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Expanding Air Line

Posted: Sun Dec 26, 2010 11:09 am
by DYI
A recent project of mine includes a 3/8" ID, 300psi rated air hose from Lowes, which I believe is the "Task Force" brand PVC hose (although I've been unable to find a specsheet for it). After being pressurised to 110psig for 12 hours, I noticed that the hose had expanded uniformly to 20mm outer diameter, from the initial 16mm. I suspect that this is a result of air seeping between the two PVC layers, as the fiber weave in between layers shouldn't be able to expand to this extent. This is brand new hose, with no sign of degradation other than the expansion.

I suspect that it's caused by a leak in the inner PVC layer pressurising the outer layer and expanding it away from the fiber reinforcement, which seems to be supported by a cursory inspection. Has anyone here experienced similar behaviour from air hoses under pressure for an extended period of time?

Posted: Sun Dec 26, 2010 11:55 am
by jimmy101
You might measure the length of the hose when it is expanded. The fiber weave can expand if the length of the hose decreases. Is the hose still expanded if you remove pressure from it for a couple hours?

Posted: Sun Dec 26, 2010 12:41 pm
by DYI
That's a good idea jimmy. I measured the hose, and its length had decreased by ~1". After taking the measurement, I dropped the hose's internal pressure down to atmospheric, after which it contracted to its initial diameter. However, the hose feels very soft now compared to the undamaged spare chunk I have, and I certainly wouldn't pressurise it again.

Looks like this one's a write off. I guess I'll replace it with hydraulic hose tomorrow...

Posted: Mon Dec 27, 2010 8:28 am
by metalmeltr
I have a grease gun hose on my fridge compresser-4500psi rating-first time I pressurize it an air bubble got under the outer casing and the casing blew up. The casing now has a sizable hole in it, it is still in service because it apperars to still hold pressure.
Task force really isnt a good brand. I dont trust their tools.

Posted: Mon Dec 27, 2010 12:58 pm
by Gippeto
[quote="metalmeltr"]Task force really isnt a good brand. quote]

Really? :)

You get what you pay for...especially when it comes to tools....more often than not IMNSHO.

Posted: Tue Dec 28, 2010 6:00 pm
by Fnord
Depending on how obtrusive the regular hose is vs. hydraulic line(or if that even matters) it may be better to just wrap it in wire thoroughly. A couple layers of electrical tape should keep the wire in place.

Posted: Thu Dec 30, 2010 9:23 am
by psycix
@metalmeltr

I also use grease gun hose for my fridgy. It can leak air into a bubble under the surrounding skin.

BTB did that with the same hose, and bursted the bubble with a knife. He said it made an insane bang, indicating a lot of pressure in it.
So beware, it may release air violently when such a hose-skin bursts.