About gate Double Block and Bleed Valve 1

[kirby110]

I have a problem and hope get a hand. The problem are as following:
"Gate Double Block and Bleed Valve to ensure proper sealing in each branch. The DB&B Valves are specialized sealing valve with spring loaded seals on both sides."

What's mean of Gate Double Block and Bleed Valve?


Thanks a lot

 

[davefitz]

Normally a double block and bleed means two stop valves in series , and also supplied with a small bleed line in between the 2 larger stop valves. The bleed line also has a stop valve , and the bleed stop valve discharges into a viewable drain pot. The reason is to enable a worker to positively prove to himself that no presurized process fluid can enter into the isolated system, so he can work on the equipment with confidence that he will not be hurt.

There are also some special stop valves with 2 seats which are claimed to serve the same function as a double block and bleed, but I know little about them.

 

[zdas04]

I haven't seen this particular valve, but I've never seen a gate valve that was advertised as bubble-tight in gas service.

I have seen big-inch gate valves with a split gate that was spring loaded. I can't recall ever seeing a body bleed between the gates though. It seems like having a significant pressure upstream of an evacuated body would require an impossbilty large spring (50 psid on a 16-inch gate would be 2,500 lbf trying to unseat the gate, I'd hate to try to pre-load that spring).

If you are unclear on what Double Block and Bleed is, there have been many interesting discussions of the concept in this forum. Most recently the thread on Trunnion Ball valves last week had some very good information in it.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[shoffman83]

Actually, this is also known as an expanding gate valve, and what it allows is yuou to exacuate (bleed) the valve between the two gates. WKM Pow-R-Seal is an example.

 

[askmeaboutvalves]

The Cooper Cameron General Twin Seal Valve will fill your request.They are the world's leading manufacturer of high-integrity, positive shutoff Double Block & Bleed valves. It has been around since 1941.
Bob Paul
paulrj@ccvalve.com

 

[ValveGod]

Hi - if you've been asked for a GATE DBB, then its an expanding-type of gate that you need to look at - similar in function to the Parallel Slide Valve, where effectively there are two seperate gates within the assembly.. Have a look at doing a search on Through-Conduit Gate Valves on google or a similar search engine and you'll find companies like BEL Valves, Brieda Energia,
Bonney-Forge Vitas, Ring-O Valve etc will be able to point you the right way.

Cheers VG