# Vacuum Operated Switch for my Vacuum Filter System



## kadriver (Dec 18, 2012)

I have spent hours sitting in front of my vacuum filter flask manually operating the pump turning it on and of to maintain a set range of vacuum going to the filter flask.

I have had filter paper failures when filtering solution with acid or hot solutions if the vacuum was allowed to get too high.

So would sit there and turn the vacuum pimp on, let the vacuum get to 10 incheds Hg, then turn it off.

After it bleeds down to 5 inches Hg, I turn it back on to charge the vacuum back up to 10 inches Hg, then turn it off again.

I do this to avoid rupturing the filter paper with too high a vacuum, or allowing the vacuum to go to zero and risk unfiltered solution lifting the filter paper and allowing unfiltered solution to get into the flask. 

I have spent hours sitting in from of that flask watching it drip drip drip.

I was able to get a nice vacuum operated swith that is adjustable. I installed it today so now I am free to do other things when vacuum filtering.

The switch senses the amount of vacuum at the flask, turns the vac pump off when vacuum reaches 10 inches Hg, then turns it back on again at 5 inches Hg.

I installed a valve to isolate the switch. If I want full vacuum on the flask I just shut the valve to the vac switch.

This feature is right up there with my fumedood installation - seems like I got a whole new shop from just this little installation.

The vacuum switch is brand new and it cost me $55 on Ebay - took about 45 minutes to install.

kadriver


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## Barren Realms 007 (Dec 18, 2012)

Did you consider a vacume regulator similar to a pressure regulator, and also adding a reserve tank. These things will keep your pump from continuously starting and stopping and will extend it's life.


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## kadriver (Dec 18, 2012)

Yes, my filter cart has an 8 gallon air compressor tank with the check valve (a valve that allows flow in one direction only) drilled out. The vacuum pump draws on the tank. Then a 15 foot section of air hose communicates the vacuum in the tank to the filter flask and vacuum switch. The tank acts as a vacuum reservoir. 

The switch cycled every 10 seconds or so with just a wet filter paper in the buchner funnel.

When doing some actual filtering, the time between cycles will be much greater as the filter paper gets loaded up from the solids being filtered out.

If I used a vacuum regulator, then the vacuum pump would run continuously and the regulator would break the vacuum continuously causing a continuous hissing sound - If it is the type regulator that I am thinking of. 

Using this vacuum operated switch is better (in my opinion) because it actually controls the motor on the vacuum pump turining it on and off automatically.

The switch is actually replacing me - I used to do this job manually which required ny attention. Now I am free to walk away and do other tasks during a filter operation and the vacuum pump will cycle automatically.

The dead band range (range in inches Hg that the power stays off) is about 5 inches (even though the switch is advertised at 1 to 2 inches Hg). Plus I can adjust the dead band to any point that I want between 0 to 30 inches Hg.

I once added HCl to some inquarted gold that had not been washed free of silver nitrate from the nitric acid treatments. I knew I had made the mistake as soon as I poured in the HCl - a ton of silver chloride formed.

I could have dissolved all the silver chloride with ammonia (but this was before I even knew that silver chloride would readily dissolve in ammonia).

I spent about 8 hours trying to filter out the silver chloride after adding nitric to dissolve the gold. The whole time I sat there, reading a book titled, "Refining Precious Metals Waste" by C.M. Hoke, and cycling that vac pump.

Now the vacuum switch will automatically cycle the vacuum pump for me.

kadriver


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## scrappile (Dec 23, 2012)

kadriver said:


> Yes, my filter cart has an 8 gallon air compressor tank with the check valve (a valve that allows flow in one direction only) drilled out. The vacuum pump draws on the tank. Then a 15 foot section of air hose communicates the vacuum in the tank to the filter flask and vacuum switch. The tank acts as a vacuum reservoir.
> 
> The switch cycled every 10 seconds or so with just a wet filter paper in the buchner funnel.
> 
> ...


 

Duty cycle on the motor may not take that manny starts per hour,

in rush current can be 6 to 10 times running, heat is created and it breaks down insulation, if it is you might want to add cooling fans to help. just a thought when I saw 10 seconds , also air line may not hold vacuum and be closing if funnels is clear,. may not even be an issue on small motors, just check for heat after some starts, :!:

edit for maybe no need after looking again, 8)


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## kadriver (Dec 25, 2012)

Ok, I will keep an eye on the heat. I have not used it yet.

Thanks - kadriver


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## kadriver (Jan 29, 2013)

I have been using this and really am pleased with how it works.

I can fill the funnel with my solution, cut in the vacuum switch and turn on the vacuum pump, then go about doing other tasks.

It cycles about once evey 45 seconds or so, depending on the amount of solids glogging the filter paper.

Its like having a breath of fresh air in my shop, instead of being a slave to the on/off switch.

kadriver


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