Burst Disks - periodic replacement?

[Rick Inman]

My LDS has a policy that burst disks get changed during your Viz. Period.

Force me to change them at every vis???

Pass.

How do they know when I last changed them myself? Or that maybe I've only fill the tank once, and it sat for a year at 50 PSI. Their shop policy of mandatory change every year is bogus, IMHO.

 

[DA Aquamaster]

Changing a burst disc annually is serious overkill. And to make you spend $10 to replace a burst disc as part of a $5 to $10 VIP strikes me as just finding another way treat divers as a revenue source. I can see the shop mandating they be changed when the tank comes back from a hydro test, but any more than that is too much.

In my experience, burst discs letting go are more or less a non event. The older lead slugged burst disc could be somewhat dangerous as the lead slug was ejected form the valve much like a small bullet. However the copper discs used in the last 30 years do not eject much of anything and anything that might be ejected impacts the end of the nut as the gas has to make a 90 degree turn top exit out the vent holes.

The vent holes also direct the gas in multiple directions and the orifice itself is fairly small so no huge amount of thrust is generated. A tank with a ruptured disc mostly just sits there and makes lots of noise.

 

[do it easy]

Changing a burst disc annually is serious overkill.

Do you think it is excessive when O2 cleaning a valve or just for air tanks?

 

[akscubainst]

It's my understanding that DOT requires that the burst disk be changed at the time of Hydro.

DM

 

[divinginn]

i just had one let go in my truck after sitting in the sun all day,glad i had the windows cracked open,that tank had a serious overfill on 3600 lbs on a steel 72,i bleed off about 100 lbs,should have bleed off about 500 lbs,not sure if that tank will pass its next hydro,but i like the bottom time of a 72 with 3000 lbs in it.

 

[mheaster]

OK, many of you confirmed that a REQUEST to have them changed is reasonable.

I was always aware that the cost of hem was an expense that would be passed on to me.

It is little stuff like this that makes me want to walk away to a different shop but I am limited. Of course I have no really local LDS so I may be looking into new one for maintenance . . .

 

[DA Aquamaster]

i just had one let go in my truck after sitting in the sun all day,glad i had the windows cracked open,that tank had a serious overfill on 3600 lbs on a steel 72,i bleed off about 100 lbs,should have bleed off about 500 lbs,not sure if that tank will pass its next hydro,but i like the bottom time of a 72 with 3000 lbs in it.

The test pressure on a steel 72 with it's 2250 psi service pressure is 3750 psi, so it's no surprise that a steel 72 filled to 3600 psi, bled to 3500 psi and then left in a hot car blew a burst disk - that is what is supposed to happen.

Personally, filling a Steel 72 to 3000 psi on a regular basis strikes me as being less than prudent. And you are only getting 86 cu ft of air at 3000 psi. 3500 psi would give you 100 cu ft, but is essentially subjecting the tank to a continuous hydro test without the safety that comes from doing it with water pressure rather than air - that qualifies as being really stupid.

Just get an E7-100 and get 100 cu feet legitimately at the normal pressure of 3442 psi with no safety concerns, no blown burst discs, a normal tank life, and no more weight or bulk than a AL80.

It's my understanding that DOT requires that the burst disk be changed at the time of Hydro.

DM

There is no requirement to change them on tanks not carrying hazardous materials, just a requirement that one with a suitable pressure range be installed in the valve before the tank is returned to service.

It is however good practice to change them then, as the old burst disc has probably seen enough age, corrosion, use and cycles, to warrant replacement.

 

[Wayward Son]

I have my valves serviced at every hyrdro. Presumably George replaces the burst disk while he has it apart, but I'll have to ask to be sure. They also get serviced if they need it at any other time & i know of a few times when I had one in for VIP & got it back with O rings & burst disks replaced. 2 were done that way this year, but he doesn't arbitrarily replace them at VIP time. Only if there's a reason.