Regulations concerning tank fills

[m3830431]

I have included a link to PSI's website that talks about this very thing. In my opinion, wet filling is an outdate practice. Check out the link and decide for yourself. http://www.psicylinders.com/library/wetfills.htm

Good article

 

[DA Aquamaster]

It's late and I'm tired so may be I missed some thing but I can't find anything on a scuba shop performing a vis every year. Only the visual inspection that is required for the hydro test. This is done by the hydrostatic tester Before the hydro, not by a scuba shop after the bottle returns from the test.

in fact the section pertaining to luxfers bombs says a vip+ every 5 years!

A VIP every year is a scuba industry standard, not a federal regulation. DOT regualtions only require the VIP as part of the hydro test (which for most tanks is required every 5 years, and every 3 years on a few exempt certified tanks.) The VIP is also done AFTER the hydro test, as many cracks that are not visible before the hydro test will be visible after the hydro test. Testers may look in the tank briefly when they devalve it to look for foreign matter etc, but the actual VIP is done after the hydro test and after the tank is dry.

A visual plus inspection was originally required by the manufaturer every 18 months on 6351 T-6 alloy tanks but is now also a federal requirement. In practice, the visual plus is done at the same time as a VIP, so when a combined with the scuba industry annual VIP standard, this means a visual plus inspection is done annually.

Water baths are not required but are controversial. They do help you get an honest fill in much less time with less temporary overpressurization of the tank and are not, as some people would suggest, inherently evil. But they do require an extra degree of care. If any water gets inside the end of the fill whip or gets inside the valve of the tank, it will be blown into the tank during the fill. In fact this is one of only two ways to get water inside a tank that is never fully emptied (the other way is a faulty compressor). So care is needed to ensure that any water is blown out of the whip and tank valve before they are connected to each other.

Of course the same is true for the valve on any tank even when filled out of a water bath as water from the dive, the boat, last night's rainfall, etc, has the potentintial to remain in the valve and be blown into the tank. DIN valves are particularly prone to this as small amounts of water have more places to stay (in the threads etc.)

The practice is less common today than before, in part because it is also more common today than before to overfill the tank by a few hundred psi so that the tank is at the service pressure when it cools. More people are realizing that if the tank is at it's service pressure when it cools to 70 degrees, it is not an "overfill" or illegal any more than it would be if you filled it to it's service pressure at 70 degrees and then left it on the beach or boat deck in the sunshine on a warm summer day.

 

[jdh]

A VIP every year is a scuba industry standard, not a federal regulation. DOT regualtions only require the VIP as part of the hydro test (which for most tanks is required every 5 years, and every 3 years on a few exempt certified tanks.)

Any opinions on the meaning of the 2nd paragraph of the linked .pdf?
http://www.text-trieve.com/pdffiles/06977.pdf


John

 

[OneBrightGator]

This is also useful when doing partial pressure EANx fills for the same reason, the 02 will cool quicker so you can get your reading, and finish the fill, so people don't have to wait all day for their bottle.

Warm, compressed and moving O2 is a BAD thing. O2 should be filled so slowly as to prevent any significant warming, if you're filling a bottle with O2 and it gets warm you are doing something seriously (read: possibly deadly) wrong.

With limited experience (0-15 dives) I hope you received thorough training in filling tanks, especially if you're handling pure oxygen, while the mechanics of filling tanks are simple, the cost for screwing up is high.

The best way to fill a tank is slow, easiest on the tank and safer for all involved.

 

[serambin]

Good article

I read that article and had a problem with the idea that by using water you get a higher pressure than the tank is designed to hold. The article states that after removal from the water and allowing the tank to come to ambient temperature . . . The water in a fill tank is surely above 70 degrees. If it wasn't before the tank was filled, the heat from the fill will raise it up above that temperature. If the temperature of the water is above 70 degrees, then how could it contribute to an overfill?

Fused again,

Stan

 

[PhilEllis]

Any opinions on the meaning of the 2nd paragraph of the linked .pdf?
http://www.text-trieve.com/pdffiles/06977.pdf

John, I will take a crack at this one. Remember, this is not a legal reading of the DOT Hazardous Materials standards, but it is my understanding after checking many sources and listening to many opinions..........

The Department of Transportation requires the following for cylinders used or offered in interstate commerce......

Hydro inspection every five years
Stamped DOT Permit Number or Exemption Number
Stamped with Approved Working Pressure

As far is me filling cylinders in my scuba store, there is no FEDERAL requirement that the cylinders be hydro inspected or meet the other requirements outlined above. The DOT requirements only apply to "cylinders used or offered in interstate commerce". If you bring your cylinder in my store and pick it up in my store, that is no FEDERAL requirement for hydro or any special stampings on the cylinder.

Now, if I TRANSPORT those tanks across any state border for a commercial purpose, such as providing to customers who have paid for a Florida dive weekend which includes the scuba cylinders, then the DOT requirements apply. Hope this helps.

P.S. There is a common sense safety issue (from the dive shops point of view) that lends toward a requirement to only fill properly hydroed cylinders that have been visually inspected each year by a properly trained inspector.

Phil Ellis
Dive Sports Online
www.divesports.com
(800) 601-DIVE

 

[drbill]

Interesting discussion. I've been under the assumption that tanks are required to pass VIP once a year and hydro once every five. Perhaps this is a California law. I know my two LDS'es won't fill a tank out of VIP or hydro. Good for them.

 

[Whitelightnin]

Interesting discussion. I've been under the assumption that tanks are required to pass VIP once a year and hydro once every five. Perhaps this is a California law. I know my two LDS'es won't fill a tank out of VIP or hydro. Good for them.

Not a California law. Just Industry practice. Most ALL shops will refuse to fill an out of vis or hydro tank (myself included) but it is not a federal law that we can't.

James

 

[kidspot]

FWIW My LDS pointed out that they do not use a water bath for filling as the water quickly reaches the same temperature of the tanks, thus getting rid of any possible benefit it had in the first place of being able to cool the tanks. Of course they fill 32 tanks at a time which is a LOT of heat being generated. Which was one of the main point in the above link...

To give good fills they fill to about 3200psi which cools to 3000 by the next morning when customers can pick them up.

Aloha, Tim

 

[DA Aquamaster]

Any opinions on the meaning of the 2nd paragraph of the linked .pdf?
http://www.text-trieve.com/pdffiles/06977.pdf

The DOT only has legal authority in matters of interstate commerce and it would be considered an infringement on state's rights if they did otherwise. So that paragraph is technically correct, although many states have adopted the same standards as the DOT, so filling an out of hydro tank could still violate state or local laws.

The issue of federal versus state jurisdiction and the potential for something to be used in interstate commerce has been a hot button issue in things like the legalization of marijuana for "personal" use. The feds maintain that marijuana grown for alledgely personal use has the potential to be used in interstate commerce and should be regulated by the federal government. They will further assert that allowing this exception would make enforcement of drug laws nearly impossible and would undermine the federal government's authority to regulate interstate commerce. States on the other hand will maintain that it's their right to legislate what happens within their borders and if interstate commerce is not directly involved, the feds need to butt out.

The same arguments extend to things like filling tanks as well. From a practical standpoint, if a shop fills a tank and it is then taken across state lines, it could be viewed as a violation of federal law. The DOT will in fact most likely make the assumption that the tank will cross state lines if a shop fills an out of hydro tank. Enforcement policies vary over time and from adminstration to adminstration.

Given the potential for all portable tanks to be taken across state lines, the average dive shop would have a hard time defending their actions to a DOT investigator if they filled an out of hydro tank unless they could demonstrate that they knew positively that the tank would not be leaving the state and/or unless the customer signed a waiver acknowledging that the tank could not be used in the course of interstate commerce or transported across state lines. But I doubt any shops are going to want to take that risk or go to that trouble.