oisd-std-173 draft

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OISD – STD – 173

Draft

FOR RESTRICTED CIRCULATION ONLY

OISD STANDARD - 173

FIRE PREVENTION AND PROTECTION SYSTEM FOR ELECTRICAL INSTALLATIONS

First Edition - July, 1998 1st Revision - Sept, 2003 2nd Revision ……………

Oil Industry Safety Directorate

Government of India Ministry of Petroleum & Natural Gas

8th Floor, OIDB Bhavan, Plot No. 2, Sector – 73, Noida – 201301 (U.P.)

Website: www.oisd.gov.in

Tele: 0120-2593800, Fax: 0120-2593802

http://www.oisd.gov.in/

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Preamble

Indian petroleum industry is the energy lifeline of the nation and its continuous performance is

essential for sovereignty and prosperity of the country. As the industry essentially deals with

inherently inflammable substances throughout its value chain – upstream, midstream and

downstream – Safety is of paramount importance to this industry as only safe performance at all

times can ensure optimum ROI of these national assets and resources including sustainability.

While statutory organizations were in place all along to oversee safety aspects of Indian petroleum

industry, Oil Industry Safety Directorate (OISD) was set up in 1986 by Ministry of Petroleum and

Natural Gas, Government of India as a knowledge centre for formulation of constantly updated

world-scale standards for design, layout and operation of various equipment, facility and activities

involved in this industry. Moreover, OISD was also given responsibility of monitoring

implementation status of these standards through safety audits.

In more than 25 years of its existence, OISD has developed a rigorous, multi-layer, iterative and

participative process of development of standards – starting with research by in-house experts and

iterating through seeking & validating inputs from all stake-holders – operators, designers, national

level knowledge authorities and public at large – with a feedback loop of constant updation based

on ground level experience obtained through audits, incident analysis and environment scanning.

The participative process followed in standard formulation has resulted in excellent level of

compliance by the industry culminating in a safer environment in the industry. OISD – except in the

Upstream Petroleum Sector – is still a regulatory (and not a statutory) body but that has not

affected implementation of the OISD standards. It also goes to prove the old adage that self-

regulation is the best regulation. The quality and relevance of OISD standards had been further

endorsed by their adoption in various statutory rules of the land.

Petroleum industry in India is significantly globalized at present in terms of technology content

requiring its operation to keep pace with the relevant world scale standards & practices. This

matches the OISD philosophy of continuous improvement keeping pace with the global

developments in its target environment. To this end, OISD keeps track of changes through

participation as member in large number of International and national level Knowledge

Organizations – both in the field of standard development and implementation & monitoring in

addition to updation of internal knowledge base through continuous research and application

surveillance, thereby ensuring that this OISD Standard, along with all other extant ones, remains

relevant, updated and effective on a real time basis in the applicable areas.

Together we strive to achieve NIL incidents in the entire Hydrocarbon Value Chain. This, besides

other issues, calls for total engagement from all levels of the stake holder organizations, which we,

at OISD, fervently look forward to.

Jai Hind!!!

Executive Director


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NOTE

Oil Industry Safety Directorate(OISD) publications are prepared for use in the oil and

gas industry under Ministry of Petroleum & Natural Gas. These are the property of

Ministry of Petroleum & Natural Gas and shall not be reproduced or copied and loaned

or exhibited to others without written consent from OISD.

Though every effort has been made to assure the accuracy and reliability of the data

contained in these documents, OISD hereby expressly disclaims any liability or

responsibility for loss or damage resulting from their use.

These documents are intended to supplement rather than replace the prevailing

statutory requirements.

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F O R E W O R D

The oil industry in India is nearly a 100 years old. Due to various collaboration agreements with foreign companies, a variety of practices have been in vogue and various international codes, standards are being followed. Standardisation in design philosophies and operating and maintenance practices at a national level was hardly in existence. This lack of uniformity coupled with feedback from some serious accidents that occurred in the recent past in India and abroad, emphasised the need for the industry to review the existing state of the art in designing, operating and maintaining oil and gas installations.

With this in view, the Ministry of Petroleum and Natural Gas in 1986 constituted

a Safety Council assisted by the Oil Industry Safety Directorate (OISD) staffed from within the industry in formulating and implementing a series of self regulatory measures aimed at removing obsolescence, standardising and upgrading the existing standards to ensure safer operations. Accordingly OISD constituted a number of functional committees comprising of experts nominated from the industry to draw up standards and guidelines on various subjects.

The first edition of the document on „Fire Prevention and Fire Protection System

for Electrical Installations‟ was prepared by the Committee on „Electrical Fire Protection‟ and published in July 1996. The present revised edition has been prepared by Committee constituted with help of member industries. This document is based on the accumulated knowledge and experience of industry members, and various national and international codes and practices.

It is hoped that the provision of this document, if implemented objectively, may go a long way in improving the safety in the oil and gas industry.

This document will be reviewed periodically for improvements based on the new

experiences and better understanding. Suggestions from industry members may be addressed to:

The Coordinator Committee on



Government of India Ministry of Petroleum & Natural Gas

8th Floor, OIDB Bhavan, Plot No. 2, Sector – 73, Noida – 201301 (U.P.)

Website: www.oisd.gov.in

Tele: 0120-2593800, Fax: 0120-2593802

http://www.oisd.gov.in/

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COMMITTEE ON ELECTRICAL FIRE PROTECTION

LIST OF MEMBERS

(1998) ____________________________________________________________________ NAME ORGANISATION ____________________________________________________________________ LEADER Shri V P Sharma Engineers India Ltd. MEMBERS Shri K K Gupta Indian Oil Corporation Ltd. Shri N V Mani Cochin Refineries Ltd. Shri G C Dwivedi Gas Authority of India Ltd. Shri P Kamalasekharan Indian Oil Corporation Ltd. Shri Niraj Sethi Engineers India Ltd. MEMBER CO-ORDINATOR Shri J K Jha Oil Industry Safety Directorate -----------------------------------------------------------------------------------------------------------------

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COMMITTEE ON REVISION OF OISD-STD-173

LIST OF MEMBERS

(2003) ____________________________________________________________________ NAME ORGANISATION ____________________________________________________________________ MEMBERS Shri R P Singh Bharat Petroleum Corporation Ltd. Shri K S Mishra Indian Oil Corporation Ltd. Shri S M Ghotavadekar Hindustan Petroleum Corporation Ltd. Shri K V Bhaskara Rao Hindustan Petroleum Corporation Ltd. Shri Niraj Sethi Engineers India Ltd. Shri H K Sarsar Bongaigaon Refinery & Petrochemicals Ltd. Shri A K Das Kochi Refineries Ltd. Shri A P Chakravarty Numaligarh Refinery Ltd. MEMBER CO-ORDINATOR Shri C M Sharma Oil Industry Safety Directorate GUIDANCE Shri V P Sharma (Leader of 1

st Committee) Engineers India Ltd.

Shri Anant Narayan Engineers India Ltd. ----------------------------------------------------------------------------------------------------------- ------

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COMMITTEE ON REVISION OF OISD-STD-173

LIST OF MEMBERS

(2015) ____________________________________________________________________ NAME ORGANISATION ____________________________________________________________________ LEADER Shri Harish Kumar Engineers India Ltd.

MEMBERS Shri Gyasuddin Engineers India Ltd. Shri Mahesh Kotasthane Reliance Industries Ltd. Shri K Viswanathan Bharat Petroleum Corporation Ltd. Shri P Mondal Bharat Petroleum Corporation Ltd. Shri Amit Kumar Oil & Natural Gas Corporation Ltd Shri Rajesh Kumar C Mangalore Refinery and Petrochemicals Ltd Shri RM Koli Hindustan Petroleum Corporation Ltd. Shri Praveen Upreti Hindustan Petroleum Corporation Ltd. Shri Mintu Handique Numaligarh Refinery Ltd. Shri Ramesh Kumar Roy Indian Oil Corporation Ltd. Shri Sumit Pal Petronet LNG Ltd. MEMBER CO-ORDINATOR Shri Dharmvir Oil Industry Safety Directorate Shri Parmod Kumar Oil Industry Safety Directorate

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FIRE PREVENTION AND PROTECTION SYSTEM FOR

ELECTRICAL INSTALLATIONS

CONTENTS

SECTION DESCRIPTION PAGE

1.0 INTRODUCTION 9 2.0 SCOPE 9 3.0 DEFINITIONS 9 4.0 GENERAL REQUIREMENTS 11 5.0 FIRE PROTECTION FOR SUBSTATION 17 6.0 ELECTRICAL GENERATOR INSTALLATIONS 21 7.0 TRANSFORMER INSTALLATION 23 8.0 CABLE INSTALLATION 25 9.0 TEMPORARY INSTALLATIONS 27 10.0 REFERENCES 29

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1.0 INTRODUCTION

Fire protection assumes greater importance in context of the electrical installations located in hydrocarbon industry where classified hazardous atmosphere may be encountered and electricity may constitute one of the sources of ignition for fire incidents and explosions. It is therefore imperative that the concept of fire prevention / protection is built into the electrical system right from the design and engineering stage and continued to the operation / maintenance stage.

2.0 SCOPE

This document provides the minimum requirements for preventing fire hazard, containing and suppression of fire in the electrical installations in the petroleum, oil and gas sector. However, this standard does not cover off-shore oil installations. It also excludes drilling rigs and well head installations. Consideration has been given to the prevalent national and international standards on fire protection of Electrical Installations. This standard in no way supersedes the statutory requirements of Factory Inspectorate, Petroleum and Explosives Safety Organisation (PESO), Directorate General of Mines Safety (DGMS), Central Electricity Authority (CEA) or other Government Bodies. Fire protection system shall be designed in accordance with applicable OISD standards as amended from time to time.

3.0 DEFINITIONS

For the purpose of this standard, the following definitions will apply.

i) CABLE RUN A stretch of cable(s) for carrying electrical current from one point to the other. ii) CABLE TRAY

A horizontal or vertical metal / FRP support for a cable run. A cable tray may support one or more cables. iii) CABLE RACK Two or more cable trays arranged one above the other. iv) CABLE TUNNEL/ GALLERY Any closed section of the structure or building which primarily serves as a distribution route for cables for electrical power and / or the control & monitoring of equipment and having walk-through corridors. The Tunnel / Gallery could be above ground or below ground.

v) CABLE TRENCH An Underground or below ground section with RCC / Brick lining which primarily serves as a distribution route for cables for electrical power and / or the control and monitoring of equipment. RCC lined trenches are usually provided with removable covers.

vi) CABLE CELLAR The space below the switchgear floor in a substation, which is utilised for installation of cable trays in sub stations with the floor raised above grade level.

vii) CABLE SHAFT AND RISERS

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Vertical ways for carrying cables constructed either of concrete / masonary or fabricated from steel. viii) CABLE VAULTS

Cable vaults are generally built below a control room wherein cables from various facilities terminate before entering the control panels.

ix) ELECTRICAL INSTALLATIONS Electrical installations include generating stations, sub-stations, switch gear rooms, transformers, cabling systems and outdoor switch yards. x) FIRE STOP A through penetration fire stop is a specific construction consisting of materials that fill the opening around penetrating items, such as cables, cable trays, Bus Ducts, conduits, ducts and pipes, and their means of support through the wall or opening to prevent the spread of fire. xi) FIRE BARRIERS

Fire barriers are passive fire protection systems which prevent propagation of fire through floor penetration or wall penetrations. xii) FIRE BREAKS Fire breaks are passive fire protection systems like chemical coating which prevent the propagation of fire in horizontal or vertical run of cables and prevent spread of fire to nearby combustibles, e.g. for preventing propagation of fire in long cable runs in the cable galleries, cable trenches and cable cellars etc.

xiii) CLASSIFICATION OF FLAMMABLE LIQUIDS

Flammable liquids vary in volatility and have a flash point below ninety-three degrees Centigrade (93o C). These

are divided into following three classes as per the Petroleum Act,1934: “Petroleum Class A”:means petroleum having a flash-point below twenty-three degrees Centigrade (23

o C)

“Petroleum Class B”:means petroleum having a flash-point of twenty-three degrees Centigrade (23

o C) and

above but below sixty-five degrees Centigrade (65

o C)

“Petroleum Class C“: means petroleum having a flash-point of sixty-five degrees Centigrade (65

o C)

and above but below ninety-three degrees Centigrade (93

o C)

xiv) HAZARDOUS AREA In accordance with the Petroleum Rules applicable to Hydrocarbon liquids, an area shall be deemed to be a hazardous area, where:

a) Petroleum having flash point below 65

0 C or any inflammable gas

or vapour in a concentration capable of ignition is likely to be present; b) Petroleum or any inflammable liquid having flash point above 65

0C is

likely to be refined, blended, handled or stored at or above its flash point. .

xv) VOLTAGE The difference of electric potential measured in volts between any two conductors or between any part of either conductor and the earth as measured by a suitable voltmeter, and is said to be -

“Low Voltage” where the voltage does not exceed 250 volts under normal condition;

“Medium Voltage” where the voltage exceeds 250 volts but does not exceed 650 volts under normal condition;

“High Voltage” where the voltage exceeds 650 volts but does not

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exceed 33000 volts under normal condition; and

“Extra high Voltage” where the voltage exceeds 33000 volts under normal condition.

xvi) INDOOR TRANSFORMER The transformer installations which have limitations in approach for the Fire Tender (in other words, which are not easily accessible by a fire tender) shall be considered indoors for the purpose of fire protection. xvii) SWITCH GEAR

Switch gear shall denote circuit breakers, cut outs and other apparatus used for the operation, regulation and control of circuits. xviii) SWITCH BOARDS Switch Boards shall mean a Panel assembly including the switch gear for the control of electrical circuits, electrical connections and supporting frame.

xix) SUB – STATION Sub – station means any premises or enclosures / building or part thereof, being large enough to admit the entrance of a person after the apparatus therein is in position, containing apparatus for transforming or converting energy to or from a voltage, apparatus for distribution or any other apparatus for switching, controlling or otherwise regulating the energy, and includes the apparatus therein.

a) Large Sub-Station Sub Station housing High and Medium Voltage cabling and switchgear. b) Small Sub-Station Sub Station having Medium and Low Voltage cabling and switchgear.

xx) GENERATING STATION

Any building or part thereof where power generating sources are installed and operated along with switchgear, switch boards and other equipment required to generate / control power.

xxi) SHALL “Shall‟‟ indicates a mandatory requirement. xxii) SHOULD ``Should‟‟ indicates a requirement which is recommendatory in nature.

4.0 GENERAL REQUIREMENTS

i) Electrical installations including generating stations, distribution station etc. are exposed to considerable fire risk since these facilities handle hydrocarbons as fuels, as well as, mineral oils for transformers which are highly flammable. Oil and gas handling or bearing equipment, storage of fuel oil, piping related to fuel oil and gas are risk prone areas. ii) All the above fire risks need to be minimized by taking suitable measures for the prevention of fire and also for protection against fire. iii) Electrical equipment shall be regularly inspected and tested to prevent the chances of fire. Precautions to be adopted for fire safety of electrical installations should conform to relevant Indian Standards i.e IS : 1646, OISD-STD-137 etc. iv) Periodic tests of electrical equipment shall be carried out as per IS : 1646 and preventive maintenance schedule shall be prepared based upon the recommendations of equipment manufacturers.

v) Flammable cleaning fluids such as gasoline, benzene, ether, alcohol etc. shall not be used on energized equipment. These fluids may, however, be used on de-energized equipment. The equipment should be left in de-energised condition at least half an hour after such cleaning.

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vi) All electrical equipment shall be kept free of carbon dust, oil deposits, grease etc.

vii) All electrical equipment shall be effectively earthed in accordance with requirements of IS : 3043, OISD-RP-149. viii) Generating stations shall be kept clean and free from any obstacles at all times. Waste material shall not be dumped near storage areas for oil, gas and other combustible material.

ix) Naked flame, welding etc. shall not be permitted in storage area or in the vicinity of fuel oil tanks. In case it is unavoidable, prior permission in writing, from appropriate authority, shall be obtained and due care and protection shall be exercised in line with provisions under OISD-STD-105 in respect of Work Permit.

4.1 ELECTRICAL EQUIPMENT FOR

HAZARDOUS AREAS 4.1.1 In order to ensure that electrical

equipment does not become a source of ignition in an oil / gas handling installation, it is necessary that the equipment is suitably selected for installation in hazardous areas.

4.1.2 Following factors shall be considered

for proper selection of electrical apparatus and equipment for areas where risks due to flammable gases or vapours may arise:

a) Area classification i.e. Zone-0, Zone-1 or Zone-2 (Refer OISD-STD-113 for definitions) b) Gas group classification i.e. the gas group IIA, IIB or IIC (Refer OISD-STD-113 and IS/IEC-60079-20 for gases covered in the gas groups) c) Temperature classification i.e. T1,T2, T3, T4,T5 or T6 (Refer OISD-STD-113 for temperature ranges)

d) Environmental conditions in which the apparatus is to be installed:

i) Electrical apparatus in general and switching and controlling apparatus in particular should be installed in safe area i.e. non-hazardous area.

ii) While deciding the route of overhead power lines, necessary consideration shall be given to avoid overhead lines passing through hazardous areas.

Electrical equipment intended for service in hazardous area shall be selected in accordance with IS:5571 and these shall be tested by agencies such as CIMFR, ERTL, CPRI or independent test laboratory of country of origin for such equipment. Indigenous Flameproof equipment shall comply with relevant BIS standard as per requirements of statutory authorities. All hazardous area equipment shall be approved by the applicable statutory authority. For details on hazardous area classification, enclosure protection etc., OISD-STD–113, OISD-RP-149, NEC – 1985, IS:5571, 5572, IS/IEC 60079-17, Petroleum Rules and Oil Mines Regulations shall be referred.

4.1.3 Portable field equipment for testing/ simulation in hazardous area shall be used only after taking applicable work permit from concerned departments.

4.2 PLANT EARTHING 4.2.1 It is recommended that all electrical

equipment be suitably earthed. Earthing system shall, in general cover the following:

Equipment earthing for personnel safety.

System neutral earthing, and

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Protection against Static and Lightning discharges. The earthing system shall have an earthing network with required number of earth electrodes connected to it. The following shall be earthed:

System neutral

Current and potential transformer secondary neutral

Metallic non-current carrying parts of all electrical apparatus such as transformers, switchgears, motors, lighting / power panels, terminal boxes, control stations, lighting fixtures, receptacles etc.

Steel structures, loading platform etc.

Metallic cable trays and racks, lighting mast and poles.

Storage tanks, spheres, vessels, columns and all other process equipment.

Electrical equipment fencing (e.g. transformer, yard etc.)

Cable shields and armour.

Flexible earth provision for wagon, truck.

Pump handling Hydrocarbon if its base Plate is separate from motor„s base plate.

Turbo driven pump handling hydrocarbon

4.2.2 Plant earthing design shall generally

be carried out in accordance with the requirements of CEA Safety Regulation, 2010 and IS: 3043. Following requirements should be met:

All earth connections should be visible for inspection to the extent possible.

Unless adequately connected to earth elsewhere, all utility and process pipelines should be bonded to a common conductor by means of earth bars or pipe clamps and connected to the earthing system at a point where the pipelines enter or leave the hazardous area except where conflicting with the requirements of cathodic protection .

4.2.3 Where installed, lightning protection

shall be provided as per the requirements of IS:2309. Self conducting structures having metal thickness of more than 4.8 mm may not require lightning protection with aerial rod and down conductors. They shall, however, be connected to the earthing system, at least, at two points at the base.

OISD-GDN-180 may be referred for details on lightning protection

4.3 The resistance values of an earthing

system to the general mass of earth should be as below:

For the electrical system and equipment a value that ensures the operation of the protective device in the electrical circuit but not in excess of 4 Ohms. However, the generating stations and large sub stations, this value shall not be more than 1 Ohm.

10 Ohms in the case of all non-current carrying metallic parts of major electric apparatus or any metallic object.

Earthing of Tanks

a) Every tank or other receptacle for the storage of petroleum in bulk, other than a well head tank or tanks of less than 50,000 litres capacity containing petroleum Class C shall be electrically connected with the earth in an efficient manner by not less than two separate and distinct connections placed at the opposite extremities of such tank or receptacle. The roof and all metal connections of such tank or receptacle shall be in efficient

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electrical contact with the body of such tank or receptacle. b) The connections and the contacts required under (a) shall have as few joints as possible. All joints shall be rivetted, welded or bolted and also soldered to ensure both mechanical and electrical soundness.

c) The resistance to earth shall not exceed 7 Ohms and the resistance to any part of the fitting to the earth plate or to any other part of fitting shall not exceed 2 Ohms.

All joints in pipelines, valves, plants , storage tanks and associated facilities and equipment for petroleum shall be made electrically continuous by bonding or otherwise; the resistance value between each joint shall not exceed 1 Ohm.

Pipeline runs / installations having cathodic protection shall be governed by Rule-109 of Indian Petroleum Rules-2002.

4.3.1 Earth rods and conductors shall be

designed to cope with the conditions imposed. The earth conductor shall be adequately sized to carry the applicable maximum earth fault current without undue temperature rise. All joints shall be protected against corrosion.

4.3.2 All the electrical equipment operating

above 250 volts shall have two separate and distinct connections to earth grid.

4.3.3 In all cases, connection to earth

should be made in accordance with IS : 3043.

4.3.4 For further details on earthing

installation practices, refer OISD-RP-147 and OISD-RP-149.

4.3.5 The main earthing network shall be

used for earthing of equipment to protect it against static electricity.

An independent earthing network

shall be provided for lightning

protection and this shall be bonded with the main earthing network below ground, minimum at two points.

4.3.6 An approach for removing fire or

explosion danger is to provide means for adequate dissipation and prevention of accumulation of static electricity, thereby ensuring that static discharges do not occur. One of the methods to eliminate risk of static electricity build up is grounding and bonding.

The subject of Static accumulation caused by flow of petroleum products and the mitigation methods are dealt in detail in OISD-STD-110 and same should be referred.

4.4 MINIMISING EQUIPMENT FAILURE 4.4.1 Maintenance

a) Proper functioning of electrical equipment can only be ensured by means of periodic preventive and predictive maintenance of the equipment. This enhances equipment life and also ensures safety of the equipment, installation and operating personnel. b) Maintenance may be daily, weekly, quarterly or annual depending upon the type of equipment. Adequate logs shall be maintained to ensure that maintenance is carried out as per approved checklists. Preventive maintenance should be carried out as per schedules laid down in OISD-STD-137. c) Live parts of switch gear shall be made inaccessible from any inadvertent physical contact, lizard entry etc. These shall be suitably covered by barriers and shrouds.

d) It shall be ensured that the electrical installation shall be rust / corrosion protected. This should be achieved by painting all equipment at regular intervals by use of zinc passivated, nickel plated hardware, stainless steel hardware, through provision of canopies for outdoor

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equipment and covering of terminal boxes to prevent ingress of water etc. Battery rooms shall be kept dry and well ventilated and all terminals shall be kept covered with petroleum jelly to avoid corrosion.

e) During maintenance if any equipment is removed from panel doors, etc. which leaves an open cut-out on the equipment, the same shall be promptly sealed using blanking plates or other means, to ensure that there is no loss of the degree of ingress protection and also that this does not provide a means of access for entry of dust / vermin etc. It shall be ensured that all unused cable entries are blanked off. f) All battery banks shall be routinely checked for healthy cell voltage, specific gravity of cells, electrolyte level etc. g) Insulation resistance of all electrical equipment, such as, all switchboards, motors, transformers, cables etc. shall be routinely measured and logged to ensure healthiness of equipment. Dielectric strength of transformer insulating oil, Oil Circuit Breakers etc. shall be measured and recorded. Oil filtration shall be carried out wherever necessary. Dissolved Gas analysis for transformers rated 5MVA and above should be carried out as a predictive method to assess health of transformer. OISD-STD-137 to be followed for inspection schedule of transformers. h) All cable terminations, bus-bar joints, etc. shall be tightened, more so for equipment subjected to vibrations, to ensure that there are no hot spots which could lead to fire / equipment failure. i) Settings of protective relays shall be checked to ensure that they are set as per the recommended settings. Protective Relays shall be tested / calibrated in line with OISD-STD-137.

j) Unused cable entries in any switchboard / Electrical installation shall not be kept open. k) Conduits used for cable entry shall be sealed and earthed. l) All wall openings of an electrical sub station including cable entries shall be properly sealed to arrest water entry inside sub station. m) All switchboards shall be provided with safety interlocks as covered under OISD-RP-149 and inspected as per OISD-STD-137. n) Transformer and switchyards shall be maintained free of vegetation / dry grass.

o) Switchgear panels should be inspected regularly for identifying un-used cable entries/ loose panel doors, and corrective action to be taken to avoid flashovers due to external intrusion such as lizard / vermin entry etc. p) Earth grid resistance shall be measured and recorded regularly to ensure operation of related protective devices in case of fault. The periodicity and documentation shall be governed by CEA Safety Regulation#41&48

For bulk storage tanks, Rule-128 of Petroleum Rules 2002 shall be followed in respect of testing of earth connections. Water should be poured in the earth pits at regular intervals to maintain the required earth resistance. q) Special emphasis shall be laid on the maintenance of equipment installed in hazardous areas to meet requirements of Rules-112 & 113 of Indian Petroleum Rules-2002. The rules are quoted for ready reference:

Rule-112: “Maintenance of approved electric apparatus and wiring:

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All electric apparatus and wiring in a hazardous area shall at all times be so maintained as to retain the characteristic on which their approval has been granted” Rule-113:

“Repair and test work: 1) No Flame proof or intrinsically safe apparatus shall be opened and no work likely to impair the safety characteristics of such apparatus or electric wiring connected thereto shall be carried out until all voltage has been cut off from said apparatus or wiring. The voltage shall not be restored thereto until the work has been completed and the safety characteristics provided in connection with the apparatus and wiring have been fully restored. 2) Notwithstanding anything contained in this rule, use of soldering apparatus or other means involving flame, fire or heat or use of industrial type of apparatus in a zone “1” area shall be permitted for the purposes of effecting repairs and testing and alterations, provided that the area in which such apparatus or wiring has been installed, has first been made safe and certified by a competent person after testing with an approved gas – testing apparatus to be safe and free from inflammable vapours, gases or liquids and is maintained in such conditions, so long as the work is in progress”

No alteration that might invalidate the certificate or other document relating to the safety of the apparatus, shall be made to any apparatus. If replacement components such as cable glands, conduit or conduit accessories, are available only with thread forms which differ from those provided on the apparatus, suitable adaptors having necessary certification and approval shall be employed.

Equipment enclosures and fittings shall be examined to see that all

stopping plugs and bolts are in position and properly tightened. Locking and sealing devices shall be checked to ensure that they are secured in prescribed manner. Replacement fasteners, nuts, studs and bolts shall be of the type specified by the manufacturer for the particular apparatus. No attempt shall be made to replace or repair a glass in a flameproof enclosure e.g. in a luminaire or other enclosures, except by replacement with the complete assembly or part obtainable from the manufacturer, complying with the approval certificate.

If at any time, there is a change in the area classification or in the characteristics of the flammable material handled in the area or if the equipment is relocated in the area, the area classification drawing should be correspondingly revised and a check shall be made to ensure that the equipment selection corresponds to the revised area classification. A system shall be established to record the results of all inspections and the action taken to correct defects.

4.5 FIRE ALARM AND GAS

DETECTION SYSTEM 4.5.1 Each installation should be equipped

with a fire detection and alarm system which shall be able to detect fire at the earliest and to give an alarm at the manned location so that appropriate action can be taken (e.g. evacuation of personnel, summoning of fire fighting organisation, triggering of the extinguishing process etc.)

4.5.2 Hydrocarbon/LEL/Toxic Gas detectors

shall be provided in the air-intake duct of substation pressurisation system and / or air conditioned system. On actuation, it shall simultaneously give an alarm, close the damper and cause tripping of the Pressurisation System and /or AHU

4.5.3 The alarm system may be activated

by automatic detection devices viz.

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smoke detectors, heat detectors etc. or by manual operation of manual call points i.e. brake glass units.

4.5.4 Installations involving hazardous

gases shall additionally be equipped with gas detection system which shall be able to detect the leakage of hazardous gases and give alarm when the gas concentration has reached 20% of lower explosive limit (LEL) and should activate the shut-down system, as well as give signal to shut-off valves to prevent further release of the hazardous gases in the concerned areas when 40% LEL has reached. The tripping should be based on a logic to prevent any nuisance operation.

Gas detectors shall be employed in outdoor / indoor process areas handling hydrocarbons.

4.6 COMMUNICATION SYSTEM

The plant shall have adequate communication system in line with the requirements of OISD-RP-149.

4.7 EMERGENCY LIGHTING 4.7.1 In addition to the normal lighting, each

installation shall be equipped with emergency (AC) and critical (DC) lighting.

4.7.2 Emergency lighting shall enable the

operators to carry out safe shut-down of the plant, to gain access and permit ready identification of fire fighting facilities such as fire water pumps, fire alarm stations etc.

4.7.3 Critical lighting, sourced from 220V or

110V DC system shall enable safe evacuation of operating personnel and shall be employed along escape route, assembly point and critical installations such as first aid centre, control rooms, manned sub-stations, fire water pump house etc.

4.7.4 As a good engineering practice, the

AC emergency load should be considered as 20-25% of normal lighting load. In small plants, with small AC emergency load and where

there is no separate standby DG set, critical DC lighting system may take care of the entire emergency lighting.

4.7.5 For hazardous areas, emergency

lighting fixtures shall be explosion proof Ex(d) type, irrespective of the area being classified as zone-1 or zone-2.

4.7.6 For details on lighting philosophy and

installation practices, refer OISD-RP-147, OISD-RP-149.

4.8 REQUIREMENTS FOR CONTROL

ROOM / BUILDING

Manned areas such as control rooms, operator rooms etc. and areas housing critical equipment including power supplies required for safe shut down of plants located close to process units / hydrocarbon storage areas shall be governed by provisions in OISD-STD-163.

4.9 REQUIREMENTS AND EQUIPMENT

PROTECTION

The electrical system shall be designed and selected to ensure the following: a) Protection of equipment against damage which can occur due to internal or external short circuits, overloading, abnormal operating conditions, switching, lightning surges etc. b) The continuity of operation of those parts of the system not affected by the fault, is maintained. c) Personnel and plant safety.

Accordingly, relays and protective devices shall be suitably selected and coordinated. All the numerical / microprocessor based protection relays shall be provided with conformal coating and 3C3/3C4 compliant as per IEC-60721-3-3. Refer OISD-RP-149 for further details.

5.0 FIRE PROTECTION FOR SUB-STATION

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5.1 Sub-station is a vital Electrical installation which has a number of sources of fire hazards like Cables, Transformers and Circuit Breakers. Cables are normally PVC/XLPE insulated and pose fire hazard in case of overheating or short circuit. An Oil filled Transformer contains large quantity of oil and is liable to explosion and fire in case electrical faults do not clear fast or get sustained. Circuit Breaker and other switchgear items may cause low intensity fire along with explosion in case of severe earth fault.

5.2 LOCATION OF SUB-STATION 5.2.1 The sub-station shall be located in a

safe area as close to the load centre as possible. Consideration should be given to cooling tower sprays, vapours contributing to insulation breakdown etc. and other factors affecting the safe operation of the sub-station.

Also refer OISD Standard 118 (Layouts for Oil and Gas Installations)

5.3 LAYOUT OF SUB STATION Following requirements should be

borne in mind while engineering the layout of a sub-station:

i) Access for initial installation of the switchgear, possible removal, overhaul or replacement, as well as fire fighting etc. ii) Ease of operation. iii) The location must be considered in conjunction with possible cable routes. iv) It is imperative that any water tanks or pipes are not positioned directly above the switchgear.

5.3.1 In large plants, the main sub-station floor shall be raised above grade level and the space below the sub-station floor (cellar) shall be utilised for installation of cable trays.

5.3.2 Every sub-station shall have a

minimum of two exits. These exits shall be located at opposite ends of

the building, to prevent the possibility of operating personnel being trapped in case of fire. Large sub-stations shall have three exits. Maximum distance for a man trapped in fire shall not exceed 30 meters to the nearest fire escape. Panel and equipment layout shall be so designed that personnel can go out from any exit. The doors shall open outward and be equipped with exit signs.

5.3.3 The cable cellar level of the sub-

station floor shall be suitably raised from adjacent grade level to avoid water ingress. The roof shall be given adequate water proofing treatment to ensure that rain water does not seep into the sub-station.

5.3.4 Dry Type transformers should be

preferred over Oil filled transformers for indoor duty. If unavoidable, location and provisions for indoor transformers shall be governed by relevant clauses of CEA Safety Regulation#44 .

Further guidelines on sub-station layout may be referred to OISD-RP-149.

5.3.5The switchgear layout shall allow sufficient space at front of the switchgear to withdraw and maneuver the circuit breaker trolley and at the rear to allow access for cable terminations, maintenance and inspection of equipment CEA Safety Regulation#37(iii) shall be referred in the context.

5.3.6 The design of the floor must take account of any fixing arrangements and base channels for switch boards. It is essential to ensure that the holes or slots for cables are clear of floor steelwork or reinforcement.

5.3.7 Switch boards should be provided with space heaters of sufficient rating to prevent condensation. Switchgear located in a high ambient temperature (for example, in a boiler house of the building) should be adequately ventilated in order to avoid excessive cubicle temperature.

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5.3.8 Cable trenches inside the sub-stations shall be filled with sand, pebbles or similar non-flammable materials or cable trenches shall be covered with non-inflammable slabs. All cable entries to the sub-station building should be properly sealed to prevent entry of any fluids/chemicals etc.

5.3.9 Fire extinguishers, suitable for electrical fires (CO2 type) and round bottom fire buckets with clean dry sand, conspicuously marked, should be kept in easily accessible position near the switchgear enclosure.

5.3.10 Each sub-station should have layout diagram, at entrance, for location of fire extinguishers and fire exits. Fire exits / escape route shall also be marked on the cable cellar floor.

5.3.11 The switchgear rooms should be kept clean and tidy and should not be used as a storage room, especially for combustible materials such as discarded printer outputs, newspapers, cans, rags for cleaning etc.

5.3.12 a) Transformers and equipment

installed outdoors, having an individual or aggregate oil content of 2000 Litres or more shall be located in a suitably fenced and locked enclosure separated on all sides by at least 6 Metres from any building including substation. There should be no door or window opening in the surrounding building if transformers are within 6 Metres thereof. b) If the transformers are within 6 Metres of doors and window openings of surrounding buildings then they shall be protected by single fireproof doors and 6 mm thick wired glass in steel frames respectively.

c) Separating walls shall be provided between transformers having an individual or aggregate oil content of 2000 Litres if the distance between transformers cannot be maintained as 6 metres minimum. d) Separating walls shall not be necessary in case of transformers

having an aggregate oil capacity exceeding 2000 Litres but individual oil capacity of less than 5000 litres if the distance between transformers and other apparatus is more than 6 Metres or if the transformers are protected by an approved type of high velocity water spray system. e) Where, however, oil capacity of individual transformer is larger than 5000 litres, separating walls shall be provided unless all equipment / buildings / plants are located at a clear distance of not less than the following:

Oil Capacity of Individual Clear Separating Transformer Distance(Mtrs) 5000-20000 Lit. 8 20000-30000 Lit. 15

f) The provisions as above shall not

be applicable if the transformer is filled with non-combustible insulant liquid.

5.3.13 Separating walls between sub-station

and outdoor transformer bays, if required, shall have a four hour fire rating. In general, a 230 mm thick reinforced concrete wall or a 355 mm thick brick wall is considered to provide adequate fire protection. Separating walls shall be carried right upto the roof level, unless the roof is more than 3 mtrs. above the highest point of the equipment, in which case, the wall shall be carried upto a height of at least 600 mm above the top of the equipment (e.g: Transformer conservator) level. The separating wall shall extend at least 600 mm beyond the width of the transformer and cooling radiators.

All openings from outdoor transformer bays into the building shall be sealed to prevent smoke from entering other portions of the sub-station. The requirements under this clause, however, do not apply to dry type transformers or transformers having sulphur hexa fluoride, non-flammable coolants and having primary voltage not more than 33 kV.

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5.4 TRANSFORMER

It is essential to pay major attention to early detection of any abnormality / fault and to protect the transformer from faults/fires so that fault is cleared before transformer catches fire. Regular monitoring of checks as specified by manufacturer (such as Oil Temperature, Winding Temperature and calibration / testing of IDMT and instantaneous Over current / Earth Fault protections, Stand by earth fault protection, Restricted earth fault protection, Differential protection etc.) should be followed. For details of protection relays for transformers, refer OISD-GDN-149.

a) OUTDOOR TRANSFORMER For outdoor transformer, firefighting equipment and fire prevention arrangement shall be as per Clause 7.0. It shall be ensured that the discharge from any pressure relief devices on the transformer shall be directed such that there is no injury to person working around and also directed away from any nearby equipment in order to prevent any damage to that equipment by discharged flaming oil. b) INDOOR TRANSFORMER Selection of indoor transformer shall be guided vide clause 5.3.4. Separating wall for indoor oil transformers shall be as per Clause 5.3.12.

5.5 SWITCHGEAR ROOM

a) Smoke detectors of ionization/ optical/ multi sensor types in sufficient quantity on cross-zoning principle with suitable time delay devices incorporated as per guidelines given in IS:2189, should be installed in large substations. b) Capacitor units containing a flammable dielectric fluid, if located indoor, should be separated from

adjacent electrical equipment by a one hour fire barrier. c) Fixed exhaust and ventilation systems should be switched off during a hydrocarbon leak. d) The Battery rooms should be given special attention and the amount of hydrogen evolved from the batteries during charging should be well ventilated to preclude a build-up of flammable atmosphere. . Light switches should be located outside the battery room. Fittings exhaust fan and associated switch/ sockets inside Battery room (flooded type Batteries) shall be of Ex „d‟ Gas Group IIC type. Heat detectors inside battery room shall be Ex‟i‟/Ex‟d‟ type.

5.6 CABLE TUNNEL/ GALLERY

An effective fire / smoke Detection system shall be installed. Alarm / annunciation system shall be provided in Control Room / Manned Sub station to facilitate appropriate action. Performance / efficacy of such system shall be checked periodically and documented. Selection of fire fighting equipment should be governed by provisions under Clause 5.8. As an abundant safety measure, fixed fire extinguishing system with deluge facility using water spray may be applied for cable galleries and cable tunnels.

The water spray system consists of a number of spray nozzles mounted on piping network covering the complete span of cable trays laid horizontally and vertically. To avoid total flooding, cable galleries and tunnels may be divided into a number of zones. Each zone is controlled by one deluge valve assembly connected to detection network. When fire occurs in a particular zone, detection unit in that zone will actuate and corresponding deluge valve will open and spray water.

5.7 CABLE CELLAR

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An effective fire/smoke Detection system shall be installed. Alarm / annunciation system shall be provided in Control Room / Manned Sub station to facilitate appropriate action. Performance / efficacy of such system shall be checked periodically. Selection of fire fighting equipment should be governed by provisions under Clause 5.8. Additionally, Hydrants at strategic locations for fighting fire in major emergencies may be installed.

5.8 FIRE FIGHTING EQUIPMENT FOR MINOR FIRES

5.8.1 Electrical de-energisation / isolation

of the equipment from the energized system should be the first step to fight an electrical fire. Following should be given attention: i) Where energized electrical equipment is involved in a fire, the non-conductivity of the extinguishing media is of utmost importance, and only extinguishers expelling dry powder, Carbon Di-oxide (without metal horn) or vaporizing liquids should be used. Once the electrical equipment is de-energised, extinguishers suitable for the class of fire risk involved can be used safely. ii) All foams are electrically conductive and should not be used on fires involving exposed energized electrical equipment. After de-energization, fire extinguishers should be used depending on class of fire.

5.8.2 Annexure B of IS:2190 shall be referred for assessment of class of fire / nature of occupancy criteria etc. Following firefighting equipment shall be provided in electrical sub-station to fight minor fires: i) Dry Chemical Powder fire extinguisher ( 9 Kg. Capacity)

To be located inside sub-station. The number should be determined based on a maximum travelling

distance of 15 meters. At least 1 fire extinguisher shall be provided for every 250 m

2 area.

ii) CO2 Extinguisher (4.5 Kg. Capacity)

To be located in sub-stations. The number should be determined based on a maximum travelling distance of 10 meters. At least 1 fire extinguisher shall be provided for every 100 m

2 area.

iii) Sand Buckets One in each Transformer Bay. The use of fire buckets shall not be considered as a substitute for fire extinguishers.

The inspection & maintenance of the above fire extinguishers shall be based on the guidelines of OISD-GDN-115.

5.8.3 Water should be used with discretion

in areas of electrical equipment. Provision should be made to prevent inadvertent operation of a water suppression system. When water is used, an adequate drainage system should be provided. Before selecting water for use indoors, it should be determined if the equipment is water tight.

If conditions are such that the equipment cannot be de-energized and the fire cannot be extinguished by non-conducting agents, water spray may be used with proper nozzle selection. Water-spray nozzles can be used safely and effectively on voltages upto 138 KV, phase to phase with the following precautions :

i) Only spray type nozzles are used. ii) The minimum distance from the equipment is at least 2 meters. iii) The fire fighter does not stand in a pool of water.

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ANSI/IEEE Standard 979 may be referred for further guidelines on the types of water-spray nozzles.

5.8.4 Carbon dioxide is ineffective for

outdoor applications because it is rapidly dispersed by wind.

6.0 ELECTRICAL GENERATOR INSTALLATIONS

6.1 A fire in a generating installation

would affect the continuity of power supply along with consequent loss of production and probable replacement of highly valuable equipment. It is necessary that every effort be made to reduce the chances of fire.

One of the prime causes of fire is the failure of insulation. Other causes relate to fuel burning equipment, lube oil systems and fuel oil handling / storage systems.

6.2 Gas Turbo generator (GTG) room shall

be adequately ventilated and shall be provided with fixed automatic hydrocarbon detector (LEL detectors) and alarm system. All cable trenches, tunnels and other basement areas on the turbo generator building shall also be similarly protected.

6.3 a) The fire protection system of generators should consist of standard practice of generator manufacturers. This can be realised in most case by CO2 flooding within the generator enclosure on occurrence of a fire. Monitoring of such a fire and CO2 flooding shall be automatic. If it is not automatic, CO2 cylinders shall be readily accessible.

Simulation of operation of system shall be carried out at regular intervals. b) Generators halls should be provided with automatic fire detection system such as smoke detectors. In case of generator halls with high roofs, linear beam type smoke detectors may be employed. Additionally, manual call points

(break glass boxes) shall be employed for fire alarm.

c) Fixed fire water spray type protection system shall be used for controlling a fire involving large quantities of lubricating Oil on Turbine generators. This shall consist of two systems of water protection, one for areas below the operating floor of the turbo generator and designed to extinguish pool fires and also providing protection against heat generated by three dimensional or spray fires. The other is a water spray system for oil fires at or around the bearing housings. Fixed C02 or dry chemical extinguishing systems have been found to be inadequate for basic protection of turbo generator because of the likely hood of re-ignition and, further, these extinguishing media may not be sufficient to cope with a long duration fire. However, in some cases, fixed dry chemical or C02 systems backed by water spray systems should be provided.

6.4 Gas intake to gas turbines shall be

through separate pipe-lines with remote controlled solenoid / motor operated valves located in the open area. Additionally, manually controlled stop valves shall be located near the gas turbines.

6.5 All fuel oil tanks located above

ground, with a capacity exceeding 45 KL shall be bonded to the ground with at least two separate and distinct connections on the opposite extremities of such tank. The roof and all metal connections of such tanks shall be bonded to the body of such tanks.

6.6 To prevent the hazard of static

electricity, the fill and recirculation lines to storage tanks shall discharge below the liquid level.

6.7 Adequate illumination shall be

provided at all locations, for effective fire fighting purposes. The minimum illumination level shall be 150 lux for boiler house, turbine hall etc. and

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150-200 lux for control rooms and sub-stations.

6.8 a) Emergency diesel generator (DG)

sets are normally required to be operated only on failure of the normal supply. These emergency DG sets shall be located in well ventilated rooms and provided with air exhaust equipment in order to dissipate the heat generated during power generation. The day tank for diesel shall not be located inside the emergency DG room as it is a potential source of fire and may also release flammable vapours. The day tank shall be located outside the DG room within a fenced area, preferably with a corrugated sheet roof to provide protection from direct sun and rain.

Emergency Diesel Generator should be provided with auto cut in system. b) The exhaust from the emergency DG shall be conveyed outside the DG room through an exhaust pipe. The direction of exhaust pipe shall be so chosen as to help disperse the exhaust away from the DG room. c) Batteries for starting the DG set shall have containers of non-corrosive, non-flammable material. Batteries shall be located in a well ventilated location, to prevent the accumulation of an explosive mixture.

7.0 TRANSFORMER INSTALLATION

7.1 A transformer is the main equipment

in the switchyard / sub-station which is prone to fire hazards due to the large quantity of oil it contains. Special attention shall be devoted to safeguard the transformer and other nearby equipment against fire.

7.2 SEPARATING WALL

Separating walls shall have fire rating and specifications as per clause 5.3.13. Separating wall shall also be designed to withstand the explosion of transformer bushing or lightning

arrestor. Clause no. 5.3.12 shall be referred for provision of separation walls / safe inter distance etc.

7.3 OIL CONTAINING PIT

In order to prevent oil, whether from a small leakage or outflow from transformer tank, from reaching and polluting the water bearing stratum, transformers shall have the following provisions, depending on the oil capacity of the transformer.

7.3.1 Oil Capacity upto 2,000 litres

Transformers installed adjacent to sub-station/buildings shall, where oil capacity does not exceed 2,000 litres, be provided with a layer of 100 mm deep stones of about 40 mm granulation, all around the transformer, for a width of 20% of the transformer height or with a minimum width of about 800 mm.

7.3.2 Oil Capacity exceeding 2,000

litres

Transformers installed adjacent to sub-station / building shall, where oil capacity exceeds 2,000 litres of oil in a chamber, be provided with oil containing pits. The oil containing pit may be shaped as illustrated in Figure – 1, where two alternative solutions are considered. In both schemes, it is recommended that the pit shall extend all around the transformer for a width of 20% of the transformer height, with a minimum width of about 800 mm.

CASE – 1 The oil containing pit shall be able to contain an quantity of oil equal to that of the oil contained in the transformer, plus the volume of water in the fixed fire fighting installation (if any) plus a certain margin for rain water. This margin should be proportionate to the quantity of rain falling in the region where the sub-station lies and to the frequency of the maintenance and emptying operations.

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The whole pit around the transformer shall be filled with stones of about 40/60 mm granulation except that the top 150 mm of the pit shall be devoid of stones. A layer of stones of this size extinguishes the burning oil penetrating it. A Porosity factor of 40% may be considered for 40/60 mm size gravel.

CASE – 2 The oil containing pit shall be similar in construction to CASE – 1, however, it shall be able to contain a quantity of oil corresponding to approximately a third or even less than the volume of oil contained in the transformer. In such a case, the oil containing pit shall be connected to a waste oil tank as per Clause 7.3.3.

In case oil capacity exceeds 9,000 litres, in any chamber, provision shall be made for draining away of any oil, which may escape or leak from the tanks, to a waste oil tank as per Clause 7.3.3. In both the cases, it shall be possible to empty the pit by means of a pump.

If the emptying is automatic, the emptying system shall be laid out and controlled in such a way as to prevent oil flowing into the general drains of the sub-station. The bottom of the pit shall be constructed of impermeable concrete.

7.3.3 Waste Oil Tank

The oil containing pit, when of a smaller volume than required, say able to contain a quantity of oil corresponding to only a third of the volume of oil contained in a transformer, shall be connected by a draining pipe of earthenware or steel, not less than 150 mm diameter, to a waste oil tank situated in suitable place. If only one waste oil tank collects the drainage of several containing pits, the tank should be situated either in a place central to the transformers or in the lowest part

of the sub-station to assist drainage. The tank shall be of sufficient capacity to receive, without overflowing, the contents of the largest transformer of the sub-station plus the water of any fixed fire fighting system, and a certain quantity of rain water collected from all pits. No other drain shall lead to the tank. This tank shall be provided with an air vent large enough to avoid over pressure during operation. The vent shall be provided with a flame arrestor. The whole internal surface shall be impermeable. (Refer Figure:2). Provisions shall be made for suitable oil soak pit where use of more than 9000 litres of oil in any one oil tank, receptacle or chamber is involved, in line with CEA Safety Regulation#44,

Oil containing pit shall be sized for following i) The spill of the largest single

container

ii) Two nos. of fire hose operating for

a minimum of 10 minutes

iii) The maximum design discharge of

fixed fire suppression systems

operating for a minimum of 10

minutes

Portable pumping arrangement shall be considered for emptying of waste oil pit.

7.4 FIRE PROTECTION

The first para of Clause 5.4 on fire prevention rather than fire fighting should be recapitulated .

7.4.1 Fixed fire extinguishing systems for

oil filled transformers shall be provided if any one of the following conditions exists:

a) Neither separating walls having fire rating and specs as per 5.3.13 are erected in line with criteria under clause 5.3.12 nor the inter distance criteria under same clause is met.

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b) The transformers of the sub-station/ switch station are located in the basement of the building. c) Transformers of 10 MVA

and above rating or in case of oil filled transformers with oil capacity of more than 2000 liters.

7.4.2 In case, fixed fire extinguishing

systems are to be installed, they may consist of the following:

i) Water Spray (Mulsifyre) System Such a system shall be provided with automatic high velocity water spray system (Mulsifyre System) or foam water spray. Complete impingement on all exterior surface (except bottom surface) shall be done with a rate not less than 12.5 ltr./min/sq. meter. Any space of width greater than 300 mm shall have separate arrangement for spray of water. Separate arrangement of water spraying shall be considered for conservator.

Piping for spraying should not be carried across the top of the transformer unless no other alternative space is available. Water spray shall not impinge on energized bushing and lightning arrestor.

The system operation shall be automatic unless :

Automatic operation presents a hazard.

System is attended by trained personnel round the clock.

Foregoing clauses 5.8.1 and 5.8.3 should be kept in mind while adopting water as a medium of fighting electrical fire. ii) Nitrogen Purging Nitrogen injection system offers a fast fire prevention and

extinguishing system for oil filled transformers. Pressure relief valve operation due to internal faults activates the system and nitrogen is injected from the bottom area of the tank, which brings down the oil temperature, as well as, provides an inert nitrogen layer on top of the hot oil to prevent any contact of oil with oxygen. Such system may be considered in areas where availability of water is limited or there is probability of water freezing. Alternately, use of dry type transformers may also be considered for such areas.

Use of Nitrogen Purging is optional. Necessary techno- economic study is to be done by the user before going for the system. Fixed fire extinguishing system should be tested once every year to check system effectiveness.

8.0 CABLE INSTALLATION 8.1 Electrical cables are usually

sheathed with polyvinyl chloride (PVC) which contributes to the rapid spread of fire. PVC also gives off highly toxic products out of combustion including corrosive gases, when it is exposed to intense heat or is involved in fire. Dense smoke from the cable fires hinders fire fighting efforts and the approach to the source of fire.

The concept of fire protection of cables, cable trenches, tunnels and galleries is based on the following considerations:

a) Preventing / delaying fire damage to the cables to preserve their functioning and increasing their resistance to fire/heat.

b) Preventing / retarding flame propagation through cable runs.

c) Segregating cable runs into compartments with a view to localising a possible cable fire and its spread.

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d) Providing effective fire detection and alarm system e) Providing effective fire extinguishing system. f) Avoiding cable joints in Over Head cable Racks and Trenches in hazardous areas and, g) Avoiding cable runs in close proximity to drains carrying Steam / Hydro carbons at high temperature.

8.2 Cables in trays, racks or ducts

which are critical (e.g. cables feeding emergency shutdown and emergency depressuring valves) shall be protected from fire damage, unless they are designed to fail safe during a fire exposure. Fire proofing requirements of such cables shall be as per API-2218.

8.3 In order to avoid spread of fire due to cables, it is recommended that the outer PVC sheath of all cables used in industry shall be flame retardant type conforming to category AF as per IS:10810. The minimum Oxygen index shall be 29. The cables shall have a low smoke property and the minimum value of light transmittance shall be 60% as per IEC-61034-2.

For plants having sub station with trenches (without cellar) and major under ground cable runs, minimum Oxygen index requirement, as above, is not essential.

8.4 For various types of cable laying

methods employed, the following precautions are recommended from fire safety point of view:

8.4.1 Directly Buried Cables

Where cables are directly buried in the ground after excavation of soil and then backfilled with sand and soil, care shall be taken to ensure that no combustible materials such as paper, plastic, rags, wood shavings etc. accumulate within the trench prior to backfilling. H.V. and M.V cables should be segregated by

a 300 mm gap and a layer of bricks laid between the two.

8.4.2 Cables Laid In Trenches

a) Where cables are laid in lined trenches, the trenches shall be with covers of fire retardant material. b) Lined Cable trenches located in hazardous areas, shall be filled with sand. c) Cables laid in lined trenches in safe (non-hazardous) areas should be run on cable rack/trays supported from the walls of the cable trench. The cable trays/racks shall be suitably spaced to ensure that a fire in one tier will not propagate to another tier. Minimum distance between tiers shall not be less than 225 mm. Cables may also be laid in lined trenches using the methodology as applicable for direct burial.

8.4.3 Cables laid in Tunnels / Galleries / Cellars

a) Measures shall be taken to keep the tunnels well ventilated. Cable tunnel floors shall be provided with a slope leading to a sump with a sump pump. The tunnels shall be kept dewatered at all times. Fire fighting equipment and hydrants shall be located at the entrances of tunnels. b) Compartmentalisation of cable tunnel should be done by provision of separating walls at an interval not more than 30 meters and by sealing the opening with the use of fire stop / fire barriers.

c) All cable tunnels, cellars etc. shall be provided with adequate number of fire escapes, evenly distributed, so that maximum distance for a man trapped in fire does not exceed 30 meters to the nearest fire escape. d) Inter-compartment movement should be through fire check doors.

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e) Fire detection and alarm system shall be provided in the cable tunnels, cellars.

f) Emergency lighting shall be provided inside the cable cellars and cable tunnels. g) The fire rating of fire stop when tested according to IS : 12458 and of barrier wall when tested according to IS : 3809 shall not be less than the rating of the building components. h) No welding or naked flame should be allowed inside cable tunnels and cellars. Same, if unavoidable, shall be carried out with proper work permit and precautions meeting norms under OISD-STD-105 and OISD-STD-137.

i) Fire stops should be deployed at the locations where the trenches enter the sub-station. Entry of cables to the blast resistant control room buildings shall be through fire resistant multi cable transits (MCTs).

8.4.4 Cables Laid On Overhead Cable Trays

a) Cables laid on cable trays supported on pipe sleepers etc. shall be at least 300 mm above grade level. The space below the cable trays shall be kept free of dry grass/vegetation. b) Cable trays installed on elevated pipe racks, especially if carrying hydrocarbons, shall be provided with GI sheet, of adequate thickness, to protect the cables in case of a fire in the pipe rack/equipment located below the cable trays. c) Cable trays should not be installed at an elevation where acid/hydro-carbon piping is located above the cable tray. For cables running directly below the Air fin coolers/ Acid/ alkali Pipelines, GI sheet of adequate thickness shall be provided for protection of cables.

d) Special attention, such as the installation of fire stops or fire breaks, shall be given to vertical cable runs, since they propagate fire more rapidly as compared to horizontal runs. e) FRP cable trays, wherever provided, shall be fire resistant and UV resistant type.

8.4.5 Fire Prevention in above ground installation

a) Above ground cable installations where proper separation cannot be achieved, a fire resistant barrier or shield shall be deployed between the trays or a passive fire-retardant coating may be applied to the cables. Fire hazards can also be minimized by installing fire breaks. Fire resistance criteria shall be in line with IS-12459. b) Consideration should be given to the application of passive fire coating for the following areas: i) Immediately after end termination or joints upto a length not less than one meter in either direction. ii) Crossing or T-crossings upto a length not less than one meter in either direction. iii) Cable passing through high temperature area, entire length. iv) Exposed vertical length, entire length.

9.0 TEMPORARY INSTALLATIONS

9.1 Temporary electrical supply is

generally required for installations erected for short periods of time ranging from a few hours to a few months. Temporary supply installations need extreme care to avoid any hazard from electrical shock by exposure to live wires or fire due to short circuiting. Such installations are exposed to

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environmental hazards also. It is, therefore, necessary to take extra precautions for such installations to ensure safety of personnel and equipment.

9.2 Temporary installations are

considered as electrical installations open to sky or partially covered and intended to be used for periods not exceeding 6 months or during Plant Turn Around.

9.3 Such installations may be exposed

to the following environmental conditions:

Water splashes/jets of water from any direction

Partial or total covering by water

Dust/ Dirt

Vibrations

Impact

Ingress of insects,rodents, birds, vermin etc.

Exposure of solar radiation

Exposure of lightning strokes

Apart from the above, fire risk may be enhanced in such temporary installations due to the nature of construction material and, in some cases, due to storage of combustible material.

9.4 Each installation shall have a main switch with a protective device, installed in an enclosure adjacent to the metering point. The enclosure housing the main switch and other distribution equipment shall not be affected by conditions specified in Clause 9.3.

The room housing the main switches shall be well ventilated with an adequate clearances and operational space around.

9.4.1 The main switch shall be connected

to the point of supply by means of an armoured cable adequately protected from rain water. Cables shall be laid underground covered with sand, brick and earth for ensuring mechanical protection.

When laid above ground, cables shall be properly cleated or supported on rigid poles at least 2m high. Crossing of roads shall be avoided. The height of the main switch shall not exceed 1.5 m

9.5 The outgoing shall be double or

triple pole switches with fuses/MCBs. Rewirable type fuse should not be used. Copper wire shall not be used as a replacement of fuse in fuse carriers . HRC fuses of proper rating shall be used. Loads in a 3 phase circuit should be balanced and load on neutral should not exceed 20% of load in the phases at the point of supply.

9.6 An independent earthing facility

should preferably be established within the temporary installation premises. All appliances and equipment shall be adequately earthed. In case of armoured cables, armour shall be bonded to the earthing arrangement of power supply source.

In case of local earthing, earth electrodes shall be buried near the supply point and earth continuity wire shall be connected to local earth electrode/ plate and further distributed to various appliances.

9.7 Earth should not be used as Neutral

of an Electrical installation. 9.8 Unless unavoidable, Taped joints

shall be avoided and proper Industrial Type extension cord shall be used for joining of cables in Construction power installation and temporary electrical installations. If unavoidable, taped joints shall not be employed at heights less than 3 Mtrs. Such joints shall be clamped at either side to avoid any strain.

9.9 The installation shall be adequately

protected against overload, short circuit and earth leakage by the use of suitable protective devices. In construction sites, protection of personnel against indirect contact shall be assured by automatic

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disconnection of supply by means of residual current devices having sensitivity not exceeding 30 mA with instantaneous tripping. Healthiness of the RCCB/ELCB shall be checked before commencement of work everytime.

9.10 All temporary installations shall be

tested before connection of supply to ensure suitability of protection system, adequacy of feeders, cables etc., to check the loads in various circuits and sub-circuits, ensure proper earthing and bonding etc.

9.11 Temporary installation shall not be

employed in hazardous areas. However, adequate provisions shall be made in the permanent electrical installation to cater to the requirements of temporary loads, such as those requiring electrical power during plant shut-down etc.

Adequate number of flameproof 240V AC plug-sockets, flameproof portable hand lamps for illumination of interior of vessels / equipment, during maintenance shall be provided as a part of the permanent electrical installation. As a good engineering practice, these facilities shall be accessible with a flexible cable of 50 Mtrs. length. Flexible cables used for construction power installations shall be doubly sheathed and fine wire armoured. 415 V, TPN, 63A, flameproof welding receptacles, outlets for hydro-jetting/ Stress Relieving machines etc. shall be provided in the plant area at regular intervals to take care of maintenance requirements during plant shut down.

10.0 REFERENCES

The following codes, standards and publications have either been referred to or used in the preparation of this document and the latest editions of the same shall be read in conjunction with this document:

(I) OISD Standards / Recommended Practices (as per latest amendments) such as: a) OISD-105: Work Petmit System b) OISD-110: Recommended Practices on Static Electricity. c) OISD-113: Classification of Area for Electrical Installations at Hydrocarbon handling Facilities.

d) OISD-115: Guidelines on Fire Fighting Equipment and Appliances in Petroleum Industry. e) OISD-116: Fire Protection Facilities for Petroleum Refineries and Oil/Gas Processing Plants. f) OISD-118: Layouts for Oil and Gas installations g) OISD-137 : Inspection of Electrical Equipment h) OISD-147 : Inspection and Safe Practices during electrical installation.

i) OISD-149 : Design Aspects for Safety in Electrical System.

j) OISD-163: Process Control Room Safety.

k) OISD-180: Lightning Protection.

(II) Latest BIS (Bureau of Indian Standards) Publications :

IS-1646 : Code of Practice for fire safety of buildings (General) Electrical Installations. IS/IEC 60079-1: Explosive Atmosphere Part 1 – Equipment Protection by Flameproof Enclosure “d” IS-2189: Code of Practice for Selection, Installation & Maintenance of Automatic Fire Detection & Alarm System

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IS- 2190 : Code of Practice for Selection, Installation & Maintenance of Portable First Aid Fire appliances. IS-2309: Protection of buildings and allied structures against lightning. IS-3034: Code of Practice for Fire Safety of Industrial Buildings: Electrical Generating and Distributing Station IS-3043: Code of Practice for Earthing. IS:3809: BIS Standard for testing of Fire Rating for Barrier Wall. IS-5571: Guide for selection of electrical equipment for hazardous areas. IS-5572:Classification of Hazardous areas (other than Mines) for electrical installations.

IS-10028: (Part 1,2,3) Code of practice for selection, installation and maintenance of Transformer. IS-10810: Methods of tests for Cables. IS-12458: BIS Standard for testing of Fire Rating. IS-12459: Code of practice for fire safety in cable runs.

IS/IEC 60079-17: Explosive Atmospheres– Electrical Installations Inspection and Maintenance

(III) NEC-1985 (IV) INDIAN ELECTRICITY ACT & CEA (measures relating to safety and electric supply) Regulations, 2010 as per latest amendments.

(V) THE PETROLEUM RULES-2002 with latest amendments.

(VI) IEC 60331 & IEC 60332: Fire resisting characteristics of electrical cables.

(VII) ANSI/IEEE STD-979: GUIDE FOR SUB-STATION FIRE PROTECTION.

(VIII) NFPA-850

“Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Station. (IX) Oil Mines Regulation

oisd-std-173 draft

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