SurfLung wrote:
"They just kept stretching...".
That statement alone immediately tells me there was probably a leak.
I did a lot of hydros when I worked at Divers Service Center and any time I saw a tank that “just kept stretching”, it always turned out to be a leak. After a while, you get to recognize them very quickly.
The only explanation for the first guy's incompetence is that maybe they don’t see that many leaks anymore… maybe he never test tanks with tapered threads.
In any case he should have figured it out. At least he only failed them and did not condemn them.
SurfLung wrote:
- As for the special procedure of pre-testing galvanized tanks to 90% of final test pressure, the new hydrotest man said he checked all his references for a special directive and found none. But, he said on the other hand that the wording in the documentation indicates that there is nothing wrong with doing the test that way and so he was happy to comply with my request.
The special procedure is not driven by the CFR (the DOT codes). It is driven by the cylinder manufacturers and it is acceptable in accordance with the CFR.
At one time we used to do a similar procedure just to check for leaks, before the actual test. The manufacturers had not required that procedure, but I remember doing a quick leak check to 90% of hydro pressure on a regular basis. We used the 90% since it was specifically allowed per the CFR, but we only held long enough to check for leaks.
The fact that we did it as a leak test probably also explains why we also never had any failures on galvanized 3AA cylinders.
Actually a galvanized 3AA cylinder has a reasonable chance of passing even without the pre-stretch procedure, but the numbers are substantially better after following the procedure. The new high strength HP galvanized cylinders are more likely to fail if the procedure is not followed.
. The reserve rod has a neat little retainer that is held in place by the tank band so, I'm going to leave it this way and just install the rod on that side.
