Three Types of Scuba Apparatus

The arrangement of the component parts varies considerably among the different makes of scuba. If you are going to use an unfamiliar scuba, the instruction manual should be studied, and if at all possible, some instruction should first be taken from a person who is qualified in the use of that particular scuba.

The united states divers’ corporation aqualung: In this scuba, the first-stage regulator, demand valve regulator, and exhaust valve, form an integral unit mounted on the high-pressure manifold attached to the cylinders. The cylinders are worn on the back and are fastened to the diver by means of a harness assembly. They are worn with the manifold up, so that the demand regulator rides the back of the neck. A corrugated breathing tube supplies air from the demand regulator to the mouthpiece. Another corrugated tube carries the exhaled gases from the mouthpiece to the exhaust valve, which discharges the gases to the water. The position of the exhaust valve close to the demand regulator diaphragm minimizes the difference in pressure (water pressure) between the two, so that inhalation and exhalation occur at nearly identical water pressure. The air-reserve mechanism is integral with the manifold and is located above one of the cylinders. It is manually operated by means of a pull rod.

The scott aviation corporation hydro-par: This apparatus uses a completely different arrangement of components from the aqualung. The cylinders are secured to a back plate which has a shoulder harness for attachment. The cylinders may be worn with the cylinder stop valves up or down. The first-stage regulator is integral with the high-pressure manifold mounted on the cylinders, and reduces cylinder pressure to about 100 pounds per square inch over bottom pressure. A medium-pressure hose supplies this low-pressure air to the demand regulator. The demand regulator is mounted directly into a molded housing on the right side of the mask, which replaces the mouthpiece. The exhaust valve is mounted similarly into the left side of the mask. A special-pressure balancing mechanism subjects the exhaust valve to demand regulator pressure and compensates for pressure differences between the two locations. The air-reserve mechanism on the Hydro-Pak is located in the first-stage regulator and is operated by a knurled knob mounted on top of the first-stage regulator.

The Hydro-Pak contains an added feature not found in the aqualung or air lung. It has a water-ejection button which is used to clear the mask if it should become flooded. This button is located on the demand regulator. Pushing the button depresses the diaphragm, causing a free flow of air to enter the mask and force out the water. Hook a finger under the mask to let the water out in this process, because the pressure-balancing mechanism locks the exhaust valve shut during this operation. The water-ejection button is useful for clearing large amounts of water, or at any time that a free flow of air is desirable. You can clear small amounts of water by tilting the head to the left and draining water through the exhaust valve by exhaling.

The northill company air lung: This equipment uses the same arrangement of components as the aqualung, with some differences. It has no intermediate-pressure stage because the demand regulator is especially designed to work directly from cylinder pressure. Furthermore, the exhaust valve is integral with the demand regulator diaphragm, and exhaust occurs through the diaphragm from a chamber which is isolated from the demand valve itself. This subjects the demand regulator and the exhaust valve to exactly the same hydrostatic (water) pressure. The location of the air reserve mechanism on the airlung is also different. The mechanism is an integral part of the demand regulator and is manually operated by means of a lanyard attached to a lever.

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