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Old 08-24-2012, 08:43 PM   #1
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Default Co2 Manifold question

My regulator has a check valve and 50-55psi safety valve built on.
Integral pressure relief valve for safety: Pressure Relief Valve Releases at 50-55 PSI

Since it has the 50psi safety outlet, could the Co2 manifold be built out of schedule 40 PVC which has a rating of 120 to 810 psi?

Don't want to turn the beer fridge into a claymore but trying to build it out on the cheap.



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Old 08-24-2012, 09:15 PM   #2
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Using PVC to store / deliver pressurized gas is inherently dangerous, even at only 55 PSI. The problem is the gas inside the pipe is compressed and if the pipe were to rupture the pressurized gas will drive the shards away from the pipe very fast. It would not be as bad as a claymore but the flying pieces of PVC could hurt someone.

Water is safe in the same pipe because the water is not compressed, it's only under pressure and if the pipe were to rupture you would only have a water leak.



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Old 08-24-2012, 09:18 PM   #3
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Quote:
Originally Posted by thargrav
Using PVC to store / deliver pressurized gas is inherently dangerous, even at only 55 PSI. The problem is the gas inside the pipe is compressed and if the pipe were to rupture the pressurized gas will drive the shards away from the pipe very fast. It would not be as bad as a claymore but the flying pieces of PVC could hurt someone.

Water is safe in the same pipe because the water is not compressed, it's only under pressure and if the pipe were to rupture you would only have a water leak.
I'm not sure this is correct. Pressure is pressure as far as the pipe is concerned. I'd be more worried about the PVC being permeable to gas and wasting a lot of CO2.
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Old 08-24-2012, 09:26 PM   #4
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No. PVC piping is meant for liquid applications, thargrav is correct. It's not designed to hold gas pressure. It's actually against OSHA regulations in the workplace. Please use another material!

http://www.osha.gov/dts/hib/hib_data/hib19880520.html
http://www.usplastic.com/knowledgebase/article.aspx?contentkey=787
http://www.lascofittings.com/supportcenter/compressedair.asp

From the last one:
Although the use of PVC for compressed air transmission may appear easy, and inexpensive, the dangers are real and immense. Water, like most liquids, is not compressible, therefore it cannot store energy. When a hydrostatic failure occurs, water is projected, but the shrapnel is not projected very far.

On the other hand, air and other gases are compressible. This can result in large amounts of stored energy. System failure could lead to a disastrous situation when this energy is released, sending shrapnel outward. Severe injury and damage can result.

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Old 08-24-2012, 09:32 PM   #5
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It's true that pressure is pressure & both exert the exact same pressure on the pipe. And it's also true that as long as the pipe does not rupture there is no issue.

But it's not the pressure that's the problem, it's the energy stored inside the pipe. Water leaking from a pipe does not expand & can only leak as fast as the water source will let it. But pressurized gas will EXPAND at a very fast rate - this is what drives the shards of PVC away from the pipe and into whatever may be in the way.

This is why using PVC to carry compressed air is a OSHA violation.

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Old 08-24-2012, 09:35 PM   #6
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Ok point taken. My question though: Why would other materials be safer in the event they failed at lower than rated pressure in a gas application?

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Old 08-24-2012, 09:39 PM   #7
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I'm not a material science expert, but I think in general it boils down to plastics vs. metals. When metal goes, it ruptures. When plastic goes, it shatters. It's about the failure mechanism. Remember the Redhook worker that was recently killed by an exploding plastic keg... pressurized plastic is just plain dangerous.

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Old 08-24-2012, 10:51 PM   #8
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Quote:
Originally Posted by Ryush806 View Post
Ok point taken. My question though: Why would other materials be safer in the event they failed at lower than rated pressure in a gas application?
Iron pipe full of compressed gas ruptures - PVC pipe full of compressed gas explodes.


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