Believe it or not, the pump performance factor is outside the pump. The piping connected with a pump affects performance. If the piping is wrong, efficiency of the pump goes down and you pay for maintenance and energy for the pump's service life. Sump design, suction piping design, suction and discharge pipe sizes, pipe supports etc., decide how your pump will perform.

Crucial suction piping
The discharge piping size and layout are a matter of economics. For the discharge side, allow a least-cost pipe size and layout, considering friction loss and energy cost of pumping. Ensure that the pump will operate at duty point. The story of the suction piping is different. This piping is a crucial contributor to the performance of a pump.

NPSH & cavitation
Centrifugal pump troubles begin when you have poor suction conditions. The suction piping supplies liquid under a limited pressure. If the piping is poor, cavitation will occur. Cavitation means vaporization of liquid in suction area and inside the pump. Cavitation damages the pump impeller. All centrifugal pumps are liable to face cavitation and all applications must avoid it. Keeping the suction pressure high is the answer. That pressure on suction side is 'NPSH' (Net Positive Suction Head) Keep the system NPSH more than what the pump NPSH parameter is.
 

Good suction piping
The suction pipe should never be smaller than suction connection of the pump and, in most cases, should be at least one size larger. The suction pipe should be as short and as straight as possible, to make the flow smooth and to lower friction loss.

Keep the suction pipe velocity as recommended for the liquid and pipe material. Remember, higher velocity increases friction loss. That will reduce NPSH and air or vapor separation at suction may occur, a condition not acceptable.

Layout and fittings
The suction piping is further complicated when elbows or tees are located adjacent to the pump suction nozzle. This gives an uneven flow pattern. Try to make the suction piping straight and without a fitting before the pump. The right way to install an elbow is to put it in the vertical run. If vapor separation occurs, it will upset hydraulic balance. That will lead to vibration, cavitation and excessive shaft deflection. For high and very high suction energy pumps, shaft breakage or premature bearing failure may occur. Another layout requirement: When you have a pump adjacent to the supply tank and the suction pipe is horizontal, ensure that the minimum level in the tank is higher than the pump casing.

Lift pumps
If your installation has suction lift, air pockets in the suction piping can be a source of trouble. Make suction piping horizontal. If that is not feasible, give a uniform slope upwards from the sump to the pump. Ensure that you do not have air pockets. There should be no high spots where air can collect. If air accumulation happens, the pump will lose its prime. On horizontal installations, use an eccentric, rather than concentric, reducer always. Install it with the flat side on the top.

Suction pipe submergence
Often, while filling, the discharge of liquid is free above the surface of the supply tank. If such a flow is near the pump suction, the entrained air will enter the pump. Submerge the supply lines under the liquid surface. How much of the suction pipe should be submerged in the liquid is also an important parameter. Improper submergence can cause a vortex.

Conclusion
The pump is a dynamic machine and all dynamic machines are affected by outside conditions. The suction piping has to be right. Do that or pay.

Source- Project Vendor.
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