outdoor or semi-outdoor substation, when the transformer oil is 1000kg or more, an oil retaining facility than can accommodate 100% of the oil amount shall be provided.

Chapter VI Selection & Laying of Cables

Section I Selection of Cables

Article 6.1.1 The cables shall be selected in accordance with such conditions as the ambient environment, the technical parameters of the power consumers and the laying method.

Article 6.1.2 The materials of the cables shall be selected according to the following stipulations:I. In the following cases, copper core cables shall be adopted:1. Explosion hazard environments of zone 1 or zone 10;2. Environments containing substances corrosive to aluminum; 3. Frequently moved cables;4. Environments with sever vibration;5. Excitation circuits of DC motors and synchronous motors;6. Control circuits or other secondary circuits.II. Copper core cables should be used for the cable lines in the explosion hazard environment of zone 2.

Article 6.1.3 The sectional area of a cable line shall be selected according to the secular allowable current-carrying capacity in which all correction factors are takes into account. The hot stability of the cable shall be checked with the three phase short circuit current under allowable voltage loss and maximum system operating condition.Checking of the short circuit hot stability may be omitted for cable lines with fuse protection or for LV distribution.

Article 6.1.4 Crosslinking polyethylene insulated cable should be adopted for HV cable lines; while PVC or crosslinking polyethylene insulated cable should be adopted for LV cable lines.

Article 6.1.5 Cables with plastic bushings should be used for open cable lines; corresponding armored cables shall be used where mechanical damage might occur; steel band armored cables should be used for direct embedded lines; and flexible stranded cables shall be used in environments with severe vibration.

Article 6.1.6 The method of using a 3 core cable plus a single core cable as the neutral line shall not be adopted for the power cable used in an LV three phase four wire system.

Article 6.1.7 When different heat radiation conditions exist along the route of the cable, the line section under the worst radiation condition (no less than 10m) shall be taken as the basis for consideration.

Article 6.1.8 When multiple cables are laid in parallel in a cable trench filled with sand, the comprehensive factor for reduced the current-carrying capacity (including soil heat resistance factor, multiple cable parallel laying factor and temperature factor) shall be taken into account, which should be 0.5 ~ 0.6.The cable current-carrying capacity shall be corrected according to the ambient temperature where the cable is laid. Please refer to Table 6.1.8-1.When the ambient environment is air, the maximum mean atmospheric temperature of the hottest month at the cable laying location shall be taken as the air temperature.When the ambient environment is soil, the mean ground temperature of the hottest month over the years at the cable laying location shall be taken as the soil temperature.

The air temperature plus 5 C may be taken as the temperature in the cable trench. Please refer to Table 6.1.8-2 for the correction factor of the soil heat resistance factor. The cable current-carrying capacity shall also be corrected according to the cable laying method. Please refer to Table 6.1.8-3, 6.1.8-4 and 6.1.8-5. For checking the short circuit hot stability, the maximum allowable temperature of the cable core can be found in Table 6.1.8-6.

Table 6.1.8-1 Current-carrying capacity correction factor at varied ambient temperature

Working temp. of core (C)

Current-carrying capacity correction factors under different ambient temperatures C

5 10 15 20 25 30 35 40 45

90

80

65

60

50

1.14

1.17

1.22

1.25

1.34

1.11

1.13

1.17

1.20

1.26

1.08

1.09

1.12

1.13

1.18

1.03

1.04

1.06

1.07

1.09

1.0

1.0

1.0

1.0

1.0

0.96

0.95

0.94

0.93

0.90

0.92

0.90

0.87

0.85

0.78

0.87

0.85

0.79

0.76

0.63

0.83

0.80

0.71

0.66

0.45

Table 6.1.8-2 Correction factors for different soil heat resistance factors

Cable section (mm2)

Soil heat resistance factor Pr (cm C / W)

60 80 120 160 200

2.5 ~ 16

25 ~ 95

120 ~ 240

1.061.081.09

1.01.01.0

0.900.880.86

0.830.800.78

0.770.730.71

Note: ① Common soil means the soil in normal plain areas, such as North China and Northeast China, and 120cm C / W may be taken as Pr.

② Dry soil means the soil in plateau areas, mountain areas with little rainfall, dry hilly land and so on and 160 ~ 200cm C / W may be taken as Pr.

③ Damp soil means the soil in coastal, lake side and river side areas and such areas with much rainfall as East China, South China and so on, and 60 ~ 80cm C / W may be taken as Pr.

Table 6.1.8-3 Current-carrying capacity correction factor for

multiple embedded cables laid in parallel Number of parallel

cablesClearance between cables (mm)

1 2 3 4 5 6 7 8 9 10 11 12

100

200

300

1.00

1.00

1.00

0.90

0.92

0.93

0.85

0.87

0.90

0.80

0.84

0.87

0.78

0.82

0.86

0.75

0.81

0.85

0.73

0.80

0.85

0.72

0.79

0.84

0.71

0.79

0.84

0.70

0.73

0.83

0.70

0.78

0.83

0.69

0.77

0.83

Table 6.1.8-4 Current-carrying capacity correction factor for

multiple cables laid in parallel in air Qty. of cables 1 2 3 4 5 4 6

Parallel moded s

Cable center

distance

S=dS=2dS=3d

1.001.001.00

0.901.001.10

0.850.981.00

0.820.950.98

0.800.900.96

0.800.901.00

0.750.900.96

Note: When the outer diameters of the cables laid in parallel are different, the mean outer diameter of the cables may be taken as value d.

Table 6.1.8-5 Current-carrying capacity correction factor for cables laid in bundle in cable bridge

Number of cable layersLaying method

Ladder support Cable tray

1 layer

2 layers

3 layers

4 layers

0.8

0.65

0.55

0.5

0.7

0.55

0.5

0.45

Note: ① The influence of alternated laying of power cable and control cable, power cable load rate and simultaneous factor has been taken into consideration for the correction factors listed in this table② A cable bundle is normally composed of 6 ~ 10 or more cables.③ The temperature factor is not included.

Table 6.1.8-6 Max. allowable temperature of cable core at short circuit C

DescriptionMax. allowable temperature C

Copper core Aluminum core

Crosslinking polyethylene insulated cable

EPR insulated cable

PVC insulated cable

Rubber insulated cable

250

250

130

100

200

--

130

100

Section II General Requirements for Cable Laying

Article 6.2.1 The following principles shall be observed in selection of the routes of cable lines:

I. Easy laying and short route;

II. Places with possible external damages, vibration, corrosion and heating should be avoided;

III. Far from the releasing sources of explosion hazardous gas or vapor;

IV. Along the less hazardous side of the piping when the cable is laid along a pipeline or pipe rack delivering inflammable gas or liquid; above the pipe when the inflammable gas or vapor is heavier than air and below the pipe when it is lighter than air;

V. Convenient for maintenance and repair.

Article 6.2.2 Where the cable lines enter or leave the cable room, cable shaft, cable trench and so on and the holes and openings for the cable lines to pass through the walls or floors between different explosion hazard environments shall be tightly blocked.

Article 6.2.3 The cable supports shall be made from noncombustible materials and the steel supports, if used, shall be galvanized. The supports should be applied with anticorrosion painting or spray painting.

Article 6.2.4 The bending radius of the cable shall be no less than that specified in Table 6.2.4.

Table 6.2.4 Cable bending radius to outer diameter ratio

Cable types Single core Multi core

Crosslinking polyethylene insulated cable

EPR insulated cable

PVC insulated cable

20

10

10

15

10

10

Article 6.2.5 Refer to Table 6.2.5 for the maximum distance between cable supports or fixed points.

Table 6.2.5 Maximum distance between cable supports or fixed points

Cable laying method Power cable (mm) Control cable (mm)

Horizontal laying

Vertical laying

10001500

8001000

Section III Cable Laying Method

Article 6.3.1 Open laying of cables shall meet the following requirements:I. Cable supports, cable bridges (ladder supports, trays and troughs), overhead galleries and steel cable suspension may be adopted for open laying of cables;II. For open laying of unarmored cables indoor, those parts under 2.5m from the ground in case of horizontal laying and under 1.8m from the ground in case of vertical laying shall be protected against mechanical damage, except for open laying in a special electrical room (e.g. the distribution room, motor room, etc.);III. Where the cables pass through walls or floors, they shall be run in pipes or protected with other measures;IV. Direct sunlight should be avoided for outdoor open cables;V. In case the cables are horizontally suspended on steel cables, the space between the power cable fixed points shall be no greater than 0.75m and that between the control cable fixed points shall be no greater than 0.6m;VI. The clearance between the open cable and the thermal piping shall be no less than 1m, otherwise thermal insulation measures shall be taken; the clearance between the open cable and other piping shall be no less than 0.5m, other wise mechanical damage protection measures shall be taken.

The cross clearance between the open cable and the thermal insulated vapor piping and general piping should be no less than 0.2m, but mechanical damage protection measures shall be taken when the cross clearance falls under 0.5m (no less than 0.5m from the outer side of the piping).

Article 6.3.2 Direct embedding of cables shall meet the following requirements:I. Two power cable lines supplying power to the same load point should be separately laid or their horizontal spacing shall be increased if separate laying is impossible;II. Permanent marks shall be provided for the cable lines at the terminals, bends and intermediate connections and every 30 ~ 50m along the straight lines;III. The parallel or cross clearances of the cable lines with various facilities shall be no less than the values listed in Table 6.3.2. It is strictly forbidden to lay the cable in parallel over or under the pipe;

Table 6.3.2 Min. clearance of direct embedded cables from various facilities

Description Laying conditions

Parallel CrossFoundations of buildings and structures 0.6Electrical wire poles 0.6Trees 1.5Underwood 0.5Communication cables 0.5 0.5Thermal pipe trenches 2.0 (0.5) (0.5)Water piping and compressed air piping 1.0 (0.25) 0.5 (0.25)Flammable gas & inflammable liquid piping 1.0 0.5Oil piping 1.0 0.5Other piping 0.5 0.5Railroad (from rails when in parallel and rail flange when crossed)

3.0 1.0

Highway (from curb when in parallel and surface when crossed)

1.5 1.0

Road (from curb when in parallel and surface when crossed)

1.0 0.7

Drainage trenches (from trench side when in parallel and trench bottom when crossed)

1.0 0.5

Note: ① The clearances listed in the table shall start from the outer edges of various facilities.② The road lamp cables are in parallel with underwood along the road and the distance is not limited.③ The values in parenthesis in the table mean the minimum allowable local clearances of cables that are protected with pipes, spacers or thermal insulation.

IV. The surface of the cable shall be no less than 0.8m from the ground surface and the embedding depth of cables in cold areas shall be properly increased according to the freezing depth of the soil;

V. Cables shall be routed away from corrosive places or, when it is necessary to pass through the said places, plastic bushing cables shall be used or other anticorrosion measures shall be taken;

VI. The direct embedded cables shall be laid with 100mm soft soil or sand layers (containing no stones or other hard matters) over and under them and covered with concrete slabs or bricks, with the covering width extending beyond both sides of the cables by 50mm;

VII. Cables shall be protected with pipes at their crossing points with roads and railroads and the protecting pipes shall extend out of the roadbed by 1m;

VIII. Cables shall be protected with asbestos cement pipe at their crossing points with thermal pipe trenches; the protecting pipes shall extend beyond both sides of the thermal pipe trenches by 2m and, when protected with thermal insulation, shall extend beyond both sides of the thermal pipe trenches and the cables by 1m;

IX. When laid in parallel with a building, the cable shall be embedded out of the range of the apron slope; at the entering point into a building, the protection pipe of the cable shall extend beyond the building’s apron slope by 0.25m;

X. Cables directly embedded indoor shall run through protection pipes, whose inner diameter shall be no less than 1.5 times the outer diameter of the cable.

Article 6.3.3 Laying of cables in cable trenches shall meet the following requirements:

I. The cable trenches should be built with brick structure (or of concrete structure in case of higher underground water level than the trench bottom) and reinforced concrete covers and, where it is subject to downward pressure or side pressure exerted by heavy objects, shall be reinforced with proper measures according to the possible load;

II. The cover slabs of indoor cable trenches shall be made flush with the indoor ground and all the gaps should be sealed with cement mortar when dust and water tend to accumulate on the ground;

The cover slabs of outdoor cable trenches should also be sealed with cement mortar;

III. Cable trenches shall be provided with drainage measures and the slope of the trench bottom should be no less than 0.3%;

IV. The weight of the cable trench covers should not exceed 50kg and steel covers are recommended for those indoor cable trenches that will be opened frequently;

V. The clearances of cables laid in cable trenches shall be no less than the values listed in Table 6.3.3;

Table 6.3.3 Min. clearances of cables laid in cable trenches

DescriptionLaying conditions

Trench depth <600mTrench depth 600mm

Width of walkway, cable supports on one side 300 450Width of walk way, cable supports on both sides 300 500Vertical clearance between cable support layers

Power cable 150 150Control cable 100 100

Horizontal clearance between power cables 35 35Clearance from top cross strut to cover slab 150 ~ 200 150 ~ 200Clearance from bottom cross strut to trench bottom 50 ~ 100 50 ~ 100

VI. The crossing sections of the cable trenches with railroad or highway shall be reinforced with proper measures;

VII. The entering points of the cable trenches into buildings shall be provided with sealing measures;

VIII. Cable trench laying method is not recommended for strong and medium corrosive environments;

IX. When the explosive gas or vapor is heavier than air, the cable trenches in the explosion hazard environment shall be filled with sand. The general requirements for the sand filled cable trenches are as follows:

1. Sand filled shallow trenches up to 800mm are recommended;

2. The cables laid in the trench should not exceed 4 layers;

3. The bottom of sand filled cable trenches shall be covered with a concrete bed course and a uniform 100mm thick layer of sand. No supports shall be installed in the trenches. The vertical clearance between cable layers is 100mm. The whole cable trench shall be filled with sand after the cables are laid. The trench shall be covered with reinforced concrete slabs on the top. The cover slabs and gaps shall be sealed with cement mortar;

4. The LV power cable and control cable may be laid in parallel while the HV power cable should be laid separately;

5. Cables of large sectional areas should be laid on the upper layer or along the side of the sand filled cable trench;

6. The entry point of the sand filled cable trench into a building shall be provided with sealing measures;

7. Water drainage and sand drifting protection measures shall be taken for the sand filled cable trench;

8. Backup positions should be reserved on the top layer of the sand filled cable trench.

Article 6.3.4 Laying of cables on cable bridges shall meet the following requirements:

I. Approved products shall be used for cable bridges and buildings, structures and process pipe racks should be utilized as the supporting members;

II. Ladder supports, cable trays and cable troughs may be selected for cable bridges;

III. For protection from sunlight and mechanical damage, cable bridges with protecting covers shall be adopted;

IV. Cables going up and down the cable bridge shall be protected against mechanical damage;

V. No more than two layers of cables should be laid on each layer of cable bridge, with three or four layers cables only to be laid when the path is very crowded;

VI. The HV power cable and two power cables supplying power to the same load point should be laid separately; the power cable and control cable for the same LV power consumer should be laid side by side;

VII. Anticorrosion measures shall be taken for cable bridges in corrosive environments;

VIII. When cable bridges are selected, backup positions should be reserved;

IX. Additional load applied during installation and maintenance shall be take into consideration for the designed load of a cable bridge;

X. Reliable electrical connections and grounding shall be provided between cable bridges.

Chapter VII Motor and Lighting

Section I General Provisions

Article 7.1.1 Selection of the local control protection devices for the power-driven equipment shall comply with the selection of electrical equipment and meet the relevant provisions for the requirements for environmental characteristics.

Article 7.1.2 Selection of the cross-section for the conductors of insulated wires and cables shall meet the following requirements:

I. The permissible long-time current carrying capacity of conductors shall not be less than the calculated current of the maximum continuous load for line.

II. The voltage bias value of the endpoint of power-driven equipment shall be checked, and the starting voltage variation value shall be checked for some individual motors.

III. Relatively long-distance control line shall ensure the reliable operation of the starting equipment.

IV. Relatively long-distance measuring line shall be checked for the permissible load of transformer.

V. According to the requirements for mechanical strength, the cross-section of cores for the insulated wires shall not be smaller than the values indicated in Table 7.1.2. However, the min. cross-section of wiring in the explosive hazard locations shall meet the relevant provisions of Chapter IV.

VI. The long-time permissible current carrying capacity of the working neutral line for the gas discharge lamp shall not be less than the calculated current for a phase with the max. load.

Table 7.1.2 - Min. Cross-section of Cores for Insulated Wires

Services Min. Cross-section of Cores (mm2)

Cord with copper core Wire with copper core Wire with aluminum core

I. Mobile power-driven equipment

1.5

II. Wiring with conduit

1.5 1.5 2.5

Article 7.1.3 In the production plant the power supply box for the maintenance purpose shall be provided, and the radius for supplying power should not be greater than 30m.

Section II Set up of Control Equipment for Motors

Article 7.2.1 Individual starting device shall be equipped for motors. A common starting device is not allowed to be used by several motors unless it is required by the production mechanical unit or the process.

For the local control of operation for irreversible squirrel-cage motor 4.5 kW, when the starting up is not frequent and no interlock is required, the load switch (the switch with iron housing), switch group or ON/OFF

knob switch may selected and used as the starting devices.

Article 7.2.2 It is recommended to be controlled or monitored locally, but when there is one of the following conditions, the remote control or DCS may be used for the control or monitoring:

I. Environmental conditions are severe at the site or locations where the operation personnel should not be kept staying for a long period.

II.The objects to be controlled are dispersed and it is not convenient to implement the unified marshalling and control.

III. The objects to be controlled are far away and patrol inspections are not made frequently.

III. It is required by a high-level automation or the process specialty.

Article 7.2.3 When it is a local control, an ON/OFF control switch is provided by the machine locally. When it is a multi-point control, the following requirements should be followed to set up control switches:

I. Control room: to provide ON/OFF control switch and selector switch for operating modes (e.g. Central Control/Local Control; Auto/Manual);

II.By the machine: Based on the specific conditions to set up the control switch using one of the following :

1. ON/OFF control switch and selector switch of operating modes allowed for starting up in the control room.

2. Emergency STOP switch.

The selector switch for operating modes shall be located by the machine or somewhere in the control room. When the selector switch for operating modes is set up in the control room, the control switch in field (push-button or knob) shall be provided with a locking position.

Article 7.2.4 The local control device (switches) should be installed in a position for easy operation and close to the motor, and in case it is not possible to see the mechanically driving part, the following measures shall be taken to prevent accidents:

I. To set up pre-warning audible signal device;

II.A switch for stopping the start up are provided nearby the motor and driven machinery.

Article 7.2.5 The mains of control circuit for individual control of LV motor should be connected from its main circuit. In case it is connected from the other power supply, the control circuit shall be cut off when the mains of its main circuit switch is OFF.

Article 7.2.6 The control circuit of motor should use phase voltage, and isolation transformer may be used if necessary. When DC power supply is used, it is recommended to use an isolated neutral system.

Article 7.2.7 Motor or motor group may be provided with necessary interlock and automatic control system according to the requirements of the process, and the system shall meet the following requirements:

I. Motor group or the motors to be started up in succession shall comply with the specification of voltage variation.

II. Non-coulometric contacts shall comply with the requirements for reliable ON/OFF, and contacts shall be changed over if necessary.

III. Selector or changing-over switches shall be set up for controlling the throwing-in and blocking-out of the interlock.

Article 7.2.8 Ammeter shall be set up by the motors 37 kW or the motors that need to be monitored for their current under operation.

Section III Protection of Motors

Article 7.3.1 HV motors shall be provided with the following protections:

I. Phase fault protection

1. Current quick-break protection is used for the motors < 2000 kW, and the protection device should use two-phase wiring.

2. Longitudinal differential protection is used for the motors 2000 kW. The motors < 2000 kW shall also be provided with the differential protection when their current quick-break capacity can not meet the requirement for sensitivity.

II.Single-phase ground protection

When the single-phase ground current is > 5A, this protection shall be provided. When the single-phase ground current is 10A, it activates the interlock, and it activates signals when it is < 10A.

III. Overload protection

The overload protection shall be provided for the motors that are subjected to overload in the production process. Inverse time relay should be used for this protection, and the inverse time part of protection device may activate interlock and also may activate signals or to decrease load automatically depending on conditions.

IV. Low-voltage protection

1. 0.5s is taken to activate the interlock for disconnecting the secondary motors in order to ensure the restart up of major motors.

2. The activation time is 5 - 10s for the motors that need to be restarted up.

V. Loss-of-synchronism protection

Synchronous motor shall be provided with an individual loss-of-synchronism protection device, and the protection device activates the interlock with time-delay, and it will activate the re-synchronizing system if necessary.

VI. Non-synchronous rush protection

The high-capacity synchronous motors should be provided with the protection for short-time power failure and the non-synchronous rush resulted in when the power is restored.

Article 7.3.2 LV motors shall be provided with the following protections:

I. Phase fault protection

1. Fuse protection;

2. Instantaneous trip relay protection of automatic air breakers;

3. Some specific major motors with high-capacity may be provided with over-current relay individually, and it activate the overload instantaneously;

4. LV motors should be provided with independent short-circuit protection, and a group of motors which are closely related in process may share a common short-circuit protection device, however, it can be inactivated immediately when any motor in the group is found in failure.

II. Single-phase ground protection

When the phase fault protection can comply with the sensitivity of the single-phase ground fault, it may also used for the single-phase ground protection, otherwise, the single-phase ground protection shall be provided individually.

III. Overload protection

The following motors shall be provided with overload protection:

1. The motors that are easy to be subjected to the overload or blocking;

2. The motors that are difficult to be started up or restarted-up or need to have limited starting-up time.

3. The motors that operate continuously for a long time or run without monitoring by any operator.

Thermal relay, or long-delay over-current drop relay of automatic air breaker may be used for the overload protection of motors, and the individual inverse time over-current relay may also be used.

Protections for the increased-safety motors shall match up with the blocking time.

IV. Open-phase protection

Continuously running motors should be provided with open-phase protection.

V. Low-voltage protection

1. The motors that are not required to be restarted up, shall be provided with a low-voltage protection with instantaneous activation or short-delay ( 0.5s) activation.

2. The motors that are required to be restarted up, shall be provided with the low-voltage protection with a time-delay of 10s.

VI. Leakage protection

Leakage protection may be provided according to the conditions.

Article 7.3.3 The control circuit of motor shall be provided with the short-circuit protection. When the mains of the control circuit is connected from the main circuit and the protection device of main circuit can provide the protection for the wiring of control circuit, no such protection is required to be provided.

Section IV Wiring Modes for Motor and Lighting

Article 7.4.1 Cable or insulated wire with conduit should be used for the wiring of LV motors, and the wiring shall be mainly in a radiation mode. A trunk wiring mode may also be used for certain loads.

Article 7.4.2 Cable shall be used for wiring in a radiation mode for HV motors.

Article 7.4.3 Wiring mode for indoor lighting shall be as follows:

I. Insulated wires with surface-mounted steel conduits should be used for the production buildings.

II. Insulated wires with flush-mounted steel conduits shall be used for the instrument and electrical control rooms and buildings for auxiliary facilities.

Article 7.4.4 Insulated wires with surface-mounted conduits shall be used for the outdoor plant area, and the surface laid cables are also allowed when the conditions are permitted. Cable to be buried directly underground is allowed for some individual sections.

Section V Lighting Modes and Classifications

Article 7.5.1 Lighting modes are classified as the normal lighting and the emergency lighting.

Article 7.5.2 Outlets for the normal lighting, emergency lighting and maintenance lighting should be provided within the production plant.

Article 7.5.3 Obstruction lighting shall be installed for the chimneys and high towers in accordance with the relevant stipulations.

Article 7.5.4. Illumination for various kinds of production plants shall comply with the requirements made in《Regulations on Illumination Design of Production Plants of Petrochemical Enterprises》.

Section VI Lighting Network Voltage and Power Supply & Distribution

Article 7.6.1 Selection of lighting network voltage shall comply with the following provisions:

I. 380V/220V 3-phase & 4-wire system or 3-phase & 5-wire system should be used for the normal lighting or emergency lighting.

II. 36V should be used as the normal lighting voltage for especially damp locations. When measures are taken to prevent electric shock, 220V is permitted.

III. The voltage of maintenance lighting used for the portable lighting lamps shall be 36V.

IV. The voltage of maintenance lighting used in metal vessels or narrow spaces where it is easy to get contacted with the ground conductors shall be 12V.

Article 7.6.2 Common transformer should be used to supply the power for normal lighting and motor loads. Separate transformer may be used to supply the power for lighting if necessary.

Article 7.6.3 Substation shall be provided with distribution panel for lighting to supply the power to lighting boxes in a radiation mode. It is also allowed to use the trunk line for supplying the power, but it is recommended no more than 2 distribution boxes are used on one circuit.

Article 7.6.4 Emergency security power supply system should be used to supply the power for the emergency lighting or the emergency lighting lamps should be used.

Article 7.6.5 A transformer of 220V/12~36V should be used to supply the power for the maintenance lighting.

Article 7.6.6 Control modes for lighting shall be as follows:

I. Locally dispersed or centralized control mode should be used in normal locations.

II. Lighting boxes should be used for the centralized control for the locations with explosive hazards or large-sized plant buildings. Some individually dispersed lighting fixtures may also be controlled locally and dispersedly.

III. Manual control or photoelectric auto control should be used for the outdoor plant area.

Section VII Light Source Selection

Article 7.7.1 Fluorescent lamps should be used for the instrument control room, electrical control room, night shift rooms, offices and distribution unit room.

Article 7.7.2 Mixed-light illuminant shall be used for the normal lighting of high and large production buildings.

Article 7.7.3 Depending on the conditions, fluorescent lamps, incandescent lamps, HT sodium lamps and HT mercury lamps or the projection lamps with the aid of HT mercury lamp and HT sodium lamp may be used for the tower group and outdoor plant areas.

Article 7.7.4 Illuminant lamps that can be lighted up instantaneously and reliably shall be used for the emergency lighting.

Article 7.7.5 Incandescent lamps should not be used in the vibration locations.

Section VIII Selection and Layout of Illuminators

Article 7.8.1 Illuminators with high efficiency and easy maintenance shall be selected and used under the conditions of meeting the requirements of the environmental characteristics and visual sense and of light intensity distribution and limiting glare.

Article 7.8.2 Illuminators shall be selected according to the following environmental conditions:

I. In normal places or the places with high humidity, open-type illuminators should be used.

II. In the damp locations, closed-type water-proof and dust-proof illuminators or the open-type illuminators with water-proof lamp holders should be used.

III. Dust-proof illuminators should be used in the locations where there are dusts, but no explosive and fire hazard.

IV. Lamp fixtures used in the locations with relatively intensive vibration shall be provided with anti-hunting measures.

V. Lamp fixtures subjected to the mechanical damages or in low positions shall be protected with guard meshes.

VI. The anti-corrosion illuminators shall be used in the environment with a corrosive atmosphere.

VII. The illuminators used in the locations where there are explosive and fire hazards shall be selected and used

according to the relevant stipulations.

Article 7.8.3 Minimum suspension heights of illuminators above the ground should not be less than the values indicated in Table 7.8.3 in order to limit glare.

Article 7.8.4 Minimum suspension heights of illuminators specified in Table 7.8.3 may be reduced by 0.5m but shall not be less than 2m in the rooms specified below.

I. Rooms with illumination of normal lighting is less than 30Lx ;

II. Rooms with a length equal to or less than 2 times the suspension height of illuminators;

III. Rooms for personnel to have a temporary stay.

Article 7.8.5 When the position of illuminator is higher than sight line of people, its protection angle shall not be less than 30o, and when it is below the sight line of people, its protection angle shall not be less than 10o.

Article 7.8.6 In order to obtain an even illumination, the ratio of l (spacing between illuminators) to h (the calculated height) may be based on the values specified in Table 7.8.6.

Article 7.8.7 Installation position of light fittings shall be convenient for maintenance, and the requirements are as follows:

I. The suspension height should not be greater than 6m for those light fittings which require ladder to carry out maintenance.

II. Crane shall be used to carry out the maintenance for those light fittings installed on trusses.

III. No light fittings shall be installed in the locations where it is unsafe or difficult to carry out the maintenance for light fittings.

Table 7.8.3 - Minimum Suspension Height of Illuminators

Types of light source

Types of reflector Protection angle

Capacity of lamp bulb

(W)

Min. suspension height (m)

Incandescent lamp

Enamel reflector 10o ~ 30o ≤ 100150 - 200300 - 500

2.53.03.5

Opal glass diffused reflector ≤ 100150 - 200300 - 500

2.02.53.0

HT mercury lamp

Enamel reflector 10o ~ 30o ≤250 5.0

Fluorescent lamp

Aluminum polished reflector 10o ~ 30o ≤ 40 6.0

Fluorescent lamp

Without reflector ≤ 40 2.0

Halogen tungsten lamp

Enamel reflectorAluminum polished reflector

≥30o

≥30o

500≤ 1000

6.07.0

Types of light source

Types of reflector Protection angle

Capacity of lamp bulb

(W)

Min. suspension height (m)

HT sodium lamp

Enamel reflectorAluminum polished reflector

10o ~ 30o

10o ~ 30o

250400

6.07.0

Metal halide lamp

Enamel reflectorAluminum polished reflector

10o ~ 30o

30o

4001000

6.014.0

Table 7.8.6 - l/h Values for Well-distributed Illuminators

Types of illuminators l/h values

Balancing illumination, General illumination 1.4 ~ 2.0

Deep illumination, Mirror deep illumination 1.3 ~ 1.8

Anti-explosive lamp, Spherical lamp, Ceiling lamp 1.8 ~ 2.4

Fluorescent tube (simple type) 1.3 ~ 1.5

Article 7.8.8 There shall be an appropriate distance between the positions of illuminators and process equipment, piping, etc. No lighting fixtures shall be installed above the bus of power distribution unit.

Annex I - Tables of Classification of Zones for

Explosive-hazard Locations of Petrochemical Production Units

Notes:

1. The following tables may be used as a reference for the classification of zones for the hazardous locations, as various factors and conditions have to be taken into consideration in a comprehensive way when the zones of hazardous locations are classified, especially the experience in operation of the similar production units has to be taken into consideration.

2. The zones of hazardous locations as classified in the tables are based on the following conditions:

(1). Outdoor or semi-outdoor units are considered as the units with natural ventilation.

(2). The indoor units are provided with mechanical ventilation as well as the stand-by ventilation system, and the number of air changes shall comply with these provisions.

(3). No other specific measures are considered such as setting up flammable gas detectors and monitors, filling up with nitrogen, getting isolated, etc.

Table 1 – Classification of Zones of Hazardous Locations for Petrochemical Production Plant

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

1 2 3 4 5 6I. Oil refining process units

(I) Atmospheric vacuum distillation unit

1 Cold oil pumping house

Gasoline, kerosene, diesel oil , pump oil

II AT3 A 2

2 Hot oil pumping house

Light & heavy diesel oil , heavy oil, residual oil

II AT3 B 2*

3 Open installation area Gasoline, kerosene, diesel oil , heavy oil

II AT3 A 2

(II) Catalysis & Cracking Unit

1 Cold oil pumping house

Liquid hydrocarbon, gasoline, diesel oil

II BT3 A 2

2 Hot oil pumping house

Light & heavy diesel oil , waxy oil, slurry recycle oil

II AT3 B 2*

3 Gas compressor room Rich gas, liquid hydrocarbon, condensed oil

II BT3 A 2

4 Open installation area Liquid hydrocarbon, gasoline, kerosene, diesel oil

II BT3 A 2

(III) Delayed Coking Unit1 Gas compressor room Rich gas, liquid hydrocarbon,

condensed oilII BT3 A 2

2 Cold oil pumping house

Liquid hydrocarbon, gasoline, diesel oil

II BT3 A 2

3 Hot oil pumping house

Heavy diesel oil , heavy oil, residual oil

II AT3 B 2*

4 120 & 180 pumping houses

Residual oil C 21

5 Open installation area Liquid hydrocarbon, gasoline, diesel oil , waxy oil

II BT3 A 2

(IV) Catalytic Reforming Unit

1 Hydrogen compressor

Hydrogen, methane, ethane, propane

II CT1 A 2

2 Cold oil pumping Hydrogen, gasoline II CT3 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

house3 Hot oil pumping

houseDiesel oil II AT3 B 2*

4 Open installation area Hydrogen, methane, ethane, gasoline, diesel oil

II CT3 A 2

(V) Alkylation Unit1 Ammonia

compressor roomAmmonia II AT1 B 2

2 Pumping house Liquid hydrocarbon, alkylate oil II BT3 A 23 Open installation area Liquid hydrocarbon, alkylate oil II BT3 A 2(VI) Polyunit 1 Pumping house Liquid hydrocarbon, gasoline II BT3 A 22 Open installation area Liquid hydrocarbon, gasoline II BT3 A 2(VII) Gas Fractionation

Unit1 Compressor room Dry gas, liquid hydrocarbon II BT3 A 22 Pumping house Liquid hydrocarbon 150 II BT3 A 23 Open installation area Dry gas,

liquid hydrocarbon 150II BT3 A 2

(VIII) Steam Reforming and Hydrogen Generation Unit

1 Compressor building Hydrogen, methane II CT1 A 22 Pumping house Cyclo- or ethanol amide II AT1 A 23 Open installation area Reforming gas, transforming

gas, cyclo- or ethanol amideII AT1 A 2

(IX) Hydrogenation & Cracking Unit for Waxy Oil, Heavy Oil & Residual Oil

1 Compressor building Hydrogen, hydrogen sulfide, methane

II CT3 A 2

2 HP oil pumping house

Waxy oil, heavy oil, residual oil C 21

3 Open installation area Hydrogen, hydrogen sulfide, methane, gasoline

II CT3 A 2

(X) Hydrogenation & Refining Unit for Gasoline, Kerosene, Diesel oil or Lube

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

Oil1 Compressor building Hydrogen, hydrogen sulfide,

methaneII CT3 A 2

2 HP oil pumping house

Gasoline, kerosene, diesel oil or lube oil

II CT3 A 2

3 Open installation area Hydrogen, hydrogen sulfide, methane, gasoline, etc.

II CT3 A 2

(XI) Lube Oils and Phenols Refining Unit

1 Pumping house Various types of lube oils and phenols

C 21

2 Open installation area Various types of lube oils and phenols

C 21

(XII) Lube Oil Argil Refining Unit

1 Pumping house Various types of feedstock lube oils

C 21

2 Refining tank, Filter building

Feedstock and product lube oils C 21 Classification of Fire Hazard

3 Feedstock and product storage tank yard

Feedstock and product lube oils C 21

(XIII) Ceresin Argil Refining Unit

1 Pumping house Raw oil, Liquid paraffin C 212 Filter building Refined liquid wax C 213 Shaper room and

Wax storage Refined liquid wax, wax block product

C 21

4 Feedstock & product storage tank yard

Feedstock and refined liquid wax

C 21

(XIV) Furfurol Refining Unit

1 Pumping house Raw oil, Refined oil, Furfurol II AT1 C 22 Open installation area Raw oil, Refined oil, Furfurol II AT1 C 2(XV) Propane Deasphalting

Unit1 Propane compressor

roomPropane (containing ethane and butane)

II AT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

2 Propane pumping house

Propane (containing ethane and butane)

II AT2 A 2

3 Propane storage tank yard

Propane (containing ethane and butane)

II AT2 A 2

4 Open installation area Propane (containing ethane and butane)

II AT2 A 2

(XVI) Ketone-benzol Dewaxing Unit

1 Vacuum filter room Propanone, benzene, oils II AT1 A 22 Vacuum compressor

roomPropanone, benzene II AT1 A 2

3 Feedstock pumping house

Propanone, benzene, oils II AT1 A 2

4 Ammonia compressor room

Ammonia II AT1 B 2

5 Double tube crystallization room

Propanone, benzene, oils II AT1 A 2

6 Open installation area Propanone, benzene, oils II AT1 A 2(XVII) Urea Dewaxing Unit1 Double-tube reactor

buildingUrea isopropanol, aviation kerosene

II AT3 B 2

2 Open installation area Aviation kerosene, diesel oil, lube oilSolvent: 1.Isopropanol; 2. Ethyl acetate; 3. Dichloroethane

II AT3 B 2

(XVIII) Molecular Sieve Dewaxing Unit

1 Pumping house Kerosene or light diesel oil, wax II AT3 B 22 Open installation area Kerosene or light diesel oil, wax II AT3 B 2(XIX) Paraffin Sweating

Unit1 Sweating tank room Waxy oil C 212 Pumping house Waxy oil C 21(XX) Paraffin Extraction

Unit 1 Compressor building Ammonia, lube oil II AT1 B 22 Pumping house Lube oil C 213 Filter press room Lube oil C 21

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

4 Double-pipe crystallization room

Ammonia, lube oil II AT1 B 2

5 Open installation area Ammonia, lube oil II AT1 B 2(XXI) Oxidized Asphalt

Unit1 Pumping house Goudron C 212 Open installation area Residual oil, asphalt C 21(XXII) Three Waste

Treatment Unit1 Three waste

treatment buildingSO2, CO2, H2S, amino-phenol, gasoline, phenol, naphthenic acid, ethanolamine, etc.

II AT3 A 2

2 Open installation area SO2, CO2, H2S, amino-phenol, gasoline, phenol, naphthenic acid, ethanolamine, etc.

II AT3 A 2

3 Sulfur recovery Sulfurous dust C 114 Sulfurous waste

waterII AT3 A 2

II. Basic Organic Chemical Materials and Products

(I) Methane Partially Oxidizing and Acetylene Unit

1 Olefin acetylene Methane, acetylene II CT2 A 22 Acetylene

concentration and ethylene purification

Acetylene, methane II CT2 A 2

(II) Tubular Furnace Pyrolysis Ethylene & Propylene Unit

1 Pyrolysis and phrolysis area (open flame)

Light oil, hydrogen, methane, ethylene, propylene

II AT3 A 2*

2 Quenching area Hydrogen, methane, ethylene, propylene

II AT2 A 2

3 Compression Hydrogen, methane, ethylene, II AT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

(pyrolysis area) propylene4 Refrigeratin Ethylene, propylene II AT2 A 25 Separation cold area Hydrogen, methane, ethylene,

propyleneII AT2 A 2

(III) Regenerative Furnace Pyrolysis Ethylene Unit

1 Pyrolysis (with heavy oil as feedstock)

Hydrogen, methane, ethylene, propylene

II AT3 A 2

2 Compression (pyrolysis gas)

Hydrogen, methane, ethylene, propylene

II AT3 A 2

3 Separation Hydrogen, methane, ethylene, propylene

II AT3 A 2

4 Refrigeration with ammonia

Ammonia II AT1 B 2

(IV) Extracting Butadiene from C4 Unit

1 Extraction butadiene from C4

Butane, butene, butadiene II BT3 A 2

2 Iso-butene separation Butane, (N) butene, Iso-butene II BT3 A 23 Extracting butadiene

from butene with oxidation and dehydrogenationFront and back acetonitrile

Butane, butene, butadiene II AT2 A 2

Dehydrogenation Butene, butadiene II BT3 A 2Compression (gas generation)

Butene, butadiene II BT3 A 2

(V) Synthetic Alcohol Unit

1 Absorption & Boiling-out with Sulfur Acid Method

Ethylene, ethanol II BT2 A 2

2 Rectification Ethanol II BT2 A 23 Intermediate storage

tank yardEthanol II BT2 A 2

(VI) Direct Method Acetaldehyde Unit

Ethylene, acetaldehyde II BT2 A 2

(VII) Acetic Acid Unit Ethylene, ester acid II BT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

(VIII) Pyrolysis Gasoline Hydrogenation

1 Hydrogenation and fraction of hydrogen

Hydrogen, benzene, toluene, xylenes

II CT1 A 2

2 Hydrogen gas compressor

Hydrogen II CT1 A 2

(IX) Aromatics Extraction Unit

Benzene, toluene, xylenes II A 2

(X) Paraxylene Unit1 Toluene dismutation

& isomerigationBenzene, toluene, xylenes II A 2

2 Fraction Benzene, toluene, xylenes II A 23 Separation of mixed

xylenesXylenes II A 2

(XI) Acrylonitrile Unit1 Feedstock air

compressor roomAir E

2 Corresponding acrylic ammonia (oxidation)

Propylene, ammonia II A 2

3 Pre-refining and rectification

Acrylonitrile, acetonitrile, ammonocarbonous acid

II AT2 A 2

4 Concentrated cyanide waste water boiling out furnace

Cyanide D

5 Cyanide waste water biochemical treatment station

Cyanide E

6 Cymag section Ammonocarbonous acid, caustic soda

E

(XII) Phenol & Propanone Unit

1 Hydrocargonylation Benzene, propylene, iso-propylene

II AT2 A 2

2 Oxidation II AT2 A 23 Rectification and

pumping house (hydrocarbonylated and oxidized products)

Iso-propyl benzene, phenol, propanone

II AT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

(XIII) Chlorethylene Unit (oxo-chlorination process)

1 Chlorine compressor building

Chlorine E

2 Ethylene compressor building

Ethylene II BT2 A 2

3 Main process production units (including direct chlorination, oxidation, and rectification of dichloroethane and chlorethylene, pumping house)

Ethylene, chlorine, dichloroethane, chlorethylene

II BT2 A 2

4 Cracking of dichloroethane (open flame)

Dichloroethane, chlorethylene

II AT1 A 2

5 Intermediate storage tank yard for dichloroethane and chlorethylene

Dichloroethane,chlorethylene

II AT1 A 2

6 Burning of residual liquid (open flame)

Organic chloride, hydrogen chloride

II AT1 A 2

7 Wastewater treatment E

(XIV) Chlorethylene generated with acetylene method

1 Acetylene generation (location nearby charge door is Zone 1)

Acetylene II CT2 A 2

2 Synthesizing hydrogen chloride (open flame or hot part)

Hydrogen, chlorine and hydrogen chloride

II CT2 A 2*

3 Synthesizing chlorethylene and

Acetylene, hydrogen chloride, chlorethylene

II CT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

rectification(XV) Butyl Actanol Unit 1 Process production

unit (including 2 stages of condensation and 2 stages of hydrogenation and refining)

Acetaldehyde, butanol, actanol, butenal, octenoic acid

II CT3 A 2

2 Hydrogen tank Hydrogen II CT1 A 23 Intermediate tank

yardButanol, actanol, II AT2 A 2

(XVI) Acetic Oxide Unit1 Cracking (open

flame)Acetic acid, ketene II AT1 A 2

2 Absorption and rectification

Ketebe, acetic acid, acetic oxide II AT1 A 2

3 Acetic acid recovery Acetic acid II AT1 A 2(XVII) Epoxychloropropane,

propylene glycol1 Propylene

compressor buildingPropylene II AT2 A 2

2 High-temperature chlorination and refining

Propylene, chloride, allyl chlorine

II AT2 A 2

3 Hypochlorination and refining

Allyl chlorine, Dichloro-propanol, epoxy, chloropropane, chlorine

II AT2 A 2

(XVIII) Styrene Unit1 Benzene

hydrocarbylationBenzene, ethylene, ethylbenzene II BT2 A 2

2 Dehydrogenation of ethyl benzene

Ethylene, ethylbenzene, hydrogen

II CT2 A 2*

3 Condensation of dehydrogenating furnace (open flame)

Ethylene, ethylbenzene, hydrogen

II CT2 A 2

4 Rectification of ethylbenzene and styrene

Ethylbenzene, styrene, benzen II AT2 A 2

(XIX) Glycol Unit

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

1 Air compressor room Air II BT2 E2 Recycle ethylene

compressor buildingEthylene II BT2 A 2

3 Oxidation, absorption and rectification

Ethylene, epoxyethane II BT2 A 2

4 High pressure hydration of epoxyethane

Epoxyethane, glycol II BT2 A 2

5 Rectification of glycol

Glycol II BT2 B 2

(XX) Triisobutylalunimium (TIBAL)

1 Activation of aluminum powder

Aluminum powder 11

2 Synthesis Aluminum powder, isobutene A 23 Filtering and refining Triisobutylaluminium A 2

III.Synthetic Rubber(I) Styrene-butadiene

rubber (SBR)1 Preparation of carbon

and hydrogen phaseButadiene, styrene II BT2 A 2

2 Preparation of water phase

Colophonic acid soap, fatty acid soap

E

3 Polymerization and degassing

Butadiene, styrene II BT2 A 2

4 Glue storage tank yard

Butadiene, styrene polymer

5 Final treatment (coacervation, drying, packing)

SBR C 23

6 Product intermediate storage

SBR C 23

7 Colophony section Colophony, caustic potash C 238 Fatty acid soap

sectionFatty acid, caustic potash E

(II) Acetonitrile Rubber1 Preparatio of water

phaseEmulsifier E

2 Polymerization and Butadiene, acrylonitrile II BT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

degassing 3 Final treatment

(coacervation, drying, packing)

Acrylonitrile-butadiene rubber C 23

(III) Ethyle-propylene Rubber (EPR)

1 Preparation of catalyst and aids

Vanadylic chloride, Chloroethyl aluminum

A 2

2 Polymerization Ethylene, propylene, gasoline II BT3 A 23 Condensation Ethylene, propylene, gasoline II BT3 A 24 Recovery of

monomer and solventEthylene, propylene, gasoline II BT3 A 2

5 Final treatment (dehydration, drying and packing)

Ethylene -propylene rubber (EPR)

C 23

(IV) Cis-1,4-polybutadience Rubber

1 Monomer and solvent storage tank yard

Butadiene, gasoline II BT3 A 2

2 Preparatio of catalyst and aids

Nickel naphthenate, trifluoride, triisobutyl, aluminum

II BT3 A 2

3 Polymerization Butadiene, gasoline II BT3 A 24 Condensation Butadiene, gasoline II BT3 A 25 Monomer and solvent

recoveryButadiene, gasoline II BT3 A 2

6 Final treatment (dehydration, drying and packing)

Cis-1, 4-polybutadience Rubber C 23

7 Product warehouse Cis-1, 4-polybutadience Rubber C 23(V) Chloroprene Rubber1 Generation of

acetylene Acetylene II CT2 A 2

2 Synthetic vinyl acetylene

Acetylene, vinyl acetylene II CT2 A 2

3 Synthetic chloroprene vinyl acetylene, chloroprene II BT2 A 24 Polymerization Chloroprene II BT2 A 25 Final treatment

(coacervation, drying and packaging

Chloroprene, chloroprene rubber II BT2 B 23

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

6 Product warehouse Chloroprene rubber C 23(VI) Isopentyl Rubber1 Olefine aldehyde

one-step synthesis of Isoprene

(1) Feedstock tank yard Isobutene, formaldehyde II BT2 A 2(2) One-step synthesis of

isopreneIsobutene, formaldehyde, isoprene

II BT2 A 2

(3) Compression of recycle isobutene

Isobutene II BT2 A 2

(4) Rectification Isobutene, isoprene II BT2 A 22 Olefine aldehyde

two-step synthesis of isoprene

(1) Feedstock tank yard Butane, vinyl, formaldehyde II AT2 A 2(2) Olefine aldehyde

Condensation Butane, vinyl, formaldehyde DMD

II AT2 A 2

(3) DMD DMD isoprene II AT2 A 23 Isopentyl rubber(1) Monomer and solvent

tank yardIsoprene, gasoline II AT3 A 2

(2) Preparatio of catalyst and aids

Naphthenic acid rare earth, gasoline

II AT3 A 2

(3) Polymerization Isoprene, gasoline II AT3 A 2(4) Coacervation Isoprene, gasoline II AT3 A 2(5) Monomer and solvent

recoveryIsoprene, gasoline II AT3 A 2

(6) Final treatment (dehydration, drying and packing)

DMD C 23

(7) Product warehouse DMD C 23IV. Synthetic Plastics and Resins

(I) Caprolactam 1 Cyclohexane

generated with hydrogenation of benzene

Benzene, hydrogen, cyclohexane II CT1 A 2

2 Cyclohexanone generated with

Cyclohexane, cyclohexanone II AT2 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

oxidation of cyclohexane

3 Cyclohexanol generated with hydrogenation of phenol

Benzene aldehyde, Cyclohezanol

II AT2 A 2

4 Cyclohexanone generated with dehydration of cyclohexanol

Cyclohezanol, cyclohexanone II AT2 A 2

5 Rectification of cyclohexanone

Cyclohexanone II AT2 A 2

6 Esterification, dislocation and neutralization

Cyclohexanone, cyclohexanone fat

C

7 Extraction and refining

Caprolalactam, chlorylene II BT2 B 2

8 Chipping and packing Caprolalactam C 23(II) Polyvinyl chloride 1 Polymerization of

vinyl chlorideVinyl chloride II BT2 A 2

2 Centrifugation, drying

Polyvinyl chloride C

3 Packing Polyvinyl chloride C 23(III) High Pressure

Polyethylene 1 Compression Ethylene II BT3 A 22 Preparation of catalyst Catalyst, white oil II AT3 A 23 Polymerization Ethylene II BT3 A 24 Processing (extrusion

and pelleting)Polyethylene C 23

5 Blending Polyethylene C 236 Packaging &

intermediate storagePolyethylene C 23

(IV) Polypropylene1 Preparation of catalyst Titanium trichloride, aluminum

monochloro ethide, gasolineII AT3 A 2

2 Polymerization Propylene II AT3 A 23 Esterification,

scrubbing, filtering Gasoline, Polypropylene II AT3 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

4 Solvent recovery Gasoline II AT3 A 25 Pelleting and packing Polypropylene C 23(V) Polyvinyl Alcohol1 Synthesizing ethylene

acetateAcetylene, acetic acid, ethylene acetate

II CT2 A 2

2 Polymerization and recovery

Ethylene acetate, methanol, polyvinyl acetate

II AT2 A 2

3 Alcoholysis Polyvinyl acetate, methanol, polyvinyl alcohol

II AT3 A 23

4 Packaging and storage Polyvinyl alcohol C 235 Cleaning furnace with

liquid D

6 Refrigeration and air compressor room

E

(VI) Polyester1 Air compressor room Air E 2 Terephthalic acid Terephthalic acid, paraxylene II AT1 A 23 Digly-cidyl

terephthalateTerephthalic acid, methanol II AT1 A 2

4 Ester interchange Terephthalic acid dimethyl ester, ethanediol, methanol, terephthalic acid diethyl ester

II AT1 A 2

5 Terephthalic acid ethyl ester

Terephthalic acid dimethyl ester, ethanediol, methanol, poly terephthalic acid diethyl ester

C 23

6 Pelleting and packing Poly terephthalic acid diethyl ester

C 23

(VII) Lump Polystyrene 1 Polymerization Styrene II AT1 A 22 Pelleting and packing Polystyrene C 23(VIII) A-, B-, S- Plastics1 Polymerization Butadiene, styrene, acrylonitrile II AT3 A 22 Dehydration, pelleting

and packaging C 23

(IX) LP Polyethylene1 Preparation of catalyst Titanic chloride, gasoline II AT3 A 22 Polymerization Ethylene, gasoline II AT3 A 23 Esterification,

scrubbing and filteringGasoline, polyethylene II AT3 A 2

4 Drying and packaging Polyethylene C 23

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

5 Recovery Gasoline II AT3 A 2(X) Nylon 661 Cycohexanol

generated with hydrogenation of phenol

Phenol, Hydrogen, cyclohexanol II CT3 A 2

2 Adipic acid generated with oxidation of cyclohexanol

Cyclohexanol, adipic acid II AT3 B 2

3 Adipic dinitrile generated with ammonification and dehydration of adipic acid

Adipic acid, ammonia, adipic dinitrile

II AT1 B 2

4 Hexanedianmine generated with hydrogenation of adipic dinitrile

Adipic dinitrile, ammonia, hexanediamine

II CT1 A 2

5 Polymerization Adipic acid, hexanediamine C 236 Packaging Nylon 66 C 23

V. Inorganic Chemical Plant

(I) Synthetic ammonia, synthetic methanol

1 Desulfurization of natural gas and light oil, coke oven gas

Methane, ethane, propane, etc. II AT1 A 2

2 Steam reforming Hydrogen, CO, methane II CT1 A 23 Partial oxidation Hydrogen, CO, methane II CT1 A 24 Gas generation

(normal pressure, pressurized)

Hydrogen, CO, methane II CT1 A 2

5 Storage, drying, handling and crushing of coke

Coke and its dusts C 22

6 Preparation, crushing, screening, storage and handling of coal powder

Coke and its dusts B 11

7 CO removal Hydrogen, CO II CT1 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

8 CO2 removal Hydrogen II CT1 A 29 Preparation and

regeneration of copper liquid

Acetic acid II AT1 B 2

10 Treatment of coke oven gas

Hydrogen, CO, methane II CT1 A 2

11 Hydrogen separation and nitrogen scrubbing unit

Hydrogen, CO, methane II CT1 A 2

12 Hydrogen and nitrogen compression

Hydrogen, CO II CT1 A 2

13 Synthesis of ammonia and methanol

Hydrogen, CO II CT1 A 2

14 Refining of methanol

Methanol II AT2 A 2

15 Ammonia absorbed liquid, storage and bottling of ammonia

Ammonia II AT1 B 2

(II) Urea1 CO2 compression CO2 E 2 Pumps for synthesis

of urea, gas, ammonia and aminomethane

Hydrogen II AT1 B 2

3 Decomposition and absorption

Aminomethane II AT2 A 2

4 Evaporation, pelleting, handling and storing

Urea

5 Stripping of biurea reformed gas

Hydrogen, CO, ammonia II AT1 A 2

(III) Ammonium Acid Carbonate

1 Ammonia absorption and ammonia liquor tank

Ammonia II AT1 B 2

2 Carbonization of reformed gas, treated

Hydrogen, CO II CT1 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

ammonia3 Centrifugal

separation, drying, packaging and storage

Ammonium acid carbonate E

(IV) Nitric acid1 Air absorption and

filtering, compression

Air E

2 Contact oxidation (normal pressure and pressurized)

Ammonia, air II AT1 B 2

3 Normal pressure and pressurized absorption and tail gas treatment

Nitrogen oxide, nitric acid E

4 Fuming nitric acid absorption

Nitrogen oxide, nitric acid B

5 HP reactor section Nitrogen oxide, oxygen B 6 Concentrated

sulfuric acid extracted with magnesium nitrate method

Nitric acid E

7 To concentrate magnesium nitrate liquid by evaporation

Magnesium nitrate solution D

(V) Ammonium nitrate1 Neutralization Ammonia, nitric acid B 22 Crystallization by

evaporation, centrifugal separation, pelleting

Ammonium nitrate C

3 Drying, cooling-down, storing, handling and packaging

Ammonium nitrate E

(VI) Ammonium nitrite1 Crystallization by Sodium nitrite B

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

evaporation, separation, drying, packaging and storing

(VII) Air Separation Unit1 Air extraction,

filtering, compressing and cooling down

Air E

2 Air fraction column (the casing contains rare gas fraction column)

Oxygen, nitrogen, argon B

3 Rare gas extraction unit

4 Purification of argon (with hydrogen)

Hydrogen, oxygen, argon II CT1 A 2

5 Refining of krypton and xenon

Oxygen, nitrogen, krypton, xenon

C

6 Combination unit of air separation and nitrogen scrubbing

7 Scrubbing ammonia with purge gas of synthetic ammonia, argon extraction with drying liquefier

Hydrogen, nitrogen, ammonia, argon, methane

C

(IX) Combination alkali making

1 Salt bin and salt washing, compression of heavy alkali with CO2

Na CO2 E

2 Calcination Sodium carbonate D (X) Chlorine alkali 1 Salt storage and salt

water refining NaCl solution E

2 Electrolysis Hydrogen, Chlorine II CT1 A 23 Drying and Hydrogen II CT1 A 2

No. Description of Location

Description of Media Class & Group of

Media

Classification of Fire Hazard

Zone of Hazardous Location

compression of hydrogen

4 Drying and compression of chlorine, filling liquid bottles with chlorine.

Chlorine E

5 Evaporation Caustic soda E 6 Solid alkali Caustic soda E 7 Synthesis of

hydrogen chlorineHydrogen, chlorine, hydrogen chlorine

D

*Notes:

Hot oil pump building has an operation temperature of 200 oC ~ 400 oC much higher than the flash point temperature of diesel oil, therefore, it is classified as Zone 2 explosive hazardous location, however, its hazardous scope is relatively small and it is only limited to the space inside the pump building.

Most locations around open flames are also classified as Zone 2 explosive hazardous location, and only the spaces within a radius of 1.5M around open flames (furnaces or high temperature objects) are the non-explosive hazardous environment.

"Hazardous Location Zones" listed for various kinds of production units in the above table are only referred to the main areas and environments, among which partial or part of surroundings may be Zone 1 or Zone 0 and they shall be determined by the design personnel according to the actual requirements and conditions.

Annex II Classification and Grouping of Explosive Gas Mixtures

According to the provisions in National Standard GB3836.1, explosive gas mixtures shall be classified in accordance with the max. test safety interval and the min. ignition current, and grouped in accordance with the ignition temperature. See Attached Table 2-1 ~ Attached Table 2-3.

Classification According to Maximum Test Safety Interval (MESG)

Attached Table 2-1

Class Maximum Test Safety Interval (MESG, mm)

II A 0.9

II B 0.5 MESG 0.9

II B 0.5

Classification According to Minimum Ignition Current Ratio (MICR)

Attached Table 2-2

Class Minimum Ignition Current Ratio (MICR)

II A > 0.8

II B 0.45 MCR 0.8

II B < 0.45

Note: Minimum Ignition Current Ratio (MICR) is a ratio of the minimum ignition current value of various kinds of gases and vapors to the minimum current value of laboratory methane.

Grouping According to Ignition Temperature

Attached Table 2-3

Group Ignition Temperature

t (oC)

Group Ignition Temperature

t (oC)

T1 450 < t T4 135< t 200

T2 300 < t 450 T5 100 < t 135

T3 200 < t 300 T6 85 < t 100

Annex III Grouping of Dust Temperature and Classification and Identification of

Dust Explosion-proof Enclosures of Electrical Equipment

(I). Grouping of Dust Temperature

Dust is grouped into 3 groups according to its ignition temperature as shown below in Attached Table 3-1.

Grouping of Dust Ignition Temperature

Attached Table 3-1

Temperature Group Ignition Temperature T (oC)

T11 T > 270

T12 200 < T 270

T13 150 < T 200

Note: When grouping of dust temperature is determined, the smaller value of the ignition temperature value of dust cloud and the ignition temperature value of dust layer shall be taken.

(II). Classification and Identification of Dust Explosion-proof Enclosures of Electrical Equipment

Dust Explosion-proof enclosures of electrical equipment shall be classified as 2 classes in accordance with their capacities to limit dust entering into the equipment:

Dust-tight Enclosure: the protection class of the enclosure is IP6X, and identified as DT.

Dust-proof Enclosure: the protection class of the enclosure is IP5X, and identified as DP.

Annex IV Notes of Wording

It is required in this provision to define the wordings used to express the degrees of strictness. In implementation, deal with each case in accordance with the following statements of wordings:

(I). Wordings used to express requirements that must be very strictly followed without any deviation therefrom.

Wording in positive form to be used is "shall", and the equivalent expressions are "it is necessary (required to)…", " only … is permitted…".

Wording in negative form to be used is "shall not", and the equivalent expressions are " it is not allowed (permitted, acceptable or permissible)…".

(II). Wordings used to express something shall be done in this way under normal conditions.

Wording in positive form to be used is "shall".

Wording in negative form to be used is "shall not" or "is required to be not …", "it is not allowed (permitted, acceptable, permissible)…".

(III). Wordings used to expression the action steps are allowed with possibilities for selection or when the conditions are permissible it should be done first:

Wording in positive form to be used is "should" or "may", and the equivalent expression is "it is recommended that…".

Wording in negative form to be used is "should not", and the equivalent expression is "it is not recommended …".

SINOPEC STANDARD

Specifications for Design of Electrical Power

forProduction Plant

of Petrochemical Enterprises

SHJ38-91

Description of Specifications

1991 BEIJING

Chapter 1 General

Article 1.0.1 Based on relevant international and ministry level standards, this article is stipulated according to the requirements on the writing of scheme auditing, which are put forward in the Sinopec Electrical Center (88) Electric No. 2 document. The specifications are mainly applied to the design of electrical power for the newly building–up, rehabilitated and expanded projects of production plants and auxiliary facilities in large and medium petrochemical enterprises (including oil refineries, chemical plants and chemical fiber plants). For small plants, these specifications can be applied with most requirements less strict except that their load grading must be made according to relevant regulations.

In order to ensure a reliable power supply, not only the electricity consumption and load grading but also the capacity and the output value of the plant shall be considered in the design of production plant power supply.

The construction scale of oil refineries shall be classified according to their quantity of crude oil processed per year:

Large oil refinery: 2,500,000 tons or more;

Medium-sized oil refinery: over 500,000 tons but less than 2,500,000 tons;

Small oil refinery: lower than 500,000 tons.

The size of nitrogenous fertilizer plant:

Large nitrogenous fertilizer plant: annual synthetic ammonia output of more than 150,000 tons;

Medium-size nitrogenous fertilizer plant: 40,000 to 150,000 tons of annual synthetic ammonia output;

Small nitrogenous fertilizer plant: annual synthetic ammonia output of less than 40,000 tons.

There are a wide variety of petrochemical plants and they are in constant development and transformation, so at present there is no official document that can be used to define them accurately. The further definition of the sizes of these plants shall be made based on the information to be collected in the future.

Article 1.0.3 During the compilation of these specifications, national standards and relevant ministry-level standards were also being revised. In this case, there must have differences in some parts between them. When conflicts arise in actual operation, they shall be discussed and solved on the basis of coordination and mutual respect. At the same time, the characteristics of petrochemical plants and the guarantee of emergency power supply shall be considered under the condition that the construction progress is not affected.

Chapter 2 Load Grading and Power Supply Requirements

Section I Load Grading

Article 2.1.1 As for load grading, this article analyzes the stipulation in 2.0.1 of the national standard GBJ52-83 that electrical loads shall be classified as three grades according to their importance and the political impacts and economic losses that power failure brings about. At the same time it also considers the stipulation in 2.1 Specifications for Design of Power Supply for Chemical Enterprises CD90A5-85 that load grades shall be classified as emergency load, important load (important continuous chemical production load), secondarily important load (common continuous chemical production load). The general load grading method shall not only comply with the national standards as much as possible but also consider the high variations in complexities of chemical reactions of various production plants in petrochemical enterprises especially the special requirements for reliable power supply due to the existence of flammable, explosive and toxic matters in the production process. These specifications list separately Grade 0 load. In recent years, with the introduction of large and medium-size petrochemical plants, power supply design standards in foreign countries urge us to conduct useful studies on the grading of electrical loads. In addition, according to the national standard GBJ52-83 3.0.1, electricity users in the following cases shall equip themselves with auxiliary power supply:

I. Auxiliary power supply shall be provided to ensure the first grade power consumption (refers to the uninterrupted power supply even when the whole system breaks down). In fact, the ideas of emergency load and emergency power supply had been put forward early in Iron and Steel Design Manual (Edition 1974). The manual also pointed out that emergency load refers to the situation of serious casualties and damages due to the abrupt power failure in Grade 1 load. Emergency power supply refers to the reliable power supply for the emergency use of emergency load in order to ensure the safe shutdown of the plant of the enterprise when the production power supply in the enterprise is abruptly failed. This emergency power supply shall have adequate independence in its geographic location and cable connection. Auxiliary power plant provided with low cycle stepout device shall be used as the power supply to high-capacity emergency load and diesel generator as the power supply to low-capacity emergency load. The idea of Grade 0 load in this article is also based on the above-mentioned production characteristics especially with the petrochemical plants so that it is easier to take corresponding measures to realize reliable power supply.

Article 2.1.2 If the power supply to Grade 0 load is abruptly failed , the consequences will be very serious and most dangerous. If flammable, explosive or toxic matters are involved in the chemical reactions, abrupt power failure may lead to sharp increase or decrease in reaction temperature and pressure and even explosion, fire or massive leakage of poisonous matters, which will cause casualties and serious damages. In order to prevent this kind of accident or carry out timely rescue activities in case of these accidents, the power supply to rescue equipment and apparatus needed to evacuate the people shall be classified as Grade 0 load.

The purpose of setting up Grade 0 load is to prevent accidents and realize safe shutdown. Therefore, emergency load shall be stipulated on the basis of switching off the sources of chemical reaction materials, stopping chemical reactions and ensuring the safe operation of large and critical production units.

Another purpose of Grade 0 load is to facilitate quick salvage of equipment and personnel evacuation in case of an accident and stipulate the level of emergency loads on this ground.

There are countless kinds of petrochemical production units. These specifications only give a partial list of Grade 0 load equipment, which is to be supplemented in actual production practices.

Article 2.1.3 - 2.1.5 When deciding Grade 1 and Grade 2 loads in continuous petrochemical production, it should be emphasized that the whole petrochemical production process shall be regarded as the main starting point but shall not be based on the characteristics, functions and capacity of a single machine. We can find the definite dividing lines of continuous production loads between production units of different functions. Abrupt power failure in petrochemical raw material production units will mainly lead to the break of chemical reactions and production chaos, which in turn causes reduction in output and even the shutdown of the whole plant. Although it won’t cause casualties or serious damages of critical units, it takes time to resume production resulting in great economic losses. Therefore, these important kinds of continuous chemical production load shall be classified as Grade 1 load. As for power failure in petrochemical product processing units, it will not take a long time to resume production and the economic losses are low. So we list the load for this ordinary continuous petrochemical production as Grade 2 load, and this is the same case with small electricity-consuming petrochemical units. However, in small refineries, power failure may cause explosion and fire hazards, so individual or some electricity-consuming units shall still be listed as in Grade 0 or Grade 1 load. Loads other than Grade 0, 1, and 2 will be classified as Grade 3 loads.

Section II Power Supply Requirements for Various Load Grades

Article 2.2.1 The actual operations of petrochemical production units in recent years prove that the power supply mode of two loops connected from the network plus BZT cannot satisfy the requirements of Grade 0 load for the reliability and the continuity of the power supply. In the 13 large-scale synthetic ammonia (300,000 tons/year) plants imported from the foreign countries in 1970s, the dual-loop power supply mode is most common. According to the accident statistics between May 1976 and May 1980, there are 33 plant-wide power failure accidents in total. Moreover, several other large-scale petrochemical plants also have dual-loop power mains and their own auxiliary thermal power plants, such as Shanghai Petrochemical Plant, Yanshan Petrochemical Plant, Qilu Petrochemical Plant, and Sichuan Vinylon Plant etc. According to the statistics made since 1974, altogether 18 plant-wide power failures happened in these plants. In the above-mentioned 51 plant-wide power failure accidents, over 50% are caused directly by internal failures in the enterprises. However, there are also many accidents caused by the failures on power grid Three plant-wide power failure accidents in Shanghai Petrochemical Plant were all resulted from its internal failures. Among the ten plant-wide power failures happened in Sichuan Chemical Plant between 1974 and 1979, nine were resulted from the power grid failures, in which two were caused by power grid breakdown. As the regional main grid is parallel in its main network voltages, petrochemical works cannot obtain in a strict sense two independent power supplies no matter how many loops they draw from the grid. Therefore, any power grid malfunctions may lead to the power failures in all loops connected to the production plants and result in power failure accidents. When the auxiliary power plants are provided, low cycle stepout measures are taken to increase the reliability of power supply for the production plants. However, the operation experiences show that the plant-wide power failure accidents can not be completely prevented. In the three power failure accidents happened in Shanghai Petrochemical Plant, internal failures mixed with the operation conditions at the time and the malfunction of relay protection, in the

end neither internal auxiliary power supply nor external power supply from the grid can supply power for the loads. It is a problem that can be resolved by the low cycle stepout devices. So, we think that normally the auxiliary power plants that run in parallel with the power grid should not be used as the emergency power supply. That’s why the article here regulates that the power for Grade 0 loads shall be supplied by independent (independent in the sense of its geographic location, energy sources and water sources etc.) emergency power supply system.

Article 2.2.2 In the course of production, the processes that needs emergency protection measures which can be achieved through technological means shall not adopt electrical protection measures. Grade 0 loads shall be strictly controlled for the equipment.

Article 2.2.3 It is stipulated in U.S. National Electrical Code (NEC) Section 700: the emergency power supply systems shall consist of one or more than one of the following units: ① batteries; ② automatically starting-up generator system; ③ dual overhead/buried power lines that are in strict separation from each other geographically and electrically according to the regulations, which shall minimize the probability of power failure in both lines; ④ power line connections at the power supply side of the circuit breakers that can effectively isolate the faults happened within a building or a group of buildings, but this measure shall be used in combination with one of the above-mentioned three items.

The “strict separation … geographically and electrically” mentioned in item ③ actually refers to two independent power supplies in a strict sense as we usually say. This situation only exists in the few power plants such as Cangzhou Power Plant or remote areas. Generally speaking, most large systems are in parallel operation. The above-mentioned item ④ can serve as emergency power supply only when the failure is occurred internally and external power supply is guaranteed. Long years of experiences show that it is impossible to limit the electrical failures to a certain scope. Meanwhile power supply departments have never promised that no failure will happen to their supply service. So, the special lines defined in item ④ shall not be used as safety supply by itself. It shall be used in combination with the former three items. To sum up, we can say that emergency power supplies are referred to as the power supplies electrically independent from the power grid.

In Japanese fire control codes and construction codes, the emergency power supply is defined as follows: ① self-contained power supply; ② external power supply. In Japanese regulations, emergency power supplies mainly refer to batteries (including UPS) and diesel generators and other independent power supplies.

Article 2.2.5 For grade 1 loads, single loop power supply mode is not considered. Experiences in every petrochemical plant have proved that single power supply mode is not good for the long and continuous production of the plant. Thus, in this article it is stipulated that dual power supplies are required for grade 1 loads and the specific requirements for the dual power supplies are also made.

Chapter III Automatic Switching-over of Power Supply and Motor Restart System

Section 1 Automatic Switching-over of Power Supply

Article 3.1.1 The purposes for providing automatic switching-over deveices

Article 3.1.2 The installation location of the automatic power switching-over device is stipulated according to the accident probability of production units’ power supply system. The main purposes of the stipulation is to reduce as much as possible the stages and the activation time of the automatic power switching-over systems on the condition that the power supply reliability is not affected, so as to ensure the restarting up of motors.

Article 3.1.3 Wiring requirements for automatic power switching-over systems are made according to the national standard Code for Design of Relay Protection and Automation Devices in Industrial and Civil Electrical Installations and References of Electrical Power Design for Iron and Steel Works and in combination of the characteristics of power supply and distribution for production units.

Article 3.1.4 This article is set to prevent this situation: due to the insufficient overload capacity of the auxiliary power supply or failure to guarantee the motor restart conditions, bus line voltage is lower than the allowable limit after the successful automatic power switching over and the fault makes the whole restart action fail. In this case, the originally normal bus voltage is dragged down and the accident is in turn expanded to a larger scale.

Article 3.1.5 It stipulates the optional matching conditions for automatic power switching0-over devices and relay protection according to the structural characteristics of production unit power supply and distribution.

II. When feeder does not install reactors, it can only depend on start time limit to match the protection time limit in order to prevent itself from activating before the isolation of faulty units.

III. It must be guaranteed that only after the motors that are not allowed to start again are disconnected can standby power supply be activated.

IV. In order to prevent the surge of asynchronism, the start time limit of automatic power switching-over devices shall be higher than the under-voltage protection time limit of synchronous motors.

Article 3.1.6 The general conditions for the optional matches between automatic power switching-over devices are stipulated.

Article 3.1.7 The high-voltage power lines in petrochemical plants are usually overhead lines with considerable lengths. The probability of overhead line non-stability is high, especially in areas frequented by thunderbolts. So it is necessary to install the automatic reclosing devices at the power supply side of the connection. For the purpose of enhancing the rate of successful reclosing act, the existing power systems incline to increase the reclosing time. In some areas, the time is increased to 1.2 seconds. In this case the start time of the automatic power switching-over devices is prolonged and it will affect the restart-up of motors. Therefore, some regulations are stipulated here to solve the problem.

I. Reduce the stages of automatic power switching-over devices. The units shall be arranged according to the accident rate of the power supply and distribution network and the on the basis of not affecting the reliability of power supply. Item 3.1.2 has taken this factor into account.

II. Reduce the time of protection. This measure is quite beneficial when the conditions are available. However, it is not easy to do so when the power supply and distribution network has its own structural peculiarities. The reduction shall be made on the basis of optional matching. For example, the time of relay protection acts at both ends of a line can be the same.

III. As for the automatic power switching-over devices with current lockout, its start time shall be coordinated with the protection timing of the relay protection devices and automatic devices of the upper stage instead of the protection timing of the feeder line from the distribution substation. When the production process requires quick restart, it is possible for automatic power switching-over unit not to coordinate with the upper-stage relay protection and automatic device feeder lines.

Section 2 Motor Restart System

Article 3.2.1 The scope of motor restart system shall be defined.

Article 3.2.2 Motor restart mode shall be arranged using one or more restart modes listed here in this article according to the actual conditions in the project engineering.

Real crossover restart is good in some imported production units, but it needs DC control power supply, DC contactors, etc., and it brings no special advantages for the restart. So, in normal cases, crossover-like or time-lapse restart is enough to satisfy the requirements.

Article 3.2.3 The restart methods for high and low voltage asynchronous motors listed in this article are the most commonly used methods in production and can be used according to the specific conditions of the project engineering.

Of course, the new advanced restart methods in some recently imported units can also be applied and popularized, but they are not listed in this article since it is difficult to manufacture them domestically.

Article 3.2.4 Item I, II and IV are extracted from the chemical design specifications, Specifications for Design of Electric Power for Nitrogen Fertilizer Factories 12.2.3.

I. 1．Restart load current shall not exceed the calculated peak value allowed in the external power supply loop, so that the restart of motor groups will not lead to current fluctuation in the power grid and there is no need to ask the power dispatcher to permit the restart. If the peak current of the restart will exceed the calculated maximum value, it needs to discuss with power supply departments before the restart.

2． Overload multiplication factor of workshop transformers is determined by the bus line voltage drop requirements in the course of restart. If the multiplication factor is set at 2, for the workshop transformer with rated capacity lower than 1000kVA and the secondary voltage of 400／230V, when its impedance voltage is lower than 5.5％, the bus line voltage 0.9UH can be ensured in the course of restart.

3． When mortor is restarted up, the restart peak current shall not exceed 1.1 times the rated current of the emergency generator. This is a rule stipulated in International Technical Conditions for Diesel Generators (Verified Draft).

II. As one of the basis performances of squirrel cage motors is that the motor shaft torque is in direct ratio with the square of the supply voltage, the motors will absorb high current from the power system when they are restarted in groups and thus the bus line voltage and the corresponding motor terminal voltage will decrease. As a result, the shaft torque of the motor will also be lowered. Moreover, the restart is made at load. In some cases, restart is a bit more difficult than a normal start, so the decrease of shaft torque shall be considered and it shall be checked that the shaft torque of restarting motors must be higher than the drag torque of the corresponding mechanical rotating speed.

As for general purpose centrifugal pumps, the excess torque is relatively high between the motor shaft torque and the pump’s drag torque, so voltage drops will not bring any difficulty to the restart of this kind of motors. However, for the restart of motors that drive some hard loads, the conditions shall be checked in detail. If the restart is difficult, the dimension of the driving motors can be increased a little so as to increase the excess torque for a successful restart.

III. This item is stipulated on the basis of the Electrical Power Ministry standard Specifications for Design of House Load in Thermal Power Plant DLGJ17-D81 Article 49 and the characteristics of petrochemical enterprises.

IV. Restarts are almost always occurred under hot conditions. Each restarting motor will respectively absorb restart current close to the start current from the power supply and at the same time these restarts are all made at load. Therefore, in the design of restart circuits, the heating of motor windings in the restart process shall be checked..

Only four major conditions necessary for restart are listed, and the other conditions, such as the general time limit of restart and the prevention of residual voltage impact in the instant of restart, will be discussed in other articles.

Article 3.2.5

II. The purpose of this rule is to regard the restart current as a possible maximum short time overcurrent, so that the overcurrent protection meter with time limit in the feeder line and the effect of the current will not activate the misoperation of overcurrent protection in the restart.

III. As stipulated in this article that it is better to arrange the real crossover restart at the time when residual voltage is lower than 40% of the rated voltage, because the vectors and the values of residual voltage and supply voltage in the course of motor restart are the two major parameters that effect the asynchronous surge. When the two have relatively high absolute values but small phase-angle difference (as soon as the motor power is just failed and the motor starts inertial rotation, its phase angle is not in time for increasing), or when the phase difference between the two reaches its maximum value but the absolute value of residual voltage reduces to a low level, the asynchronous surge for the motor restart can be avoided.

In the power supply system of the existing production units, it is difficult to apply the former solution because of some coordination problems between relay protection devices and the timing problem in on and off actions of the switching-over. Therefore, the latter one is extensively used in the restart circuit design. For motors in

normal operation, in case the power goes off, we shall not resume the power immediately. Only when the feedback voltage is lowered to the permissible value as the magnetic field of the rotor weakens can we resume the power supply and realize the restart.

According to the experiment data of a project in China, when 6KV bus line is in operation with load, the waiting time (when residual voltage lowers to 35%UH) between power cut off and restoration is about 0.7s - 1.5s. So, for real crossover restart, when necessary and possible, we can purposely add about 1s time lag in the automatic devices and set the time of motor restart to about 2s, so that high residual voltages can be avoided and the successful restart will be ensured. The increase in action time of the automatic devices will not affect the time for inactivating the faulty parts, so it will not affect the reliability of relay protection. Normally dual power supplies are used in the production units. Therefore the increase in the activating time of automatic device will not bring notable impacts upon the whole power system. In addition, we seldom meet cases of real crossover circuits, so it will not be a problem.

IV. Requirements for automatic devices: the time setting of automatic power switching-over devices shall get out as much as possible of the action time limit of the reclosing devices while the timing cannot be prolonged arbitrarily. If the requirements cannot be satisfied, see 3.1.7 for solutions.

3.2.6. For the smooth application of the various kinds of coordination listed in the article, the main steps of motor restart system design are listed below for readers’ reference.

I. The topic of restart shall be put forward by the process specialty, and the necessity and possibility for the restart shall be discussed jointly by the related specialties of electrical, process, automatic control, equipment, etc.

II. Accept and re-examine the restart requirements proposed by the process specialty:

1. The importance of loads driven by electric power (its importance concerning personal safety, production safety and continuity);

2. Requirements for restart sequences;

3. Requirements for restart timing;

4. Special requirements for the restart of some types of motors;

5. Specify the equipment which is not allowed to be restarted up.

III. Collect all the useful information concerning the severity and the occurring frequency of relevant power supply failures, including the information on the automatic devices of the system and whether some specific motors are allowed to be restarted in the system.

Collect as much as possible the properties of the motors that need restarting, the properties of driven equipment and the data of the system impedance.

IV. Design the power supply and distribution system according to the restart requirements and consider the installation of automatic devices and relay protection in the main bus connection.

V. Study the necessity for using real crossover restart and determine the mode of connection for the restart.

VI. Calculate the restart current and voltage of the motors and determine the sequence and the interval of the

restarts.

Article 3.2.7 Calculation of restart current

I. The motor start current only relates to the parameters of motor instead of the load. Load only affects the start time of motor and not the level of start current. During the motor restart, due to the inertia property of the motor and the interval of power cut off, the rotation speed of the motor cannot be zero (slip ratio S is not 1). In other words, the motor is actually restarted at a certain slip ratio. Here the start current of the motor is different from the value when the motor is directly started under full voltage. However, according to theoretical analyses and calculations and the data and curve obtained in the experiment on the motor’s inertia properties, the restart current will come close to the start current when the restart is done at the time that its rotation speed is reduced to 70-85% of its rated speed. Therefore, it is specified that the restart currents of medium and small capacity low-voltage squirrel-cage induction motors can be calculated on the basis of their start currents. For the convenience of calculation, the current is directly set to 6 times the rated current.

II. As for most high-voltage motors, their rotation inertia and the stored energy are high, so their inertia duration is relatively long and their speed reduction is slow. According to test data and inertia property curve, the equivalent restart current multiplication factor of high-voltage motors takes different values along with the different duration of power breaks.

Here we use the comprehensive equivalent start current multiplication factor to represent the start current. The effect of voltage drops on the start current during the starting is not considered, because the restart process is similar to the start process, both are very quick. Moreover, the effect of restart voltage drop on the restart current is quite complicated. There are many effecting factors and it is difficult to explain this with a universal formula.

In addition, different high-voltage motors have different start current multiplication factors and the differences are so big as ranging from 4.4 - 7.0. However, for most high-voltage motors, the current multiplication factors are lower than 6 or at about 6, so we set the multiplication factor of the equivalent restart current at 6. If we only calculate the restart current of one high-voltage motor, the multiplication factor shall take the specific value in the sample.

Article 3.2.8 Calculation of restart voltage

List the differences between the restart voltage calculation and the calculation of ordinary motor start voltage and the precautions to be taken.

Article 3.2.9 All or most motors of the whole workshop are require to be restarted up since there are strict requirements for the production continuity and importance of process and the safety and reliability of the power system . However, as restricted by several factors of voltage, current for restart up, it is not practical to make all or most motors on a main bus line restarted simultaneously in a short time after the disappearance of main bus voltage and the restoration of power supply. In this case it is necessary to restart the motors step by step in batches.

In project engineering, the capacity limit for restart shall be decided by calculating the restart voltage, and then batches for restart shall be set. This article suggests determining the batches of motor restarts according to the ratio between the rated capacity of the motors to be restarted and the rated capacity of the transformer.

In the present-day project engineering, the load factor of transformers has been set relatively low (about 50%) in order to increase the capacity limits of the first batch of motors to be restarted. If it still won’t work, we can further reduce the UK value of the transformers and then implement the restarting in batches.

Article 3.2.10 In determining the intervals between the time-lapse restart of each motor group, we have consulted the actual timing of some recently imported equipment and the design values in some domestic projects. The interval values here have been proven feasible in actual practices. For those special motors, its restart timing will be determined according to its special requirements for the restart.

Article 3.2.11 This article is stipulated on the basis of the chemical engineering specifications for Design of Electrical Power of Nitrogen Fertilizer Plants 12.2.4 and 12.2.5, and the characteristics of petrochemical production units.

Chapter 4 Explosion and Fire Hazard Environment

Section I General

Article 4.1.1 The issue discussed here is a common question stressed by similar specifications in many countries such as U.S. and Japan. We shall regard the regulations here as guidelines in our work instead of unalterable dogmas.

Relevant stipulations in national industrial standards and specifications shall also be observed during the implementation of these specifications. If the regulation here conflicts with higher level specifications, the higher level specifications will prevail.

Article 4.1.2 The purpose of this article is to draw the attention of designers. In the industry of explosion-proof products, it is forbidden to produce and sell the explosion-proof electric products that are not certified by the relevant national authorities.

Section II Classification of Gas or Vapor Explosion Hazard Zones

Article 4.2.3 Previously the measures to prevent explosion hazard were neglected by most manufacturers. They did not seriously think about the problems in their actual work. The precautions mentioned here are comprehensive measures taken before the implementation of electrical measures in aspects of production process, open-air installations, safety interlocking, nitrogen protection, ventilation, etc.

Article 4.2.4 “Release source” is an important concept and it is a major element for dividing the hazard zones. Before the classification of hazard zones, the first thing to be considered is the grading of relevant relief sources.

Article 4.2.5 Classification of explosion hazard zones

For correct classification of the hazardous environment, refer to the following steps:

I. It is required in the following steps to give the answers to a series of questions. The positive answer to any of the questions will confirm the existence of an environmental zone. The boundary limits of the environment can be defined according to Figures 4.3.1—1 to 4.3.1—9. When the zones are determined, the considerations shall be made to each room, location or area respectively.

II. The necessity of the classification:

Positive answer to any of the following questions verifies that it is necessary to make the classification of zones.

1. Do flammable liquids or gases tend to exist?

2．Is it possible that flammable liquid with flash point 45℃ will be transferred, processed or stored at the temperature higher than its flash point?

III. Second step of classification of environmental zones

Provided that there is positive answer in the first step, the following questions will be used in classifying the zones.

1．Positive answer to any of the following questions will lead to the conclusion that it is zone 1 environment:

(1) Does critical concentrations of flammable gases tend to occur in the air under conditions of normal operations?

(2) Does the critical concentration of flammable air mixture tend to occur frequently as a result of maintenance, repair or leaking?

(3) Will processing, storage or faults of other units tend to lead to faults of electrical systems and the discharge of flammable liquids or gases?

(4) Is the pipeline system for flammable liquids or gases arranged in poorly ventilated environments? Is the pipeline system (including valves, instruments or piping fastened by bolts or flanges) in bad conditions of maintenance?

(5) Are there some low places where flammable gases or liquids tend to accumulate?

2．Positive answer to any of the following questions will lead to the conclusion that it is Zone 2 environment:

(1) Does the pipeline system for flammable liquids or gases locate in poorly ventilated environments? Is the piping system (including valves, instruments or pipes fastened by bolts or flanges) in good conditions of maintenance ?

(2) As for production units containing flammable liquids or gases in well-ventilated environments (except those pipeline systems that are in good conditions of maintenance), will liquids and gases leak from potential discharge sources such as pump seals, vent holes or venting valves, sampling points, discharge openings because of abnormal operation conditions?

(3) Is the location adjacent to Zone 1 environment? Can flammable gases infiltrate into the location through trenches, pipelines or protective conduits?

(4) If positive-pressure mechanical ventilation is applied, will the faults or abnormal operation of ventilation equipment result in the formation of flammable vapor mixtures in the air?

Article 4.2.6 In actual designs, we often see that non-explosion hazard zones are classified as explosion hazard zones, for example, the lab for water-cooling tower. The reason is that the designer does not calculate whether the maximum volume concentration of flammable matters that can be possibly formed will exceed 10% the lower limit value of explosion, especially under the conditions of good mechanical ventilation or natural ventilation.

Two points will be specially stressed here. First, the classification of zones for water-cooling towers. Here in this article, it is regarded as non-explosion hazard zone. The flammable liquid or gas contained in circulation are from the process equipment leak. Usually the leak is not in a large volume even in abnormal production conditions. Furthermore, the amount of circulating water is usually very high and the percentage of flammable matters in water is a trace. Moreover, the cooling tower is set up in open air and there are force fans that can quickly blow away the flammable matters. So the flammable matters will not build up to a concentration 10% higher than the lower limit value of explosion. Years of practical experiences also prove that it is not necessary to make the classification of zones for the cooling tower unit.

Second, regarding the classification of areas where there are units applying open flame or red-hot parts. Both the domestic and foreign standards stipulate that there is no need to classifying the areas. The problem is that there is no definition of the limits for the area that requires no classification. It is specified in this article that the limits are 1.5 meters. Seen from the perspectives of heat radiation and gas flowing, the distance is small and relatively appropriate and can be regarded as a reference in actual design.

Article 4.2.7 - 4.2.9 Ventilation is an important element for the classification of explosion hazard zones. Here the issue is described in detail so that the measure can be correctly understood and applied in the actual design. Although mechanical ventilation is an effective method in reducing the hazards in an environment, it shall not be applied unless in special conditions or unavoidable situations. Normally in most cases production units will be arranged in open-air or half-open-air environments and natural ventilation is used to reduce the hazards for the environmental zones..

For petrochemical production units, the open air or the open arrangement has the following advantages:

1. It is the most convenient and the simplest way to achieve good ventilation. However, we have to consider the environment, terrain and installation location around the unit and analyze whether the expected effects can be achieved.

2. Compared with enclosed buildings, it can reduce the explosion hazards and alleviate the consequences of explosions.

3. It will save the expenses of mechanical ventilation system (including the standby system), the cost for civil construction and operations.

Section III Scopes of Gas or Vapor Hazard Zone

Article 4.3.1 This article is an excerpts from relevant API 一 500A regulations. It helps us understand the characteristics of different materials and decide the range of hazard zones. Its appendix provides descriptions of

the nature of flammable gases and liquids and the knowledge is highly useful in our actual work.

Article 4.3.2 Plenum is a safety measure that we have take when we have no other choices. The regulations and requirement on plenums will help us use them correctly.

Article 4.3.3 When the volume, pressure and flow rate of flammable liquid is controlled within the levels stipulated in the article, the amount and the possibility of its leak is low and thus the scope of hazard zone is small. Moreover, as the installation is set under open-air or half-open-air conditions, good natural ventilation will also help reduce the scope of hazard zone.

Section IV Electrical Installations in Gas or Vapor Explosion Hazard Environment

Article 4.4.2 Table 4.4.2 gathers the explosion-proof structures of motors, transformers, electric apparatuses, lamp fixtures and instruments to facilitate the application of users.

The use of sparkless motors in Zone 2 environment has been emphasized on in this article, because sparkless motors have been extensively used in imported plants and in foreign countries (in foreign countries it is actually totally-enclosed industrial induction motor), and are now in good operation. It is economically significant that sparkless motors are used in Zone 2 environments. Theories and practices also prove that the use is safe and reliable and there should not be any worries and other psychological blocks.

Article 4.4.3 Anti-explosion labeling is a safety item in the engineering and production management. However, few people come to understand its importance. This article makes a detailed explanation about the labeling.

Article 4.4.5 To ensure safety in hazard zones, it is necessary to use copper core cables and wires. It is safer and more economical than the aimless use of explosion-proof or positive-pressure-ventilated motors.

Moreover, we shall pay attention to the overall safety of electrical anti-explosion arrangements. This is an important concept. We think that we shall solve the following problems in order to improve the overall safety of electrical anti-explosion arrangements:

1．Overall and long-term safety must be maintained during the course of design, installation, operation and maintenance. It requires not only the complete procedures but also the strict management made by qualified personnel.

2．Engineering design lacks the coordinated overall safety between different specialties. For example, in some specialties, some safety measures are not proper, not complete, or lack of coordination with other measures in other specialties.

3. Overall electrical safety is not coordinated for all the parts or links of this specialty. As for the electrical specialty there are some points to be noted as follows:

(1) The safety measures taken in the power design are to the high requirements while the safety measures for lighting design are to the relatively low requirements. For example, in Zone 2, 2.5mm2 aluminum wires are used for lighting circuits while power cables must be 4mm2 or higher. Another example: branches and joints in lighting circuits are seen everywhere while no joint is allowed for power cables (in fact, joints are unavoidable in places such as motor terminal boxes). This is not so appropriate.

(2) If higher explosion proof grades are adopted for the motors while the aluminum-core wires are used, the overall safety level will be relatively low.

(3) Temperature increase curve of increased-safety motors does not match up with the behaviors of overload protection thermal relay.

Article 4.4.10 In explosionhazard environment, special copper conductor shall be used for the protective earth wire (PE) for the electrical equipment housings so as to ensure that single phase earthing failure will be cut-off.

Section V Dust Explosion Hazard Environment

Article 4.5.1 Types of Dust Explosion Hazard Medium

According to their characteristics and degrees of danger, there are three kinds of dust explosion hazard mediums: explosive dust, flammable conductive dust, and flammable nonconductive dust. Explosive dust is a kind of dust that is flammable in the air that is lack of oxygen or even in carbon dioxide and it can explode terribly when in the suspending state. Aluminum catalyst is usually used in chemical production. The catalyst is made from aluminum powder, which is a kind of explosive dust.

Flammable dust is the dust that can react with oxygen in the air and let out heat that eventually leads to burning. Flammable dust is less dangerous than explosive dust. According to their different natures, flammable dust falls into two kinds - flammable conductive dust and flammable nonconductive dust. For electrical units, flammable conductive dust is more dangerous than flammable nonconductive dust. As for flammable dust dangers induced by the dangerously high temperature and the electric sparks of the electrical equipment, conductive dust is more dangerous than nonconductive dust.

Article 4.5.2 The fundamental solutions to the dust explosion problem is to take precautions against it. Great importance shall be attached to these precautions.

It is described in these specifications that the measures mechanical ventilation shall be used for the precautions against Different countries have different descriptions about the measure. For example, in the Australian specifications the Classification of Hazard Zones, Part II Dust (AS2430 Part II —1981), it says: …… dust is different from gas. Excessive ventilation is not always appropriate, because accelerated ventilation may lead to the formation of suspending dusts, which means greater instead of smaller dangers…… It is stressed in these specifications to use mechanical ventilation to prevent the formation of suspending dusts. In the process of production, ventilation facilities will be carried over the dusts leaking from containers or equipment into a dust collector, as a result, raw material loss will be reduced and so will the danger lying in the production site. It is not that simple kind of accelerated ventilation, which makes dusts suspending in the air and increases degree of dangers.

Article 4.5.7 As suspending dust has a quite limited range of diffusion in the air and it is easy for it to be thinned out to under the lower explosion limit, the method of defining the ranges by rooms is adopted in this specification and no explosion hazard environments are defined outside the doors and windows of buildings.

Article 4.5.8 The main content of this article is the selection of electrical equipment. Though some countries (such as Japan and France) produce explosion-proof electric equipment that are specially used in dust explosion hazard environments, most countries use dust-proof and airtight electrical devices. Therefore, the dust-proof

and airtight electric equipment are included in the range of selection under this specification. The electrical equipment designed for gas or vapor explosion hazard environments can also be employed in environments with dust explosion hazards (the temperature grade of the equipment housing should be considered), but it is not cost effective and is not recommended.

Section VI Fire Hazard Environment

Article 4.6.1 Discrimination of the fire hazardous substance and explosion hazardous substance shall be paid attention to. Discrimination of some substances is easy in normal cases, but quite difficult in some other cases or should be handled cautiously. For example, in case of diesel oil with its operating temperature higher than its flash point or some kind of flammable dust with large particle size, the quantity, arrangement and environment (ventilation) conditions shall be taken into consideration and the practical experiences shall be based on for discrimination.

In such rare cases as with very large space of the location and small quantity of inflammable liquid, where the actual operation experience has proved that there are no explosion hazards, the hazard may also be defined as fire hazard.

Article 4.6.2 As for zoning of fire hazard environment, the quantity and arrangement of flammable substances in the environment shall be first considered to decide whether occurrence of a fire disaster possible. If it is, the area may be defined as a fire hazard environment. It is not right to think that any area with flammable substances is certainly a fire hazard environment.

Chapter 5 Substation

Section I Site Selection

Article 5.1.2 It is defined that the power transmission and distribution unit shall be generally located outside the explosion hazardous area and specified at the same time, for the sake of safety, the requirements when it has to be located inside the hazardous area.

Section II Power Supply and Distribution System

The articles of this section are abstracted from or written by referring to the following Codes and Standards

I. Standards of Ministry of Water Conservancy and Electric Power Articles 2.1, 3.2 of SD126-84 “Tentative Regulations for Harmonic Management of Electric Power System”.

II. Standards of SINAPEC

Articles 3.3.6 of SHJ1066-84 “ Technical Specification for Power Design of Refineries”.

III. Design Standards for Chemical Engineering

1. Articles 3.1.11, 3.1.13, 3.1.15, 3.1.19, 3.2.1, 3.2.10, 3.2.12 and 3.4.1 of CD90A2-81 “Regulations for Design of Electric Power of Nitrogenous Fertilizer Plants”.

2. Articles 4.2.3 ~ 4.2.6, 4.3.2 and 4.3.3 of CD90A5-85 “Technical Specification for Design of Power Supply of Chemical Enterprises”.

Section 3 Operation Power SupplyArticle 5.3.1 The chrome-nickel battery has a number of advantages, of which, the main advantage is that it can ensure the reliable operation of the relay protection and automatic unit. Compared with the capacity energy-storage unit, not only can it reduce the maintenance time, but also simplify the wiring, thus it is recommended.

Article 5.3.2 AC operation is a method currently used. With present development, chrome-nickel battery can also be used if required by relay protection and automatic unit.

Section 4 6 ~ 10KV Main Electrical Equipment Selection

Article 5.4.2

I. Because of breaking capacity depending on voltage, for convenient usage and reducing the conversion calculation and unifying with the National Breaker Standard (GB1984-80), it is defined to use rated open current instead of rated breaking capacity.

Since most of the breakers are opened after 2~3 cycles, periodic component and non-periodic component of short-circuit current are all attenuated somewhat then, it is more practical to calibrate by short-circuit current of

the actual opening time. The short–circuit capacity of the power supply and distribution system of the industries and enterprises is not that large, for simplifying the calculation, the selection may be done based on the super-transition short-circuit current first. When not satisfied, then check against the previous conditions.

II. The new series products produced recently are all passed the open current test under specified cycle operation as per breaker standard and usually their breaking ability will not be reduced due to re-closing. However, some of the breakers are not up to the nameplate rated parameters because of the manufacturing quality, so care must be taken. Example: SN0-10 (G) can only be opened normally at the 30% opening capacity and become abnormal at 50%.

III. Rated closing current refers to the maximum current when breaker can close without resulting in contact fusing connection and obstructing continuous normal operation under defined conditions and is expressed in peak value. For closing current, manufacturer usually takes 2.5 times of the rated open current (1.8x2, where, 1.8 is the impact coefficient). Therefore, under normal conditions, when the open current can be passed through, its closing current can be passed through accordingly. However, the limited passing through current of SN0-10 breaker made by Beikaiyuan is 65KA and its closing current is only 59KA due to the mechanism, therefore, closing current should be calibrated.

IV. The problem is that there is no special breaker in our country applicable to the test condition. Although the performance of vacuum breaker is relatively complete, the dynamic and static contacts are usually contacted by flat pressing, which is the cause of over-voltage of capacitor bank re-closing and the problem of opening restrike can not be avoided completely. The theoretic analysis evidences that the re-closing over voltage will not be higher than 2Vex when placing the capacitor bank into service, but practice shows it is higher than this value. For 10KV vacuum breaker, it may reach the value of 2.73Vex, and over voltage of breaker cut-out restrike may reach 4.8Vex. Therefore over voltage protection must be taken. Zinc oxide lightning arrester is used in most time.

V. Restrike breakdown rate of the vacuum breaker is smaller and has a desired arc wiping performance with less maintenance time, and especially applicable to the frequent operation application.

Article 5.4.3

I. Capacitor may take high power grid voltage resulting from connecting to the power grid, high grid voltage resulting from high sub-harmonic wave, over voltage resulting from series reactor, high-operation-voltage resulting from light load etc. Thus the capacitor withstanding voltage limit is defined.

When capacitor is operation under over voltage, its performance and life will be affected due to its enhanced fluid field. When the voltage value and operation time exceeds its permitted value, capacitor fluid will be locally discharged which will lead to more hazards. Therefore when selecting the capacitor, its rated voltage must be slightly higher than the actual power grid voltage, but not much higher, otherwise the capacity of the capacitor will be remarkably reduced.

II. When any one of the parallel capacitors fails, rest of the capacitors of that fault section will release the stored-energy to the fault capacitor in the form of discharge. When its energy is more than the min. explosion energy of capacitor enclosure, the capacitor will explode. The min. explosion energy of the enclosure the capacitor can withstand will be increased with the increasing of the capacity. Therefore by selecting capacitor with larger capacity, not only the enclosure explosion possibility can be reduced, but also the space (cubicle

number), the installation and maintenance work can be reduced as well. Therefore, it is better to select the capacitors with larger single capacity with the precondition of closing to the calculation capacity and uniformly distributed among the three phases.

III. The discharge process of capacitor insulation film is relatively slow and the capacitor with larger capacity will be slower. To ensure the safety of personnel and equipment, the discharge process should be speeded if the manufacturing condition allowed. Therefore it is defined to use the capacitor of 100KVar and above.

Article 5.4.4

I. It is defined the principle of selecting the reactance value of series reactor to limit re-closing surge flow.

It is stipulated in the National Standard “Parallel Capacitor” that capacitor must be able to withstand the transition over-voltage of the first peak value which not exceeding the effective rated voltage of and 1/2 cycle of the duration. Over-voltage often occurs for the capacitor opening and closing by breaker, which is breakdown without force, at the time when it is closing. Its max peak value of transition over current is allowed to be 100 times of the rated current.

If high frequency surge flow passes through the smaller current transformer when placing breaker bank into service, due to the higher conductance of the primary winding of the current transformer, higher over-voltage

will occur during re-closing, which may breakdown the insulation of the primary winding of the current transformer. The similar accident happened before in the electric power sector and it was tried to connect LV

lightning arrester at both ends of the winding, as a result both were exploded. At present the only way to solve the problem is to limit the re-closing surge flow and increase the current transformer ratio.

It is also noted that the actual reactance value of the China made core reactor, under the action of re-closing surge flow and due to core saturation, is only 30%~60% of the rated reactance value. Therefore it is better to

select air reactor to obtain the desired limit property from the view of limiting the surge flow.

II. In order to make the capacitor circuit induce the comprehensive reactance of limited harmonic to avoid amplification of higher harmonic of capacitive reactance, the inductive reactance value of the reactor must meet XL>XC/n2(XC is the capacitive reactance of the capacitor bank), for the fifth harmonic, X L>XC/52 =0.04XC; for the third harmonic, XL>XC/32 =0.11XC . Therefore, in the actual application, to limit the fifth harmonic and the above, the selected reactance value should be 5%~6%XC; to limit the fifth harmonic and the above, the selected reactance value should be 12%~13%XC.

III. It is stipulated based on the capacitor acceptable long-time over-current and the saturation effect of the core reactor. 35% equivalent current of higher harmonic is included in 1.35 times of the rated current.

The series reactor should satisfy the dynamic stability when shorting and the thermal stability during shorting.

Article 5.4.5

I. In the past, porcelain insulation structures are often used and at present, epoxy cast insulation structures are used more. The volume of the later is smaller and light, which helps reduce the volume of the power distribution unit and have better basic stability. Since the heat radiation of the structure itself is not so good, the thermal stability will not be so stable, this should be decided based on the installation and operation conditions.

II. The current transformer, used as the neutral zero sequence protection of the transformer, its primary current is selected based on the transformer allowed unbalance current, the neutral current of yyno wiring transformer

shall not exceed 25% of the LV side rated current; there is no stipulation for dyn11 wiring transformer. The unbalance of transformer 3- phase AC depends on the unbalance of the 3-phase reactance. According to the stipulation of power transformer (GB 1094 ‥D71) the unbalance of the 3-phase DC resistance of the transformer winding, 630KVA and below will be line 2%, phase 4%; for all the other transformers, phase 2%, the unbalance of the 3-phase reactance will be 10%. The max unbalance of the reactance may reach up to 20%. The unbalance current of the transformer will be at about 20% if the effect of the unbalanced resistance is ignored. The analysis made by the electrical power department holds that since the system reactance is further greater than that of transformer, the unbalance of 3-phase current of the transformer shall be considered based on the reactance unbalance of the whole power grid. For the selection of the correct current transformer for the transformer neutral point, it should be decided according to the max zero sequence current of the transformer installation location.

III. Since the proportion of the primary ampere-turn ratio of the zero sequence current transformer is greater, its current and turns are not in the inverse proportion relationship and secondary winning turns cannot be established based on the current, therefore the rated transformer ratio of zero sequence current transformer has no actual sense. In actual application, it is difficult to calculate the primary star-up current of current transformer, the method often used is to obtain first the terminal voltage of the secondary winding of current transformer based on the selected relay operation current, then find out the protection sensibility using the curves provided by the manufacturer (i.e. primary start-up current).

Article 5.4.6

I. Oil-immersed type transformer is often used before and operation experience shows that it is reliable. In recent years, epoxy cast type potential transformers are used more often, the volume of which is smaller and light, but casting quality is not ensured. Air bubbles occurred in casting are harmful to safety operation because of the field concentration and too low free voltage, and explosion accident happened before due to this reason.

III. When it is necessary to prevent ferroresonance, resistor or bulb may be connected to the secondary opening triangle, 220V 220W bulb is suitable for 6~10KV potential transformer, or use resonance absorption instrument.

IV. When single phase is grounded for neutral point direct grounding system, non-grounding phase is still the phase voltage and the voltage at the opening voltage of the third wing of the transformer is 100V. When single phase is grounded for neutral point non-direct grounding system, non-fault phase voltage of the primary winding of the transformer increases times and the opening voltage of the third winding of the transformer increases 3 times. To ensure the opening triangle voltage will be 100V, the third winding voltage must be 100/3V.

Article 5.4.7 Notes for parameter selection of metallic oxide lightning arrester are as follows:

I. Continuing operation voltage of the lightning arrester uby

Since there is no series gap in metallic oxide lightning arrester, its resistor disc will withstand power frequency phase voltage over a long period of time. To ensure its service life, the operation voltage applied over a long period of time to the arrester must not exceed the continuing operation voltage of the arrester. That is uby≥ukg.

Where: uby-----effective continuing operation voltage value of metallic oxide lightning arrester (KV);

ukg-----system max. phase voltage effective value (KV).

II. Rated voltage of the arrester ube

For the rated voltage of metallic oxide lightning arrester, the value, which is the same as arc suppression voltage of valve type arrester can be taken in general case. In addition to consider the amplitude of power frequency over voltage af the installation location, the duration of the over voltage has to be considered and its rated voltage should be selected by considering the initial energy of the arrester.

III. Through current capacity of the through current capacity metallic oxide lightning arrester indicates the ability valve block passing through impulse current and expressed in energized peak value under the defined wave shape and through-current times. After test, the change of valve block parameter shall not exceed the acceptable value. The follow current passed through by metallic oxide lightning arrester is very small, which can be ignored. Therefore, during actual application, only the energy of thunder and lightning over voltage and operation over voltage should be considered.

The calibrations of other parameters are similar to that of general valve type arrester.

Section V Arrangement of Power Transmission and Distribution Units.

Article 5.5.1

II. Lay stress on saving doesn’t mean ignoring the actual needs. Although substations are non-attended, if a maintenance room can be considered in the arrangement, it will be convenient not only for the substation’s maintenance work, but also provides a special maintenance area for the production.

III. Its self has greater heat productivity plus the sunlight on the west, making the temperature become higher, which will be liable to fire. During design, full consideration has to be taken to make good use of the favorable conditions to minimize its influence. However plane arrangement is limited by many factors, especially the petrochemical enterprises, which exists potential explosion hazard, so try to have a all round consideration.

IV. Specifically defines the requirements for the plane arrangement of the important control room.

V. Most of the substations use cable trench for wiring. As the scales of the units are getting larger, wiring by using cable room is getting more and more. Head room of 1.8m is decided based on the present project situation at home and abroad.

VI. Water induction of cable trench is more serious and popular for the substations with higher underground water level. For the substations with lower underground water level, due to raining water penetration during raining season and back flow of sewers, water flooding in cable trench also becomes popular. Even there is a case that the surface water sheet flood into the substation. Therefore, there is a requirement for the grade inside and outside the building.

Article 5.5.2.

IV. Although there is no great opportunity to have transformer damaged due to accident, the opportunity to lift the core to do some maintenance is not that less, e.g. oil leakage or penetration of cover and sleeve; loosing or heating of connection parts; loosing or vibration of fasteners; improper contact of the tap change etc. According

to the report from the site, there are very fewer of transformers to operate without core being lifted out every year. Some of them have their cores to be lifted out as many as 4~5 times, and to solve the problem at site when the problem occurs will cost a lot of time and the safety power supply will not be ensured. Some times, it is difficult to lift out the cores because of the insufficient clearance of the room. Therefore it is suggested to have lifting device at production site. In chemical enterprises, lifting device is not a problem, provided that there is a maintenance path for transformer in and out of the room, it will not be necessary to use core-lifting device. Therefore, the capacity of the core-lifting device should be considered based on core weight.

Article 5.3.3

I. It is defined not only the requirement for general arrangement, but also for special case for consulting.

II and III. Seeing from the past experience, it is often happened to have technical transformation and expansion to the production units after a period of operation time. Some of the units, which can be improved through technical transformation, have to be expanded due to less space reserved during design phase. Therefore, there is detailed requirement for space reservation for future use.

IV ~ VI. Integrated related standards at home and summarized the arrangement sizes, which are beneficial to normal maintenance and test.

VII. Outgoing and setting up conditions of power distribution system have directly impact on the personnel safety and maintenance work, so it is strictly stipulated in the articles, anyhow, there are still flexibility in application.

Section VI Related Requirements for Buildings

Article 5.6.1 During operation of the transmission and distribution units, they will be getting hot due to power losses, there must be good ventilation conditions for heat disperse. Rreports from production site show that under the same temperature condition, great temperature difference are observed owing to the housetop with or without heat insulation and the height of the house. For some of the LV power distribution room, their temperatures are above 40℃, some are as high as 45℃~46℃.

For some of the control rooms, sometimes it is impossible to avoid the sunlight on west. If curtains are used, the temperature inside the room will become high, the attendants will get upset; if they are not used, then control panels will be directly under the sunlight and have reflect light, which will not be good for panel minitoring.

In cold weather, owing to the poor heat insulation of the floor and roofing, roof will be condensed with freeze and forest or will have condensate dripping, which will be absolutely unsafe for power transmission and distribution equipment.

Article 5.6.2 General Requirements for Ground treatment Defined

Article 5.6.3 the wall of power distribution unit room in refineries were white washed before and looked nice. An incomplete investigation shows there is no accident caused by wall surface stripping, but such kind accident did happened in other department: over short circuit trip happened due to stripping off of the cement plaster of the rain shed of the secondary bus entrance of a general substation of a refinery. Therefore, it is defined that the

roof of power distribution room shall not be plastered.

Article 5.6.5 Lighting condition is directly related to ventilation condition. If natural lighting condition is not available, its ventilation condition will be poorer, which will not be good for equipment operation. Therefore, it is better to use natural lighting.

Article 5.6.6 In the past, water-proof of cable trenches was not be paid great attention to, especially, the bury points of cable supports and out connectors of cables, they were not plugged and treated for water-proof, thus causing sever water leakage and penetration.

Article 5.6.7 Conditions and requirements for HVAC defined.

Article 5.6.9 In the past, cement slabs were used for the cable trenches inside and outside room, but the ground become uneven due to poor construction quality, and there will be noise when people walking on them, and they are not convenient for maintenance work due to heavy cement slabs. But architectural view holds that steel plates will make the ground untidy and they cannot bear heavy weight. If construction quality is not ensured, it will make more noise, so high construction quality is essential. For the locations where plates have to be moved from time to time, (e.g. behind panels), checkered steel plates may be used.

Section VII Requirements for Fire Prevention

The problems raised in this section are only related to those liable to be over-sighted on fire prevention and the extent (strict or loose) on grasping the standards, and clarification has been made as well. Explanation is not necessary.

Chapter 6 Cable Selection and laying

Section I Cable Selection

Article 6.1.1 The selection of power cables for the petrochemical and chemical fiber project shall be in accordance with the load character, surrounding environment, laying method and cable property.

Article 6.1.2 The selection of material of power cables shall be in accordance with the load character and laying environmental conditions of cable lines. Since the copper core cable has higher current capacity and better flexibility, it is necessary to use copper core cable in the environment where frequent moving and sever vibration often occurs.

The coil material for increased safety and explosion proof type motor is copper, if aluminum core cable used, copper-aluminum transition measures or other measures shall be taken before cable connecting to motor terminal, thus there is an additional intermediate wiring; in addition, the wiring bell of explosion proof motor is smaller, it is difficult to lead the larger section cable to motor, but copper core cable can reduce the core wire broken problem, therefore, copper core cable shall be used for the cable lines in explosive hazardous environment of Zone 1 or Zone 10; and it is better to use copper core cable for the cable lines in explosive hazardous environment of Zone 2.

Article 6.1.3 For the selection of HV cable line, at present, it is selected based on the economic current density or the long-term acceptable cable current capacity. Since the existing data for the economic current density are 1950s’, not applicable now. In this article, it recommends to select the HV cable according to the long-term acceptable cable current capacity (all the factors included) and thermal stability, and calibration of voltage loss is also necessary.

For the selection of LV cable line sections, they must be selected based on the long-term acceptable cable current capacity (all the factors included) and calibration is also necessary.

Article 6.1.4 Cross-linked cable is a new type cable, which is made by modifying the molecular structure using chemical or physical method, i.e. to convert the thermoplastic polyethylene into thermoset cross-linked polyethylene to increase remarkably its thermo-mechanical property. This kind of cable has the advantages of simple structure, light in weight and no limitation for laying drop. However, the price of the cross-linked cable is more expensive.

The cross-linked polyethylene insulation cable has better cold withstanding characteristics, which can be used in the ambient temperature of –40℃. It is inadmissible to use polythene cable for the ambient temperature below –20℃.

To select the cable type has to follow the requirement of this article and take the consideration of local conditions during design.

Article 6.1.5 To select proper type of cables, according to different laying method and surrounding environmental conditions.

Article 6.1.6 This article refers to the stipulation made in “Technical Specification for Design of Cable Laying of Coal-fired Power Plant and Substation”, article 4 of SDJ 7‥D79 of the Ministry of Electrical Power.

Article 6.1.7 When the heat radiation conditions, where the cable passing through, is different, the cable

current capacity will be different. Take the section (no less than 10m) where the heat radiation condition is the worst as the basis when selecting cable, to ensure safety operation of cable.

Article 6.1.8 When laying cable line in the sand-filled cable trench, reduction of the comprehensive coefficient of long-term cable acceptable capacity is related to the soil thermo-resistance coefficient, multi-cable laying in parallel coefficient and temperature coefficient. Test conclusion has to be used for this data, however, this test has not carried out yet, and some of the design institutes attached to China Petrochemicals, Zhenghai Petrochemical Complex, Yangzi Petrochemicals were investigated when writing this standard and it is tentatively fixed at 0.5~0.6 and can be adjusted when the test data are available.

Table 6.1.8-1, 6.1.8-2, 6.1.8-3, 6.1.8-4 refer to Tables 3, 4, 5, 6 in Appendix 2 of “Operation Rules for Power Cables” of Ministry of Electrical Power.

Table 6.1.8-5 is abstracted from the test results jointly performed by Technical Center of Electrical Design of Ministry of Chemical Industry and Shanghai Cable Research Institute.

Table 6.1.8-6 is mainly abstracted from catalogues of cable manufacturer.

Section II General Requirements for Cable Laying

Article 6.2.1 This article is mainly to ensure safety operation of cable lines, avoid their damages by foreign force as less as possible, save investment and to be easy for maintenance and repair according to the characteristics of petrochemical and chemical fiber industries.

Article 6.2.2 The purpose of this article is mainly to protect the spreading of cable fire and the immersion of explosive gas mixtures.

Block tightly all the holes to prevent small animals and insects from entering into electrical room to avoid any heavy electrical accident, and the immersion or penetration of waste water and rain water outside the room, since the waste water produced by petrochemical and chemical fiber unit usually carries various kinds of chemical composition, which are corrosive to cable lines.

Article 6.2.3 Steel supports are usually used for cable supports. Galvanized steel supports may strengthen the anticorrosion property; for better anticorrosion property, applying anticorrosion paint and spreading plastic are admissible for chemical corrosion area, salt fog and humidity torrid zone.

Article 6.2.4 The cable acceptable min. bending radius data are summarized mainly based on the information provided by manufacturers.

Article 6.2.5 This article is abstracted from Article 6.5.11 of “Technical Specification for Power Design of Refineries”.

Section III Cable Laying Methods

Article 6.3.1 Cable open-laying shall be in conformity with the following:

I. Cable open-laying, the following methods are basically used.

II. This article refers to article 5.4.2 of “Code for Design of LV Power Distribution Units and lines” (GBJ‥D83).

III. This article refers to article 5.4.1 of “Code for Design of LV Power Distribution Units and lines” (GBJ‥D83).

IV. When cables are often exposed to the sunlight, outer sheath of the cables will absorb heat, which will increase the thermal resistance of outer medium and reduce the cable current capacity. Cables with rubber and plastic sleeve will be liable to aging under the direct sunlight and its service life will be shortened, therefore, shelter shall be installed when necessary.

V. This article refers to article 5.4.4 of “Code for Design of LV Power Distribution Units and lines” (GBJ‥D83).

VI. This article is abstracted from the fifth of article 6.5.10 of “Technical Specification for Power Design of Refineries” (SHJ1066‥D84) (Tentative).

Both insulation evaporation pipes and thermal pipes will disperse heat, therefore, there must be a certain distance between cable and thermal pipes and insulation pipes, and protect them from mechanical damage.

Article 6.3.2 Cables direct-bury shall be in conformity with the following requirements:

I. Cables laid in adjacent or parallel in the same route may subject to mechanical damage at the same time, or the adjacent cable will be effected due to one fault cable. To ensure safe power supply and reduce accident, the cables shall be laid separately or their parallel spaces shall be increased.

II. To ensure safe operation of the direct-buried cables, reduce mechanical damages, and locate the fault cable, reduce the accident correction time when there occurs fault cable, conditions for setting up cable line signs and laying spaces are defined.

III. This table is compiled based on the article 13.4.5 of “Technical Specification for Power Design of Plants” (JBJ6‥ D80), article 5.4.14 of “Code for Design of LV Power Distribution Units and Lines” (JBJ54‥D83), data of article 5.4.3 of chapter 11 of “Code for Installation Construction and Acceptance of Electrical Units”.

IV. The frozen soil in Northeast China some times reaches 1m or even over 2m in depth, it will be difficult to bury the cable below the frozen soil layer. Therefore, the bury depth has to be deeper according to local frozen soil depth, which shall be considered during design phase and proper measures have to be taken to protect the cables from damaged.

V. In the section where cables will pass through may exist various factors, which will damage the cables (e.g. chemical reaction, underground current, thermal impact, corrosion substances etc.). cable damages can be avoided if proper measures have been taken.

VI. Soft soil or sand layer will be laid around the cables to protect them from damaged.

Covered with concrete slabs or bricks to protect them from mechanical damage.

VII. This article is written by referring to note ⑥ of article 5.4.14 of “Code for Design of LV Power Distribution Units and Lines” (JBJ54‥D83).

VIII. This article is written by referring to note ④ of article 5.4.14 of “Code for Design of LV Power Distribution Units and Lines” (JBJ54‥D83).

IX. This article uses the data of article 5.3.1 of chapter 11 of “Code for Installation Construction and

Acceptance of Electrical Units” (JBJ232‥D82).

X. This article is written by referring to article 5.4.1 of “Code for Design of LV Power Distribution Units and Lines” (JBJ54‥D83).

Article 6.3.3 Cables laid in cable trench shall be in conformity with the following requirements:

I. Cable trenches shall be built by bricks, which will be simple in construction and less cost in investment. When underground water level higher than bottom of the trench, reinforced concrete structure will be preferred in order to prevent water penetration.

At present, cable trenches are built by bricks covered by reinforced concrete slabs and reinforcement measures will be taken only at the places where liable to subject heavy pressure.

II. The gaps of trench slabs are one of the causes of water penetrated into trenches. Therefore, seal requirements for slabs are put forward to avoid the entering of water, steam, oil, dusts etc.

III. water accumulation in cable trenches is very popular, on one hand, large amount of underground water or rain water penetrated due to high underground water level and improper water proof measures taken during construction; on the other hand, improper water discharge measures, especially during raining season, raining water back flow into the trenches to cause water flooding in trenches, resulting inconvenience for cable line operation, maintenance and repair.

IV. Different cover plates can be considered during design based on the local conditions. For the indoor cable trenches, which have to be opened frequently, light type plates, like checkered steel plates, can be used usually, for convenient line maintenance.

V. This article is written based on the sixth of article 5.4.7 of “Code for Design of LV Power Distribution and Lines” (GBJ54-83), data of article 4.0.3, chapter 11 of “Code for Installation Construction and Acceptance of Electrical Units” (GBJ232‥D82).

VI. This article refers to article 13.5.14 of “Technical Specification for Power Design of Plants” (GBJ6‥D80).

VII. Seal measures taken at the building entrances will prevent the entering of harmful gases into trenches, thus, prevent the development and spreading of an accident.

VIII. Power lines in the corrosion environment are usually open laid (e.g. laid in cable tray), and if laid in the trenches, they are liable to be corroded and flooded in the water, as a result, their service life shortened.

IX. For the sand-filled cable trenches used in explosive environment, trench type, depth, laying methods for different cables, arrangement, number of cable layers and distances are defined.

Article 6.3.4 Cables laid in cable trays shall be in conformity with the following requirements;

I. Cable trays are widely used in petrochemical enterprises for laying cables. In the engineering, it is better to make use of the floors of buildings and structures, walls, supports and hangers, process piping works etc, as the supports of the cable trays.

II. Base on the report of “Temperature Rising Calculation and Test Study under Transient State, Steady State and Periodic Load when Cable Bundles Laid in Cable Tray”, when cables laid in cable tray without space, its current capacity will be reduced in different extent, raceway reduces the most, tray the next and ladder the least.

Therefore specific conditions have to be considered during engineering.

III. When installed outdoors, protection covers have to be installed on the top of cable tray to protect the cables from the sunlight and welding slag and mechanical damage.

IV. The cables leading up and down the cable trays have to be run in protection conduit or enclosed support to protect them from mechanical damages.

V. Based on the report of “Temperature Rising Calculation and Test Study under Transient State, Steady State and Periodic Load when Cable Bundles Laid in Cable Tray”, when cables laid in cable tray without space, its current capacity will be reduced as the layers of cables laid in the cable tray increased. Therefore, when cable channel is commodious, no more than two layers of cables will be laid in each tray and three or four layers will be laid only when the cable channel is tight.

VI. The main purpose is to ensure safety power supply of the cable lines and to reduce accident impact.

VII. There are several anticorrosion treatment methods for cable trays, such as galvanizing, spreading paint, electrostatic spreading plastic zinc-nickel alloy electric plating etc., they will make cable trays have higher anticorrosion abilities under different service environment.

VIII. For future use (future construction of the project and newly built cable lines).

XI. When defining load of the cable trays, additional load (e.g. working personnel and maintenance tools etc.) has to be considered for installation and maintenance, in addition to the weight of cables laid and their accessories.

X. All the cable trays have to be grounded to form electric path and there must be reliable electric connections between cable trays and grounded as well.

Chapter 7 Motor and Lighting

The articles in this chapter are abstracted from or written by referring to the following codes and standards.

For the articles, which are fully applicable, they are basically the original articles. For the original, which includes the non-production units, only the applicable parts are maintained. Some of the articles are related to refinery units or chemical units, they were combined into one when writing.

I. Article 2.3.2 of “Code for Design of Electric Power Units of Industrial and Civil General Equipment”.

II. Articles 7.4.4, 7.4.6, 7.5.1, 7.5.3, 7.5.4, 7.5.5, 7.5.7, 7.6.1, 7.6.2, 7.6.3, 8.2.1, 8.2.2, 8.2.5, 8.2.7, 8.2.19 of “Technical Specification for Power Design of Refineries”

III. Articles 2.1, 2.4, 2.6, 2.7, 3.2.3, 3.2.7, 3.2.9, 3.2.10, 3.2.11, 5.1, 5.2, 6.1, 6.2, 6.3, 6.7, 6.9, 6.13, 7.2.7 of ‘Technical Specification for Lighting Design of Chemical Enterprises”.

IV. Articles of 12.1.12, 12.1.14, 12.1.17, 12.1.18, 12.1.2, 12.1.4, 12.1.8 of “Technical specification for Power Design of Nitrogenous Fertilizer Plants”.

V. No description for articles 7.2.6 and 7.6.3, they are the summaries of present design practice.

Appendix Natures of Inflammable Gases and Liquids

1.1 General

This appendix is abstracted from American API RP500A, which is helpful to have the knowledge of American explosion-proof specification, negotiate with foreign merchants and procure equipment etc.

1.1.1 Inflammable Mixtures

When inflammable gas mixed with air and there is firing source, whether the mixture will spread fire (explosion) will depend on the mixed proportion of the inflammable gas and air. If the mixture concentration is too high or too low, fire will not be spread through it. Thus, the minimum and maximum concentration of the inflammable mixture, which will spread fire in the air is referred to “inflammable (or explosion) limit”, they are usually expressed in volume %, which is the mixture in the air under normal atmosphere and temperature. The lowest limit for common inflammable liquids will be less than 1% (fuel oil of JP‥D6.1) and the highest inflammable limit will be 100% (acetylene, ethane oxide).

1.1.2 Inflammable Range

The concentration range of the inflammable gases in the air between the lowest and the highest is referred as “inflammable (explosion) range”. This range may be as narrow as 0.6%~3.7% (JR-6), or as wide as 2.5%~100% (acetylene). For general hydrocarbons, their inflammable range will be 1%~10%, but the inflammable range for hydrogen will be 4%~75%. Certain gas concentration may be higher than its highest inflammable limit. This cannot be hold that it will provide any extent of safety, because before concentration reaches its highest inflammable limit, it must pass through its inflammable range.

1.2 Grouping of inflammable air mixture in “National Electric Regulation”

The explosion-proof devices, which passed through the national explosion-proof inspection can only be used in the inflammable substances of specific class or group. Since the maximum explosion pressure and ignition temperature of the inflammables changes widely, “National Electric Regulation” groups the air mixtures based on their inflammable property. Some of the inflammables are grouped as the table below. For the inflammable substances list, see NFPA70.

1.3 Selecting electrical devices based on the nature of inflammable air environment

Based on the above grouping of the inflammable air mixtures, most of the inflammable environment of petrochemical plants belong to Group C and D. But acetylene production, hydrogenation, catalyst regeneration and other processes may cover their classes, especially Group B and C (equivalent to II Group C). According to the requirement of “National Electric Regulation”, when using explosion-proof type electrical devices, fittings and enclosures suitable for the specific air mixtures shall be selected. This is not requested for the electrical device types, such as increased safety, non-spark and positive pressure.

Classification and Grouping of Inflammable Gases and Steam

T. Group Ignition T.Grouping of Inflammable Gases and Steam

D C B A

T1 450 Steam, ethane, benzene naphtha, butane, propane, ethanol, methane, phenylethene, methylbenzene, dimethylbenzene, propylene, 1-propylalcohol, 2-propylalcohol, (n) pentane, 1-pentanol, methanol, acetone, propylene, nitril ammonia, ethylic acid (iso), butaester, butanol

Ethanal, acrylic alcohol, butyradehyde, CO, cyclopropane, butylene, diethyl ether, ethylene

Acryladehyde, arsenic compound (3), H2, H2, oxide ethylene, oxide propylene, product gas, H2 content more than 30%

acetylene

T2 300

T2A 280

T2B 260

T2C 230

T2D 215

T3 200

T3A 180

T3B 165

T3C 160

T4 135

T4A 120

T5 100

T6 85

Appendix Risks of Crude Oil Storage and Transportation and Safety Measures to be Taken

Several explosion accidents happened before in our country during crude oil storage and transportation and the after-effects were serious. This indicates that we did not fully understanding their risks. Many people hold that crude oil is black and thick, look like heavy oil, residual oil, which is not that dangerous, and not as dangerous as gasoline and light oil. In fact, crude oil components are very complicate, it has not only the light components like butane, propane or natural gasoline, but also the heavy components. In addition, the crude oil is always stored and delivered in the atmospheric pressure and unenclosed status in large quantity, this constitute more dangerous conditions than that of gasoline, light oil, even LPG.

We know from the three elements (e.g. flammables or inflammables, air and fire source), which constitute the explosion conditions that crude oil, during storage and transportation, has explosion hazards all the time (actually, belongs to Zone 0 environment). Since crude oil often directly exposed to air during storage and transportation, the top spaces of the storage tank and compartment are full of hazardous explosive gases formed by light component gases and air. If electrostatic sparks occur due to filling and vibration etc. explosion may happen.

Gasoline, light oil, LPG are explosive hazardous products. Usually, people know them and they are filled in pressure enclosed vessels when in storage and transportation, air cannot enter into the vessels. Even if there is little air in the vessel, gasoline or light oil is volatile under normal temperature and the mixtures in the top space of the vessel is often above the explosion high limit, there should be no explosion hazard. However, when the temperature is lower and volatile mixture less, the mixture in the top part of the vessel may be between the explosion high and low limits, therefore they are also hazardous.

Storage and transportation vessels under normal pressure are more hazardous than that under pressure, which is difficult to understand. It seems that the pressure vessel is liable to explosion, but that kind of accident, resulting from insufficient structure strength in design, is seldom to happen in fact. On the contrary, air cannot enter into the vessel and the explosive hazardous mixture cannot be formed because the vessel is pressurized. So the explosive hazard of pressure vessels are not as dangerous as that of normal pressure vessels. For the normal pressure vessels, although, there is no risk of explosion or cracking, air can enter into the vessel freely, explosive mixture will be formed on the top space of the vessel over a period of time, which is evidently dangerous. Some times, on the top space of the storage and transportation vessel of normal pressure, slightly vacuum pressure may be formed due to the changes of temperature etc., which will be liable to have air and fire entering into the vessel leading to ignition and explosion.

The crude hazard is related to the amount of light components and the temperature at which it is stored and transported. It will be more hazardous with more light components in crude oil and higher temperature and become less hazardous in the opposite conditions. In a word, it will be the most hazardous when temperature makes the volatile amount of light components of crude oil and the air mixture are just between the explosion high and low limit

For the above reasons, to prevent crude oil from explosion during storage and transportation, the following has to be observed:

1. The personnel at all levels working at crude oil storage and transportation system have to be made understood that crude oil is the most hazardous medium, especially made them understood in theory.

2. The personnel working at crude oil storage and transportation system have to be selected and trained both at quality and responsibility.

3. Work out and complete the operation and management rules and regulations for crude oil storage and transportation.

4. Try to fill fully the vessel or compartment and leave the top space as small as possible and fill the space with N2 to keep it in slightly positive pressure. Monitoring instruments and alarm devices are also requested.