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The Diving Air Compressor has Become Our Friends

2016-01-18 15:31

The compressor is a kind of the driven fluid machinery which can lift the low pressure gas up to the high-pressure gas. It's the heart of the refrigeration system, inhaling the refrigerant gas of the low temperature and low pressure from the suction tube, compressed by the motor driving the piston, exhausting the refrigerant gas of the high temperature and high pressure to the discharge pipe, provide a power for the refrigeration cycle, so as to realize the compression, condensation, expansion and evaporation (endothermic) refrigeration cycle.
 
But if you were breathing under water, you would carry an air-tank filled with compressed air. For recreational diving this is normally normal atmospheric air, but compressed about 200 times to 200 bars (or 3000 psi). The scuba diver uses a pressure regulator (in their mouth piece) to bring back the air from the high pressure to atmospheric pressure (when at the surface) or the local underwater pressure, depending on the depth.
 
There is nothing special about the air. It's just normal atmospheric air which is compressed 200 times, so you can take more of it with you on your underwater trip. The compression is done by a scuba air compressor.
 
Obviously, the job of the scuba air compressor is to compress the air from 1 bar atmospheric pressure to about 200 bars.
 
Of course, we don't want any oil, chemicals or dust to contaminate the air. We also want a compressor that can produce up to 200 bar of pressure at a reasonable flow rate, so it doesn't take too long to fill-up the scuba tanks.
 
Since the compressor is usually located at the back of the dive-shop. And the dive-shop is usually located on a nice, white, tropical beach... so compressor noises can be a problem.
 
In short: our perfect scuba air compressor produces clean, dry, oil-free air, and lots of it without making any sound. Of course, these are impossible, but let's check out the possibilities and issues that can come up when buying, installing or using a compressor for scuba air.
 
Then let's have a look at the compressor types: When shopping for a scuba air compressor, you will notice there are different types of air compressors, all with different price-tags. Their working principle is not different than other industrial reciprocating piston compressor, except that they have more stages, to be able to create the high pressure of 200 bars.
 
A basic distinction can be made between oil-lubricated and oil-free diving air compressors. The oil-free type uses special ceramic cylinder liners and rings which require no lubrication. The big advantage of course is that there is no compressor oil, so there is no chance of contamination of the breathing air. But, of course, they are a lot more expensive compared to oil-lubricated compressors.
 
The oil-lubricated type is the most common kind of compressor and much cheaper compared to oil-free compressor types. This type uses oil to lubricate the moving parts and the inside of the cylinder. This means that the breathing air comes in contact with the oil, and there will always be a little oil that leaves the compressor together with the air (called oil-carry-over).
 
This oil (although a very small amount per liter air) needs to be removed, for the obvious reasons. This is done by the use of special filters. There are filters for dust, water and oil.
 
Now in the market, there are the Hookah Diving Air Compressor, Low Pressure Dive Compressor, and Scuba Diving Air Compressor. If you want to carry it along with you, you can buy either the Portable Breathing Air Compressor or Portable Scuba Diving Air Compressor.