Plastic air lines…. Don’t

Ohio Blue Tip · October 01, 2006, 10:08:29 AM

A good friend of mine (up north) just related a sad tale this morning. Seams he plumbed his garage with pvc 2" lines for the air system, it was a beautiful job and has worked fine for a couple of years. The 2" system is labeled 280 psi and it runs at 175 psi.
A few weeks ago an 8' run of 2" exploded into many pieces, fortunately no car was in the area as it broke one window, destroyed a speaker, stuck some holes in the steel ceiling, bent tool box and dented the steel garage door. Don't want to think what could have happened if anyone was in the shop when it let loose.
:!: DON'T USE ANY PLASTIC FOR AIR LINE. :!:

Dave · October 01, 2006, 10:29:16 AM

Quote from: "Ohio Blue Tip"A good friend of mine (up north) just related a sad tale this morning. Seams he plumbed his garage with pvc 2" lines for the air system, it was a beautiful job and has worked fine for a couple of years. The 2" system is labeled 280 psi and it runs at 175 psi.
A few weeks ago an 8' run of 2" exploded into many pieces, fortunately no car was in the area as it broke one window, destroyed a speaker, stuck some holes in the steel ceiling, bent tool box and dented the steel garage door. Don't want to think what could have happened if anyone was in the shop when it let loose.
:!: DON'T USE ANY PLASTIC FOR AIR LINE. :!:

Ya know Kenny.. Ive seen this done before and even did it at our plant cause one of my bosses wanted it done that way :!: Yup it broke No way would I ever do it again. It just isnt safe. Buy good old black pipe and use it.
Dave :!:

donsrods · October 01, 2006, 11:30:55 AM

It happens all the time, and yet people still think if they buy a certain schedule PVC or thickness it will be ok. IT IS NOT. I too have seen pictures of where one blew, and it almost took out a wall.

We had our marina replumbed for air a couple of months ago, and the pro who did it said he isn't even allowed by law to use PVC. Black pipe is the best, but galvanized is ok too. Some people say it flakes off, but we have it in our shop and have had no problems.

Thanks for posting this info, you might save someone's life.

Don

purplepickup · October 01, 2006, 12:07:17 PM

Thanks Ken. I've heard about plastic pipe exploding but never had anyone I know have it happen. Your friend should take some pictures of the damage just to have around for when this discussion comes up again.

Leon · October 01, 2006, 12:46:03 PM

Years ago I was researching codes relating to this and did find that a few places allowed PVC only if it was burried in the ground. At least there if it goes the schrapnel is contained.

WZ JUNK · October 01, 2006, 02:15:18 PM

Quote from: "Ohio Blue Tip"A good friend of mine (up north) just related a sad tale this morning. Seams he plumbed his garage with pvc 2" lines for the air system, it was a beautiful job and has worked fine for a couple of years. The 2" system is labeled 280 psi and it runs at 175 psi.
A few weeks ago an 8' run of 2" exploded into many pieces, fortunately no car was in the area as it broke one window, destroyed a speaker, stuck some holes in the steel ceiling, bent tool box and dented the steel garage door. Don't want to think what could have happened if anyone was in the shop when it let loose.
:!: DON'T USE ANY PLASTIC FOR AIR LINE. :!:

Interesting. Must be the Michigan weather. Most shops here use plastic for air. I have not seen 2" used though and not that much pressure. I think mine is 3/4". I guess when you visit me, you will need to keep alert. Mine is plumbed so that the drops come off of the top of the line and the main line near the ceiling slopes back to the compressor. I do not have problems with moisture. All the drops go past the quick disconnect and have a petcock drain at the end.

John

timkins · October 01, 2006, 02:23:23 PM

How about soldered copper? Mine is 3/4" for the main supply with drops of 1/2". The compressor runs at about 125# BUT I never leave the pressure on the lines only in the tank.

Crosley.In.AZ · October 01, 2006, 02:32:27 PM

I have used the PVC pipe for years , with no problems that I did not cause.

I use 3/4 schedule 80 at the base in the my shop. I use metal upright lines so I can bolt them to the wall. That way if I pull on an air hose I am not pulling on the PVC pipe.

Leon · October 01, 2006, 03:59:07 PM

Quote from: "timkins"How about soldered copper? Mine is 3/4" for the main supply with drops of 1/2". The compressor runs at about 125# BUT I never leave the pressure on the lines only in the tank.

What I've been able to find is the copper is OK but over years the soldered joints can develop small leaks (?) I've never seen or heard of that actually happening so that's what I used. The important thing is if a steel or copper line were to fail, it would split or crack, releasing the pressure. When PVC fails under the pressure of a compressable medium, it explodes into schrapnel. PVC is meant to carry fluids not gasses.

kb426 · October 01, 2006, 04:53:11 PM

What seems to happen is that the pipe gets some oil in it from the compressor. PVC attracts static elect. horribly. The ensuing explosion is the result of that. I don't know about using an airless comp., and I'm not brave enough to try. 15 tears ago I saw the result of an explosion in a friends shop. There were millions of little pieces of pipe on the floor after that. It literally blew up all the lines.

phat46 · October 01, 2006, 07:03:59 PM

I would never use plastic for any airline pressure, but why would anyone need to run 175#? Even the shop I work at, with a 50 h.p. compressor, only runs 110#. I run just over 100# at my home shop.

kb426 · October 01, 2006, 08:19:07 PM

I used to do the burst test on pvc for irrigation pipe at a plant I worked at. It's been more than 20 years ago so my memory is foggy. The pipe has either a 3 to1 or a 5 to 1 safety factor built in to the rating. I tested 14" and smaller down to 1" which was the smallest we made. When you had to check 215 psi pipe, the testing fixture would make a little noise getting to the burst point. I remember that you had to break the pipe and record the pressure. We've all seen pvc fail at times and when you take in the safety factor, it points at defects in manufacturing. If the extruder operator isn't watching the adjustment on the die, you can have thin spots or possibly pin holes. Then we can pick on the blender operator that mixed up the formula. Lots of options for the reason of failure. The 280 psi pipe should have had a burst test of at least 840 psi. I don't remember if ips had the same specs as pip. Thats iron pipe size and plastic irrigation pipe.

Crosley.In.AZ · October 01, 2006, 08:30:02 PM

Quote from: "phat46"I would never use plastic for any airline pressure, but why would anyone need to run 175#? Even the shop I work at, with a 50 h.p. compressor, only runs 110#. I run just over 100# at my home shop.

I have a Speedaire 2 stage compressor w/80 gallon tank. One of the older ones that really pump air.

It is capable of 175psi.... I have it set to shut off at 140psi.

Some of the best money I spent on a tool.

river1 · October 01, 2006, 08:35:38 PM

Quote from: "timkins"How about soldered copper? Mine is 3/4" for the main supply with drops of 1/2". The compressor runs at about 125# BUT I never leave the pressure on the lines only in the tank.

the newspaper plant i work at uses copper for all their lines. they run 175# for pressure also, this in a 125000 sq ft plant. when it was installed i asked the plumber doing it and he said type L. that is the medium strength copper pipe.

later jim

Leon · October 01, 2006, 09:36:43 PM

Quote from: "phat46"I would never use plastic for any airline pressure, but why would anyone need to run 175#? Even the shop I work at, with a 50 h.p. compressor, only runs 110#. I run just over 100# at my home shop.

I agree, 100 psi is plenty for a shop. I have a regulator on the output of the tank and with the tank filling to 175, there are many times that I do a smaller job without even turning the compressor on. When I do use it, the compressor cycles very little.