PVC for air according to OSHA

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Richard_W
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PVC for air according to OSHA

Post by Richard_W » Fri Sep 19, 2008 8:31 pm

I am posting this for information so that those unaware of the danger of PVC pipe can become educated on the matter.

http://www.osha.gov/dts/hib/hib_data/hib19880520.html

Also some other information from LASCO fitting INC..

http://www.lascofittings.com/supportcen ... sedAir.asp

There was a time when I thought PVC was fine for air and I learned the hard way it's not a good idea, when a pipe blew up on a fellow worker not 20 feet from me.

Harold_V
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Post by Harold_V » Fri Sep 19, 2008 9:12 pm

Richard_W,

The board owes you a debt of gratitude for providing the links, above. Please allow me to offer my appreciation for your efforts.

This should dispel the notion that PVC is acceptable for use with compressed gasses of all types, with rare exception.

Harold

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mechanicalmagic
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Post by mechanicalmagic » Fri Sep 19, 2008 10:35 pm

Richard_W,
My thanks also, many home shops have used plastic for air. (Myself included, many years ago.)

I would like to add that many plastics used for plumbing and tubing are degraded by exposure to sunlight and fluorescent lights at close distance.

Dave J.
Every day I ask myself, "What's the most fun thing to do today."
9x48 BP clone, 12x36 lathe, TIG, MIG, Gas, 3 in 1 sheetmetal.

Jose Rivera
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PVC

Post by Jose Rivera » Fri Sep 19, 2008 11:36 pm

I'll be getting rid of the short run I am using for air ASAP.

It leaks besides, so either the joints are not sealed good or the pipe leaks under pressure.

I have been considering going into 3/8 pipe for a while. Now I have a reason.

Thanks a million.
There are no problems, only solutions.
--------------
Retired journeyman machinist and 3D CAD mechanical designer - hobbyist - grandpa

10 Wheeler Rob
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Re: Plastic Plumbing

Post by 10 Wheeler Rob » Sat Sep 20, 2008 7:41 am

Yes, you guys are right, think safety first.

I work on design of new products with fuels, steam, other pressurized gases and fluids, as well as high voltages and burners and such. We due a lot hazard and failure mode and effect analysis. You would not believe what gets missed in some of designs.

There is an ANSI building plumbing code that covers the limitations and design properties of plastic piping in buildings, it dose not allow that much.

Often many over look the failure modes and what injuries or damage might result. PVC is brittle and if its lets go you got shrapnel flying.

If you can afford to run copper tubing it will serve you the best. No rust and and last forever.

I have run a remote air lines in doors on the cheep, using the 1/4 polyurethane tubing rated for air use with the push in fittings. Stands up very well and because its flexible you do not need a bunch of fittings to add pressure drop and failure spots. And if it did let go, its not going to have any flying shrapnel!

One aside note, my older brother a few years ago had bought an older air compressor, did not hydro test it or any thing. He had it in his basement, next to his water pump. One day it exploded, ruptured the water pipe near it and the water heater on the next floor above it. What a mess, but thank God no one was near buy to get hurt.

Dose any one have any recommendations for home air compressors, other than drain them once in while? It's not like many of us have the ability to due a hydro test, and would tend to too lazy to do it if we did.

Rob

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Steve_in_Mich
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Post by Steve_in_Mich » Sat Sep 20, 2008 11:37 am

Often many over look the failure modes and what injuries or damage might result. PVC is brittle and if its lets go you got shrapnel flying.
Yes! Note the date on the OSHA references, so it is a long time since the hazards have been known and reported. I suspect that the testing to identify the potential problems with PVC for compressed air service proceeded those letters by another 10 years. I recall working in a research group called "Plastics Fabrication and Treatment" in the early 70's where all kinds of plastics were constantly under test. One test that always comes to my mind when the subject of PVC air lines is mentioned is a "crazing test" where the crazing agent is oil. Exactly, oil sump compressor pumps do put out 'some' oil (if only in a vapor form) with the air that goes into the air system. The presence of oil on the surface of many plastic materials promotes crazing, early embrittlement and fracture failure.

Despite all the warnings, some insist on using or continuing to use PVC in pressurized air systems.
Dose any one have any recommendations for home air compressors, other than drain them once in while? It's not like many of us have the ability to due a hydro test, and would tend to too lazy to do it if we did.
Compressor inlet air filter and oil change interval is usually covered in the manual. Keeping up with these two items, clean inlet air and periodic oil changes, will increase the life of your compressor. The right ambient air temperature is also important. Actually testing the "pop" (overpressure relief) valves to be sure that they are not stuck to the seat (free to move) by pulling the little ring to expel some air every now and then lets you know that they could work if called upon. Draining condensate after each heavy use of the compressor is a good idea. Some folks like to add the automatic blowdown valves to handle this but personally I drain (bleed off) the tank so I can monitor what is collecting in the tank. How much water? How much oil foam? How rusty is the condensate?

I always recommend a hydrostatic test of any receiver you are in doubt about. Maybe you bought it used or it is just very old, in either case if you are uncertain of its condition - test it or have it tested. I do my own hydro testing - it's not difficult.

I don't know about lazy but I do have a tendency to procrastinate, maybe they are related, but it seems there is never enough time to do all that needs doing. Pick the important items. From a safety point of view keeping abreast of the condition of your compressed air supply has got to be high on the list.
Just because you don’t believe it - doesn’t mean it’s not so.

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Dick_Morris
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Post by Dick_Morris » Sat Sep 20, 2008 4:36 pm

Since PEX is a new generation of plastic, I was curious if it was approved for compressed air, but it apparently isn't. However, there is a version of PEX that is designed for compressed air:

http://www.flexalpex.com/
http://www.ipexinc.com/Content/EN_US/2_ ... ed_air.asp

From what I've read, I suspect standard PEX is safer than PVC, even though it's not approved.

Harold_V
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Post by Harold_V » Sat Sep 20, 2008 11:04 pm

I would expect that Pex is more flexible---more rubber like, so it probably doesn't burst with shrapnel. Certainly an improvement, at least from a safety standpoint.

It's rather amusing, how no matter how much evidence is presented, there are those that won't have any part of information that is not in keeping with their own concepts. Sort of reminds me of smokers that think it's not a source of cancer of the lung.

Humans will never cease to amaze me.

Harold

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bcody
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AGREEMENT

Post by bcody » Sun Sep 21, 2008 12:13 am

Like a child. You tell them something is hot and they have to touch it. Bill

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Berne Ketchum
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Post by Berne Ketchum » Sun Sep 21, 2008 11:02 am

Jose -- I had pvc air lines in a former shop and never had a problem, but chose to put copper in my current shop. I see you're planning 3/8", but my advice would be to go bigger. I have 1/2" copper line now with a run of about 30 feet, and the pressure drops if I'm using a air-hungry tool like a grinder or needle-scaler. I wish I'd gone to 3/4".

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Orrin
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Post by Orrin » Sun Sep 21, 2008 11:39 am

Jose -- I had pvc air lines in a former shop and never had a problem, but chose to put copper in my current shop. I see you're planning 3/8", but my advice would be to go bigger. I have 1/2" copper line now with a run of about 30 feet, and the pressure drops if I'm using a air-hungry tool like a grinder or needle-scaler. I wish I'd gone to 3/4".
I installed a long run of 3/4" air piping and now I wish I had gone even larger. The far end is roughly 150' from the compressor and the pressure drop is sometimes a problem.

If the cost of pipe hadn't shot up so high, lately, I would install a loop around the buildings where air is delivered. That would provide a dual path out to the far end.

Orrin
So many projects, so little time.

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Fender
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Re: Plastic Plumbing

Post by Fender » Sun Sep 21, 2008 5:13 pm

10 Wheeler Rob wrote: One aside note, my older brother a few years ago had bought an older air compressor, did not hydro test it or any thing. He had it in his basement, next to his water pump. One day it exploded, ruptured the water pipe near it and the water heater on the next floor above it. What a mess, but thank God no one was near buy to get hurt.

Dose any one have any recommendations for home air compressors, other than drain them once in while? It's not like many of us have the ability to due a hydro test, and would tend to too lazy to do it if we did.
This is an excellent point. Back in 1972, I bought a brand-new Craftsman air compressor. I ran it in my shop for many years. About three years ago, I turned it on, and the compressor shaft sheared off. I thought about fixing it, then thought about the rust which is in the tank......and said, "Nahhhh!". I bought a new compressor. Fixing up an old lathe or mill is one thing. An old air tank is quite another.
Dan Watson

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