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Topic Review (Newest First)
03-04-2004 04:35 AM
Kevin45 To help out with altering black pipe just add a union here or there. That way it can be disconnected without having to unscrew everything. If properly planned out you may only have to alter a couple of pieces (re-thread) and normally they will do this where you buy it for a small fee or free. Build it to last for the next 100 years. After that, who gives a @#$%

Kevin
03-03-2004 02:31 PM
Goobzilla Pretty clever on the chiller!

I may have to give that some thought. That's another bennie about Black Iron pipe. It's just like Tinkertoys, if you want to make a change, just unthread it and make a change.

I bought 7 21ft. lengths of pipe and they cut them in half for me so we could get them in the back of my truck. Borrowed a chop saw and a pipe threader and a buddy & I plumbed my 32x34 shop in a couple hours.

Ron
03-03-2004 11:51 AM
Beenaway2long I'm confused! B.I.P. comes in so many different lengths, why do you need to cut it? A coupling and a short nipple or two and your there. We did my buddies garage in 3 hours. Granted, it took 4-5 beers each, but hey, thats Overtime ! After the PVC episode, he (we) aren't taking any chances. Copper may be OK, but I'll take the steel from now on.

Whatever method you choose,be sure to have "catch pipes" below ant outlet. Like the cleanout on any natural gas line in your house. I retro'd all of mine to have 12" pipes with a ball valve on the end to keep the air nice and dry. My buddy went as far as putting a "chiller" on the end closest to the compressor to minimize condensation.

Here's a quick description:
Compressor to ball valve with high flow disconnect : went to flexible hose to isolate vibration to another high flow fitting. He turned the 3/4" B.I.P. down into a 5 gallon pail (with drain) and used a series of 90's and nipples to go around the inside of the pail 8 times. It goes through a line dryer then brought that up to the main branch on the ceiling. Each runner went to the side wall and went down to a T. One piece continued down with a ball valve, the center of the T went to the air coupler. Where he does his painting, he has another air filter/dryer. Overkill? Maybe. But he'll never worry about it again. Every once in a while, open the valves and drain the air. When he paints or uses alot of air, he fills the pail with ice water to minimize condensation. Said he saw it on Eastwoods tapes.
03-02-2004 06:29 PM
Goobzilla Copper is good too, anything but PVC. I got my black iron pipe for $.31/ft at the local industrial supply place.

Ron
03-02-2004 12:52 PM
nightMARE I've seen PVC explode under pressure. It's already been pretty much said that it's not a good option, but no one seems to be talking much about copper. It's way easier to run than black pipe. Just cut and solder, and from what I've seen it's cheaper. It will handle all the pressure that a compressor will put out. It can't take a ht as well a black pipe but most air lines are over head and I know in my garage we don't throw too many hammers and wrenches into the rafters.
03-01-2004 09:40 AM
TRACKMAN Thanks Kevin for runnin' this all out to ground! Your last post was great. It's starting to make sense. I had never envisioned the PVC to be brittle but when these engineers begin describing it's "glasslike" state, that says it all. You would think their industry would require a warning stamped on the side stating "Not for use with compressed gases". We've got warnings on everything else!!

I've been against the black pipe for just the reasons they stated, cut it (messy), thread it (even a worse mess), mount it (heavy), twist it on, test it, yikes, a leak, now need another 1/2 turn at an elbow in the middle of the system, etc. Don't get me wrong, once installed, it is the best.

I worked at a race shop that used copper airlines, thought it was an overkill but I'm thinking that's the way to go now. With just a little prep, a little heat and the right flux, that solder flows everwhere. Although the thermoplastic may be the ultimate answer, I need a safe product that I can use and be able to run down to the hardware store to buy another elbow, etc.

Thanks again guys, I hope others who are considering PVC read this thread.

The TRACKMAN

Thanks Kevin for runnin' this all out to ground! Your last post was great. It's starting to make sense. I had never envisioned the PVC to be brittle but when these engineers begin describing it's "glasslike" state, that says it all. You would think their industry would require a warning stamped on the side stating "Not for use with compressed gases". We've got warnings on everything else!!

I've been against the black pipe for just the reasons they stated, cut it (messy), thread it (even a worse mess), mount it (heavy), twist it on, test it, yikes, a leak, now need another 1/2 turn at an elbow in the middle of the system, etc. Don't get me wrong, once installed, it is the best.

I worked at a race shop that used copper airlines, thought it was an overkill but I'm thinking that's the way to go now. With just a little prep, a little heat and the right flux, that solder flows everwhere. Although the thermoplastic may be the ultimate answer, I need a safe product that I can use and be able to run down to the hardware store to buy another elbow, etc.

Thanks again guys, I hope others who are considering PVC read this thread.

The TRACKMAN
02-29-2004 10:02 PM
Goobzilla And a trained chimp (like me for instance) can cut & thread a piece of black iron or galvanized pipe, so what's the point?

I guess the bottom line is it's your shop, so you do what you want. I'm about as cheap as they come, but I won't skimp on safety. If some one told me there's a 1-10% chance this PVC could fail catastrophically and shoot jagged shrapnel all over your shop OR for about the same time & money you could eliminate the risk, I know which way I'm leaning.

Ron
02-29-2004 03:54 PM
jimk You also have to look at repairing them if they need it.Pvc...a two year old can fix.
02-29-2004 09:39 AM
Kevin45 I was doing a search on PVC airlines and ran across this:

[i]Fellow List Members:
I've followed the thread on using PVC pipe in compressed air service and
feel that I need to add my two cents worth.
Let me state now that PVC and compressed air are a deadly combination.
PVC has a high "rubber to glass" transition temperature. This means that at
higher temperatures (>45 degrees F, approx.) PVC exhibits rubber like
characteristics; it's somewhat flexible. At lower temperatures, PVC goes
through a "glass" transition which (as the term would imply) means that it
exhibits glass like characteristics; it's extremely brittle.
It is this brittleness that causes PVC to be deadly in compressed gas
service. When it fails it is catastrophic, hurling sharp pieces of shrapnel
at high speed into anything and anyone in the way. Failure can be caused by
simply plugging in to a compressed air line or even starting or stopping a
compressor.
Additionally, the quality of the system can be compromised by the installer
in that, by using too much primer and cement, a weak spot can be caused from
puddling of the cement in the fitting.
I've seen these failures and they're quite frightening.
Don't be confused by pressure ratings on the pipe. The pipe is perfectly
capable of containing the pressure but under NON SHOCK conditions.
There are two companies that manufacture an ABS compressed pipe system that
can be solvent joined like PVC. One is Chemtrol (their product is called
ChemAir) and the other is Duraplus (Durapipe in the UK) the product name is
Airline.
We can't afford to lose any LBC entusiasts. Please, keep your shops as safe
as your cars.
Rodney McDonald
Spanish Fort, AL
'76'B 393703 ]/i]



Ease of installation and greater economy certainly are big reasons to consider thermoplastic pipe for plumbing your compressed air system.




--------------------------------------------------------------------------------


For years, metal piping materials -- primarily copper and black iron -- have been the overwhelming favorite for plumbing compressed-air systems. Recent advances in materials technology, however, have made thermoplastic pipe a safe and economical alternative to traditional materials.

A big advantage of metal pipe, tubing, and fittings is that installers are familiar with them and the techniques for joining them. Black iron is inexpensive, but installation is time-consuming and labor-intensive. Moreover, threaded joints often serve as a source of leakage. This leads to higher operating costs because compressors must operate overtime to compensate for the leakage. Although connections between copper pipe and fittings are less prone to leakage, copper components are more expensive, and installation, again, is labor intensive -- especially when large diameters are involved.

But these aren't the only drawbacks to metal piping systems. Interior corrosion can cause scaling and pitting on inside surfaces. As the corrosion products combine with moisture and other contaminants, they accumulate on the inner surfaces of the pipe and fittings, increasing their roughness. As the ID becomes rougher, pressure drop though the system increases. Again, this ends up costing money by reducing efficiency of the compressed air system. Perhaps more importantly, particles can dislodge and clog or damage end-of-line equipment.



The good and bad of PVC

Because of these drawbacks, compressed air system users have been seeking alternatives to traditional metal pipe and tubing. Over the past five to ten years, industrial plastics have been developed that present an attractive alternative to metal piping.

PVC piping is relatively inexpensive, easy to install, lightweight, and corrosion resistant. However, PVC has one major drawback. It is brittle. An inadvertent impact could cause the piping to shatter, endangering surrounding personnel. Most PVC pipe manufacturers warn against using PVC for compressed air service due to potential liability from such failures. The Plastic Piping Institute, in their Recommendation B, states that plastic piping used for compressed air transport in above-ground systems should be protected in shatter-proof encasements, unless otherwise recommended by the manufacturer. In many states, the Occupational Health and Safety Administration (OSHA) has stepped in and regulated against using brittle plastics such as PVC in these applications, and additional states are following suit.

The strictest standard in the country has been issued by California's OSHA. It includes five tests, as well as a requirement for comprehensive marking of the pipe and fittings. These tests include long-term hydrostatic, short-term burst, and three specialized impact tests -- all to ensure the safety and ductility of the system. The impact tests include striking frozen, pressurized pipe with both blunt and sharp strikers, using various forces, and striking a frozen pipe with a hemispherical striker, using various forces.

Manufacturers are required to present the results of these tests for review upon request. When specifying a thermoplastic system, for safety's sake it is important that your supplier meets Cal-OSHA regulations, regardless of the state in which the system will be installed.



An attractive alternative to PVC

New thermoplastic piping systems -- using high-density polyethylene (HDPE), for example -- overcome the brittleness problems associated with PVC. They efficiently and reliably deliver compressed air with lower material and installation costs and longer service life than with metal systems. They offer a margin of safety missing from PVC.

These new thermoplastics are safe because they expand at the point of failure, tearing open rather than fragmenting dangerously. They do not accumulate scale on their ID, nor does pitting or corrosion occur, and they are unaffected by synthetic and mineral oils used in compressors.

The internal surface of thermoplastic piping typically has a roughness factor, C, of about 150 to 165. Metal piping systems, on the other hand, start out with an interior surface roughness factor of about 120. This factor is inversely proportional to friction head losses: as C increases, system pressure drop over a given length at a given flow decreases. This means that when installed, the ID of thermoplastic pipe and fittings is smoother, so lower pressure drop occurs than with metal piping components. Moreover, because it is less prone to accumulating particulate contamination, and corrosion does not occur, the ID of thermoplastic piping systems remains cleaner and smoother.

The substantially rougher surface of metal piping allows contaminants to collect in the millions of tiny pits and crevices on the ID of the pipe. In addition, moisture and other contaminants can react with the metal itself and produce corrosion products that also accumulate. Over time, these contaminants and corrosion particles continue to collect and build up to form scale. As the scale builds, it roughens the ID of the pipe and fittings, which increases pressure drops. Ultimately, the higher pressure drop increases the demand on the system's compressors, which increases operating cost. Moreover, pipe scale particles can dislodge and damage equipment when carried downstream. Because thermoplastics do not promote the formation of pipe scale -- even when exposed continuously to condensation -- these problems do not exist with thermoplastic piping systems.



Installation advantages

Thermoplastic systems also offer low cost and quick installation. Heat-fusion welding makes pipe joining quick, easy, and extremely reliable because there are no threads to leak. Unlike PVC, no glues or cements are used, so there is no cure time. Testing can be conducted immediately after installation. In contrast, some glues may require as long as 24 hours to fully cure before full system pressure can be applied. In addition, fusion welding can be performed in any environmental condition using simple, lightweight tools without prior experience. These tools are available for low-cost rental or purchase.

A cost comparison shows that black iron is less expensive than standard thermoplastics. However, in tool set up and installation comparisons the plastic system takes only half the tool set-up time and one third the time to weld each joint. Moreover, in many pipe sizes the weight of black iron is 10 times that of thermoplastic pipe, making iron components more difficult to maneuver, support, and install, especially in larger sizes.

Thermoplastics are even more cost effective when compared to copper. The price of thermoplastic pipe is less than copper, although the cost of the fittings is a little more. Overall, the total systems appear similar, but, again, the real savings appear in the installation time and maintenance of the system. Soldering of copper pipe is much more time consuming than the socket fusion method used with thermoplastics.

When done properly, soldering a joint can take from five to seven minutes by a well-trained and experienced plumber or mechanical contractor. If done improperly, the joints can leak, especially in large-diameter systems. On the other hand, unlike soldering, socket fusion can be performed in less than two minutes by anyone with minimal training, and with less chance for error. The result is a strong, leak-free joint every time.



Considerations for thermoplastics

An important consideration when designing a thermoplastic compressed air system and selecting the appropriate thermoplastic material is thermal expansion. Thermoplastics expand and contract from thermal changes more than metals do. This must be taken into account during system layout by allowing for expansion at corners or by building in expansion loops and offsets.

Another important consideration is pressure rating. Be sure to select a material and construction with an adequate margin of safety for the pressures to which your system will be exposed. In the case of a safety failure or a temperature rise, a system should still perform at the operating pressure.



Scott N. Robichaud, is assistant vice-president of engineering, Asahi/America, Inc., Malden, Mass.
02-29-2004 09:21 AM
TRACKMAN Thanks Ron for your input, OSHA rules are usually made up because someone got hurt, etc. I don't doubt that they have banned PVC for use with compressed gases. I'm just trying to understand the "why" part, that's to say why is this Sched 40 PVC good for 495 PSI of water and not safe for 135 PSI of air? Maybe the compressability of air causes a pulsating effect that the water doesn't ???

I have some buds in OSHA, I'm going to contact them.

Thanks again for helping to keep us safe!

The TRACKMAN
02-28-2004 10:31 PM
Goobzilla
Your call I guess

PVC is not rated for compressed gases, period. The pressure rating does not apply to gas. The method of failure is the real problem with pvc, it grenades w/lots of shrapnel. But everyone is free to do as they wish I guess. You'd think OSHA and state safety organizations banning its use in compressed gas (air) installations would be enough for people to get the message. But as my old motorcycle safety instructor once said "If you've got a $20 head, get a $20 helmet."

If anyone can explain why people are so stubborn about this when A) The dangers are known and real, B)the alternatives are not that much more expensive or difficult to install, I'm all ears

Ron
02-28-2004 09:36 AM
TRACKMAN
Airlines from PVC

The ongoing controversy regarding PVC for shop air really interests me. I have used Sched 40 PVC for 10 years and never had a problem. My decision to use it is based on the rating printed on the side - 495 (maybe slightly less) PSI. I will use it again in my new garage. I've seen some posts regarding PVC bursting with scary consequences. I'm wondering if these folks used that thin wall PVC that the Irrigation contractors use or is there a real concern about using the Sched 40 PVC? If this sched 40 stuff is a problem, what does that say about the rating system?
What think??

The TRACKMAN
02-12-2004 02:19 AM
Goobzilla
It Happens A LOT!

Glad you're friend wasn't hurt. Hopefully people will get will get the message before they are hurt or killed.

Ron
02-11-2004 06:55 AM
Beenaway2long IT HAPPENED LAST NIGHT !!

My buddy went out to his garage and fired up the heat, lights and compressor to start sanding out his 70 Nova. He went inside while the garage warmed up, and came back out to hear his compressor still running and the air coming out full tilt. The PVC pipe ruptured/split and there were 3 pieces of the pipe missing. It was in the middle of a run, no where near a joint or clamp. One piece was stuck in the back seat, which was covered in plastic, leaning against the wall.
I wonder if it was because it was cold, or dumb luck. It was in there for 3 years. He's done the same warm up deal many times, in colder weather. Makes ya wonder.

Tonight is the trip to Home Depot for 3/4" black iron pipe.
02-11-2004 02:46 AM
Goobzilla
PVC is not cool!

In fact PVC piping is prohibited for use in compressed gas systems (including compressed air) by OSHA. Here's a link:

OSHA's stance on PVC

It's a shrapnel hazard when it fails, very dangerous stuff! I know some people have gotten away with it for years without incident, but when it does fail, it isn't pretty.

Copper or Black iron pipe isn't that much more expensive and not that hard to work with. I plumbed my 32 x 34 shop w/ 1/2" black iron pipe in a few hours with a chop saw and a rented pipe threader.

Just wanted to share some info.

Ron
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