burst disk

[HeatCker]

what is the normal life span of a burst disk?
i assumed that the disk was changed when the tank was hydro'd, every 5 years, i assumed wrong apparently.
thanks in advance.

 

[rhwestfall]

never assume....

at my last requalification, I requested the valve be rebuilt, and burst disc be replaced, or it wouldn't have happened...

I will do it myself at the same interval if time permits.

 

[tbone1004]

depends on the LDS, but most do not service the valve at hydro which IMO is a crime because of the markup they charge for doing nothing in the process. It makes me laugh that they stress the importance of annual service of a regulator, but then never service the valves....
It's also not just the burst disc, the o-rings inside should be replaced as well

 

[Johnoly]

..It's also not just the burst disc, the o-rings inside should be replaced as well

I agree. I rebuilt/replace my own valves. I do about 120 - 150 dives a year. Maybe I'm a little rough on my valves, but I can't get 5 years(hydro-time) out of a valve. I'm usually rebuilding/replacing a valve every 3-4 years . Lately the quality has dramatically improved on the DGX valves and the price point is cheaper than parts/time to rebuild a Thermo valve. I've been just doing swap & trash lately, it's quicker, cheaper, and works for me.

 

[JackD342]

Both Sherwood and Thermo specify rebuild at 5 years, including replacement of burst disc, seat, orings, etc. If 3 part burst disc instead of a single piece assembly, all parts are replaced.

Care to share more of your story?

 

[HeatCker]

thanks guys
i just recently started getting my worthington steel lp77 overfilled, to 3400 psi
shortly after that i had to service the thermo valve, an inside oring blew
the plastic valve on/off handle was lose, so while i've got your attention i might as well ask...
the valve on the tank is rated for 2400 service pressure
could the oring blow because of the increased pressure??
could the oring blow because of the loose handle/washer?? (has a fancy split screw head to tighten handle)
while it was being serviced i was talking to the tech about burst disks, and he mentioned he'd change the burst disk because it is not done during hydro....i just assumed out of ignorance that it was....seems like a logical thing to do

 

[JackD342]

Loose valve knob is just that - a loose knob. Unrelated to pressure, and a common occurrence.
Interior o-ring failure may was probably due to age and wear if service is being skipped, but likely also precipitated by the increased pressure.
Rating of a modern Thermo valve is based on the installed burst disc, and not the valve itself.

You cannot assume either way regarding the disc change at hydro, unless you ask. I know I do so religiously with hydro, but you will not have to search far on SB to find folks that characterize following the MFGR requirements as a pointless money grab. Perhaps your shop is in that camp, or perhaps is not even aware of Thermo’s service schedule. I know I did not realize it until a couple of years after I first started handling cylinder service.

 

[W W Meixner]

Loose valve knob is just that - a loose knob. Unrelated to pressure, and a common occurrence.
Interior o-ring failure may was probably due to age and wear if service is being skipped, but likely also precipitated by the increased pressure.
Rating of a modern Thermo valve is based on the installed burst disc, and not the valve itself.

You cannot assume either way regarding the disc change at hydro, unless you ask. I know I do so religiously with hydro, but you will not have to search far on SB to find folks that characterize following the MFGR requirements as a pointless money grab. Perhaps your shop is in that camp, or perhaps is not even aware of Thermo’s service schedule. I know I did not realize it until a couple of years after I first started handling cylinder service.

Hey Jack...

For 100% O2 cleaned cylinders...I O2 clean the valve at least annually along with the cylinder...completely dis-assemble...clean/dry/O2 compatible grease/new VITON ''O'' rings/new nylon bushing/new birst disc/inspection of seat nut and replace if necessary...

HeatCker is over-filling his 2400 PSI LP cylinder to 3400 PSI...not knowing the characteristics of the valve...but assuming it's not HP rated...I would only be servicing that valve with correct specification service components...including the burst disc...for 2400 PSI application...

For what HeatCker is doing he needs a 5250 PSI rated burst disc...as well as a valve compatible with 3442 PSI applications...not to mention a HP compatible cylinder...

What he's doing is not right...and the fill station attendant is way out of compliance if he/she is over-filling this cylinder/valve combination...to 3400PSI...nothing good can come from this...

Best...

Warren

 

[NAM001]

thanks guys
i just recently started getting my worthington steel lp77 overfilled, to 3400 psi
shortly after that i had to service the thermo valve, an inside oring blew
the plastic valve on/off handle was lose, so while i've got your attention i might as well ask...
the valve on the tank is rated for 2400 service pressure
could the oring blow because of the increased pressure??
could the oring blow because of the loose handle/washer?? (has a fancy split screw head to tighten handle)
while it was being serviced i was talking to the tech about burst disks, and he mentioned he'd change the burst disk because it is not done during hydro....i just assumed out of ignorance that it was....seems like a logical thing to do

i WOULD SAY THAT the tag that says 2400 service is moot. that same valve is for 3000 or 3300 etc. someone correct me if I am wrong. the tag that says 2400 means that the valve has been configured to provide proper protection for 2400 psi service rated tank. that protection is the burst disk. if you replace the disk with a 4600 psi disk then that tag should be changed to read 3000 psi service and is now a 3000 psi valve. The issue normally with a tank that is properly used is to verify the proper disk is installed in the valve that will provide the proper protection. ((((( i used 4600 on the premis that the disk should be able to hold 90% of TP). Lets not nit pick on the number. rather than the principle. On a 2400 lp 85 tank for example TP is say 5/3 o of working pressure or 4000 psi. the burst is designed to rupture before 4000 psi but still hold 3600 psi. I believe this is not a scuba thing but a fire code thing to protect fire fighters from being killed by metal fragments in the air form exploding tanks.

Likewise the rebuild kit for your valve isthe same for a 2400 as it is for a 3400 valve. The valve is rated for service up to XXXX psi or xxx bar. The o-rings etc are that same no matter what as they are good for the max rating for the valve . Only the burst disk is different.

 

[JackD342]

i WOULD SAY THAT the tag that says 2400 service is moot. that same valve is for 3000 or 3300 etc. someone correct me if I am wrong. the tag that says 2400 means that the valve has been configured to provide proper protection for 2400 psi service rated tank. that protection is the burst disk. if you replace the disk with a 4600 psi disk then that tag should be changed to read 3000 psi service and is now a 3000 psi valve. The issue normally with a tank that is properly used is to verify the proper disk is installed in the valve that will provide the proper protection. ((((( i used 4600 on the premis that the disk should be able to hold 90% of TP). Lets not nit pick on the number. rather than the principle. On a 2400 lp 85 tank for example TP is say 5/3 o of working pressure or 4000 psi. the burst is designed to rupture before 4000 psi but still hold 3600 psi. I believe this is not a scuba thing but a fire code thing to protect fire fighters from being killed by metal fragments in the air form exploding tanks.

Likewise the rebuild kit for your valve isthe same for a 2400 as it is for a 3400 valve. The valve is rated for service up to XXXX psi or xxx bar. The o-rings etc are that same no matter what as they are good for the max rating for the valve . Only the burst disk is different.

Exactly correct. Change the disk - change the sticker. That is the totality of the “configuration” on most/all modern valves.