10% overfill / Plus + rating on Steel LP tanks

[John Hoffer]

In response to my email question regarding the period for renewal, Mr. Thomas Ivey, SCUBA Product Manager of PST, has referred me to:

http://hazmat.dot.gov/exemptions/E09791.pdf

The current DOT exemption (DOT-E 9791) in effect for PST's HP steel tanks is dated November 12, 2002 and expires March 31, 2004.

The exemption references 49 CFR section 107.109 for renewal.

 

[John Hoffer]

I took a quick gander at the renewal section. I don't think anybody but PST or an equally competent manufacturer is going to be able to file for renewal. The renewal process requires a certification that the original application remains accurate and complete. Given the complexity of the exemption (and presumably the application process), DOT will have some understandable reservations if a party without the requisite expertise files for renewal. Certainly, the public's safety would not be well served if that's all it took.

The renewal application must be in the door 60 days prior to expiration of the exemption for seamless coverage.

I like HP steel tanks, and I'm still thinking of getting more. But there is an economic risk that I doubt think many divers understand. If the manufacturer abandons the SCUBA market for whatever reason, those HP tanks may easily become door stops.

I don't consider this a big deal, more of the in-the-FWIW department. I just enjoy sharing what I learn.

 

[John Hoffer]

Pescador775:

You will enjoy this. I am reversing my opinion to agree, in part, with you. I think the Hazmat hotline gave me bad information, but not for the reason you cited.

I am in the process of writing a request for a written opinion from the Office of Hazardous Materials Standards of DOT on the question of whether the "+" symbol is needed for the 10% overfill. In the process of writing this letter, I have given the CFRs a much closer reading.

First, as you noted, DOT fill limitations don't apply in the absence of a some involvement with a common carrier. For the sake of discussion, we must ignore that requirement because dive shops never really know where the tank goes after they fill it. Prudence dictates that they assume the worst.

Second, as best as I can tell, the process of hydrostatic testing for 2400+ stamped steel tanks is the same as any other other steel tank. The only difference for the "+" stamp is that certain average or maximum wall stress limitations must be met, which is a computational test using the elastic expansion determination. The "+" stamp signifies that the computational test has been met. (This is a bit of an oversimplification, but suffices for purposes here.)

This computational test may be done at any time during the life of the tank, not just during the first five years as my dive shop maintains.

I think what happens when you call the Hazmat hotline is that they are aware of proposed DOT regulations that will do away with the "+" distinction and change the service pressure to the 10% overfill amount. It's not unusual for an governmental agency to ignore existing regulations in favor of proposed regulations they prefer. The Forest Service has been administering "Wilderness Study" areas for over a decade as if Congress had passed proposed legislation making them actual wilderness areas.

I hope to get to the bottom this eventually. I don't think this issue is as simple as anybody has made it out to be. Bear with me.

 

[John Hoffer]

Last December I created a stink about some information I obtained from DOT. The US Department of Transportation (DOT) Info Center Hotline, 1-800-467-4922 told me, on two separate occasions, that once a tank is stamped "+" it may be overfilled by 10% so long as it continues to pass hydro, regardless of whether it is subsequently restamped with the "+" symbol. I also learned from a website that PSE's tanks do not have a lifelong DOT certification, but rather have an exemption. In addition to passing hydro every five years, the exemption must be renewed every two years or the tanks cannot be filled for use in interstate commerce.

After getting flamed on this board, I reviewed the regulations, which in particular caused me to question the validity of the advice the Hotline had given me.

First, I contacted PSE and they confirmed, by directing me to a copy of their exemption, that their tank's exemption must be renewed every two years. Normal 3AAA tanks (low pressure tanks) don't have this requirment. Case closed. No big deal so long as PSE stays in business. Put it in the "interesting information" category.

On January 7, 2003, I wrote DOT about the advice I had received on the phone. Last week I finally received a response.

As has been reported on this board, there is no limitation in the regulations on how many times a tank may be restamped with the "+" symbol when it passes hydrostatic testing. The LDS line that plus rating is only good for the first five years is a either a myth or a lie, depending on the sophistication of the shop.

The "+" symbol must be restamped on the tank each time it passes hydro in order to be overfilled 10%. This position contradicts what the DOT Hotline told me last December.

The hydrostating testing by water jacket method is exactly the same for normal and plus ratings. The only additional requirement (of significance) is that the wall stress calculation must be performed for the plus rating. This calculation is contained at 49 CFR section 173.302a(b)(3) and differ from the wall stress calculation for new tanks in 49 CFR section 178.3(f)(2). The plus stamp is essentially a notice that the tank passes the wall stress calculation.

Thus, the reason why LDS don't want to do the plus rating when you bring in your tanks for hydro is because they don't what to use a MS Excel spreadsheet to do the wall stress calculation.

I know my LDS about bit off my head when I told him my plus rating was renewable on my 2400 tanks. Told me I didn't know anything. Anybody who wants to confront his LDS about this topic, send me a self-addressed, stamped envelope, and I will send a copy of the letter authored by Hattie L. Mitchell, Chief, Regulatory Review and Reinvention, Office of Hazardous Materials Standards, U.S. Department of Transportation. Email your request for my address at john_hoffer_jr@yahoo.com.

 

[Dryglove]

I just recently went through this trying to get the + rating for two steel 72's that i purchased and needed hydro'd. This is what i was told and was unsuccessful in getting the + rating renewed.

Larry,
I have been doing more research on Requalifing the steel 72's. I called Bill High the president of PSI Scuba Tanks Inspectors in Washington. I discussed what you had emailed me about and I added my two cents worth. Well what the whole conversation boiled down to was that I am correct ( in part ) about the 5 year 10% over fill stamp and you're correct ( in part ) about the requalification. So if we put the two together we will be 3/4 correct. LOL
The last and most important part left is the Hyro Companys part in this. A tank can be re-qualified if the manufacturer has and will issue a ( RE # ) for that particular tank. I didn't get into the whys and wherefores of this # with the Hydro Company. In the past the hydro company has requested the RE# on a specific tank and waited an unreasonable amount of time before receiving it or finding out that the # wasn't available.
Danny at the Hydro company said he would try and get the re # for the two tanks in question. He would not promise results.

 

[John Hoffer]

Larry:

I've been told that sometimes the best place to get hydro testing for a plus tank is a shop that does hydros for fire extinguishers, i.e., not the LDS. Pull out your yellow pages and start calling. Cheaper too.

Best of luck.

 

[Uncle Pug]

John Hoffer once bubbled...
best place to get hydro testing for a plus tank is a shop that does hydros for fire extinguishers

...for pursuing and posting to this topic. I hadn't remembered that you were flamed... but in any event sorry that you were.

As for getting a + rating at the local fire extinguisher shop... Everett Carbonic won't touch it for some reason.

I have heard that there is a extinguisher shop in Seattle that will + rate cylinders that have an RE number which all of my PST LP104s do.

 

[Dryglove]

So what exactly is a RE number that seems to be the golden key to get a "+" rating?

 

[chrpai]

The advise around the MidAtlantic Yahoo! groups is to contact your local fire department and ask them who hydros there scba units.

 

[Bob3]

Every so often I get reminded how lucky I am, my hydro guy always goes with the "+" rating as long as the bottle qualifies.
It's almost enough to make me ship some of my 4400 psi tanks back to CA for the $12 hydro instead of shelling out the $20 surcharge the hydro joint here in Milwaukee charges for the extra paper shuffeling.

Trivia note: I have an email around somewhere from the CGA stating that a bottle that does not pass the "+" criteria will not pass hydro.