Valve Pressure Rating Vs. Tank Pressure Rating

[MAK52580]

I recently bought a 300 Bar Thermo Valve for my 40 cu. ft. bottle. The Luxfer cylinder has a 3,000 psi rating and the valve has a 3180 rating.

Since this tank will never have a high pressure in it anyways since it will contain higher partial pressures of oxygen, is it still kosher to use this valve on the tank? Or do i have to switch out the burst disk to a 3,000 disk?

My gut would tell me that as long as the burst disk rating is not below that of the cylinder rating then I should be fine considering it will hardly ever be subject to 3,000 psi.

Any opinions?

Thanks.

 

[jdh]

I recently bought a 300 Bar Thermo Valve for my 40 cu. ft. bottle. The Luxfer cylinder has a 3,000 psi rating and the valve has a 3180 rating.

Since this tank will never have a high pressure in it anyways since it will contain higher partial pressures of oxygen, is it still kosher to use this valve on the tank? Or do i have to switch out the burst disk to a 3,000 disk?

My gut would tell me that as long as the burst disk rating is not below that of the cylinder rating then I should be fine considering it will hardly ever be subject to 3,000 psi

Any opinions?

Thanks.

I like the Thermo convertible DIN/Yoke valves, like the ones that come with PSt 130's. I have them on all my 40's. Anyway, 300 BAR is 4351 psi. Are you saying the valve has a 3,180 psi burst disc in it? I certainly wouldn't change out discs if they were rated 180psi higher than the tank. Sometimes I put 3010 psi in my 40's!

John

 

[jonnythan]

It's no problem. People use 300 bar (4350 psi) DIN valves on low pressure (2640) tanks all the time, because of the secure connection.

 

[Leadking]

I recently bought a 300 Bar Thermo Valve for my 40 cu. ft. bottle. The Luxfer cylinder has a 3,000 psi rating and the valve has a 3180 rating.

Since this tank will never have a high pressure in it anyways since it will contain higher partial pressures of oxygen, is it still kosher to use this valve on the tank? Or do i have to switch out the burst disk to a 3,000 disk?

My gut would tell me that as long as the burst disk rating is not below that of the cylinder rating then I should be fine considering it will hardly ever be subject to 3,000 psi.

Any opinions?

Thanks.

Change the burst disc. It is not a 180 psi difference-it is a 250 lb difference. Burst discs are a function of hydro pressure, not operating pressure. The busrt disc for a 3180 + rated tank is 5250 psi (3180+318=3498x1.5 hydro=5247 psi).

 

[LobstaMan]

I understand that, but still wouldn't that leave you with some extra psi on the burst disc? On a 3000 psi AL tank, the test hydro pressure is 4500 psi, so the disc would still have 750 psi remaining. Or, I am missing the point of the burst disc, i.e. it needs to match the hydro amt on the tank it's affixed to. Thanks...I'm still learning.

LobstaMan

 

[DA Aquamaster]

A DOT 3AL tank has a hydro test pressure of 5/3rds the service pressure, so for a 3000 psi tank, the test pressure is 5000 psi.

Per DOT requirements, a burst disc is required to fail in a range of 90% to 100% of the hydro test presssure of the tank. So for a 3000 psi tank it would be expected to fail between 4500 and 5000 psi.

If the burst disc is designed for a tank with a 3180 psi service pressure, it would be expected to fail at 4770 to 5300 psi.

I'd have no reservations about using a 3000 psi rated valve in a 3180 psi tank, but not vice versa. Having a bust disc let go at 4500 psi rather than 4700 psi is not going to make any practical difference, but not having the disc fail until 5300 psi rather than at 5000 psi could make a serious difference if the extra 300 psi is enough to cause the tank to fail catastophically. The odds of something bad happening are very remote, but the potential cost of it happening once are not worth the $7.00 cost of replacing it with the correct assembly.

In the real world. using a valve/disc assembly that is rated for a slightly lower pressure is not a problem as there is still ample margin between the service pressure and the pressure where the burst disc will fail. Theoretically you could use a burst disc designed for a 2250 psi tank in a 3000 as it will not fail until the pressure reaches 3375 to 3750 psi. at least when it is new. But in practice this would be a very bad idea as discs get weaker as they age and experience fill cycles, and you would pretty quickly have a disc failure which would result in a loss of air which of course creates another safety problem if it occurs during a dive.

 

[LobstaMan]

So, it's okay to use a valve with a lower service pressure than the tank, but not vice versa. I'm looking at putting new Thermo Pro DIN/Yoke valves on steel 72s to replace the original J valves on there now. I should use a valve specifically rated for 2250pis then, correct?(That is if they make them for that pressure.)

LobstaMan

 

[MAK52580]

So, it's okay to use a valve with a lower service pressure than the tank, but not vice versa. I'm looking at putting new Thermo Pro DIN/Yoke valves on steel 72s to replace the original J valves on there now. I should use a valve specifically rated for 2250pis then, correct?(That is if they make them for that pressure.)

LobstaMan

LobstaMan,

I have 2 DIN/Yoke adaptable valves for the higher pressure E8-130s. I doubled them up and have no use for the valves on there now. If you are willing to change out the burst discs, they could be yours if you like. Otherwise I was just going to eBay them. PM me if interested.

Marc

 

[Leadking]

I understand that, but still wouldn't that leave you with some extra psi on the burst disc? On a 3000 psi AL tank, the test hydro pressure is 4500 psi, so the disc would still have 750 psi remaining. Or, I am missing the point of the burst disc, i.e. it needs to match the hydro amt on the tank it's affixed to. Thanks...I'm still learning.

LobstaMan

Aluminium tanks are hydro'd at 5/3 working pressure so a 3000 psi tank would be
3000x1.666=5000 psi. The hydo for different manufacturer's and material composition can change the hydro spec's. DOT 3AL for aluminium and 3AA for steel are "standard"
but cylinders that have an "E-XXXX" designation are "exempt" cylinders that do not meet the standard and may require different hydo requirements.

 

[StSomewhere]

It's no problem. People use 300 bar (4350 psi) DIN valves on low pressure (2640) tanks all the time, because of the secure connection.

Huh, I was told that was done to facilitate overfills.