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Welding, hydrotesting a compressor tank

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  • #16
    Another Tank Story

    I was in a guy's garage (friend of a friend), leaning back against his bench, looking across the garage (open trusses). A light in my head went on and I said, "Hey, it looks like a can of paint exploded in here?" He pointed down behind my knees, under the bench, at a brand new air compressor. He said there was a gallon of paint on the floor, where I was standing, when the compressor tank blew. Luckily, his vehicles were out and the garage was uninhabited when it happened.
    RETIRED desk jockey.

    Hobby weldor with a little training.

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    • #17
      Working at the compressor shop I saw split/cracked compressor tanks on a regular basis. None were catistrophic failures luckliy. Most were small pits or cracks that leaked. Considdering the high volume of air screw machines produce, I could easily see a castistrophic/ large split if you had a OPV failure and/or reducing reg / hp limit switch failure.

      At the dive shop, I have personally seen no fewer than 4 alum 3000psi- 3500psi tanks split necks. All have been small cracks that leaked. One split just after being refilled, having just come back from passing hydro. We would frequently find neck cracks on alum tanks on eddy current inspections and fail tanks prior to the tank actually leaking.

      I have only personally seen the aftermath of 1 catastophic HP tank failure. That failure was in an O2 tank and there was 1 fatality and several injuries. I had a pict of the tank but can not find it right now. Again, most of the ones I have heard of happen either at filling or due to elevated temps such as leaving them in car trunks/sun etc. Again, most likely cause is burst disk failure.

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      • #18
        A follow up from the original poster of the question.

        I have been able to find a sensible deal on a good condition compressed air tank. I will throw my tank away or reuse it for pig roasting (have not decided). In any case, I drilled a hole in the tank already to warn any possible future user that the tank is not suitable for compressed air.

        if I actually throw it away, I will also weld a word "BAD" on it so as not to leave any doubt or room for unscrupulous sellers who may get it from garbage.

        So, the bottom line is that I will not use a tank. If chance of its explosion is only 1%, I do not want it.

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        • #19
          Here is another picture just for fun.


          -Dan
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          • #20
            IMO, it sure would be great to have a 80gal tank to build a real nice BBQ smoker out of. You could have worse problems
            Millermatic 180 Auto Set

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            • #21
              welding preasure tank

              depending on the age of the vessel..I have welded many "vibration" cracks in compressor tanks. Just clean the area...stop drill it and tig it. But, if the tank is an older tank, as has been brought out, there more than likely are other stress cracks that cannot be detected and in such case the tank should be replaced.

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              • #22
                Im my experience, linear cracks develop on old tanks, probably due to the expansion and contraction of the tank on a daily basis when in operation. Old tanks are out of the question, and I wouldnt even attempt it, but I would weld cracked new tanks all day long!
                If you want peace, be prepared for war!

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                • #23
                  Iraqi welder

                  This thread and all the talk about welding pressure vessels reminded me of the Iraqi welder...

                  Originally posted by 11b View Post
                  We took a pic of this guy on patrol. Sadly, you see it all the time. Yes that is a propane tank and yes he lived.
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                  80% of failures are from 20% of causes
                  Never compromise your principles today in the name of furthering them in the future.
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                  • #24
                    Man,
                    This thread makes me rethink my homemade sandblaster made from an old semi-rusty propane tank.

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                    • #25
                      Joe ;
                      How much pressure is going to be in your's ?
                      I Don't think I would worry about it !

                      ............. Norm
                      - Arcair- K 4000 CAC.
                      - LN - 25
                      - Lincoln Ranger 8
                      -DeWalt Compressor

                      www.normsmobilewelding.blogspot.com

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                      • #26
                        Darwin Award Winner!

                        Kind of off topic, but tanks and explosions made me think of an item in the news just the other day.
                        This kid was stealing gasoline from his uncle's truck, it was early in the morning and dark. He wasn't sure how full his gas can was getting. Being the Darwin Award Nominee that he is, he thought it would be a good idea to see how full his can was by illuminating the gas can with his cigarette lighter. This resulted in burns over 75% of his body.
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                        • #27
                          Originally posted by aametalmaster View Post
                          Wouldn't the proper hydro be more than the pressure it would run at? I also work in a refinery and the hydro's are always more than the service the vessel would see on a normal operating run.
                          That's been my experience as well. I worked at an ASME shop operating under the U,R & S stamps. We always hydro tested at well above operating pressure.

                          Bob,
                          Do you work at the refinery off Raff Rd.?
                          Blondie (Owner C & S Automotive)

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                          • #28
                            Don't do it!

                            You are correct to have dirtied your shorts and ceased operation. The most dangerous thing in the world is people that base saftey on the fact that they have never seen something happen. I used to be an air compressor technician for a living. I don't have the pictures to show it but have seen the results of a ruptured tank; It was a mobile unit in the bed of a 3/4 ton truck. The failure destroyed the truck. just for details a gasoline powered compressor has a control called a pilot valve that unloads the pump and controls the engine idler. Pilot valves fail all of the time; That's why there is saftey relief valve on the tank to prevent an over pressure situation. The saftey valve had failed, and to save a couple of bucks the owner installed a pipe plug in it's place. The pilot valve failed soon after and the compressor ran until the tank ruptured. Had the owner not been 300 ft. away using a paint gun he would be STONE COLD DEAD!!! Compressor tanks are assembled using submerged arc process at the factory and hydrotested at 1.5 times max working psi. You cannot duplicate these conditions; Scrap that tank and buy an new one. Remember 175 lbs is pounds per square inch. Multiply 175 by the number of square inches in your tank. Whole new respect!
                            Sometimes there's no second chances.

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                            • #29
                              Originally posted by davinci2010 View Post
                              You are correct to have dirtied your shorts and ceased operation. The most dangerous thing in the world is people that base saftey on the fact that they have never seen something happen. I used to be an air compressor technician for a living. I don't have the pictures to show it but have seen the results of a ruptured tank; It was a mobile unit in the bed of a 3/4 ton truck. The failure destroyed the truck. just for details a gasoline powered compressor has a control called a pilot valve that unloads the pump and controls the engine idler. Pilot valves fail all of the time; That's why there is saftey relief valve on the tank to prevent an over pressure situation. The saftey valve had failed, and to save a couple of bucks the owner installed a pipe plug in it's place. The pilot valve failed soon after and the compressor ran until the tank ruptured. Had the owner not been 300 ft. away using a paint gun he would be STONE COLD DEAD!!! Compressor tanks are assembled using submerged arc process at the factory and hydrotested at 1.5 times max working psi. You cannot duplicate these conditions; Scrap that tank and buy an new one. Remember 175 lbs is pounds per square inch. Multiply 175 by the number of square inches in your tank. Whole new respect!
                              Heres a couple pics: http://www.cdc.gov/niosh/face/stateface/ca/05ca010.html and http://www.railpictures.net/viewphoto.php?id=176187

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                              • #30
                                Build a smoker or a grill, do not attempt to use it! I just scored a 30 gallon tank from work that started leaking, when we cut it open there was crud in the bottom almost 2 inches deep the entire length of the tank. It had been drained but the drain was off set from the middle and there was always water left in the tank.

                                -Dan
                                Owner
                                DW Metalworks LLC
                                Miller Trailblazer 302
                                Miller 8RC Feeder
                                Miller Passport Plus
                                Miller Dynasty 200 DX W/Coolmate 1
                                Hobart Handler 135
                                Hypertherm PowerMAX 30
                                Smith O/A Torch Set
                                Plus more tools then my wife will ever know about....

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