Vacuum regulator question

[mingmongmang]

Hi

I'm tasked with building a fairly large (48x31x70") vacuum chamber and I'm not sure how to regulate the pressure. I've seen vac regulators that mount inline between the pump and chamber but I'd prefer a regulator that I can mount through the chamber wall, letting air in to maintain the vacuum level.

My reasoning is that I could use a much smaller bore (cheaper?) regulator than if I put it inline with the pump. The pump I'm using will be taken from an existing chamber of about half the volume and it uses 1-1/4 ID hose and I don't want to restrict flow and increase evacuation time.

If I do use a regulator that lets air flow in through the chamber wall, how do I calculate how large a bore I need, or can anyone give me a rough idea from experience? I expect to operate the chamber in the range of -5 to -15 psig.

Or.. If I should go with a 1-1/4" inline regulator, could someone recommend a good source or model?

Thanks,
Jon.

 

[Compositepro]

I've used Fisher regulators that have worked with great precision and can be set-up to work either way that you describe. I'd post a link but It seems fisher has been bought by Emerson and I can't find the valve I'm looking for. (How do these companies stay in business?).

If you are operating at very low pressure then it often often works best to bleed a little air into your system to regulate vacuum. This way you have a large and unrestricted line from chamber to the pump.

If you operate at high pressure (low vacuum), then regulate the line from chamber to pump,to avoid high flow rates and wasted pump power. There are other considerations like how clean is the flow from the chamber and the type of pump you use.

 

[moltenmetal]

compositepro gives excellent advice. Do NOT attempt to throttle a vacuum using an in-line regulator! Instead, use a controlled leak to regulate pressure. Where you allow that leakage to be introduced, and what you leak into the process (i.e. atmospheric air or a purified, dry gas) depends on your process needs.

If the "vacuum" your'e talking about is only a little below atmospheric pressure, then it makes sense to throttle the non-trivial mass of material you're actually pumping to take some load off the pump.