air lines

[nomadhermet]

OK Guys need some advice. I want to run air lines in the shop for the workbench and tools. I now drag a hose from a wall mounted regulator from one end of the shop to the other. I run 120 psi from the compressor to regulator and never above 90 psi after regulator. I'm both cheap and lazy, has anybody used pvc pipe. The thought of cutting and threading metal pipe for this project seems a waist of time and money if plastic will work.
I've seen metal air line in eastwood that is flexable with connections.Thanks for any help.

[a66toy]

I am using type L copper, it's easy to install but with the price of copper now it could be costly. I've heard, but never seen, that pvc weakens and can rupture after a while from the expansion and contraction from pressure but I see it used in a lot of home shops. It's a pain dragging hoses around coiling then back up isn't it, thats why I piped mine.

[rbryce1]

Deleted this post, see my next post!!!!!

[rbryce1]

On the other hand, I also just found this site, which makes me change my mind. In the event the PVC does fail, it would be 1) catestrophic 2) throwing high speed pieces of plastic everywhere that could be dangerous or even fatal if struck by, 3) fail without any indication and 4) would have an incredible amount of reserve energy in the stored gas (air) in the system. This is totally different than a low pressure metal pipe failure which will crack but not explode, and even more dangerous because the fluid is a gas, not a liquid, which PVC was designed and rated for.

http://www.woodweb.com/knowledge_base/C ... ystem.html

I was an Engineer in the Navy, and I have seen photos of high pressure air system ruptures and they were not pretty. These were 4500 psi stainless steel air systems, which is not much different in comparison to 150 psi of pressure in a PVC systems. The strengths we are talking here are proportional, but the results would be the same.

This is also why PVC is not allowed by OSHA for any gas system.

Many articles also indicate the metal fittings threaded into PVC connections fail as well due to inadvertant overtightening of the connection, as it is very hard to "feel" the tightening of metal in PVC, and most often, the connection is over tightened and results in either cracks or cracks waiting to break later. Should this threaded air fitting fail without a hose on it, it would become a very high speed missle, just like a bullet, capable of severely damaging something or hurting someone or even killing someone.

Since I am looking at a cost of about $200 for a metal system compared to $75 for a PVC system, it just doesn't seem woth the possible problems.

[vito]

On the other hand, I also just found this site, which makes me change my mind. In the event the PVC does fail, it would be 1) catestrophic 2) throwing high speed pieces of plastic everywhere that could be dangerous or even fatal if struck by, 3) fail without any indication and 4) would have an incredible amount of reserve energy in the stored gas (air) in the system. This is totally different than a low pressure metal pipe failure which will crack but not explode, and even more dangerous because the fluid is a gas, not a liquid, which PVC was designed and rated for.

http://www.woodweb.com/knowledge_base/C ... ystem.html

I was an Engineer in the Navy, and I have seen photos of high pressure air system ruptures and they were not pretty. These were 4500 psi stainless steel air systems, which is not much different in comparison to 150 psi of pressure in a PVC systems. The strengths we are talking here are proportional, but the results would be the same.

This is also why PVC is not allowed by OSHA for any gas system.

Many articles also indicate the metal fittings threaded into PVC connections fail as well due to inadvertant overtightening of the connection, as it is very hard to "feel" the tightening of metal in PVC, and most often, the connection is over tightened and results in either cracks or cracks waiting to break later. Should this threaded air fitting fail without a hose on it, it would become a very high speed missle, just like a bullet, capable of severely damaging something or hurting someone or even killing someone.

Since I am looking at a cost of about $200 for a metal system compared to $75 for a PVC system, it just doesn't seem woth the possible problems.

Not worth it. Times like this is think of the safety aspect.

[MaineVette]

Do the lines need to be rigid? Why not buy a bunch of rubber hoses and clamp them in place or fish them through the wall studs. It might not be as neat as iron pipe, but it would do the trick and would be pretty cheap.

[rbryce1]

Do the lines need to be rigid? Why not buy a bunch of rubber hoses and clamp them in place or fish them through the wall studs. It might not be as neat as iron pipe, but it would do the trick and would be pretty cheap.

That is what I am doing rignt now. Don't really have any problems with this method, except the hose costs you some pressure at the end of the line due to the expandability of the hose itself. Just have to set the primary regulator higher, that's all. In my case, I am doing this with the sand blasting cabinet, and it doesn't matter because I find the cabinet works best at around 55-60 psi of air pressure. Below or above that, it doesn't blast near as well. So I have a regulator at the cabinet and it reduces the line pressure down for just the cabinet.

[nomadhermet]

Thanks for the ideas Guys, The price of copper is crazy,your right TOY. I have triped over the air line and have draped the dirty hose over the boat the last times. RB "Very high speed missle" That makes pvc out i still have a $100 emergancy room deductible, your right VITO not worth it,
I"m going to try part black pipe and a rapid air kit from eastwood to cover the whole shop.
Checking into this only added more questions; I have seen air guages that are liquid filled. Is this needed on a home shop? and why the liquid. RB on the site you posted they talked about a home run line to complete the system. I think they mean not to dead end but return back to supply if that is true where is the return to, before regulator,a second regulator. I think that would let air to supply the tool from both directions,helping volume.not sure. Thanks for the help GUYS.

[vito]

nomad

try calling a HVAC or plumbing shops and ask if they have any old pipe lying around. or some place that is going out of business. when I worked in the shop we always had old stuff lying around.

liquid filled guages. If I remember correctly, they are used for the pulsations that are in the system, typically higher pressures then what you are working with. If me, I would not pay extra for them.

rbryce1 can probably explain this better.

Cheers

vito

[rbryce1]

Liquid Filled Gauges are normally used on compressors, presses, pumps, motors, winches, etc where vibration and pulsation is present. Standard auto gauges (inside the car) are not liquid filled and are good enough for daily use. Gauges in high-performance, heavy use vehicles or equipment that vibrates a great deal are often filled with certain liquids to reduce shock and enhance accuracy.

You may consider liquid filled gauges if they are mounted directly on the compressor, as you will not see any needle vibration, but you most likely do not need them on a wall mounted regulator which is connected to the compressor with an air hose. I have my master regulator on the compressor. It is not liquid filled and reads fine while the compressor is not running, but vibrates somewhat when it is running. From there, the air travels through a short hose to my master manifold and down stream regulators which are mounted on the garage wall. These are steady all the time.

As far as the "Home Run", I could not find where the article referenced that, but it most likely means if you have a large shop and desire to run the air line all the way around the shop, it will work best if it is a loop rather than a dead end. An event called head-loss in piping systems costs pressure over long runs due to friction and resistance to flow. A very long run will have lower pressures and reduced air capacity at the end than at the source. A loop would prevent this by cutting the distance air needs to travel to the connection in half. Just depends on how big your shop is. A single car garage would not see this. A two car may be enough to see some pressure losses and anything over 2 cars I would install the loop.

Hope this helps.