[TheForge] PVC for compressed air

Wed Apr 6 10:00:33 EDT 2011

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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