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Bleed Hole in Valve
- shrivallabha
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14 years 5 months ago - 14 years 5 months ago #7670 by shrivallabha
Bleed Hole in Valve was created by shrivallabha
In what case does a valve need to have bleed hole? What is the purpose?
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- Jop
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14 years 5 months ago - 14 years 5 months ago #5394 by Jop
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Replied by Jop on topic Re: Bleed Hole in Valve
This is often with the "Quarter Turn" family of valves such as Plug Valves and Ball Valves.
The "Bleed" (or Vent) hole is drilled through the upstream side of the plug or ball.
The reason for this is as follows:
Some commodities have a very high expansion rate when subjected to heat. This expansion creates excessively high pressure in the valve that could cause the valve to fail if the trapped liquid (in the cavity) were not able to vent.
Some Gate valves can also trap fluids in the top works, but are not normally specified for the high expansion commodities.
Globe valves, Butterfly valves and Check valves do not "Trap" fluids, so there is no problem.
The "Bleed" (or Vent) hole is drilled through the upstream side of the plug or ball.
The reason for this is as follows:
Some commodities have a very high expansion rate when subjected to heat. This expansion creates excessively high pressure in the valve that could cause the valve to fail if the trapped liquid (in the cavity) were not able to vent.
Some Gate valves can also trap fluids in the top works, but are not normally specified for the high expansion commodities.
Globe valves, Butterfly valves and Check valves do not "Trap" fluids, so there is no problem.
Do it once and Do it Right
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- 11echo
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14 years 5 months ago - 14 years 5 months ago #5428 by 11echo
Replied by 11echo on topic Re: Bleed Hole in Valve
I've seen a different application of "bleed holes" on check valves. Theoretically on a liquid commodity a "slug" could be trapped between a block valve and a check, when the block valve is closed. A 1/4" dia. "bleed hole" is drilled in the flapper on swing checks so if there is any thermo-expansion the pressure won't over stress the valve. Personally I've always questioned if the seat on the flapper would seal well enough to cause the problem!?? ...But on paper it sounds right.
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- sarandayal
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14 years 3 months ago - 14 years 3 months ago #5552 by sarandayal
Replied by sarandayal on topic Re: Bleed Hole in Valve
The floating seats provides a double block & bleed function when a drain plug & bleed valves is mounted on the body. The cavity can be relives through vent or drain connection. The independents upstream and downstream sealing ensures tight shutoff at the body cavity in the fully open or closed position. This features protests against fluid contamination and detects seat leakage from seats without dismantling the valve from pipeline.
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