New Lp 108 Disk Burst 1st Over Fill 3800 Psi?

[DrifterEd]

Hi...THIS MY FIRST TIME ON SCUBA BOARD.QUESTION? I JUST BOUGHT 3 LP 108 AND HAD THE FILLED FOR THE FIRST TIME. SHOP OVER FILLED HOT 3800 COOL 3500. ONE TANK BURST DISK AT 3800? CAN I REPLACE BURST DISK TO ONE WITH A HIGHER RATING. ANY COMMENTS APPRECIATED.THANKS...

 

[DA Aquamaster]

You can replace it with one with a higher rating, but not legally or intelligently. The burst disc is there for a reason.

Assuming your tank has a service pressure of 2400 psi, a 10% overfill to 2640 psi is allowed as long as the tank is "+" rated and will have no ill effect on you or your tank.

Hot filling a 2400 psi tank to 3800 psi is incredibly stupid and is only 200 psi short of a hydro test. While the tank is designed to withstand a hydro test pressure, it is designed to do so for only a very short period of time. A hydro test is also done with water so that if the tank fails no explosion ensues.

A 3500 psi pressure maintained in a 2400 psi tank for an extended period of time will drastically reduce its life with the result that it will in relatively short order either fail a hydro or in a worst case situation fail catastrophically.

If you need more air, buy bigger tanks.

 

[LUBOLD8431]

A 3500 psi pressure maintained in a 2400 psi tank for an extended period of time will drastically reduce its life with the result that it will in relatively short order either fail a hydro or in a worst case situation fail catastrophically.

If you need more air, buy bigger tanks.

Actually, these tanks can handle 3500 psi. Change the burst disk, and you'll be all set. They are used in Europe, and filled to 3500 over there. Just different specs in the USA to make DOT happy.

 

[FredT]

CAN I REPLACE BURST DISK TO ONE WITH A HIGHER RATING.

By current USA DOT rules the burst disk rating has to be at hydro test pressure with a MINUS 10% tolerance.

In the US a "normal" 2400 psi tank hydros at 5/3s pressure, or 4000 psi unless otherwise marked in the tank roll mark. Given a "standard test pressure the burst disk should fail at between 3600 psi and 4000 psi. If the tank has a different test pressure in the roll mark that is the upper end of the burst disk range.

The "proper" response is to spank the fill station operator for overfilling.

FT

 

[OneBrightGator]

Hot filling a 2400 psi tank to 3800 psi is incredibly stupid and is only 200 psi short of a hydro test. While the tank is designed to withstand a hydro test pressure, it is designed to do so for only a very short period of time. A hydro test is also done with water so that if the tank fails no explosion ensues.

A 3500 psi pressure maintained in a 2400 psi tank for an extended period of time will drastically reduce its life with the result that it will in relatively short order either fail a hydro or in a worst case situation fail catastrophically.

Evidently there's a lot of incredibly stupid cave divers down here going through tanks like candy... or not.

Replace the burst discs with ones rated higher and you'll be fine.

Ben

 

[LUBOLD8431]

Actually, the best thing to do is to get rid of the Fabers, and get yourself some new PST E8-130's. That will solve the overfill issues to 3442 psi anyway!!!

 

[Ontario Diver]

Actually, these tanks can handle 3500 psi. Change the burst disk, and you'll be all set. They are used in Europe, and filled to 3500 over there. Just different specs in the USA to make DOT happy.

One other major issue. Some European tanks have a designated lifetime (5-10 years) after which they are expected to be condemded. (Much like fiber wrapped tanks.) IIRC, they can have higher pressures than the same tank in a North American sense, but they "wear out" where the North American ones could last forever.

I stil agree with FredT on the spanking issue tho' :spank:

 

[pasley]

... Just different specs in the USA to make DOT happy.

I would imangine that DOT did a bit of research before settingh the limits. They did not pull the numbers out of thin air.

I agree with the other comments. If in the USA, stick to the USA limits. No point in pushing the tanks to the edge. I would also question the compentency of the idiot who overfilled these tanks and bust the disk. No IMHO replacing a SAFETY DEVICE like a bust disk with a higher rating is not the recommended solution. Using the tank within its design limits is.

Oh by the way, putting the tanks in water DOES NOT PREVENT THEM EXPLODING. The water is there to take the expansion measurement by measureing the amount of displacement. If a tank lets go, water will not save you. The following links show the damage an AL80 that is NOT overfilled can do.
http://www.scubabomb.freeservers.com/Cscuba.htm

Here is a photo of a Steel tank that let go inside a car. Bottom ruptured, making it a missle. Note the bulge in the car roof and doors.
http://www.diveshop-pr.com/pages.dir/engl.dir/tankexplosion.html

A tank explosion could result in death or dismemberment.

Can you overfill a tank. Yes, Should you - no. Can you replace the burst disk, yes, should you no.

Bottom line, it is not just YOUR LIFE you are endangering by uping the burst disk and then overfilling, or even just heat expansion. You are also endangering the LIFE of ANYONE near by if the tank lets go (Dive shop employee, person just walking by on the beach etc). That could happen, especially if the tank gets a little warm in the summer sun.

 

[DeepScuba]

Pasley:

He said, and meant, the tanks are hydroed with water IN them for the reason provided.

 

[LUBOLD8431]

Ok, let me tell you something: the FABER cylinders are designed for 10,000 cycles to 4,000 psi... (yes, these are the LP ones, filled to 2640)

I think they are plenty safe enough to fill to 3500 psi.

As far as the DOT is concerned, they pull alot of stuff right out the air. Please dont defend the DOT. They are just another government agency that sometimes does things without having a CLUE...

[edit to include:]
ALso, the 3AA designation is over 60 years old!!! Thats right, it was around before world war II. Do you know where the 10% overfill came from??? HMmm??? It had nothing to do with any tests, or designs or metallurgy experts... It had to do with a shortage of pressure cylinders, so they had to get more out of each one. thats where the overfill came from. So, basically thanks to that, we get to overfill these tanks. Now, do you think the metal has stayed the same since the 1940s??? NO, actually the steel alloys that they use now are stronger, and can handle more pressure...

HURRAH for Pressed Steel for finally changing from 3AA to a designation that actually Makes SENSE!!! E SERIES...