Air Venturi tanks, word of caution

[Willie14228]

Okay so let me say this first, I don't know if the issue came about because of the guy that refilled the tank may have loosened the valve of if it was an actual o-ring failure what ever the case 4500 psi spewing out in the seat beside you will make you do some emergency braking and after all is said and done emergency shopping for clean underwear 

Today I took my tank to the same person I always have, these tanks have a slow fill valve that has to be removed to fill the tank or it takes forever to fill as such it is possible while removing that restrictor valve from the main valve he loosened the main valve from the tank. 

He filled the tank reinstalled the restrictor valve and I paid and left, I didn't get 10 miles from the dive shop when the oring popped, and let me say that 4500 psi of air escaping is a very loud and scary event. my first thought was that the burst disk had ruptured but that was not the case, after all was said and done I unscrewed the main valve and discovered that the o-ring does not sit in any type of keeper groove. It just rides flat on the seat of the valve and tank the only thing that holds it in place is the tightness of the valve to the tank. 

From now on when I pick the tank up I am going to check to make sure the valve is nice and tight

 

[Flintstone]

One of these days somebody is going to get hurt. Cheap compressors and air cylinders long without hydro testing are an accident waiting to happen. I surely do hope I am wrong. Just sayin'.

 

[Alan_B]

As I understand it the 4500 psi holds the valve in place very tightly, the only time it can be loosened is when the pressure is released to zero which should not be happening very often. Then it does need to be tightened before filling. The technician doing the filling should do this as part of his pre-fill inspection. Tanks brought in with zero pressure get extra scrutiny, they should not be at zero unless new or post hydro testing.

I have restricted flow valves on both my tanks (AV and Brancato), and my understanding is that the restriction is one-way so it has no effect in the filling direction. It is internal to the valve and so could not readily be removed anyway. There is a Din300 to Foster adapter on my tanks (or Din300 to hose) but those are not flow restricted items and can be filled through.

Sounds like a different setup there. How does it work?

 

[Hepotter]

O-rings, both old and new, even flattened between a valve and a tank, can still fail...

Unless the technician took the fill valve off of an empty tank, and then re-tightened it, there's no way any human could have turned that fill valve with air in the tank.

Even with just 500 psi in the tank, that correlates to 500 pounds of pressure on the fill valve threads and no human is going to turn that without a very large tool.

I've seen it happen in 40 feet of water during one of my scuba classes...sometimes they just blow out! Age is usually a factor, but not always. All kinds of seals are prone to failure over time.



Regards,

Uncle Hoot