Vacuum source using refrigerator compressor

[Rivea]

I want to do some vacuum distillations to reduce the boiling temperature of some solvents. I had an old working refrigerator compressor laying around in my shop. To regulate the amount of vacuum applied to the distillation apparatus, I have provided a needle valve and a large vacuum gauge. I have invested about $50 into the project for a large gauge, an accumulator to prevent fluid from being sucked into the compressor, along with some copper fittings and pipe.

I have not tried this beast yet for distillations, but it does pull a damn hard vacuum at about 29.5 inches Hg. I have used it to evacuate an auto A/C unit that I repaired, and it worked beautifully.

I will report on its use in a distillation in the near future. Here are a couple of photos if anyone is curious about building one similar to it.

 

[Oncewas]

That's awesome! Looks nice and solid man. I love when an idea is born into a creation cool stuff . 29.5 inches of mercury is solid! Humms like a refrigerator nice and quiet. Dang I need to get myself an old refrigerator .

 

[Xt]

Looks nice and vintage... very 'steampunk'. Top work!

 

[Crystalito]

Could you please provide some general instructions on the building of such a device? I have seen some instructions online here and there but i would like to know more, from someone with first hand experience.

 

[Trickster]

I want to do some vacuum distillations to reduce the boiling temperature of some solvents. I had an old working refrigerator compressor laying around in my shop. To regulate the amount of vacuum applied to the distillation apparatus, I have provided a needle valve and a large vacuum gauge. I have invested about $50 into the project for a large gauge, an accumulator to prevent fluid from being sucked into the compressor, along with some copper fittings and pipe.

Nice design. Those I saw before were quite crudely made.

A word of caution. There is a known issue with vacuum pumps made of refrigerator pumps - lubrication. It is not a problem if a liquid coolant is used because a small amount of oil is added to it. But if you run it dry for some time it may seize.

 

[Rivea]

I want to do some vacuum distillations to reduce the boiling temperature of some solvents. I had an old working refrigerator compressor laying around in my shop. To regulate the amount of vacuum applied to the distillation apparatus, I have provided a needle valve and a large vacuum gauge. I have invested about $50 into the project for a large gauge, an accumulator to prevent fluid from being sucked into the compressor, along with some copper fittings and pipe.

Nice design. Those I saw before were quite crudely made.

A word of caution. There is a known issue with vacuum pumps made of refrigerator pumps - lubrication. It is not a problem if a liquid coolant is used because a small amount of oil is added to it. But if you run it dry for some time it may seize.

Trickster,

You're right about oiling. Normally in its closed loop operation in a refrigerator some of the lubricant circulates through the entire closed system (compressor, condenser, capillary tube, and evaporator). Occasionally one needs to inject some refrigerant lube into the compressor input port to avoid seizing the compressor. It need be only a minimal amount of lube. I have run this compressor perhaps 20 times over the last 15 years and have not lubed it. I have used it to primarily to evacuate auto A/C systems which takes a couple of hours. To avoid seizing it I'll put a 1/2 ounce of lube in the inlet port prior to its next use.

If the compressor is from a refrigerator prior to 1994 in the US, it used R12 refrigerant and mineral oil based lube. Post 1994 the systems started using R-134A refrigerant and PAG type lubricant.