“Stainless steel” is a general description that covers a wide range of materials. Some would be suitable, some would not. Full size water tube boilers these days apparently sometimes use material that we would regard as stainless steel. But unless you really know your materials, it would be better to stick to the standard grades of steel used for boilers. The wrong grade of stainless is quite likely to be worse than normal material. Some grades are prone to chloride cracking.

 

Normal steel tubes should actually be able to last quite well, given a bit of attention to water treatment. Typically we don’t actually use our boilers enough, they spend too much time in storage, which is probably where the damage occurs. They should be either bone dry, which would be best, or chock full of deoxygenated water, which is OK for shorter idle periods. The worst is of course to be partly full of water, which will cause corrossion around the water line.

 

Conside how quickly a lathe bed can pick up a film of rust over winter, then remember that the boiler typically does not even have a film of oil to protect it. So a few rapid changes of temperature will soon kick off some corrosion in a boiler.

 

regards

John

Thank you for the kind words regarding my boiler retubing article. When I was collecting information before I started on my 4″ Garrett, I spoke to a gentleman who had repaired a vertical boiler for a boat, and he had the very problem you describe. It was at that point he cut a manhole. I am currently building a 6″ Garrett, and have bought a commercial boiler for that, and it too has come without a manhole door, just a dummy ring welded on for a dummy door. I am not sure why the manhole doors are being omitted, it is one less hole to seal, I suppose. I intend to follow all the aftercare recomendations that came with my new boiler, I will mill a clearence in the smokebox door ring as I build it, so I can pull the tubes out, and I will replace the tubes after about 8 years. This is on the basis that they will pull out OK if they are not too bad, and I will not need a manhole.

Chris Gunn

I shall shortly be starting a 4″ Little Samson. The drawing shows a manhole, and I shall certainly want the manhole operational because of that article. I can put one of those dental mirrors in and check the tubes – that was the idea.

 

With my 3″ LS, I agree that initially sealing the manhole was problematic (I did it all while running on air) Once the solution was found, it sealed immediately and has been trouble free for the year that the engine has been running.

 

All I did was to use plumbers hemp and load it with Foliac Graphite, to form a fibrous matrix to hold the paste, and then did up the clamp.. No gaskets. Let it set, filled the ring with water and  checked for bubbles at 125psig off the compressor.

 

Re comment by `tractionengine42` about flooding interior of boiler with Argon gas. Wouldn`t this be difficult/expensive to source? How about these 2 cheap and easily obtained materials – chalk and vinegar. Could be mixed up in say a bucket and let it get on and fizz. Use a glowing strip of wood to slowly lower in to bucket and when it goes out, you know how full the bucket is with carbon dioxide. Much heavier than air so you can pour it like water into your boiler. Not tried this but think it should work OK – based on school chemistry lessons.

Damp carbon dioxide would promote rusting unless all the oxygen waspurged

out. Depending on the particular boiler, it might be simplest to dry it out by

blowing a stream of hot air through it.

Inert gas is all very well, but sealing would have to be very thorough if air was

to be kept out for a matter of months. It is a bit of a joke that argon is probably

cheaper than nitrogen when the cost of getting hold of a cylinder is taken into

account

Most of the boiler treatments are tannin based so that would sound right. Usual advice when not using the engine for a length of time is to completely fill the boiler with a stronger than usual dose of treatment or completely empty and put a small heater or lightbulb in the firebox to keep it dry.

 

J

Hi Nicholas,

My suggestion for using carbon dioxide was that chalk is free – its everywhere around Brighton and all you need is the cheapest bottle of vinegar that money can buy.It was one for the “tightwads” of this world!

John