Gate Valve without bottom cavity

[gaoms84]

What is the use of bottom cavity in gate valve?
In my feed document of my ongoing project, underground burried Gate valve(as per AWWA 515) is without bottom cavity. What could be the reason behind this?

What if the same valve is used for above ground? Do we still need to provide without bottom cavity ?


Thanks

 

[pennpiper]

Gaoms84,
It is possible you have the wrong impression of the design of the typical Gate Valve.
What you are calling a "cavity" at the bottom of the Gate Valve body is part of the Guide and the sealing of the wedge(see the detail in these images:

https://www.google.com/search?q=Gat...2Hom6yAG94IHYCw&ved=0CCYQsAQ&biw=1024&bih=665

).

The vertical surfaces on each side of the body has cast in guides that hold the wedge in proper alignment as it travels up and down during the opening and closing operation. The bottom of the body is shaped the same as the guides on the sides and continues the guide down one side of the body around the bottom of the valve body and up the other side. There are surfaces (or seats) near the side rails and the bottom curve of the body that are machined along with the surface of the gate which provide the seal. The cavity (or space) at the bottom of the valve is there to allow the wedge to become alined with the seats and form the seal.



prognosis: Lead or Lag

 

[gerhardl]

You are not asking about a knife-gate valve? (In case the explanation will differ.)

 

[LittleInch]

gaoms84,

As you no doubt have found, there are many variations of "gate valve" and many suppliers, each with their own design.

A slab gate valve normally has a "cavity" so that the slab has somewhere to go, but many wedge gate valves don't.

A cavity can be bad news if you're transporting fluid with particles as they can fall in there and prevent correct operation of the valve. Thus in most designs, this is avoided, but if you have a particular issue, post a section of the valve(s) in question.

My motto: Learn something new every day

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