MK15.5 and Eagle units
Colkan International are located in the North East of NSW Aus. and have a large factory producing and servicing rebreathers for the recreational market. Initial based around the MK15 military unit Colkan have created the MK15.5 recreational unit. Colkan have large stocks of spares and can service any MK15 or 15.5.
Colkan are currently in the process of developing a new family of unit called the Eagle ... we will keep you updated to progress as and when available
Brief Overview of the MK15 family
MARK 15 - MOD 0 (Also Civilian CCR-1000)
The Mark 15 Mod 0 utilizes a stainless steel Center Section assembly, and stainless/plastic canister for CO2 scrubber. It also used flexible hoses for both the High Pressure, and Low Pressure lines running from the 1st stages. The 1st stages themselves were placed in the unit "upside down" - or with the tightening nut facing the back of the unit. To load the spheres (which were made of Teflon coated steel) you raised the 1st stages out of the unit, inserted the valves from the spheres, tightened them down, and placed both sphere and 1st stage back into the unit.
The Center Section of the Mark 15 also incorporates a rather low-tech method for gas sealing. Basically, it uses two "rubber bands" that are placed around 1) the Canister, and 2) the Cover. The first, isolated the "dirty" air that had to pass through the scrubber from the "clean" air in the counterlung. The second, sealed the Canister/Counterlung compartment from sea water.
With the introduction of the Mark 15.5, there were some notable improvements, the most notable being the incorporation of a newer, plastic Center Section. It was larger than its predecessor, and had a much more engineered sealing system, using large "o" rings instead of rubber bands. It also had larger bore Inhale and Exhale fittings to accommodate larger bore hoses.
The next improvement, was the elimination of the flexible hoses in the unit, which were replaced by hard tubing. The 1st stages were also "flipped over" and mounted to the unit, eliminating the need to remove them to install the spheres. The Spheres themselves were changed from Teflon-coated steel to Inconel - a non-magnetic metal.
The Mark 16 was the last (so far) to be developed for the Navy, and is still in use today. It had a larger, deeper case, was completely hard-plumbed, had separate O2 and Diluent Addition Ports in the center section (both ports are combined via a manifold on the 15 and 15.5), and also was the first of the units to have true "Voting-Logic" in the electronics.
The Navy also required that the "on/off" switches be removed from the Mark 16 - I have no idea to this day why they did that. The O2 solenoid was also removed, and in its place a piezoelectric solenoid was built in. This eliminated the need for the 50cc Oxygen Collector that is found in the 15 and 15.5’s.
The 1st stages were also modified to operate at higher intermediate pressures. The Mark 15 and 15.5 had intermediate pressures of 130 psi. The Mark 16 regulators were tuned to 275 psi nominal. This allowed the exclusive use of 1/8th inch tubing throughout the Mark 16.
The Mark 16 is also the only unit to have built-in external "knobs" for turning on and off the O2 and Diluent valves on the spheres.