Instructor Manual
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Ocean Diver
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Adapting to the underwater world
Copyright © BSAC 2017
14
Pillar/cross-flow valves
A-clamp
The A-clamp or international fitting cylinder valve has an
O-ring set into the valve outlet and the regulator clamps
around it. Sometimes this is referred to as a yoke fitting.
• 232 bar cylinders (max)
The A-clamp type of cylinder valve can only be used on cylinders with a working
pressure up to 232 bar.
DIN
The DIN cylinder valve has an internal 5/8-inch BSP thread and no sealing O-ring
as this is on the diving regulator instead.
• 232 -300 bar cylinders
DIN valves can be fitted on cylinders up to 300 bar. A 232 bar DIN cylinder
valve has five thread rotations within the valve whereas a 300 bar DIN valve
has seven thread rotations. This means that it is not possible to attach 232-bar-
rated equipment to a 300 bar cylinder supply. It is possible to screw an A-clamp
insert into some 232 bar DIN valves to convert them to allow use of regulators
equipped with A-clamp fittings.
M26
• Nitrox cylinders
In 2008, an EU directive came into force requiring an M26 fitting to be used on
equipment where the gas being used has an oxygen content above 22 per cent.
This fitting appears similar to a DIN fitting but is a 26mm fitting rather than a
5/8”. However, this valve type has not been generally adopted in the UK.
Buoyancy compensator
Supports the cylinder
The buoyancy compensator or BC carries the cylinder. It
is a jacket or harness system. They are manufactured in
various styles but have many important common features.
