PVC for air according to OSHA

[Urban_Ops]

In my shop I ran 1/2" schedule 40 stainless, Tig welded in place with about 4" standoffs. I might take pics this week if anyone is interested.
I cannot believe anyone would use plastic for airline.

[Jose Rivera]

In my shop I ran 1/2" schedule 40 stainless, Tig welded in place with about 4" standoffs. I might take pics this week if anyone is interested.
I cannot believe anyone would use plastic for airline.

I did it because at the time I was short in moneys, plus reading the 600 lb rating on the PVC I assumed that it would be enough for a 7' run.
What I did considered and never crossed my mind was the danger of bursting on impact, which now mentioned it makes sense.

[Maddog55]

A little bit about myself first: My name is Matt, I live in Plano
Texas and I have a small shop where I do machine work on
Antique Kawasaki two-stroke triples as well as Harley Davidson
engines. I have a lathe, mill, TIG, Flowbench and some other
stuff like a cylinder boring machine.

(This is a hobby/side business, I'm a Telecom engineer for my
real job)
Nuff of that:

I can tell you first hand that PVC is NOT good for air line.

I had my shop plumbed for PVC a copuple years ago. it was
real nice, had the coily drops all around the machines and
everything. It was there for about 6 months without any trouble.

One night, I went out to the shop for a smoke, (wife won't let
me smoke in the house).

Anyway, I happened to be standing near the compressor where
the PVC line went up the wall and into the attic space.

While I was standing there, that line blew up into a thousand
little bits. It took the metal shielded cable that carried the
220V to the compressor with it. The explosion made a huge
spark when that (shielded) wire shorted out against the panel.

It knocked me to the ground and all the lights in the place were
out. I was lying there on the floor in total darkness. I thought I
was dead, I'm not kidding. I layed there for a minute and pinched
myself to see if I was still alive.

I escaped with only minor injuries (Thank God). I could have been
blinded or killed.

Bottom line: DONT USE PVC for AIR. Bad idea!

[Mike Walsh]

Can't we just let sleeping dogs lie?

[Bill Shields]

Somebody has a lot of $$ to use copper pipe at today's prices.

Much better than the white plastic stuff though.

[juiceclone]

Re: the comment about PEX pipe. It is not well enough known that PEX "cross linked poly" is EXTREMELY degraded by any exposure to ultraviolet energy as that found in sunlight, and to a lesser degree in artificial light sources. From experience, not just information, I have had PEX show pinholes, cracks and splits for no obvious reason. I thought this stuff was the best thing to come along, but even when it is used inside and just exposed to florescent light at normal viewing levels, strange leaks appear when used for either water or air over time. Outside it is gone in weeks. The worst part is that you as the consumer/installer of the pipe have no way of knowing if it was shipped or stored in an environment that resulted in exposure to UV somewhere prior to your buying it . I know it's being used all over the US now in potable water systems and hydronic heating systems, but based on my experiences with it, I will not trust it again. I am surprised there is not more discussion about this and/or the manufacturers have not addressed it. I read the ad above re: pex with aluminum lining, but don't know if this is related to the problem or not.

[Jim Jakosh]

I guess copper or steel is best, but I put sch. 40 3/4" pvc lines in both shops and have had them run for years without any problems. They run on the ceiling and get no sun exposure...Jim

[RCW]

Questions:

If I remember correctly, refrigeration lines and similar pressurized installations are silver soldered. Would that be advisable for air?

Of course, by the time you buy copper pipe and silver solder, your air may cost more than a good lathe. Can air hose safely be used as an economical substitute? I've seen one popular supplier touting air hoses for this.

I have a big--if seldom used--compressor. It sits outside under a roof. Should I do a hydrostatic test periodically? Is that done just like a boiler?

Bob

[Greg_Lewis]

This subject has been debated for at least 20 years, going back to the usenet rec.crafts.metalworking bbs. At that time I called a PVC manufacturer and spoke to one of their engineers. He said PVC is not rated for air and that it will get brittle in sunlight. But then he sheepishly admitted they use it for drops to their machines.

However, I just recently expanded my shop and decided to completely re-design my air supply. I went with copper as I can get it locally and it's easy to work with over black pipe. The price of copper over black pipe was not enough to make a significant difference. The PEX that's rated for air is not avail. around here and fittings are expensive.

Most important: when I pulled out the old PVC, I dropped a piece on the concrete and it shattered into a half dozen pieces.

[ccvstmr]

...despite the concerns about PVC pipe exposure to different kinds of lighting (UV, florescent, or other)...another source of risk is exposure to certain kinds of lubricants carried with the air thru the piping...synthetic lubricants in particular.

Was involved in an industrial incident back in the '80's when a polycarbonate "see-thru bowl" on a pneumatic system pressure regulator, filter, lubricator exploded. The polycarbonate bowl shards pierced a sound control wall that had a perforated metal skin with insulation in between. Thereafter, specs for pneumatic controls were modified to state..."metal bowls or metal shrouded polycarbonate bowls." Luckily, nobody was hurt...but if you think about it...specs, rules of the road and even RR General Code of Operating Rules...were basically written as a result of property damage and/or personal injury and hopefully eliminate (or at least minimize) the chance of a repeat situation.

It's not only the materials being used to be concerned with...there's also the fittings and method of installation to consider. Be careful...that's all. Carl B.

[Harold_V]

Be careful...that's all. Carl B.

Yep!
The real issue with using plastics that are not intended for use with air is what happens when there's a failure, just as has been described. Pipe made of plastic that is intended to be used with air doesn't shatter, although it can fail. When it does, it opens up and loses pressure, but does not create shrapnel. That's key to what is, or what is not, acceptable for use in air service.

I confess, I have a complete pvc air system. However, virtually all of it is encased in concrete, and what little is not is buried in insulation, in the attic of my shop. It has served for more than thirteen years thus far, without issue. It is always under pressure, as I never turn off my air compressor.

No, I do not recommend pvc be used for air.

Harold

[John_S]

We have PVC air lines in open air under our roundhouse roof that have been in service for more than 5 or 6 years. These are completely exposed to >90deg heat in the summer and <30deg cold in the winter. I think we run 80lbs in them at all times. Never had a problem with them.

I also have had PVC air lines in my shop for around four years now, although I only typically run 20lbs through them (up to 40lbs for doing riveting work), and have never had any problems either.

Living on the edge!