BradC
15-01-2012, 05:39 AM
G'day all,
I'm doing some experimentation looking at the outgassing of various thread sealants. To do this I'm trying to hold a vacuum under 100 microns on a brand new recovery cylinder. I'm having trouble holding a vacuum however.
Now, as I do this as a hobby, most of my kit is cheap E-bay garbage excepting :
- All ball valves are CPS
- Valve core remover / isolation valve is a CD3930
- Vacuum gauge is a Fieldpiece SVG2
As an asside, I had a "cheap" chinese vacuum gauge which measured in "Microns" and when I put it up against the SVG2 it turns out the cheap gauge plumets toward absolute vacuum somewhere around 2000 microns on the SVG2. The best part is I paid more for the cheap gauge 2 years ago than I did for the SVG2.
Connecting the SVG2 directly to my Vac pump using a small 1/4" copper hard line gives me about 37 Microns (when it's nice and hot with fresh oil). Putting any of my valves between the pump and the SVG2 gives me about the same base reading, but when I close the valve to isolate, the SVG2 steadily increases until it's off the scale (> 2000 microns). So that indicates to me either my flares are leaking or the ball valve is leaking. The flares look clean, have a decent looking seating surface and are torqued properly. Replacing the hard line with any of my hoses gives the same but slower results (more volume in a hose I guess).
I've seen vacuum grease advertised around. Should I be using that on the connectors?
My hoses are cheap e-bay specials (but with new CPS gaskets). Can someone recommend me some real hoses that are likely to hold < 100 microns vacuum?
Are there ball valves that are Vac rated?
Basically it appears I've reached the limits of my cheap-o gear and I'm looking for some affordable real-mans gear.
As another observation, I've been using my vac pump (cheap e-bay 2 stager) on and off for the last 2 years, but probably with a combined run time of less than 24 hours. When I started this little exercise I was getting ~200 microns vac from it. After about 3 days of continuous running and a couple of extra oil changes I now see 37 microns. Obviously it needed a good run-in.
I'm doing some experimentation looking at the outgassing of various thread sealants. To do this I'm trying to hold a vacuum under 100 microns on a brand new recovery cylinder. I'm having trouble holding a vacuum however.
Now, as I do this as a hobby, most of my kit is cheap E-bay garbage excepting :
- All ball valves are CPS
- Valve core remover / isolation valve is a CD3930
- Vacuum gauge is a Fieldpiece SVG2
As an asside, I had a "cheap" chinese vacuum gauge which measured in "Microns" and when I put it up against the SVG2 it turns out the cheap gauge plumets toward absolute vacuum somewhere around 2000 microns on the SVG2. The best part is I paid more for the cheap gauge 2 years ago than I did for the SVG2.
Connecting the SVG2 directly to my Vac pump using a small 1/4" copper hard line gives me about 37 Microns (when it's nice and hot with fresh oil). Putting any of my valves between the pump and the SVG2 gives me about the same base reading, but when I close the valve to isolate, the SVG2 steadily increases until it's off the scale (> 2000 microns). So that indicates to me either my flares are leaking or the ball valve is leaking. The flares look clean, have a decent looking seating surface and are torqued properly. Replacing the hard line with any of my hoses gives the same but slower results (more volume in a hose I guess).
I've seen vacuum grease advertised around. Should I be using that on the connectors?
My hoses are cheap e-bay specials (but with new CPS gaskets). Can someone recommend me some real hoses that are likely to hold < 100 microns vacuum?
Are there ball valves that are Vac rated?
Basically it appears I've reached the limits of my cheap-o gear and I'm looking for some affordable real-mans gear.
As another observation, I've been using my vac pump (cheap e-bay 2 stager) on and off for the last 2 years, but probably with a combined run time of less than 24 hours. When I started this little exercise I was getting ~200 microns vac from it. After about 3 days of continuous running and a couple of extra oil changes I now see 37 microns. Obviously it needed a good run-in.