Compressed Air System

My suggestion is to use metal above ground and keep the PVC buried. Don't overpressure the line and watch out for rocks and roots.

My brother has PVC air lines, chest high, throughout his shop. They are 10 years old.

PVC is not a good material for this, but there is another plastic that would work. HDPE (high density polyethylene) is one.

As I understand, oil degrades the PVC. It is comparatively brittle, so if/when it breaks, shards of shrapnel fly everywhere.

High density polyethylene is what you mean, I think. That would certainly work well.

Probably safer, too.

But, I still maintain that PVC underground poses no threat of injury from bursting.

I do concede that your advice is more appropriate than mine, but, that's not the way I'd do it.

I know about the brittleness of PVC, but I would bury it in the ground and connect to metal pipe above ground. My concern is the distance. Would I still have adequate pressure (90PSI)?

The pipe will need to be evaluated for flow rate versus pressure drop over its length. There are some rules of thumb for suitable velocity. For compressible fluids like air, the Colebrook equation is probably the "Cadillac." It is used for relief valve discharge header calculations, and is hairier than what you need.

Use pipe larger then necessary for the amount of air flow needed. The pipe then acts as additional storage for the compressed air. You will though have to look at the specs on pressure of the larger size pipe. As the size increases the max working pressures go down.

Plastics tend to expand under pressure more then metal pipes. If you just use pipe large enough to handle the flow needed then the stress due to quick changes in pressure on PVC may cause it to break. Another reason to use larger pipe. All so take care in burying it the pipe should be surround in a bed of sand. Any sharp object like a stone will wear though quickly even a small one.

i thynk it cost less to buy another for your son then to do this.

NO! NO! NO! DON'T USE PVC PIPE, IT COULD KILL YOU! Not only is it illegal to use in the USA but it is also extremely dangerous! PVC pipe when it breaks forms shards (very sharp irregular pieces that become deadly projectiles) which when combined with the compressible air creates very fast moving, in excess of 100mph, particles that could cause fatal injuries depending upon the shape and where it hits you. This is obviously an extremely dangerous thing.

There is one form of ABS plastic, Acrylonitrile-Butadiene-Styrene , that is approved for compressed air use because it will split, such as copper and steel piping will, when it fails. It does not form particles. See-

http://osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=19714

http://osha.gov/dts/hib/hib_data/hib19880520.html

http://osha.gov/SLTC/compressedgasequipment/recognition.html

War Stories: Several times while I was at a very large horticultural facility where much compressed air was used for manufacturing, packaging and material handling (2ea 50hp screw compressors) I observed PVC compressed air piping fail. The last time a section of 2" Sched 80 PVC failed and blew up. The schards ranged in size from miniscule to one piece approx 20" long with a point on it like a Bowie Knife. I was approx 40 ft away, behind a wall and ended up with a ringing in my ears. There was another guy walking about 10ft away from the failure and ended up with a free ride in an ambulance to the Emergency Room to remove a 3" piece of PVC from his shoulder that had gone 2" into him. There are other such incidents that happened at that facility but too numerous for this forum. I no longer work there for several reasons, foremost the failure of the owner and his brother to follow common sense procedures for the safety of the employees.

The most cost effective resolution to your problem is probably the purchase of another compressor. It also has the advantage of not having to dig or trench for the piping. If you insist on long distance piping copper tubing is your cheapest alternative. Every design of comp air system I have done it has come out the cheapest when material and labor are considered except for mega systems.

Another advantage of the additional compressor is that the cooling effect of the dirt surrounding the buried piping will cause alot of condensation to collect in the piping from the condensation of moisture in the compressed air.

The OP has already stated that he is going to bury his PVC plumbing.

All of the articles you cite clearly refer to "above ground" use of PVC pipe for gas transmission as a problem. "Above ground" use is discouraged.

"I know about the brittleness of PVC, but I would bury it in the ground and connect to metal pipe above ground."

What else did he say?

Illegal to use for air in the United States.

I'll stand by my first statement. There is virtually no risk if the PVC pipe is buried.

OSHA does not, yet, control what one does on one's own property.

I would never recommend using PVC pipe for above ground compressed gas service. I cringe every time I walk into my brother's shop, because, as I said earlier, he's got the stuff plumbed all over right at chest height.

Cheers.

OSHA is involved if you have 8 or more employees and regardless of number of employees, they get involved if someone is killed or 3 or more people end up being hospitalized.

It's better safe then sorry. Anytime someone tries to cut corners to save a dollar is inviting trouble that could have been easily avoided.

It might last for years then one day something happens and it leads back to that PVC pipe. Then it will occur to you that someone, somewhere warned you but you wanted to save a dollar that ended up costing you more then you saved.

You can do what you want. You're asking for advice here and we're giving it to you.

It's your world and we're just living in it.

"You can do what you want. You're asking for advice here and we're giving it to you."

I didn't ask for advice, I gave my opinion to Ronseto.

The words you seem not able to comprehend in your warning are above ground applications.

This is not an "above ground application"!

Ronseto has clearly stated that the PVC will be buried.

Cheers.

And I express to you that the warnings I see concerning PVC for using compressed air or gas does not specify "Above Ground or Below Ground Use."

So Better safe then sorry.

"The Use of Polyvinyl Chloride Pipe in Above Ground Installations. OSHA Hazard Information Bulletin (HIB), (1988, May 20). Describes the hazard when using polyvinyl chloride (PVC) pipe for transporting compressed gases."

"SUBJECT:Safety Hazard Information Bulletin on

the Use of Polyvinyl Chloride (PVC) Pipe in Above ground Installations"

"
November 8, 1988

Mr. Jack Cannova
Tempe Industrial Supply
412 Orion Street
Tempe, AZ 95283

Dear Mr. Cannova:

With regard to the use of plastic pipe for unprotected, above ground gas transmission and distribution piping systems, it is our understanding that only one type of plastic pipe is acceptable for such uses."

These all clearly specify "above ground" .

Cheers.

On Discovery Channel a couple of weeks ago, Myth Busters, they used PVC pipe for compressed air. I wanted to contact them then and recommend some other material, but I forgot. Will contact them this evening.

nooo don't do that, I want to see it go off in that red hair goofs hand.

What's the price of a decent compressor compared to all that work burying pipe and so on... ?

More than a shovel and one's own sweat!

Ronseto,

I have a similar set up at my home in indiana. The main shop and another smaller one about 250yds distance. What I did may also work for U. I plumbed in a heavy schedule (80) over to the smaller shop and buried the pipe about 8 inches (in dirt).

I also installed air tank (reservoir) over at the smaller shop.Once this AUX. tank fills up, it can be used as needed. Because of the distance from the supply (Air comp.) I installed an electric solenoid valve that detects 'massive' leakage and closes the valve. In case of a line bust underground or similar over at the smaller shop, the Air compressor will not suffer trying to keep up with the massive leak!!

Good Luck......

I would suggest that you price up the cost of extending the pipework from one compressor to the other workshop in whatever pipework you want, and the cost of digging a 4ft deep trench, placing over the pipe protective ceramic tiles (would you need planning permission?), sand as the bed for the pipe, backfilling, and all the connections and labour required to make it work for you and then cost the price of a NEW compressor.

How big a compressor do you really need?

And as so many people have stated, better safe than sorry, if PVC or any other type of plastic is not worth the trouble or a life.

However, the final decision is yours.

..and after you solve all the issues already mentioned...when you and your son both need air at the same time you may find that neither of you has enough! Buy a second compressor, you'll save time, money, have plenty of air at both sites and have a spare if needed.

May be useful this experience for you:an engineer used the I.Rand at its maximun pressure (200psi,14kgf/cm2) in along line but the pipe, common galvanized iron 1'' pipe,not the good seamless pipe, the common one cheaper than plastics pipes and...It works when i thought it was going to explode! even with severals outlets.then pressure regulators.May be 3/4'' pipes are the usual in factories, neither so high pressure is needed.Water drain is needed.-

Do not know what type of shop, home, or work, and if IR and $$$ means a screw type compressor $30,000.00+ 100 CFM @ 100PSI or just a large compressor.

Going under ground is OK, but you have to determined the usage as in the amount of air required and quality. If the air needs to be dried/conditioned, because running at that length you will have moisture build up.

Worked at a shipyard, and we always had that problem and if it was shutdown for the holidays, you have to purge the line, it resembled a fire hose that an airline and the quality would be poor for a while. Plus be aware of the frost line if you live in that area.

And if thats the case

My suggestion to you is; It may be just easier/cheaper to purchase a large compressor if its a home shop. one with a Air delivery of 10.2 SCFM @ 40 PSI, 8.5 SCFM @ 90 PSI for $700.00-800.00 or 18.7 SCFM at 100 PSI for $1200.00-1500.00. because if your using air tools like a dynafile that can suck up to 7-12 scfm's, it would be starving if anything smaller.

p911

The compressor I have is an Ingersol-Rand oil lubed piston type. Output is about 10 CFM @ 90PSIG. I don't have a frost problem. I have provision for purging lines of moisture. My usage of air is to drive nails and for blowing out dirt from crevices. My son uses impact wrenches, grinders and other air hungry tools. I'm retired on a fixed income so a new compressor is totally out of the question. Everything I try to do around here has to be on the cheap. That's why I need to go with PVC. I know that PVC is not to be used with compressed air and other gases, but as I mentioned, it will be buried in the ground where failure will not present a hazard.

I see,

1.) can your son help out?

2.) have your tried craigslist? have to be careul you not buying other peoples problems, Ithe few times I used craigs list, never had an issue.

Naturally my son will be the one digging the trench. He has a tractor and we have access to any digging implements we need. The only cost will be for pipe and fittings. If it lasts 10 years, wonderful! At 75, I don't date stamp any new projects.

Just a suggestion, try talking with a couple of local air compressor shops. They frequently rebuild many of the units that they take in as trades or from upgrades. I got a bargain on a 2-stage 5hp unit that way. The shop even threw in a single phase motor instead of the 3-ph one that was on the unit.

Also, if your son has the big cfm requirements, how about putting your unit in his shop and having him buy you a 2hp unit for your occasional use at your location? That should handle shooting nails and a blow gun and give him the volume of air he needs.

Other possible sources could be auctions of defunct gas stations, factories, wood shops, etc. Also keep a good line of communication to those air compressor shops in your vicinity. They could give you a good buy when one comes along for a used unit.

Good Luck!

I had my 7 1/2 horse compressor pump rebuilt....$1850.00.....so I had it partial rebuilt $750.00 so I could shop around I still should have bought a new one which I did about a year later $1,800.00 compressor on sale for about $1,200.00. I don't think rebuilt compressors are the way to go (except the larger screw types.)

I was fortunate enough to be able to buy a reconditioned one from the compressor shop that serviced the 100hp screw, 50hp screw and 2ea 10hp rotaries that were used at the chemical plant where I worked. All was on the up and up, no excessive discounts. The compressor has lasted for over 20 years with no repairs other than to change the oil, clean filter, and some preventive TLC. It is a Quincy, never had much problem with them on the industrial side of things. I think the reason I have had very good results with them is that I find a good repair shop with a good group of service people who do good preventive maintenance work.

Also I try to listen to them with an accute ear. They almost talk to you and tell you what is happening if you pay close attention to them. My mechanics used to laugh at me when I would use a stethescope to listen to the compressors and motors. After a few minor problems found this way I had to buy all the mechanics their own ones. One guy got real good whith it. He got good with it with other equipment also.

The compressor has lasted for over 20 years with no repairs other than to change the oil, clean filter, and some preventive TLC.

Thats great, Quicy is a rather big player

So true, also I try to listen to them with an accute ear. They almost talk to you and tell you what is happening if you pay close attention to them.

All machines speak, its just that you have to understand what they are saying....experience.

p911

Plenty good advice above. 200yds is not a big deal, regular in factories. One to remember if you do go with the pipe is to ensure you have water traps at all the low points along the line and burying it of above ground allow u-bends for expansion and contraction with temp fluctuations. I recently saw plastic & aluminium composite pipe (Don't know which, but looked like a HDPE) for residential plumbing. It was much cheaper than copper and easier than galvanised steel pipe.

Yes, "200yds is not a big deal", in industries air line runs even for miles and for instrument air requirements use high pressure polymer small bore tubes (not pipes).

As long as there is no third parties properties and government properties like road, running tube should not be big deal.

Moving compressor shop to shop could be problem. How about having only reservoir bottle (adequately sized) with casters such that it could be pushed across?

I keep seeing warnings when looking at PVC and CPVC products that state:

Not to be use for compressed air or gas lines.

So my suggestion to you is to not use PVC for an air line.

One other thing about using PVC even if its going to be buried. If its not tested before covering it up, and your bury it, only to find out it leaks. You may not need your Gym Membership anymore

There is something else. The insurance implications may influence ronseto's decision.

If the local building code prohibits it, your insurance may not cover any losses resulting from the explosion of the compressed gas _(air) line. Not that there would ever be a problem.

Do you know the building inspector?

Really? All the quotes I used in my last post came from:

http://osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=19714

http://osha.gov/dts/hib/hib_data/hib19880520.html

http://osha.gov/SLTC/compressedgasequipment/recognition.html

These are the documents you selectively quoted when you made your first comments in post #8.

ALL of these documents deal with ABOVE GROUND APPLICATIONS, a fact you refuse to acknowledge.

You can thank the lawyers for PVC suppliers blanket statement about use in transporting compressed gas.

Industry standards? Maybe, maybe not.

Cheers.

OSHA is not going to reference OSHA regulations if something should happen. They are going to reference what the manufacturer has as a warning and use that. If the manufacturer warns to not use for compressed air that is what OSHA is going to hit you for.

nice to see you are familiar with OSHA.

but if someone does get hurt?.......they may get one on punitive who knows?????

I think lynlynch was just stating whats out there. I've seen it also, don't like it, but its out there

WHAT ABOUT MOVING CLOSER?????

FORGET all that.

Why go through all that bother for something that is only used occasionally? Let him buy another spare air tank (or a few of them) and a pressure valve. He can fill the tank and roll it the 200 yards to the other shop. When the tank needs to be refilled, he can roll it back over and refill it.

No back-breaking work, no risk of pipe failure, no legal hassles. You can re-sell the tanks someday if you want to.

Let him buy another spare air tank (or a few of them) and a pressure valve. He can fill the tank and roll it the 200 yards to the other shop. When the tank needs to be refilled, he can roll it back over and refill it.

???????Why would you suggest doing things half way...........if you have him (and him being his son) buy all that.......have him buy a air compressor......kinda funny though with just a little imagination.....put a pigeon in it to make it work.

"All that?" A few spare tanks and a valve doesn't sound like much to me, compared with their current plan to dig a 600 foot trench and bury 600+ feet of PVC pipe (or whatever high-pressure pipe they decide to use) and add the fittings needed to connect to the existing compressor and provide a connection port at the far end. Assuming that the local building codes will allow them to do this, assuming that an inspector would pass it, and assuming that the pipe won't leak or rupture -- yet they are doing this to avoid buying another compressor. (?!)

I think they are the ones 'doing things halfway'. I agree, they ought to just buy the 2nd compressor. I was just trying to suggest a 3rd option, maybe a bit less expensive than a new compressor and a bit less work that burying 600 feet of PVC.

third option, ok....then I'll add

Using tanks, not forgetting to mention that when pumping up a tire with air, that tank volume is cut in half. you would need a couple of tanks.

Or dig the trench half way, 100 yards....that way they only have to dig half as much and walk half as far.