[TheForge] PVC for compressed air

Wed Apr 6 11:16:04 EDT 2011

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