Guidelines for Piping Arrangements for Centrifugal Pumps

January 2004

Process Industry PracticesMachinery

PIP REEP004Guidelines for Piping Arrangements for

Centrifugal Pumps

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES

In an effort to minimize the cost of process industry facilities, this Practice hasbeen prepared from the technical requirements in the existing standards of majorindustrial users, contractors, or standards organizations. By harmonizing thesetechnical requirements into a single set of Practices, administrative, application, andengineering costs to both the purchaser and the manufacturer should be reduced. Whilethis Practice is expected to incorporate the majority of requirements of most users,individual applications may involve requirements that will be appended to and takeprecedence over this Practice. Determinations concerning fitness for purpose andparticular matters or application of the Practice to particular project or engineeringsituations should not be made solely on information contained in these materials. Theuse of trade names from time to time should not be viewed as an expression ofpreference but rather recognized as normal usage in the trade. Other brands having thesame specifications are equally correct and may be substituted for those named. AllPractices or guidelines are intended to be consistent with applicable laws andregulations including OSHA requirements. To the extent these Practices or guidelinesshould conflict with OSHA or other applicable laws or regulations, such laws orregulations must be followed. Consult an appropriate professional before applying oracting on any material contained in or suggested by the Practice.

This Practice is subject to revision at any time by the responsible Function Team andwill be reviewed every 5 years. This Practice will be revised, reaffirmed, or withdrawn.Information on whether this Practice has been revised may be found at www.pip.org.

© Process Industry Practices (PIP), Construction Industry Institute, TheUniversity of Texas at Austin, 3925 West Braker Lane (R4500), Austin,Texas 78759. PIP member companies and subscribers may copy this Practicefor their internal use. Changes, overlays, addenda, or modifications of anykind are not permitted within any PIP Practice without the express writtenauthorization of PIP.

PIP will not consider requests for interpretations (inquiries) for this Practice.

Not printed with State funds

January 2004

Process Industry Practices Page 1 of 11

Process Industry PracticesMachinery

PIP REEP004Guidelines for Piping Arrangements for

Centrifugal Pumps

Table of Contents

1. Introduction..................................31.1 Purpose ............................................. 31.2 Scope................................................. 3

2. References ...................................32.1 Process Industry Practices ................ 3

3. Definitions ....................................3

4. General Piping Configuration .....44.1 Typical Arrangements........................ 44.2 Pump Suction Piping ......................... 44.3 Pump Discharge Piping ..................... 5

5. Support of Piping Systems .........55.1 Equipment Allowables ....................... 55.2 Design Considerations....................... 55.3 Cold Spring ........................................ 55.4 Expansion Joints................................ 55.5 Piping Alignment................................ 65.6 Supports ............................................ 65.7 Field Welds........................................ 7

6. Operation and MaintenanceConsiderations ........................... 7

6.1 Accessibility ....................................... 76.2 Piping Vents, Drains, and Gauge

Connections....................................... 86.3 Permanent Inlet Strainers .................. 96.4 Temporary Inlet Strainers .................. 96.5 Warm-up Lines .................................. 96.6 Minimum Flow Bypass....................... 96.7 Self-Priming Pumps......................... 106.8 Pumps Operating in Parallel ............ 10

Appendix – Typical PipingArrangements – Figures .......... 11

Figure 1. End suction, top dischargeoverhung centrifugal pump preferredinstallation

Figure 2. End suction, top discharge overhungcentrifugal pump alternate installation.

Figure 3. Top suction, top discharge centrifugalpump preferred installation

Figure 4. Top suction, top discharge centrifugalpump alternate installation for largediameter piping

Figure 5. Side suction, side discharge centrifugalpump preferred installation

PIP REEP004 Guidelines for Piping Arrangements for Centrifugal Pumps January 2004

Page 2 of 11 Process Industry Practices

Figure 6. Side suction, side discharge centrifugalpump alternate installation for suctionpiping with elbow installed in the sameplane as the shaft

Figure 7. Vertical inline side suction, sidedischarge centrifugal pump preferredinstallation

Figure 8 Vertical inline side suction, sidedischarge centrifugal pump alternateinstallation

Figure 9. Examples of reduction at pump suctionfor side suction pump piping

Figure 10. Examples of reduction at pump suctionfor end suction pump piping

Figure 11. Examples of suction and dischargevalve orientation

PIP REEP004January 2004 Guidelines for Piping Arrangements for Centrifugal Pumps


1. Introduction

1.1 PurposeThis Practice provides guidance for designers in the layout of piping systemsaround centrifugal pumps.

1.2 ScopeThis Practice is a compilation of graphics and narrative guidelines for the layoutof piping for centrifugal pumps. This Practice covers piping considerations thataffect operability, maintainability, hydraulic performance, and piping flexibilityfor centrifugal pumps. It includes typical piping layout drawings for eachconfiguration routinely found in the process industry and considered goodpractice. This document also references other industry standards that apply toinstallation requirements, allowable nozzle loads, and methods of pipingflexibility analysis. This document does not address auxiliary piping (lube oilpiping, seal piping, etc.) or non-metallic piping systems.

2. References

Applicable parts of the following Practices shall be considered an integral part of thisPractice. The edition in effect on the date of contract award shall be used, except asotherwise noted. Short titles will be used herein where appropriate.

2.1 Process Industry Practices (PIP)– PIP REIE686 - Recommended Practices for Machinery Installation and

Installation Design– PIP RESE002 - Allowable Nozzle Loads on Rotating Machinery

3. Definitions

axial stop: Mechanical restraints used to control axial or longitudinal movement of thepiping in one or two directions without providing complete fixation

breakout spool (also known as dropout spool): A short, flanged length of pipeimmediately connected to the pump piping flanges. Lengths vary with the size of the pipebut typically range from 6 inches (15 cm) to 3 ft (1 m). The purposes of this spool are tofacilitate pump installation, allow piping modification to reduce pipe strain, isolate thepump, facilitate commissioning activities such as flushing or blowing lines, and allowremoval of temporary inlet strainers.

cold spring: The intentional misalignment of piping during assembly to produce adesired initial displacement and stress

hangers: All devises used to suspend a piping system and also to support the weight ofthe same. Examples include suspended rods, base-type support units, anchors, etc.Hangers are included in the more general term “pipe supports.”



isolation block valve (also known as block valve or isolation valve): A valve used toisolate a pump preparatory to maintenance

owner: The party who owns the facility wherein the pump system will be used

restraints: All devices used to restrict or limit the free expansion of a piping system andyet support none of the weight. Examples include guides, sway braces, sway struts, andsnubbers. Restraints are included in the more general term “pipe supports.”

short radius elbow: A fitting used to change the direction of the piping system 90°,having a radius equal to 1.0 times the nominal pipe diameter

standard long radius elbow: A fitting used to change the direction of the piping system90°, having a radius equal to 1.5 times the nominal pipe diameter

supports: The entire range of devices used to suspend, support, guide, anchor, andrestrain the movement of piping systems. Examples include hangers, restraints, guides,anchors, sway struts, shock and sway suppressors, etc.

4. General Piping Configuration

4.1 Typical ArrangementsTypical piping arrangement sketches for various pump types are provided in theAppendix of this Practice.

4.2 Pump Suction Piping4.2.1 Pump suction piping should be arranged in accordance with

PIP REIE686, Chapter 6 - Piping, such that the flow is as smooth anduniform as practicable at the pump suction nozzle.

4.2.2 The use of tees, crosses, valves, reduced port valves, strainers, near-run-size branch connections, and short radius elbows should be avoided nearthe suction nozzle.

4.2.3 Suction valves should be full port and of the same size (or larger) as thepump nozzle on condition that net positive suction head (NPSH) marginis available in accordance with PIP RESP001 (see Appendix Figures 1through 4).

4.2.4 The pump suction piping should have a straight run of five pump suctionnozzle diameters between the suction flange and first elbow, tee, valve,reducer, permanent strainer, or other obstruction in accordance withPIP REIE686, Chapter 6.

Comment: Temporary suction strainers, flanges, drains, andpressure indicator connections may be included withinthe straight run suction piping requirement.

4.2.5 The suction pipe size should be larger than the pump suction nozzle orshould be as a minimum equal to the pump suction nozzle.



4.2.6 For horizontal suction piping, eccentric reducers with the flat side on topshould be used to avoid pocketing of vapors in the suction line. For topsuction pumps, the reducer should be concentric (see AppendixFigures 1 through 4).

4.2.7 The last pipe elbow in the suction line to a pump should be a standardlong radius elbow.

4.2.8 For double suction pumps, the last pipe elbow in the suction line to thepump should be perpendicular (not in the same plane) to the impellershaft (see Appendix Figure 3).

4.3 Pump Discharge Piping4.3.1 A check valve should be installed in the discharge line of all pumps in

accordance with PIP REIE686, Chapter 6 - Piping, unless no possibilityexists for a flow or pressure surge (such as water hammer) under anycondition.

4.3.2 The check valve should be located between the pump discharge flangeand the discharge block valve.

5. Support of Piping Systems

5.1 Equipment AllowablesThe support and flexibility of the suction and discharge piping systems should bedesigned to limit nozzle loads to less than those specified in PIP RESE002.

5.2 Design Considerations5.2.1 The design of pump piping support systems should account for all

possible operating conditions. The potential effect of operating upsetsand transients on nozzle loads, internal misalignment, and externalcoupling misalignment cannot be ignored.

5.2.2 All identifiable system thermal or pressure upsets should be specifiedbefore starting engineering and procurement of the pump and design ofthe piping system. These abnormal conditions can result in higher loadsbeing imposed on the nozzles than under the normal operating situationsand can cause coupling misalignment after only one cycle of upset load.

5.2.3 If differential settlement is anticipated, the pump foundation should beextended to provide support for the suction piping.

5.3 Cold SpringCold spring (cold pull) should not be used as a design method to deal withanticipated thermal growth and operational pipe strain.

5.4 Expansion JointsExpansion joints should not be used unless the owner’s approval is obtained foreach expansion joint proposed.



5.5 Piping AlignmentPiping alignment should conform to PIP REIE686, Chapter 6 - Piping.

5.6 Supports5.6.1 General

5.6.1.1 Piping should be adequately supported and controlled to meetthe design requirements of the pump. This removes the staticload, allows identification of piping fit problems duringinstallation, and allows easier removal of the pump formaintenance.

5.6.1.2 Only those supports specified as a result of the piping analysisshould be provided (see PIP RESE002).

5.6.1.3 Piping design requirements should include allowable flangeloadings, thermal growth, etc. These requirements are set by thepump manufacturer, the industry standards, or the owner.

5.6.1.4 The dead weight of the piping and process fluid should beentirely supported by pipe hangers or supports.

5.6.2 Springs5.6.2.1 Spring supports should be designed to provide the required

support for the weight of the pipe, the insulation, and thecontents during operation and hence relieve the load on thepump nozzle and allow free thermal expansion of the pipe.

5.6.2.2 Adding more supports or moving existing supports may benecessary if resonant vibration appears in the piping.

Comment: Spring supports for liquid-filled piping systemsmay be difficult to install because the system isempty at the time of installation and the springdesign load reacts against a liquid-filled system.

5.6.3 Adjustable or Rigid Supports5.6.3.1 Adjustable supports should be used to account for field

variations in installed dimensions and for changes over time.

5.6.3.2 The first piping support next to a horizontal nozzle should be anadjustable support.

5.6.3.3 Rigid supports may be used to limit the movement of a line toprevent excessive deflection.

5.6.3.4 A rigid support is not satisfactory where thermal expansion maycause the pipe to move away from the support.

5.6.4 Restraints5.6.4.1 Restraints should be installed to control deflections caused by

induced loads (such as thermal expansion, wind, etc.) in the



pump piping system, thus avoiding excessive loads on pumpnozzles.

5.6.4.2 Restraints should be used to direct the pipe thermal movementaway from the equipment and into other portions of the pipingsystem that have enough flexibility to absorb the movementwithout becoming overstressed or without overloading otherconnections.

5.6.4.3 A guide should be used to permit only axial movement whilepreventing lateral movement.

5.6.4.4 An axial stop should be used to permit lateral movement whilepreventing axial movement.

5.7 Field Welds5.7.1 The piping design should include a provision for a final piping field

weld to permit piping installation in accordance with the machineryflange fit-up requirements in PIP REIE686, Chapter 6 - Piping.

5.7.2 On larger pipe, the final field weld should be farther away from themachine to allow for ease of installation.

5.7.3 Following the final field weld, the pipe-to-pump nozzle flange alignmentshould comply with PIP REIE 686.

6. Operation and Maintenance Considerations

6.1 Accessibility6.1.1 Piping should be arranged to allow adequate access to the pump without

requiring excessive dismantling of the piping system.

6.2.2 The coupling between the pump and its driver should be easilyaccessible to align the pump and driver.

6.2.3 Pump seal access should be considered because seal failure is the mostcommon cause for maintenance.

6.1.4 Axially split pump casings should not have overhead obstructions.

6.1.5 Radially split pump casings should have clear access to the end of thepump for normal maintenance.

6.1.6 If necessary, access can be provided by designing the piping to beremovable. It is best, however, to design the piping to be self-supportingin a manner that minimizes the need for piping removal during normalmaintenance activities.

6.1.7 The guidelines for accessibility contained in PIP REIE686, Chapter 6 -Piping, should be carefully followed.

6.1.8 Isolation valves should be provided in the inlet and outlet process piping.



6.1.9 Any temporary or permanent strainer should be located between the inletisolation block valve and the pump inlet connection.

Comment: Depending on service, process integrity may requiredouble block and bleed valves on vents and drains.

6.1.10 Block valves requiring attention, observation, or adjustment duringnormal operation should be located within reach from grade or platform.

6.1.11 Block valves used for operation of the system may be chain-operatedwhen the bottom of handwheel is more than 7 ft (2.1 m) above the highpoint of finished surface or operating platform.

6.1.12 Chain wheels should not be used on screwed valves or valves smallerthan NPS 3.

6.1.13 An impactor-type chain wheel should not be used on valves smaller thanNPS 4.

6.1.14 Chain-operated wrenches should not be used on any type of valve.

6.1.15 Block valves used only for process shutdown and located less than(15 ft) (4.6 m) from an access level do not need to be chain-operatedunless they cannot be reached by a portable ladder.

6.1.16 Stems of globe and gate valves with solid wedges should be orientedabove the valve body centerline.

6.1.17 Stems of gate valves with split or double disc-type gates should beoriented vertically upward.

6.1.18 Stems of valves in hot service, such as heat transfer fluids, should be inthe horizontal position.

6.1.19 Sufficient room should be allowed for the operation of handles or leverson valves.

6.1.20 Hand-operated control valves should be located so that they can beadjusted while associated instruments can be read.

6.2 Piping Vents, Drains, and Gauge Connections6.2.1 Vents and drains should be provided in accordance with PIP REIE686,

Chapter 6 - Piping.

6.2.2 Adequate drains should be provided on the piping to perform routinemaintenance on pumps.

6.2.3 Drains should be located at the lowest point in the piping near the pump.

6.2.4 Drain connections should not be placed in angle sections of reducers.

6.2.5 Dead legs in piping should be avoided. When a dead leg is unavoidable,it should be provided with drains.

6.2.6 Provisions should be made for the installation of a pressure gauge in thesuction piping between the strainer and the pump suction flange.



6.2.7 A pressure gauge should be installed in the pump discharge pipingbetween the check valve and block valve. Gauge isolation and bleedvalves should also be provided.

6.3 Permanent Inlet StrainersPermanent strainers should be provided according to PIP REIE686, Chapter 6 -Piping.

6.4 Temporary Inlet Strainers6.4.1 Temporary suction strainers should be provided for initial startup

according to PIP REIE686, Chapter 6 - Piping.

6.4.2 A means (typically a break-out spool) should be provided to remove thetemporary suction strainers.

6.4.3 A means of determining whether a strainer is plugged should beprovided. This is of particular importance on high-energy pumps.

6.5 Warm-up LinesPumps handling hot materials greater than 300°F (150°C) or handling high pourpoint materials should have warm-up lines in accordance with PIP REIE686,Chapter 6 - Piping.

6.6 Minimum Flow Bypass6.6.1 If the minimum continuous flow rate required by a pump cannot be

assured, a minimum flow bypass or instrumentation to alarm or shutdown the pump should be provided.

Comment: Sealless pumps require minimum flow protection at alltimes including at start-up and during upset conditions.

6.6.2 Unless otherwise specified, minimum flow bypass should be routed tothe suction vessel.

6.6.3 If the system provides adequate cooling for the recirculated fluid,consideration may be given to routing the minimum flow bypass to thepump suction line.

6.6.4 A bypass routed to a pump suction line should be connected at a pointthat is a minimum distance of 10 pipe diameters upstream of the pumpsuction flange.

Comment: Bypass control is often used on high specific speedpumps, such as axial flow pumps, because the powerrequirement decreases with increased flow.

6.6.5 Size of the suction vessel, thermodynamic properties of the pumpedfluid, and amount of fluid to be recirculated should be taken intoconsideration to determine whether a cooler is required in the bypassline.



6.7 Self-Priming Pumps6.7.1 Suction piping for self-priming pumps should be designed to minimize

friction loss and reduce the volume of air that must be evacuated in thesuction pipe.

6.7.2 Piping elbows and suction piping lengths should be minimized.

6.7.3 The suction pipe size should be the same size as the pump suctionnozzle.

6.7.4 During the priming cycle, air is evacuated from the suction line at a verylow pressure at the pump discharge. If the application requires adischarge piping system that incorporates a check valve to preventbackflow or to stop water hammer, an air bleed line or vent should beinstalled between the discharge flange and the check valve to ensure thatthe pump will prime. The air bleed line should not be installed below theliquid level or should not contain any liquid traps to impede airflow fromthe pump. An air release valve may be installed to allow the air to escapeand seal once the pump is primed.

6.8 Pumps Operating in Parallel6.8.1 The pressures on the suction and discharge sides of each pump in

parallel should be essentially equal.

6.8.2 If two or more pumps are fed from one common suction intake ordischarge into a common header, suction and discharge manifold pipingshould be symmetric.

6.8.3 Pumps operated in parallel should have block valves to allow individualpumps to be taken out of service.

6.8.4 Each pump operated in parallel should have a check valve installed inthe discharge line to prevent backflow under operating conditions.



Appendix – Typical Piping Arrangements – Figures

Documents

Guidelines for Piping Arrangements for Centrifugal Pumps