|This item "the triple rig"
was a design for DCBA or Damage Control Breathing Apparatus and was
not associated with diving. However my jpeg enclosed (under this article)
shows an earlier variant of DCBA modified for 55MSW diving and called the
SDDE or Surface Demand Diving Equipment, with the cylinders acting as air
This was an excellent design also using many of the parts in the
better known mixed gas/oxygen Clearance Divers Breathing Apparatus
There were only two small changes to convert from DCBA to SDDE namely an
aluminium back plate and a small adapter to connect a surface supplied
umbilical. No longer in service with Royal Navy but some overseas navies
still call spares.
At the time the Royal Navy already had a SCUBA variant called the SABA
set Swimmers Air Breathing Apparatus and the closed circuit oxygen and semi
closed 60/40, 40/60 32.5 mixed gas clearance divers set called the CDBA for
diving to 55 MSW both of these units worked well from the Gemini inflatable
boats. However the surface supplied SDDE was difficult to operate from the
Gemini due to having to have storage bottles, a diver panel, and two
Also at the time a deep water mixed gas semi closed variant was used for
secret operations called the Mark 4C. Designed primarily for SUBSMASH this
unit was used from 1975. Some aspects of the Mark 4 project may still be
classified, I will check on this but incidentally working at 100MSW semi
closed in cold 4 deg C water the maximum measured 02 uptake was
2.7 L/min at 63 MSW resulting in a P02 of 0.42 bar. The deep diving version
of this unit was rated to 350MSW.
Pics of DCBA / SDDE below if you need more info let me know.
Iain, thanks for contributing to my website!