5 replies to this topic

[Beergson]

Hi all
I work based at UOP Process Basis Design Package.

I wonder why UOP set up for pump suction pipelines (to gate valve before the strainer) design pressure (material class) the same as for discharge pipelines?
Do you have any ideas?

[gvdlans]

Hi all
I work based at UOP Process Basis Design Package.

I wonder why UOP set up for pump suction pipelines (to gate valve before the strainer) design pressure (material class) the same as for discharge pipelines?
Do you have any ideas?

Please provide a sketch with a typical hook-up. Then we know what we are talking about...

[shan]

Hi all
I work based at UOP Process Basis Design Package.

I wonder why UOP set up for pump suction pipelines (to gate valve before the strainer) design pressure (material class) the same as for discharge pipelines?
Do you have any ideas?

Because it is parallel n+1 pump arrangement, the standby pump suction line may be pressurelized by the operating pump discharge.

[fallah]

Hi all
I work based at UOP Process Basis Design Package.

I wonder why UOP set up for pump suction pipelines (to gate valve before the strainer) design pressure (material class) the same as for discharge pipelines?
Do you have any ideas?

It isn't a strange situation at all.

Potential of surge occuring in discharge line of a pump may lead to suction line subjected to surge pressure and therefore would be designated with design pressure same as that of discharge line.

[Sridhar P]

Dear fallan and Shan,

Can we generalise that for all pumps working on standy by arrangment, suction line design pressure, from sution isolation valve, to be same as the discharge pressure whether positive displacement pumps or centrifugal pumps.

Hope NRV provided on discharge line will not gurantee no dischare leakage to suction side.

[djack77494]

Sridhar,
You are right to say that a NRV (check valve) will not ensure that reverse flow will not occur. So given the situation with multiple parallel pumps, one or more being employed as spares, there is the possibility that a spare pump will have a closed suction valve and an open (or leaky) discharge valve. In that situation, the discharge pressure of the operating pumps is fully realized back through the spare pump(s) as far upstream as the (closed) suction valve. Totally sensible.