14 replies to this topic

[Mthomas]

Of the tubings shown on the McMaster Carr site, which is the appropriate one(s)?

Edited by Mthomas, 07 September 2021 - 06:39 PM.

[ntsqd]

Any on the page that I linked will work. The DOT semi-flexible is probably the best for no leaks, but will be some pain to install. I have used the regular nylon and the polyurethane (PU) tubing. Each has their +'s and -'s and I can't really suggest one over the other without some idea of the goals. I think that the nylon is ultimately better at sealing, but the  PU is a little more flexible and can make the install go easier. Neither leaks badly, it just seems like the PU system needs to stay pressurized or it will leak a little on first re-start and then settle in and stop leaking. I have recently discovered that one of the fittings in the PU system is being pushed on by a part that I didn't install. Remains to be seen if moving it so that contact can't happen changes my experience and perception of the PU tubing.

 

You will want a sharp blade to cut the tubing. Cutting with something like diagonal wire cutters willl achieve the cut, but tends to collapse & kink the tubing. Making insertion into the fittings difficult and it may not always seal. I use one of these:

https://www.mcmaster...hose-cutters-7/ but I have in a pinch also used a carpet knife with a new blade in it.

 

[Mthomas]

Is there a tool to form the flare in any copper tubing used? Also, is it common to use copper as an initial connection, or is steel frequently used? Also, what length is typically needed to isolate the heat from the tubing at the compressor? Thanks

 

Reason for all the questions is that I have OBA now with a connection at either end primarily used to air up for the highway,  but the rubber hose connecting everything is degrading and needs to be replaced. to sure what it is, looks like air line used in tire shops. Someone else set this up for me a few years ago.

Edited by Mthomas, 07 September 2021 - 11:10 PM.

[ntsqd]

To do it correctly the 37° flare that I use requires a flaring tool that forms that angle. In copper you *may* get away with using the much more common 45° flaring tool if your tube nuts, tube sleeves, and fittings are all steel. The first time that you tighten the tube nut it will sort-of re-flare the end of the tube. I will suggest a little graphite in the threads and between the tube nut and the tube sleeve if you're going to do this. While not at all good practice, it does work. You may want to fully anneal the 45° flare before trying to "re-flare" it. The issue with copper is that it work hardens, and it could harden enough just from the whole flaring/re-flaring process that it fails from fatigue cracking after a fairly short service life. The annealing of copper is easy, heat with a propane torch until you see a hint of green in the flame and the tubing is glowing, then dunk in water. If you did that to steel the results would not be what you want, but both copper and aluminum will fully anneal from this process.

 

Could also just use 45° fittings et. al. Those have never been as confidence inspiring for me, but they may work fine.

 

I used 10 feet of 3/8" copper tube on our camper's OBA because that is what came in the box that I bought. That is massively overkill. I'll guess no more than a couple feet is necessary.

[cware]

I used all AN lines with Vibrant fitting fittings.