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Equipment Piping Arrangement


1. General

When real estate is scare and where piping and pipe supporting structures are routed close to equipment, piping should be arranged such that full access is provided for maintenance and removal or replacement of the equipment can be done with minimum dismantling of the piping. Where required, removable pipe spools should be provided to facilitate the removal of equipment.

Pipe routing and supports near static and rotating equipment should be arranged such that forces and moments induced by piping on equipment nozzles should not exceed the values specified in the Piping Stress Analysis required by Company standard.

Control valve assemblies should, where possible, be located at deck level or on first platforms level above deck, unless otherwise required for process reasons.

Piping and structure should be arranged to allow clear access for installation of any lifting equipment and any mechanical handling activities. All operations and maintenance access should be in accordance with supplier recommendations.

2. Pumps

Pump suction and discharge piping should be arranged to allow the casing sections of the equipment to be removed with minimum disturbance on any connecting piping.

When more than one pump is installed on a common suction and/or discharge header, spectacle blinds or other positive isolation facility should be installed in order to isolate each pump for maintenance purposes. In all cases the positive isolation should be installed in accordance with information shown on P&ID’s. Particular attention should be paid on cryogenic liquid lines on which installation of flanges should be minimized.

For multiple pumps, piping arrangements for each pump should generally be similar in arrangement.

Auxiliary piping should be installed along the base plate and should not extend over the operating floor.

Special attention should be given to ensure the minimum clearance between adjacent pumps is achieved.

Inspection covers, bearing caps, upper halves of casings etc., should be removable without disturbing the piping.

To avoid spillage of hazardous or toxic fluids in the event of a pump being opened, the drain and/or vent connections should be permanently connected to a disposal system suitably arranged for this purpose.

For horizontal suction lines and for pump types with double suction inlets, a straight length of minimum 5 times the nominal line size should be provided immediately upstream of the suction nozzle of the pump (this requirement is to be confirmed by the pump supplier).

Suction piping should be as short and as direct as possible. It should not contain pockets where gas may accumulate. However, if this is unavoidable, venting facilities should be provided.

A strainer should be installed in all pump suction lines. All screens and filters should be sufficiently reinforced to prevent their failure and subsequent entry into the pump. Strainers should be designed or selected to suit the service.

There should be sufficient space for removal of strainer element in pump suction line. If a cone type temporary strainer is provided on the P&ID, then removable spool should be provided to facilitate removal of the temporary strainer.

If the suction nozzle of a pump is smaller in size than the connecting piping and a reducer is required in a horizontal line, it should be eccentric and installed with the top flat.

Requirements for suction, discharge piping straight length should be as per vendor’s requirements. Special attention should be done for retractable pumps to provide enough space for maintenance.

3. Compressors

Compressor piping requires special attention, and the effects of vibration and pressure surge should be considered to prevent fatigue failure. The use of spring hangers should be considered, pipe support arrangements should be in accordance with the stress calculation.

The following table recommends straight length requirements applicable to compressor inlet and outlet piping and the minimum requirements should be confirmed by the compressor vendor:

Type of Compressor

Inlet Opening Preceded By

Minimum Straight Length Before Inlet

Centrifugal compressors, axial compressors or combinations thereof and compressors with interstage side stream inlets

Straight Pipe

3D

Elbow

3D

Reducer

5D

Valve

10D

Flow Device

5D


Type of Compressor

Inlet Opening Followed By

Minimum Straight Length After Inlet

Centrifugal compressors, axial compressors or combinations thereof and compressors with interstage side stream inlets

Straight Pipe

3D

Elbow

3D

Reducer

5D

Valve

5D

Flow Device

10D


For further information on this subject see ASME PTC-10, section 4.3

Piping arrangement should allow removal of temporary strainer without the need to dismantle piping, supports or affect alignments. Removable spool maybe used to facilitate this process.

Inter-stage and discharge piping should have sufficient flexibility under the thermal load resulting from the heat of compression.

A strainer should be installed in all compressor suction lines. All screens and filters should be sufficiently reinforced to prevent their failure and subsequent entry into the compressor. Strainers should be designed or selected to suit the service.

Unless otherwise specified by the compressor vendor, lines between knock-out pots and the compressor suction should be as short as practicable and preferably without pocket between the knock-out drum and compressor.

Suction lines taken from a header should preferably be connected to the top of that header. However, if the suction line is at least one pipe size smaller than the header, a center-line connection to the side of the header is accepted.

The anti-surge/recycle line should be sloped away from the anti-surge/recycle valve, which should be located at the highest point of the system.

Piping should be such arranged to not obstruct any operation, maintenance and mechanical handling requirements.

4. Exchangers

Exchangers should be arranged to facilitate operation and maintenance requirements, in particular cleaning requirements. The piping arrangements to each exchanger should generally be similar in arrangement.

Nozzles on exchangers should be positioned so that the best piping layout is obtained without affecting the design capacity of the equipment. 

Piping should be arranged such that:

  • On Shell & Tubes Heat Exchanger: It does not hamper removal of shell and channel covers and the withdrawal of the tube bundle.
  • On Plate-Frame Heat Exchanger: It allows space to pull out the frame and replacement of the plates.
  • On Printed Circuit Heat Exchanger: It allows space above the equipment for its entire replacement.
  • On Air Coolers: It allows the replacement of the motor and belt without piping disconnection.
  • On Electrical Heaters: It does not hamper removal of electrical head and the withdrawal of the tube bundle.

It may be necessary to provide a pipe spool, elbow, or other removable pipe piece between the block valve and the equipment nozzle.

Drain and vent nozzles on heat exchangers should be provided with valves and blind flanges.

Cooling water piping should be arranged such that coolers or condensers remain flooded in the event of loss of supply.

5. WHRU

Piping should be arranged such that it does not does not hamper removal of WHRU bundle. It may be necessary to provide removable spools between the block valve and the WHRU connections to allow the maintenance.

Accesses to observation windows and instrument connections of the WHRU should be provided.

6. Vessels

The piping designer should coordinate the piping requirements with the equipment designer to achieve optimum nozzles position and orientation.

For ease of operation and maintenance, vessels that are grouped together should have their platforms at the same elevation with interconnecting walkways. The number of stairways and/or ladders to the platforms should be determined in accordance with statutory regulations to meet safety requirements.

Vessels that are grouped together should, if practicable, be elevated such that their level gauges can be read from one common level.

Where possible, block valves should be located directly against the vessel nozzles. Piping should be arranged and supported such that spectacle blinds can be easily installed for maintenance purposes (vertical orientation) as shown on P&ID’s.

Elevation of manways on the top and bottom of vessels should be defined on a case by case basis. Manways should be orientated such that the manway cover opens away from access approach.

7. Vessels Trim

Vessel trim is defined as valves and piping components directly connected to a vessel, which do not form part of a piping line. Typically, vessel vents, drains, standpipes and various types of instrument connections.

Vessel trim design and materials are the responsibility of the piping section. A piping line number or numbers should be allocated for each vessel trim, and trim materials should be selected according to the designated piping class.

7.1 Level gauges

Level gauges are devices allowing visual observation of actual level through a glass plate or tube.

Depending on equipment design, level gauges can be either supplied as part of the equipment (not part of piping design) or mounted externally to the equipment and connected to the equipment (piping).

Level gauges should be placed in such a position that the level indicated will be visible from deck platform level or access ladder. The level in the gauge should be visible from the location where the same level is measured by another instrument.

Clearance should be provided for illuminators or back lighting when fitted.

7.2 Stand pipes

A stand pipe should be used when 2 or more Level gauges are requested in same area.

Stand pipes should be considered as part of the process piping and should be in accordance with the relevant piping class.

The minimum nominal size of the stand pipe should be 3” and the connection to the vessel should be 2” flanged connection.

Where level gauge standpipes are installed on equipment operating at elevated temperatures, flexibility should be provided considering differential expansion when isolation valves are closed.

8. Allowable Nozzle Loads

Forces and moments induced by piping on nozzles of equipment should not exceed the values stated in the various standards as specified in Piping Stress Analysis per Company standard.

For specific cases where such maximum allowable loads are not defined, the manufacturer’s standard requirements should be met.



Tags: Piping Arrangement Equipment