[TheForge] [The Forge] PVC for compressed air

Wed Apr 6 11:37:32 EDT 2011

By the time you invest the T&M, you could have done it right the first time for less $$ and aggravation, not to mention the "compressor running for three days until it eats itself when the plumbing fails" scenario, as well as the increased hassle of having to remove guards any time you are called on to maintain the plumbing behind them.

These are what we call "hidden costs" - something that over the years I have b developed some ability in discovering and quantifying for clients. These less-than-obvious costs can add up rapidly and it therefore behooves all seeking efficiencies to give their spending decisions their due analysis and careful consideration.  This is upfront work that appears to consume disproportionate resources in relation to the returns, but I have found that far more often than not it is precisely the opposite case that proves true. Do the groundwork with diligence and care and it will always pay better dividends.  

Sometimes the obvious solution is best.  Sometimes not.
        -A. Vida

-----Original Message-----
From: Bruce Freeman <freemab222 at gmail.com>
Sender: theforge-bounces at mailman.qth.net
Date: Wed, 6 Apr 2011 11:16:04 
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

How about guards?  What if you put some protective guard between the
pressureized PVC pipe and the workspace?  Could be anything -- earth,
wood, steel, oversized PVC (not pressurized, and with escape routes
for air), etc.  Then if the pipe exploded, the shrapnel would be
contained.

On Wed, Apr 6, 2011 at 10:00 AM, David E. Smucker
<davesmucker at hotmail.com> wrote:
> 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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-- 
Bruce
NJ
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