centrifugal pump piping design layout

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LLaayyoouutt aarrrraannggeemmeenntt ffoorr CCeennttrriiffuuggaall PPuummpp PPiippiinngg

11.. GGEENNEERRAALL

The design of a piping system can have an important effect on the successful operation

of a cceennttrriiffuuggaall ppuummpp. Such items as pump design, suction piping design, suction and

discharge pipe size and pipe supports must all be carefully considered. A typical

horizontal cceennttrriiffuuggaall ppuummpp installation is illustrated in FFiigg..CCPPPP11,, CCPPPP22,, CCPPPP33.

Selection of the discharge pipe size is primarily a matter of economics. The cost of

various pipe sizes must be compared to the pump size and power cost required to

overcome the resulting friction head.

11..11 The suction piping size and design is far more important. Many cceennttrriiffuuggaall ppuummpp

troubles are caused by poor suction conditions.

11..22 The suction pipe should never be smaller than the suction nozzle of the pump and

in most cases it should be at least one size larger. Suction pipes should be as short and

as straight as possible.

Suction pipe velocities should be in the 1.0 – 1.5 metre per second range, unless

suction conditions are unusually good. Higher velocities will increase the friction loss

and can result in trouble some air and vapour separation. This is further complicated

when elbows or tees are located adjacent to the pump suction nozzle. In that case

uneven flow patterns or vapour separation keeps the liquid from evenly filling the

impeller. This upsets hydraulic balance leading to noise, vibration, possible

cavitation and excessive shaft deflection. Cavitation, erosion damage, shaft breakage or

permature bearing failure etc. may result.

11..33 On pump installations involving suction lift, air pockets in the suction line can be a

source of trouble. The suction pipe should be exactly horizontal or with a uniform slope

upward from the sump to the pump as illustrated in Fig.CPP7. There should be no high

spots where air can collect and cause the pump to lose its prime. Eccentric rather than

concentric reducers with flat side top should always be used.

11..44 If an elbow is required at the suction of a double suction pump, it should be in a

vertical position if at all possible. Where it is necessary for some reason to use a

horizontal elbow, it should be a long radius elbow and there should be a minimum of

five diameters of straight pipe between elbow and the pump suction as illustrated in

Fig.CPP9.

22.. LLOOCCAATTIIOONN

22..11 Common location of pumps in chemical and petrochemical plant is under the

piperack at grade.

Pumps are to be placed close to and below the vessels from which they take their

suction in order to have net-positive suction head (NPSH) required by the pump.

22..22 Any reduction in suction line size required at pumps should be made with eccentric

reducers, with flat side up to avoid accumulation of vapour pocket. Changes in

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Centrifugal Pump Piping Design Layout http://www.piping-engineering.com/layout-arrangement-for-centri...

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direction of suction lines should be at least 600mm away from the pump suction.

22..33 Pumps should be arranged in line with drivers facing the access gangway.

Clearances and piping should provide free access to one side of the driver and pump.

There must be good access to gland / seal and coupling where most of the

maintenance and adjustments are done.

22..44 With normal piperack column spacing of 6m, it is generally found that only two

pumps of average size can be arranged between the columns, with a preferred

clearance of 1m between the pumps.

The clearance between any structure / steel work and the pump discharge line shall be

0.75m minimum. For small pumps upto 18 KW, clearance between pumps should be

0.9m minimum. A space of 2 – 2.5 m should be provided for working aisle.

A typical arrangement of pumps is illustrated in Fig.CPP4, CPP5, CPP6.

22..55 Means of lifting should be provided for pumps or motor weighing more than 25Kg.

33.. SStteeppss ttoo ddoo PPuummpp PPiippiinngg

Step 1 : Collect the P&ID and the pump data sheet.

Step 2 : Study the pump data sheet and collect the similar (capacity / head) pump

dimensions / nozzle position.

Step 3 : Analyse the location and the space provided in the unit plot plan w.r.t. suction

and discharge line routing.

Step 4 : Review the maintenance / operation space around and lifting facility.

Step 5 : Locate the control station, Electrical push button station, Electrical-trench,

process fluid drain, flushing / cooling connection as required for the pump model.

Step 6 : Check elevations of all valve handwheels on suction as well as discharge line

and provide common platform for valve operation, if required.

Step 7 : Make Iso sketch for suction and discharge line with all the items as per P&ID

and discuss with process engineer for any change.

Step 8 : Finalise supports of the line and issue for stress analysis, if required.

Step 9 : Get the stress analysis report for Nozzle loads. Compare the allowable loads

with the actual load for any change & finalisation.

Step 10 : Finalise location of pump / drain or trench / Electrical cable route and issue

civil information to civil for foundation design.

Step 11 : Keep necessary insert plate on the foundation block for support of push

button switch, small lines for flushing / cooling manifold.

44.. PPUUMMPP PPIIPPIINNGG ::

44..11 HORIZONTAL CENTRIFUGAL PUMP :

A typical horizontal cceennttrriiffuuggaall ppuummpp suction and discharge piping arrangements is

illustrated in Fig.CPP7.

44..22 Pump suction piping shall be as short as possible and shall be arranged so that

vapour pockets are avoided.

44..33 Reducers immediately connected to the pump suction shall be eccentric type flat

side up to avoid accumulation of gas pocket.

44..44 For end suction pumps, elbows shall not be directly connected to the suction

flange. A straight piece 3 times the line size shall have to be provided at the suction

nozzle. This is illustrated in Fig.CPP8.

The effect of elbow directly on suction is illustrated in Fig.CPP9.

44..55 For top suction, pump elbow shall not be directly connected to suction flange. A

straight piece of minimum 5 times the nozzle size shall have to be provided at the

suction nozzle.

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44..66 T-type strainers are to be used for permanent as well as temporary to avoid

disassembly of suction piping for strainer cleaning.

44..77 Piping shall be so arranged that forces and moments imposed on the pump

nozzles do not exceed the allowable values specified by the vendor.

44..88 When a suction vessel operates under vacuum the vent connection of the pump

has to be permanently connected to vapour space of the suction vessel to allow

possible filling of the pump with liquid before it is started.

44..99 For pumps handling hot fluid, the first factor concerns the support of pump piping

which often includes large expansion loops for flexibility. When the pumps are located

below the piperack (to reduce possibility of hydrogen leakage over motor), support

becomes easy otherwise the designer should consult stress engineer for best location

of stops and hanger. With the optimum layout and support, it is to be ensured that the

loadings on the pump nozzles are not exceeded beyond the allowable limits.

44..1100 Piping configuration for a group of pumps of similar size shall follow identical

pattern and the stress analysis of one pump piping should be applicable to the other

pumps.

44..1111 Auxiliary Pump Piping Arrangements:

The Auxiliary piping are usually cooling water to mechanical seals, bearings, stuffing

boxes, gland quench and lantern ring flush.

When pump fluid is used, a line is attached to the vent connection on the pump case.

The circulated seal fluid has to be sent back to pump stream or referred through the

seal to pump internal clearances.

In viscous or high temperature hydrocarbon liquids, the seal fluid medium circulates

from external source through connections on the pump seal.

Various Auxiliary piping plan is recommended in API 610 for proper selection according

to design requirements.

44..1122 Pump vendors usually supply the Auxiliary piping and the neat

arrangements of these piping and its support are to be ensured by the designer while

reviewing the vendor document. Fig.CPP10 illustrates one typical Auxiliary piping

arrangement on the pump base plate.

44..1133 A typical arrangement for piping and valves operation is illustrated in

Fig.CPP11 with maintenance and operation access.

44..1144 A typical suction and discharge piping arrangement with common platform

for operation of valves connected to two adjacent pumps is illustrated in Fig.CPP12 and

CPP13.

55.. SSUUCCTTIIOONN BBAASSIINN OOFF PPUUMMPP

55..11 The basin for the intake of centrifugal pump shall be designed and sized properly

for smooth function of the pump. The recommendations of hydraulic institute are

illustrated in Fig.CPP14.

55..22 The flow of fluid to the suction bell should be even, smooth and stream lined

without any vortices.

55..33 A typical sump with the components and relative dimensions of clearance and

submergence is illustrated in Fig.CPP15.

55..44 For multiple pump installations with high capacity pumps, the analysis of a

proposed intake design are often made by use of a scale model of the intake basin with

all parts such as baffles, screens, gates, separating walls etc.

The large basin is required to ensure low inlet velocity (approx. 2 ft. per sec.) and to

eliminate vortexing at the bell mouth.

55..55 A typical sump pit with pump is illustrated in Fig CPP16. This sump is the collection

pit of waste material coming through a pipeline. A screen at the mouth of the pump

avoids choking / fouling of the pump during operation. The discharge of the pump may


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go to a slope tank / pond / waste-removal tanker.

Fig CPP1: Centirfugal pump drawing (Type-1)


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Fig CPP2: Centirfugal pump drawing (Type-2)

Fig CPP3: Centirfugal pump drawing (Impeller)


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Fig CPP4: Typical pump location plan


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Fig CPP5: Typical access for Maintenance

Fig CPP6: Typical pump locations-Elevation


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Fig CPP7: Air pockets in suction piping


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Fig CPP8: Typical pump suction & discharge piping


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Fig CPP9: Elbow at pump suction

Fig CPP10: Typical auxiliary pump piping


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Fig CPP11: Maintenance & operation access requirements


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Fig CPP12: Typical suction/discharge piping, plan & elevation


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Fig CPP13: Typical suction/discharge piping, front view

Fig CPP14: Multiple pump installation (Vertical pumps)


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Fig CPP15: Sump dimensions, plan view, wet pit type pumps

Fig CPP16: Typical sump with pump

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3 COMMENTS

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July 17, 2015 at 8:52 pm

Marty Metz

Very HelpfulThank you

Reply

October 28, 2015 at 2:31 am

N. senthil kumaran

Useful technical details.Thank you very much

Reply

January 25, 2016 at 7:47 am

Salman Malik

Quite Helpful.Thanks

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centrifugal pump piping design layout

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