Preferred fittings in a smokebox?

[milwiron]

For steam delivery in a 6 inch diameter smokebox do people prefer pipe threads with unions, compression or flared fittings?

Thanks for your input,
Denny

[Bill Shields]

assuming you are talking about copper tube (since you ask about flare...)

I stay away from unions.

Standard 'olive' compression sleeves on copper can begin to leak after time -> but are often easier to assemble

as annoying as they can be assemble in the first place -> I find flare fittings are easier to get apart years later.

Then there are the British type of fittings where you solder on a taper sleeve to the end of the pipe and jam it in with a backing nut, which are my personal favorite.

http://ibls.org/mediawiki/index.php?tit ... 6_Fittings

[318J]

I have had good luck with stainless steel braided hose, with unions on the ends. (Rated for steam, not just the plumbing stuff at the hardware store) Makes running the delivery lines much easier, takes the heat, and comes apart no problem when the union is generously coated with anti-seize. Even after years.

I've noticed copper tubing has a limited lifespan in a smokebox, particularly with coal burners.

[Bill Shields]

I have had good luck with stainless steel braided hose, with unions on the ends. (Rated for steam, not just the plumbing stuff at the hardware store) Makes running the delivery lines much easier, takes the heat, and comes apart no problem when the union is generously coated with anti-seize. Even after years.

I've noticed copper tubing has a limited lifespan in a smokebox, particularly with coal burners.

dumb question, since I have never considered it in this application:

What is inside the stainless braid to hold pressure?

[Fender]

I've noticed copper tubing has a limited lifespan in a smokebox, particularly with coal burners.

It makes a big difference whether the copper tubing is directly in line with the combustion gas flow through the tubes, or off to the side. The cinders come through the fire tubes at a pretty good velocity, and the “sandblasting” (aka “cinder cuts”) from these cinders is what erodes the copper. This can be reduced or eliminated by wrapping the copper tubing with soft copper wire or other material to protect it in vulnerable areas.

[FLtenwheeler]

I was just inside a smokebox. I used SS compression fittings and SS tube. It should last a few decades.

Tim

[Bill Shields]

I've noticed copper tubing has a limited lifespan in a smokebox, particularly with coal burners.

It makes a big difference whether the copper tubing is directly in line with the combustion gas flow through the tubes, or off to the side. The cinders come through the fire tubes at a pretty good velocity, and the “sandblasting” (aka “cinder cuts”) from these cinders is what erodes the copper. This can be reduced or eliminated by wrapping the copper tubing with soft copper wire or other material to protect it in vulnerable areas.

FWIW:

a few years ago i took apart (for the first time) a 51 year old loco with copper tube wrapped in copper wire as Fender describes.

the copper wire was pretty well blasted away, but the tube underneath was still OK.

[318J]

dumb question, since I have never considered it in this application:

What is inside the stainless braid to hold pressure?

My understanding is the inside is a stainless steel corregated hose. The braided outside gives the circumferential and longitudinal support for the hose to not be blown apart- and also helps prevent the internal hose from being bent too tight and breaking.

We have used up to 6" stainless braided flex hose to tie in mobile rental boilers to existing systems, up to about 100psi. The hoses typically come rated for 150psi. While rare (especially the smaller the line is) if the outside braid is compromised, the corregated hose inside will herniate out of the opening and rupture. It's pretty spectacular.

I wouldn't worry about it happening in live steam though- this kind of line in smokebox service is pretty tame compared to heavy duty industrial service. For our purposes it's pretty much bulletproof. The downside is the price. A 3/8" SS braided line will run about $50+/ft. It also comes in set lengths unless you get a custom length made up. I always order on the slightly longer side.

But it's nice to be able to easily pull it to the side to get at all the tubes or something else if I need to.

Hose-Diagram.gif (87.55 KiB) Viewed 5140 times

[Soot n' Cinders]

I dont have delivery lines in the smokebox with the shay, but I had to replace my blower line not long ago. If you're burning coal, you need to be very careful with copper in the smokebox as it will erode/corrode away. I got 2-3 years out of my original copper blower before it ate through and failed. I replaced the copper tube with 316 stainless tube and a 316 stainless compression fitting from McMaster-Carr. It was not cheap for sure but 1 year in and the stainless looks the same as it did when I installed it, except for the soot.
Only thing is forming stainless and tightening down the compression ferule is a lot harder with stainless than standard copper tube and brass fittings.

[Kimball McGinley]

Sam 3183 - I am kind of stuck at this point on my loco. I like the SS hose idea - can you suggest a supplier and some specs if needed?

[318J]

Kimball,

I would start by doing all your plumbing sans the hose, and use a piece of rope to mock up the flex line so you can get a good idea of the length you need. Avoid sharp bends and kinks. Keep in mind the ends of the hose are rigid. They come with a variety of fittings on the ends, or just plain male/female NPT connections.

I'd recommend having a look on McMaster-Carr and search around for the availabilie options. You can filter by size, length, pressure rating, and more. If the right length isn't available, there are some suppliers that will do custom lengths... for a price.

[Fender]

Only thing is forming stainless and tightening down the compression ferule is a lot harder with stainless than standard copper tube and brass fittings.

Is there any reason not to use a brass ferrule in a stainless compression fitting?