POsition Seated Vs Torque seated Valve 2

[anandg84]

Folks,
What is the difference between position seated and torque seated valve?
When this terminology is been used. And which all valve will come under this category ?

Thnks

 

[zdas04]

Historically all valves were torque seated. Gate valves and globe valves get "shut tighter" when you tighten the handwheel further since the stem tries to drive them further onto the seat. Butterfly valves are the only torque-seated 1/4 turn valves that I can think of--adding torque drives the flapper further onto the seat, a missing stop can allow them to go past the seat and open again, but that is rare.

In the 1970's quarter turn valves became widely available. The first of these position seated valves was the plug valve followed by the now-ubiquitous ball valve. Full shut occurs when the seat completely blocks the flow path and going further would open the flow path on the other side.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[LittleInch]

That's a good reply.

Basically any valve which need torque to activate the seal is torque limited to apply the right pressure on the seals, and position is where position seals the valves.

Torque valves include wedge gate, split gate, expanding plug, globe and needle valves

Position valves are ball, normal plug, slab gate, piston type choke valves amongst others

Occasionally torque type valves will get clogged or jammed before full closure, but the torque limiter on the actuator cuts out and it is not always easy to see or indicate that the valve is not completly closed whereas position valves are usually easier to identify when they have not been fully closed and limit switches not made.

However that's pretty rare so in essence there's no real difference between the two to use as comparison.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[anandg84]

Thanks for the replying.

 

[Luxeal]

The orbit is a good exemple of a torque seated ball valve.




Luxeal

 

[LittleInch]

Basically a ball valve version of an expanding plug, but again the key issue is that force is used to create the seal instead of position.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way