PVC for airlines (and why you shouldnt use it)

srmofo · May 11, 2010

PVC for air lines (and why you shouldnt use it)

I haven't been here long, but Ive seen this topic pop up often enough to think it deserves its own thread. Someone searching might find this a little easier with a specific title. This thread can also be linked so when other threads mention pvc. Its also been mentioned in other threads to quit threadjacking with the PVC debate.

1) When it ruptures it sends very sharp shards of plasctic flying in every direction. Anyone nearby is going to be hurt. Bad.

2) PVC becomes brittle with exposure to UV light and/or cold temperatures.

The results of the study (published as UNI-TR-5, "The Effects of Ultraviolet Aging on PVC Pipe") indicate a gradual decline in the pipe's impact strength. The lowest impact strength recorded after two years of exposure was 158 ft-lbf, or 75% of the original ASTM value.

The biggest risk I see is from impact damage to it. Its going into a garage/shop atmosphere and things do occasionally get thrown/catapaulted/launched around. It only takes 1 hit in the right spot to cause a serious incident. If it was only used for the mainlines behind a wall covering, I would consider it less dangerous just because its not as exposed to impact damage. HOWEVER I have no doubt in my mind that a 1"-2" diameter piece of PVC pressurized to 100+ PSI would blow a hole straight through drywall and most likely even plywood.

Heres a few links of pvc exploding, make your own judgment if it is worth it. Im aware its not from compressed air but rather from compressed gases. PSI is PSI though.

-Pics of shards

you get the idea search if you want more

Im not an engineer and I dont even consider myself an expert on the matter.

Edit * good catch D force

D Force · May 11, 2010

Maybe the Airlines should ban PVC in our carry-on bags?

trashauler · May 12, 2010

I have plumbed about three of our truck shops with PVC pipe. It is a maintenance nightmare. I never had any of it shatter, but repaired a lot of leaks. They seem to break near any joint when the temp changes. I made the mistake of doing it in one of my shops in Vegas. Big mistake we now use it for water line and ran pipe for the air line. It is amazing how much that stuff expands and contracts. I dont think I will be using it any longer. It is so easy to put up though and you can plumb an entire shop and be working rather quickly.

porschedude996TT · May 12, 2010

I went to copper after years with PVC. In hind sight, I consider myself lucky, or maybe it is just getting conservative in my age. I think I did it in PVC to save money when I didn't have much and rising children...

benjamming · May 12, 2010

porschedude,

Did you braze or solder the copper joints?

Hurricane_Whisperer · May 12, 2010

PVC explodes. It explodes dozens of feet away from the compressor and it explodes when no one is around to hit it.

Many people try to theorize and rationalize the breakage as a result of impact, heat, oil or other factors. This is a waste of time.

Our shop had it and it blew up at lunch when no one was around and the compressor was not running (receiver and lines were at full pressure though.)

I replaced all of it.

NUTTSGT · May 12, 2010

If you want to make a case against PVC then get some actual footage of airlines exploding, the type of links you have posted are what main stream media does when trying to portray a story "their" way.

A PVC pipe bomb, seriously, go ahead and do the same thing with your copper lines or galvanized lines with threaded caps

Wind turbine, notice the person posting under it in comments, says they have a 14 month life expectancy. The guy who built the one in the video, di dit to see what would happen, sounds biased to me.

Not even sure what to say about this one other looks like some complete idiots. I wouldn't be surprised if they even used glue. Yes, people are that dumb, my sisters old house, previous owner failed to use glue on the plumbing.

It quit working, so they kept adding hair spray, brilliant, self explanatory.

harvero · May 12, 2010

Here's one on PVC vs. ABS.

sgrammel · May 12, 2010

airlines <> air lines

rpsurfr · May 12, 2010

We need a T shirt..... PVC KILLS... some graphic of a pipe going postal.
Geez, :shocking:

gary300 · May 12, 2010

Are you nuts? Either one on those would kill you if went off close to your head. After all the warings on this site against any form of plastic for air lines, why would yoy even consider it? Insursance for the spouce?

srmofo · May 12, 2010

NUTTSGT said:
If you want to make a case against PVC then get some actual footage of airlines exploding, the type of links you have posted are what main stream media does when trying to portray a story "their" way.

A PVC pipe bomb, seriously, go ahead and do the same thing with your copper lines or galvanized lines with threaded caps

Wind turbine, notice the person posting under it in comments, says they have a 14 month life expectancy. The guy who built the one in the video, di dit to see what would happen, sounds biased to me.

Not even sure what to say about this one other looks like some complete idiots. I wouldn't be surprised if they even used glue. Yes, people are that dumb, my sisters old house, previous owner failed to use glue on the plumbing.

It quit working, so they kept adding hair spray, brilliant, self explanatory.

As stated (psi is psi), those videos were posted to show what pvc looks like when it ruptures. People dont realize how sharp those fragments are and the velocity they travel at. You're absolutely right I dont have any videos of it exploding when used as air line. I also dont know many people that put a video camera on a piece of pvc and hit record for several years. They do however turn on a video camera when they're about to do something stupid like pressurize a piece of pvc with a mini explosion. Yes those pressures go much higher, which is probably why you see so many spudguns exploding, that and idiots love to record themselves :beer:

Ill tell you what, If I have any free time this weekend (unlikely, but Ill get around to it sometime soon). Ill pressurize a piece of pvc and smack it with something, most likely a large , long piece of steel that I can just drop. What size pvc would you like to see it demonstrated on?

akdiesel · May 13, 2010

srmofo said:
Ill tell you what, If I have any free time this weekend (unlikely, but Ill get around to it sometime soon). Ill pressurize a piece of pvc and smack it with something, most likely a large , long piece of steel that I can just drop. What size pvc would you like to see it demonstrated on?

Way to take one for the team...

Dragster Racer · May 13, 2010

How about over pressurizing it to failure? That is the true failure mode. And have some foam pieces at various distances away. 1', 3' 6'
The attitude on this board sometimes drives me nuts. We have to remember that all of the information given here can at best be taken as opinion. Some folks have trouble believing that they may not be right, and have to convince the rest of the world that their way is the right way. It's pretty much why this country can't get anything positive accomplished in politics. Opinions are completely polarized.
My opinion about pvc and air: I wouldn't use it considering the other economical options out there. However, I have no problem with others using it. My only suggestion would be to protect areas where it can be damaged or where failure would be near people. Who on this board has seen injuries from exploding pvc air lines? Pictures?

Stuart in MN · May 13, 2010

If you were to go back through the many different threads here on the board about this subject, there have been a number of people here who have witnessed exploding PVC air lines. I'm one of them. In my case, it happened in the next room that was thankfully unoccupied at the time, so there weren't any injuries (it was a spontaneous explosion - no one bumped into the pipes or anything, they just blew.) However, there were shards of plastic stuck in the walls, so it certainly was a dangerous situation.

It's puzzling that this discussion keeps coming up over and over again, no matter how much evidence is provided to show it's not a good idea. If you were to look into it, the PVC pipe manufacturers all specifically state their product is not to be used for compressed air systems, and that's good enough for me.

benjamming · May 13, 2010

srmofo said:
Ill tell you what, If I have any free time this weekend (unlikely, but Ill get around to it sometime soon). Ill pressurize a piece of pvc and smack it with something, most likely a large , long piece of steel that I can just drop. What size pvc would you like to see it demonstrated on?

The larger the better...

englishwheeler · May 13, 2010

I'm wondering how the air psi differs from water psi...I wouldn't think it would. On my golf courses, we did all the irrigation piping with Sched. 40 pvc with 100-110 psi of water running through them. We never had anything rupture becuse of explosion. Now if a machine hit a pipe or sprinkler head, that was a different story. I was almost killed once when I was beginning to repair a broken head. As I was clearing the dirt around it to get access to the wiring, the head blew off. Thank God the wires were still attached, they caught the head from cracking my head. Needless to say I got completely drenched by the geyser that ensued.

Does the fact that these pipes are buried make them different? Or are you guys using thinner piping?

Our maintenance shop had pvc air line, but it was made with scrap irrigation line, so it was sched 40, something line 3/16" thick. Never had a blowout.

Please fill me in if air acts differently than water on these pipes. I'm curious.

Stuart in MN · May 13, 2010

The difference is that air (or other gases) are compressible, while water (or other liquids) are not. Also, PVC pipe is not ductile, like a steel or copper pipe - it will break into shards when damaged, where the metal pipe will just bend.

So, if you have a PVC pipe filled with compressed air and it's damaged, the pipe will break into pieces and then the rapidly expanding air will blow those pieces all over. If you have a PVC pipe filled with compressed water and it's damaged, the water is going to spray out but it's not expanding rapidly like compressed air will.

Maddabe · May 13, 2010

Buddies of mine run a garage here in town. Their air lines are all sch40. 15 years those lines have been in place and never a single issue. I am in FL so it never comes to a hard freeze down here but we do get frost and freezing temps a few times each winter. I've used sch40 for quite a few potato guns (pneumatic and combustion) and never had an issue. What are these guys doing to blow out their lines?

Stuart in MN · May 13, 2010

I don't think anyone has said that PVC lines WILL blow out, but they CAN blow out and that's part of the danger...there's no way to know, they could last for years and years with no problems but then again they could go any time. It's a certainly a concern in a commercial garage (where it's an OSHA violation) but in a home shop you also have to worry about the potential of injury to your family members. I think that's a pretty good reason in itself.

Jack Olsen · May 13, 2010

My grandfather smoked two packs a day and never got cancer.

The manufacturers of PVC piping say it's not safe for use with compressed air.

benjamming · May 13, 2010

Jack,

Not an apples:apples comparison considering there are many (infinite?) variables when discussing humans but much fewer when discussing materials such as PVC.

BTW, the oil from the compressor plays a role in deteriorating the PVC lines.

It boils down to managing risk.

rwhite692 · May 13, 2010

I had PVC air lines many years ago in my old place, however, it was all done with schedule 80 pipe and fittings.

I also regulated line pressure down to 120PSI or so, before the PVC sections.

Never had any failures or problems with it. However, the potential danger of PVC shattering and potentially causing injury is certainly well-documented.

I have worked in semiconductor industry for ~25 years, and for a long time, in many wafer fab facilities, sched 80 PVC was used almost exclusively for the plumbing of non-critical gases like clean dry air supply lines, and N2.

Before the OSHA ban on using PVC for compressed air, we had miles and miles of the stuff running around. I only remember seeing one actual mechanical failure and that was when a pipe got hit when a piece of equipment was being moved.

All of that being said, when I plumbed my current garage, I did it in all 3/4" black iron pipe. One less thing to worry about.

Stuart in MN · May 13, 2010

rwhite692 said:
I have worked in semiconductor industry for ~25 years, and for a long time, in many wafer fab facilities, sched 80 PVC was used almost exclusively for the plumbing of non-critical gases like clean dry air supply lines, and N2.

That's interesting. I would have thought PVC wasn't 'clean' enough for a wafer fab. I worked for a semiconductor company back in the 1980s, and when we built our wafer fab we used 316L stainless tubing for everything, both liquids and gases (I used a scrap piece to patch the gas line on my 1971 Catalina.

) However, since I only worked at that one place I'm not an expert on how it's done throughout the industry.

66HertzClone · May 13, 2010

When the manufacturer of a product recommends against using it, making the decision to use it is just stupid. Darwin award canidates, kind of like the idiot who used a 22 caliber bullet as a fuse and was shot in the leg as he drove his car.

rwhite692 · May 13, 2010

Stuart in MN said:
That's interesting. I would have thought PVC wasn't 'clean' enough for a wafer fab. I worked for a semiconductor company back in the 1980s, and when we built our wafer fab we used 316L stainless tubing for everything, both liquids and gases (I used a scrap piece to patch the gas line on my 1971 Catalina. ) However, since I only worked at that one place I'm not an expert on how it's done throughout the industry.

Hi Stuart....Notice I said, "non-critical" gases. Critical gases (anything that actually gets to the product) are indeed all done in SS.

Clean Dry Air used for equipment operation (such as would operate air cylinders, and the like) as well as N2 for purging dry cabinets, etc, was done with schedule 80 PVC routinely.

I'm not saying it's right to use PVC when plumbing for compressed air. Just merely trying to put some perspective on what it's use was, historically. It was in use everywhere in manufacturing plants, prior to the OSHA ban. Far and away, schedule 80 was what was used.

Jack Olsen · May 13, 2010

Jack Olsen said:
My grandfather smoked two packs a day and never got cancer.

benjamming said:
Jack,

Not an apples:apples comparison considering there are many (infinite?) variables when discussing humans but much fewer when discussing materials such as PVC.

BTW, the oil from the compressor plays a role in deteriorating the PVC lines.

It boils down to managing risk.

You might have misunderstood the point I was trying to make -- which is understandable, since what I wrote wasn't very clear.

Here's my point:

People use anecdotal accounts of PVC systems without failures as though it might be useful in making a decision about using the product that way. I think this is human nature, but it's just as sensible as deciding to smoke because someone you know did it and didn't happen to get cancer -- or to drive drunk because you've seen other people do it and not have problems.

The PVC manufacturers associations are against it. OSHA is against it. It seems clear that there are better materials for the application.

benjamming · May 14, 2010

Jack,

Thanks for clearing it up. I agree that anecdotal evidence is slightly worse than eyewitness evidence, i.e. essentially worthless to prove a point.

PVC for airlines (and why you shouldnt use it)

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