60 inch butterfly valve with a drain?

[Rakesh2560]

Greetings friends,

Needed a little help we have a 60 inch butterfly valve in a flare line which is passing it has got a small bore gate valve connected to it right opposite the drain we just wanted to know the purpose of the valve can any one tell me what's the purpose of small bore valve attachef to the butterly valve & is it safe If we inject sealant to it to stop passing the isolation is required in order to reverse spectacle blind downstream to isolate a drum

 

[JStephen]

http://www.tlv.com/global/TI/steam-theory/bypass-valves.html

On large municipal water valves, they frequently have a small bypass valve. I've understood in the past that the purpose of that valve was to let them relieve some of the pressure differential across the main valve to make the main valve easier to operate. That seems to be an application not considered in the link there.

 

[Gator]

Without a photo or sketch it's hard to guess.

 

[racookpe1978]

If we inject sealant to it to stop passing the isolation is required in order to reverse spectacle blind downstream to isolate a drum

This sounds VERY dangerous in a flare line 60 inch in diameter!

You have a bypass valve that is leaking (I think) around a flare line (safety release line right?) main valve, and you want to inject (an unknown) sealant into the bypass/vent valve inlet upstream of a spectacle flange, just so you can insert a blind flange in the spectacle flange location? Do you propose continuing to operate under this condition?

 

[chicopee]

A gas sampling line, perhaps?

 

[racookpe1978]

The entrapped gasses and fluids between the two seals of the double seal cutoff valve will expand as the temeprature changes: Creates a vacuum (that will pull out the gaskets, lockup the valve from moving easily) or expand create a pressure bubble between the two seals (similar results) -> both bad for the valve, bad for the operators.

Pressure gage point? Relief valve point? Test point for checking the seals periodically?
Sample point not likely: Why would you sample a non-flowing, trapped and isolated part of the product being produced. Vent point if on top. Drain if below.

 

[LittleInch]

Who said it was a double disc / double seal valve? All the Op has said it that it's a butterfly valve.

We have no type, no vender, no drawing, virtually nothing.

Sounds like someone put the spectacle blind the wring side of the isolation valve to me...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[racookpe1978]

True, true. The image above was added by a reader, not by the original poster.

 

[Rakesh2560]

Thank you guys for your feedback I still haven't figured out the purpose of 1 inch valve but p & I'd says it's a valve with a bleeder so may be used for draining

 

[Gator]

There was no mention of a bypass around the valve by the OP and to my knowledge (maybe that's not saying much), butterfly valves typically don't have connections (or bosses) for vent/drain piping. Unless it's a dual-disc which forms a cavity between the discs that can be vented/drained for whatever reason when the disc is closed. As LI confirms, without a photo/sketch/vendor drawing or valve model number it's difficult to say what is the purpose of the "small bore gate valve connected to it right opposite the drain". Why wouldn't the drain be on the up or downstream piping rather than on the valve itself?

Presumably there would be two vent/drain locations on the valve body, which location to be used would depend on which orientation the valve is installed. The valve would have to be installed with the stem horizontal if you wanted to drain flare line liquids from the cavity created by the double disc configuration (obviously).

But this is all speculation.

[Edited to clarify]

 

[georgeverghese]

Maybe talk to a hot tap specialist company to see if they can help you..