2 replies to this topic

[Technocrat]

Dear All,

This is a general question on centrifugal pumps:
Why NRV is located before the discharge valve and not after the discharge valve? What will be the consequences if done so?

Regards.

P.S.: Dear Administrator, can you please delete one of these posts? I have duplicated it my mistake. --DONE.

[Art Montemayor]

By “discharge valve” I believe you mean to state “discharge block valve”. Am I correct? The Non-Return Valve (NRV) is a Check Valve and I want to make sure just which “valve” we are talking about.

I also interpret that you want to know why a check valve is located Upstream of a discharge block valve. Am I also correct here? If so, then the reason is very simple: it is because this allows positive shut off of the discharge block valve and the ability to inspect or do maintenance on the check valve (with the pump shut down, of course).

Some people prefer to install the check valve DOWNSTREAM of the discharge block valve – and I have never quite figured out why. The consequence of doing it this way is that you can’t gain access to the check valve’s internal seat and mechanism. I always install the check valve upsteam of the discharge block valve. I do this because the check valve sees more cyclic operation and requires more maintenance that a block valve that only operates to shut down the pump and to start up the pump – which is little or next to nothing as service needs.

[Technocrat]

Dear Art,

Thank you very much for the reply. I always appreciate replies from you and read them thoroughly. I was thinking that it was a process reason to install the check valve upstream of the discharge block valve.

Thanks and Regards.