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Using CSST gas pipe for air line

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Lonstar

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Ok, no flaming please, I'm just asking.

I need to put a flexible line between the compressor and the main trunk. I've got a 140' spool of 3/4" Tracpipe PSII CSST gas pipe that I don't think I need for anything. Also have plenty of Autoflare fittings (and am certified).
Thinking about using 3' of it for the flex line. I'm aware gas is low PSI, that's what everyone gets wrapped up around, but CSST has a minimum burst strength of 1,500 PSI. Suggested pressure test PSI is 150. My current compressor is 125 PSI and will soon be replaced with one that's 175 PSI.

Thoughts?
 
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rlitman

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I wouldn't do it.

First off, CSST may be flexible, but it isn't designed for the vibration you see on a whip connecting a compressor to an air plumbing system. I would expect it to eventually work harden and fail.

Second, while schedule 40 black pipe is rated for 150PSI working pressure (yes, I am aware that the PIPE has a significantly higher WP, but people tend to forget that the threaded fittings are mostly class 150), the WP ratings I am able to find for CSST range between 5 and 25 PSI, but not more. While I believe your numbers, I do not believe they represent an actual working pressure rating.
 
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stonesfan68

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The other thing about corrugated steel tubing is that it is in fact, corrugated. That type of tubing will tend to trap liquid water. I’d use something else for this application.
 
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rlitman

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stonesfan68 said:
The other thing about corrugated steel tubing is that it is in fact, corrugated. That type of tubing will tend to trap liquid water. I’d use something else for this application.
Click to expand...

Good point. That, and the corrugations hurt it's flow characteristics too (though that part shouldn't be a big deal for very short runs).

But a piece of rubber hose and a couple of barbs is not exactly expensive or difficult to install.
 
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rlitman

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Lonstar

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Now that winter is taking its grip I decided its time to do the compressor maintenance I put off all summer. Changed the oil and finally replaced the factory wing handle drain with a pipe/ball valve that extends beyond the legs of the tank (compressor about 1.5 yrs old). Also decided to move it a few feet from where it was, so couldn't use existing hose to reconnect to main line, existing being a "temporary" 3/8" air line hose that's been on it since new. Why fix what ain't broke, right? :)

I needed to use the compressor when done so I was looking for a solution using what I had on hand, that's why I asked about CSST. Figured it would just be a temporary thing.....like the 3/8" hose was.
As I was torquing down the autoflare to where it needed to be with a 20" long 1-3/8" wrench, it dawned on me that the compression point in the autoflare is probably going to be the weak point. Over time vibration from the compressor is going to weaken the thin walled stainless steel tubing and cause it to snap. So that's when I answered my own question. I'm positive the tubing can withstand 175 psi without a problem, but the flared ends are the weak point.

It's holding fine right now, but today I ordered a 3/4" hydraulic line and swivel fittings. Best to stop with the temporary line and do it right. The kicker is total cost was a few dollars more than just one of the Tracpipe autoflare fittings I'm using now.

Thanks guys
 
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