Discharge of Centrifugal Pump
Discharge of Centrifugal Pump
(OP)
I always install check valve at the discharge of pump. I understand that it is a general practice for pump installation.
However, someone said that check valve is not required in case of no chance of back flow to damage the pump. They did not tell me in detail about such cases. Please advise me about this matter.
However, someone said that check valve is not required in case of no chance of back flow to damage the pump. They did not tell me in detail about such cases. Please advise me about this matter.





RE: Discharge of Centrifugal Pump
I can't recall seeing a pump without a check valve on the discharge.
The biggest problem with check valves is that they are routinely oversized. People tend to size them off the pump discharge pipe diameter. They should be sized for the flow. An oversized check valve will flap like a flag in the wind, and wear out long before it should. (This is why swing checks wear at the point where the shaft goes through the flapper.) I've seen pumps with 4" discharge flanges that only required a 1-1/2" check valve.
RE: Discharge of Centrifugal Pump
RE: Discharge of Centrifugal Pump
The question of the need for a check valve is related to the number of pumps performing the same service (i.e. the installed spare situation). Most pump installations have two pumps (each at 100%) or three (or more) pumps each with a percentage of the duty.
When there are multiple pumps installed in parallel, there must be a check valve installed to prevent reverse flow to and protect the pump or pumps at rest.
If you have a single pump, only used occasionally without a path for reverse flow, then isolation valves upstream and downsteam of the pump will suffice.
I am aware that there is a lot of opinion in cyberspace about this subject, and some will not agree with me..... nonetheless the single-pump system can be operated adequately.
Any ideas from other people ????>>>>>>>>
MJC
RE: Discharge of Centrifugal Pump
1. A pump fitted with check valve can be left with both suction and discharge valves wide open. This allows the operator to just switch on and bring the pump on line within a short span of time.
2. If a standby pump is to be a autostart pump then check valve is a must.
3. Presence of discharge check valve with bypass line and valve allows the pump to kept hot.
Thanks
RE: Discharge of Centrifugal Pump
Check valves are necessary to prevent the backflow that would occur in most systems due to downstream pressure reversing the flow with a sudden loss of input pressure from the pump. Most systems do not suddenly depressurize, and would tend to backflow.
Leaving pump on check valves with discharge and suction open:
This is hazardous. Check valves are NOT positive seal valves and the pump can rotate backwards due to downstream pressure. Also, if a seal failed, the fluid (often hazardous) can leak out if the valves are left open.
RE: Discharge of Centrifugal Pump