#9 max steam pressure

[Benjamin Richards]

I suppose it could be done, but I suspect the economics of it are a big reason it's not done. I found a resource addressing the exact question of EN-plating a firetube boiler which indicated that electroplating "in-situ", especially for such a mechanically intricate piece as a boiler, would be prohibitively costly due to the complexity of bringing the process to the workpiece, and ensuring thorough coverage. Galvanic corrosion may also be a factor, or it may place additional restrictions on the water supply.

[Mike the Choochoo Nix]

It would be easier to just build a boiler with stainless steel.
They are trying that in Australia with some large model boilers. I don't know the grade of steel, but it is used in heat exchangers. Yes there are problems using stainless, but maybe some day that will be the thing to do.
Mike Nix

[Keith Taylor]

It would be easier to just build a boiler with stainless steel.
They are trying that in Australia with some large model boilers. I don't know the grade of steel, but it is used in heat exchangers. Yes there are problems using stainless, but maybe some day that will be the thing to do.
Mike Nix

The problem with stainless is chloride embrittlement and stress cracking. And it doesn’t transfer heat as efficiently.

Keith

[Dag Bonnedal]

Normal steel for pressure vessels is the absolute simplest form of soft steel without any alloys or other additives. This is because you want the highest possible elasticity and maximum elongation before it cracks. It is expensive only because you need full traceability and documentation for its production.
When the Germans started to build locomotives with higher pressures (225 psi and above), they used a high tensile steel called Izette. They had big problems with fatigue and cracking before they learned how to handle it. You know better, but wasn't there similar problems with the NYC Niagaras?
In this respect, stainless steel is not good for pressure vessels.

In the UK and also in Sweden many (most) locomotives still have copper fireboxes (new ones are even built in the UK!). This makes the corrosion problems more severe because the galvanic difference between the metals gives corrosion in the steel, e.g. pitting on the tubes. Thus good water  treatment is even more important in this case.

Dag B

[Mike Fox]

Dag, that was very informative. Thanks.

[Bill Piche]

I could be wrong, but I think the Hiawatha Pacifics only got 1 cycle out of their stainless boilers before they were all retired early due to stress fractures.

As for corrosion resistance, from what I've been hearing lately from some of our MNG members working other jobs you can't beat Apexior 1. Fort Wayne uses it on the 765 and gets good results. It needs to be sand blasted off at the end of a tube cycle, but that has to happen for inspection of the surfaces anyways.

Apexior No. 1 is a product utilized to protect interior boiler surfaces. It was developed in the 1920s and widely utilized by a multitude of railroads. The Norfolk and Western went as far as coating the superheater flues prior to installation.