The Steamboating Forum

Hi, I am planning on using all stainless fittings for all my pipe connections from boiler to engine are their any pro's/ con's with black iron compared to stainless?

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Black iron (steel) will rust slowly. Stainless will likely not corrode, but is sometimes subject to hidden chloride corrosion which can cause sudden failures. Since we take some care to minimize chloride levels inside our boilers, I'd worry about this more if the boiler is in a open boat used frequently in salt water and subject to salt spray (like mine).

Also, remember that schedule 80 pipe should be used for all boiler nipples (stainless or black iron), since threaded schedule 40 pipe is not strong enough to handle mechanical loads often placed on boiler piping.

I prefer painted (w/ high temp paint) schedule 80 steel nipples for my own boat.

- Bart

Why stainless? Cost is high, and 300 pound malleable iron fittings (with schedule 80 piping generally used) do the job as well. A stainless flex hose is proper between the boiler and the engine if there is not a properly designed piping flexibility for the steel piping without a flex hose. But most of us are not up to designing such a piping "stress loop". The flex hose is the only stainless piece I would use.

I agree with Bart and Fred.

I just wanted to add - depending on your pipe fitting supplier (I'm using McMaster Carr) - sometimes the Class 3000 forged fittings can be cheaper than the Class 300 (as Fred stated it 300 pound). Also at least McMaster Carr has certain fittings that are only available in Class 3000.

The Class 300 fittings as Fred said, are malleable iron fittings.

The Class 3000 fittings are forged steel. Way over kill, but if it's cheaper then the Class 300 ones it's something to consider. The real negative with the Class 3000 fittings is some of them are considerably heavier.

I bought most of the fittings for my boat. It's about 85% Class 300, and 15% Class 3000. Some wouldn't like the mixing on aesthetic grounds, but It doesn't bother me.

-CB

I concur. Stainless is way overrated except for being pretty. Besides, you need to insulate any high temp stuff to save fuel.

Any time stainless gets tucked away where it might get wet and not dry out it is really treacherous. Rapid corrosion in crevices especially if there is any slight movement that might erode the very thin chromium oxide layer that makes it nice looking.

Save the stainless for cooking pots.

The stainless fittings and pipe I'm getting for free, that's why I'm leaning that way. What kind of pipe insulation is used ?

There is already a topic within this forum addressing insulation and lagging for our steamboats.

Some effective methods:

1. Pure cotton rope, wound around the piping, labor intensive, and very nice looking. Be sure to get cotton rope, most of it in these times have plastic wound into the cotton, and that will NOT do for steam temperatures.

2. Fiberglass or mineral wool about 3/4 inch thick over the piping, with an outer covering of cotton cloth, soaked in Plaster of Paris/water, and wrapped to give rigid insulation covering. You only have minutes until the plaster sets, so plan accordingly.

3. Aluminium foil wrapped in several layers over the piping, exterior lagging as above. Lagging is optional from a technical standpoint, but is recommended to protect the insulation from damage, and to make things look good.

lighthousekeeper wrote:The stainless fittings and pipe I'm getting for free, that's why I'm leaning that way.

Free may sound good now but this isn't household plumbing. The failures are not pretty for steam, I'll leave it at that. Maybe get that free stainless and sell it, and use the money to buy appropriate fittings?

-CB

lighthousekeeper wrote:The stainless fittings and pipe I'm getting for free, that's why I'm leaning that way. What kind of pipe insulation is used ?

Are you sure these are schedule 80? You want this for all piping between the boiler and the first
shutoff valve on each boiler connection because of the risk of threaded boiler nipples breaking at the
root of the thread.


- Bart