API 6D Gate Valve Selection - Slab vs Expanding
API 6D Gate Valve Selection - Slab vs Expanding
(OP)
In a situation where the valve size, class and trim are the same why would I choose an expanding over a slab. Not talking about metal seated. when would you use a 600# expanding gate over a 600# slab gate, let's say both were PEEK seated for high temp.
I have assumed the expanding gate's mechanical seal would be well suited for gas applications when there line pressure fluctuates. Is that right?
Any other info appreciated.
I have assumed the expanding gate's mechanical seal would be well suited for gas applications when there line pressure fluctuates. Is that right?
Any other info appreciated.





RE: API 6D Gate Valve Selection - Slab vs Expanding
Expanding gates will give you, at least are supposed to, 1. an upstream seal against line pressure, and 2. reduced operating torques at full pressure differential when opening.
Rick
RE: API 6D Gate Valve Selection - Slab vs Expanding
As the seating force is not affected by the fluid pressure then any application where line pressure is not high would be a good use.
Places where you have isolation for entry - things like pig traps - and you would like really good isolation over a long period of time / usage like station isolation valves are where you might go the extra mile in terms of cost and size to install an expanding gate.
As with DPE seated ball valves you need to allow for liquid expansion in the cavity if exposed to solar effect or other heat input for an expanding gate valve.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: API 6D Gate Valve Selection - Slab vs Expanding