Tank Valve Blows O-rings

[cbmech2]

As in the other posts, I am unsure which o-ring you are referring to. Are you referring to the valve o-ring itself? Over time the sealing surface on the tank can get corroded and become non-concentric with the valve (flat). This can be resurfaced using the correct tool. If it is the valve to regulator o-ring, then Matt is correct that the hardness should be a 90 at least. I would also check the surface of the regulator mating surface. It too can get dinged up and cause sealing problems. Should be able to flatten it out with some fine grit sandpaper. The only problem there is that you will of course remove the chrome plating. Hope this helps and good luck to you.

 

[Couv]

edit....good info above by cbmech, he was faster on the draw than me, so forgive the redundancy....c

Al,

OK, now that we know it is a yoke valve, go back and read tfsails' post-especially the overfilling caution. A bit of overfilling is usually not going to cause problems, but 500 psi over could be a bit much. First, have a good look (meaning if you have old eyes like me, use good light and a 10 power magnifying glass) at the o-ring groove. Nice and round? Good. No dings or chips? Good. Compare the small divot where the yoke screw fits into to your other valve. Do they look exactly the same as far as placement and depth? Now the o-ring. Most valve faces take a -014, but as others have pointed out, it might be a slightly different size. Try a 90 duro or as Matt suggested a 90 duro polyurethane (he is rich and can afford those) if still having problems.

Now there is one more thing that I do not believe has been mentioned. The yoke on your regulator could be stretching due to the excess pressure, but because you said this does not happen with your other tank, most others here probably discounted that; but, again, see tfsails warning.

Good luck and keep us posted on your findings.

Couv

 

[alrazi]

Guys I really appreciate all your replies, the O-rings are the correct type but apparently the extra pressure is the main cause. Now the tank was left open with 210 bars and nothing happened yet.
I think I've made a mistake allowing the dive operator to compress the tank to 245 bars. I definitely will not risk it again. .this could've happened 25mtr below surface. . . and my advice to all .. compress your tanks to the limit but do not exceed the maximum allowable, The manufacturers know the capabilities of their equipment, so stick to the design spec.

 

[halocline]

It's unlikely that the valve o-ring would hold at the surface and then extrude at depth. Because ambient pressure at depth is greater, there is less of a pressure gradient across that o-ring when the tank is at depth. It certainly does happen occasionally, but it's far more likely that the o-ring will fail immediately if there's a problem with the valve/reg seal.

One thing you're forgetting; your tank was filled using a yoke fill whip that seals exactly the same way as your regulator, against the same o-ring. If the problem was solely that the valve o-ring could not handle the pressure, it would have failed during filling. There's something in the way your reg fits that is causing it to fail under that higher pressure.

Remember that the problem in your case was the valve/reg interface and had nothing to do with exceeding the service pressure of your tank. You could put a DIN valve on this same tank and you would have no indication of any problem.