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Compressed air lines

C

coshoo

Well-known Member
I've got PVC air lines now, am told they are a bomb waiting to happen. Rehabbing my shop, so want to do it right. What say you? I know copper would be great, but need to go about 1 inch diameter and I think I'd have to get a second mortgage to use copper.
 
coshoo I just installed 3/4 rapid airline in my shop. Bought a 100 ft kit from northern. I m not far from ya if you want to see it. e-mail is open. RB
 
I used all 1/2 black pipe, ball shut of valves & added a dyer, has worked fine for 25 years.
Compressor shut off at 200psi. I don't use much in 3/4 impacts on 1/2.
 
PVC shatters when fails, sending schrapnel. Steel. Sweated copper. Plastic/rubber lines made for air pressure are advised.

How many times have you tugged on an air line, pulling sideways on the air coupling?
 
what makes you think you need a 1 INCH LINE unless you have a several thousand dollar rotary there is no way a 1 inch line is needed 1/2 inch for shop use is more that the ordinary compressor could supply be sure to run the line in a complete circle that way you will never run out of supply.
 
I built my shop 20 years ago and trying to conserve $ stretch the air lines into the equipment storage area used 1 1/2 inch PVC; the building is 138 feet long by 40 wide and I had air outlets on both sides at each bay. PVC is easy and fast to install EXCEPT you have to fasten it to a hard surface every few feet, 12 isn't close enough. With 100+ psi in the line it will slowly stretch and bow between the attachment points until it reaches the failure point, then it just comes apart. I redid the lines with 3/4 inch main copper line with a drop to working height (4 FT.) between every other bay and only on the front wall. So with 6 bays 16 ft wide and the ceiling 16 high it made for 3 out lets plus the shop. Yes it was expensive but not as bad as constantly redo in the PVC.
I did learn to cap of the pipe at the shop to storage area and at each bay; pressurize the line and check for leaks--less joints to check. When you cut the cap do keep your body parts out of the outlet of the pipe. I still have pipe bits in my arm.
In retrospect I think 1/2 inch pipe would have worked also.
 
I am assuming galvanized pipe is fine? I tried black pipe for a bit and didn't like the rust particles that would show up.
 
I haven't tried it, but PEX has been successfully used. Even though it's not officially approved, it is a low cost and easy install, just keep it away from heat and direct sun. I would still use black pipe for the drops.

There are a lot of plumbing diagrams on the net and Youtube how too's to follow. Shows how to angle everything up from the compressor so the condensate will go to the tank. Also come off the top of the trunk lines to get dry air.

I like a lot of valves so I can isolate sections without having to shut everything down. Also install an occasional union, and a lot of tees, plug the unneeded end for expansion later.
 
I used hose designed for air pressure. Air hose goes around objects easier than ridged pipe and easy to replace if needed.
 
I checked that out, RB, looks like the way to go. I don't get down toward Raymond too often (you're near Willie's Grave, I think), but I'll get in touch next time, and set up a meet.
 
What air pressure are you running on PVC. If you regulate it down to 120 psi or less there isn't anything wrong with using PVC for air. I've been using PVC for air for more than 45 years without any issue. I have worked at other shops that used it and had it break sometimes but they didn't have it set up right. If you change from PVC to galvanized pipe where the couplers are you can better attach the pipe to the building. It's yanking on the air hose and breaking the pipe which caused any problems, not that it just fails and explodes. That I've never seen happen anywhere.
 
(quoted from post at 14:41:48 02/01/18) don't know what would be wrong with pvc, I have 1" that if glued is rated for 350 pounds
Click to expand...



You don't want to be around it when it decides to let go, friend of mine had to go the ER so they could get all the pieces out of his arm.
 
Copper is forever and very pretty if you clean and lacquer it. If you have a really good scrap yard it is amazing what shows up now and then. Just as long it is from a job and not ripped out of someones house!!!! I did a small system from my basement with yellow hotwater plastic. Only broke one time whem I hit it. If you are only doing a short run do the far end or the close end in copper and in a few months do another section. That way you spread the expence and where you stopped you can put in a T or a drop line and ball valve and then continue on from there. What ever floats the canoe. You want plenty of drop pipes with little blead valves for condensed water.
 
As a plumbing contractor we are no longer to use any air pressure to test newly installed pvc waste lines for new construction. The test before was 3 psi. Manufactures of pvc pipe came out with no air pressure to be used in any pvc lines. All plumbing inspectors will fail any job that has air pressure. They will not even come to your job. To many injuries with air pressure. Fyi
 
I just looked up copper pricing seems to have come way down, Menards had 3/4 x 10' for 17 bucks.
 
WOAH..that is something I haven't heard. How about do a hydro? Fill the system right to the top with water and then put air at the top? Like 40 or 60 pounds for normal house pressure? I know here at work they have the stand pipes in the parking garages and they are tested at 175psi. Never been around when they test but have been here a couple of times when the frozen sprinkler system thawed out. Nothing like Niagara falls running down the parking ramps!
 
Use of PVC for air lines has hurt enough people that it is not allowed by OSHA unless underground or encased in a burst resistant housing or shell.

As mentioned by a couple others here, oil is a big factor in the cause of burst PVC pipe. Most compressors pass at least some oil with the air.

I've seen the end result of a 3" sch 80 pvc burst. Shards of that pipe were found in every portion of the shop up to 200' feet away. That company was super lucky as it blew first thing in the morning when the shop foreman turned on the compressor and then went into his office. No other employees had arrived yet or were in the building at the time of the explosion.
 
(quoted from post at 12:16:29 02/01/18) I've got PVC air lines now, am told they are a bomb waiting to happen. Rehabbing my shop, so want to do it right. What say you? I know copper would be great, but need to go about 1 inch diameter and I think I'd have to get a second mortgage to use copper.
Click to expand...
1/2" black iron pipe, if your routing pipe all the way around your shop coshoo and want more air volume go to 3/4". but not pvc. plastic overtime with the vibration of the comprsser running will harden and when it blows will send schrapnel every where.
 
On a side note.

Some of my customers have used PVC for ultra pure water, about once a year they have outages due to broken off fittings. I am not a fan of PVC being used on any supply line, just have seen two many failures due to mechanical stress.
 
I guess every time I blow out the water lines in our cabin and home before heading S I am risking my life! I never go above 60 psi and haven't had a problem in 20 years, I guess I won't worry about it!
 
(quoted from post at 15:53:04 02/01/18) I just looked up copper pricing seems to have come way down, Menards had 3/4 x 10' for 17 bucks.
Click to expand...

Wow, that's way down. Four years ago I ran 150' of 3/4" pex underground in conduit for an air line because copper would have broken the bank.
 
They don't like the galvanized flakes, I always hear black iron pipe.

Copper.

Lot of manufactured aluminum from several manufacturers.

Pex.

Rubber air hose.


Paul
 
I was told my PVC air system was a bomb also. It's been 15 years and it is still working fine. I installed a 3/4" system in my pole building when it went up. The pipe is at the eve(12'). I installed standard flexible air hose for all of the drops down to 5' off the floor. The PVC is anchored every two feet along the entire run. I plumbed air at every post(6 drops). Each of the flexible hoses are anchored to the post as well so you can't tug on the PVC when you are looking for that last inch of hose. I installed a trap to catch water in the system at the air compressor which should catch any oil also. The system is only pressurized when I use it. I will never leave it on over night or if I leave for the day. I have also turned my relief valve down to 120psi. I figure if I can't make it work at 120psi I need to figure something else out. My neighbor is a professional diesel mechanic. He plumbed his shop with PVC at least 10 years before I moved in. The only problem he ever had was driving a nail through the pipe during a dry wall repair. Oh, and he runs his pressure at 130psi. I suppose if my system ever goes "BOOM" I will change it out but until then I will continue to use it.

OTJ
 
As a plumbing contractor we are no longer to use any air pressure to test newly installed pvc waste lines for new construction. The test before was 3 psi. Manufactures of pvc pipe came out with no air pressure to be used in any pvc lines. All plumbing inspectors will fail any job that has air pressure. They will not even come to your job. To many injuries with air pressure. Fyi
 
It's pretty interesting all the bursting pipe and shrapnel stories, especially given the bursting point of even schedule 40 is well over 1000 psi. Lot's of fiction.
 
I used half inch truck air line with push-lok fittings. 175 psi. Easy and fast and can add lines anywhere in just minutes. Bleed the air off and can remove fittings with your fingers. Fittings are pricey but need no tools except a pair of cutters to cut the line..Had it in for 8 years and not a single problem.
 
Worked at a factory that consumed a great deal of air. Lines were fitted with 4 inch pipe on floor level against the machines mostly. Many feet of this served as supply tank with connectors welded in about every 3 feet. This served individual machines that were a part of the larger production line itself, and powered by a large capacity compressor for each line. House air for heavy work was stored in upright tanks of probably 3000 gallons. I always thought the capacity of the 4 inch pipe would be a good idea in a shop if room was available.
 
We always used black pipe where I worked.
We had a plastic system for a while and
it was a dangerous.
 
We never had a plastic pipe or fitting to burst
but the glues was not compatible with the
compressor oil and it would blow apart at
the joints. This was a 100 HP screw compressor
running about 110 pounds of pressure in a garment
factory.
 
(quoted from post at 21:32:46 02/01/18) It's pretty interesting all the bursting pipe and shrapnel stories, especially given the bursting point of even schedule 40 is well over 1000 psi. Lot's of fiction.
Click to expand...

Believe what you like. I've seen the result. ProMet machining Gresham Or. ~1989 or so.

It has happened enough times that OSHA will fine a company for using it. Even the companies that make PVC pipe tell you to not use it for air. They know it can fail dangerously and do not want the liability.

Lots of folks use it and have never had a problem yet, and some may never and some will. It's all a gamble. In this case it's a hazard that is easy to avoid. IMO kind of dumb not to.
 
That rating is at a set temperature in a lab with brand new pipe. It is not the real world where the pipe is sun weakened where it runs next to the windows or gets hit by a tool or some other object by accident. Steel copper galvanized rubber hose are all much more durable products to use. Compressed air has alot of stored energy in it I would bet that shards of PVC shrapnel are moving pretty fast in the event of a failed fitting or section of pipe.
 
If the pipe size is say 1" steel you are usually able to run a smaller size copper tube. The reason being is that it is very smooth on the inside. This is possible because there is very little friction as apposed to the steel that is rough. Also the time saving of soldering vs threaded joints would be a great saving as well.
 
That is true about the new pipe but the working pressure from a air compressor is a fraction of the bursting pressure rated with a new pipe. Then when a pipe is broken there is not shrapnel flying all over the shop. I've have been within 10' of a pipe break on three occasions and all it did was make a lot of noise. The pipe could have been glued back together if there was an adhesive that would hold with all of the plastic there. It breaks like a pipe broken from freezing water. The pipes breaking is from them being poorly installed. The shops that I worked in would run a pipe down a column and put an elbow on it where they put a coupler. Then the pipe was attached to the column with duct tape or a zip tie. In my own shop I weld a steel plate to an steel elbow and attach that to the column and run PVC from there. I've never had a pipe break in my own shop and some of the pipe dates back to the mid 1980's and some of this pipe has been exposed to the Texas sun for more than a decade.
 
I've never had an issue with oil. In the 1980's I had a compressor that was defective and was blowing oil into the pipe. I replaced the compressor and I'm still using some of the same pipe. I had taken it down and put it up in my own shop.
 
It seems like one person is taking it personally defending what they have.

PVC probably will not have any issues, but it is not a wise choice to install based on industry experience.

Personally, I think that it would not burst due to the pressure, but mechanical stress will make it fail, I have seen this failure many times with liquid, so no experience on the shrapnel.
 
Why don't you look into some of these new plastic pipe products that are meant to carry air. No pvc is rated for air according to OSHA website.
 
(quoted from post at 17:41:48 02/01/18) don't know what would be wrong with pvc, I have 1" that if glued is rated for 350 pounds
Click to expand...

350 pounds of water pressure perhaps. Not 350 pounds of air pressure. They use water for pressure test of tanks for a reason - when it lets go it is not catastrophic, but air is a different matter.
 
I guess the shrapnel I speak of is where the pipe splits the long way of the pipe and the cracks twisting around the pipe. At this time is when the pipe atarts to flop around from the air flying out of it. I'm betting that is not a place to be standing when it happens.
 
Years ago, I worked in a fabrication shop with high pressure equipment. Pumps, valves, and compressors with working pressures of 5,000 psi to over 100,000 psi. One of the things that became apparent after many failures was that the piping was failing prematurely. Failure was not because of the pressure ratings, but from the cyclic nature of compressors. The constant pounding will make even tubing rated at 3 times working pressure had short life. In the course of R&D, it was discovered that a pre-treating procedure known as autofrettage would greatly extend the life of the tubing.
The basic procedure is to pressurize the tubing with a static pressure of over 2 times the expected working pressure. Pressure was held for a length of time and then released. The theory behind this was that over pressuring the tubing would begin to yield the metal. When the pressure was released, the metal was now in a state of compression that countered some of the pressure passing through it in operation.
Unfortunately, this procedure will not work with plastics because they simply do not yield. Plastics will hold pressure up to the point that they burst. The constant cyclic pressure generated by a compressor will fatigue the plastic. Then, it fails due to fatigue rather than from excessive pressure. A pulsing pressure like that generated by a compressor will eventually cause the plastic to fail. Black pipe would be the most reliable while copper may well do the job, but maybe not as reliably. Hard drawn copper tends to get brittle over time and may fail for that reason.
 
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