Failed Hydro

[rob.mwpropane]

Couple of years ago when testing my tanks my hydro tester text msg me and told me the time to be at his place to watch my tanks get hydro tested. He really wanted me to see (and tell others in our club) that they have nothing to hide and it's a straight forward measuring process. You should set up an appointment with your tester and watch him test a fresh tank. You should do the same with your repair tech when they service your regulator and they'll happily show you the guts and what's good and bad inside.

Don't go and you won't know.

They don't do the test but every few weeks when they have a pile of them. I don't think that that would work. I'm almost 100% sure that there are only 2 hydro shops and this one is the one that all LDS use. Now does each LDS send the memo over each time for every group of tanks? Was this this guys 1st day? No idea.

Bummer! I've owned galvanized steel tanks for 15 years. At one point I owned 12 of them. Now I'm down to 4. I've never had one fail hydro. All 4 of my existing Worthington HP tanks have seen their 3rd hydro without issue. I always use dive shops that run a large volume of galvanized steel tanks through their hydro vendor. That helps me to feel comfortable that the facility is used to dealing with galvanized steel scuba cylinders. So far so good.

Yeah... I think I just got a rotten egg or they didn't do it right. This tank looked brand new on the inside. It was by all rights a brand new tank. Maybe it was just a dud... Idk.

Not sure I understand question.

1 tank is pressurized to 90% of TP.
2 tank is depressurized.
3 tank is pressurized to 100% of TP
4 cubic centimeters of elastic expansion are recorded
5 tank is depressurized.

If the measurement in step 4 is greater than REE, tank fails hydro. Unless I'm mistaken....

Thank you. That's what I was thinking, but thank you very much for the verification. I still don't understand what about running it to 100% causes it to fail? Why does it need to be "stretched" or "rounded out"? What does the galv process do that causes that?

 

[James79]

Thank you. That's what I was thinking, but thank you very much for the verification. I still don't understand what about running it to 100% causes it to fail? Why does it need to be "stretched" or "rounded out"? What does the galv process do that causes that?

As I understand it, the hot galvanizing process they used can slightly warp it (just a tiny bit out of round). So the initial 90% pressurization puts it back in round, then they do the full hydro pressure. Without the round out you get a false (artificially high) expansion number.

 

[rob.mwpropane]

So I called the LDS that I would think uses the same company I used. He verified that they do.... and then he said he had no idea what the 90% round out procedure was or if they do it. But he said they have tanks fail from time to time, always 3442 or 3500's....I'm assuming galvanized.

 

[Johnoly]

...What does the galv process do that causes that?

{Disclaimer>I'm not a certified hydro guy}
The galvanized surface produces uneven small surface stretch tensions on an empty PST galv tank. Those 'unevens' can cause an uneven REE on the 1st pressurization in the 1st step and hold pressure of a normal hydro test. By doing a pre-fill > depressure in the 1st test step, it normalizes those surface tension stresses. This means when the 2nd fill step of the PST hydro procedure is done, the base measurement point is now reset to a tank that has 'normalized surface tension stress'.

Some hydro testers say this is moving the 'goal post' and ?cheating?, but the federal procedures code allows for this and PST uses it. In the end it's just like a car mechanic,,either you trust them or you don't. If your car isn't fixed then most people find a new mechanic. If you don't trust your hydro guy then change. That's why my hydro guy let me watch his test and I trust him because I saw what he does in his shop. Regulator annual servicing is no different and everyone should ask their shop to show them how you gear is serviced so you TRUST the guy doing the work.

 

[rob.mwpropane]

{Disclaimer>I'm not a certified hydro guy}
The galvanized surface produces uneven small surface stretch tensions on an empty PST galv tank. Those 'unevens' can cause an uneven REE on the 1st pressurization in the 1st step and hold pressure of a normal hydro test. By doing a pre-fill > depressure in the 1st test step, it normalizes those surface tension stresses. This means when the 2nd fill step of the PST hydro procedure is done, the base measurement point is now reset to a tank that has 'normalized surface tension stress'.

Some hydro testers say this is moving the 'goal post' and ?cheating?, but the federal procedures code allows for this and PST uses it. In the end it's just like a car mechanic,,either you trust them or you don't. If your car isn't fixed then most people find a new mechanic. If you don't trust your hydro guy then change. That's why my hydro guy let me watch his test and I trust him because I saw what he does in his shop. Regulator annual servicing is no different and everyone should ask their shop to show them how you gear is serviced so you TRUST the guy doing the work.

Thank you for the explanation. That makes a lot of sense, even if you're not a hydro guy.

I was hoping that by using the hydro shop that all the LDS use that I would be in good company... I don't think that's the case though. I've said it before and I'll say it again. The area that I live in has to be one of the worst for scuba. I don't trust not one of them, hence why I tried to circumvent getting the hydro through the LDS and setup an account to go straight to the hydro shop. My tank would have failed either way because they all use this shop.

It amazes me that the LDS says that they get tanks fail from time to time. I know it's possible, but with what people tell me on here I would think that it's likely the hydro shop isn't doing the correct procedure if it happens "time to time".

Just a guess. I'm heading down to pick up the tanks tomorrow morning, so I'll talk with the guy. I have the paperwork and some ok knowledge to take with me. I'm not looking to make waves, I just want to make sure it was done right... if the tank failed then it failed. Better to fail than go on the backs of one of my kids.

Does anyone know if the test sheet for the hydro should dictate on it that the round out procedure was done.... or it just a pass / fail kind of thing? Can he say that "sure, we did that...", but there's no verification, or is that something that needs to be documented?



I REALLY appreciate everyone's insight and experience. So thanks!

 

[rhwestfall]

their word is all you will likely get.... The biggest error I have seen is to just use the minimum time to declare it failed the test. Talking with manufacturers, they have pointed out that the test procedure has a minimum time but includes language that it should be held "until it stabilizes". If they don't, the results will be a failed tank. They did it to me with a tank at the first requalification.... I know they didn't let it stabilize because the guy said they failed it at the minimum time (twice)....

 

[runsongas]

@rob.mwpropane did you watch the video on the xs scuba site for the worthingtons? it explains the roundout for galvanized tanks

 

[rob.mwpropane]

their word is all you will likely get.... The biggest error I have seen is to just use the minimum time to declare it failed the test. Talking with manufacturers, they have pointed out that the test procedure has a minimum time but includes language that it should be held "until it stabilizes". If they don't, the results will be a failed tank. They did it to me with a tank at the first requalification.... I know they didn't let it stabilize because the guy said they failed it at the minimum time (twice)....

I believe that I'm screwed on this tank. It's not the end of the world, and my diving life will go on. I just don't want to be back here again. In hindsight, I wish I learned more about the procedure and verified for sure that they in fact do it. The fact that they have failed a number of tanks tells me that there system isn't correct.

@rob.mwpropane did you watch the video on the xs scuba site for the worthingtons? it explains the roundout for galvanized tanks

I was in the middle of watching Alec P when you posted. I also went and watched the video from XS. There's no way that they did all that. The tank in the video wasn't even 1% out let alone 10%. From my understanding it has to exceed 10% to fail? The odds of them doing that correctly on a tank and that tank failing that's less than 20 years old and in mint shape is astronomical. They either didn't let it "stabilize" as @rhwestfall pointed out, or they didn't do it at all. And the fact that the LDS said they fail tanks from time to time leads me to believe whatever they're doing isn't correct. They just wouldn't have that many tanks fail. He said "all the ones that fail are either 3442 or 3500" and then he chalked it up to all from being "overfilled".


This doesn't really get me anywhere besides looking for a better place to hydro tanks. They'll never admit to failing a perfectly good tank, and I highly doubt that I could get someone else to test with it being XXX out the way they did. In the grand scheme of things I'm really glad it was just a cheap 80. Not that I need anymore hydro anytime soon..... but does anyone know a great hydro place in the MD, VA, DE, PA region?

 

[greeniguana]

My local dive shop is a certified DOT hydrotester :^)

 

[rob.mwpropane]

My local dive shop is a certified DOT hydrotester :^)

SW FL is a hop skip and a jump away, lol.

All our LDS locally, as far as I know, outsource between 2 places. I called both places. One was $25 / tank, the other was $40 / tank... I may have picked the wrong one, I don't think I'll ever know though. The $25 one was closer.

It'll be a while before I need another hydro test, all mine have been done in the last 2 years. Between now and then I'll find someone somewhere. It would be great to find an LDS that does it in house. I know some guys in PA that might have better places to go.

I own my own compressor, so LDS are a little leary when you say you want hydro but no VIP / fill.