Diving air compressor

Diving air compressor

A small stationary high pressure diving air compressor installation
Other names	Breathing air compressor
Uses	Filling dive cylinders (high pressure) Provision of surface supplied breathing air (low pressure)

A diving air compressor is a breathing air compressor that can provide breathing air directly to a surface-supplied diver, or fill diving cylinders with high-pressure air pure enough to be used as a hyperbaric breathing gas. A low pressure diving air compressor usually has a delivery pressure of up to 30 bar, which is regulated to suit the depth of the dive. A high pressure diving compressor has a delivery pressure which is usually over 150 bar, and is commonly between 200 and 300 bar. The pressure is limited by an overpressure valve which may be adjustable.

Most high pressure diving air compressors are oil-lubricated multi-stage piston compressors with inter-stage cooling and condensation traps. Low pressure compressors may be single or two-stage, and may use other mechanisms besides reciprocating pistons. When the inlet pressure is above ambient pressure the machine is known as a gas booster pump.

The output air must usually be filtered to control purity to a level appropriate for breathing gas at the relevant diving depth. Breathing gas purity standards are published to ensure that the gas is safe. It may also be necessary to filter the intake air, to remove particulates, and in some environments it may be necessary to remove carbon dioxide, using a scrubber. The quality of the inlet air is critical to the quality of the product as many types of impurity are impracticable to remove after compression. Condensed water vapour is usually removed between stages after cooling the compressed air to improve efficiency of compression.

High pressure compressors may be set up with large storage cylinders and a filling panel for portable cylinders, and may be associated with gas blending equipment. Low pressure diving compressors usually supply compressed air to a gas distribution panel via a volume tank, which helps compensate for fluctuations in supply and demand.^[1] Air from the gas panel is supplied to the diver through the diver's umbilical.