Master Diver

Diving Equipment

Open circuit demand scuba is the most commonly used by recreational divers, but closed circuit and semi-closed rebreathers are now available.

Test Pressure: the pressure to which the cylinder is subjected to during hydrostatic testing. For a 200 bar cylinder it is 300 bars, for a 232 bar cylinder it is 348 bars.

If internal inspection reveals corrosion, it may have to be cleaned by tumbling. The tumbling process involves filling the cylinder approximately half full of an abrasive material such as carbide chips, or aluminum oxide chips, and rotating it for a number of hours.

A dual valve for a single cylinder, known as a Y-valve, or an H-valve, allows a diver to mount 2 regulator systems on a single cylinder.

The first stage reduces cylinder pressure to an intermediate pressure (or low pressure) of approximately 90-150 psi (6 to 10 bar).

The second stage reduces the intermediate (low) pressure to ambient pressure.

Because of their tendency to fail in a closed position, upstream valves are rare in modern scuba regulators.

In a Balanced Valve regulator the operation of the regulator is independent of the cylinder or applied pressure. (Breathes the same at low tank pressure)

The internal valves of scuba regulator first stages are available in 2 basic types, diaphragm and piston.

The main valve of a Pilot Valve regulator is opened and closed with air pressure, rather than mechanical leverage.

Some regulators may not be capable of delivering high flow rates at low cylinder pressures when two divers are breathing from it at the same time in an emergency air sharing situation.

Regulator performance evaluation has traditionally been based on breathing resistance or effort.

Modern regulator performance is defined in terms of maximum respiratory work level or breathing work.

If both ends of a