tank neck orings

[HeatCker]

this has happened twice at the dive shop while getting my new faber hp100 tank filled...
during the filling process the oring in the neck of the tank blows/leaks and causes the tank and tank bank to partially drain or empty...
this has happened several times with tanks belonging to others..
the fills are done slowly, i think somewhere around 300 - 400 psi per minute, i will double check that...
what would cause the neck oring to blow...
one suggestion was that the tanks could have been very empty at the start of the fill, say 100-200 psi...
thanks guys...

 

[runsongas]

could be wrong duro or wrong size. i think some of the faber are not the common 014 size. or they could be trying to cheap out with a 70 or 75 duro NBR instead of a higher duro viton/epdm oring.

 

[JahJahwarrior]

Definitely switch to the 90 duro oring, don't lubricate it as it is static, confirm proper torque on valve, and you should be good to go.

 

[tbone1004]

fill speed shouldn't cause them to blow, nor would starting pressures.

Since you're saying it's happening to others, then I would tend to say that the dive shop has messed up the valves somehow. That is an exceptionally rare failure mode for tanks and if they are having repeat issues with it, then they need to look in the mirror and find out what they're doing to cause that. If they are using 90duro o-rings like they're supposed to, using metal o-ring picks to remove the neck o-rings could cause a gouge in the valve that could leak. I am not aware of any standard neck size tanks that don't use a 214 o-ring. I think @runsongas is thinking of the valve outlet o-rings where some valves do use some oddball sizes.

 

[shurite7]

Tank o-rings hold up quite well. There are some cheap ones, which may be the issue; even so, I have filled tanks with the lesser quality o-rings and never had an issue.

I’ve seen a few o-rings blow and it wasn’t because they were poor quality, rather it was because the o-rings were not changed when the tanks were VIP’d. Do you know if the o-rings were changed or were they re-used?

As mentioned above ensure the valve is tightened correctly. If the valve is not tightened enough it will not secure the o-ring in place.

 

[guruboy]

Also, don’t lube the oring.

can you clarify if they are failing/breaking or maybe extruding?

 

[HeatCker]

thanks all.
i'll pass this on and see if i can get more info, thanks again..

 

[iain/hsm]

Faber is of Italian manufacture and not the best of manufacturers.
The American importer is a box shipper and not an engineering company.

Not for the first time cylinders designed with counter sunk cylinder necks have found themselves being fitted with valves designed for counter bored valves (AKA Luxfer) by importers who frankly dont know the difference and dive shop who fit them knowing even less. And the O-ring used for each of these applications is a different size.

Agree with the earlier comments on O ring hardness this helps. But also consider the possibility that the machining of the neck is slightly off angle, this give a small gap between the piller valve and the cylinder neck on one side of the cylinder, worth taking a look as its a new cylinder this has happened many time before with the scuba importers of cheap deal imported cylinders.

When it happens to you underwater it will give you a firmer understanding of the problem.

Failing that when the cylinder 0-ring seal fails underwater most but not all the gas is released, the retaining few hundred psi isn't enough of drive pressure for the regulator to operate but more than enough to keep the sea water out of the cylinder on the body recovery. As far as the fatal accident coroner report is concerned, it's classed as a death by drowning the idiot diver having breathed all the gas out the tank.

Good quality 0 rings are cheap, you get to know the cure date, the material compound as well as the critical dimentions and the manufacturer. Junk from China is even cheaper. Knowing the difference is priceless.

By contrast most O rings you get from a dive shop are hydralic rejects you have no idea how old they are, or the compound or the manufacturer or how much carbon black (soot) was put in them to eaak out the maximum number of rings you can make out of some sweat shop in China to make your cheapskate importer and scuba shop a little richer.

Your call.

 

[tursiops]

Faber is of Italian manufacture and not the best of manufacturers.
The American importer is a box shipper and not an engineering company.

Not for the first time cylinders designed with counter sunk cylinder necks have found themselves being fitted with valves designed for counter bored valves (AKA Luxfer) by importers who frankly dont know the difference and dive shop who fit them knowing even less. And the O-ring used for each of these applications is a different size.

Agree with the earlier comments on O ring hardness this helps. But also consider the possibility that the machining of the neck is slightly off angle, this give a small gap between the piller valve and the cylinder neck on one side of the cylinder, worth taking a look as its a new cylinder this has happened many time before with the scuba importers of cheap deal imported cylinders.

When it happens to you underwater it will give you a firmer understanding of the problem.

Failing that when the cylinder 0-ring seal fails underwater most but not all the gas is released, the retaining few hundred psi isn't enough of drive pressure for the regulator to operate but more than enough to keep the sea water out of the cylinder on the body recovery. As far as the fatal accident coroner report is concerned, it's classed as a death by drowning the idiot diver having breathed all the gas out the tank.

Good quality 0 rings are cheap, you get to know the cure date, the material compound as well as the critical dimentions and the manufacturer.

By contrast most O rings you get from a dive shop are hydralic rejects you have no idea how old they are, or the compound or the manufacturer or how much carbon black (soot) was put in them to eaak out the maximum number of rings you can make out of some sweat shop in China to make your cheapskate importer and scuba shop a little richer.

Your call.

Wow, you must be a lot of fun on a dive boat. Do you have anything positive to say about anything?

 

[iain/hsm]

Wow, you must be a lot of fun on a dive boat. Do you have anything positive to say about anything?

I am, ask your wife.....she does. LOL