Overpressure protection for valves

[morojlu]

Dear all,

I want to buy a gate valve with high rating (1500LB) and our client has bben commented us taht this valve should have following condition:

1- Overpressure protection
2- Equalizing valve
3- parallel disk

I know Items 2 nad 3, but I didn't get item no.1, should the gate valve have some additional accessory?

Thanks,

mehdi

 

[davefitz]

I am not sure what he implies, but it can be one of 2 things:

a) gate valves may need to have a bonnet relief- a small bypass in the bonnet or above the gate to prevent accumulated water from expanding and overpressuring the bonnet when it heats up

b) the piping system it is connected to is required to have a positive means of preventing overpressure- safety valves sized for the max inlet casualty flow

 

[Scotsinst]

They may mean a parallel slide gate valve and require overpressure protection for the trapped media between the discs (thermal relief).

 

[waross]

It may be a pressure relief for water hammer, even though water hammer may not be an issue. (someone copied an old specification).
respectfully

 

[cliff6361]

Dave Fitz got it right. With high pressure and temperature valves a method should be used that will prevent the gate valve bonnent area from be overpressurized from fluid being trapped in the neck and thremal increase that can cause fluid expansion. This can lead to a very danerious condition. What could happen? The gate or wedge can be locked in the closed position preventing the valve from being opened to worst case the pressure can rise above the allowable deign limit for the material until a failure of the shell occurs. There are many ways of providing the protection - from the very simple to very complex. Keep in mind the more complex the more chances of it not working are.

 

[Ashereng]

mehdi

I think I am going with Scotsinst, the parallel slide gate (or slab gate)- it has sort of a "parallel disk" thingy happening.

Have you asked your client to clarify? That would have been my first step.



"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?