Gate Valve - reverse acting, why?

[Actionman123]

If I have understood this correctly, in reverse acting gate valves, you pull the plug up to close the valve. Gate down = open valve.

What are the benefits of such a design?

In what kind of aplications is this valve used?

 

[dbaird]

Maybe it means air-to-open rather then air-to-close? This would be fail safe in some instances when and if you loose signal and/or air supply and it presnts a hazard if valve remains open.

David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.

 

[Joesteam]

Something does not sound right here. Reverse acting usually refers to actuation and not valve design. The design you suppose would have the valve stem in the main flow area when the valve would be open, and this would not be practical.

 

[Actionman123]

re dbaird;

No, this has nothing to do with fail safe action.
The valve is fail safe close.

re Joesteam;

The design in question here will not result in the valve stem in the main flow area. This is a slab gate. It's a plate with a hole in it. When the gate is down, the hole matches the flowpath. When the gate is up, the plate is blocking the flowpath.

My question is: Can anybody point out an aplication were this will be of any benefit?

 

[Sircrashalot]

I would think that in a situation of a dirty service this would be good as the pocket below the gate would be 'full' of the gate in the open and flowing condition. Because of this, the pocket would not be subject to filling up with debris that could cause the valve from fully closing.

Andy

 

[GrimesFrank]

Actionman,
As indicated by Joe the valve is to be coupled with a reverse action actuator.

The air to open aspect raises your stem providing flow. With an air loss (w/ spring return) it will cause a positive mechanical closure.

Frank "Grimey" Grimes

Rule 25. of Swanson's "Unwritten Rules of Management"

Have fun at what you do. It will reflect in your work. No one likes a grump except another grump.

 

[dcasto]

A Reverse Slab Gate valve is manufactured by WKM. The gate goes down to open a hole in the gate that allows fluid to flow. The theroy (or design) is if the stem and packing section is damaged in a fire accident, the gate will slam upwards and seal the line. WKM SAF tT SEAL or POER Seal

 

[jdraf]

This type of gate valve design is common for fuel safety shutoff in industrial burner applications (boilers, furnaces, flares, etc). If the seats are constructed of the proper materials, they can be rated to Class VI seat leakage.

The most common valve I'm aware of in this design configuration is MAXON.

http://www.maxoncorp.com.

 

[pipehead]

In pipelines, this valve is piggable. Some of the regular gate valves had guide ears on the bottom of the valve which would hang up a pig. Foster Valve is good too.

 

[JLSeagull]

OS&Y

 

[BRIS]

I am probably digressing: the slab plate valve described by Actionman123 is also termed a ring follower in the hydro power business and used in high velocity penstocks where we need a smooth flow path to avoid cavitation.