Tanks Rated Pressure ???

[halocline]

As far as the 2400 /2640 goes this is from the goverment in WWII they demanded tanks that had woring presures that were higher than what you could get on th shelf. Instead of going through a redesign of vessels they permitted existing tanks to be allowed to use a working presure 10% above the rated presure. The 10% over fill was ok'd so long as hydro was good.

Now from the 60's i think that somewhere or other i heard that tanks could be hydroed once and that was it. perhaps once to retain the + on the hydro and then no more + rating.

That's not true, but it sure seems to be popular in dive shops. There was another thread recently about this. I also have heard that the practice of plus rating began as a materials shortage in WW2, but the rule is that as long as the total expansion of the tank during hydro is not greater than a specific number of CCs (called the REE number) then it gets the plus rating. Why this incredibly complex and abstract concept is beyond so many dive shops and hydro testers is beyond me.

 

[captain]

I will need someone else to perhaps further explain this. The US has what is called a safety factor. It is 4..... so a tank that has a burt psi of say 10k will be assigned a working presure of 10k /4 or 2500 psi. Other countrys use less than a factor of 4.

Next the european tanks as i understand is made of a different material (stronger) so they have a higher burst rating.

As far as the 2400 /2640 goes this is from the goverment in WWII they demanded tanks that had woring presures that were higher than what you could get on th shelf. Instead of going through a redesign of vessels they permitted existing tanks to be allowed to use a working presure 10% above the rated presure. The 10% over fill was ok'd so long as hydro was good.

Now from the 60's i think that somewhere or other i heard that tanks could be hydroed once and that was it. perhaps once to retain the + on the hydro and then no more + rating.

Im sure this should stir some up.[/QUOTE

The plus rating can be issued at any time, they need not be concurrent. It would be issued on a brand new tank then not after X number of hydroes and again issued on the current hydro. It all depends on who is doing the hydro and his willingness to follow the guide lines or knowledge of the regulations. As long as the results of the expansion measurements meet the guide lines for the plus rating it doesn't matter how long it has gone without a plus.

 

[NAM001]

I believe thos who have chimed in are correct. I was recalling from the 60's when i got my first tank that it was good for one hydro. It was a healthways tank 2250 72. Perhaps it was just that tank or policy changes have occured over the decades. I dont know. captains ost is what is currently being seen in my corner of the pond.

 

[captain]

I believe thos who have chimed in are correct. I was recalling from the 60's when i got my first tank that it was good for one hydro. It was a healthways tank 2250 72. Perhaps it was just that tank or policy changes have occured over the decades. I dont know. captains ost is what is currently being seen in my corner of the pond.

It is mostly ignorance of the regulations, lack of documentation of the REE values on older tanks but mostly the fact that most hyrdro shops do few dive tanks compared to commercial tanks. The commercial gas industry is not concerned about the plus rating, the gas is sold by the cubic foot not by the tank, only divers want more gas in a tank, the welder doesn't care, tank goes empty he just gets another so there is no incentive to do the plus the gas company will still sell the same amount of gas, just in two tanks instead of one. If divers would be willing to pay a couple of bucks extra for the plus then maybe it would be an incentive to for hydro shops to do it. Now if it is a dive shop that does hydros in house there is absolutely no reason the plus shouldn't be done other then the tank not meeting the requirements.

 

[Bob DBF]

...only divers want more gas in a tank, the welder doesn't care, tank goes empty he just gets another ...

Count me in with the welders, I'll take the time to get out of the water and strap on another tank.



Bob
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I may be old, but I’m not dead yet.