Table of Contents

  1. Introduction
  2. General
  3. General Safety
  4. Lines
  5. Valves
  6. Heat Exchangers/Reboilers
  7. Pumps and Compressor
  8. Vessels/Columns
  9. Furnaces/Boilers
  10. Relief System
  11. Electrical
  12. Instrumentation
  13. Civil/Structural
  14. Attachments

1. Introduction

The purpose of this document is to lay down a review procedure to ensure that the desired level of quality for the creation of a piping 3D is carried out in the engineering office and that sound design criteria for operability, safety and maintenance have been observed.

This check list may also be used for the recording of the check, appropriate space is left for any comments against a checked item in column “remarks”.

Additionally the form “Internal 3D Model Review” (see Attachment 1) and the form “Approved 3D Model Revisions from Internal 3D Model Review” (see Attachment 2) may be used for reporting purposes.

2. General

Check if “Interference Checking” facility has been run, if so, ask to see a printout of the report.

Check the 3D model against the latest issue of the plot plans, engineering and utility flow diagrams and line tables.

Follow the line up systematically and pay strict attention to details since many accidents are caused by seemingly minor items.

Mark on the engineering flow diagram all the lines, fittings and instrumentation which have been checked.

Make sure that when a modification, addition, elimination or reduction is considered, that is suits its purpose, is practical and also economical. When is doubt consult others.

Use this procedure for a number of items which can not be shown on diagrams. Please note that the checklist does not pretend to be complete and under no condition it shall overrule sound judgment.

Check that the color code has been used correctly.

Check if construction can build the unit(s) economically as designed.

Check that start up and shutdown problems have been considered and drain and let-down facilities have been provided.

Check the accessibility for operation, maintenance with mobile equipment and inspection.

Check location of future equipment.

Check location of drop out areas.

Check platforms and ladders.

Check that access ways and roads provide ample head room for vehicles, mobile equipment, etc. required for efficient and safe construction, operation and maintenance of the plant.

The policy of access to valves, blinds, manways, instruments, etc. shall been established during 3D model creation. Check 3D model for consistency of approach.

Package units are not normally modelled in detail and are usually show as a block. Ensure adequate space is available for access and for removal of components of package unit.

Check location of particularly noisy equipment, valves, etc. in relation to the frequency of visits by operating and maintenance personnel to the area.

Check the space required around fired heaters for soot blowing and decoking and clearance for burner removal.

Check that air fine coolers can be installed or handled during maintenance of plant by means of a mobile crane.

Check that adequate clearance and maintenance access is provided for plug removal tube cleaning, motors, V-belts, fans.

The 3D model shall also indicate junction boxes, cable trays and trunks, switch gears and power stations, control room, local panels, analyzer houses.

Check at final stage the package units, if vendor information has been included in the 3D model (use certified vendor drawings of lay out and detailed piping showing all instruments and local panel).

3. General Safety

Check that fire hydrants are not positioned at the ends of, or in the line with the ends of, horizontal vessels.

Check elevated equipment’s and platforms for the proper escape routes. Ensure unobstructed and short escape routes at grade.

Check that ladders and staircases have been installed on the outside of structures. Are staircases provided with turnaround landings?

Does escape traffic have to pass through structures? Check companies and/or governmental regulations for safety.

Check that remote shutdown and valve closing devices are installed at safe locations. Check that equipment concerned can be seen from these locations.

Check for “chimney gasp” between platforms and/or table tops.

Check that safety showers and eye baths are located near equipment containing aggressive chemicals (e.g. caustic, ADIP, MEA, HCl, h4SO4, etc.).

Check accessibility of the unit for mobile fire-fighting equipment and rescue work.

Avoid head bumpers, shin splitters and tripping hazards.

Check that emergency/smothering steam header block valves are at safe distance from protected equipment (e.g. in hydrogen service or near fired heaters). A steam header block valve station could be fire shielded, if required, by brick or concrete wall.

Make sure that operators manipulating drain valves can see the emerging affluent. The required level gauges shall be visible and funnels must be provided.

Check that water trapped in goosenecks cannot be displaced by hydrocarbons.

Check that utility stations have been provided, including those at the main operation platforms, e.g. for the connection of steam lances.

Check barometric seal height of vacuum for liquids other than water. Ensure that the liquid can be drained as well. Important for the design of the structure elevation.

Check that platforms have been provided at places where work is expected between maintenance stops.

Check that steam exhaust cannot cause personnel hazards either from spraying droplets of hot water or causing icy or wet surfaces.

Check that steam rings are foreseen at flanges in overhead lines of thermal cracking units and for lines in hydrogen service.

Be alert for equipment supported on continuous platforms when sections of these platforms are supported on structures subject to different thermal expansion.

Check that continuously operating vent stack are higher than the highest nearby structure (within a safe distance).

Check the location of liquid relief valves, since its actual height influences the required set pressure.

Check the location of toxic gases (h4S, VCM etc.) monitoring points if applicable.

Check that drains of light hydrocarbons (propane, butane) are protected against freezing (e.g. double valves).

Check that firewalls have been located correctly.

Check that levers of plug-and ball valves are not hampering operators on walkways or platforms, levers shall move in the same plane as the piping lay out.

Check that steam for purging of lines and equipment (e.g. snuffing steam, emergency steam) is dry, provide automatic trap stations with drain assembly upstream of last block valve in steamline.

Check that process ventlines are routed and oriented to safe locations, (3 meter above highest platform), watch nearest platforms and prevailing wind direction.

Check location of manholes with platforms and ladders in respect to safe escape route.

In case of location of water cooled equipment at high elevated platforms, check if the normal cooling water pressure is suitable for this duty, otherwise a booster pump shall be installed.

To prevent vacuum in equipment located at high elevations, due to siphon operation of the fluid, install a vacuum breaker to suck in air or a process gas.

4. Lines

Check that piping entering and leaving the unit is logically grouped together.

Check that valves, blinds, flushing/drain and instrument connections are properly located. Check especially so called manifolds and large control valves. Check in cases where spades are used ISO spectacle blinds, that piping system are flexible enough to insert these spades.

Check that piping subject to thermal expansion is anchored at plot limits.

Check elevation of overhead piping and horizontal clearance of access and/or walkways.

Check that start-up/circulation lines are short.

Check that dead ends have been avoided. Check if system can be flushed and drained.

Check that vapor lines (inclusive steam) branch off from the top of main lines. Prevent pockets in vapor lines. Keep lines sloping to a drum or install drainpoints (driplegs).

Check that piping subject to thermal expansion is flexible enough. Are supports adequate?

Check if nozzles and branches on expanding piping are not installed near obstructions, support beams, etc. (to avoid ripping off). Are these lines properly anchored. Are stresses on equipment nozzles within limits.

Check for pockets in vapor lines where condensation may occur. Has external heating been applied on those pockets which can not be avoided?

Check that long lines attached to small bore nipples are properly supported to prevent breakage due to vibration.

Check that lines do not pass through table top, but run alongside. If impossible group lines together passing via a sleeve.

Check that dead end sections have been avoided (e.g. in water lines).

Check that piping has been designed to permit easy drainage, venting, flushing, testing, maintenance, insulation, painting.

Check position of eccentric reducers. Normally straight side on bottom of horizontal lines except in pump suction lines where vapor pockets may cause calibration in the pump.

Check that compressor suction lines slope toward knockout drum.

Check that small bore cooling water lines branch off from top of the header. (This to prevent plugging).

Check that stripping steam lines are short and horizontal or sloping from the last valve.

Ascertain that two phase flow vertical piping has been checked for flow stability.

Check that hydraulic (water) hammer conditions have been checked.

Check that all lines have been properly numbered.

Check that high temperature and special material lines have been stress analyzed.

Check that gas is prevented from entering cooling water system.

Check absorber gas feed inlets for pockets near the inlet to avoid absorbent in the gas line.

Check that piping with instrument connections has been laid so that these connections are easily accessible. Check if necessary platforms and walkways have been provided.

Check anchoring of piping discharging to atmosphere. Pay special attention to screwed piping.

Check that vacuum equipment steam jets has been hooked up directly to the steam mains, i.e. without any intermediate connections which may suck in air. This is not applicable for vacuum pumps.

Check (for the same reason) that venting of the gas compressor suction piping has been avoided.

Check all coordinates on piping for correct configuration and clearances.

Check that service stations have been properly located. Design also for winterizing (water/steam/air in one insulated box).

Check for rotary equipment that suction and discharge piping are properly supported.

Check clearance between piping and structural steel with fireproofing.

Check that thermosiphon reboilers have been located such that minimum pipe distances and equal vapor distribution are achieved.

Check required straight piping runs to distributor piping in distillation columns. Only in vertical plains are bends allowed within this straight run.

If a vent is required on an exchanger for periodically purging of noncondensable vapors, this vent valve shall be accessible, vent plus line shall be shown on 3D model.

Check piping arrangements on shell and tube side of exchangers carefully for correct flow of fluids and proper operation of exchangers.

If symmetrical piping hook up is required to exchangers, airfines or double suction of pump, check this carefully.

Keep length of suction piping to pumps to a minimum and prevent pockets.

Check location of break flanges on piping at shell and tube exchangers and aircoolers to facilitate bundle removal.

Check that number of passes in a heater are shown and if necessary check that piping is symmetrical.

Check that location of isolating valves and valves of snuffing steam and emergency steam are at 15 meter distance from the heater at grade and accessible.

Avoid dead legs in heavy fuel oil lines and waste gas lines.

In case of steam jacketed sulphur lines provide T-pieces or cross pieces at the end for cleaning the sulphur lines by rigging.

Check location of relief valves and their good accessibility for servicing.

Check location of local panels for safe operation and good accessibility.

5. Valves

Check that valves in overhead pipe tracks have been avoided to the maximum extent.

Check that chain operated valves have been avoided where possible.

Check that all valves are installed with the steam installed with the stem pointing upwards or horizontally.

Check that hand wheels are easily accessible for operation and yet not obstructing walkways or platforms.
Check also steams, especially in open position.

Check that valves for emergency operations are workable grade level.

Check that valves that need frequent attention are easily accessible.

Check valves in vertical lines for possible water traps.

Check when reduced port valves are installed, that piping is self draining on both sides of the valve.

Check that hot oil block valves are well accessible in view of fire risk.

Check that control valve assemblies are located at ground level or on first platform (except when required otherwise for process reasons).

Check that installation of valves outboard of elevated platforms has been avoided.

Check that valves or double block and bleeders have been installed in utility connections to process equipment and lines.

Check that spring loaded and/or extra block valves have been used where valves may freeze-up when draining or sampling.

Check that process vents and drains are shown.

Check location /installation of check valves in ditch. lines of pumps or near connection of lines, for example connection of condensate lines from traps to condensate collecting header near to the header.

Check levers of plug-or ball valves, these shall not obstruct walkways, platforms etc. Levers shall move in the same plane as the piping lay out.

6. Heat Exchangers/Reboilers

Check that piping arrangement is acceptable with respect to the removal of shell and channel covers as well as the withdrawal of tube bundles.

Check whether bundles can be pulled and lowered safely from platforms and stacked arrangements (obstructions, hydrants).

Check stacked heat exchangers for the possibility of oil spills on hot equipment beneath it, especially during maintenance work.

Check accessibility to exchangers for maintenance, bundle removal/cleaning, etc.

For a thermosiphon check reboiler check the elevation difference between draw-off pan and reboiler for driving force

If a vent is required on the exchanger for periodically purging of noncondensable vapors, this vent valve shall be accessible. Vent also to be shown on 3D model

Cold fluid enters the exchanger at the bottom and leaves it from the top

Check crane access to airfin coolers for maintenance or construction.

Check symmetrical piping hook-up to several bundles in an airfin cooler or to exchangers in parallel operation. Dead legs in capped headers shall be kept to a minimum or be avoided, use elbow ISO tees at the end of the header. Pockets in outlet piping of aircooled or water cooled condensers must be avoided as well as in the hot vapor bypass lines.

7. Pumps and Compressor

Check that flow in suction piping is as smooth as possible

Check that high points in pump suction lines have been avoided

Check that valving around pumps is logical and operable

Check volumes which must be drained when a filter or a pump needs to be opened

Check that pumps can be safely and easily handled for maintenance

Pay special attention to spading-off possibilities

Check that priming facilities are adequate

Check that facilities have been provided for gradual heating prior to start

Check hookup of suction line on double suction pump. Piping layout to be as follows for side inlet:

  • Straight length from suction flange until bend to be 3D (D = diameter nozzle pipe), no reducer allowed.
  • In vertical pipe reducer, strainer and valve can be installed.
  • For top inlet straight length = 5D if suction line runs in length direction of pump motor and 3D if suction line runs in same plane as pumps impeller(s). Upstream of the bend in the suction line the strainer, valve etc. can be installed.

Check that pump operating under vacuum are provided with high point vents, which are connected via a vent line to the top of suction vessel

For a vertical pumps no straight length is required.

If pump handle liquids with temperatures above auto-ignition, this pumps shall be located in safe-areas (not underneath pipe rack) and widely spaced from other pumps. Good accessibility for fire fighting is required and above pumps a sprinkler system shall be installed

Piping to compressors. Pockets shall be prevented, lines shall be slope to suction drum and suction line shall mostly be steamtraced. Check vendor drawings carefully

Check all flushing, cooling, quenching requirements of pumps and compressors

Check that sufficient space is available for removal of filters from strainers

Suctions lines of pumps to be of minimum length

Check NPSH of pumps

If two pumps are parallel operating the piping hookup at suction and discharge side shall be symmetrical.

  • On reciprocating compressors safety valves must be located upstream of the discharge block valve.

8. Vessels/Columns

Check location of vents as well as direction of outcoming streams

Check positions of drain nozzles. Keep them clear from areas where heavy equipment such as fork lift trucks may work

Check that manways are within reach of hoisting equipment

Check that instrument tappings and local instruments are readily accessible

Check that the lines can follow the expansion when heating up/ cooling down. Pay special attention to supports on hot respectively cold structures. Check free movement of platforms

Check that staircases, platforms, ladders etc. are logically located

Check that the layout of platforms , ladders, piping, relief sets, etc. is in accordance with the specified basis for wind and earthquake load calculations

Check location and elevation of all piping- and instrument nozzles against requisition of equipment and drawing

Check that spectacle blinds or spades are installed (indicated) at the nozzles for pressure test or isolation purposes. Normally required with columns

Stripping steam to the columns shall be dry; install KO pot at grade provided with automatic steam traps and drain valve and provide a minimum distance insulated steamline in vertical run without pockets to the steam inlet nozzle of the column.

Check that sufficient space is available for column erection activities

Check that consideration has been given to loading and unloading of catalysts, packing, internal etc.

9. Furnaces/Boilers

Check that piping does not obstruct observation windows, access doors, header box covers, etc

Check that space is available for tube withdrawal and cleaning

Check that piping at burners is arranged so that insertion/removal of lighting torches and burner guns is not hampered

Pay special attention to safety of fuel system:

  • Check that heavy fuel and LBF system are sufficiently segregated

  • Check that provisions are made to adequately prevent liquid fuels from entering steam and gas system

  • Are locations of flame arrestors, straight pipe length etc. of low pressure and waste gas in accordance with specifications?

Check that emergency/smothering steam valve manifolds are at safe distance. Steam shall be dry. Install upstream of manifold at low point a drain valve and automatic steam trap

Check that dry emergency steam is available

Check that :

  • Branch off nozzles are positioned on top of main

  • Steam line are under continuous slope (no pockets)

  • Sufficient steam traps and drain points are provided

Check that fuel and atomizing steam cocks are within hand reach when looking at the burners through the observation windows

Check that the local emergency shutdown switch is at a safe location

Check that safety logic (for heater start-up and shut-down) is not located below (vertical) furnace. Normally such a logic is located in a local panel at safe distance (15 meter) from a fired heater

One complete burner hookup shall be shown per heater including all instruments and all provisions for safe startup, operation and shutdown of the heater with associated equipment (e.g. fans).

Check final certified vendor drawings for equipment correctness.

Check prescribed safety distances, e.g. for example:

  • 12 meter to catch basins
  • 15 meter to process equipment exclusive airfin coolers
  • 22 meter to airfin coolers

Check that the damper can be operated from grade.

Check that the flue gas oxygen analyzer is located at grade.

Check heater or boiler location for maintenance and construction accessibility and also for decoking, regeneration or soot blowing activities.

10. Relief System

Check that inlet lines to relief valves are self draining into process equipment.

Is its proper functioning not hampered by the nature of the process fluid? The allowable pressure drop across the inlet line of relief valve is limited to 3% of the set pressure (at maximum capacity). If pressure drop is too high, the line size shall be increased.

Check accessibility of the relief valves for maintenance and inspection. Check if relief valves have been installed at proper elevations. Distinguish between valves releasing to atmosphere or relief deader.

Check pressure relief discharging to atmosphere for safe location and direction.

Check that discharge pipe is drainable. If so, does drain not impinge on other equipment? Have measures been taken to avoid freezing of moisture on relief valve seats in low temperature service?

Check tail pipes for adequate support against reaction forces.

Check that the tail end of vent pipe is within the action radius of fire extinguishing equipment. If not, has a snuffing steam connection been provided?

Check that length of piping is minimized for safety relief valves discharging into a closed system.

Check that outlet line from relief is self draining into flare header. Check if connections are made on top of the flare header.

Check that flare lines have no pockets and that they are sloping to the flare knockout drum.

The back pressure on the relief valves (calculated during the design) shall be checked with the actual layout of the flare system.

Check destination of outlets from 1 ”x 1” thermal relief valves to atmosphere or grade for safety.

In case hooked up to the vessel, check if steamtracing is required to prevent plugging.

Check locking devices of the valves at inlet/outlet of the relief valves.

Check that valves with Castell lock system (or other system) are properly installed.

Check that safety relief valves and inlet/outlet lines adequately supported.

Check that tail pipes of relief valves require weather protection cap.

Check that the proper type of the relief valve has been specified, for example in waxy service piston type in view of plugging.

In case of 1 ”x 1” thermal relief valves, the inlet of the relief valve shall be self-draining to the process line, the discharge line can be connected to a collecting header which shall be discharging under slope without pockets to a vessel. Check if inlet and outlet lines of relief valves shall be steamtraced.

11. Electrical

Check that cable trunkings are properly located and not obstructed by equipment etc.

Columns of pipe racks are normally used to install junction boxes for both electrical and instrumentation purposes.

Check that orientation and access is not hampered by location of control valve station, steamtracing stations, utility stations or other piping lay-outs.

12. Instrumentation

Check that all instruments are on 3D model and have been correctly tagged.

Check that instrument cable trunkings are properly routed and in accordance with applicable instrument drawings.

Check that local control panels, main junction boxes, etc. are properly located.

Check location and accessibility for operation and maintenance of all instruments. Mind removable piping on both sides of reactors (swing elbow), here special design is required.

Check straight length of orifice runs.

Check clearance above external displacers for removal of floats.

Check platform clearance around level gauges, control valve stations, relief valve station, especially for Camflex type control valves with bypass.

Show all personnel protection, gas detection points (sniffing points).

13. Civil/Structural

Check that all structures with bracing and pipe racks are shown, inclusive fireproofing.

Check that all plinths for equipment and structures are shown.

Check that all table tops are shown.

Check location of analyzer house(s), if fast loop requirements for correct measurements (samples) will be met.

Check that bracing of steel does not form an obstruction.

14. Attachments

  1. Internal 3D Model Review

  2. Approved 3D Model Revisions from Internal 3D Model Review

  3. Definition of Percentage Completion

Internal Model Review

attachment not available ??

Approved Model Revisions From Internal Model Review

attachment not available ??

Definition of Percentage Completion

The following description is a definition of each percentage complete stage of the piping 3D model. Company practice normal practice is to make 3D model reviews at 30, 60, 90 and 100% completion.



  • Plot Plan Attached to 3D Models
  • Battery limits located
  • All major equipment located
  • Major structure shown
  • Major pipe rack shown

30% Completion

  • Comments from Client BASIC 3D model review incorporated
  • Large bore critical process lines studies on the 3D model
  • Piping studies 15 - 20% complete
  • Location of unit access ways for mobile maintenance and fire fighting equipment shown
  • Comments from Client for operation and maintenance incorporated

60% Completion

  • Comments from Client 30% 3D model review incorporated
  • Ready for Client’s comments for operation and maintenance
  • All equipment located
  • Piping studies 70% completed
  • All large bore process lines and utility mains shown
  • In-line instruments shown for lines installed
  • Instruments on equipment located. Local panels shown
  • Main cable trays installed
  • All structures (concrete and steel), ladders and platforms shown
  • All pipe racks shown

90% Completion

  • Comments from Client 60% 3D model review incorporated
  • All piping shown
  • Safety showers, eye baths or jump-in baths shown
  • Piping studies 100% complete
  • Instrumentation, including cable trays 100% complete. Electrical cable trays 100% complete
  • All major pipe supports located

100% Completion

  • Client’s final comments from 90% 3D model review incorporated
  • 3D model updated to latest issue of PEFS’s, PEUFS’s, line tables, arrangement drawings and final equipment drawings
  • All sprinkler mainheaders shown