Copper refrigerator line on steam engine

[EnidPuceflange]

As the title says, can you use 1/4" and 3/8" soft copper refrigerator line for steam and water plumbing? I get that it has to be silver soldered ....

Logically, water pressures run up to about 150psi. the running pressure is 90psi, so hydro would be the max at 180psi.....and the tube is (I think) drawn over mandrel so seamless, so it SHOULD be OK, right?

This is for steam plumbing from fountain to injectors, as well as injector to boiler check valve. I need a solid yay/nay because I'm about to get a boiler shipped from the UK and the boiler supplier also has a bunch of fittings and stuff including what I'm assuming is "definitely OK for steam use" copper tubing, and I could order some to come with the boiler.

What says everyone?

[Pontiacguy1]

I've used it many times on many different locomotives for external piping. I've soft-soldered it in the past, and it will hold for a while, but I always ended up going back and having to fix it and use the 45% silver stuff on there. After doing that, it didn't fail again. I would not use it inside the smoke box, though. External piping is OK, but inside the smoke box it will typically not last too long in a coal burner. I've had to replace it on every steamer i have, and I used 303 stainless steel tube when replacing it.

I usually just go buy it from the local Ace hardware or similar instead of having it shipped, unless you need a size that they are unlikely to carry.

[Bill Shields]

DO NOT USE soft solder in any location that will be hot, exposed to boiler pressure and / or does not have a shut off valve between it and the boiler....and even if there is a valve...once it starts leaking -> can you get your hand in there to close a valve without getting burned (not everyone wears asbestos gloves)....

as PG says....in the long run, all the soft solder will eventually fail, so it is best to just go in and silver it to begin with and forget it....and my personal experiences is that once you put lead solder on something, forget about ever getting silver solder to stick unless you TOTALLY REMOVE EVERY BIT OF THE LEAD SOLDER...which is tough on fittings...

One of the problems with hardware store fittings is that they will not take a lot of mechanical 'abuse'...and if you get crazy and push on one too hard, it is likely to kink and / or bend...and then where have you saved $$$ ?

Having to rip the cab apart to replace a $4 fitting is penny wise - pound foolish...

[Fender]

Another thing to consider, is what type of connections/fittings will be used with the copper tubing. Some common methods are compression fittings, flared fittings, or threaded fittings. Copper tubing is generally too thin to thread directly, so usually a thicker brass threaded tube is silver soldered onto its end. Similarly, model union connections are silver soldered onto the tubing. Flared connections are more bulky, but have the advantage of being able to be attached and removed multiple times without leaking. Compression fittings are less bulky, but tend to leak if they are removed and re-connected multiple times.

[rudd]

I am not seeing 303 tubing on the market, I see 304, 321, and 316.. If the 303 is better, where does one get it?

[Harold_V]

You're not likely to encounter tubing made of 303, as the sulfur (or selenium) content wouldn't be desirable.

For chemical resistance 316 would most likely be an acceptable choice. 304, 321 or even 347 would probably serve well for this purpose. Each alloy offers chemical resistance to specific compounds/conditions, so if you're concerned, check the available options against anything of concern.

H

[AnthonyDuarte]

The thin wall copper will work fine, but it is very susceptible to forming kinks when bending and it can't be threaded. Thick wall copper tubing is harder to kink, but it's also a little harder to bend. Nothing a good annealing won't take care of.

I would not recommend compression fittings for injector installations, especially on the suction line between the tender and injector, which is precisely where I tend to see them. They are available and easy to install, but they're frequently a failure point for the installation. If you really need the ability to separate the line, use a union.

[Pontiacguy1]

Could have sworn I had some 303 stainless tube at one point. Must have been 304 stainless. Either way, putting the stainless tubing inside of your smoke box will be a lot bigger pain to do initially, but you should never have to do it again.

[amadlinger]

I absolutely agree with what Pontiacguy reported on the internal smokebox piping. Over the decades of hard-running, I had replaced copper and brass piping components in the smokebox several times; having now switched to 316SS stainless steel with Swagelok fittings several years ago everything still looks like the day I installed it (once you clean off the soot).

Regarding piping on the outside of the locomotive, copper works fine but I have had great success with hard brass tubing instead of copper refrigeration line. The brass comes in straight lengths, forms cleanly and crisply, is easy to thread (not gummy like copper), and is available in a variety of diameters and wall thicknesses (so can select a thicker wall for threading). McMaster and Onlinemetals.com have great selections.

[Bill Shields]

Amen on the brass tubing concept.

[zimirken]

I've used lots of hardware store soft copper tubing. I use flare fittings and red rtv silicone on npt threads. I've had issues with Teflon tape and pipe dope holding pressure during cold hydro, but leaking once it gets hot. Rtv silicone has to dry overnight, but I've never had a leak with it. Also it's super easy to unscrew the threads and just as easy to clean off. Flare is infinitely better than compression IMO, as long as you have one of the good flaring tools. I've always had problems with leaky compression fittings, and you need a new ferrule every time you make a change. This is all just my experience though.

It makes sense that people have trouble with copper in the smoke box. Copper is susceptible to corrosion from sulfur, and coal often has a high sulfur content.

[Bill Shields]

Compression fittings when used on copper are just fine as long as you solder the ferrule in place.

Biggest problem with copper tubing in the smoke box is not so much sulfur but abrasion from flying cinders