FAQ - Venting your mechanical fore pump

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Richard Hull
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Real name: Richard Hull

FAQ - Venting your mechanical fore pump

Post by Richard Hull » Tue Feb 28, 2017 12:29 pm

If your mechanical fore pump is located in your home, especially in a common living area, you must attach an oil mist filter to your vent or exhaust line of the pump. These are commonly obtained from various professional vacuum specialty dealers and some refrigeration supply houses. Inside a dwelling, a pump working for long periods, without a mist filter attached, will fill the room with an oil mist which will be inhaled by all present.

The very best, long term, solution is to vent the pump's exhaust and oil mist to the outside world, (no mist filter needed). A line must be constructed from the exhaust of the pump through a hole cut in the wall of the home, garage or out building where the pump is located and run. This line should be as short as possible. Thus, the closer the pump is located to an outside wall, the better. The line should be on a level with the exhaust port or, better still, directed in some sort of incline down from the exhaust port to the hole in the building. As the oil mist is to be pumped to the outside world, stuff from the outside world will be free to enter the exhaust port of your pump and the oil, fouling it. The two most common bad items are curious bugs seeking shelter or a home and moist air in humid conditions. In good, scientific vacuum work and practices bugs and water in the pump oil is generally frowned upon.

I thought about these issues of bug entry and water vapor getting into my oil and line way back in 2004, the day I put in the copper vent pipe line.

My method:

I used commonly found 1/2-inch copper pipe and related fittings found at most any hardware outlet on the planet.

I took a right angle copper bend and soldered a piece of fine copper screen wire to one end-arm. I then slipped the open arm onto a 6" length of matching copper pipe and sweat soldered it to the screened bend. The pipe exits my lab with only a 1" stub sticking out of the building. (The screened end of the right angle is turned down towards the ground, obviously.) I used a pliable clay rope, (a form of putty), found at hardware stores to mold and ooze around the small air space around the hole to seal the pipe and make it weather and bug tight through its exit hole. All of the remaining short lengths of pipe and small ball valve in this vent line are just slide fits, within the lab. In this manner, when new oil is added I can just slip the parts loose from the vent opening/oil fill port on my precision fore pump. The ball valve in the line is left closed when the pump is not on to prevent our typical muggy moist air from foiling the oil. In this manner I have had no bugs or airborne moisture enter the oil-fill vent opening in the pump for the last 13 years.

Note: adapting the line to your pump's exhaust port is up to you and will vary considerably from pump to pump. Typically, manufacturers use a common pipe thread for their vent hole and adapters, usually brass, from this large thread to a pipe nipple or a smaller threaded pipe hole are found at plumbing specific hardware dealers.

Super tiny midges and the like, entering through the fine screen openings would, in theory, immediately stick to the thin film in the oily copper line due to the viscosity of the oil and die. I have changed oil exactly 4 times since 2004. Each time, the old pump oil is rather clean and free of debris. Likewise, I clean out all of the 4 slide fit pieces in the lab with acetone and observe the liquid that washes them out and not even midges, other "buglettes" or their body parts are seen. Thus, this system seems to be working just fine for me.

Mom and dad will not let the younger folks here bore a hole in the house walls to the outside and this is where a mist filter is a must have item as noted above. All fusor work will cease if mom comes in to pick up your dirty clothes while you are running your pump and sees a fog in your room.......Nervous Nelly's, those parents. The thought of you filling your lungs, long term, with oil distracts them a bit.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Joined: Mon Nov 28, 2016 7:48 am
Real name: Ian Krase

Re: FAQ - Venting your mechanical fore pump

Post by ian_krase » Sat Mar 04, 2017 6:36 am

Many commercial oil mist filters are pretty pricey.

McMaster sells a line of low-cost oil mist filters / mufflers, https://www.mcmaster.com/#exhaust-mufflers/=16lqm45, but I haven't tried them.

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