Gate valve stem in Horizontal position 2

[nasim123]

Dears
As per Saudi Aramco Standard SAES-J-600 States " When gate valves are used as block valves for Pressure safety valves,they shall be installed with the stem horizontal or sloping down away from the relief valve to keep the gate from falling off and blocking the flow.".

What is the logic behind the above statement. If the Block valve stem is in vertical position what will happened? Your advice please...

Thanks
Nasim

 

[don1980]

The reason is stated in the last phrase of the quoted text: "....to keep the gate from falling off and blocking the flow." This is referring to a potential mechanical failure of the connection between the gate and the valve stem.

This statement is copied from API 520 Pt2 (ref 8.3.2).

 

[georgeverghese]

It is also good practice to use full bore valves on the inlet and exit of the PSV.

 

[LittleInch]

There are the occasional gate valves which have a rising slab to open....

I suppose the potential is always there for a gate to fall off, but it is a pretty rare event.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[nasim123]

Thanks a lot for the reply