Originally Posted by para
The screw in yolks tend to have the pressure gauge on the cylinder and so aren't used for diving as far as I'm aware, this is info I got from the dive shop that if the cylinder can be used for diving then it is tested as such.
I have a Din fitting which has the pressure gauge attached to the cylinder, if I remember correctly the A Frame cylinders have pressure gauges attached to the hose so the cylinder and can still be attached to a divers regulator.
Although I'm no expert!!!
I have diving regulators with both 'A' frame and Din fitting (screw in type) neither of which have gauges on.
I think what you meant are the cylinders that come with the gauge as part of the actual valve body these too are available as 'A' frame and Din . Thus the gauge is part of the bottle and not the whip assembly and as such are deemed surface use only and the test period is 5 years for it to have it's hydrostatic test. Cylinders that can be used underwater will be 2 1/2 years for a visual then a hydrostatic test at 5 years.
What you could say is that if your filling whip has a gauge on it then the cylinder it fits can be used for diving if the whip has NO gauge on it then the cylinder it fits is a surface use only one.
The Hydrotech website is good to see the cylinders.
Hope that this clarifies it.