burst disk

[W W Meixner]

KWS/Jack...

Not correct...first we have no idea of the characteristics/generation of the valve in question...further...most valves in use in North America are stamped/forged with identified service pressure...both in BAR and PSI...these identified service pressures should not be exceded...the wall thickness of the valve bodies are not all the same...

Finally ...''all'' valve service kits are not the same...

A 3442 service pressure cylinder...paired with the correct service pressure valve/burst disc assembly is the only option...

I see no point in enabling a novice to do the wrong thing...this isn't DIY...nor is it re-purposing something that can be used in a safe manner...it's wrong...and it's not safe...

DIR...

W...

 

[HeatCker]

thanks guys for your input
i just looked ... the "Thermo" valve on the tank is stamped for 230 bar (230 * 14.5 = 3335 psi)
the new burst disc is rated for 4000 psi for 2400 psi service pressure
so i should back off on the overfills
or replace the valve and burst disk with one of higher rating which is probably what they do in cave country

 

[happy-diver]

I figured that in order to prevent burst disc issues I put two discs per valve
and as European valves have no facility for burst discs, well go figure that!

 

[JackD342]

KWS/Jack...

Not correct...first we have no idea of the characteristics/generation of the valve in question...further...most valves in use in North America are stamped/forged with identified service pressure...both in BAR and PSI...these identified service pressures should not be exceded...the wall thickness of the valve bodies are not all the same...

Finally ...''all'' valve service kits are not the same...

A 3442 service pressure cylinder...paired with the correct service pressure valve/burst disc assembly is the only option...

I see no point in enabling a novice to do the wrong thing...this isn't DIY...nor is it re-purposing something that can be used in a safe manner...it's wrong...and it's not safe...

DIR...

W...

Warren-
I think you already know from numerous previous posts that I am firmly on the side of doing things "by the book," using OEM parts, correctly matching disk to service pressure, and following manufacturer's guidelines. This OP has a valve already and is asking for guidance on what next steps to have done with/through his LDS. I purposely did not go down the rabbit hole of the "over fill" of his tanks and mismatching burst disks to enable that practice. He needs to understand how and why his current valve is "rated 2400 PSI." That rating is based on the burst disk, although the sticker/label might easily be inaccurate if not kept up to date when changing disks.

I think you are both a little mistaken, and a little bit not reading what I wrote closely enough.

• I specifically qualified my guidance as applying to "modern" valves, based on my knowledge of Thermo, XS Scuba, and Sherwood. I can't speak to any additional limitations on earlier generations with any specific knowledge, and so passed on that. I do assume that Blue Steel and other valves in the North American market are similar.
• I just looked at a current Sherwood valve - only pressure marking is the replaceable sticker. On a current Thermo yoke valve, there is a "230 BAR" maximum etched on the valve body, plus the label based on the burst disk. I am confident that you will see that same 230 BAR etching on ALL Thermo and XS Scuba yoke valves regardless of which burst disc is installed. I am pretty sure that is driven by a US DOT pressure limit for ANY yoke valve. Nothing to do with the wall thickness of the valve body - XS/Thermo is not making any more components than necessary. (In this example, yoke also applies to their convertible "PRO" valves.)
• Again based on XS/Thermo, they do make some DIN only valves that are rated for 300 BAR. These cannot be used with a yoke regulator, even with a DIN insert, as the dedicated 300 BAR versions have the deeper threaded opening.
• No one said "all service kits are the same." But they do NOT vary by service pressure - the burst disk (whether a single piece assembly or a 3 piece set) is a separate purchase and are not included in a valve service kit. Sherwood makes ONE service kit that covers most of their production for both current valves and decades of past output. (Two if you count the nitrox version, if still available). XS/Thermo makes 6 kits, 1 each of K, PRO, & DIN for each of their two brands. There are slight differences between the components for each brand, so the 6 kits actually are unique and not just "badge engineered."

So the bottom line for this OP is that he does NOT necessarily need to buy a new valve if using it on a cylinder with a different service pressure - almost for sure just changing the disk will do. Filling a 2400 rated tank to 3400? That is a totally different can of worms.

 

[JackD342]

thanks guys for your input
i just looked ... the "Thermo" valve on the tank is stamped for 230 bar (230 * 14.5 = 3335 psi)
the new burst disc is rated for 4000 psi for 2400 psi service pressure
so i should back off on the overfills
or replace the valve and burst disk with one of higher rating which is probably what they do in cave country

Without knowing more about your tank, that disk probably is the correct match for your cylinder. And no argument from me regarding backing off on the overfills.

 

[abnfrog]

exactly right on with your answer jack .....as an IT that teaches o2 cleaning and vip inspection at my 5 star sdi/tdi facility , you are right , the modern valve will take those pressures no problem and is stickered for the burst disc ......

 

[HeatCker]

thanks again for taking the time to respond.
the tank i am overfilling is an xs scuba worthington 3AA steel lp77.
born sept 2007, vis'd every year, hydro'd every 5 yrs, and carefully taken care of.
i am under the impression, from reading many posts here on scuba board, that lp 3AA steel tanks are way over designed and are used/overfilled daily in cave country (3600 psi) and still pass visual and hydro inspect after many years of overfilling use.
i don't want to open a "can of worms" on what is right and what is wrong, that's already been hashed out in many threads, there are obviously two camps on this issue....what i would like confirmed is "are 3AA steel LP tanks safely and successfully used as i have described in cave diving"

 

[W W Meixner]

thanks again for taking the time to respond.
the tank i am overfilling is an xs scuba worthington 3AA steel lp77.
born sept 2007, vis'd every year, hydro'd every 5 yrs, and carefully taken care of.
i am under the impression, from reading many posts here on scuba board, that lp 3AA steel tanks are way over designed and are used/overfilled daily in cave country (3600 psi) and still pass visual and hydro inspect after many years of overfilling use.
i don't want to open a "can of worms" on what is right and what is wrong, that's already been hashed out in many threads, there are obviously two camps on this issue....what i would like confirmed is "are 3AA steel LP tanks safely and successfully used as i have described in cave diving"

HCK...

What is the stamped/engraved/etched working pressure on your valve...post a few pictures if you can...

So far...and if I've missed something I apologize...but no information has been posted on your valve...the cylinder is twelve years old...and if the valve is a common small head yoke only valve...I certainly would not be putting it under 3400 pounds of pressure...working pressure identification is there for a purpose...

Valves are not expensive...further...my verdict on overfilling any cylinders has been in for a long time...

What cave divers do regarding over-pressurizing cylinders is often referred to by them as a ''dry-hydro''...based on an article from Europe...relating to the fact that steel cylinders can be re-hydro'd 10,000 times in their service life...Although I've seen this article referenced numerous times...I've never seen the actual article...or the science behind it...and I'm not ready to believe it...when the existence of this article became known to European cylinder manufacturers such as Faber...they started stamping...''DO NOT OVER PRESSURIZE''...on their cylinders...they were particularly concerned with their low pressure cylinders...and all cylinders for the North American market...

Remember...there's ''manufacturer authorized''...then there's everything else...eg: DIY/re-purposed use/over-pressurizing cylinders...to name a few...

DIR...

W...

 

[NAM001]

KWS/Jack...

Not correct...first we have no idea of the characteristics/generation of the valve in question...further...most valves in use in North America are stamped/forged with identified service pressure...both in BAR and PSI...these identified service pressures should not be exceded...the wall thickness of the valve bodies are not all the same...

Finally ...''all'' valve service kits are not the same...

A 3442 service pressure cylinder...paired with the correct service pressure valve/burst disc assembly is the only option...

I see no point in enabling a novice to do the wrong thing...this isn't DIY...nor is it re-purposing something that can be used in a safe manner...it's wrong...and it's not safe...

DIR...

W...

I think we are saying the same. parts are the same OTHER THAN the burst disk. If you go and buy a valve you buy one of a style and you say what disk you want in it. The valve body of a 2400 valve is the same as a 3000 valve. Only the installed burst disk is different. As far as being stamped with a service marking ..... NOt a one of my valves are marked with a working pressure. If you buy a burst disk it comes with a sticker ( from some suppliers) with the associated working pressure for that disk. Any valves I have bought was marked with a removable sticker on it so you can change burst disks if used on a different tank. I have also bought tank valve rebuild kits and none of them have pressure ratings unless they have the burst disk in the kit. I saw last week a molded marking of working pressure on a very very old valve. I have not seen any permanent pressure marking on any new valves. I have been undrer the4 understanding that a low pressure valve is a low pressure valve. Is not a 3442 valve in the low pressure valve catagory? Or is the upper limit 3300. I dont know because i dont use so called HP tanks . all of mine are lp tanks. If 3442 is a hp tank then it would use a different designed valve. The valve for a 3000 and a 2400 ( as far as I know) is the same valve with different burst disks in them. As high and low pressure tanks and valves go Wasnt there a problem with the 3500 psi tanks as far as whether they were HP or LP tanks years ago and they changed the tank to a 3442 to avoid the question of tank catagory? I would also highly suspect that if there was a special HP valve needed that the tank would be threaded differently to prevent the lower pressure valve from being put in. I would reddily concede that a 3442 valve is not the same if it had a different thread on it. Again I dont use HP tanks and that 2400 tanks use the exact same valve that a 3000 tank does, ignoring the installed burst disk being the difference.

Additional info I use DIN valves. if it is a hi pressure din you can not put in a adaptor (screw in) and it is called a 300 bar din max 300 bar use. but the ones with a screw in adaptor is called a 200 bar din. I again am assuming that the 200 bar means nothing but to sy LP valve which again I have to ask where is the line between LP and HP.

 

[NAM001]

thanks guys for your input
i just looked ... the "Thermo" valve on the tank is stamped for 230 bar (230 * 14.5 = 3335 psi)
the new burst disc is rated for 4000 psi for 2400 psi service pressure
so i should back off on the overfills
or replace the valve and burst disk with one of higher rating which is probably what they do in cave country

My interpretation of that is that if it is a yoke valve it is a lLP valve. that 230 is teh max rated usage for the valve design. My burst valves for a 2400 tank blows ar about 36-3700 psi. so i am going to assume that the burst disk is for a tank with a 4000 psi Test Pressure which would be 3600-4000 psi. Over filing is alwyas a hot topic for many and of no concern for many others. To be honest if you know you ahve a min 3600 burst threthhold adn since there is no scuba police ac accordingly. keep in mind that pressrue goes up when the tank is sun heated and that when you get a 2400 fill it could be 2600 id the tank fillers gage is not correct. I have filled a LP tank to 3300 and the gage ws 200 off so unknowing ly it was really filled to 3500. the sun hit it and the burst blew. 20 degrees temp rise is 100 psi apx. You do the math. Yes replacement is what they do in cave country. a burst disk for a 3000 psi valve is about 4500 psi. I have also seen those tanks hit 4450 int he sun. To be honest I dont know why anyone would want to push a tank that much. Many do and leave the tank in the water where the sun will not heat it much. the water if 80f will keep the tamp down. Every one has their work around safety items. One must use some common sense when they push limits.