[TheForge] PVC for compressed air

Wed Apr 6 11:22:19 EDT 2011

Have to agree with Dave.  Had one lousy section of PVC from compressor to steel in Mesa shop.  It failed and the 20hp compressor ate itself.  Compare cost of large industrial compressor with cost of black pipe to plumb shop.  Never say it will not happen.  That is what those boobs in Japan did and see where it got them.  The old saw, "penny-wise, dollar-foolish has its roots in firm wisdom.  Decide accordingly.
        -A. Vida

-----Original Message-----
From: "David E. Smucker" <davesmucker at hotmail.com>
Sender: theforge-bounces at mailman.qth.net
Date: Wed, 6 Apr 2011 10:00:33 
To: Blacksmithing List Sponsored by ABANA<theforge at mailman.qth.net>
Reply-To: Blacksmithing List Sponsored by ABANA <theforge at mailman.qth.net>
Subject: Re: [TheForge] PVC for compressed air

Dave,  I know it is costly, but I would replace your PVC pipe.  As I said it 
will fail, it is just about when.  Dean Coffman (Big Blu Power hammers) had 
a large PVC line is his shop fail.  No one got hurt except that his big 
compressor just ran and ran, as it happen in off hours if I remember 
right -- he has steel today.  Take a look at what is out there as a lower 
cost option than steel pipe.  The issue is more than fatigue -- more that 
sunlight -- more than oil.  It is all of the above plus some other things 
too.

As a side note on fatigue -- all pressurized aircraft will have their skin 
fail -- if you wait long enough -- enough cycles.  It is a the nature of the 
material.  Aluminum doesn't have a fatigue limit or endurance limit the way 
steel does.  (With steel if you stay below the endurance limit you will not 
have a fatigue failure.  Provided you haven't had a major overload that 
lowers the endurance limit or surface defects etc.)  This is something that 
is closely tracked by the airlines and airframe manufactures and  to re-skin 
the aircraft after so many cycles is the norm.  It is the number of take 
offs and landings, not the number of flight hours that make the difference.

Dave

--------------------------------------------------
From: "Dave Mudge" <dave at magichammer.net>
Sent: Tuesday, April 05, 2011 11:56 PM
To: "Blacksmithing List Sponsored by ABANA" <theforge at mailman.qth.net>
Subject: Re: [TheForge] PVC for compressed air

> The "CYA" clause in my personal safety first and don't get sued book 
> dictates
> that I say "I AM NOT RECOMMENDING THIS".....
> I have a medium size air compressor that puts out around 20 cfm @ 125 
> lb/sq.in.
> It sits atop an 80 gallon tank which is then piped into a 150 gallon tank.
> I use sch. 40, 1-1/2" pvc that runs up the wall and around the shop in a 
> loop.
> The 1-1/2" "T's" off and runs to within a foot or so of the air hammer
> where it reduces to 3/4"
> and then feeds the controls of the hammer. I also "T" off and run down the 
> wall
> to shoulder height, reduce to 1/2", and through fittings and such to 3/8" 
> rubber
> or plastic air line for regular shop use. I used this system for 10 or 15 
> years
> before the hurricane and have re-established the system since rebuilding.
> It has not failed so far (thank the gods). My system stays charged 24/7.
> I never turn off the compressor. I don't have any leaks so I don't worry 
> about
> the compressor constantly running when I am not using any air. My system 
> is not
> flexing very much. What will disintegrate pvc is direct sunlight. If
> you use pvc and
> it is exposed to direct sunlight, you should paint the part in the
> sun. The paint of course
> will protect the pvc from the sun. I DO NOT RECOMMEND THAT ANYONE USE PVC
> FOR THEIR SHOP AIR SYSTEM.
> be safe,
> dave m
>
> On Tue, Apr 5, 2011 at 8:15 AM, David E. Smucker
> <davesmucker at hotmail.com> wrote:
>>
>> If you use PVC for compressed air it will fail -- the only question is 
>> when
>> and how. Not only is fatigue an issue but oil from the compressor may 
>> also
>> effect the PVC.
>>
>> There is plastic pipe compounded and design for air system piping -- but 
>> you
>> will need to go to a major plastic pipe supply, or one that sells systems
>> for shop use to find it -- not your local Big Box store.
>>
>> Here is one supplier http://www.rapidairproducts.com/ they sell both 
>> nylon
>> tubing and a composite plastic and aluminum pipe and the required 
>> fittings.
>> This is just one source -- other can be found by google on "compressed 
>> air
>> piping"
>>
>> Dave
>>
>> --------------------------------------------------
>> From: "Paul N" <crosspein at sbcglobal.net>
>> Sent: Tuesday, April 05, 2011 8:33 AM
>> To: "Blacksmithing List Sponsored by ABANA" <theforge at mailman.qth.net>
>> Subject: Re: [TheForge] PVC for compressed air (A little OT -- a 
>> mini-scale
>> saber saw?)
>>
>> > I'd be cautious about using PVC for compressed air. For years, there
>> > have been debates about the danger, and I pretty much disregarded them.
>> > Then about 10 years ago, I gave in and decided to replace it with type
>> > "L" copper. Type L is what is recommended for compressed air. Many of
>> > the big box stores carry it, in addition to the cheaper Type "M", which
>> > is what is used for the most common plumbing.
>> >
>> > The danger of PVC is similar to what is currently in the news for the
>> > Boeing 737's. The constant flexing from the pressurization and
>> > depressurization work hardens it over timee and makes it brittle. Then
>> > it cracks and fails catastrophically, often sending plastic shrapnel in
>> > all directions.
>> >
>> > I became a true believer as I removed the sched. 40 PVC I had 
>> > previously
>> > installed. It had been "in service" for about 7 years, and when I 
>> > pulled
>> > those pieces down, a number of sections cracked and shattered. They 
>> > were
>> > no longer the pliable pipes that they were when I installed them. So,
>> > unless your plumbing is underground, I'd be very wary of using PVC for
>> > compressed air.
>> >
>> > **paul
>> >
>> > On 4/5/11 1:07 AM, peter fels wrote:
>> >> How much air do you need?
>> >> More storage means more air for longer.
>> >> Be very conservative with air pressure tanks!
>> >> They can go off like a bomb!..Lotta kinetic energy!
>> >> Putting them somewhere way over there, has a lot of virtue.
>> >>
>> >> My first compressor was from an old refrigeration unit,
>> >> The tubing went to 2, 250 gallon, ( carefully washed out) former 
>> >> propane
>> >> tanks.
>> >> I used several hot water heater over- pressure valves in each one and
>> >> tapped a hole in the bottoms
>> >> for radiator drain valves .
>> >> Ordinary sched 40 house plumbing will generally deal with 100 PSI. if 
>> >> you
>> >> are careful.
>> >>
>> >> It was enough air to do a little sandblasting...or run an air tool for 
>> >> a
>> >> while.
>> >> Needless to say, that rig took a long time to recover.
>> >> Safe from air tool boredom.
>> >> Cost around $5 for fittings i couldn't scrounge.
>> >>
>> >> On Apr 4, 2011, at 8:49 PM, Bruce Freeman wrote:
>> >>
>> >>> How big a tank do you mean?
>> >>>
>> >>> On Mon, Apr 4, 2011 at 6:59 PM, peter fels<artgawk at thegrid.net> 
>> >>> wrote:
>> >>>> An inexpensive little compressor ( even one from a bigger freezer) 
>> >>>> and
>> >>>> a big pressure rated storage tank,
>> >>>> will cover a whole lot of applications.
>> >>>>
>> >>>...
>> > <snip>
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