Welch 1402 advice Please

Check the group archives with google for a fairly recent (6 months, maybe) thread about a Welch 1405 or 1402 in the subject line. Someone was asking about an inlet chamber in one post.

Those threads don't sound common for any types of fittings that I'm familiar with, but check around at auto parts stores, plumbing places, or appliance/HVAC parts suppliers and maybe you'll find a fitting that you can adapt barbs to.

Maybe you've already reviewed the Welch site, but I think there were some application/operation PDF files about general operating procedures for their pumps.

WB ...............

In the exhaust port.

Check the vapor pressure of teh oil you have, if it is for direct drive vacuum pumps it should work fine. I run the Leybold direct drive oil in belt driven pumps and it works fine. The belt drive ones run at a lower speed so if the oil will stand up to direct drives it will work in a welch pump.

That's a toughie. If you cannot find one from a surplus pump place, you could thread a piece of brass tubing (there *may* be an NPT size that is close in OD) to be 20 tpi and then seal with something like epoxy.

Jim

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Pour it into the exhaust port.

has the nipples for $20 each. Their prices on oil and other stuff are usually very good; I've used a lot of their conflat flange copper gaskets over the years, and they sell all the parts to rebuild your pump when you need to.

-- Regards, Carl Ijames carl.ijames at verizon.net

Ooh. Forgot those folks. They're the ones keeping my vintage veeco leak checker running. Very good service.

Jim

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Someone else may correct me, but I think that any oil will be good enough for your application. That is I don't think you will notice the difference between a 5 mm hg vacuum and a 5 micron hg vacuum for degassing resins.

Dan

If a motor oil has higher vapor pressure constituents those will be pumped away, possibly compromising the lubrication qualities of the oil.

Oils in vacuum pumps have to seal, they have to have appropriate vapor pressures for teh application, and they have to lubricate - all of these at the operating temperature of the pump, and without degrading over time.

If I were him I would charge the pump once with a reasonable quality vacuuum pump oil, and run it with the gas ballast valve open as a rule, because he will be pumping a fair amount of water vapor and also whatever comes out of his epoxy resin, which is most likely condensible.

Jim

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Jim has forgotten more about vacuum systems than I have ever known. But I can remember reading about using an ordinary motor oil ( probably non-detergent and I am pretty sure it was a single grade oil like SAE 30 ) in a vacuum pump. The article said the brand and grade, but since I probably read it before Jim was born, I can not remember the details.

Dan

Many of the older piston pumps used straight-weight motor oil. Actually a check of a leybold, alcatel or pfeiffer vaccum site might pin down the answer to this question.

Jim

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I know people who have used 10w30 mobil 1 but they didn't have good gauges so I don't know what base pressure they got. For degassing urethane it would definitely be good enough. Regular motor oils have additives to get the multiweight rating so you would want a straight sae

30, but the synthetics don't need additives for the 10w rating. I would definitely expect the synthetic oil to have fewer volatile components. The standard distilled/refined mineral oil for direct drive pumps usually has a 19 in the name, like the TV019 someone else mentioned, or Inland 19, or Invoil 19, etc. This is advertised as either the same as or one step "better" oil than the duoseal oil used in lower speed belt drive pumps, which works well in either direct drive or belt drive pumps. I'm sure you can find a data sheet somewhere online, to get a viscosity rating, which you can then compare to the motor oil scale to see if 30 weight is really the best. Oh, heck, the Lakers just didled away a lead and went to overtime so hang on a sec - okay, I'm back. From (another good source of vacuum stuff), they give viscosity specs on inland 19 of 54 cst (251 SUS) at 40 deg C and 8.1 cst (52.7 SUS) at 100 deg C. Normal pump operating temps are in the warm to just too hot to touch range, or 40-70 deg C. I found which gives viscosities of 9.6-12.9 cst at 99 deg C for SAE 30 and 5.7-9.6 cst at 99 deg C for SAE 20 motor oil, so SAE 30 may be just a tick on the thick side but given it's availability I wouldn't hesitate to try it. I also found a listing for Mobil 1 10W30 as 59 cst at 40 and 10 at 100 deg C, so it's on the thin side of 30 weights and should work okay. Well, the Lakers managed to get the win so I'll stop typing :-).

-- Regards, Carl Ijames carl.ijames at verizon.net

I did a little googling and found <

. Becker does not make high vacuum pump, but does say their pumps operate at 0.4 Torr. So not too bad and certainly good enough for degassing.

Dan

I think I goofed the URL for the info on oils. It is

< >

The last bit is Tee Dee One for tech doc one. At the very end is a list of various companies and the oil Becker recommends.

Dan

1)&3) As others have said, in the exhaust port, there should be an oil level glass on one edge of the pump body amd a drain plug right below. Usually there's an aluminum baffle dingus screwed in the exhaust that looks like a knob. This has the screwy 20 TPI thread on it. On my Welch, the intake is a standard pipe thread, I was able to screw in the adapter tree for evacuating car AC systems with no adapters needed. Might be there was already a reducer in the port, if so, it was painted and gunked up to match the body, because I sure don't remember seeing it. You can also buy, at great cost, a muffler/oil filter for the exhaust port that supposed to cut down the oil mist and the noise. I'd like to make one up, but haven't gotten to it yet. I'd recommend not restricting the outlet with a hose barb, back pressure is NOT a good thing on these units. 2) I use Mobil Vacuum Pump Oil. I got this at MSC, it was about $1.50/qt. They had it on the shelf at the local outlet, so no shipping. From my purposes it worked fine, it's probably meant for dairy operations and the like. I can get down to the range I need to dry out the car AC, so it's good enough.

One thing I'm setting up is a reservoir tank set, I'll pump those down with the inlet shut off, then I can get instant vacuum on my project when I open the inlet ball valve. I'm thinking of using it on stuff like small vacuum forming frames and epoxy degassing bell jars where you need vacuum pronto and can't wait for pump down. I've got a set of tanks of about 50 liters total volume, that should be enough for what I want to do.

Stan

[ ... ]

That sounds useful -- but be careful. Tanks made for pressure may not be capable of handling a vacuum well. Somewhere out there there is a photo that someone posted a link to here a few years ago. It was a tank car -- for natural gas, I think -- which had been undergoing a steam cleaning when quitting time came. Someone just shut the valves on it, while it was still loaded with steam, and went home. The steam condensed, making a partial vacuum, and the tank car crumpled. from the pressure differential.

Enjoy, DoN.