Pump Suction Straight Length Requirement

banu....

There is some difference in opinion on this matter, it is always best to get the manufacturer's requirements for the specific pump.

Generally speaking, for centrifugal pumps it is best to:

- Ensure that the suction piping diameter is one size larger than the suction nozzle

- Ensure that the fluid velocity is ~ 3-5 ft/sec

- A straight length of 3-5 of the LARGER SUCTION PIPE DIAMETERS (not the suction nozzle diameters) is desired

- Consult the Pump Handbook ( you already have a stolen copy) for more details

This is a piping layout guideline only....not good in all circumstances.

Your detailed evaluation and calculation of NPSH, of course, will govern the sucess of the installation.

You have done an NPSH evaluation...correct ?

Well why not ?

The reducer is preferred to be assembled directly into the suction flange to minimize any friction loss in suction line.

Very Important Note. The reducer at pump suction line must be eccentric type, and you have to verify its position, as TF (top flat) or BF (bottom flat)?

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on the suction side of a pump(in general) if you make your return manifold larger than the supply, and use the first in last out design, it will tend to balance the system

"use the first in last out design"

What do you mean by this, please explain.

sorry, first in , last out , is only used in solar collectors, and heating manifolds, where you have a closed loop system, and circulators ( not pumps) are used. I rate Mjcronin 's reply, as very good.

Dear all

when we have to place a minimum 5D spool piece then can we place reducer at the suction nozzle??

Not only can you, it is recommended by most pump manufacturers because it increases the size immediately allowing for less pressure drop, allows air movement (no pockets), and most important helps keeps pump from vortexing. The 5d is from the face of the suction to the beginning of the 90 degree ell. This dim. allows for ecc. red. inline. Short answer YES.