Non Slam Shut valves

[Rauri]

Hi All,

I have been asked to review a system in which a large pump has been added (>600l/s) as the existing 5No pumps are not operational. This is only a temporary measure.

The operational teams were having issues with what they thought was water hammer, and so, they also added a non-slam valve on the new pump discharge. They also opened the existing gate valves on the 5 pumps - as they were advised the recoil check valves would provide some benefit to the system.

While I would advise for the non slam check valve to be added anyway on the new pump discharge due to the length and volume of the main, I am confused as to why opening the gate valves on the existing, non operational pumps would have any benefit to the system. In my mind, for the recoil valves to work, the pumps would trip and then the column of water would hit the NRV before recoiling the other way creating a vacuum - and potentially lifting the recoil check valves as some kind of air relief. I highly doubt this is the case and they are not providing any benefit at all.

Could anyone provide some insight? I have attached a rough PID sketch.

Thanks

 

[mk3223]

Agreed that there is no sense to open the gate valve at the No.5 pump dicharge since it won‘t be run at all.
New check valve at the temporary pump discharge is needed for protecting it from the poterntial water hammer damage.
The other thought: is there an issue or concern of the confirugation of the pumps discharge piping as needed to open the gate valve of the 5th pump?

 

[Rauri]

Thanks!

I don't believe there was any other issue with the discharge configuration of the new pumps. The team thought opening the gate valves of the existing would bring the benefit of the recoil valves on the existing configuration... but don't' see how it has anything to do with it - as you would need flow through the existing pumps for the recoil valves to act as 'non-slam' valves.