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  1. #11
    Join Date
    Feb 2006
    Location
    Sacramento CA
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    80

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    Quote Originally Posted by Broccoli1 View Post
    I don't understand this line of thought as SOME ONE makes the tanks?

    Why can't Iron head or any one else that is qualified to do so make their own tank?
    Check the requirements necessary for a high pres. welding cert.

  2. #12
    Join Date
    Dec 2007
    Location
    Los Angeles
    Posts
    2,888

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    Quote Originally Posted by KEENAVV View Post
    Check the requirements necessary for a high pres. welding cert.
    As long as the person fabricating the Tank has the certs, what would be the problem?

  3. #13
    Join Date
    Mar 2006
    Location
    Queens NY
    Posts
    1,547

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    i think the problem is that the people who make the tanks, make hundreds and thousands of them. they have experience, empirical testing and certs. To make just one, you don't get any of that. I'd buy it so you can get the experience and quality of the above mentioned. Same reason some one who isn't an experienced welder shouldn't be doing critical work, and should pay a qualified person to do so, instead of suffering the learning curve for one job.
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  4. #14
    Join Date
    Jun 2004
    Location
    nj
    Posts
    204

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    Quote Originally Posted by Broccoli1 View Post
    As long as the person fabricating the Tank has the certs, what would be the problem?
    It isn't just the weld job itself... It is the design process, material verification, NDE On the finished product, and about 50 other things. The risk is much greater than the (possibly nonexistant) cost saving. The risk may not show for several years.

    For examlpe, a minor design issue led to some failures: http://www.cpsc.gov/cpscpub/prerel/prhtml02/02108.html

    To get an idea of the energy involved,
    http://www.railpictures.net/viewphoto.php?id=176187. The tanks on this locomotive arn't really that big. Well, weren't. Note the bent running board. The channel at the edge was maybe 4", maybe 6". The doors and engine compartment structure were also bent up (look at the roof... it is humped).

  5. #15
    Join Date
    Dec 2007
    Location
    National City CA
    Posts
    1,086

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    Quote Originally Posted by Iron Head View Post
    Better yet, hydraulic cylinders, steam lines, on and on and on.
    Not saying you can't. Liability is one issue. And I'm not referring to damage to your own home how about the guy next door. If you house catches fire that tank if pressurized and no safety valve will end up a couple of zip codes away. Same goes for hydraulic cylinders. Are you willing to bet your life on your welds. Training, experience, those are the qualities of the guy i want welding my steam lines, hydro cylinders, and air receivers. But then when you take into consideration cost of materials and fab time. Along with learning how and why the tanks are designed the way the are. Add in the threaded bung fittings and safety valve it starts to add up. and to me it just ain't worth it. Oh did I mention I'm a cheep SOB too. and I still wouldn't make an air tank that big even at half the cost of new.
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  6. #16
    Join Date
    Dec 2007
    Location
    National City CA
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    1,086

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    Quote Originally Posted by enlpck View Post
    It isn't just the weld job itself... It is the design process, material verification, NDE On the finished product, and about 50 other things. The risk is much greater than the (possibly nonexistant) cost saving. The risk may not show for several years.

    For examlpe, a minor design issue led to some failures: http://www.cpsc.gov/cpscpub/prerel/prhtml02/02108.html

    To get an idea of the energy involved,
    http://www.railpictures.net/viewphoto.php?id=176187. The tanks on this locomotive arn't really that big. Well, weren't. Note the bent running board. The channel at the edge was maybe 4", maybe 6". The doors and engine compartment structure were also bent up (look at the roof... it is humped).
    I did say 42 TONS of potential force
    Miller Syncrowave 200 W/Radiator 1A & water cooled torch
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  7. #17
    Join Date
    Sep 2005
    Location
    16919 Pole Rd. Brethren, MI 49619
    Posts
    4,412

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    I don't know how much 30 inch domes cost for that pipe but I would bet plenty, more than a tank. I bought a 12 inch for an oilfield job a while back and didn't look at the price, just passed it on but for it and a couple other parts it evidently was worth it to send someone on 2 hr road trip. The welding wouldn't worry me as much as some of the other design factors but the 3/8 wall pipe would certainly be adequate, not with flat ends though. I don't get too uptight about certifications for a lot of jobs but we usually know the design is overkill to some extent.
    Same with trailer hitches, I look a lot at the customer, I have refused to do them when I didn't feel the person or truck was unsafe such as a broad with a 78 Ford pickup with one working brake wants to hook on a 4 place horse trailer to this piece of crap, no tail lights or working brakes, I am not working on that truck period.

  8. #18
    Join Date
    Sep 2005
    Location
    16919 Pole Rd. Brethren, MI 49619
    Posts
    4,412

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    My Bud Cliff is another matter, would do any job he asked as he is fussy about his stuff, in good condition and takes every reasonable human effort to take care of it.

  9. #19
    Join Date
    Dec 2006
    Location
    Traer, IA
    Posts
    317

    Default Well.....

    I wouldnt do it - but I'm not a welder by trade either. I agree with the others that you definately dont want to use flat ends
    Attached are some pics of a compressor my Dad built me about 10 years ago. He used weld caps on the ends, pop off valves etc....
    Now before anyone jumps all over me, he was a pipe welder with all the certs and mostly welded high pressure steam lines for the local university and John Deere. He's retired now, but still the best welder I know of. I'd bet my life on that compressor never letting go, but on the same hand feel very very nervous filling a purchased portable air tank with 90psi, built by people who build them day in and day out (probably in China). I had a buddy on the receiving end of a purchased air tank that decided to let go. Wasnt a pretty site - the tank basically wrapped around his head. 10K later in plastic surgeory he still looks like Herman Munster (minus the bolts). Let me know if you would like any other pics of the tank. I'll get a picture of the tank that blew up on him when I get a chance - he kept it as a little reminder since the only thing he remembers is starting to fill it, then getting the hospital bill
    Attached Images Attached Images

  10. #20
    Join Date
    Dec 2007
    Location
    National City CA
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    1,086

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    Yep
    Here in California any pressure vessel larger then 10 gal has to be inspected every five years and be ultrasonically tested for signs of corrosion by Cal Osha. I don't remember off the top of my head but I think if the vessel lost 5% of it's wall thickness in any location the tank had to be retired. CalOsha has their own division just for pressure vessels.

    As for the small home compressors having a service life it's most likely due to the lack of an automatic drain. Without one the tank will eventually fill with water.

    First place I ever worked for had troubles with their air compressor. It wouldn't hold any real pressure or should I say it was cycling quite often like there was a high demand of air. Well no one listens to the new guy. And they proceeded to unbolt the compressor. and move it out and bought a replacement. turns out the compressor was half full of water. No drain on the tank no cycling air dryer nothing just a ball valve down stream of the tank in the air piping system
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    Millermatic 252 on the wish list
    Bridgeport Mill W/ 2 axis CNC control
    South bend lathe 10LX40
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    Over 20 years as a Machinist Toolmaker
    A TWO CAR garage full of tools and a fridge full of beer
    Auto shades are for rookies
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