UHDE

TRAINING MANUAL – PIPING

Uhde India Limited

GENERAL GUIDELINES FOR PIPING LAYOUT

DOC DOC No. No. : 29040-PI-UFR-0024 Rev.

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CONTENTS

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Cover Sheet

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Introduction

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Piping Plans

2–3

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General Guidelines for Routing

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Drawing Content

3–4

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Main Inputs

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6.0

Suggestions

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App li cab le Rev is io n: Prepared:

Checked:

App ro ved :

Date: First Edition: R0 Prepared: DNL

Date:

Date:

Checked: Checked: AKB

App ro ved : RUD RU D

Date: Fi l e Nam e: C- 24

Date: Ser v er :

Date: VK O: K UMUS 209

PUNE: K UMUS 207

Di r ec ec t or or y: y: PUNE: Re Ref er er \ Pi \ Tr ai ai ni ni ng ng Ma Man ua u al

VK O: O: Re Ref er er \ Tr ai ai ni ni ng ng Ma Man ua u al


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DOC No. : 29040-PI-UFR-0024 Rev.

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INTRODUCTION:

One of the most important aspects of piping design is the arrangement (or layout) of piping. This aspect is not related to the ability of the piping to contain the fluid under design conditions but rather to efficient and safe operation of the plant. The job of a piping layout engineer is like an architect, where he has to use his personal skill, imagination and creative abilities in making layouts. In each case the system of piping arrangement depends upon the particular situation. However, to ensure well laid out piping, logical approach must be made and it is very essential that the layout of the plant is rational and carefully studied by piping engineer. Since piping plans are made area wise, it is important that all aspects are studied together.

2.0

PIPING PLANS:

A piping plan is usually made in 1:33 1/3 scale for Process Units, 1:50 scale for Pipe-racks and Utility Storage Tank Area. Usually floor wise plans are made. Local sectional views are given wherever elaboration is required. Normally a piping plan is prepared in two stages. In the first stage it is called a Piping-Study Plan. A Piping-Study-Plan is basically a conceptual proposal consisting of pipe routings in plans and sections (where necessary) of all pipe lines (2” NB and above) fulfilling all conditions laid down in P & IDs and identifying schematically locations of all control stations, rotameter stations, valves, on line instruments, etc. The piping study plan should necessarily show all platform sizes, locations and elevations required for operation and maintenance of piping/instrument components. Lines less than 50 NB are generally not shown. However, depending on the criticality and extent of small sized lines in a particular unit, lines less than 50 NB may be required to be shown. Usually, the study plan starts with the laying of critical lines first. Critical lines are those which are either of large diameter or having high temperature or gravity lines. The study piping plans along with Isometric sketches is discussed with other department (PE & IC) in order to get their comments at conceptual stage. It also serves following purposes: •

Freeze the equipment locations after piping study satisfying all requirements as far as possible.

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Finalize nozzle orientation and cleats for platforms & ladders associated with equipments.

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Feed data to stress group for thermal analysis of lines.

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Furnish top of foundation elevations & other related data to Civil for design.

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Furnish information to model group for preparation of a scaled model wherever applicable. Preparation of order bill of material for pipes & fittings used by other departments such as IC/EL for finalisation of their cable routings. Piping plans are usually updated after getting comments from other departments as well as from stress group and also after review of model by licenser/client where applicable. Comments are obtained through isometric sk etches The piping plans so frozen can now be used for development of final piping plans.


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Final piping plans is a document which shows the routing of all piping of size 2” and above in plan view with clear cut sections if required. It also shows indicative routing of field routed lines to the extent that clarity permits. These are issued for constructions.

3.0

GENERAL GUIDELINES FOR ROUTING:

Following points serve as guidelines while making a piping plan/study. •

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The lines should be located in neat and orderly manner (in groups or banks wherever practicable)

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The lines routing should permit use of standard fittings as per piping specification.

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The lines should be routed so as to have ease of supporting arrangement.

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The line routing should meet all the process requirements indicated on P & I Diagrams.

Piping should not be located at grade especially in areas where frequent personnel movement or traffic is likely. This is important when choice is to be made between sleepers and pipe rack. Piping should be arranged so as to clear the movement of cranes/hoists, etc. All in line piping components requiring regular attention of maintenance personnel should be readily accessible. There should be adequate clear working space around equipment which require frequent maintenance/servicing. All valves, control valves, instrument should be readily accessible either from grade or permanent platforms. There should be adequate platforms and ladder arrangement for column manways. Piping should be arranged to allow removal of the equipment with minimum dismantling of pipe work. Similarly, all dip-pipes should be removable easily. Pockets should be avoided wherever possible especially while routing relief headers. Hot lines should be routed away from electrical conduits and steam condensate should not be discharged into the ground in the vicinity of electrical conduits.

•

Hot lines should be routed so as to have flexibility.

•

Sample piping should be as short as possible.

DRAWING CONTENT:

Following in general shall be shown on a piping plan but not limited to: •

Plant ‘NORTH’ direction shall be indicated along with a key plan.

TRAINING MANUAL – PIPING GENERAL GUIDELINES FOR PIPING LAYOUT

Uhde India Limited

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All platforms, stairways, ladders shall be indicated. All lines up to NS 6” shall be indicated in single lines, while for size NS 8” and onwards shall be indicated in double lines and to scale. All on line fittings, valves, instrument connections, etc., shall be indicated on the plan. All flanged joints must be shown. Change of piping class should clearly be marked where applicable. Tag numbers of piping items, instrument items, process items, etc., shall be indicated as per P & I Diagrams. Special fittings not covered in piping specification shall be called out.

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Each line shall be designated with the complete designation as per line list.

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Flow direction shall be marked for each line.

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Valves shall be indicated with proper symbols to indicate difference in types, e.g.,Gate, Globe, Non return, Butterfly, etc. Valve hand wheel/ stem shall be indicated in the plan or in the section to indicate orientation. Requirement of extended spindle with/without headstock as well as chain operated valves shall be clearly marked.

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Drain funnels shall be located.

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Utility stations as well as safety showers shall also be marked.

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All equipment shall be indicated as per plot plan showing piping nozzles, instrument nozzles and other nozzles like manhole, etc.

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5.0

DOC No. : 29040-PI-UFR-0024

Centreline elevation or elevation of TOS shall be indicated for each line. All lines should be completely dimensioned. All support points for the pipes to be indicated with a correct symbol such as shoe, guide or anchor. It is not required to give the primary support coding. But if secondary supports or special supports are required then corresponding number/code shall be indicated. Battery limits/match lines shall be shown clearly.

MAIN INPUTS:

Main inputs as required from various departments in order to start the activity of study piping plans are as follows: PE

:

Frozen P & I Diagrams, vendor drawings/catalogue information for pumps, compressors & other package items.

MQ

:

Static Equipment Specifications.

IC

:

Frozen hook up diagrams indicating PI/IC interface.

PI

:

Piping specification, unit plot plans.


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SUGGESTIONS:

6.1

P & I Diagrams



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Line routings must meet process requirements indicated on P & IDs. Sometimes special notes/requirements are put on P & Ids for layout purpose. These are either noted adjacent to the applicable lines or listed under “NOTES” Some of such requirements are as follows: a. Slope for gravity lines (required slope indicated) b. Loop sizes c.

Length of barometric legs.

d. Restrictions on length of piping or on horizontal leg. e. Desired location of valve/control valve assembly, etc. It is important to look for all such notings and piping arrangement should take care of all such requirements.

6.2

Instruments

a. In general all instruments whether in line or on line should be accessible. b. There should be sufficient clearances around instruments for their removal. c.

Orifice Flanges:

1.

These can be located at a convenient elevation accessible by using either a stool or ladder and not necessarily to be accessed from ground/operating floor.

2.

Orifice flanges in liquid lines should preferably be located in horizontal leg of piping. Installation in vertical leg, if necessary, from layout consideration should be checked with IC department.

3.

It is important to consider orientation of tapped holes. Usually orifice-flanges installed in horizontal liquid lines have tapped holes from the sides and differential pressure instrument is mounted below line elevation. There should be sufficient clearance between this pipe and the adjacent pipes so that taps & tubing from sides is possible. Also, there should be sufficient clearance below the line (usually 600 mm) so as to mount differential pressure instrument below the line. This is important when the lines run over sleepers. For dry gas service, taps are usually from top and differential pressure instrument is mounted above the line.

4.

Valves and various fittings, such as, bends, tees, reducers make flow more turbulent which affect flow measurement accuracy. In order to overcome this problem straight lengths are recommended upstream and down stream of orifice flanges. These straight lengths are usually expressed in terms of pipe diameter, such as, 10D, 15D etc., and dependent upon the type of obstruction upstream of orifice flanges. Standard table as applicable for the project is to be used while making pipe routings.

5.

At places where it is not possible to provide required upstream straight length for orifice flanges, it is recommended that the same be discussed with IC.


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Control Valves:

1.

These should be installed in horizontal leg of piping as far as possible. In case a control valve is required to be located in vertical leg due to layout considerations, the same should be discussed with IC.

2.

On-off control valves can be mounted, in vertical leg of piping.

3.

A control valve located in vertical leg of piping, usually require a proper support for its actuator.

4.

Some of the control valves have side mounted actuators and these should be properly looked into for interference while making layouts.

5.

Some of the control valves have design which require removal of internals from bottom. It is important to identify such control valves with IC and sufficient clearance below the control valve should be provided while mak ing layouts. Similarly, clearance above the control valve should also be looked into while routing by pass line or any other line above control valve.

e.

f.

Level Gauges & Level Transmitters:

1.

Level gauges and level transmitters do occupy a good amount of operating space and it is advised that the complete arrangement is studied in detail considering their mounting details, isolating valves and operating area.

2.

At places where level gauge and level transmitter both are attached to a stand pipe, such that centre of float is more or less also centre of level gauge, butt welding tees, if called by piping specification are usually not possible to provide. Usually, half couplings or branches with or without reinforcement are used. It is advised that an enlarged sketch be made and feasibility of various connections be studied. Sometimes, it becomes necessary to increase the stand pipe dia in order to accommodate various tappings around its circumference which are more or less at the same elevation.

Temperature Measuring Points:

1.

All temperature measuring points whether local indicators or transmitters require use of thermowells which are inserted in pipelines. Thus, these points are to be located at easily accessible level and local temperature indicators should also be at easily readable level.

2.

Since thermowells are inserted in pipelines, following points should be kept in mind:

a.

Line size Small dia lines are required to be enlarged for inserting thermowells so that some minimum length of thermowell remains in contact with the fluid. Generally, following minimum line sizes are used for installing a thermowell: At Elbow

Straight Pipe

:

Minimum size 3”

:

Minimum size 4” Some licensers do recommend 6”. This is to be check ed with project specification.


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b. Nozzle Projections Nozzle projection from top of pipe is important so that required portion of thermowell comes in contact with the fluid. In case the projection is more, the length of thermowell which will come in contact with fluid will get reduced and on the other hand if nozzle projection is less, thermowell may hit to the bottom of pipe. Usually, the nozzle projection from top of pipe is 150 mm for uninsulated lines and for insulated lines having insulation thickness upto 50mm. Generally, following table is used: INSULATION THK

NOZZLE PROJECTION FROM TOP OF PIPE

0 to 50 mm

150 mm

51 to 100mm

200 mm

101 to 150 mm

250 mm

3. At elbows, nozzles for temperature measurement should be so oriented that the thermowell insertion is against the direction of flow.

6.3 Valves:

All valves should be located at easily accessible level for ease of operation and maintenance. 1.

Preferred valve hand wheel elevations are as follows:

a.

Vertical stem

Ideal Range:

1150 mm to 1300 mm

Good Range

: 550 mm to 1150mm 1300mm to 1450 mm

b.

Horizontal Stem

Ideal Range

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1050 mm to 1400 mm

Good Range

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600 mm to 1050mm 1400mm to 1800 mm

2.

Valves located with stem vertical are preferred due to ease of maintenance and minimum blockage of operating area. However, accessibility of handwheels should be checked.

3.

Valves can be located with their stems either vertical up or turned up to horizontal position. Valves installed with stem lower than horizontal are not preferred due to higher chances of leakage through gland and stagnant.fluid in the space below casing cover. Usually, a drain is provided in the casing cover when the valve has to be located due to unavoidable circumstances with s tem below horizontal.


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4.

Large size valves (12” and above) are usually gear operated. One should check the orientation of gear box assembly and ensure that the handwheel is on operating side and there is no interference of gear box assemble with any piping or structure.

5.

Motorized valves should be checked for orientation of their actuators. These valves are also provided with handwheels for manual operation and hence it is important to ensure that their handwheels are on operating side and there is no interference of actuator assembly with any piping or structure.

6.

Valves when located more than 2.2 m elevation from operating level due to process consideration are usually provided with chain wheels for their operation. Such valves are located with their stem in horizontal and operated by a closed end chain from operating floor. The use of chain operated valves is recommended only in unavoidable cases and that too for valves 2” and above sizes. Screwed end valves are not used with chain operators.

7.

Valves when located below floor level due to process consideration are usually provided with extended spindles for their operation, such that the handwheels are at operating level.; The extended stem of a valve passes through the floor and usually a headstock is used which guide the stem. It is important to review the location of headstocks from operation point of view and the openings in floor.

8.

Globe valves should be installed so as to close against the pressure.

9.

Locked open valves should be installed with their stems in horizontal plane as far as possible. This is to avoid closure of valve in case plug or disc gets disengaged from stem accidentally. When block valves are used in branch lines at headers, they should be located in horizontal runs, at high points, so that lines will drain both ways.

10. The location of a non return valve whether in horizontal or in vertical leg of piping depends upon its constructional feature and the same should be looked into while making layout. TYPE SW ING CHECK VALVES to top. LIFT CHECK VALVES (Piston or ball lift)

LOCATION Horizontal or in vertical with flow from bottom Horizontal

Some ball lift type check valves particularly lined type permit installation in vertical only with flow from bottom to top.

6.4 Safety Valves:

1.

All Safety Valves should be so located that they can be easily accessed.

2.

Safety Valve inlet piping should be kept to minimum as far as possible.

3.

Safety Valve outlet piping should be self draining to the relief header or other destination. Wherever, this is not possible, PE should be consulted before locating such Safety Valves.


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4. When Safety Valves discharge vapours to the atmosphere, the outlet pipe should terminate at least 3 metres above equipment or any service platform located within a radius of 15 metres of the valve. A 3/8” dia weep hole for drainage at low point of line should be provided. Also the top open end should either be provided with a rain hood or with a 45 degree elbow and open end cut vertically. 5. When Safety Valves discharge steam to the atmosphere, the outlet pipe should terminate at least 3 metres above any service platform located within 8 metres of the valve. Outlet pipe should have a 3/8” weep hole for drainage at low point of line should be provided. Also the top open end should either be provided with a rain hood or with a 45 degree elbow and open end cut vertically. 6. Provision of lifting devices such as davit, chain pulley block should be made for all relief valves weighing more than 45 Kgs. 7. Relief header shall not have pocket. Where this requirement cannot be met., ‘PE’ should be consulted for making provision of a k nock out pot. 8. Safety Vales invariably require strong and sturdy special supports in order to absorb thrust. Also, the branches for inlet to Safety Valves are usually reinforced. Normally, a fixed type of support is provided close to Safety Valve and with this in mind main line should be routed in such a way so as to have enough flexibility.

6.5 Interference:

Utmost care is required while routing the lines so as to avoid interference of piping with other pipes & structures. Following are the general types of interferences noticed: 1. Pipe to pipe This type of interference may occur due to: •

Flanges not considered initially while specifying the distance between adjacent pipes but later on flanged joints added without checking the spacing. Normally, the pipes are spaced in such a way that they permit use of flanged joints but flanges in adjacent lines are required to be staggered. In case flanged joints are required to be adjacent, the spacing between pipes should be checked.

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Insulation thicknesses not considered properly: Sometimes it may happen that lines are hot but they are not required to be insulated. However, accessible portions of such lines are insulated from personnel protection point of view. Hence, it is important to consider insulation thickness of such lines while spacing.

•

Thermal movements of pipes not considered. Sometimes interferences are noticed when pipes move under hot condition. Therefore, for all hot lines, it is important that the spacing be checked considering expected movements of pipes under hot condition. Same logic also applies when cold pull is provided.

2. Pipe to Equipment/Structure/Foundation •

Depending upon plant hazard and fire potential equipments supported on structural steel members, fire proofing is recommended. This is done by providing normally 50 to 75 mm thick concrete layer over structural members. Extent of fire proofing depends


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upon fire potential area and has to be ascertained with PE/Licenser. Thus it is important to check interference of piping with structure considering fire-proofing thickness, if applicable. •

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Pipes running close to equipment should be checked for their interference with equipment after duly considering applicable insulation thickness. Similarly, there may be fire proofing up to certain height, for some of the fire potential equipment such as skirt supported columns handling flammable liquids/vapours, etc. It is important to consider insulation as well as fire proofing thickness when pipes are routed close to such equipment. Foundations of equipment handling corrosive fluids usually require Acid/Alkali resistant lining. This has to be ascertained with PE/Licenser. Pipes running close to such foundations should be checked for their interference after duly considering Acid/Alkali resistant lining. This lining can be as high as 75 mm thick. While routing the lines at Grade level the elevation should be so decided that provision of a drain connection with a valve should be possible. It is recommended that there should be minimum 150mm clearance between drain valve and paving. For all hot lines, thermal movements of t he pipe should also be considered while checking interference with structure/beam/column. For steam lines running on piperack, drip legs are provided and usually they are located close to beams so as to have ease of supporting for small diameter lines connected to steam traps. If not located properly, these drip legs may interfere with beams during thermal expansion of the lines. Nozzles located at bottom of saddle supported equipments, such as shell and tube heat exchangers, horizontal pressure vessels, etc. Should be checked for interference of nozzle flanges with foundation.

6.6 Maintenance/Removal:

1. Piping should be arranged in such a way so as to have sufficient clearances around equipment for maintenance especially pumps, turbines, compressors, agitators, etc. As far as possible, pipe routings should be such that permit removal of equipments with minimum dismantling of pipe-rack. 2. Horizontal casing pumps having inlet and outlet nozzles on top, usually require space in front for taking out impeller shaft. Connected piping as well as supports, if any, must clear this removal area. 3. Shell and tube type heat exchangers require clear space for removal of tube bundles and those with fixed tubes require space for rodding. Similarly, plate type heat exchangers also require clear space for removal of plates. This space requirement for removal of plates may be either at the back or on sides depending upon design. Reciprocating compressors also have requirement of clear space for removal of pistons and piston rods, etc. All such requirements should clearly be marked on study piping plans and piping should be arranged in such a way so as to clear these areas. 4. Pipes should be routed in such a way that they do not hinder the movement of chain pulley blocks,EDT/HOT, etc., provided for maintenance purpose. Similarly, all erection/maintenance openings should be kept clear of piping.


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At places where piping cannot be avoided in clear areas marked for maintenance due to process consideration, break up flanges in line are provided so that portion of this piping can be dismantled during maintenance. 5.

Piping connected to nozzles having dip pipes should be provided with break up flanges so that dip pipes can be removed.

6.

Lines connected to nozzles provided on bolted covers of tanks and vessels to have break up flanges so that bolted covers can be removed with minimum dismantling of piping.

7.

All strainers require clear space for removal of screens. Layout of piping should permit easy removal of screens for strainers.

a.

Y or T Type Strainers They are normally located in horizontal leg of piping with screens removable from bottom. This allows accumulation of solid particles at bottom of screen which is a preferred arrangement. These type of strainers when used at pump suctions required to be rotated about line axis by 45 degree and even in some cases by 90 degree in order to facilitate screens removal which otherwise is not possible due to low elevation of suction lines with respect to grade or paved area.

b.

Conical Strainers These type of strainers require spool pieces having lengths at least equal to the lengths of conical screens for installation in the lines. Normally, conical screens are only procured and spool pieces are provided in piping for their installation.

c.

Basket Type Strainers In these type of strainers, screens are removed from top. Sufficient clearances should be kept above these strainers for removal of top covers and screen elements.

8.

Spectacle blinds and plate type strainers do have projections outside the pipelines. Orientation of such projections should be reviewed from removal and interference point of view.

6.7 General:

It may happen that some of the equipment nozzles as well as Instruments have flange ratings higher than connected piping. All such places should be identified and marked clearly on study piping plans. In case any equipment nozzle is found to have flange rating lower than the connected piping, the same should immediately be brought to the notice of ‘PE’ and ‘PI’ lead engineer. This requires a review of piping specification of connected lines as well as design parameters considered for equipment. 1.

While routing the lines, avoid making use of Non standard fittings. Study the piping specification in detail before starting the layouts.

2.

Generally, Instrument and Electrical cable trays are placed above pipes so that leakages from pipes, if any, do not damage cables. At places, where cable trays are on either side of the pipelines, it is advised that hot pipes as well as lines carrying flammable and corrosive fluids are not placed adjacent to cables.


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3.

On pipe-racks bigger diameter lines should run close to columns as far as possible and small diameter lines in middle portion of the pipe-rack width. This would result in having less deflections of pipe-rack cross beams.

4.

On piperacks having two or more tires, it is preferable to place all small dia lines on one tier instead of distributing on all tires. This is in order to avoid intermediate cross beams for support of lines at other tires except for the tier where small dia lines are placed.

5.

For all high temperature lines running on piperack, expansion loops are generally required. It is recommended that expansion loops be placed symmetrical with respect to fixed points so as to cancel out the forces at intermediate anchors. Also, it is a good practice to place all high temperature lines adjacent to each other so that expansion loops are at one place for all the lines. From the expansion loop consideration, it is preferred that all hot lines be at one end of the piperack width so that width of the piperack is available for expansion loops and such loops are either contained within the piperack width or projection outside the piperack is minimum.

6.

Avoid running lines over building main columns as this would hinder the extension of columns, if required in future. Similarly, lines running on top of the beams with their axis parallel are not preferred, since they may hinder the provision of railings or parapet walls.

7.

All barometric leg piping to be kept straight as far as possible. Offsets, if unavoidable should be made by using 45 degree elbows/bends and number to be kept to minimum. This routing should be discussed with ‘PE’ and agreed upon.

8.

Condensate discharge piping for a closed system should have minimum number of bends. This is to avoid high back pressure acting on traps.

9.

For all saddle supported equipments the choice has to be made by PI regarding one of the saddles as fixed and other as guided. It is recommended that after routing major lines connected to such equipments, fixed saddle should be so selected that vessel expansion favourable act towards absorption of thermal expansion by connected pipelines.

10. When piping is connected to two or more equipments in parallel the arrangement of piping should be symmetrical as far as possible. This is to have same pressure drop in the system when stand by equipments are operated. 11. For all lined piping, spacers should be provided for field adjustment. Generally, the equipments to which lined piping is connected are grouted at site after assembling and erecting the lines. This allows the shifting of equipments to some extent for adjustment purpose. Thus, the location of spacers should be decided after reviewing all the lines connected to such equipments and not each line in isolation. 12. All gravity and slurry lines should be routed without pocket. 13. Expansion bellows are installed in piping where it is not possible to have in built flexibility due to process reasons. It is very important to provide proper supporting arrangement when expansion bellows are used in order to ensure that they are not subjected to thermal movements/loading other than calculated.


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14. Do not look your own battery limit area but ensure that lines continuing further from your battery limit or incoming lines to your battery limit are properly represented by match lines on other drawings also with coordinates and elevations marked. For lines which appear on two or more separate piping plans, it is advised that overall profile be looked into. 17. The choice of eccentric or concentric reducers should be made correctly. In order to simplify the situation following is recommended. I.

All reducers located in vertical legs: Concentric.

II. All reducers located in horizontal legs: Eccentric. 18. Eccentric reducers depending upon the position can be placed with flat side either on top or bottom. a.

Usually, at all pump suctions, eccentric reducers have flat sides on top except for pumps handling slurry where eccentric reducers are placed with flat sides on bottom.

b.

At all pipe rack locations, eccentric reducers are used with flat sides on bottom in order to keep BOP same.

c.

At control valve assemblies, eccentric reducers can be placed with flat sides on bottom.

d.

Eccentric reducers located in slurry lines should have flat sides on bottom.

19. Depending upon the line profile vents and drains are required mainly for: a.

Hydrotesting of lines

b.

Venting and draining of lines during plant start up and shut down.

For hydrotesting purpose, usually, 3/4” or 1” couplings with plugs are provided. There vents and drains are without valves. However, for venting of lines during plant start up and draining of lines during plant shut down vent and drain points are provided with valves. These are to be identified by ‘PE’, while giving comments on Isometrics and are required to be marked on P & I diagrams. Lines handling flammable and corrosive fluids can not be vented or drained into atmosphere just like that. Usually, they are led to effluent collection system and again such cases are to be identified by ‘PE’

6.8 Colum n Piping :

For routing the lines connected to colum ns in Petro-chemical & refinery projects, following may be noted: a.

First decide orientation of nozzle connected to reboiler. This is required so that Reboiler Outlet Piping is as short as possible and also symmetrical, if reboiler has got two nozzles.

b.

Decide tray down comer orientation with respect to orientation of nozzle connected to re-boiler.


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c.

Fix orientation of other nozzles after deciding tray down comer orientation.

d.

Start piping plan from top and move downward.

e.

There should be a change in ladder direction after 6 to 8 m. A long straight ladder with intermediate platforms is not desirable.

f.

Column davit to be located in such a way that ground is clear for lifting the material.

g.

While crossing from one ladder to another the passage should not go crossing the manholes, i.e., there should not be ladders on either side of the manhole.

h.

Exit from ladder to a segmented platform should be from one side only, i.e., ladder should not be located between two segmented platforms at the same level. Passage from one platform to another via ladder is not recommended.

i.

Platforms should be minimum 1000 mm in width and maximum 2000mm.

j.

All lines should run close to columns as far as possible. Lines, if passing through platforms should not cut through toe angles of platforms. Also all these lines are supported by providing pipe cleats to columns at proper orientation and elevation.

k.

Control valve assemblies including valves, safety valves, instruments, etc. Should be located on platforms adjacent to columns and not closer to railing as far as possible. This is in order to reduce bending moment acting on columns due to weight of platforms and piping. All valves/instruments/manholes should be easily accessible from platforms provided. Access to all nozzles from platforms is not

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