Union in air compressor lines

[JTG]

I'm going to be hooking up my new (used) compressor in the next few days and I'm struggling to figure out the best way to install the lines. At one spot I have 3/4" threaded male hose coming from a backup tank. I want that to go into a T to tie into the new tank. The problem is the threaded hose end does not swivel. So if I thread the t into the hose I can't thread it into the tank. I have a similar problem going to the regulator.

The way I see it I have 4 options:
1. use copper lines to and solder connections. The problem with this option is if one of my threaded connections has a small leak I can't tighten it much because the copper line restricts the movement.
2. Use black unions. Can these work with pressure up to 175psi? I have no experience with these.
3. Hammer unions. Better than option 2? Never used them.
4. Copper compression fittings. Do they have them for 3/4" and for that pressure? I've only used them for my fridge water line.

What would you guys do?

 

[Strouty]

I am using black iron unions on my 1" and 3/4" pipe setup without issues, but I never thought about it, I just assumed that the unions were rated equal to the pipe. Now I am going to check.

 

[Strouty]

Looks like they are rated the same as the pipe.

http://www.anvilintl.com/usercontent/submittal-info-sheet/7154_PF-SUB-385.pdf

As for copper, they make compression fittings that big, but I am not sure of what the rating would be.

 

[WILD-BILL]

I'm also using unions in my airline piping. No issues at all.

 

[PoorOwner]

I have unions. It makes it so I don't have to solder one run of 25 foot section on a ladder.

It does seem to leak a little bit but a little dressing of sealant on mating surfaces is what I plan to do to fix it.

 

[Boilerhouse]

I would go with the B.I. union(s). You will need one for sure, a second would be if you wish swivel capability at both tanks. No problem getting them rated up to, and beyond, 175 psi rating.

 

[MJD1]

Unions or hydraulic swivels would work. I prefer the hydraulic pile swivels, since they are more compact and have hex fittings.

 

[Richard Cranium]

if you are worred about the union leaking, just put a little liquid Teflon on the mating surfaces.

 

[kunkernator]

I use unions in my setup too. The first time i tighten one down, it generally doesnt leak, but after breaking it free, then re-tightening it, i put some pipe dope on it.

Also have used large JIC fittings for air line unions before, they are EXCELLENT.


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