Royal; Navy CDBA Rebreather Gas System

Royal Navy CDBA Rebreather Back-Mounted Cylinder Subsystem

The twin cylinders of the back-gas assembly are carried by the main chassis vest of the rig, just below the weighting pocket.

Attachment is by an aluminum pin with a flip-lever for locking the pin into place. As with the rest of the rig, no tools are needed for servicing.

The cylinders feed the manifold block, which carries the pressure reduction regulator, interchangeable orifice, and bypass valve.

The regulator is a constant pressure regulator, for obtaining constant mass flow. The bypass valve has a black plastic guard that prevents inadvertent opening in service.

Orifices are provided for Nitrox and Oxygen. Even when diving the rig as a pure 02 rebreather, a slight trickle of 02 is continuously provided to the loop.

Each orifice has an integral filter, and is inserted into the main manifold block for use.

Gas is carried to the rig through a high pressure hose, which connects to the counterlung.

Here is the entire gas system. Imagine the diver facing to the left, the gas manifold would lay along the divers left hip, with the bottles across the small of his back and the hose running up along the front of his chest to the counterlung feed port.

Detail view of the on/off valve on the cylinders, and the gas manifold with regulator and bypass.

Supply hose feeds the counterlung, and is retained by a 90-degree bayonet fitting, which is impossible to remove once the system is secured in position.

The gas system of the CDBA is a simple constant mass flow system with bypass. The system is industrial in nature, with all components being oversized, and with construction being of heavy brass billets machined to shape. Durability was obviously the watchword here, and no expense was spared to manufacture a robust system.

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		The twin cylinders of the back-gas assembly are carried by the main chassis vest of the rig, just below the weighting pocket.
		Attachment is by an aluminum pin with a flip-lever for locking the pin into place. As with the rest of the rig, no tools are needed for servicing.
		The cylinders feed the manifold block, which carries the pressure reduction regulator, interchangeable orifice, and bypass valve.
		The regulator is a constant pressure regulator, for obtaining constant mass flow. The bypass valve has a black plastic guard that prevents inadvertent opening in service.
		Orifices are provided for Nitrox and Oxygen. Even when diving the rig as a pure 02 rebreather, a slight trickle of 02 is continuously provided to the loop.
		Each orifice has an integral filter, and is inserted into the main manifold block for use.
		Gas is carried to the rig through a high pressure hose, which connects to the counterlung.
		Here is the entire gas system. Imagine the diver facing to the left, the gas manifold would lay along the divers left hip, with the bottles across the small of his back and the hose running up along the front of his chest to the counterlung feed port.
		Detail view of the on/off valve on the cylinders, and the gas manifold with regulator and bypass.
		Supply hose feeds the counterlung, and is retained by a 90-degree bayonet fitting, which is impossible to remove once the system is secured in position.