Pressure
Diving compressors generally fall into one of two categories: those used for surface supplied diving and those used for filling scuba diving cylinders.
Surface supplied diving compressors are low-pressure and high-volume. They supply breathing gas directly to a diver, from a control station called a "rack" via a hose called an "umbilical". Their output is generally between 6 and 20 bar /100 and 300 psi. These compressors are often very large and powerful, because they must be able to deliver gas at a sufficient pressure and volume to multiple divers working at depths of several hundred feet as the divers breathe.
Compressors used in scuba are high-pressure and low-volume. They fill diving cylinders and storage flasks or banks of storage flasks. These compressors are generally smaller and less powerful because the volume of gas they deliver is not so critical; a lower volume compressor can be used to fill large storage flasks during the long periods of the day when demand is low. This stored compressed air can be decanted into diving cylinders when needed. Common scuba diving cylinder pressures are 232 bar / 3000 psi and 300 bar / 4500 psi.
Read more about this topic: Diving Air Compressor
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