Tank Question..

[DA Aquamaster]

Joel, I just had two X7-100s fail on their first hydro with initial test dates of August 2005 and September 2005. I am not aware of them ever being overfilled - at least more than the usual 200 psi over until they cool - even in North FL. They have also not seen a great number of cycles as they have not been my go to tanks. Worthington has a procedure that is essentially identical the PST procedure but it only indireclty references the need to re-zero the burette, thus my concern is that both tanks failed due to a failure to properly perform the round out proceduce prior to the test.

My understanding of the need for this procedure with heat treated special permit tanks is that they are no longer perfectly round in cross section following the heat treatment process. Consequently when brought up to pressure, the tank does round out and increases its internal volume - but is not doing so do to excessive permanent expansion. That expansion due to normal rounding of the tank, if not properly zeroed out is what causes tanks to 'fail' a hydro test if the round out process is not properly done.

I have not gotten the test report back from the shop yet but when I get it, what do you recommend?

[Superlyte27]

Ok, so if you had to guess...
If I pick up a pair of PST LP104's with original hydro date of 6/01 and current hydro date of 4/07 I shouldn't have any problems? These aren't the tanks with the picky hydro technique?

[DA Aquamaster]

3AA steel PST LP tanks should last forever if not abused. As far as I know they are not subject to the same heat treatment process and should not have the same issues as the exempt/special permit tanks.

[Jay]

Joel, I just had two X7-100s fail on their first hydro with initial test dates of August 2005 and September 2005. I am not aware of them ever being overfilled - at least more than the usual 200 psi over until they cool - even in North FL.

I have not gotten the test report back from the shop yet but when I get it, what do you recommend?

Call Dave Zappala at Advanced Hydro Testing (352-422-1234) if he was not the one who did your tanks. It would help if you had the report but he can probably hazard a guess at what happened. If it was him, he will tell you exactly what happened. I have been in his facility numerous times and helped him a few times. We have had the discussion about that series failling hydro's and he believes it is a process problem with the facilitity in most cases, but I do not remember the intracacies of the conversation.

[gasdiver]

Joel, I just had two X7-100s fail on their first hydro with initial test dates of August 2005 and September 2005. I am not aware of them ever being overfilled - at least more than the usual 200 psi over until they cool - even in North FL. They have also not seen a great number of cycles as they have not been my go to tanks. Worthington has a procedure that is essentially identical the PST procedure but it only indireclty references the need to re-zero the burette, thus my concern is that both tanks failed due to a failure to properly perform the round out proceduce prior to the test.

My understanding of the need for this procedure with heat treated special permit tanks is that they are no longer perfectly round in cross section following the heat treatment process. Consequently when brought up to pressure, the tank does round out and increases its internal volume - but is not doing so do to excessive permanent expansion. That expansion due to normal rounding of the tank, if not properly zeroed out is what causes tanks to 'fail' a hydro test if the round out process is not properly done.

I have not gotten the test report back from the shop yet but when I get it, what do you recommend?

This makes sense to me. I would hope they have not destroyed your tanks before you can get a second test done, assuming they did not use the process where the zero was set at 85-90% of WP.

[KarsticGator]

The E-8's are rated to 3442psi, but have the testing pressure stamped on the tank. My E-8 130's (LP 104's) read "AA 3442" then "TP 5250". The testing facility should recognize these markings and not test them at 5800 psi. I use Alachua Fire Extinguisher, and they are fully aware of the new ratings (and new names for PST tanks).

[KarsticGator]

Ok, so if you had to guess...
If I pick up a pair of PST LP104's with original hydro date of 6/01 and current hydro date of 4/07 I shouldn't have any problems? These aren't the tanks with the picky hydro technique?

Just read the stampings on the neck of the tank. If it says "2400" then they are the "LP 104's", and they will be tested at 5/3. If the tanks say "3442", then they are the new E-8's. However, I think PST was still calling those tanks LP 104's in 2001.

[KarsticGator]

Jo,

I was told, off the record by someone at PST, that the LP and HP used different steel alloys, and that the 3442 E-Series was the same alloy they had been using on the LPs, so the E-Series was for all intents a HP with a 3/4 neck.

It was off the record so I can give no citation.

I thought PST closed up shop??

[Scott]

Just had 2 PST E7-100s born in 2005 tested this past spring with no issue up here in Va.


Scott

[Sludge]

the LP and HP used different steel alloys, and that the 3442 E-Series was the same alloy they had been using on the LPs, so the E-Series was for all intents a HP with a 3/4 neck.

I must have been smoking crack when I typed this, as it makes no sense. If the E-Series is in fact the same alloy as the LP, it is not related to the HP.

I don't think we'll get a definitive answer since PST closed up shop (thanks, unions), and I don't want to dispute what Joel said (after all, he's been at this a lot longer than me), but what I alluded to makes the most sense. If you stop testing a cylinder at 4000psi and begin testing it at 5200psi, you're going to get a higher failure rate.

I don't have any firsthand knowledge of a single hydro failure of a 2400 PST cylinder, even ones that have been pumped to 3600 for 35 years. But I know some people whose logic says, "If we can take 2400 tanks to 3600, let's take 3442 tanks to 4400." I believe this is overfilling them, and when you test them at 5200psi some are going to fail.