"Union" fittings

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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Lopez Mike
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Re: "Union" fittings

Post by Lopez Mike » Wed Jun 07, 2017 2:57 am

I don't doubt that they are good fittings but I can be in Pavement Narrows, Montana and find flare fittings. Every propane fitting in creation uses them and the flaring tools are in every corner hardware store.
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Re: "Union" fittings

Post by cyberbadger » Wed Jun 07, 2017 3:45 am

A person gripe about full scale union fittings. I usually love the Class 3000 forged steel fittings (they are heavy, but sometimes are cheaper), but the union that mcmaster carr sells has no hex on the one side. And I know I'm crazy for not liking pipe wrenches, but I find no hex on a union very inconvenant. I like to use crescent wrenches wherever possible. The Class 300 malleable fitting the sell has a hex on both sides....

-CB
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Re: "Union" fittings

Post by barts » Wed Jun 07, 2017 3:47 am

For me, sizing tubing such that I leave the right amount for the flare is hard; the Swagelok fittings work like a compression fitting so I just need to get the tubing the right amount into each fitting. I'm lazy, basically.

I do copper flares for propane, of course. Our 1971 Airstream is all flared copper underneath.

I also use the steel hydraulic fittings. Tough as nails, and cheap.

= Bart
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Lopez Mike
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Re: "Union" fittings

Post by Lopez Mike » Wed Jun 07, 2017 3:50 am

I got rid of all of those plumbing unions and went to hydraulic ones. 37 degree JIC. Simple, cheap, reliable, good quality control, rated for thousands of P.S.I. and available everywhere.
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Re: "Union" fittings

Post by SL Ethel » Wed Jun 07, 2017 12:53 pm

Well, I think I'm sold on the hydraulic flare fittings. Thanks everyone for the wealth of shared experience and advice.

Cheers,
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Re: "Union" fittings

Post by DetroiTug » Wed Jun 07, 2017 1:16 pm

A few years ago, I started to put a reflex gauge on my boiler and due to space constraints, the series 300 piping was too bulky and found that the hydraulic NPT fittings were much smaller and compact - perfect. Had it all piped up and installed and I was doing some reading on it and discovered that the hydraulic fittings are harder and more brittle than standard malleable iron fittings. I'm way late to the party with this because many people are using them without incident. But it is something to consider from a fatigue/failure standpoint. I opted to not install it, but may still in the future.

-Ron
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Re: "Union" fittings

Post by Lopez Mike » Wed Jun 07, 2017 1:23 pm

How did you discover the variation in malleability and how did it affect the safety and/or usability of the fittings?

So far the only thing I've needed to do with my hydraulic fittings is sand and paint the exterior and sometimes lightly polish the mating surfaces to get a good seal without having to tighten them down quite so firmly. Several of my unions are disturbed regularly for trailering and hydro testing.

I'm getting ready to replace my existing JIC fittings with S.S. ones for esthetic reasons (the cad plated ones are getting quite rough looking).
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Re: "Union" fittings

Post by DetroiTug » Wed Jun 07, 2017 2:39 pm

Quote: "How did you discover the variation in malleability and how did it affect the safety and/or usability of the fittings?"

I think it was on a Parker site that explained the difference. The metal composition in hydraulic fittings is stronger/harder which typically equates to more brittle and less malleability. How did it affect me or my experience with it? :) Well it caused me pause using them on my boiler which holds around 40 gallons of scalding hot water and a pipe failure on the glass with someone standing near it, would not have been good. Not to say that's going to happen, but it caused me to hold off until I was more confident and better understood using them there. It looks as though a lot of people are using them without incident. It's always good to question and err on the side of safety.

I think it was Fred that mentioned boiler makers of old would take sheet stock intended for boiler construction and fold it over on itself (180 degree bend) in a press, if it survived without cracking it was deemed satisfactory. Experience from doing fab work has shown many metal materials have poor malleability. Very common 1018 cold drawn steel can only bend about 45 degrees without cracking, must be heated beyond that. Hot roll 1014 or similar must be used for cold bending components. So it's logical to surmise, 1018 would not be permissible for boiler construction. Poor malleability of steels was a major factor in early boiler failures. Stick to the ASME B31.1.

-Ron
Last edited by DetroiTug on Wed Jun 07, 2017 2:53 pm, edited 2 times in total.
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Re: "Union" fittings

Post by Lopez Mike » Wed Jun 07, 2017 2:49 pm

I will keep this in mind when I'm inspecting things.

I changed over for several reasons. The only plumbing unions that I can get locally are such chinese junk that it gives me pause to use them in my house. They look like dog poop. So crude. Made of some 'iron like' material. Beyond malleable.

I can disconnect the hydraulic ones with regular wrenches. I'm offended by pipe wrenches. I keep one in the boat but mostly as a hammer. Sad to say, there is a right way and a wrong way to use a pipe wrench as a hammer.
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Re: "Union" fittings

Post by DetroiTug » Wed Jun 07, 2017 6:47 pm

Quote: "The only plumbing unions that I can get locally are such chinese junk"

Sadly that is the case. According to a local plumbing supplier, there is no schedule 40, 1/2" or 3/4" NPT pipe made here in the states anymore. That is why it's so cheap at HomeDepot. 3/8, 1/4 and 1/8th inch are still available from domestic producers at higher end plumbing places, and the quality difference is stark and so is the price. Nearly everything at Home Depot is from China. When I did my Ofeldt coils, I used sch40 1/4", cheapest US made I could find was $3.85/ft.

-Ron
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