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PVC Propel pressure vessel

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PVC Propel pressure vessel

Postby Bob the Builder » Sat Jun 06, 2009 8:45 pm

Anyone ever try it? I know copper is the commonly used material, but the PVC pipe I've seen is pressure rated to over 330PSI, and our propel is usually only at around 60PSI if I'm not mistaken. Even if the pressure triples if the vessel get hot on a summer day on the bench, pressure would still be WELL within tolerance.

Is there any reason that one could not use PVC for the pressure vessel? Its a lot easier to work with than copper.
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Postby tsenecal » Sat Jun 06, 2009 9:25 pm

just a WAG here, but the propel liquid gets pretty cold when it expands, you will want to make sure anything you use doesn't get brittle when it gets cold.
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Postby JWLaRue » Sat Jun 06, 2009 9:38 pm

Bob,

There was a study done about 10(?) years ago and if I recall correctly, an issue that was reported stated that the PVC could become brittle over time due to the effect of the Propel chemical attacking the plastic.

Perhaps the folks involved in that original study could chime in here and ensure that we have correct information?

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Postby raalst » Sun Jun 07, 2009 5:46 am

I'm not one of those, but I checked google.

It seems there are an awful lot of different PVC types, with different
characteristics. there might be PVC's designed to take pressure
(and pressure fluctuations). but do not expect your drainpipe to have those
chracteristics.

the link below explains the behaviour of (some type of) PVC with
temperature, which is probably what we want to know.
NOT GOOD for the application of propel, although the problem is apparently
not in letting the tank stew under the sun, but rather the low temperatures when filling..

http://www.madisongroup.com/services/failure/casepipe/pipeanalysis.html

hope that helps.
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Postby Sub culture » Sun Jun 07, 2009 6:05 am

What's the problem with copper?

It's the easiest of metals to work with- soft and malleable, and when it work hardens just heat it up to cherry red and quench it in a bucket of water.

Soldering it is a piece of cake, just get the parts bright and clean, and flux it up.
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Postby spongjim » Sun Jun 07, 2009 7:30 am

It was tried already and does work ,32nd par. uses pvc pressure tanks for the torpedo launchers. I put two of these tanks on a PT boat and fire from it.
Now you have to think back 32nd designed these to use freon in them .



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Postby Bigdave » Sun Jun 07, 2009 9:03 am

It does work but as Jeff said over time it will become brittle. :evil:
This was talked about very much in the early years and I believe there is a good article on it in the old SCR's.
I would think Skip would know more about this. Maybe he will chime in.
I myself would not take the chance of using it. BD.
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PVC Propel pressure vessel

Postby clive » Sun Jun 07, 2009 12:26 pm

[quote="Is there any reason that one could not use PVC for the pressure vessel? Its a lot easier to work with than copper.[/quote]

I am not sure about PVC for Propel pressure vessels but now days they use PVC pipe for central heating
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Postby Thor » Sun Jun 07, 2009 1:14 pm

I wrote the those articles in the old SCRs around 1994 about the use of PVC as a storage vessel for compressed gas service. The pressure rating must be considered as only applying to incompressible mediums such as water, oil, etc..

Rigid PVC or other hardware store type plumbing plastics are meant ONLY for incompressible fluids use. The danger lies within the failure mechanism of the PVC itself. It is a chystalline material and fails as such....in shrapnel. I checked with about every manufacturer of PVC, CPVC that I could find at the time and they all supplied me with almost identical information stating that their products were not to be used in gaseous type service. There is a lot of stored energy in a compressed gas. If the PVC vessel fails under incompressible liquid service, you simply get a leak. Not so with an expanding medium. So, use it at your own risk and be warned.

PVC non-rigid tubing designed and intended for LP gas service is a completely different animal all together.
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Postby Skip Asay » Sun Jun 07, 2009 1:15 pm

For many years, 32P sold PVC pressure vessels for their kits. For several years, I sold PVC pressure vessels for my kits. In over 39 years, I've never actually seen any one of them blow up. I recall some years ago a story that was being passed around about someone's PVC tank blowing up. Unfortunately, no one was ever allowed to actually inspect the remains nor know just who it was who owned/built it. Sorta leaves a bunch of questions, doesn't it?

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Postby Thor » Sun Jun 07, 2009 1:26 pm

Hey Skip! Sorry we must have hit submit at the same time!

I used PVC as a propel vessel in my boats for many years as well. I still have a couple of boats that have them installed and never took them out due to my laziness.

I never experience a failure. However, the manufacturers do warn against this application. If you do chose to use PVC, it may be wise to insert the vessel inside the BT to provide an additional layer of protection. It is also smart to wear safety glasses whenever loading propel on board. With the expense of Propel, I have, personally, been trending towards the RCABS type systems that do not require the use of propel.

Adam wrote quite a bit last year about his research into the subject a couple of years back on SP. You might want to check that information out.

What ever material you chose..use common sense and be safe!
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Postby Bob the Builder » Sun Jun 07, 2009 2:28 pm

Thanks a lot for the replies, guys! It was more a question lurking in the back of my mind than a serious consideration. I just made a new one from brass for my 32nd Nautilus project, so there will be no issues.

Very interesting reading. Thanks a lot!
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Re: PVC PIPE

Postby JWLaRue » Sun Jun 07, 2009 2:41 pm

sunworksco wrote:PVC pipe will hold more pressure than needed for propel.The only thing it can't handle is petroleum based fluids.As long as you use schedule 80 pipe you will have no problems.CPVC is even stronger and can take lower temps although PVC will be fine.


John,

Any vessel that we're talking about will fail if it is completely full if Propel and the temperature rises too far. I think the temperatures reached in the back of a car sitting in sunlight during the Summer could be enough.

The best way to ensure that there isn't a problem, regardless of the material used, is to install a pressure relief valve. These things are quite inexpensive (roughly $20) and in the event that there is a problem with the pressure inside the vessel, it'll simply vent the excess until a safe pressure is reached.

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Postby Sub culture » Sun Jun 07, 2009 2:52 pm

Brass isn't the best material to make a pressure vessel from- it can fail without warning.

You'll probably be oy, as it isn't very high pressure, but it's better to use copper.

Model steam boilers aren't generally made from brass,and there's a good reason for that.
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Postby Rogue Sub » Sun Jun 07, 2009 9:06 pm

Yes make it from copper. It is the most common material I have seen used and have not heard of a failure yet. A relief valve is also never a bad idea.
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