Pump Back Pressure

[Charlesan]

Our customer has three pumps supplying an 8" Main Header, one pump is on standby, one pump has been serviced and is delivering 300psig into the 8" header,the other working pump is only generating say 260 psig into the overhead header,consquently the 300psig from the first pump is putting a back presure on the other pump and is stopping the check valve from opening and delivering its flow in the main 8" header, the supply lines into the header from the pumps are 6" with a vertical check valve above the pump followed by an isolation valve

Can anyone advise how the pressure can be equalised in the most efficent manner

Thanks

Charlsan

 

[Artisi]

The rough way to do it is throttle the discharge valve on the 300psi to a point where the other pump can open its NRV.

Or overhaul the other pumps so they all produce the same pressure.

 

[JJPellin]

Assuming that the pumps are identical and are designed to run in parallel, then I would tend toward the second suggestion from Artisi. The weak pump must be severely deficient if it can't produce as much pressure at dead-head as the other pump produces at normal flow. However, before overhauling that pump, I would verify that it has adequate suction pressure. Specifically, I would look for restricted suction strainers, gate valves with dropped gates or incorrect valve line-up. If the weak pump has proper suction conditions and it is running at full speed, then the pump may have internal wear or damage. If you give more details about the configuration of the pumps and the arrangement of the process, we could be more helpful.

Johnny Pellin