Q: Pressue in dead cavity?

[scartail]

Hey all... I have a simple question, I think.

I have a small dead cavity that is only 0.030" wide by 1.5" diameter. The only leak path would be under bolts/washers (this bolts (3x) are small 1/4" dia or less). How much pressure should I expect in that cavity, if the head of the bolt area is at 2000 psi? I surveyed my colleagues and get a mix response (almost a 50/50 split). Some say little pressurization, others say full 2000 psi. My thinking is that the bolt/washer interface provides some resistance/sealing (though a bad seal).

What do you think?

Thanks in advance.

s.

 

[1503-44]

Can't see what you are talking about.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[TugboatEng]

Assume interfaces are going to leak. What damage can result?

When I put pneumatic controls in a sealed electrical enclosure I drill holes in the enclosure. What happens when your seal fails?


How tight is your cavity relative to the leakage through the bolt?

 

[LittleInch]

Sketch needed to make sure but a bolt washer combination is not designed to be gas tight.

So if there is 2000psi gas pressure outside the bolt then your v small void will become 2000 in most cases.

The odd one or two might seal, but the vast majority don't.

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

 

[1503-44]

Like a Flange w/o a gasket? That's a good one.
Gas molecules are smaller than unsealed interfacial gaps.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[scartail]

Thanks for the input. Sorry, the fluid is LNG.

 

[geesaman.d]

If there's an instantaneous pressure change, that gap will take a bit longer to pressurize. But it will.

 

[LittleInch]

You have 2000 psi of LNG?? Really??

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

 

[1503-44]

Possibly CNG

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[cvg]

the interface provides some resistance/sealing (though a bad seal).

if you have a bad seal than it is connected and eventually will become fully pressurized. doesnt matter how much resistance it has to flow.

I'm just surprised that half your colleagues got it wrong...

 

[Snickster]

I still don't have any idea what the OP was talking about.

 

[IRstuff]

The odds of creating a hermetic seal by accident is almost nil. Even when one tries to create hermetic seal, but has no experience in doing so, the odds for success are low.

On one program, we thought we might have created a hermetic seal and became worried about overpressure; when the unit was actually built and pressurized, it lost pressure in seconds.

Even when a system is correctly designed for a vacuum seal, it takes a lot of vigilance and maintenance to keep the seal from leaking.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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