Oxy/Acetylene Cylinder Question

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How are tanks hydro tested, and what causes them to fail?I understand they are submersed in water and are subject to blowing up when bad, but assuming they don't blow up, what determines a pass/fail?
Reply:Each time a cylinder is pressurized it expands, and when vented it contracts, in time this cycling fatigues the barrel. As the barrel fatigues, it expands a greater amount than when new.A cylinder being tested is filled with water and submerged in a water filled test chamber of a known volume. While submerged in the water filled test chamber, the cylinder is pressurized. Since pressurizing a cylinder causes the walls to "balloon" an amount of water is displaced from the test chamber. Because water practically doesn't compress, the amount of water displaced from the test chamber is an accurate measurement of the cylinder's expansion. When compared to known specs, the pass/fail can be determined by accurately measuring the volume of water displaced from the test chamber.Hydro-testing is relatively safe, because the rupture of a water filled vessel causes only a relatively harmless exhausting of the water, unlike the catastrophic explosion of a rupturing gas-filled vessel.When swapping cylinders, I find it interesting to check the stamped build and test dates; there are a lot of 100 year old cylinders still in service.Good Luck
Reply:Originally Posted by denrepWhen swapping cylinders, I find it interesting to check the stamped build and test dates; there are a lot of 100 year old cylinders still in service.Good Luck
Reply:I think some of the old cylinders were made pretty darn well. I've seen some very old ones still in service also. I can't recall any over 100 yrs., but it wouldn't surprise me.
Reply:The LWS I work at has seen cylinders as old as 1886, and they still passed! Usually the ones that fail are the ones that have been in Co2 service, as the liquid Co2 sitting in the bottom of the cylinder would cause the steel to weaken. I used to run a hydro tester back in 92' and only had two cylinders fail in 11 months, but man when they blew you were glad they were submerged in a water jacket. One day we had 4 cylinders come in from a scrap yard to be tested, and they still had the Swastika symbol on them from WW2, I showed these to my boss, and he brought a "special stamp" out of his office, this stamp was used to close the Swastika symbol to make it look like a square box.
Reply:Originally Posted by ss42768...they still had the Swastika symbol on them from WW2, I showed these to my boss, and he brought a "special stamp" out of his office, this stamp was used to close the Swastika symbol to make it look like a square box.
Reply:Acetylene tanks are different than all the others because they are filled with a porous material, (used to use Kapok, asbestos and various other neat stuff) which is saturated with acetone. The acetylene dissolves in the acetone and the pressures are relatively low, a few hundred psi vs a few thousand. Acetylene tanks fail more from settling of or damage to the filler rather than the tank itself, since a void inside can cause problems. I once acquired a few C02 tanks when a bowling alley closed. One still was fairly full, so I set it in the yard. One nice summer day a year or two later, I was in the yard and started hearing a high-pitched hissing. The tank had developed a hole a few inches above the bottom, and the gas was leaking out. When it was empty, I found it had 'water' inside and had rusted through from the inside out. I don't know if it hadn't been properly checked before refilling, or somehow got the water in later. It had been used with a beverage carbonator system, so maybe it was actually Coke rather than water.
Reply:Originally Posted by denrepEach time a cylinder is pressurized it expands, and when vented it contracts, in time this cycling fatigues the barrel. As the barrel fatigues, it expands a greater amount than when new.A cylinder being tested is filled with water and submerged in a water filled test chamber of a known volume. While submerged in the water filled test chamber, the cylinder is pressurized. Since pressurizing a cylinder causes the walls to "balloon" an amount of water is displaced from the test chamber. Because water practically doesn't compress, the amount of water displaced from the test chamber is an accurate measurement of the cylinder's expansion. When compared to known specs, the pass/fail can be determined by accurately measuring the volume of water displaced from the test chamber.Hydro-testing is relatively safe, because the rupture of a water filled vessel causes only a relatively harmless exhausting of the water, unlike the catastrophic explosion of a rupturing gas-filled vessel.When swapping cylinders, I find it interesting to check the stamped build and test dates; there are a lot of 100 year old cylinders still in service.Good Luck