Help Validate Facts on Overfill to LDS

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Charlie99:
Not often at least. Not much comfort to the previous owner of the Dive Center of Sebastian, out in the Vero Beach, FL area, who died back in 2001 when a old steel tank blew up while he was filling it. Rusted old steel tank by Voit. Out of hydro.
Out-of-hydro also equalled out-of-viz. On the old steel 72's I used to fill for the commercial deep divers in Hawaii - the tanks had to be in hydro and I had to VIP them myself before I'd pump them. Most were fine. There were a few though that I condemned right on the spot. I showed the tanks to the guys beforehand, got their ok, and drilled a hole in the neck to end any further discussion. They never complained either.
 
NutJob:
I have personally seen a pair of tanks not pass their first hydro, the tank bands had grooved the tanks, they had been overfilled that much.
What was the ambient pumping temperature - 350°? I would love to see tanks band-bulged like that, and I'm sure the Ripley people would like to as well.
 
DEEPTEK:
All tanks sold in the UK, France, have M-25 valves. Thye do not have Burst dics.

Thats EU wide (part of the EN certification) not just those 2 countries.
 
wettek:
I would love to know where I can get a jacket whose Tank strap attachments will hold back a tank sufficiently to force a tank to distort around it. There is an awful lot of force required to distort a tank.Tough gear.

Double tanks with steel bands, not a jacket BC
 
in_cavediver:
Double tanks with steel bands, not a jacket BC


Sorry, but I think you will find the bands will stretch before the tank will "flow" around the bands. More like corrosion under paint, or the bands chafing on the tank to give the "bulged around the bands" look.
 
wettek:
Sorry, but I think you will find the bands will stretch before the tank will "flow" around the bands. More like corrosion under paint, or the bands chafing on the tank to give the "bulged around the bands" look.

My guess is that the tank will expand in the places of least resistance. The band area had more resistance to expansion than around it and therfore appeared to bulge around them....it still seems far fetched though.
 
wettek:
Sorry, but I think you will find the bands will stretch before the tank will "flow" around the bands. More like corrosion under paint, or the bands chafing on the tank to give the "bulged around the bands" look.

Oh quite agreed. I personally think the bulge is bunk. Otherwise I would have condemned my 104's years ago. I Just was clarifying that we were talking about doubled steel tanks not your average jacket BC as mentioned in post #80

Mike
 
Most shops I visit will overshoot by a couple hundred psi to give you an honest fill to the service pressure (or 10% overfill as appropriate for "+" rated tank) when the tank cools.

On the one hand I think any shop owner with brains understands the meaning of the CFR's and also realizes that tank pressure changes with temp and that consequently service pressure is dependent on temp and needs to be considered with the tank at room temp.

In short overfilling slightly to compensate for the tank being warmer than normal is an acceptable practice. The previously cited CFR reference that 3AL tanks can be filled to no more than their service pressure is a reference to the plus rating also cited in the CFR not being available for 3AL tanks, not a prohibition against filling warmer than normal 3AL tanks to pressures slightly and temporarily higher than the service pressure. After all, 3AL tanks sit in the sun and in car trunks as well, just like steel tanks.

A decade or so ago a company sold what amounted to a temperature indicating sticker for scuba tanks. It was designed to be stuck on the neck of an AL 80 and was intended to be used to assist the fill operator in determining exactly how much of an overfill would be needed to produce a tank with 3000 psi in it when it cooled to 70 degrees. I thought it was finally a very practical application of 1970's mood ring technology and a step in the right direction as it was more accurate than feeling the tank and estimating from that. But, I have not seen one in a long time so they obviously did not catch on. (I have not seen a mood ring in at least 20 years either.)

On the other hand, the federal government in general and the DOT in particular went through a period of over enforcement of it's regulations. I noticed this most in the actions of the Federal Aviation Administration who got overzealous in busting pilots for all sorts of minor unintentional minor infractions of the FAR's and even for things that were construed as infractions but were not by over zealous FAA inspectors (Bob Hoover getting jerked around comes to mind). But I have also heard stories from this smae period of dive shops being fined for overfillling by a couple hundred psi on a hot fill - something that would be legal per the regs provided the tank was at or below service pressure when it cooled to 70 degrees.

So even if those stories are an urban ledgend I can understand why some shops may be reluctant to do this even in the much more consumer freindly and relaxed regulatory enforcement climate that exists now.

My suggestion is that if you keep getting short fills, complain to the shop owner, spell out your arguments, tell all your dive buddies, and take your business elsewhere to hopefuly create an incentive for the shop owner to take a more reasonable view of the regs.
 
Is there a database of tanks that failed hydro? Just so we can see what the average life of a cyl is.... or was.
 
"The ASME Code requires that all pressure vessels, irrespective of size or operating pressure, be equipped with a pressure relief device that prevents pressure from rising more than 10% above the maximum allowable working pressure (MAWP) of the vessel. Two basic types of pressure relief devices are recognized in the code; reclosing and non-reclosing type safety devices. By ASME Code definition "A pressure relief valve is a pressure relief device designed to reclose and prevent further flow of fluid after normal conditions have been restored. A non-reclosing pressure relief device is a pressure relief device designed to remain open after operation." Rupture disks are non-reclosing type pressure relief devices. Both types of pressure relief devices are employed on microwave digestion vessels (22-27)."

http://www.sampleprep.duq.edu/dir/mwavechap16/mwave.htm
 
https://www.shearwater.com/products/teric/

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