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Thread: Shop Air Compressor Piping?

  1. #46
    Join Date
    Sep 2016
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    Modesto, CA, USA
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    9,876
    I read that OSHA has outlawed pex for compressed air within the last week. I would expect it is due to ageing since it is not allowed to see sunlight for more then 30 minutes or so before burial. It might also be that pressure cycling will cause it to creep off the fittings until it blows off completely.
    Bill

  2. #47
    Join Date
    Sep 2016
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    Modesto, CA, USA
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    9,876
    Be aware if you use pex it is tube size not pipe size. so to be equal air flow to 1/2 copper pipe you need to use 3/4 PEX. one inch PEX is a s big as you can easily find. that is only 3/4 pipe size.

  3. #48
    Join Date
    Jul 2017
    Location
    Abilene, TX
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    109
    A horror story with compressed air piping!
    i am a hobby wood worker, professional Corprate pilot flying Corporate Jets, with a degree in Electrical Engineering.
    i had nothing to do with the design of this fiasco. I was merely a beer sipping bystander, 1989 a small town 18 miles North of Tallahassee, FL in GA. This town had a small manufacturing facility for small boxes and baskets and wood things that were sold to a big name company that sold these items for a 500% mark up. The owner of the manufacturing facility made very little on her investment. However she provided work for those in the community and the workers provided a quality product.
    The company that bought her wares asked for more production with a cash infusion to expand an used part of her building! win Win.
    she needed more Air for her pneumatic tools that the employees used on the assembly line.
    I knew her husband from the airport that I flew out of, he was a private pilot a sharp individual, a retired civil engineer.
    he mentioned the expansion of the facility and asked if I had any recommendations on how to expand the compressed air system. I told him that is not my area of expertise and suggested he consult with Ingersal Rand.
    i was out of the loop.
    4 months latter we ran into each other at the airport on a Sunday afternoon. I asked about the shop expansion he said he hired a guy to design the system and install it and they were going to fire it up and test today since no employees were present. He said he had the beer on Ice (you can't buy Beer on Sunday in GA)
    Cool am game! (I had a Low beer light at my house) poor planning on my part.
    We arrive at the shop, he shows me the compressor it is a twin cylinder 3 phase 480 volt compressor!
    The cylinders must have been 5 feet in Diameter just kidding I asked what is the CFM and pressure output? He said he did know. But let's fire it up!

    As I was looking at this beast I saw that the pipe coming out of the compressor was 6 inches in diameter made of steel it disappeared into the ceiling through ceiling tiles and on to the work stations in the ne Facility. I was thinking that is a lot of volume not to mention available pressure.

    Art said grab the Cooler we are going to be here a while the compressor builds up to the working pressure.

    We pop the top on the beers Art starts telling me about the project and how it gone. The first contractor had a health issue and recommended another guy to complete the project. The second guy finished up and said he needed to be in Atlanta on Monday to start a new project and every thing was a go fire it up!
    So here we are the Pressure is on! We started the compressor, we are sitting on the loading dock, feet dangling sucking down the beers, a cool November evening 6:30 ish quiet surroundings, talking about flying, the compressor has been purring in the background for about 45 minutes.
    If you have ever herd a Sonic Boom this was about 20 times louder! And my body reverberated with the concussion of the air, and I was outside a100 feet from the rupture of the pipe. The failure was the 10 inch PVC pipe the second moron though he could inhanse the volume by adding 30 feet of 10 inch diameter pipe as a resivior (his words)
    the fire department showed up thinking that the building blew up. Folks a mile away said there was an explosion here.
    the point is don't use PVC for compressed air.

  4. #49
    Join Date
    Jul 2017
    Location
    Abilene, TX
    Posts
    109
    Part 2, I forgot to mention the moron that built the system did not speak English nor did he use pvc primer / solvent prior to glueing the pipes together, A chunk of The 10 inch PVC pipe blew through two Pieces of 1/2 inch drywall and impalled an office chair. The non English speaking person was better suited to conducting other task. I blame the guy that hired hired him. Not the poor guy doing work.

  5. #50
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298
    Quote Originally Posted by Lane Hardy View Post
    ... I blame the guy that hired hired him. Not the poor guy doing work.
    My stars!!! My experience with such things is with pressure vessel inspection back in the '70s. The energy in a 30' length of 10" dia cylinder at 100+ psi is astounding. When we pressure tested vessels with air we first lowered them into an underground bunker with a heavy steel and concrete hatch. Hydro pressure testing with water is safe if it fails (and silent).

    I do use extra length of hose to increase the reservoir volume - when using air tools on the farm with a portable compressor rather then run 100s of ft of electrical cord I run a short cord and 100s of feet of air hose. But PVC? Large diameter PVC? No. You can use PVC for vacuum reservoirs since the pressures are so low, but it has to be solid core not cell core PVC.

    JKJ

  6. #51
    Join Date
    Oct 2005
    Location
    Helensburgh, Australia
    Posts
    2,700
    My welding teacher was also a investigator of industrial accidents surrounding welding and he used to relate to us how accidents came about through stupidity. One he related concerned a high pressure air tank that was being built, two welders were leak testing the tank by charging it with air, locating leaks, dropping the air pressure then repairing the leaks. This process took a lot of time and it was Friday afternoon and they wanted to finish before going home so they decided to short cut the whole thing and get out of there. They were working on top of the tank so they leak tested, found the leak and began to weld and it simply blew up. Apparently the marks their bodies left on the roof of the workshop could clearly be seen after the explosion. Compressed air is dangerous but few of us realise how dangerous.
    Chris

    Everything I like is either illegal, immoral or fattening

  7. #52
    Join Date
    Jul 2017
    Location
    Abilene, TX
    Posts
    109
    Sorry for the thread drift but I wanted to add that 10 years prior to the stupid design incident I mentioned above, I had a part time job busting and mounting tires at an auto tire shop. I was airing up an automobile tire that had a blemish in the sidewall of the new tire, a foot operated valve on the tire changer stuck open when I released the foot pettle. Not knowing that the compressed air was still entering the schrader valve. The tire separated under right middle finger and blew the end of my finger off. Compressed air is dangerous!

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