A friend of mine added a huge stainless reservoir tank (which he lucked into) to his pneumatic system. He's got it valved to when not required, it's off-line. When he's preparing to do some sand blasting, he opens the valves and lets his compressor (a commercial grade 220 v model) fill both tanks so his blast time is greatly increased. I'd never seen a system like his before or since for that matter but it seemed to work great!

I'm getting ready to rig up the garage at my new place but since the odds of me lucking into a stainless tank like his are nil, I was thinking of getting a long section of large diametre pvc pipe which I can hide up in the attic and use it as a part of the distribution system. I've seen pvc pipe used for distribution before without problem- cheaper than galvy pipe and no concerns about rust but seals need to be well glued and air pressure regulated.

I've never seen a large diametre pvc pipe above like this to expand the overall storage capacity of the distribution system though. I realize adding to the capacity will mean the compressor will need to run longer when it recharges the system but having the extra capacity seems an acceptable trade-off- ie: to run the air-sander for a minute before the compressor kicks in, instead of thirty seconds.

Maybe some of the more engineering-ly minded Forum folks can tell me whether my idea is insane or not. I can't see why it wouldn't work but ..... :crazy:

 

Mac, others have disagreed with my opinion on this, and I expect no difference this time: After years of designing piping for petrochemical plants and serving on Exxon Engineering Standards committee on piping, I would not use ANY PVC pipe in ANY compressed air systems. That is my enlightened opinion and I am sticking to it. :D

Your friend must have a commercial sandblaster that consumes enormous amounts of compressed air. My large bead blast cabinet uses about 13 cubic feet of compressed air per minute, and my 6.5 horsepower, 220V, 80 gallon compressor can stay ahead of it easily. It is desireable for the compressor to be able to shut off and rest during continuous cabinet operation, and it does that. I would re-think the plan, and farm out large jobs that require that much sandblasting firepower.

 

What would you recommend for residential use? 1" sloped galvy pipe with drains throughout?

My friend's sandblaster is industrial and consumes massive air, as you guessed. The way his system is, I've used his bead cabinet for almost 10 minutes continuously before the compresser kicks in.

 

Mac:
I have plumbed three shops with schedule 40 PVC and pressurized it to in excess of 150 lbs with out a single incident in thirty years. The rating on #40 includes a 100% saftey margin.
It however will inevitably develop leaks with temperature fluxation and this always occurs at the glue joints.
The "Disagreer" :seeya

 

I have to agree with Chuck, ... DON'T DO IT !
I design piping systems and pressure vessels for wayer treatment systems.
We rarely use PVC, and never for any system that will see more than 50 PSI.
Failures in pneumatic (gas) systems are usually more catastrophic than hydraulic (liquid) systems because gasses compress, and when something gives, the gas expands significantly, adding to the safety problem.

Use galvanized or plain carbon steel.
If you are worried about corrosion, ... keep the air dry.

 

I appreciate all of your answers but no-one addressed the main topic- is it worthwhile to install an oversized pipe (I won't enter the pvc vs metal argument) to gain extra storage capacity for the pneumatic system?

 

I used 3/4" galvanized pipe for the header, sloped about 1/4" per foot, with reducing tees to 1/2" for service drops, but you heard the volume that I use. If you can do the flow calculations, you want to keep the air velocity below about 7 feet per second to minimize pressure losses. The service drops should actually come off the top of the header and then a nipple, a 90, another short nipple and another 90 down to the service location.

Use a tee to install the service valve and put a valved drain leg below the service valve. All these top take-offs and drain legs will help to reduce any liquid water or trash in your service air. You can install a coaleser, and it will remove some of the water, but if you locate it near the compressor, the air will not be cooled enough to get much condensation...water vapor will go right through it to condense further downstream. I recommend putting another large filter right at one service location to be used for spray painting; Tip Tools has a nice big one with replacement elements that look like special toilet paper rolls.

I ran the main header across the center of the garage along a support beam, but I installed the drop piping inside the walls on the three sides without the doors, with one service location in the center of the ceiling. This minimizes the clutter on the walls, and eliminates having a lot of iron hanging on the walls right where I will be opening my Corvette's door.

Check out the Tip Tools website (http://www.tiptools.com/). Their catalog has a lot of good technical advice for installing air systems; the same information may be on their website.

 

Eggs-zachary! Ole "Disagreer" may have to make a run to the emergency room one of these days to get the PVC shrapnel extracted from his butt. It wouldn't be the first time my advice was ignored with disastrous consequences. :jester :jester :jester

 

Sounds like a good set up. I will probably go with something similar, but because my walls are already in, I will likely stick the drop piping in the corners, where there's no way the car will get close to them but they're still close and accessible. I checked the website you mentioned which provided great info as well as useful diagrams.

All this is still future planning though. My garage is still full of boxes and displaced furniture from the move. Beside, my car is still in RonD's hands but it should be coming home soon.... :cool:



I tried posting an excellent diagram from the tp tools site but it won't work for some reason. Oh well!


[Modified by Mac, 6:35 AM 11/12/2001]

 

Yes, be VERY careful. There are pressurized vessel codes for a reason. Compressed air can pack quite a punch! I've seen scuba tanks rip holes in concrete walls when they let go. Go with a certified and inspected pressure vessel.

 

"was ignored with disastrous consequences."
Chuckles:
It's advise like yours that keeps restorers like me in business, however I agree that the system you describe may very well be superior to the easy PVC method and admittedly safer in the most extreme circumstances, I simply don't see the need in most non commercial; applications.
Don't let this keep you from your lengthy pontifications, I appreciate the added income

 

There is no such thing as industrial grade safety and residential grade safety; preventing personal injury is just as important at home as it is in the workplace. Everything I have ever seen on piping design prohibits PVC in compressed gas systems in no uncertain terms. Few people have air systems in their garage, but the principles for the industrial prohibition are just as important, if not more so, in residential applications. Words like fail-safe and fool-proof come to mind.

I don't think I have ever advised anyone to do any work on Corvettes that I couldn't carry out myself. If anyone has had to send a job to Jerry Clark (or anyone) after fouling up following my advice, please email me; if true, this is a character flaw I definitely need to correct and I will STHU. If I had to chose, however, I would rather enrich "professional" restorers than cause enrichment of the medical profession with advice that led to pain and suffering.


[Modified by Chuck Sangerhausen, 5:25 PM 11/12/2001]

 

The price of steel pipe is reasonably low, ... and it is down right cheap if it prevents even a minor injury.

 

"There is no such thing as industrial grade safety and residential grade safety"

On the contrary, OSHA doesn't inspect your garage, if they did none of us would be able to afford to work on our cars, all our money would go into safety equipment, ( you been wearing that hard hat while rebuilding differentials Chuckie?).

"preventing personal injury is just as important at home as it is in the workplace"

Wow and holy cow, did you come up with this on your own or are you quoting
Dr. Seuss verbatim?

"I don't think I have ever advised anyone to do any work on Corvettes that I couldn't carry out myself."

Only you know for sure and YOU'RE talking, do I want to believe you...HUMMMM, pardon me but I sense a huge credibility gap here based solely on past experience..

" if true, this is a character flaw I definitely need to correct and I will"

This should rank pretty low on your priority list of "character flaws" I suggest you tackle the big ones first.

"I would rather enrich "professional" restorers"

Think pretty highly of ourselves don't we? As if the pros could learn anything from your essays that they didn't read years ago in the in the publications you are now discovering and quoting.
I'll tell Nabors to give you a ring next time they are stumped on a tough question. The attitude is simply amazing, pomposity abounds

"advice that led to pain and suffering.
"

When my attic mounted PVC air system explodes and causes personal injury anyone up there deserves it, speaking of which my rafters need counseling and I have recommended you to "straighten" them out. Start reading those Rafter AIMs now Chuckie.

Ever occur to you that the self serving engineers that write the specs on this crap are just that, self serving bastards that seek only to enrich their own bank accounts by over engineering, think of most as lobbyists or, if you will preachers , you should have a grasp on that concept....maybe

 

You're letting your fevered mind run away, Clark. As for me, I will read no more of your irrational, vile diatribe or respond to it. If you want to make your air system out of paper mache, it is really none of my concern. Each of us have made our cases; the readers can decide for themselves without being distracted by personal insults.

 

All we are saying is give peace a chance! Wait a minute- somebody shot John L. :mad Oh never mind!

Thank you all for your opinions. Having read the information of the tp tools website, I think I'll invest in a larger air compressor rather than trying to cheat extra capacity by over-sizing the distribution system. Like Jer, I've seen pvc used without difficulty but I appreciate the inherent safety of a metal piping. I haven't yet investigated costs of either product- I still have to unpack the boxes from my move! One step at a time. :smash:

 

"You're letting your fevered mind run away, Clark. As for me, I will read no more of your irrational"

Interesting how, when cornered you resort to catch all, generalities. I like the use of last name only very intimidating really. they teach ya that in Sunday school.

My "vile diatribe" is experience spawned, those that write the rules usually profit from them.
In my heart you'll always remain the Snagerdickin of legend, what a lesson.

Clark

 

Jer—,
Chuck—

Calm down. You're both right; your're both wrong.

Jer -- Your plastic piping will, of course work, most of the time. However, in my opinion, this approach entails a small risk. And, I don't think that this risk is cost-effective, relative to a black-iron system. Yes, a PVC system is easy to install, but the necessary pipe-threading tools can be rented cheaply. I am reminded of my ex-boss. He moved to St. Louis, where the electrical house wiring does not run in conduit. While installing a gas line for his range, he was drilling a hole iin the kitchen floor. He hit the 220v line. Ouch. In other words, certain expenditures for safety are cost-effective.

Chuck -- you are correct, to a degree. However, I was practicing Chemical Engineering when you were in diapers, so I know whereof you speak. But, in this case, I think that you are over-reacting.

You know the three degrees of idiot-proof? -- operator-proof; sergeant-proof; and wife-proof. Well, I remember that the Esso Data-book is designed for the third-degree of idiot-proof.

And hang the cost. I've had Bechtel engineers specify type 321 SS to ensure 20-year life in a temporary pilot plant! And Exxon is worse than M. W. Kellogg or Bechtel ever thought of being. (Did you know that, outside the company, the Exxon logo is considered to be quite fitting -- the sign of the double-cross?)

So don't quote, to me, refinery or chemical plant practice. They are not necessarily cost-effective, because they refuse to accept any risk whatsoever. For example -- a double-block-and-bleed on any control valve -- even in a pilot plant that has short test runs? Not cost-effective. Too easy to abort the run, if necessary, to change out a valve.

So, Chuckles, use a bit of engineering judgment, rather than just quoting refinery codes.

There. Have I insulted both of you?

Geezer

 

NEVER insulted by a true Professional Geeze
jer

 

Actually, Geez, I think you have insulted me MORE than you insulted Mr. Disagreer, and I am heart-broken that you have taken sides in this quarrel with origins in the past. :jester :jester :jester

Geez, I didn't quote the standards, but I know what they say. You ARE correct: Exxon has some of the toughest, many would say excessive, engineering standards in the world...and ALL of them have been developed in response to catastrophic loss of plants and personnel; they still manage to burn one down every now and then. I am not advocating building my garage to meet Exxon's standards: I believe that I can make intelligent choices about where to deviate.

But, for those who don't read the Operator Manuals that come with their compressors, however, I will quote from mine: "WARNING!: Risk of bursting, resulting in injury. Never use plastic pipe for compressed air.".
But, you can't believe everything you read...that's probably those ole stuffed shirt, ultra-conservative compressor engineers trying to keep the mindless jackass from sueing them for physical disfigurement and permanent disability.

By the way, being an old maintenance hand that is clearly talking to an old operating manager...How in the blue blazes do you change out a control valve without spilling the entire, sometimes very hazardous, almost always highly flammable contents of both ends of the piping out onto ground underneath the mechanics without a double block and bleed. Exxon solved the problem of unsafe working conditions and lost production by installing a manual valved by-pass around the control valve. Expensive, but it allows production to continue while the valve is safely changed.

Geez, you are clearly a very experienced person from your career as well as Corvettes, and I have great respect for your opinions in both areas. :)