I want to draw a modest vacuum on the nitrogen laser. We are doing OK with our reversed refrigeration compressors, but now would be a good time to consider moving to a better vacuum system. A two-stage, rotary vane, air conditioning vacuum pump with micron pressure gauges would be nice, if I could find some at a good price, along with tubing and couplings necessary to connect it to our system. I could go down to the pawn shop and buy a vacuum pump for $150, but I don’t know what makes one pump on the shelf better for our application than another pump on the shelf. The nitrogen laser project wouldn’t care either way, but maybe something in the future would.
Along with pump and connector expertise, we could use better techniques for finding leaks. Many of the same vacuum problems that apply to air conditioning systems also apply to our nitrogen laser.
In addition to the nitrogen laser, Science Committee apparently owns a large vacuum chamber. I’d like to hook it up and test it out, but I don’t know what couplings it needs. I’d also like to know why we have it and what it has been used for.
Let me email my brother-in-law who does HVAC for living. I gave him a vacuum pump in the past, I don’t believe he uses it, if so I’ll ask him for it. Let you know in a couple of days.
Yes! That will be quite helpful! It should be a fine roughing pump for our first stage of experiments.
Now, we need to figure out hoses, connectors and gauges. Our current equipment is crude, and can barely do what we need. It still leaves several inches of atmosphere when drawing a vacuum, and the vacuum gauges could not resolve the last inch, anyway.
The system your BiL is lending us could get us down well inside the last inch, and right to the edge of moderate vacuum. We could then hook up a high-vacuum pump, such as a diffusion or cryopump, to get us down to where we need to go for future projects.
I was referring to our current equipment, which struggles to reach 27 inches of vacuum. That’s right on the edge of what we need for the nitrogen laser.
50 microns is in the single digit Pascal range, which the chart shows as Medium Vacuum.
Not really. No mechanical pump can reach deep vacuum.
Nope if you look at the chart @Photomancer provided you will see that 50 microns is about 7 x 10^-3 kPa which solidly places it in the high vacuum range.
I will also add that most rotary vane pumps will only reach their rated performance with new oils and seals. Otherwise they are usually about twice the residual pressure they are rated for. (or worse) but that still sounds like a considerable upgrade.
Separately, the vacuum pump for the vacuum former is a much better pump than anyone gives it credit for. If it gets released from the vacuum former, I would suggest taking it off the huge accumulator, building a filter to catch the oil mist they make, and determine if it needs new vanes and oil, or just new oil. It should be a beast of a roughing pump.
