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Discussion Forum

Are pipe unions directional?

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JCB

12-28-2002 06:38:38




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I am installing a propane furnace in the shop and trying to do it to code. I am putting a union in the black pipe line after the shut off. My question is: Are unions directional i.e. does it matter which end is up or down stream?
#2 question: On the outside of the shop, I will be using a copper line to the tank. Why are copper flare fittings required and copper compression fittings not allowed?

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T_Bone

12-29-2002 15:58:16




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 Re: Are pipe unions directional? in reply to JCB, 12-28-2002 06:38:38  
Hi JCB,

A flare will hold pressure and lots of it where as a compression fitting will leak after time. The ferrel will not seal to the tubing as well as a flare and becomes loose thus the leak.

Unless they've changed code, it's brass fittings that are required. The line from the gas line riser has to be an approved AGA(American Gas Assoc.) listed flex line for gas, also the same AGA rating for the manual gas ball valve. CU tube hasn't been allowed for years.

In about 1990? or so they also approved galvanized pipe for gas as they changed the way the pipe was galvanized so it wouldn't flake off.

T_Bone

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cannonball

12-29-2002 08:31:35




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 Re: Are pipe unions directional? in reply to JCB, 12-28-2002 06:38:38  
yes union are directional as richard said, but also as others said at low pressure it did not matter, but when you use high pressure you put them in as richard said..in the gas industry we used compression fittings, but used ss tubing and fittings. we was not allowed to use any copper tubing in anything..have nice day may god bless



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Richard

12-28-2002 15:38:33




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 Re: Are pipe unions directional? in reply to JCB, 12-28-2002 06:38:38  
Actually, pipe unions are designed to flow from the Female Nut towards the Male threaded half. Nobody pays attention to it and it normally will not cause a problem, however they should be installed properly when in High Pressure High flow service. If you look closely at the mating surface, you will see that it's directional.

Again, most of our guys install them any which way and there hasn't been a problem. Same as a ball valve, they are directional but often get installed any which way as well.

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JCB

12-29-2002 06:55:31




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 Re: Re: Are pipe unions directional? in reply to Richard, 12-28-2002 15:38:33  
Thank you Richard, and all the others that responded.



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pg

12-28-2002 14:32:38




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 Re: Are pipe unions directional? in reply to JCB, 12-28-2002 06:38:38  
the flare fittings take vibration better, wont loosen up. compression on gas is undependable.



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Mac

12-28-2002 08:43:36




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 Re: Are pipe unions directional? in reply to JCB, 12-28-2002 06:38:38  
Have used a ton of unions on steam pipe and overhead heaters. We installed them whichever way was convenient. Same with huge water pumps that we might have to R&R for repairs. As far as flare over compression. I think the flare is a more dependable type connection. I never was overly fond of the comp. type. However, they do have their place sometimes. Depending on application.



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George G

12-28-2002 13:08:12




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 Re: Re: Are pipe unions directional? in reply to Mac, 12-28-2002 08:43:36  
Mac, didn't mean to attach my replie to your replie. Ment to attach it to JCB's question. Sorry bout that.



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George G

12-28-2002 12:52:27




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 Re: Re: Are pipe unions directional? in reply to Mac, 12-28-2002 08:43:36  
Unions you can use either way. Compression fittings when used properly work fine. I use compression and bite-type flareless fittings all the time in hydraulics. The biggest problem I find is people use the wrong tubing with them (the reason there against code for gas use in most places). They use tubing with too thin of a wall thickness,or in to high of a pressure system. Example-3/8 tubing with .032 wall thickness with compression fittings is rated for a max psi of 200 pounds, same tube, but with flared fittings would be rated for 1000 psi. If the tubing is too thin, the ferrule will crush the tubing and not bite into the copper. bla bla bla Good-by.

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Rod (NH)

12-28-2002 07:41:59




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 Re: Are pipe unions directional? in reply to JCB, 12-28-2002 06:38:38  
Hi JCB,

I'll give you my opinion:

I have never seen a union that was directional. There may be some specialty type union that is but I am not aware of one. If it is there should be a flow arrow indicating direction imprinted on it. I do not think you will find that to be the case though.

I think copper flare type of connections are far more dependable and leak-free than the compression style. Compression styles seem to be popular but I have never been able to get consistent leak-tight joints with them. Maybe I am too heavy handed and tend to overtighten them. In any event, I stay away from compression type fittings for all my copper tubing use. I consider the flare type to be superior.

Rod

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