There's a large number of dive cylinder valves out there, and getting the right one for your needs can be daunting. The Scuba Doctor dive shop has a large range to chose from and have we tried to make it easier for you with detailed info about each type of valve.
A Left valve is the typical/common/standard valve orientation used by recreational scuba divers using one cylinder. The valve opening and closing stem and hand-wheel are on the left side as you look at the valve outlet. It's also popular for use on side mount setups on the diver's left side, and for the OXYGEN cylinder on rebreathers.
A Right valve is the atypical/uncommon/non-standard valve orientation often used on the second cylinder of sidemount divers and twin cylinder technical divers. The valve opening and closing stem and hand-wheel are on the right side as you look at the valve outlet. It's popular for use on sidemount setups on the diver's right side, and opposite side stage bottles to keep the valves facing in the same direction, while keeping hand-wheels on opposite sides. It's also commonly used for the DILUENT cylinder on rebreathers.
Please Note: Be careful to properly specify whether you need a left or right valve by stating the orientation. Some manufacturers use the opposite names for their left and right valves, just to confuse everyone.
!!! IMPORTANT !!! Cylinders and valve threads come in a variety of sizes and great care must be taken to ensure that you are fitting the valve to the correct cylinder. The valve thread specification must exactly match the neck thread specification of the cylinder. Improperly matched neck threads can fail under pressure and can have fatal consequences if someone is hit by the flying valve or cylinder. Only qualified scuba servicing professionals should be installing this equipment. Please ensure you have the training and experience required before purchasing this item if you intend to fit it yourself. If you are unsure, please call your local scuba technician to provide appropriate information for your system.
Australian Standard Diving Cylinder Valve Thread
Most Australian Standard aluminium and steel tanks/cylinders/bottles use a standard 3/4-inch NPSM (NGS) parallel thread, sealed by an O-ring, which has a 60° thread form, a pitch diameter of 0.9820 to 0.9873 in (24.94 to 25.08 mm), and a pitch of 14 threads per inch (5.5 threads per cm). It is torqued to 40 to 50 N·m (30 to 37 lbf·ft) on aluminium cylinders.
European Diving Cylinder Valve Threads
On most steel and aluminium diving cylinders in Europe the M25X2 ISO parallel thread, which is sealed by an O-ring and torqued to 100 to 130 N·m (74 to 96 lbf·ft) on steel, and 95 to 130 N·m (70 to 96 lbf·ft) on aluminium cylinders, is now commonly used. (M25 means the diameter of the thread is 25 mm and the X2 defines the 2 mm pitch of the thread.) On smaller cylinders where the neck isn't large enough for the M25X2 thread a M18x1.5 parallel thread, which is sealed by an O-ring, and torqued to 100 to 130 N·m (74 to 96 lbf·ft) on steel cylinders, and 85 to 100 N·m (63 to 74 lbf·ft) on aluminium cylinders is used.
Please Note: The M25X2 metric thread valves are only for use with metric M25X2 threaded cylinders. While they can be wound into a cylinder/tank with a 3/4 inch NPSM threaded neck, they will not seal properly and the combination can be very dangerous. Do not try and use these M25X2 valves on typical Faber, Catalina, Luxfer etc. cylinders purchased in Australia.
When someone tries to fit a M25 valve into a 3/4-inch BSP cylinder thread, they will get it to seal, but only after damaging the brass threads on the valve. This produces an unstable fitting which can result in the valve coming out with an incredible force that could seriously injure someone, or even kill. You have been warned.
All parallel thread valves are sealed using an O-ring at top of the neck thread which seals in a chamfer or step in the cylinder neck and against the flange of the valve.
There are two basic types of cylinder valve to regulator connection in general use for Scuba cylinders containing air:
In Europe there is now a standard for cylinder valves for scuba cylinders containing gases other than air:
Most of the 200 to 240 bar valves supplied in Australia are a DIN/K convertible valve. They are made with a DIN regulator connection, but such that a DIN plug adaptor can be screwed into the DIN outlet so that an A-clamp or Yoke regulator can be connected to the valve.
Yoke valves are rated between 200 and 240 bar, and there does not appear to be any mechanical design detail preventing connection between any yoke fittings, though some older yoke clamps will not fit over the popular 232/240 bar combination DIN/yoke cylinder valve as the yoke is too narrow.
DIN valves are produced in 200 bar and 300 bar pressure ratings. The number of threads and the detail configuration of the connections are designed to prevent incompatible combinations of filler attachment or regulator attachment with the cylinder valve.
Adaptors are available to allow connection of yoke regulators to DIN cylinder valves. These plug adaptors (or inserts) are rated for 200-240 bar, and can only be used with valves which are designed to accept them.
Australian standards require that the cylinder valve includes a bursting disk, a pressure relief device that will release the gas before the cylinder fails in the event of over pressurisation. If a bursting disk ruptures during a dive the entire contents of the cylinder will be lost in a very short time. The risk of this happening to a correctly rated disc, in good condition, on a correctly filled cylinder is very low.
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Chaordent Pty Ltd trading as The Scuba Doctor Australia ("The Scuba Doctor"), ABN 88 116 755 170, is bound by the National Privacy Principles ("NPPs") under the Privacy Act 1988 (Cth) ("Privacy Act") in the way that it handles personal information. This policy explains how The Scuba Doctor handles personal information relating to individuals, whether or not they are customers.
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Contact Details
Privacy Officer
The Scuba Doctor Australia
Boon Wurrung Country
1/49 Peninsula Ave
RYE VIC 3941
AUSTRALIA
tel. 03 5985 1700
email. diveshop@scubadoctor.com.au
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