leak rates for pinch-off tubes
leak rates for pinch-off tubes
(OP)
I'm looking for numbers on leak rates using pinch-off tubes.
Thanks,
Ben.
Thanks,
Ben.
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leak rates for pinch-off tubes
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RE: leak rates for pinch-off tubes
Pinch-off tubes can be vacuum tight for years for a small volume dewar such as those used in IR detectors. My guess is that the volume is around 30 cc, assuming 1 inch OD and 0.5 inch ID for cold finger and about 3 inch long.
TTFN
RE: leak rates for pinch-off tubes
The chamber is closed with a gate valve and a pinch-off tube.
I plan to pump it down, activate the getter, seal the gate valve, and then look for leaks using an RGA.
When satisfied, I'll close the pinch-off, and the whole assembly (which is now not monitorable) will have to live for a year or two before being launched into orbit.
At a later time, the gate valve will open.
I need to be certain that the getter does not saturate during the years of storage.
I don't have a way to monitor the pressure after I pinch-off, which is a big headache for me.
RE: leak rates for pinch-off tubes
RE: leak rates for pinch-off tubes
Given your description, a good pinch-off should certaintly be no worse than a gate valve.
TTFN
RE: leak rates for pinch-off tubes
With high volume applications, if there's a certain chance of the procedure not sealing, it translates directly into yield numbers.
For this design, if the procedure fails, the experiment won't work, so it becomes a mission assurance issue.
The only way I know of verifying the seal quality is from the inside, which means another feedthrough.
Anyone familiar with a way to verify the seal from the outside?
RE: leak rates for pinch-off tubes
TTFN
RE: leak rates for pinch-off tubes
A hot-cathode gauge can be added, though will probably break on launch. (but will work during storage)