Quote Originally Posted by JMPBautista View Post
Hi. I'm Joe, a 55 years old geophysical engineer and I have a hobby for aircraft static modeling, so I'm looking for ideas to make a homemade tank compressor using a refrigerator type compressor for airbrushing purposes.

The piston and diaphragm types run hot very easily and are too noisy and I need a quiet environment to work.

In the recent past I build up one but I had trouble with an oil mist in the air flow no matter what type of oil filter I used.
I want to know what went wrong in the design and have the opportunity to correct it.

I would appreciate and welcome any ideas.

Thanks

USE A DIAPHRAGM COMPRESSOR OR OILLESS COMPRESSOR. DIRECT DRIVE COMPRESSORS CAN BE NOISY, BELT DRIVEN COMPRESSORS RUN SLOWER AND QUIETER.

WHEN YOU COMPRESS A GAS ITS TEMPERATURE RAISES AS YOU ARE PUTTING THE HEAT OF THE GAS IN A SMALLER VOLUME SO YOU PUT THE HEAT CONTENT INA SMALLER VOLUME AND THE TEMPERATURE RISES. THEN YOU ADD THE TEMPERATURE OF THE COMPRESSOR SO YOU SEE A CONSIDERABLE TEMPERATURE RISE.

REFRIGERATION AIR COMPRESSORS ARE DESIGNED SO THAT THE COLD REFRIGERANT GAS ENTERS THE CRANKCASE FIRST, THEN IS ROUTED TO THE INTAKE VALVE, GOING INTO THE CYLINDER ON THE PISTON DOWN STROKE. IT IS COMPRESSED ON THE UPSTROKE AND IS ROUTED TO THE CONDENSER AS A HOT GAS. CRANKCASE OIL IS CARRIED ALONG WITH THE GAS AND TRAVELS THROUGH THE ENTIRE SYSTEM AND BACK TO THE COMPRESSOR.

IF YOU ARE USING AN OLD PISTON, NOT A HERMETIC COMPRESSOR, ONE WAY TO SEPARATE THE OIL FROM THE GAS WHEN USED AS AN AIR COMPRESSOR IS TO EITHER USE AN OIL/AIR SEPARATOR WITH A BLEED LINE FOR THE OIL TO RETURN TO THE INTAKE OR CRANKCASE.

THAT MIGHT NOT DO A GOOD ENOUGH JOB SO AN ALTERNATIVE WAY IS TO SEPARATE THE INLET AIR FROM THE CRANKCASE, BRING THE AIR IN THROUGH THE INLET SERVICE VALVE RIGHT TO THE CYLINDER HEAD. THE CRANKCASE MUST BE VENTED TO THE ATMOSPHERE OR PRESSURE BUILDUP WILL PUSH OIL PAST THE PISTON RINGS.

HERMETIC COMPRESSORS WILL PUMP OUT ALL THEIR OIL, SO YOU MUST SEPARATE IT FROM THE COMPRESSED AIR AND SEND IT BACK TO THE CRANK CASE.

A SINGLE STAGE COMPRESSOR MUST NOT TO MAKE MORE THAN 150 PSI, 90 PSI IS BETTER. IF YOU EXCEED 150 PSI THE OIL VAPOR IN THE COMPRESSED AIR MAY IGNITE DUE TO THE HEAT OF COMPRESSION, COMPRESSION IGNITION LIKE IN A DIESEL ENGINE. THE BLAST WILL RUIN YOUR DAY, MAYBE YOUR HOUSE.
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