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Old Style Welch 1402 Gas Ballast Question

Posted: Wed Mar 22, 2023 9:20 pm
by Kevin Black
Hello all, this is my first post here.

I am having difficulty finding an instruction manual for old-style Welch 1402 Duo-Seal vacuum pump. The pump I am trying to find a manual for has the gas ballast on top, not off to the side. The gas ballast on the pump I have has a hole through some threads and a threaded cap with a hole in it also. This hole is somewhat visible in the second picture of the correct valve type.

Correct Ballast Pic 1:
https://imgur.com/a/abNI4dD

Correct Ballast Pic 2:
https://imgur.com/a/YQVAqt6

An Example of an Incorrect Ballast:
https://imgur.com/a/MGhnrVV

I am particularly interested in finding an exploded view of the pump with the top mounted type of gas ballast. Any help will be appreciated. Thanks in advance,

Kevin

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Thu Mar 23, 2023 8:24 am
by Rich Gorski
Kevin,

Here's the 1402 manual.
welch duoseal manual.pdf
(1.3 MiB) Downloaded 142 times
I've been running mine for many years. They last forever and reaches 20 mTorr pressure. See Page 7 for info on the gas ballast. I haven't used a gas ballast on it only a filter so your not breathing the oil exhaust. If you just got it change the oil and don't overfill.

Rich G.

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Thu Mar 23, 2023 12:28 pm
by Kevin Black
Thank you for that link. I was mostly interested in finding a manual for the older style of 1402, the ones that had the ballast valve directly on top, not off to the side. I spoke with Welch and they sent me a manual for a version of the 1402 with the ballast on top, however it was a different type of ballast valve than the pump I was using (or the ballast on the pump I am using is incomplete).

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Thu Mar 23, 2023 3:55 pm
by Rich Gorski
Sorry, try this manual, page 70. 1402 breakdown with ballast valve on top.
welch_owners_manual1975.pdf
(4.36 MiB) Downloaded 121 times
Rich G.

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Thu Mar 23, 2023 5:29 pm
by Frank Sanns
Why the obsession about the gas ballast? Many of us never even use it.

The gas ballast's only function is to bleed some room air into the output stream of the oil and carry away low boiling contaminants. It makes no difference if the sparge gas inlet is on the top or the side, it still goes into the output stream of the second stage of the pump.

The little bit of moisture in a Fusor or a chamber is insignificant in the operation of the pump. If you have large amounts of moisture or other low boiling contaminants, you need to use a cold trap to prevent vapors from contaminating the oil in the first place.

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Sat Mar 25, 2023 4:12 am
by Jerry Biehler
Gas ballast is only needed when pumping condensable gasses, stuff that would condense on the working surfaces of the inside of the pump when in normal operation. If you were using the pump on something like a rotary evaporator you would use it but if you are just pumping air there is no need for it. Even normal amounts of humidity are not enough to warrant it, if you were freeze drying stuff, then it would be used.

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Sat Mar 25, 2023 10:20 am
by Richard Hull
Indoors within a very well sealed system, the ballast is rarely used. However in a shed, shop, or small outbuilding lab that is not maintained at more or less room temp. Condensation is the norm. I always ballast the hell out of my mechanical pump. Last week we had overnight temps of 29 deg F. They a daytime high of 72 deg. F. I thought I might start the pump to just exercise it. I felt the external case and it was damp to the touch! I ballasted for about a half an hour to the outside world and it settled at 10 microns on the foreline. Turned the ballast off and it plunged another 2 microns to 8.

I don't mind ballasting as it saves me thousands of dollars yearly on heating and cooling costs, should I attempt to keep the lab at any sort of livable temperature year round. Ballasting is zero cost and I'm ready to go with no tremendous issues.

Most folks have enough sense to cap and seal tightly both the inlet outlets and filler ports of their disconnected mechanical pumps if left disconnected from a system for a period of time. This avoids outside air, be it moist or contaminated, from getting into the pump. When hooked to the system I ball valve the pump outlet at the pump, which is also the oil filler hole, as it is piped to the outdoors. (the pipe end outside has a fine mesh cover to keep out bugs and debris.) I also have the pump inlet valved off at the pump, isolating it from the turbo. So I only have to worry about rare occasional condensation internally. Moisture has a way of finding its way inside a pump when subjected to a vastly varied thermal range in a region of high typical moisture, (where I live)

Richard Hull

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Sat Mar 25, 2023 2:31 pm
by Frank Sanns
Richard,

I don't understand this process. If the case is cold and you are keeping it sealed up from the moist outside air, how does bubbling moist outside air into the oil through the ballast help? Seems to me, in this scenario, you are doing exactly what you do not want to do.

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Sat Mar 25, 2023 8:25 pm
by Richard Hull
Occasionally, in a senior moment I forget to close the outlet line (rare) but the oil sump remains open for outdoor moisture via the vent pipe and since I rarely run the pump, (maybe every three months) the oil is open to outside air and moisture for 3 months!! Nothing is fool proof.

I always remember to close the outlet when conditioning the pump over a 10 day period. It becomes a routine then. It is the rare demo of one day for visitors in the middle of a long idle period that I might forget as it is the very last thing I am supposed to do. With running conversation at shutdown with visitors, you know how it goes.

Pumps like mine in a lab that goes from cold to hot to cold can take it on the chin provided I do not forget to seal the outlet after operation.
Even when sealed up tight for 3 month to 6 months, I still ballast the first run for about 20 minutes and let the foreline gauge be my guide.

In retrospect how often do you run your pump? I bet 99.8% of those who have a finished, assembled fusor might have 3 months or more between runs. No telling how many have their systems torn down or in storage, never to be heard from again.

In the end no one ever hurt a pump by using the gas ballast.

Richard Hull

Re: Old Style Welch 1402 Gas Ballast Question

Posted: Mon Jul 10, 2023 1:53 pm
by Rich Feldman
This is the freshest thread about Welch Duo-Seal vacuum pumps, so it gets my picture of some seen at flea market yesterday.
With and without belt covers. The one in background might be a different make or model.
20230709_100202.jpg
I think it was the same vendor who had a thermocouple gauge set offered for $25. I was not in buying mode, and would want to excavate garage and take inventory of my vacuum gear before any new procurement.
20230709_100046.jpg