Dräger FGT-III (FGT3) (FGG III)

The fibreglass reinforced polyester casing contains the twin breathing bags, the refillable soda lime canister, the pressure reducer dosage block, and the two gas cylinders. According to the diving depth one of the three constant dosages can be selected. The apparatus can be used to a maximum diving depth of 200m. The duration can be prolonged by supplementary gas supply from a diving bell or from the surface.

 Weight:  28 kg

 Breathing lime canister volume: ~ 3 kg

 Cylinder charging pressure:     200 bar

 Cylinder capacity (each):         4 litres

The dosage block is an orifice type with an intermediate pressure of 40 bar absolute. There are three dosage settings.

Typical usage would be:

 Diving depth:   50-110m (with max. 1,4bar ppO2: -70m)

 Gas mixture:    17.5% Oxygen, 82.5% Helium

 Flow rate :     30 bar*l/min (position 1)

 Duration:       42 min



 Diving depth:   90-160m (with max. 1,4bar ppO2: 14-100m)

 Gas mixture:    12.5% Oxygen, 87.5% Helium

 Flow rate:      40 bar*l/min (position 2)

 Duration:       32 min



 Diving depth:   140-200m (with max. 1,4bar ppO2: 21-130m)

 Gas mixture:    10% Oxygen, 90% Helium

 Flow rate:      50 bar*l/min (position 3)

 Duration:       25 min

These durations may appear to be very short, but remember, these units are designed to do the bottom portion of the dive only, decompression is intended to be carried out in a chamber. The advantage of these units in the depths they are designed for is not extended bottom time, but the great saving in gas volume used. If long bottom times are required, the umbilical can be used. The umbilical connection is via a hose mounted on the right hand side of the case. The hose has a one way valve fitted so if the umbilical supply fails, the gas from the autonomous cylinders will not escape. When operating on the umbilical the necessary supply cylinders and another dosage block are installed in the diving chamber. The on-board cylinders and dosage block then serve as an emergency bail-out.

Jason has been using the unit with nitrox mixes, and because nitrox mixes are more dense than the prescribed helium mixes, the flow rates are lower. They are:

 Position 1:   8   bar*l/min

 Position 2:  10.5 bar*l/min

 Position 3:  21   bar*l/min