Patching a metal air line

[dfanders]

Gents,

We have a M52 Gasser. On the last run we heard a distict "HISS" coming from under the engine area.After shutting off the engine, we found that tha large diameter air line that runs from the air tanks to the air compressor has a SMALL abrasion hole in it. The line had rubbbed against a frame support and the hole it made was under 1/16" of an inch - the size hole froma fabric or leather working needle. When made a temp fix using rubber tubing and hose clamps.
This hole does NOT stop the truck from building up air pressure to max levels and keeping it there, while she runs. What it does do, is let the air leak out, once you stop the engine.
I do not have access to a new line, so i need to patch the current one. What is the best way to do this?
1) Braze on a section of copper over the area?
2) Use a material like JB weld directly on the hole section ( being careful not to get it int he hole.
3) Other fixes???

Cheers,
David Fanders

 

[porkysplace]

Flared fittings and a union .

 

[M813A1]

You can do what Porky said or just go to a hardware store and get some new copper line and replace the line .

 

[rosco]

You can braze weld it. Usually the rubbed area is more extensive, extending each side of the pinhole. But often, it not possible to braze it, in place, due to fire hazard, so you have to remove it. You also need to be pretty good, to braze, brass on brass. If you do, build it up good.

That is an important air line. The best repair is to replace it with, DOT rated plastic air line. Any heavy truck store, will have it and the special fittings, reqiored for it. The plastic is better. Its immune to vibration, and very abrasion resistent, and fuel proof. Also, its a piece of cake, to replace it, in tight spots, because it is so flexible. I have even used it for fuel lines!

 

[quickfarms]

I would replace it because if your repair fails and you have an accident the ins co or dot could use the repair against you

 

[gringeltaube]

...............................
3) Other fixes???
.................

A good (temporary) fix for small holes; quick and effective: a small piece of inner tube, held in place with a hose clamp.


On a side note: I'm not sure if I would use plastic (polyamide) brake tubing (like this) all the way, starting right at the air compressor's output down to the reservoir. I fear it might get too hot, there.

G.

 

[zout]

If it were a temp repair and a temp repair only a couple hose clamps and hard rubber tubing. Then as soon as you get to a location you can make the repair correctly - take the line off and remake a new replacement.

I would not even consider running main air pressure line with a repair in it any longer than necessary.
If there were a commerical vehicle it would not be FHWA acceptable with a repair in a brake line or air pressure main line. Secondary air systems are acceptable to have couplers or unions in them to make a repair.

 

[Rustygears]

The temp repair indicated was fine to limp home. The permanent fix is to either patch in a new section of metal line using flare type fittings at each end or to just replace the entire line. You'll perform just as much or more labor brazing (including disassembly, prep and reassembly) compared to replacing it and the braze will always be a spot for future failure. Just as important is to find and fix the cause of the problem. Except for corrosion, metal lines just don't fail. Resolve why the abrasion mentioned occurred and ensure it cannot occur again.

For a high pressure application, I would NEVER use epoxy. It is less reliable for that use than brazing. It is subject to cracking and future failure due to flaws in surface prep and poor bonding as well as joint failure due to a combination vibration and temperature cycling. Epoxies like JB Weld are great stuff, just not for this application.

 

[dmetalmiki]

Definately No

Can braze. Legal issues. Plastic? yes..well the..''##**" that swapped me the ZILL 131 for my KRAZ (nightmare journey) replaced the main brake air line with plastc truck hose..and it MELTED at the compressor and blew out. NO BRAKES AT ALL (no sir no way whatsoever!). Could have been CATASTROPHIC..Fortunatley we were on the wrong road out in the sticks (sat nav guidence) when it let go..My lad used "emergency brakes" ie. MUD kirbside HEDGE bushes small trees! (and only going 12 - 15 mph.) still took a frightning distance to come to a stop.
Moral? Go Sure. be safe..AND (then) feel satisied and confident in the braking ability of your truck. You can get all sorts of different fittings to join the pipe after cutting to suit.

 

[deathrowdave]

Swedge Lok compression fittings and a new piece of tubing . Much easier than flareing the tube. These fittings are rated for 6,000 psig. They are made of Brass or Stainless Steel. Very easy to use and have a double compression collar not a standard compression feral.

 

[gimpyrobb]

Its just an air compressor line, you can cut it clean and use a compression fitting to join it back again, but it shouldn't be too hard to replace the whole line. Replacing it would allow you to make sure it isn't rubbing anything again.