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JeffKranz
03-19-2009, 07:25 PM
About 10 years ago, I build my shop and decided to use PVC air lines. I had one friend on this board that has had them for years with no problems and another friend who is a pipe fitter and kept sending me internet articles on disasters of PVC Air Lines. I must tell you that my shop has 18 drops that are about 9 feet down each wall and the entire shop 30 x 64 three rooms cost just over $100 to plumb in PVC. All of the rooms have the lines in the wall with either 7/16 OSB or drywall that is on the wall which I thought should prove to be a protective barrier between the lines and humans. I also created a mold at work and make some special flanges that terminated the fittings through the wall and these wrap around the PVC line where it connects to the air line disconnect. This add plenty of strength to this connection.

Here is what is looks like going though the wall
http://i422.photobucket.com/albums/pp304/woodzy9370/pvcline-hose.jpg


It as been 10 years and I have not had one failure but I do have a couple of questions:

I leave this air system on 24-7 but since I only get to the shop every 3-4 days. I am concerned if a line either PVC or hose, were to rupture, what could happened if the compressor ran 24-7? I thought of turning off the compressor when I leave but I thought the constant pressure / no pressure would cause more problems then the occasional re-charge of the compressor

Question #1 Is it OK to turn off the system and let the air line system compress then uncompress?

Question #2 If it is better to leave on all the time, is there some type of circuit that I could add to the compressor that if it sees requires power for like 30 minutes it will disconnect the power until a reset button is re-set?

I know I probably will get some bashing about using PVC air lines but the ship has sailed and if I had to do it again, I would probably plumb with copper or Iron pipe.

Thanks,

Jeff

Errol Groff
03-19-2009, 07:32 PM
I won't make any comment on the compressor on/off question or about using PVC for your plumbing.

What I can comment on is your question about the compressor seeing low pressure and how to shut it off in case of a rupture. I used to have on my well tank (deep well with pump at the bottom of a 350' deep hole) a "low pressure cut off" switch. This device would cut off power to the pump if pressure dropped below a certain point. If there was a leak or other diasaster and the well pumped dry it would shut off the pump before damage would occur.

Perhaps there is a similar switch to cover your situation.

chrsbrbnk
03-19-2009, 07:33 PM
we had a gardner denver 35hp had a safety valve fail it ran most of the week end it toasted it had to rebore the cylinders

dp
03-19-2009, 07:58 PM
You can wire a special thermostat to the starter/contactor to shut the compressor off if there's an over-temperature condition.

http://www.thermostats-china.com/overload_protector.htm

Lloyd H
03-19-2009, 08:25 PM
I wired a relay from shop lights, lights off, compressor can't run, lights on and a push button at the light switch has to be pushed to latch safety relay on. I also learned hard way, hose ruptured and run all night, when I opened in the morning smoke was so bad I thought the shop was on fire. thankfully the compressor survived but took a couple weeks to work the carbon off the valves and restore output.

Bill Pace
03-19-2009, 08:41 PM
Dont have any answers, just my experience ---

My 80 gal 2 stage set at 130psi stays on 24/7 and has for some 15 years (if I leave on vacation/trip I shut off) and the shop is plumbed with schedule 80 PVC with some 15-18 drops and conventional fittings. I have never had a break or blow out -- or ANY kind of problem.

radkins
03-19-2009, 08:53 PM
I WILL comment on the PVC, you sir have a bomb just waiting to go off! I know one fellow who lost his right eye and another escaped injury only because he had left the shop for a few minutes. The fact yours is ten years old makes it far more likely to rupture and just because you have gotten away with it for ten years does not mean it will last another ten minutes. PVC does become more brittle and prone to shattering with time especially if exposed to sunlight, also as the temperature rises the pressure rating of the stuff drops dramatically. The problem with these systems is not just the person willing to take the risk but all too often it happens to someone who has no idea of the danger he is in, and make no mistake it is VERY dangerous! When those pipes rupture, and there are a great many cases of it happening, the pipe does not just break in half or spring a leak but rather it ruptures along the length of the pipe and will send razor sharp shards in all directions. There was a case down in Florida a few years ago where a guy received a serious neck injury from a shard that was thrown nearly 50 ft! These pieces truly are razor sharp and as my friend with the eye injury found out these life threatening pieces of PVC will NOT show up on an X-ray! Do yourself and others around you a big favor and replace that stuff before you too become one of these examples, take a good look at it the next time you are in your shop and remember it can happen to you! This stuff really is that dangerous and I am not kidding!

jdunmyer
03-19-2009, 08:57 PM
Jeff,
I plumbed my airlines (all 1/2") with Genova CPVC in 1968 and have never had a problem. Those lines are mostly in the walls, with 3/4" wood covering them, so I feel plenty safe enough.

Here's how to prevent your compressor from running all the time after a line breaks: Wire up a circuit that uses a relay and a second pressure switch that's set for say, 30 PSI. If the pressure is lower than 30 PSI, the compressor won't run. The relay is connected through a pushbutton switch and a NC contact on the pressure switch so as to bypass the pressure switch until the pressure builds up. Turn on the compressor, push the button, and away she goes.

I have to do a bit of thinking on it, but I'm sure I can come up with a circuit for you.

TGTool
03-19-2009, 09:08 PM
Do yourself and others around you a big favor and replace that stuff before you too become one of these examples, take a good look at it the next time you are in your shop and remember it can happen to you!

It seems to me the OP has already admitted he'd do it differently if he had it to do today. And that the liabilities he now recognizes are mitigated to a large extent by having the plumbing enclosed in the walls providing a scatter shield of sorts. Which of course also raises the cost of replacing the entire system as you recommend. I don't hear anyone offering to help do the work or defray the cost of the action so urgently advocated.

tdkkart
03-20-2009, 02:42 AM
I wired a relay from shop lights, lights off, compressor can't run, lights on and a push button at the light switch has to be pushed to latch safety relay on.


As soon as I get a new pump for my big compressor, and get my new shop wired, this is the way I intend to do mine as well.
Seems to make perfect sense to me, lights out no compressor, no problems.

BadDog
03-20-2009, 03:30 AM
I wouldn't even consider a relay on the shop lights. A few days away from the shop, and even a tiny leak on some random fitting/connect and it leaves you with a dry tank that has to pump up from empty. Not only waiting when you need it for just a quick job, but listening to the racket (pity those with oil less!), but you get far more heat stress on the motor/compressor, particularly when the shop is at 120 ambient.

Mine has a 1" nipple into a well sealed large Teflon lined ball valve right off the tank. Quick quarter turn, and the whole system is dead for maintenance or whatever. I turn it off every time I finish using it. You can easily ease up the pressure as well. Hook a pressure switch on the down stream side to a small light so you don't forget to cut it off, and no worry, no risk, plus easy service when the inevitable leak or quick connect needs fixing...

John Stevenson
03-20-2009, 05:08 AM
Russ,
What suits one won't always suit everyone.
I also have a tap on the end of the compressor but my compressors are up in the hay loft out of the way.
That means a ladder, rope round the chest and a trail of breadcrumbs to get to the tank.

My stop start switch through is remote and situated against the door so it's not hard to switch off at night as I leave.

spkrman15
03-20-2009, 07:38 AM
Jeff,

You can get a low pressure cut off switch. They are easy to find and not that expensive. I would use one made for a water pump such as was mentioned above.

A contactor to shut off and star-up your compressor is a great idea. If you leave the lights on the compressor could run all night, or all day, etc.

Being a little environmental, why not shut it off when you are not in the shop? If you are worried about leak down then shut off the tank from the remote lines. (Even that is not a guarantee, drains, etc leak). Save the electricity and the wear on the machine. Most compressors pump up in 10 mins max! Aren't we supposed to drain the tank daily? (hehe)

I also think the point about the lines getting brittle is true. Keep it in mind. Your install is amazinly neat and i love it. Great work. Is the rest of your shop that neat?

Rob :)

ahidley
03-20-2009, 08:04 AM
Another supper simple option is to place a ball valve right after your tank and turn it off when you leave. The draw back is you have to remember to do it when you leave.

To make that option automatic you could put a solonoid valve right after the tank and wire it to your shop lights.

Both options will leave the lines pressurized, assuming no leaks :) and the compressor on.

JeffKranz
03-20-2009, 09:59 AM
Thanks for all the comments but my concern of turning if off when I leave - will the constant pressurize / depressurize better or worst then just leaving it on thinking about expand and contract of the PVC. I already had it wired to hook to the lights and the alarm system so you could not set the alarm if the lights are on and the compressor is live. The dust collector in the wood shop had a remote that is only powered when the lights are on so it cant just start up while Im not there.

Andy I also thought of a solenoid valve at the compressor but I know that there are leaks and the compress probably cycles every 8-10 hours while no one is using it due to all the leaks the system either at the pipe joints, air hoses, or connection such as air guns.

Carld
03-20-2009, 10:01 AM
I have been watching this and I guess I have to say I have 1" PVC now since 1991. I leave my compressor on but turn off the air at the tank. If I am going away for more than a day I shut the compressor off. My check valve leaks off some so I leave it on so I have air the next morning without the comp running a long time.

ahidley
03-20-2009, 10:26 AM
I dont think that the on / off cycling of pressure is an issue. What would be a problem is a shock in pressure, i.e. rapid rise, especially when its freezing. The compressor building back up is not an issue.

Everything with age gets older and creakier....................

radkins
03-20-2009, 10:27 AM
You guys can shoot the messenger if you like but ever since Carl (my buddy who lost his eye) had his accident I try to pass on this warning every chance I get. Less than 6 months after that incident came the accident at an auto body/paint shop less than 5 miles from where I live that could have been really nasty but the fellow had stepped outside to talk to a customer. The first accident involved PVC that had been in use about 6 years but I don't know for sure how old it was in the body shop. These incidents along with many others that have been reported should make it obvious just how dangerous using this stuff is and the longer it has been installed the more likely it is to fail. Carl had just started to drain the water from a trap when his let go and his compressor had not even been switched on yet, he knew about the dangers of PVC but decided to use it anyway. He saved a few dollars but it cost him an eye and there have been many others around the country who have been injured as bad or worse. This stuff is VERY dangerous and it can happen to you! Fellows I am not trying to be a horse's arse but I have seen what PVC can do and I think if anyone using it could actually see first hand just what it can and will do and just how easily this can happen they would not even consider going near PVC under pressure!

Liger Zero
03-20-2009, 10:32 AM
The mechanism by which PVC fails is the loss of plasticizers in the resin. As they degrade/migrate the material becomes more and more brittle.

UV exposure (think florescent lighting) and solvent exposure accelerate the process.

It's not a matter of IF but WHEN, and I'll stand my ground on that (as a plastic expert) to anyone, even the fool that'll chime in that he's running 20 year old PVC without issues.

derekm
03-20-2009, 10:57 AM
The mechanism by which PVC fails is the loss of plasticizers in the resin. As they degrade/migrate the material becomes more and more brittle.

UV exposure (think florescent lighting) and solvent exposure accelerate the process.

It's not a matter of IF but WHEN, and I'll stand my ground on that (as a plastic expert) to anyone, even the fool that'll chime in that he's running 20 year old PVC without issues.

As a plastics expert - how does this contrast with PEX? (cross linked polyethylene)

Liger Zero
03-20-2009, 11:04 AM
I've never heard of or seen PEX used in this application, so I can't really offer an opinion. :) I don't want to offer assumptions based on material property charts and textbook learning and have you lose an eye. PVC on the other hand, every so often it makes the news or you hear from a friend of a friend. Plus, the migration of and destruction of plasticizers was one of the things I studyed in detail Way Back When.

One thing to remember is most PE materials while very solvent and impact resistant... become brittle at low temps. So if your shop drops below 60F in the winter you might not want to risk it.

Metal pipe for airline is a known and controllable factor. That's your best bet.

radkins
03-20-2009, 11:07 AM
I think the biggest problem is that most people simply have no idea just how violently PVC ruptures. It was mind boggling to see just how much damage the 1" I.D. PVC did in that body shop and I truly wish I had of taken pictures of all the razor sharp shards sticking out of the vinyl seat of a truck and various other items in the shop, those fragments were strewn through the shop like shrapnel from a grenade and were impaled in almost everything they hit. With the other incident (fellow who was draining the air line), in addition to his most serious injury, there were multiple injuries to his hand and arm that required surgery just to find the PVC shards because the X-ray was useless in finding them. If one of those PVC line systems decides to let go then a compressor running freely just may be the least of the worries!

winchman
03-20-2009, 11:16 AM
Think of your present PVC system as a temporary installation to see if you had the drops in all the right places. If that's the case after ten years, it's time to do a permanent installation using the right stuff.

You've gotten a great return on your investment in the PVC for the trial run. It's time to cash in and savor your good luck.

Roger

radkins
03-20-2009, 11:18 AM
Metal pipe for airline is a known and controllable factor. That's your best bet.


There is a heck of a lot more wisdom in that statement than just safety. :)


There is another problem with PVC that makes it an extremely poor choice for air line even if it could be used safely, which it can't. The problem is water in the lines (and your tools!). For the same reason that a water separator mounted at the tank is almost useless PVC will contribute greatly to the moisture problem. It does this because it is a very poor conductor of heat so by the time it delivers the air to the separator (which needs to be at least 25 ft but much better at 50 ft from the tank) the air will still be hot and the moisture will still be in vapor form so it will pass right through a separator. This is why Copper line is preferred for air lines, not only is it safe to use but it dissipates heat really well allowing the water vapor to condense into liquid so that it can collect in the system drops and the separator. I would think PEX would have this same problem but since PEX is so expensive why would anyone even consider it?

Liger Zero
03-20-2009, 11:22 AM
Plus consider water + plastic = chemical changes in the resin at elevated temps. In extreme cases the water can actually accelerate the failure.

Nylon is the WORST when it comes to water absorption, that's why I cringe when I see nylon tube used in automation applications.

derekm
03-20-2009, 11:43 AM
I've never heard of or seen PEX used in this application, so I can't really offer an opinion. :) I don't want to offer assumptions based on material property charts and textbook learning and have you lose an eye. PVC on the other hand, every so often it makes the news or you hear from a friend of a friend. Plus, the migration of and destruction of plasticizers was one of the things I studyed in detail Way Back When.

One thing to remember is most PE materials while very solvent and impact resistant... become brittle at low temps. So if your shop drops below 60F in the winter you might not want to risk it.

Metal pipe for airline is a known and controllable factor. That's your best bet.
I'm using PEX for compressed air in my shop where I'm not using copper. This PEX is rated from 0C to 20C at 12 bar = 180psi... All PEX runs are inside PVC opaque conduit.

Liger Zero
03-20-2009, 11:45 AM
So more or less you made your own "double wall" pipe. PEX/PVC.

Interesting.

How old is the PEX?

A.K. Boomer
03-20-2009, 11:52 AM
Question #1 – Is it OK to turn off the system and let the air line system compress then uncompress?


Jeff



Sounds like you have a leak or small bleedown somewhere? If your going to turn it off then id fix that, I would not let the system decompress and compress daily --- it will weaken the pipe,
What size pipe do you have? thats a biggie, what pressure do you use? thats another biggie,
Not to ignore Radkins advice - he's had it hit close to him and you have to respect him for the warnings and when you get right down to it he's really right, But we all seem to push it a little and see what we can get away with.

you having 7/16" OSB is of no concern - even if you have 1" @ 175psi your not going to rip through that with plastic particles,

I dont even think it would have the mass capable of ripping through your drywall (but i wouldnt want to use my face as a testing ground) esp. if your running more moderate pressures and perhaps a smaller pipe -- the way your pipe is stubbed through the wall is beyond safe, im not saying its incapable of failure - (it actually looks a little vulnerable hanging out like that) its just that you have that massive hex and the threaded part would just break away - not blow into a million pieces, its the uniform thin wall pipe that is the worry --- due to it being all about the same strength it will disintegrate into many many pieces.
There is no doubt that this stuff can cause major injury - but its mostly due to its extremely high velocity and not its "knockdown" power -- anything inbetween you and it that has any kind of strength at all will take away most of its threat --- yours does not see the light of day or any solvents or such. But - its up to you, one of the biggest tragedy's that we face are the ones that can be prevented.
I have a 150 psi that runs in plastic from the garage to my basement - its only for the air gun and the mister so its only 1/2 inch and has a higher rating because of it, im fairly protected by the mill as the line is less than a foot exposed and hidden behind it and for the most part i have my safety glasses on when im down there - there are two other exposed sections - one is where it leaves my garage for about a foot vertical - its UV exposed and im using it as my canary in the coal mine - the other is in the basement where the dogs hang out but its on the ceiling and their on the floor and 95% of the time when their down there they have their eyes closed, the temperature is very stable down there.
I just got to keep reminding myself not to catch that vert. one out at the garage with the weed eater anymore, that really is my biggest fear.

BadDog
03-20-2009, 12:30 PM
Russ,
What suits one won't always suit everyone.
I also have a tap on the end of the compressor but my compressors are up in the hay loft out of the way.
I absolutely agree. I didn't mean that to come off as if I thought anyone who did so was playing with less than a full deck. :D Just that I wouldn't for the reasons listed. In your case, I would probably make a secure/strong/leak and rupture-free drop straight down the closest wall and put a ball valve there. And I've pondered moving mine out of the shop to liberate room, lower noise, and reduce heat. If I did so, the ball valve would be just inside the wall where the line comes through. At least that isolates it from most leak sources, and then the relay could turn it off without leaving it to drain or keeping the entire system pressurized.

derekm
03-20-2009, 12:51 PM
So more or less you made your own "double wall" pipe. PEX/PVC.

Interesting.

How old is the PEX?
A couple of years- The conduit is make the runs easier to support and fix (PEX is off a coil and is real hard to keep straight) and keep the U.V off the PEX where the run goes outside. My compressor is only rated to 10 bar (150psi) Btw I'm also using PEX to run the water soluble coolant (low pressure) in the shop.

madman
03-20-2009, 03:29 PM
I just plumbed 200 feet of 1.250 dia black pipe and w hose reels with 50 feet air line each. Also a nitrogen air generator system and a air dryer. I just followed the Devilbiss recomendations for such a system and they recomended black pipe, the one and a quarter inch diameter size due to the length of the pipe used and the 4 hose reels also. NOW after this system has run for a while all seems OK, It has lots of pressure anywhere and also doesnt leak much. It was my first such project and i was surprised at how well it all went together, The threading of the black pipe was a bit boruing but i eventually got a electric threader, Hand or manual threading 1.250 dia pipe by hand sucks after about 10 threads,

Liger Zero
03-20-2009, 03:33 PM
A couple of years- The conduit is make the runs easier to support and fix (PEX is off a coil and is real hard to keep straight) and keep the U.V off the PEX where the run goes outside. My compressor is only rated to 10 bar (150psi) Btw I'm also using PEX to run the water soluble coolant (low pressure) in the shop.

Ah. I use rigid PEX when I make filter-bodies for Crazy Fishtank Woman.

After a quick consult with a friend who knows plastic like I do we *think* PEX is elastic enough and won't embrittle... but we honestly don't know.

If you do accidentally blow a line let us know the circumstances and situation we're curious how this holds up over time.

JeffKranz
03-20-2009, 05:39 PM
Just to clarify - Pipe is 3/4 main trunk 12' high and all the drops are 1/2. Pressure is 125psi.

As I said before, if I had to do it again I would use something other than PVC. I think I probably have a better chance of an injury driving to and from my shop since I am probably not in the shop 100 hours a year and since it is enclosed in the wall. I'm accepting the chance that I will not be harmed and know that everyone of use probably does things that present a risk to our health and welfare. My only reason to post this was to find a way to protect either the compressor in the event of a line failure or to protect the line from pressurize / depressurize.

steverice
03-20-2009, 05:49 PM
I used copper tubing on mine.

Zero failures

jkilroy
03-20-2009, 06:14 PM
I used .5 inch DOT approved nylon air brake tubing. Its nylon lined with some kind of clear liner with what looks like fiberglass braid in it. Plenty of capacity, I ran a double trunk, two loops with several joins. There are actually four .5 lines coming from the compressor to feed the system, plenty of capacity for a 34cfm compressor.

My neighbor, across the street, just went through an OSHA bust on his use of PVC. He had some nasty blowouts but he was lucky, his shop is big (10,000+ sq ft.) and sparsely populated so nobody was around to get hurt. It did cost him a couple of compressor rebuilds however. After the OSHA bust we spent an entire weekend with five guys putting in black pipe, I ran the cutting/threading operation. I am pretty sure I can run one of those Ridgid machines as well as anyone after that.

How do you plan to handle the time when someone else will take over the property? Nobody lives forever. What if the owner after you, or even after that, puts air to the system and takes a pvc shard to the neck? Remove the fittings and mud up the holes to hid the system?

radkins
03-20-2009, 07:18 PM
How do you plan to handle the time when someone else will take over the property? Nobody lives forever. What if the owner after you, or even after that, puts air to the system and takes a pvc shard to the neck?


That's the big problem with the stuff sooner or later it WILL give up and burst then at that point someone is likely to get hurt and it very well may not be the person responsible for installing it. If everyone could see the results of a PVC rupture and see first hand just how dangerous it is when it lets go I doubt we would even be having this discussion, it really is that bad!

wmgeorge
03-20-2009, 09:09 PM
That's the big problem with the stuff sooner or later it WILL give up and burst then at that point someone is likely to get hurt and it very well may not be the person responsible for installing it. If everyone could see the results of a PVC rupture and see first hand just how dangerous it is when it lets go I doubt we would even be having this discussion, it really is that bad!

I have been following this, being in the pipefitting trades for a number of years, the recommended air line is black steel pipe, or copper tubing. PVC is an accident waiting to happen, now now, we know and it has never happened yet ... but someday. Is your life, your grand kids or some one else worth the few bucks you saved? It is against OSHA rules to use PVC for compressed air, has been for many years, because of the documented accidents.

E.T.Jr
03-20-2009, 10:43 PM
What is a better choice?
I planning on plumbing air in my garage. I'm thinkin copper since I see it used at work for air and vacuum. Is there a better choice. Granted PVC would cost less, and my pressures would only be hangin out around the 100psi of a normal homeowner type compressor.:confused:

radkins
03-21-2009, 12:04 AM
Copper is the overall best choice because of it's cooling properties which makes removing the moisture from the air easier, plus for most people it is easier to install.

ckelloug
03-21-2009, 12:13 AM
Hi all,

I googled around and I found this video. It shows PVC pipe is pretty tough. It also shows that when it does go off, it goes off like a fragmentation grenade. I'd add that although the PVC seems pretty strong until they get it cold, scratches, chemical degradation from age and other factors could make a big difference in the toughness of something other than the brand new piece they are testing.
See the blastbox video in the first post of this thread:
http://www.crazybuilders.com/forum/showthread.php?p=29

John Stevenson
03-21-2009, 06:35 AM
Over here we can get 'plastic' pipe specially for air lines.
I say 'plastic' as I don't know the spec but this is sold FOR air lines.

It's used in quite demanding applications, I have been on North Sea oil rigs where this stuff is piped round at about 4" diameter.

So is this the same stuff that explodes ? or are you talking about ordinary plumbing pipe ?

I got my 'new' rotary compressor back from the air tool / compressor people just up the road last week after having it checked and serviced.
I noticed that their racks which used to be stacked full of steel galvanised piping, our usual industry standard and what my shop is piped with [ only because the scrappy had miles of it ] is now full with this plastic.
Only a few lengths of steel remain, probably for repair work ?

.

Dawai
03-21-2009, 07:28 AM
Let me tell you a story about a man named JED, poor mountaineer barely kept his family fed..

Okay.. lets talk about danger.. My buddy went to sleep in his bedroom AWOKE to seeing stars, scalded all over.. the pressure vent on his water heater failed, then the thermostat failed.. Instant steam boiler with no release.. when the waterheater finally burst, it took off skyward, taking down the ceiling and roof, spraying Bigfoot (his nickname) with steam as it flew out into the yard.

To be safe, all you worry warts need to remove the hot water heater from your houses, it may be hooked to pvc pipe too. Take cold showers, it is good for the green earth and gives you a vibrant feeling akin to jumping into a snowbank.

There is Air line pvc all over the plants in Dalton Ga. Mostly cause the maintenance men are lazy SOB's and they change the machines around every six months.

A.K. Boomer
03-21-2009, 07:53 AM
I have been following this, being in the pipefitting trades for a number of years, the recommended air line is black steel pipe, or copper tubing. PVC is an accident waiting to happen, now now, we know and it has never happened yet ... but someday. Is your life, your grand kids or some one else worth the few bucks you saved? It is against OSHA rules to use PVC for compressed air, has been for many years, because of the documented accidents.


Personally --- i live alone -- I have to admit I get a little thrill when I have to pass by that one section in the basement -- I feel the hair stand up on the back of my neck, I cross my fingers and my steps become more and more abrupt -- when the thrill starts to wear off sometimes I'll go out to the garage and look above the compressor at the head gaskets I removed to get the compression ratio up (I live at altitude) and then I'll go over and look at the pressure switch regulator screw and how its almost at its highest limit, A quick look at the pressure gauge thats in the red and then Im ready to go back downstairs and hang out directly below the pipe and count to ten:eek: When the self endangerment feeling goes away I will then take my dogs food dish down in the basement and feed them right below the pipe while wearing my safety goggles --- I never put both me and them in danger at the same time because I want to be able to see for driving when I have to take them to the vet...

A.K. Boomer
03-21-2009, 08:02 AM
Just to clarify - Pipe is 3/4 main trunk 12' high and all the drops are 1/2. Pressure is 125psi.

As I said before, if I had to do it again I would use something other than PVC. I think I probably have a better chance of an injury driving to and from my shop since I am probably not in the shop 100 hours a year and since it is enclosed in the wall. I'm accepting the chance that I will not be harmed and know that everyone of use probably does things that present a risk to our health and welfare. My only reason to post this was to find a way to protect either the compressor in the event of a line failure or to protect the line from pressurize / depressurize.



I think your situation is very safe Jeff, you may have a fatigue fracture someday tugging on a hose sideways and have the pipe inside the wall torsionally fail but who cares, with that small of pipe and that low of pressure its going nowhere, some of these guys giving you static probably have 120 lb lengths of good quality shoddily hung steel pipes hovering directly above them and their children's noggins:rolleyes:

JCHannum
03-21-2009, 08:13 AM
John; The PVC that is unsafe for compressed air is the normal Schedule 40 or Schedule 80 PVC and CPVC used for water systems. It is usually white or grey. It will eventually fail, especially in the larger sizes. 1/2" & 3/4" seem less prone to failure, but they all will. When it does go, it is not a simple split or leak, but entire sections will shatter like glass. It is this mode of failure that creates the danger.

There are other plastics on the market which are safe to use, and that is probably what you see at your supplier.

John Stevenson
03-21-2009, 08:30 AM
Thanks Jim, that's cleared that up, so why not use the proper stuff given that it's easier to use with the bonded joints, especially in a home shop that lacks a lot of equipment?

I'm OK as I have have pipe threading dies and the riggers pipe vises leftover from life a while ago.
If it wasn't for the fact all my air lines and fitting have come free from the scrappies I probably would have gone the plastic way as well.

One of my customers has moved into new premises and run round in 2-1/2" plastic with 1" drops off to the various machines and assembly benches.
Knowing them and what they do H&S would have had a big say in what went where.

.

radkins
03-21-2009, 09:15 AM
Let me tell you a story about a man named JED, poor mountaineer barely kept his family fed..

Okay.. lets talk about danger.. My buddy went to sleep in his bedroom AWOKE to seeing stars, scalded all over.. the pressure vent on his water heater failed, then the thermostat failed.. Instant steam boiler with no release.. when the waterheater finally burst, it took off skyward, taking down the ceiling and roof, spraying Bigfoot (his nickname) with steam as it flew out into the yard.

To be safe, all you worry warts need to remove the hot water heater from your houses, it may be hooked to pvc pipe too. Take cold showers, it is good for the green earth and gives you a vibrant feeling akin to jumping into a snowbank.

There is Air line pvc all over the plants in Dalton Ga. Mostly cause the maintenance men are lazy SOB's and they change the machines around every six months.



Belittling the situation does not lesson the dangers and these "worry warts" are simply warning people of a very real danger. Using PVC for air line is many times more of a hazard than a hot water heater and your comparison, although I realize is satire, is comparing apples to Oranges. As far as PVC air lines being "all over the place in Dalton Ga." PVC has been banned for many years by OSHA (unless it is run inside an approved conduit) and it is very simply against federal law to do so in any work place covered by OSHA rules. It was banned for a darn good reason but some people will continue to use it (in private shops) and there will continue to be accidents resulting from it. This really is no joking matter!

moe1942
03-21-2009, 10:19 AM
My PVC air lines are only 26 years old. Should last for awhile longer..3/4" rated to 480 PSI.

radkins
03-21-2009, 10:46 AM
My PVC air lines are only 26 years old. Should last for awhile longer..3/4" rated to 480 PSI.


Most systems don't last as long as that but just because yours has been around that long does not make it safe, it in fact is less safe the older it gets. If you guys want to take a chance with that stuff that is your arse but please use a little common sense here and DON'T try and convince someone else it is OK when the statistics clearly show otherwise. Continuing to use something as dangerous as this is reckless at best but to try to convince someone else it is alright is jut being plain irresponsible!

Liger Zero
03-21-2009, 10:56 AM
Most systems don't last as long as that but just because yours has been around that long does not make it safe, it in fact is less safe the older it gets. If you guys want to take a chance with that stuff that is your arse but please use a little common sense here and DON'T try and convince someone else it is OK when the statistics clearly show otherwise. Continuing to use something as dangerous as this is reckless at best but to try to convince someone else it is alright is jut being plain irresponsible!

As I predicted up-thread the "20+ year" clown has arrived. :rolleyes: Radkins speaks the truth, as this stuff ages it becomes more and more brittle. Just because it hasn't happened yet doesn't mean it wont.


But hey, we've done our part... the warning is out there. Good luck Moe1942! I'll just sit here and put my safety-goggles on. :cool:



...and on a final note many many companies thumb their nose at OSHA regs (such as PVC airline) and then play bat**** dumb when something goes wrong and then get off with a slap on the wrist. It's one of my biggest pet peeves with our health and safety system in this country.

ptjw7uk
03-21-2009, 10:59 AM
Suggest you read this :-http://www.osha.gov/dts/hib/hib_data/hib19880520.html

peter

radkins
03-21-2009, 12:22 PM
Suggest you read this :-http://www.osha.gov/dts/hib/hib_data/hib19880520.html

peter


At the time that was printed OSHA had yet to make a firm ruling but after that little incident hit the wires reports of other incidents started pouring in and that's when they took action. That is the way it was explained to us by an MSHA inspector after he had written a citation for improper airline plumbing at the mine where I was working at the time. The citation was not for the use of PVC (it was all black iron) but for improper placement of a line where it could have been easily damaged. The conversation got off on the use of PVC and he had some really "hair raising" stories about accidents resulting from it's use both in commercial and private use. MSHA banned the use of PVC about the same time as OSHA and for the same reasons, PVC can still be used for air and gas transportation if it is buried to a specified depth or run inside of approved metal conduit.


These accidents are so common and the hazards are so well known I just can not for the life of me understand how anyone could ignore the dangers? :confused:

Liger Zero
03-21-2009, 12:24 PM
These accidents are so common and the hazards are so well known I just can not for the life of me understand how anyone could ignore the dangers? :confused:

'cause it's inexpensive and because they have XX years of wisdom and experience and seniority so therefore it can't happen to them. :)

radkins
03-21-2009, 01:09 PM
'cause it's inexpensive and because they have XX years of wisdom and experience and seniority so therefore it can't happen to them. :)


Until it does! :rolleyes:

Liger Zero
03-21-2009, 01:12 PM
Until it does! :rolleyes:

Well see then it's someone else's fault.

Like the new guy, or the person who has his/her hand on the air-valve, or the guy who installed it, or the hardware store for selling shoddy pipe.

The sort of person who can't accept the advice that something is dangerous (unjacketed PVC airlines) after reading it online and seeing a government report isn't the sort of fellow who will take responsibility when it does let go.

:)

A.K. Boomer
03-21-2009, 01:36 PM
Mine are CPVC -- they are less apt to fracture but im told when they do they have Howlitzer like performance... :p I looked for the a.b.s but they did not have any 1/2":o -----------:(

ABS is safe right?

radkins
03-21-2009, 01:49 PM
Mine are CPVC -- they are less apt to fracture but im told when they do they have Howlitzer like performance... :p I looked for the a.b.s but they did not have any 1/2":o -----------:(

ABS is safe right?


Copper, galvanized iron and black iron are safe, just the water problem alone is enough not to use plastic!

radkins
03-21-2009, 01:54 PM
ABS is safe right?

If you always do what you've always done
you will always get what you've always gotten.



And if you continue to do what you've always done'
It will eventually catch up to you! :D

John Stevenson
03-21-2009, 03:40 PM
Copper, galvanized iron and black iron are safe, just the water problem alone is enough not to use plastic!

So what makes black iron impervious to water ?

.

radkins
03-21-2009, 03:58 PM
So what makes black iron impervious to water ?

.



Metal pipe will dissipate heat allowing the air to cool and the water vapor to condense into liquid so that it is more easily removed, in this respect Copper is even better. PVC on the other hand will insulate the air inside so it will remain hotter over a greater distance leaving the moisture in a vapor form that will not collect in the collection drops/traps and will tend to pass right through the water separator. It then will cool as it enters and expands inside the tool being used at which time the vapor will condense into liquid inside the tool. The bottom line is that PVC will contribute a lot to having moisture in the air lines.


For this same reason (hot air), regardless of the type of pipe used, a water separator located right at the tank will do next to nothing to dry the air and the moisture will tend to pass right through. The air can be very hot as it exits the tank and should be passed through several feet of metal pipe (about 50 ft if possible) before it enters the water separator.

jdunmyer
03-21-2009, 06:56 PM
As my compressor is 3-phase and uses a magnetic starter, I wired up a small toggle switch mounted in a Hoffman box next to the shop door. Directly adjacent to the switch is a regular industrial Amber pilot light that's quite bright. It's hard to miss that light when I'm leaving the shop. Of course, it'd be easy to connect a relay contact in series with the switch, as the relay for the lights is already in that box. Dunno if it has an extra contact, though.

gearedloco
03-21-2009, 08:09 PM
There is one issue that hasn't been raised. In the "bang box" (or whatever it was called) the pipe did ok until they tried it on a very cold piece.

Consider this - you've got this length of pipe and due to some reason such as a bump, or maybe a bad glue job at a fitting, a pin-hole leak develops. The escaping and rapidly expanding gas will get _very_ cold. That will, as demonstrated, make it weaker and brittle. BANG!

So even if it's full of hot air, a pin-hole will very quickly make the section of pipe around the leak _very_ cold. And a very cold plastic pipe filled with air at even moderate pressure is not a good thing.

It may be fun to bash OSHA for various things, but IMHO there are good reasons for the large majority of their rules. Those rules may "not apply" to home shops, but the laws of physics apply everywhere and are non-forgiving.

-bill

A.K. Boomer
03-21-2009, 08:52 PM
And if you continue to do what you've always done'
It will eventually catch up to you! :D


Read post #51, its in that osha link; We do allow the use of certain ABS materials that are specifically designed for compressed air systems. One such product is "Duraplus" air line piping system ABS pipe. However, as in any such system, the manufacturer's specifications on acceptable pressure and temperature considerations must be followed.

radkins
03-21-2009, 09:26 PM
Read post #51, its in that osha link; We do allow the use of certain ABS materials that are specifically designed for compressed air systems. One such product is "Duraplus" air line piping system ABS pipe. However, as in any such system, the manufacturer's specifications on acceptable pressure and temperature considerations must be followed.


ABS may very well be OK or at least the ABS specifically designed for air lines, I have no idea how it would act in a bursting situation but I doubt it would shatter like PVC. Whether ABS is safe or not is totally beside the point however since that has nothing to do with using PVC and would in no way make PVC any safer to use. The bottom line is PVC is a known hazard when used as a conduit for pressurized gas including air and there have been many serious accidents resulting from it's use. Pointing to another type of plastic line or at an old PVC system that has managed to beat the odds (so far anyway) in no way lessens the risk of using PVC and anyone who chooses to do so is putting themselves and possibly innocent bystanders at risk. Also as has already been pointed out just the moisture problem alone is more than enough reason to not to use plastic, it really does make that much difference and the few dollars saved now could very well come back to haunt you later.

Jeffw5555
03-21-2009, 09:30 PM
Metal pipe will dissipate heat allowing the air to cool and the water vapor to condense into liquid so that it is more easily removed, in this respect Copper is even better. PVC on the other hand will insulate the air inside so it will remain hotter over a greater distance leaving the moisture in a vapor form that will not collect in the collection drops/traps and will tend to pass right through the water separator. It then will cool as it enters and expands inside the tool being used at which time the vapor will condense into liquid inside the tool. The bottom line is that PVC will contribute a lot to having moisture in the air lines.


For this same reason (hot air), regardless of the type of pipe used, a water separator located right at the tank will do next to nothing to dry the air and the moisture will tend to pass right through. The air can be very hot as it exits the tank and should be passed through several feet of metal pipe (about 50 ft if possible) before it enters the water separator.

This is true, to a degree, but let me refine a statement made above. A water separator at the tank won't do "next to nothing" , it will do "absolutely nothing at all" :) It needs to be used at a point where the air has cooled to the ambient temperature of intended use to be effective.

Regarding the PVC argument, the poster is correct that copper is by far the best for the reasons stated above.

Let me add some additional detail to the points stated above.

Compressed air leaves the compressor hot and at 100% relative humidity. As the air cools, moisture condenses out. (but the air still remains at 100% RH) The main point missing from above is that reducing the air pressure lowers the relative humidity. (i.e. using a regulator) So the ideal strategy for dry air at your tools is to keep your air at high pressure until it is cooled to ambient temp, use a water separator, then use your regulator to drop the working pressure as close to your tools as possible to lower the RH. For this reason, the best way to get dry air is to use a two-stage compressor for higher pressure, a long run of copper pipe at full high pressure to cool the air, then use a separator/filter/regulator system at or very near the point of use to extract dirt, water droplets, and to dry the air by reducing pressure.

You should never use a regulator or water separator at or close to the tank for the reasons above. PVC for piping runs, besides the aforementioned safety issues, is not appropriate to use as it doesn't enable rapid cooling and condensing of the air, at least enough to get it down to ambient temp.

I've seen persons that think they are doing the right thing by having a long run of pipe and a water separator close to point of use, but they screw it up by having the regulator at the tank. Then they have a rubber hose connected to the water separator, and laying on the floor feeding their spray gun, and wonder why they see water droplets coming out of the gun. In this case, the air leaving the regulator at the tank is at near 100% RH, then as it cools in the long run of pipe (usually high in the shop, where it's warmer) it stays at 100% as excess moisture condenses out and is caught by the water separator. However it leaves the water separator still at 100% RH, then it flows through the hose in on the floor, where it's a few degrees cooler than the long run of pipe, which allows moisture to condense out.

Ergo, water drops!

radkins
03-22-2009, 06:22 AM
Exactly what I was trying to say but you said it at least 10X better and made it a lot easier to understand! :)

Shaidorsai
03-22-2009, 10:08 PM
One scenario to expose two real risks. Ever seen a small fire fed by compressed air? Any plastic may be a lot of things but fire proof is not one of them. A full tank left online 24/7 might also be considered a supercharger. Shut it off! Outside the Shop! Better yet, drain it every night! Your insurance carrier will not curse you, for it.

radkins
03-23-2009, 08:53 AM
Better yet, drain it every night! .


Draining the air lines every night may be a good idea but not the tank! Draining a tank down to zero pressure on a regular basis will greatly shorten it's service life due to metal fatigue from excess expansion and contraction. A tank will expand and contract some during normal discharge/recharge cycling but nowhere near as much as it would if it was drained down to zero pressure and then recharged. Obviously draining a tank to zero occasionally is not cause for concern and there are many reasons for doing it, occasionally that is, but doing so on a regular basis is a recipe for a cracked tank usually around the welds at the motor/pump mounts or the support legs.

As if the fatigue problem was not enough if you add up the amount of totally wasted time spent recharging the tank daily from empty it would be staggering at how much useless wear and tear it would be getting. Then there is the wasted electricity, etc,,,,