5. piping department.pdf

8/16/2019 5. Piping department.pdf

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5.0

PIPING DEPARTMENT

5.1

Foreword

The scope of the Piping Department is to design interconnecting

pipelines between different equipment to carry out fluids from the

source to the delivery point by means of pumps, gravity etc. and to

recycle fluids through closed circuit by following industrial codes &

standards which meet the following criteria for good engineering:

Its material has to be defined from a point of view of the quality,

in order to convey the fluid, in safety conditions for all the years

of the plant duration.

Its route has to be carried out in the more rational and economic

way, as much as possible, and, in addition, it has to satisfy stress

analysis requirements.

The supporting modalities and arrangement have to be properly

designed and verified.

If any, suitable coating has to be provided in order to limit the

losses of heat and gaining of heat. If any, pipes have to be equipped with a proper heating fluid, in

order to assure the minimal temperature of the process fluid

located inside the pipe.

The easy access to the working areas has to be assured.

The lay-out of new piping has to be properly studied in order to

facilitate the connection with the existing ones.


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5.2 Definitions

5.2.1

Definition of Piping and Piping Components

We define Piping the whole of the components which allow the fluid to

be properly contained, conveyed, deviated, intercepted.

We define Piping Component the element which allows one of the

mentioned operations:

Namely

To fluid flow, it shall be necessary to connect the pipe to theequipment by means of flanges.

To convey the fluid, a pipe will be used.

To deviate the fluid, fittings will be used.

To intercept the fluid, valve will be used.

So, we have introduced those elements which in the technical literature

are called “the four families” that constitute the piping, namely:

Pipes.

Fittings.

Flanges.

Valves.

A per cent distribution of the various components (in weight) could be:

Pipes, properly said 56%

Valves 21%

Fittings (curve, T pieces etc.) 13%

Flanges 9%

Others (springs, shoes, etc.) 1%


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5.2.2 Metallurgic Definition of a Steel Component

A steel component, from the metallurgic point of view, can be in carbonsteel, alloy steel, austenitic stainless steel or special, depending on it

constitution:

Iron and carbon steel (apart from impurities);

Iron, carbon steel and a metal more pure than iron;

Iron, carbon steel, chrome in a percentage not lower than 18%,

nickel in percentage not lower than 8%;

Iron, carbon steel and higher percentages of a metal more pure

than iron.

5.2.3 Product Definition

If this definition is sufficient from a theoretical point of view, it is not

enough for what concerning the technical ones due to the reason here

below listed.

For Engineering Company, purchasing always for a third Client at its

own responsibility, the problem relevant to the purchasing definition ofany piping component is quite difficult. Let’s try to understand together

which are the problems to be solved in order to purchase without

inconveniences the simplest component: the pipe.

It shall provide the Purchasing Department with a technical description

of the component to be purchased. This description shall be suitable

and clear in order to assure a perfect understanding and explanation

about the items to be furnished avoiding further or different kind of

furniture.

In the request of purchasing of any component and therefore also for

the pipe it shall be foreseen a non dimensional and a dimensional

classification. The dimensional classification in the case of pipe isformed from the diameter and the thickness or schedule.


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5.2.4 Schedule

In terms of schedule, it has to be remembered that it is just an

indicative number that Anglo-Saxon Norms locates in correspondence of

some thicknesses. It can be also said that on equal terms of number

(including the schedule) the thicknesses are variable to the changes of

diameter even though suitable to support, from a mechanical point of

view, the same conditions of pressure and temperature.

5.2.5

Nominal Diameter

Nominal pipe size (NPS) is a dimensionless designator of pipe size. It

indicates standard pipe size when followed by the specific size

designator number without an inch symbol. For example, NPS 2

indicates a pipe whose outside diameter is 2.375 in. The NPS 12 and

smaller pipe has outside diameter greater than the size designator (say,

2,4,6….) However, the outside diameter of NPS 14 and larger pipe is the

same as the size designator in inches. For example, NPS 14 pipe has an

outside diameter equal to 14 in. The inside diameter will depend upon

the pipe wall thickness specified by the schedule number. Refer to

ASME B36.10M or ASME B36.19M. Refer to App. E2 or E2M.

It is well-know that the values concerning the diameter and its

thickness are not perfectly realised from constructor. In other words, it

must be accepted that pipe cannot be wholly cylindrical and thickness

absolutely constant. It is clear that these variations, are agreed in a

paragraph relevant to those tolerances. Subsequently these tolerances

engrave also to the weight that it will be always different from the

theoretical one.


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5.2.6 Non Dimensional Characteristics

From a non dimensional point of view, in the purchasing order, it has to

specify the following characteristics:

Chemical Composition

Mechanical Characteristics

Mechanical and chemical Testing

Hydraulic Testing

Non destructive Testing

Acceptance or rejection criteria

Bars lengths

Transport

From what was said earlier, we may conclude that knowledge and the

best definition of all relevant prescriptions, done each time during

purchasing be the purchasing order become burdensome, also because

being forced in the negotiation with various manufacturers, the risk of a

long exhausting dealing, in order to comply to all these prescriptions, is

very high.

So as to avoid this kind of situation, the remedy is complete the

purchasing description with an applied codes and specification where

all the necessary prescription are listed in a very analytical way. This

norm is acquainted and accepted by the manufacturer which is officially

in turn to punch the pipes with the mark related to the same norm.

Reference codes generally applied by engineering companies for pipes

are:

-

API (American Petroleum Institute)

-

ASTM (American Society for Testing and Materials)As regards the dimensional part, reference codes are those referred to

ASME (American Society of Mechanical Engineers). Therefore, in the

piping field, it must exist a group of persons specialised in the

materials, apt to furnish to the purchasing department, which has the

commercial aspect, a purchase order, completely defined from a

technical point of view. These persons constitute the Piping Materials

Office.


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They receive necessary information from Process Department.

Precisely, Process Department, furnish, for each plant, a list completed

with all fluids (process and service fluids) to the maximum pressure and

temperature conditions, selecting the steel defined from a metallurgicpoint of view for each fluid

5.3

References

The following shows the documents and their content, which refer to

the piping design.

5.3.1

Piping and Instrumentation Diagrams (P&ID)

The P&ID is a basic document for the piping design of a plant, this

relates to:

Schematic and functional indications for all of the equipment;

All of the process and service lines which connect to the

equipment or otherwise pertaining to the plant. Each line will

have a diameter, fluid content, line number, belong to a pipingclass, possible tracing and/or jacketing;

Valve type and position;

Instrumentation.

5.3.2 Line List

The line list is a list of all the lines foreseen for the plant and describes

each line based on the following:

Project

Unit

Line number

Revision

Connection reference (to/from)


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Number of P&ID it belongs to

Operating and design temperature

Operating and design pressure

Piping class

Material

Rating

Flange finishing

Fluid and service abbreviation

Phase

Corrosion allowance

Coating (painting/insulation)

Test Pressure

Material and insulation thickness

5.3.3 Piping Classes

Each class describes in detail the dimensional characteristics and the

quality of material for each and every element belonging to the piping

class.

These information are developed in order to create one of the most

important documents for the piping design; this document is called

Mechanical Piping Classification.

Classifications are therefore a classes collection and each one can be

defined as a list of all the pipe components defined from a purchasing

point of view in order to convey one or more fluids at certain pressure

and temperature settings through the year in safety conditions. This

collection has the purpose to assembly in a sole document all the non

dimensional definitions of components and to permit to the designer to

rapidly find necessary data.


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5.3.4 Project Documentation

The following shows the characteristics and content of each documentproduced for the piping design.

5.3.4.1 Plot plan

One or both types of Plot plan are produced in accordance with the

characteristics of the plant.

General plot plan

Detailed plot plan

The arrangement of units areas, storage areas, buildings, and facilities

for loading/unloading to be provided within the plant, shall be decided

on the base of the following factors:

Soil characteristic.

Main road or rail access ways.

Location of pipelines to and from plant.

Direction of prevailing wind.

Local law and regulation which may affect the location of units

and storage facilities.

Natural elevation for location of upstream/downstream units and

equipment (such as feed and product storage tanks, waste water

plant, oil/water separator, etc…)

5.3.4.2

General Plot Plan

It is usually designed in A0 format on an appropriate scale, based onthe extension of the plant. The plot plan will show:

Battery limits with relevant coordinates;

All of the main roads;

The process units;

The service production units;

The storage tank parks with their relevant containment basins;


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Areas for product loading and unloading;

Main pipe-racks and sleeper ways;

Buildings and structures;

Orientation towards geographical north and the direction of

prevailing winds.

5.3.4.3

Detailed Plot Plan

Normally designed in A0/A1 format, on a scale of 1:100 or 1:200.

It represents a unit or a zone of the plant.

This plot plan will show:

Battery limits of the unit or zone;

Main roads with their relevant coordinates;

All of the equipment on the ground or at elevation with their

“items” and their position, with the reference axis;

All of the structures and their positions based on their aligning

reference axis, the position of the ladders and the development of

platform, possible monorails and/or overhead cranes;

All of the pipe-racks mounted on the ground with their positionrelevant to the reference axis and alignments;

All of the sleeper ways with the position of the sleeper relevant to

the reference axis;

All of the buildings and their position relevant to the reference

axis and the dimension of the external obstruction;

Dismounting areas and areas for maintenance necessary for the

equipment;

The table for the elevation of the equipment. The table will show

the elevation of all the equipment, based on the tangent line for

the vertical equipment, and the axis for the horizontal equipmentor the support plan for the equipment that have a related axis. In

particular cases, where it is necessary further detail of particular

portions of the plant, elevation designs will be produced.


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5.3.4.4

Key Plan

A small-scale plan of a plant or a group of subdivided plan of differentareas of the plant, which indicates the placement of the principal items

and piping layout of the master scheme.

5.3.4.5

Piping Layout

The piping layout represents an area of the plant, identified on the Key

plan.

It is normally designed in A0/A1 format, and on a scale of 1:33 1/3 or

1:50 the process and/or service production areas, on a scale of 1:50 or

1:100 for the storage areas.Each area, if necessary, will be designed on various levels in order to

clearly show the following:

All the elements shown on the detailed plot plan (equipment,

structures, etc.);

All the foundation parts that come out of the ground;

All the channels;

All the ladders and platforms on the equipment;

All the essential obstructions that create obstacles for piping or

for accessibility (instruments panels, fire prevention equipment,

etc.)

All the pipes and pipe components (valves, flanges, reductions,

etc.).

All the instruments on the lines and equipment.

5.3.4.6 Sections, Elevations and Details

The sections and elevations of the piping layout will be carried out only

in particular cases and only when isometric sketches are not foreseen.

Particular detail on a scale of 1:50 or 1:33 may be necessary for piping

layout on a scale of 1:100 for storage areas.


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5.3.4.7 Isometric Sketches

Isometric Sketches will be made for all the lines with a diameter of 2”and greater, unless otherwise indicated on the scope of work, shown on

the appropriate A3 format; the drawing will not be made on a scale and

will always be done on a single line tract. These will show:

The route of the line with the position of all its components.

(Valves, flanges, elbows, etc.).

The symbol with references for typical installations. (Vents,

drains, etc.).

The flow direction. The line number.

The line piping class.

The piping size and its components.

References to the equipment that connects the pipe.

All of the necessary dimensions for the construction of the line.

The orientation details of the pressure taps for the orifice flanges.

The orientation details for the flange holes if they are different

from the standard.

Eventual construction details, for special pieces to be made on

site, with piping material.

Item and number of all lines or equipment instruments.

For lines of 1 ½ “and less, if required, the isometric sketches will

be approximate for the route and for the dimensions, and must be

verified on the site by the mechanical construction department

before erection, and will not indicate pipes support.

For lines 2” and greater, the isometric sketches will further show:

The exact elevation in a way to permit the prefabrication, other

than the mounting, of the lines.

The symbol with the item of the standard and special auxiliary

support for the contract.

Indication of the field welding to carry out with the mounting, if

required by the scope of work.


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5.3.4.8

As Built Drawings

At the end of the plant construction, the drawings, which will be

updated “as built”, will be the plot plans and the underground pipinglayout.

5.3.4.9 Material Take Off

For each pipe and/or isometric sketch a material list will be made with

the following content:

a. Reference to the sketch

Line number

The zone or area where it is

Sheet number

Date

Piping class

b.

Description of the elements

Code

Destination (see destination code table)

Component type

Material type

Diameter and/or diameters

Schedule and/or thickness

Rating

Quantity Weight of every single element

Prefabrication and erection weight

Total weight


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5.3.4.10 Piping Material Summary

Depending on specific demands, a piping material list will be

summarized by:

Code;

Area /Zone /Unit;

Destination.

5.3.4.11

Isometric List

The isometric list is a list of all isometric sketches of the plant. For eachone of these sketches, the following will be described in detail:

Line number;

Date and revision of issue;

Piping class.

5.3.4.12

Auxiliary Piping Supports

The auxiliary piping supports will be defined in accordance with thestandard.

a. Auxiliary supports for 2″ lines and greater.

b. Auxiliary supports for 1 ½” lines and lower.

5.3.4.13 Auxiliary Piping Support List

Supports for 2″ lines and greater will be prepared based on a

compilation of different types:

Standard supports

Non-standard supports

The standard supports will be identified by an alphanumerical code

which will indicate the type and size.


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5.3.4.14

List of Material for Auxiliary Piping Support

The document, where all of the materials necessary for the construction

of special and standard supports are listed, will show in detail:

Type of material (HEA, Plate ecc.) and size;

Quantity;

Total weight of the type of material;

Total weight of supports.

5.3.4.15

Verification of the Piping Stresses

A flexibility analysis for the lines of the plant will be carried out in

accordance with the Stress Analysis specification.


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5.4 Definitions

5.4.1

General Criteria

To reach a correct planimetric solution, all of the elements of the plant

must be positioned in order to assure that all of the plant requirements

in the following paragraphs are followed.

5.4.1.1 Security

This refers to all personnel present in the plan, the environment, hazard

equipments and all ancillaries within the plant. These requirements will

be followed from the point of view of the planimetric solutions, using the

following preventive measures:

a.

Foresee adequate space between the hazardous components and

other components inside and outside the plant with the purpose of

eliminating or reducing the possibility of risk that they may cause

harmful effect in case of an accident and/or the entity of the

damage.

b.

The positioning of dangerous components in order to eliminate or

limit the effects of their proper functioning both inside and outside

of the plant;c.

The reserving space and access to allow the installation and

operation of fixed and mobile safety equipment, safety scape for

personnel in case of an accident;

d. Protection such as: dikes, protection walls, height differences,

corridors and slopes to reduce or eliminate hazard in case of an

accident

In lack of different standards or contractual limitations, table 4.1.1A

provides a guide for the minimum distances to keep between

components to satisfy the safety requirements (these distances are

referred to the outer surface of the related subject). The regulations inthat table come from the standards of NFPA (National Fire Protection

Association) in which it can be referred to for further details.

For projects requiring a security analysis, the pertinence of the

planimetric solution must be verified case by case respecting the risks

identified by the analysis.


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Table 4.1.1A –Minimum Distance Between Components

Note :

-

The distances are measured in meters- Where it is not specified, the distance will be calculated on the

basis of necessity for accessibility, operability and maintenance.

(1) Ex.: Water pumps, air compressors, etc.

(2) Ex.: Valves and/or activation systems for shut down systems,

water sprayers, etc.


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5.4.1.2

Functionality

This expression stands for the functional performance and productive

capacity of the plant designed. For the best output of the plant, fromthe planimetric point of view, all equipment, plant’s units and

obstructions shall be arranged in such way which shall follow limitation

of PFD, P&ID and equipment data sheet properly.

In particular:

Minimum and maximum lengths of connections and differences

in elevation. Particular attention should be paid to determine the

elevation of different plants, parameters and structure that have

been foreseen for the plant, which causes an elevated cost impact

on the total plant value for the earth work and structural work;

Flexibility for start-up and for the total or partial plant

functioning;

Positioning of components in a manner which assume proper

execution of all connections (piping and relevant accessories,

etc.).

5.4.1.3 Operability

For a good engineering practice and planimetric solution, control

system of all components of the plant shall be located in a suitable

position in order to provide easy access for handling and inspection

during normal operating condition.

To achieve this objective it may be required to foresee accessories like

fixed or mobile platform and relevant stairways.

Moreover it is recommended to integrate all distributed control and

handling components or system of similar characteristics up to its

possible extent.

The standard spaces related to accessibility and operability may differ

considerably from project to project based on the typical environmental

conditions and operating personnel requirements to run the plant

efficiency.


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5.4.1.4 Maintenance

The maintenance requirements are satisfied, from the planimetric point

of view, through the predisposition of:

Roads and routes, wide enough and spacious to enable easy

access and use for mobile equipment for maintenance of the

plant;

Open spaces, around components that need maintenance,

sufficient for: operation of maintenance vehicles, dismounting and

substitution of parts which may need it (such as: motors for

machines, heat exchanger bundles); Eventual fixed equipment such as: davits, monorails, hoists,

according to the scope of work.

5.4.1.5

Constructability

This requirement is fulfilled from the planimetric point of view assuming

that:

a.

Spaces and access for transporting components of the plant andconstruction equipment is sufficient within the site;

b. Sufficient space for any necessary temporary installation for

construction.

Observation should be paid for the positioning of big size, heavy and

long lead items in order to avoid any delay in sequential and

compulsory erection schedule due to the constriction or blockage of

passages.

Moreover attention must be given to the positioning of heavy items;

which are subjected to be lifted up during erection and usually providedwith two lifting vehicles (one for lifting and another for holding).

For best practice position the component close to the erection area

provided with sufficient spaces for easy access to the area and align

horizontally adjacent to the foundation if two components are

positioned in the same area, it is necessary to optimize the area and

leave space for lifting and, in some cases, for their assemblage during

erection.


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5.4.2 Pipe–Rack, Pipe-Way and Building Positioning

This section provides instructions regarding the positioning of singlecomponents of the Plant, particularly regarding problems related to

installation, accessibility and working maintenance.

5.4.2.1 Pipe – Racks

Pipe–Racks, in general, are the piping support and cables, above ground

structures, connecting various process and utility users within the

plant.

In order to work, it is necessary that the lines do not obstruct paths forpersonnel and machines in order to assure safety and accessibility for

other components.

These are normally placed on longitudinal wheel-tracks in the area

representing the limits of the plant’s Units with the purpose of

optimizing the aboveground route and with a symmetrical distribution

for the various users.

Pipe–Racks may be developed on different levels where the elevation

varies according to the material used for construction (ex. for concrete

pipe racks in cement, a large beam obstruction must be considered) and

the eventual presence of intermediate levels, for pipes of a large

diameter (this provides necessary space between the various levels).

As a guide, for steel pipe racks, the height of the support levels is

established as follows:

4.6 m 6.2 m 7.8 m Main pipe-rack

3.8 m 5.4 m 7.0 m For branches

In order to stabilize the size of the pipe-racks, it must be taken into

consideration that, apart from the need to support all pipelines and

cable trays it is necessary to provide 20% of space for the future lines.

When support is also required for air coolers, the width of the pipe-

racks must be the same size as the equipment.


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5.4.2.2

Walkways

In general, pipe ways are corridors where pipe runs above the ground

along the corridor and supported by sleepers, connects different off-siteareas, process and utility areas of the plant.

For pipe ways elevations are exempted from any limitation unless

otherwise indicated.

These are normally positioned along the connecting roads in order to

have easy access for maintenance and operation.

5.4.2.3

Control Rooms

The control rooms are concrete structures composed of offices,

computers, laboratories and other services, where plant operation for

process, utilities are followed and eventually other parts of the complex

are subjected to a continuous surveillance of the plant.

The size of the control rooms and their relevant locations are defined by

the Instrumentation and Civil sections.

The control rooms must be in areas that are not subject to accidental

consequences.

Such as:

Explosions

Toxic clouds

The spread of fires

Where not obtainable, Explosion Test of Construction shall be carried

out according to the pressurization conditions, etc.

Particular attention must be given to the vulnerability of exits and

emergency escape routes.

The control rooms must be located, in a central area in relation with the

users connections and orientations, as long as this does not jeopardize

operators’ interventions, with a cable entrance/exit side facing towards

it; this is to permit an optimal path for the cables and uniformity of

intervention time for the various plant Units.


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Control room must be positioned in proximity to the roads and there

must be zones reserved for operations and parking; this is in order to

permit access (both during normal operation and for maintenance

interventions), a quick intervention in case of emergency and a rapidevacuation.

5.4.2.4

Electrical Substations

The substations and the electrical substations are structures or

buildings containing feeding equipment, transformers, distributors and

control system of electrical power necessary for the Plant’s operation.

In general, this includes:

a. A High Voltage substation or entrance station located where

electrical power feed lines arrive from outside;

b.

A main station, fed from the lines coming from the high voltage

substation and, if any, fed from internal self generators.

c.

Some secondary distribution stations, the number of which varies

according to its complexity, by the number and the users

dislocation.

The dimensions of the substations and electrical substations will be

defined by the Electrical and Civil departments; the location and

orientation will be agreed on, by the Electrical department.

5.4.2.5

High Voltage Substations Or Entrance Cabin

These are generally located in proximity to the High Voltage Switch

Gear. High voltage switchgear is any switchgear used to connect or

disconnect a part of high-voltage power system. These switchgears are

essential elements for the protection and safe operation, without

interruption, of a high voltage power system. These substations must be

provided with roads and with sufficient area for vehicles movement and

parking; this is in order to permit access during normal operation for

maintenance interventions, quick interventions in case of emergency

and rapid evacuations.

In any case, the location of the main electrical substation must be

chosen in a manner to avoid overhead power transmission lines, across

the plant (therefore it is preferable to locate in a decentralized location,

in order to prevent from any accidental consequences; e.g. explosions,

lightning, etc.).


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5.4.2.6

Electrical Power Distribution Stations

According to the international codes and standards, the powerdistribution substations should be located in safe areas where formal

risk analysis, conducted properly and methodically to ensure that

potential accidental risk is either eliminated, or else reduced to a level

as low as reasonably practicable.

Such as:

Explosions

Toxic clouds

The spread of fires

Where not obtainable, Explosion Test of Construction shall be carried

out according to the pressurization conditions, etc.

Particular attention must be given to the reliability of exits and escape

routes.

5.4.3

Equipment Positioning

5.4.3.1 Heaters, Boilers, Relevant Accessories and Stacks

The heaters and relevant accessories are generally grouped in

appropriate areas situated within the battery limits of the pertaining

plant’s Unit and must be distinct from the other equipment.

These areas are chosen on the basis of the prevailing wind directions so

that an eventual gas fuel leak from the plant, will not reach the open

flames of the burners.

Within the distance among the various heaters, there must be adequate

space for operation and maintenance. The minimum distance between the heater edge and the equipment is

shown in table 4.1.1.A.

Within this limit, there may be some equipment that are strictly

connected to the heater, reforming plant reactors, high pressure

exchangers and decoking vessels.


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5.4.3.2 Columns and Reactors

The minimum distance among the columns, reactors and other

equipment is shown in table 4.1.1.A.

When fixed equipment of lifting are installed on the columns and/or

reactors (ex. davits), there must be free space at the bottom of the

equipment in question, the size of the space is given by the range for

the means of lifting plus a margin of about 1 m. These above

requirements permit the transfer, operations and accessibility around

the parts movable (catalyst, internals, valves, etc.). it is mandatory to

foresee an area on the reactors plot plan for the substitution or

replacement of spare parts, for catalyst loading and unloading operation

in order to facilitate any movement required by the operating personnel(ex. need for a particular kind of pavement, eventual bases, etc.).

5.4.3.3

Heat Exchangers

The heat exchangers are installed in groups and, when possible,

providing sufficient space for operators.

In case of exchangers installed on the ground, it has to find the

possibility to install in overlay position.

However, this is normally limited to maximum two elements, except for

the double pipe exchangers or exchangers with a shell diameter lessthan 12” (305 mm).

In case of heat exchangers installed on the structures or the

exchanger’s axis is at an elevation higher than 3.6 m, it will be required

availability of lifting equipment (e.g. monorail) capable of removing and

dismantling shell head, heavy tube bundles and distributors belts on

the shell-side.

The exchanger distributor belt shall be aligned with the shell side

nozzles and also with the concrete saddles, which facilitate marking of

civil works during engineering survey.

The exchangers must be positioned with the distributors facingoutwards the plant.

The plot plan must indicate at least two saddles; one fixed and another

sliding saddle. Horizontal saddle and free to move in the longitudinal

direction, due to thermal and pressure differentials, at the other saddle.

Around the exchanger, the following minimum distances must be

respected:


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0.7 m between each exchanger (this number refers to the

maximum overall dimension, for example between the largest

flange of the distributors);

If there are intermediate groups for regulation or maneuver

valves, a passage equal to 0.9 m must be kept;

If there are no other constrains (to access to other components)

each group of 4 exchangers must be positioned 1.5 m apart from

each other in order to provide sufficient space for maneuvers and

movement of the operating personnel.

5.4.3.4

Vessels

The distance among vessels and other equipment is shown in table4.1.1.A.

The small vessels with vertical axes, containing chemical additives,

must be gathered on the plot plan in a single zone in order to centralize

the operation for their filling.

5.4.3.5 Centrifugal and Alternatives Compressors

The compressors must be positioned, if possible, in only one area (the

compressors may be grouped into one or more of the plant’s Units),

both to facilitate the engineering and the maintenance work: thisgrouping of more compressors with relevant motors permit the use of

only one building and only one monorail, if the closing area is required.

If not otherwise specified, the compressors are generally installed

outside.

If it is necessary to install compressors in a closed building, this will be

done keeping in mind the problem of ventilation which may be solved by

leaving the walls open up to 2.5 m greater than the service platform and

providing appropriate vents on the roof; in any case, we have to

consider the relevant density of the gas, air or steam that may be

released into the atmosphere during normal operation and at anyextreme hazardous conditions as foreseen.

Further problems may arise from the classification of dangerous areas,

with possible requirements for pressurization of the building.


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During the positioning of the reciprocating compressors on the plot

plan, spaces must be provided for:

Draw off of pistons (the draw off will be generally indicated on the

machines design);

Possible pulsation dampers;

Possible intermediary coolers, etc;

Possible local panel

In the design of the compressor room on the plot plan, the following

must be kept in mind:

a. Sufficient space around the machine (about 1.5 m) greater than

what is already planned for the draw off of pistons;

b.

Sufficient space to permit the foundation construction in reinforced

concrete spaced in order to avoid transmitting vibrations;

c.

Utilize the respective spaces, under the work platform, to position

possible pulsation dampers, intermediary coolers;

d. Sufficient space to position the steam turbine, when foreseen, with

the relevant condenser (under the service platform). This spacemust be, around the turbine and the relevant operating equipment

(1.5 m minimum).

e. Align the pillars of the building in a way that they don’t interfere

with the machine’s foundations, this is to facilitate the ground

support of the service platform which must be independently

supported by the machines foundations which so that, should not

transmit inevitable machine vibrations;

f.

Provide an access available for means of transportation and

loading / unloading bay within the room;

g. Do not position any of the equipment or piping bundle, above the

compressors (except for the sealing oil tanks);

h. The K.O. drums must be located outside the compressor rooms.


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5.4.3.6 Pumps

The horizontal pumps will normally be positioned under the pipe-rackwith the hydraulic part facing outwards. If the pumps are placed in

double rows, there must be a free space (minimum 3 m) between the

two rows for the vehicle movement.

When positioning the pumps on the plot plan, it is necessary to:

a.

Align the discharge nozzles with respect to the pipe-rack pillars (as

shown in fig. “Aligning and Pump Basement”);

b. Provide sufficient space (min 3m) behind the motors, or turbines,

to permit cables routing, access, transit for the personnel, with therelevant equipment, both for normal operating phases and for

maintenance interventions;

c. Hydraulic side of the pumps shall be oriented toward the direction

where fluids flow into the plant for pumps suction;

d.

Provide sufficient space between each pump in order to permit easy

transit for operative personnel and plant maintenance. That space

will be normally fixed to about 0.8 / 1 m minimum clear span.

e. Install a fixed monorail for the movement and substitution of spare

part or any other parts when it is not possible to have easy access

to equipment with mobile lifting transport.

In addition to what has been previously described, when positioning the

pumps it is necessary to comply with all the following safety

precautions (including what is shown in table 4.1.1A).

a.

The light hydrocarbon treating pumps with P > 3.5 MPa (relevant)

must not be positioned under the air coolers, but they may bepositioned under the pipe-rack;

b. The hydrocarbon treating pumps with T ≥ T+ (flash point) must not

be positioned under the air coolers and must also not be positioned

under the pipe-rack. Furthermore, they must have a distance at

least 4 ÷ 5 m from the flammable product treating pumps with T <

T+ (point of flammability);


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c.

The pumps handling flammable products with T < T+ (point of

flammability) may be positioned both under the air coolers and the

pipe rack;

d.

Pumps handling hydrocarbon must be at a distance, as much as

possible, 4 ÷ 5 m from the equipment containing flammable

liquids, or combustibles. If this is impossible, it is necessary to

take precautions by providing adequate fire protection and an

adequate fire proofing systems;

e. The pumps must not be installed within dikes or storage tank

enclosure walls.


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5.4.3.7

Air Coolers

Apart from particular requirements, the air coolers will generally be

installed above the pipe-racks, preferably in a central position relevant

to the connecting equipment, avoiding too close to equipment and/or

structures which may interfere.

To permit sufficient air passage and an efficient thermal exchange, the

following requirement must be considered:

a. Keep sufficient space between the motor service platform and the

upper pipe-rack floor. These requirements are normally met by

leaving a minimal distance of 1.6 m from the highest point of theobstacle, for example from the outside row of the pipe with the

largest diameter on the pipe-rack floor (including eventual

insulation);

b. In case of Air Coolers located within 9m each other, the outlet port

will be at the same elevation (this is to avoid the recirculation of

hot air);

c. No equipment may be placed over the air coolers.

When planning the plot plan for all of the components of the plant’sunit, it is necessary to consider that the air coolers need access road

and space for the maneuvering of cranes.

The relevant sizing will be set according to the following demands:

Installation of air coolers during construction;

Substitution of ventilators (motors, propellers, exhaust fans);

Substitution of air cooler parts and/or connected piping;

Substitution of tube bundles.


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5.4.3.8

Hydrocarbon Storage Tanks (Atmospheric)

These tanks may be, according to their construction, fixed roof and/or

floating roof.

The fixed roof tanks are used for light hydrocarbons as petrol, crude oil,

naphtha.

To position a storage tank in the tank farm, following criteria have to be

considered:

a. The tank farm area for the crude oil storage must be located at the

highest point within the plant area and possibly where it does not

exist any booster pump in order to facilitate loading pump suction.

b.

The tank farm area of semi-refined products has to be located tothe unit of the plant aimed for loading.

c. The tank farm area for “finished products” is generally located near

the former (semi-finished products) and possibly towards the

shipment facilities.

The minimum distance between the tanks, the conformation and the

location of the containment dams and the sizes and capacity of the

relevant dikes will be defined on the basis of the codes of the country

where the Plant will be carried out.In lack of precise data, it is possible to assume:

a. The volume of the dike must be equal to that of the tank (more

than 10 cm of border on each side). If the dike contains more than

one tank, the volume must be equal to the tank with the maximum

capacity plus the submersed volume by the other tanks;

b. The height of the dike above ground level must not exceed 4 m;

c.

The height of the tank must not exceed 12 m of the dike wallsunless otherwise indicated by local codes;


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d.

The size of the dike will be defined fulfilling the condition that any

straight line passing through the area of the tank’s roof (or the

upper edge, if the it’s a floating roof) and forming a 45° angle with

the vertical point falling within the perimeter inside of the dikeitself.

The dikes are generally formed up with soil covered by a layer of

concrete (this choice is rather preferable than concrete walls).

A passage way 1 m wide must be provided on the crest of the dikes and

shall have stairways outside the dike at a distance not more than 8 m.

5.4.3.9 Pumping Stations (“Off-Site” Areas)

During designing a plot plan, the altitude profile has to be considered tolimit the pumping station work; in addition in the design of the plot

plan, it is important to take into consideration the following

requirements:

a.

The elevation of the pump’s suction nozzles must be arranged in a

way to avoid the creation of pocket on the lines. These pockets

negatively influence the performance of the pump and can block

the total emptying of the connected tanks.

b.

The pumping stations must be positioned near the roads and musthave areas for operation and parking; this is to permit access (both

during normal operation and for maintenance), a rapid intervention

in case of emergency;

c. The layout of the connected piping must be optimized (to/from

pipe-way and to/from tanks).

5.4.3.10

Light Hydrocarbon Storage Tanks (Balls and Large Cylinders)

The storage tanks for light hydrocarbons can be spherical containers

(spheres) and/or horizontal cylindrical containers; they are used for

stocking liquefied petroleum gas (LPG) and semi-cooled products

(“Cigar” shape, type).

From the safety point of view, a proper solution to be adopted, in order

to avoid possible overheating with the possibility of explosion, could be

the one to use buried horizontal containers.


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This solution is particularly recommended:

For storages near built-up areas; For high capacity storages;

For small storages (ex. intermediate products) adjacent to the

process Unit;

5.4.3.11 Flares

The distance of the flares from the process unit and from the

hydrocarbon storage tanks depends on the height on the heat generated

from the flame, in order to avoid to damage the equipment and

jeopardize the safety of personnel.

This distance will be defined, after a careful safety analysis, during the

execution of the Project.

The zones near the flares where there may be the presence of personnel

must be treated in accordance with API RP 521.

5.4.4

Free Spaces for Maintenance

a.

Access roads and inside of the plant’s limits:

1.

width of the principal access road 6.0m

2. width of the road within the Unit 4.0m

3. footh path width 1.0m

4. internal curve 6.0m

b. Headroom for the passage of large maintenance

vehicles at the principal access points of the plant,

measured from the roadway and the lowest point

of the pipe or structures elements:

6.1m

c. Headroom for the passage of railways, measured

by the summit of the rail and the lowest point

of the pipe; isolated or not structures

elements (to verify with local codes:) 6.5m

d. Minimum distance from rail axis to any obstacle

(to verify with local codes): 2.6m


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e. Minimum height for the passage of maintenance

cranes in areas of the plant: 4.3m

f.

Headroom for maintenance access for

the pumps 3.2m

g.

Access space for pump maintenance , measured

by the end of the pump/motor to the external

edge of the structure and/or piping:

3.0m

h. Minimum distance between the road edge footh

path and equipment and/or piping

1.5m

i.

Minimum passage for personnel access among

equipment,structures and/or piping:

0.75m

j. Minimum overhead passage under piping 2.1m

or structures

k.

Minimum walkway width for walkways

connecting to the platforms or sleeper-ways 0.80m

5.4.4.1 Horizontal Heat Exchangers Installed on Structures

a. Fixed tube bundle exchangers:

Minimum space between structure limits

and the external distributor edges: 0.75m

b.

Removable bundle exchangers:

Minimum free space between the structurelimits and the external edge for the fixed shell: 0.75m


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c.

“Double tube” or “fin-tube” heat exchangers:

Minimum free space between structure limits

and shell cover: 1.5m

Minimum free space between the structure

limits and piping connections: 0.75m

d.

For all types of exchangers, the minimum

distance between the lower nozzle flanges

and the structure will be: 0.2m

5.4.4.2

Air Coolers Mounted on Elevated Structures or Pipe-Racks

a. Free access from piping and/or equipment,

for the mounting of piping bundles by a crane 4.0m

b.

Free vertical space between the electrical motors

of fans and service walkways 1.8m

5.5

Piping Installation

This Section will provide the criteria regarding the installation of piping

connected to the various equipment of the Plant, with particular detail

regarding problems related to positioning, work accessibility,

maintenance and proper function.

5.5.1 Pipe-Racks

Normally, when more floors are necessary, the pipes are positioned as

follows: Service piping: upper floor

Process piping: lower floor

A typical distribution of the piping on the pipe-rack, on the basis of

services and size, is shown in the figure 1.


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5.5.1.1 Pipe Spacing

The piping installed on pipe-racks will have sufficient space betweeneach other.

This space is necessary in order to carry out the operations following

the installations, those being: flanges clamping, welded joints, painting,

insulation, etc.

The pipe spacing (L) between two pipes, no jacketed, must at least

respect the distance resulting from the following formula:

.min252

)( ++

= Dt DF

mm L

where:

DF (mm) = external diameter of the piping flange with DN or greater

rating

Dt (mm) = external diameter of the piping with a smaller DN

Table 5.2.1A shows the pipe spacing (L) normally respected between

non-jacketed piping with a flange rating of 150# ÷ 900#.


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Table 5.2.1.A – Pipe Spacing Between Non-Insulated Piping

(mm)

Note: for diameters or ratings not covered by the present table, apply the

formula already indicated.

If one or both of the pipes are jacketed and are steam traced, the pipe

spacing must be increased by the insulation thickness.


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5.5.1.2 Branches

As general rule, the piping branches from the header are positioned:

Underside, for lines conveying liquids. This allows the self-

drainage, avoiding the likely risks caused by product stagnancy in

the pipelines (corrosion, water hammer, etc.)

On the top part for lines conveying air, gas or steam. This allows

to prevent the possibility of circulation of the relevant

condensates that may cause erosions, not considered, in the

choice of the appropriate material concerning the above

mentioned fluid.

The branches from the cooling water header, with lines of DN ≤ 1- 1/2",

are to be placed on the top part in order to avoid occlusions due to

slush.

The connection of outlet piping to the blow-down header are to be

placed on the top part and must be made at 90° for lines of DN ≤ 1-

1/2", or with an inclination of 45° toward the flow, for lines with DN ≥

2". This configuration is necessary for the following reasons:

Because of the low pressure within the line, the head loss mustbe reduced as much as possible.

The stress on the joints must be reduced as much as possible.

5.5.1.3

Positioning

The lines of DN >12"must be placed within the piping bundle and as

close as possible to the column of the Pipe Rack structure in order to

reduce the stress coming from the beams (see figure 1).

Steam and condensate headers, that generally need loops, must beplaced so that the loop mainly develops within the pipe-rack (see figure

1).

Piping facing downwards (for control valves, hose station, etc.) must be

placed toward the pipe-rack pillar in order to facilitate the supporting.

They must face outside the pipe rack reserving a free area of 500 mm of

clear light between the pipe surface and the edge of the pillar.


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A span of about 31 m under the pipe rack must be free of pipes,

machines and equipment in order to allow the passage for service

vehicles.

5.5.1.4

Elevations

The bottom pipe elevation of the insulated lines must consider the

shoes height that are normally as follows:

100mm with insulation ≤ 80mm

150mm with insulation 85 ÷130mm

The blow down manifolds must have a minimum slope towards the

relevant separators equal to 2 per mil, so avoiding pocket.


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Fig. 01 – Typical Section of Pipe-Rack


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5.5.2 Pipe- Way

The piping installation criteria on the pipe-way are the same describedfor the pipe-rack with the exception of all process and service pipelines,

which will be installed at the same elevation; the minimum suggested

DN will be 1-1/2″ .

On the pipe-way, for pipelines with DN>30″ (750), the pipe spacing will

be estimated considering the possibility of access among the pipes

(about 300 mm of clear light).

5.5.2.1

Elevations

Piping must be installed at a bottom elevation equal to 400 mm. Such

elevation is valid for all of the process and service lines, regardless of

diameter. An exception to this rule regards the pipelines conveying

steam of which elevation is fixed in accordance with the following table.

Bottom of Pipe Minimum Elevation for Lines Conveying Steam

DN Line ≤ 10″ 12" ÷ 20" > 20

Elevation (mm) 400 600 650

The above mentioned minimum elevations are required in order to allow

the installation, where necessary, in the low part of condensate of

drainage groups by means of steam traps, the above mentioned groups

must be arranged to allow, with a minimum distance from the ground,

the operations in the relevant maintenance.


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5.5.3 Installations on Pressure Equipment

5.5.3.1 Piping on Columns or Vessels

The piping installed on columns will be grouped in a free section, facing

the pipe-rack so avoiding, where it is possible, to cross the service

platforms.

The pipelines that descend on the columns will be placed away from the

equipment, in order to allow proper supports.

All the spillage lines of fractionating columns have to come down from

the nozzles, downward 3 m, at least, before changing direction.

5.5.3.2

Piping on Exchangers

The lines connected to the distributors nozzles shall be supported in

order to allow the disassembly of the spool. The pipelines connected to

the exchangers shall be designed and supported in order to facilitate

the removal of the tubes bundle, introducing, where necessary, coupling

flange for disassembly.

Typical installation of piping on exchangers is shown in the figure 3.


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Fig. 02 – Typical of Piping Installation on Columns


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Fig. 03 – Typical of Piping Installation on Exchangers


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5.5.4 Piping Installations on Pumps, Compressors and Steam Turbines

5.5.4.1 Pumps

The pumps suction lines shall possibly be shorter in line according to

the requirements of the thermal expansion of the suction line. In any

case, pockets shall not be formed.

On centrifugal pumps, in case that the suction nozzle would be smaller

than the line, it will be used a reduction “eccentric type” placed with the

plane part upward. For the lines that are involved in transport of high

density fluids (slurry) or fluids, for which, pocket are expressly

forbidden, the eccentric reduction will be placed with the plane part

downward.

Concerning double suction pumps “side-side type”, a length of straight

pipe, equal to five times the diameter of the line, between the pump

nozzle and the first elbow if placed on the horizontal plane, shall be

foreseen. When the elbow is placed on the vertical plane, the straight

length could be omitted.

Typical of lines installation on double suction pumps


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For the pipelines that are connected to threaded part of machines

(service line, seal lines, vent or drain lines) a flanged connection

between the machine and the block valve of the line, shall be foreseen.

When the connection of a temporary strainer is needed, this will be

installed as near as possible to the machine, between suction nozzles

and the first block valve. The route of the line and the supports, shall

allow the disassembly of the filter.

5.5.4.2 Compressors

In order to reduce vibrations, suction and discharge pipes reciprocating

compressors shall be positioned on the ground and hook up on it, as

near as possible to the machine, according to the thermal expansion

requirements.

In the case of lines involved in chemical washing, appropriate

connections or tube pipes to the machine, will be provided. The relevant

supports will be provided for the line filled with water or temporary

supports will be provided.

5.5.5 Storage Atmospheric Tanks

As far as the installation of these tanks is concerned, an adjustable

connection has to be provided.

The suction pipes from a tank, have to be installed to the minimum

allowed elevation in order to avoid the forming of pockets on the line

that could interfere with the operation of the pump and prevent the

entire emptying of the connected tank.

The firewater, used to convey water mixture and foaming-agent liquid,

have to be installed within the basin and on the ground to reduce as

much as possible the damage of the pipelines in case of accident.

The pipelines jointed to the distribution manifold nozzles of products

from/to tank, have to be gathered as much as possible in a manifold.

The relevant valves have to be positioned on the addle of the service

platform. The distance between centers among pipelines of manifold has

to allow the access for the assemblage and for the maintenance of the

relevant valves.


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5.5.6 High Pressure Storage Vessels

For security reasons, only the pipelines directly connected to the

relevant high pressure storage vessels, could be installed in the storagearea.

The above mentioned pipelines have to be suitably supported

considering the requirements of expansion/contraction and vibrations.

Normally the connection to the vessel is carried out providing a single

line placed at the bottom of the vessel.

This single line has to be used for all the operations: filling, emptying

and drainage.

When, for specific operating conditions, the Process requires a returning

vapor line, this will be connected at the edge of the vessel. The distribution pipes of the product from/to the vessels have to be

grouped, in a manifold that, for security, has to be placed outside on

the partition wall.

To reduce at minimum the possibility of dripping, the threaded

connections must not be used inside the pipelines and the quantity of

the flanged connections has to be reduced to the minimum.

Concerning inlet and outlet piping, a drainage has to be provided. This

has to be placed after the first block valve in the length outward from

the manifold; the relevant discharged inflammable vapors shall be taken

out to a safety place.For the conditions of assembling execution, see the typical examples

shown in pictures 4, 5, 6 and 7.


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Fig.04.- Typical Arrangement of Vessel Piping Layout


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Fig. 05 – Typical Model of Piping Assembling


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Fig. 06 – Details of Piping Assembling


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Fig. 07 – Typical Models of Fire Fighting Assembling


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5.5.7 Valves and Instruments

All of the valves which require operating intervention must bepositioned in a way so that the hand wheel is accessible from the

ground or from a platform. If it is positioned higher than 2.1m (hand

wheel axle) from the operating level, they will be operated by means of a

chain (this does not apply for valves which are 1 ½” or less). If the

valves are positioned under the operation levels, the hand wheel

extension will be brought to 1.2m over the operation levels. All valves up

to 1 ½” are considered accessible, for operation made from vertical fixed

ladders.

For the block valves positioned at the header branches, operation

devices are not foreseen.

The control valves must be accessible from the ground or from

platforms. When they are mounted on platforms, the control valves will

be positioned on the inner side of the handrail.

The safety valves must be accessible from the ground or from platforms.

When mounted on platforms, safety valves will be positioned on the

inner side of the handrail.

The valve for pressure instruments must be accessible from the ground,

from platforms or from fixed vertical ladders. If positioned at a height

higher than 3.6m from the ground, they will be accessible by portable

vertical ladders.

The temperature instruments will be accessible from the ground,

platforms or fixed vertical ladders. If positioned at a height higher than

3.6m from the ground, they will be accessible by portable vertical

ladders.

The valve for flow instrument will be accessible from the ground,

platforms or fixed vertical ladders. If positioned at a height higher than

3.6 from the ground, they will be accessible by portable vertical ladders.

If positioned on a pipe-rack, no fixed installation for accessibility will be

foreseen.

The glass level gauges will be accessible from the ground, platforms or

fixed vertical ladders.

The displacement or differential level gauges will be accessible from the

ground or a platform. If positioned with a bottom edge at a height

higher than 3 m from the ground, they will be accessible by a fixed

vertical ladder.


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5.5.8 Installation of Piping Parts and Accessories

5.5.8.1

General

The piping will be arranged in a way which permits the removal of

pieces of equipment or parts of it which may require maintenance

operation (pipe bundle of the exchangers, pumps, etc.) without

removing the block valves or all pipe connected to the equipment itself.

The hot piping will be arranged or insulated so that the heat radiation

conditions within 40°C of the neighboring equipment do not damage the

surrounding equipment.

The piping will be gathered into groups whenever possible. These

groups will have different elevations in order to permit deviations,change of route and perpendicular intersections of the pipes without

interference among them.

The piping will be designed so that liquid and gas pockets are avoided.

When this is not possible, there will be a vent for the gas pockets and a

drain for the liquid pockets.

Dead legs on the piping will be avoided for pipes which transport

caustic products, acids, liquids which may solidify or gas which may

form a corrosive condensate.

There will be no process piping inside the control room. No steam or

condensate piping will be inside the electrical substation.

5.5.8.2 Installation of Gate Valves and Globe Valves

At the inlet and at the outlet of safety valves, the valve stem will be

always oriented horizontally.

On pipes containing dangerous liquids, the valve stem will never be

installed below the horizontal level.

On cryogenic service pipes, the valve stem will be oriented vertically or

at 45° from vertical.

Chain for valve handling shall not obstruct passage areas. The chain

will extend to 900 mm above the operation platform

All Car Seal Open (CSO)/ Lever Operated (LO) gate valves will be

installed with horizontal stem, in order to avoid that, in case of failure,

the wedge should fall due to the force of gravity, and obstruct the fluid

flow.


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5.5.8.3

Check Valves Installation

Clapet check valve will be preferably installed horizontally. Vertical

installation will be in the case of upwards flow.

If a check valve is installed in such a way that when it closes liquid

accumulates in the pipes, a drain is required upstream from the valve.

5.5.8.4

Plug Valves and Ball Valves Installation

On the plug valves, and ball valves chain operation, with or without

extension, will be allowed only in exceptional cases.

The position indicator of gear-operated plug and ball valves shall bevisible from operational floor.

5.5.8.5 Butterfly Valves Installation

In the butterfly valves installation, it is necessary to verify that, during

the operation, the butterfly valve does not interfere with element inside

pipes (thermo-well pips, line reduction, internal coating).

If butterfly valve is not “Threaded connection type”, additional couple of

flanges will be installed when, downstream line, it has to be removedduring maintenance operations.


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Fig. 08 – Valves With Stems in Vertical Position


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Fig. 09 – Valves With Stems in Horizontal Position


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Fig. 10 – Typical Example of Battery Limit Installation (placed on theground)


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Fig. 11 – Typical Example of Battery Limit Installation (Placed on Pipe-

Rack)


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5.5.8.6 Vents and Drains

Piping will be designed in order to avoid gas and liquid accumulation.

Otherwise:

On all liquid accumulation, drain valves will be installed.

On all gas accumulation, valved vents will be installed.

Vent diameter: 3/4″

Drain diameter:

3/4" for 3/4" to 8″

1” for 10" or larger lines.

An exception is made for lines containing heavy products, where the

diameter will be 1” minimum .

For vents and drains installed on high pressure lines or hydrogen lines,

the first connection nipple to main line will be SCH. 160 min.

Drains installed on hydrogen and LPG lines will be designed with a

double valve.

5.5.9 Control Valves

For control valve installation, sufficient clearance for actuator

accessibility and/or removal will be provided.

The plug will always be removable from the bottom of the valve

and the minimum clearance shall be agreed with the Instrument

Section.

The actuator’s diaphragm will be accessible from the top of the

valve and a 300mm clearance will be provided.


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Control valves will be positioned preferably with the stem in a vertical

position. In special cases, the stem may be orientated up to 45°from the

vertical axis. The stem may never be orientated horizontally or

downwards.

In the control sets, a valved drain will be provided between the first

block valve and control valve.

5.5.10

Safety Valves

Installation criteria

The safety valves will be installed in accessible areas in order toensure operability and disassembling.

Safety valves will preferably be installed vertically.

The installation of these valves in a dead stretches of pipe (e.g. at

the end of horizontal pipes where normally there is no fluid flow),

have to be avoided.

Valves discharging into the atmosphere will be located at the

highest point of the line on which they operate. Valves

discharging into a closed system will be located at a minimum

distances from the header to which they are connected.

Inlet line

The safety valve inlet line will be vertical and as short as possible;

fittings used will be kept to a minimum to minimize the pressure

drop.

In order to reduce mechanical stress on safety valve and on

relevant inlet lines, it will be necessary to take into consideration

the reaction forces caused by valve opening, especially in the case

of discharge into the atmosphere.

A proper analysis of such forces and relevant effect on valve and

connected piping will be made applying the calculation criteria for

such forces as per ANSI B31.1 and per API 520.

Gate valves will be installed with horizontal stem in order to avoid

any failure, falling of wedge due to the gravity, and to obstruct the

fluid flow.


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In case of joint assembly of a main safety valve and its spare,

block valve on the inlet and outlet lines will be installed creating a

system which does not allow the block valve to be closed on the

main safety valve without first opening the block valve on thespare safety valve, or vice versa. This system can be obtained by

mechanical interlock or using valves with padlocks.

For safety valves that operate at a temperature below zero degrees

Celsius and that discharge into the atmosphere, it is necessary to

avoid the formation of ice and condensation in the valve plug, due

to air humidity. For this purpose the safety valve will be installed

with the last part of the inlet line not insulated. In this case, the

not insulated part will be long enough to prevent reaching dew

point in the valve; otherwise the safety valve must be heated

(using steam or other proper means).

Outlet line – Discharge into the atmosphere

When a valve discharge into the atmosphere the outlet line shall

be directed upwards for gas discharge, and downwards for liquid

discharge.

For dangerous fluids, if a safe location discharge is expressly

required on the P&ID, the outlet pipe will be raised 3 m above any

walkway situated within 15m.

For those fluids for which a safe discharge location is notrequired, the outlet pipe will be oriented towards an area where

the passage of persons is not foreseen

Outlet pipe of safety valves discharging into the atmosphere will

have a 10mm diameter hole in the bottom to drain condensate or

rain water, if any. In case of dangerous fluids, the said hole will

be connected by piping to a safe area or to the sewer.

Outlet line – Discharge into a closed system

Safety valves discharging into a closed system will be installed atthe higher level than flare header, so that safety valve outlet line

is always sloping towards the header; the intake will be on the top

header, oriented at 45° in the flow direction. Horizontal intakes

will be allowed when the safety valve discharge pipe diameter is at

least one diameter smaller than of the header one.


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If the safety valve has to be installed lower than header, a ¾”

valved drain line should be provided, at the minimum distance

from safety valve outlet flange, discharging, after checking of

process, into a recovery pot where liquid, after vaporization, shallbe connected to blow down header.

For the assembly of block valves on safety valve outlet lines, the

same rules will be observed as for the assembly of inlet line valve.

Special care will be taken in the safety valve outlet lines

arrangement, in order to minimize changes of direction.

Support for the above line will be designed in order to minimize

stress on the valve, taking into account that the line will have to

maintain its position with the safety valve.

5.5.11 Piping Characteristics

5.5.11.1

Line Diameters

Pipes and fittings with diameters of 1 ¼ ", 2 ½" , 3 ½ ",4 ½ " and 5” will

not be normally used. Where such diameters are required for

connections to equipment, the pipe length will be reduced to a

minimum.

5.5.11.2

Flanges and Unions

The use of flanges on pipes will be minimized and anyway limited to:

Connecting lines to equipment;

Connecting flanged elements installed on-line (valves, etc.);

On pipes which have to be removed for particular service and

maintenance.

Unions will not be used on flammable or toxic products lines. In any

case, the use of union will be limited to utility lines, 1 ½” or smaller

diameter and when the line rating is not larger than 600#.

Flat-faced flanges (FF) will be used for cast iron valves and/or

equipment nozzle joints.


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5.5.11.3

Bends

Changes of direction will be made by means of elbows (forged, cast or

mitred) or bent pipe.

Elbows will be long radius type (R=1.5D) if not otherwise specified.

Miter bends will be made with 3,4 or 5 elements.

For changes direction, bent pipe can be used with a bending radius

longer than 1.5 times the pipe diameter, in particular, this solution will

be adopted for slurry lines, pneumatic transport lines, pigged lines,

utility lines with 11/2” or smaller diameter, (e.g., steam tracing, utility

lines of equipment, etc.).

5.5.11.4

Diameter Reductions

To reduce piping diameter, reducers or reducer nipples, weldedolet and

similar will be used; reduction flanges will be used only in exceptional

cases.

5.5.11.5

Branches

Branches will generally be at 90° and will be made with “T” pieces, pipe

to pipe branch connection with or without reinforcing plates orweldolets.

Pipe to pipe branch connections (with or without reinforcing plates),

with an angle smaller than 90°, will be used only for flow

requirements(slurry lines, safety valve discharge on flare headers, etc.)

Reinforcing plates will be defined as per ANSI B31.3 standard.

5.5.12

Steam Distribution Network

Where possible, the steam header will be positioned at one end of thepipe-racks and sleepers, for the installation of thermal expansion loop,

if any.

Steam headers will be blind flanged, (never with cap), in order to allow

the cleaning. When block valves are provided on header branches, they

will be installed on the upper horizontal length of pipe to allow the line

to drain on both sides.

On the lowest points on the end of steam header, pots will be provided

with steam traps.


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5.5.13

Utility Stations

Service hose stations for water, air, steam and nitrogen supplies (last

one only where expressly required by the design specification) will be

located in the following areas:

Process and utilities production areas

At ground floor; hose stations will be arranged to reach all equipment or

pipes concerned, by means of 15 m hose length.

On structures; hose stations will be arranged to serve all the floor. Thewater hose station shall be limited to the first floor.

On fractionate columns; hose stations will be provided on all manholes

platforms and on the highest platform, with the exception of water.

For vertical structures and vessels, in general, utilities stations will be

installed on all floors.

Off-site area for storage and loading

Hose station will be provided in pumps room, in tank trucks and/or

railway loading area and in waste treatments area

5.5.14

Instrument Air Distribution

The instrument air distribution network will be completely separated

from the service air network; use will be only for plant instrumentation.

For each utility branch from the header, a block valve will be provided,installed at a minimum distance from the header.

Threaded piping instrument air distribution network shall be provided

with assembly joint by unions on 11/2” or smaller lines, and flanges on

2” or larger lines, to be installed about every 12m length of straight pipe

and every two changes of direction.


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APPENDIXNotices on ferrous materials, used in the

Industrial Plants

I. Carbon Steels

The carbon steels are considered the alloys of iron and carbon usually

containing about from 0.02 to 1.2 % C and with the percentage of Mn

from 0.25 to 1% and further quantity of other e

5. piping department.pdf

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