Burst Disk Pressure

[1969ivan1]

Anybody out there know the standard pressure rating on a steel 72 burst disk?

[kgehring]

I think it is about 2750psi.

[pearldiver]

Ya, I think it is that. But word of caution. Look and see if the burst disc contains the old copper BB. You should change that kind, as if the disc bursts, the BB shoots out like a rocket. The new style is much safer. Beware though, the new burst discs don't fit in some of the old 1/2 inch valves.

[simonbeans]

I think Karl may have put in a different number than he thought. The working pressure of a bust disk is 40% or so over tank working pressure. For a 72 with a 2250 and a plus, the disks are rated at 3750, not 2750. I also agree that if you have one of the older burst disks, have them changed to one with an actual thin copper disk and a vented plug. If the the disk should rupture, the vented plug directs the escaping air to both sides of the valve instead of straight out. This is safer because the eacaping air won't cause the cylinder to spin.

[pearldiver]

I think the old BB style discs were lower than 3700. Not that it matters much, but if I recall correctly, they were around 3200 or so and held in place with a spring. I could be wrong.... Have that BB scream out of a plug and wonder how far it would travel through flesh before it stopped!!! Of course they were supposed to stay in the disc. I only had one burst, and the BB stayed where it was supposed to.

[kgehring]

It is 3750. Thats what I attempted to type. Must not have enough nitrogen in the system!

[pearldiver]

I missed decompression stops!! I think it is 3700.

[kgehring]

The disk reads 3750 right on it. Rob, do you need one?

[pearldiver]

I just looked at mine. It's a Healthways from 1956 and doesn't say that on it. In fact, nothing do I see but a BB staring at me.

[simonbeans]

What Karl and I were looking at are the new replacement burst disks. The older ones with the BB were not marked. I do not remember what their burst pressure was. Replace it if you can as you do have a nice little "pistol" if it ever blows.

[BROXTON CHUCK]

I checked several of my original steel 72's from the 1950's and they all have the original blow out plugs marked 3200 PSI. Even my 1953 RENE BROXTON tank has the old 3200 plug in it still. Since hydro is 5/3 the working pressure, this seems reasonable. I pump my tanks to 2500psi and have had no trouble. The older 70 cubic foot tanks, I pump to 2400 which is the standard 10% over fill. Chuck

[pearldiver]

The dive shop tried to install a new burst disc on my Healthways 1/2 inch valve to replace the BB one last year. It wouldn't work. For some reason it leaked air and looked huge compared to the original one so he re-installed the old one. I am not an equipment specialist to know what he was trying to do or why it leaked air. I'm bringing the tank to Wazee and maybe someone can shed some light on it for me....Maybe it's time to retire the tank?? The disc on that tank burst in about 1978 and was replaced with the same kind; one with a BB. The BB didn't shoot out of the old one unless there is a hole in the car somewhere and I didn't see it!! Sure would hate to retire the tank though, it was a present.

[BROXTON CHUCK]

All this paper worry about burst discs is hooey. If you dont abuse your gear, and dont overpump your tanks, your burst disc will never be needed. I still got the originals in all of my tanks, some over 50 years old, and there are no probs. Any compressor servicing a particular tank has a safety blow off to protect against overpressure. Its the duty nonetheless that the guy doing the filling, to watch whats going on, and not exceed the 10% overfill pressure.

[pearldiver]

That sounds like a good idea to me. Good thing I have answers here. The dive shop owner I used to go to has been deceased for about 15 years and knew all this stuff like you guys do. When I was 11, I took my regulator apart to see how it worked. It was cool. I rode my bike to the dive shop and brought my regulator in a paper bag all apart because I didn't know how it went back together. The guy was shocked. He made me promise I wouldn't repair my own gear or take it apart again. So I am way dumb on regulators and valves. I'll let you guys work on mine any day!

[BROXTON CHUCK]

Pearldiver: Bryan has a great idea where we can describe how we overhaul different regs, and any shortcuts, ideas we have that will help others troubleshoot their regs. Ill be doing one on the old broxtons and da's. Bryan will do the mistral types. Some other volounteers will help with the other regs Im sure. That way, even if you havent done it before, youll see how simple it really is. Hope this will help you. Chuck