Watermain Shutdown Analysis - Secondary Valving

[geosean]

Hello All,

I'm an EIT working on a watermain shutdown analysis for a client. The base analysis simply requires that I model a watermain shutdown between the existing isolation valves that I locate on their as-builts. This is a fairly typical assignment, with the exception of one line at the end of the request that has me a bit confused - "Please also let me know what the impact would be if we had to do secondary valving."

Could someone give me an idea of what is meant by secondary valving? No one in my office seems to have an idea.

Thank you!

Sean

 

[cvg]

well, I would have to assume that meant the existing valves are not able to fully shut down the line. Either they are broken or will not seal tight. Alternatives for secondary valving would be either

a) a secondary valve would have to be installed to fully isolate the system or

b) a second valve at another location would also need to be closed to isolate the system

both would have the impact of shutting down a larger section of the system

 

[geosean]

Great, thank you cvg - that makes perfect sense. Based on the assignment I'm leaning towards your option 'b'.

Cheers!

 

[bimr]

To add background to cvg's post, only the top utilities maintain these valves. Some of these utilities have a valve exercising program where the valves are periodically operated.

Sometimes when the operator tries to close a valve, the valve will not close and the operator has to move upstream to try to close the next valve.