Warning about hot fills!

[ianr33]

50 PSI/min is the recommended filling rate according to CGA (and maybe that's O2 and not air, but I think it's air). Now, go to a gas house and see when they have 75 or 100 O2 or air cylinders on the fill rack, it's easy to maintain 50 PSI/min. It's a little more difficult in a dive shop with 2 fill stations or on a liveaboard with 6.

Yes,but ,if I arrive in cave Country with empty tanks, that would take 76 minutes to get a decent fill.

 

[Wookie]

Yes,but ,if I arrive in cave Country with empty tanks, that would take 76 minutes to get a decent fill.

What else ya got to do. You're going to get there the night before. Drop your tanks off at Ed's and they'll be ready by the time you go diving.....

 

[Cleavitt]

One of my PST HP120 tanks failed hydro about 5 years ago due to over expansion. I was told it probably failed due to hot fills. Even the manager of the dive shop where it was filled most often agreed it was probably due to the hot fills.

If that were the case I would think there would be an awful lot of tanks failing hydro. Hot fills aren't exactly uncommon. More than likely the hydro test wasn't done according to PST/Worthington specs for HP DOT exempt tanks. There is a special procedure for hydro testing modern HP SCUBA tanks and many dive shops and hydro facilities are still not aware of this. If the procedure is not followed it can result in a "false positive." There are quite a few complaints on the Interweb of HP DOT exempt tanks from both PST and Worthington failing their first hydro because of this.

PSI-PCI - XS Scuba-New Hydro Rules

 

[captain]

If that were the case I would think there would be an awful lot of tanks failing hydro. Hot fills aren't exactly uncommon. More than likely the hydro test wasn't done according to PST/Worthington specs for HP DOT exempt tanks. There is a special procedure for hydro testing modern HP SCUBA tanks and many dive shops and hydro facilities are still not aware of this. If the procedure is not followed it can result in a "false positive." There are quite a few complaints on the Interweb of HP DOT exempt tanks from both PST and Worthington failing their first hydro because of this.

PSI-PCI - XS Scuba-New Hydro Rules

The hydro faclity get a copy of the rules along with my tanks when I take them in for hydro. Even LP tanks can end up with a false positive. It happened to a friend, the shop ended up buying him new tanks.

 

[drbill]

If that were the case I would think there would be an awful lot of tanks failing hydro. Hot fills aren't exactly uncommon. More than likely the hydro test wasn't done according to PST/Worthington specs for HP DOT exempt tanks. There is a special procedure for hydro testing modern HP SCUBA tanks and many dive shops and hydro facilities are still not aware of this. If the procedure is not followed it can result in a "false positive." There are quite a few complaints on the Interweb of HP DOT exempt tanks from both PST and Worthington failing their first hydro because of this.

The hydro test was done according to the PST requirements.

As I'm sure you know, hot fills are not necessarily strictly a function of whether the tank is immersed in a water bath but also how fast the fill is done. Many times my tank was the only one being filled at the time. When a dozen tanks are being filled simultaneously, the fill time is much slower.

BOTH of my PST HP120s failed, one due to over expansion and the other due to rust (common in tanks filled on SoCal dive boats) discovered during a VIP.

 

[Gilldiver]

50 PSI/min is the recommended filling rate according to CGA (and maybe that's O2 and not air, but I think it's air). Now, go to a gas house and see when they have 75 or 100 O2 or air cylinders on the fill rack, it's easy to maintain 50 PSI/min. It's a little more difficult in a dive shop with 2 fill stations or on a liveaboard with 6.

The Airgas, Praxair, and BOC regional fill houses I have been to do tanks in batches of 6 and will vacuum and pump them in less than 10 minutes - this is with any and all gasses up to 5.0.

 

[captain]

I have a steel 72 I bought new in 1957. The shop had a fill whip right at the front door as you walked in. They would hook up and fill in less than two minutes, you almost needed gloves to handle it after it was filled. I still use it and it still passes hydro.

 

[whaylonsmithers]

Have you heard anything back from the certification agency yet?

He was so upset that he filed a Q and A on us with our certification agency.
Comments.

 

[divezonescuba]

The certification agency informed us that we had not violated any standards, considered the situation closed, and need not even reply to the complaint. We did anyway since the letter gets retained in our file at the HQ.

I directly sent the individual a copy of our response just in case the certification agency did not forward one to him. In our response, I include all of the ignorant statements that he made during his visits and I also related his lack of cooperation with the usual liability paperwork.

 

[roastbeef]

I watched the technicians doing several hydro test on my OMS steel tanks he took it from 0 to 4700 psi in 5 seconds than quickly released the pressure to measure. Than stamped it good for another 5 years.