Steam passages inside the boiler

[Brian Hilgert]

What do most people building boilers use for steam passages inside of the boiler? Copper or steel tubing? I know Soot n Cinders is using copper and silver solder, and jlakes85 is using steel. Is there one benefit over another or just personal preference?

Thanks,
B

[NP317]

My Ed Perry-built boiler (2000) uses copper fire tubes silver-brazed to the tube sheets, and steel pipe and fittings for the steam distribution to the cab.

My Mikado boiler was built by a now-gone Texas Boiler Maker (2008) and uses the same materials in the same places, but the copper tubes are rolled into the tube sheets.
~RN

[Glenn Brooks]

Most of the recent boilers built in our club have copper tubes, rolled in. Most of the builders prefer copper tubing because of more efficient and quicker heat transfer.

Glenn

[SteveM]

Not to change the subject, but get some clarification:

Why rolled instead of some form of soldering / brazing / welding?

Is it just for the replace-ability factor?

Steve

[Brian Hilgert]

Thanks for the replies, I'm using Copper flues and plan on rolling them in.

I am more concerned with the dry pipe, the inner pipe from the throttle to the outside of the boiler, the pipe from the steam dome to the turret, etc.

[Bill Shields]

consider ability (elimination of need) to do future maintenance above all else.

dry pipes typically do not need attention for the life of a boiler, but if it does..what do you do??

[Brian Hilgert]

Bill. That is the main reason I am asking the question of what material to use. The piping will not be easily accessible after the boiler is welded. So what material is less likely to give trouble in the future? Should I worry about rust or silver solder problems?

[FLSTEAM]

Schedule 80 pipe and forged fittings should last well into your life time and beyond.
Dissimilar metals will always present the possibility of corrosion. Tubes will most likely be replaced one or more times in the life of the boiler.

[Wolfgang]

Most of the recent boilers built in our club have copper tubes, rolled in. Most of the builders prefer copper tubing because of more efficient and quicker heat transfer.

Glenn

Glenn, I'd bet dollars to donuts that the difference in heat transfer coefficient between steel and copper, makes no noticable difference in the use as fire tubes.

Wolfgang

[Bill Shields]

the only "real" reason to use copper as a fire tube is because they will not rust out and require frequent replacement.

you don't have to worry about dissimilar metal / corrosion problems in one of our boilers..think about how few operating hours / calendar DECADE our boilers are actually WET and active..it is a non-issue.

I am partial to copper and silver soldering and bronze flanges (not brass). Sometimes I use bronze screw fittings with bronze threaded pipe.

Sometimes I use steel..

[James Powell]

Bill, we rusted out the end plates on a boiler in a year...

Now, this was a special case, in that it was a 1500w electric fired boiler, with more copper than steel in it. The electrolytic action on it must have been violent in action, as the ends were 1/2", and there was pits that were in excess of 1/4" deep over the course of perhaps 2 years, but more likely 18 months. The boiler was held together with, IIRC, a single stay in the centre. (& O rings on the V'd steel plate, IIRC...).

At any rate, saying it can't be done- it can, but only under rather unusual situations. We have gone through 3 boilers so far on the roller, but that is at the bottom edge of practical steel boilers. (one of them had <8" of grate...) These have copper flues rolled in. The advantage of rolling is that if the tube decides to leak, you can re expand it in the future. If you silver solder, and it leaks after the first coal fire, you are up a tree.

James

[James Powell]

To answer the question, I would use copper for the dry pipe inside the boiler, with bronze at the wet end, and if it is going through a bushing, steel bushing material, in a steel boiler, or bronze on a copper boiler.