Questions about LP72 tanks

[lowviz]

Read this: Older steel tanks?

Tape a sheet with that procedure to your tank and try another test facility.

 

[guruboy]

Read this: Older steel tanks?

Tape a sheet with that procedure to your tank and try another test facility.

Thanks. I read a bunch of threads a few years ago before I bought my first LP72. Don't think I read that one though. My tank was actually just tumbled prior to this hydro so the interior and exterior look great (and passed visual inspection).

Something always seems to come up when I'm trying to get my old LP72s hydro'd. When I took my first one to get tested a few years ago, it was refused for "being too old" by the first facility I tried.

 

[guruboy]

I just found this thread which talks about hydro on older steel tanks.

The OP had the same situation as me, tank failed hydro with 14% expansion. He had it re-tested and passed. I think I'll take my tank to get tested at another facility and see how it does. If the second time also fails I will scrap it.

 

[guruboy]

In case anyone wants, I'm attaching PDFs of the PST D100-E bulletin Luis has mentioned and the PST REE values (58.4 for PST LP72).

Also, here is a video explaining the round-out procedure.

 

[guruboy]

Regarding the CFR (Code of Federal Regulations) CGA (Compressed Gas Association) information, I found this website with what seems to be the relevant information for hydro testing- 49 CFR 173.34

49 CFR 173.34(e)(4)(v) states-
"(v) Minimum test pressure must be maintained for at least 30 seconds, and as long as necessary for complete expansion of the cylinder. A system check may be performed at or below 90% of test pressure prior to the retest. In the case of a malfunction of the test equipment, the test may be repeated at a pressure increased by 10 percent or 100 psi, whichever is less. This paragraph (e)(4) does not authorize retest of a cylinder otherwise required to be condemned under paragraph (e)(6) of this section."

So it looks like during equipment malfunction, the test is to be repeated with a 10% or 100 psi increase in pressure, whichever is less (100psi for LP72 tanks). Not sure if operator "error" falls under "equipment malfunction" but I'll make sure I take a copy of the PST D100E bulletin to the second hydro facility.

 

[halocline]

My experience with hydro facilities around here is that almost all of them are woefully ignorant about scuba tanks. Some of them are also arrogant and refuse to even discuss any of these issues with a customer. The best you can hope for is to find a facility where you can talk to the person doing the test, show him the stuff from PST, and ask him nicely to follow the correct test procedures.

I almost got thrown out of a hydro shop because I disagreed with the owner's insistence that my LP72s were "high pressure". Another shop stamped the words "no plus" on my 72s because I had requested a plus rating and he wouldn't qualify them because he didn't have access to the REE. (I had given him the pst REE document, but he didn't trust that it was authentic) A third shop did a VE test on a 10 year old catalina AL80 because he said "all scuba tanks need this test, it's the law".

So hydro testing for a LP72 is an adventure.

 

[tbone1004]

no kidding, thanks for correction. I knew my shop did it on all tanks regardless, but didn't think it was necessary for the low pressure series.

 

[guruboy]

I think for compressed gas tanks as a whole, scuba tanks are all considered high pressure.

The 2-step hydro isn't required, but it seems it is highly recommended to keep your tank from failing false positive.

 

[guruboy]

I went back to the hydro shop and asked them about the steel tank testing. They are aware of the round-out procedure like the one mentioned in D100E but they only use it on steel tanks stamped with the exemption (according to them there is a separate section for that). On 3AA stamped steel tanks, they only do the standard hydro test. They will not perform the round-out procedure on a 3AA stamped tank.

 

[guruboy]

Most of the 72s I've seen are painted over a galvanized primer. It's very easy to remove the outer paint and leave the primer; you can then spray a bit of ZRC galvilite cold galvanizing compound on them.
...
But, on the bright side, I haven't found much, if any, difference in getting fills for my plus rated PSTs and my non-plus rated WKs. ...

I saw you posted that you had some WK tanks. Were they paint over galvanized primer? If so, is that hot dipped galvanized still (did they even do cold galvanized tanks back then?)? Trying to figure out how to verify my tank was hot dipped galvanized. It is not paint. The hydro shop said, "it is not galvanized, just a regular steel tank" but couldn't explain what the dull gray coating on it was...