you cannot give these guys the answer the want. It's like a religion with them. They believe!!!
Once again, Leadking got it right. After the inane replies to my post, I gave up. Some guys can’t seem to grasp the fact that this is a cumulative effect. You can take arsenic and you may not die. You can even do it multiple times, thus convincing yourself it is safe. However, at some point you hit the cumulative limit and you die. You may not even take as much this time as you did last time, but when you hit the limit, you still die.
One guy actually looked up the info in 49 CFR 178, but then wrongly decided that since there is a safety factor, overfilling must be OK (thus eliminating the safety factor!) Try running any tool at 100% duty cycle, and see what you get. That's what an inexperienced fool does. A craftsman respects his tools.
For the super-genius who asks, "are you sure you know what you're talking about?", I won't introduce myself again, anyone interested can go to my first post:
Plus ratings and hydros Post#39
I'm astounded at all the people willing to put into writing their misinformed statements of "I think...", "I'm comfortable with...", "I consider..." Without any engineering data to back it up.
The real doosey was, "The reason testing is done with hydraulic rather than gas pressure is that you can't have a "catastrophic" failure, just a very sudden drop in pressure as the material gives. Doesn't even make much, if any, noise."
Ha! Tell that to the test operator who has to go home and change his underwear!! We had a cylinder blow inside a test jacket that startled me 150 ft away, inside the front office. It blew the bottom completely off the cylinder. Don't tell ME they don't make noise! Have you ever witnessed a burst test??? I've been to 10 different cylinder manufacturing facilities and over a hundred retest facilities in 20 different countries and worked with over 4000 test operators. (But then again, maybe I'm "not sure I know what I'm talking about".)
I am posting two photos of calibrated cylinders that have ruptured do to fatigue failure. These are examples of the "unnatural" failure that occurs with fatigue. It is not a ductile failure - it cannot be detected by visual inspection or hydrostatic test. When it goes, it goes - sudden and catastrophic.
I say "unnatural" because cylinders (other than composite) generally fail with a ductile bulging in the sidewall before the tensile failure causing burst. If you look carefully at the second photo, you don't see the characteristic bulging. Both of these cylinders burst BELOW test pressure! At manufacture, the burst pressure of 3A and 3AA cylinders cannot be less than 1.5 times test pressure. By cycling these cylinders at higher pressures, you LOSE that safety factor. There was no ductile bulging in the wall, just a sudden, catastrophic failure.
I say "catastrophic" because the cylinder burst before test pressure. No warning. A cylinder failing the hydrostatic test simply exceeds 10% permanent expansion - not catastrophic. Had either of these been pneumatic rather than hydrostatic bursts, they probably would have also been "catastrophic" in the sense of loss of life and/or limb.
Just because you "can" overpressurize a cylinder doesn't make it safe practice. Some of these guys just don't seem to get it. Each time you do it, you are losing some of the safety factor that was built into the cylinder. Cylinders are extremely safe - they are "over-designed". That's what KEEPS them safe. 3AA cylinders are designed for UNLIMITED service life - that means they live forever. We have cylinders that are over 100 years old. But when you overpressurize them, you are eating into that service life. It may not be you who pays. It may be someone 50 years from now who bought the cylinder at the auction of your estate, and 10 years later it ruptures. That may be meaningless for some of the younger people reading this post, but as for me, I don't want ANYONE'S blood on my hands.
I will not continue to reply to this thread. This simply isn't an issue of debate for me. One guy said that rules are for stupid people. Each time I get on an airplane I will thank God that that guy is not the pilot.
Darrell Garton
CTC Seminars