Should I drill out my vacuum valve?

The valve might not work properly.

Maybe, it depends on the size of the chamber, and the pump you are using. If the pump or the chamber is small, then you may not find any change.

If that is the most significant restriction in the system, yes.

A better bet would be to simply eliminate the valve altogether, you really don't need it. Simply connect your pump to the vacuum chamber with the largest, shortest practical piece of tubing or hose.

Jim

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"jim rozen" wrote: (clip) A better bet would be to simply eliminate the valve altogether, (clip) ^^^^^^^^^^^^^^^^ That would also tell you whether the valve is a significant reason for the slowness in pumping down. It could be that the pump capacity is low compared to the volume you are pumping, or the other restrictions are also working against you.

In general, the more 'stuff' in a vacuum system like that, the lower the pumping speed. Most valves, even when wide open, restrict the flow somewhat.

Elbows or angled fittings, sections of tubing or hose, likewise.

The ideal situation is the chamber, stuck right on the inlet of the pump.

Jim

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No, the ideal situation would be where the chamber is the vacuum pump's piston(/vane/whatever they use). Go from zero to working volume in a single stroke... no troublesome valves! :) Hard to work with zero starting volume though...

Tim

-- "I have misplaced my pants." - Homer Simpson | Electronics,

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This is how they make liquid hydrogen bubble chambers. The cylinder itself is the chamber, and a piston is pulled down to make the liquid hydrogen inside the cylinder become supercritical, so that any particles that pass through leave tracks. The initial volume is not zero though.

Jim

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Jim,(and all others) thanks for the response. So if I have the hose connected to the chamber with no valve and with a full vaccuum inside, I would reduce the vacuum by loosening the tube?

Steve

At the pressure you'r likley talking about for degassing, where the mean free path is >>> the size of fittings, doesn't it more or less work as at atmospheric pressures?

I thought elbows were only to be strongly avoided once the gas pressure got very low, or when the flow approached supersonic.

If I have the hose connected to the chamber with no valve and with a full vaccuum inside, I would reduce the vacuum inside by loosening the tube? Thanks Steve

You could put a vent valve into the system if you wanted. That would give you a more controlled vent up. If you vent de-gas chambers too rapidly, you can upset the container of material inside, with predictable, messy, results.

I would imagine something like a short section of copper pipe, with a small 1/4 inch needle valve on the side. That could be put inline with the pumping line.

Jim

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I high vacuum system big valves are essential, often as big a 12 inches or more. For the initial pump down the vacuum piping is much smaller. A very small valve could be a problem.

Scp

Vacuum degassing is not high vacuum.