It may not be applicable to your boiler Brain, but newly made steel/copper riveted boilers in days gone by where routinely store outside to 'weather' for a time, the resulting corrosion helping to seal caulked seams.

Guy

When i worked on full-sized boilers we "pressed 'em up" with anti-corrosive treated water until it came out the vent valve on top of the top boiler drum before leaving them unused for any period.

Members of our club store full size and model engines either completely full with water containing a good dose of treatment or completely dry. (damage by the water freezing is not a problem here in Oz).

Dry storing should be done after a blowdown when the engine is still hot. Remove the manholes and mud bungs and use wicks or syphon to remove ary remaining water. The remaining heat should evaporate any moisture in the boiler.

I was taught about puting a lighted candle inthe boiler and sealing it to remove oxygen but do not know of anyone who does it this way.

Paul.

Edited By Paul Lousick on 10/05/2019 23:58:08

Some years ago the firm I worked for used to put lime in trays and place in the boiler before boxing up changing every few months I should have said these were very large industrial boilers

A couple of points:

Burning a candle in a boiler for storage – so that hydrocarbon fuel will produce CO2 and H2O, which will condense and combine with the CO2 to make carbonic acid, and then lay in the nooks and crannies – Doh!

Filling to the brim. Does nothing to address crevice corrosion – in fact encourages it. You will find plenty of crevices around all fittings, around the foundation ring weld and around stays – none of which can be cover welded from the inside of the vessel. Maybe if you are filling to the brim with an inhibitor laden water.

For my boiler, anything over a couple of weeks it is always dry – blow down hot and let the residual heat do the rest. For over winter, take the plugs out as well. My boiler is stored inside in a heated room. For less than a couple of weeks (between rallies) then store well filled. I use boiler treatment anyway which will scavenge most of the oxygen out.

Martin

you can get breathers filled with silica gel, dry it out as others have suggested above, then fit breather/driers to any open holes so moisture from the air can't get in and condense with temperature changes.

To really go to town you could wrap a soil heating cable round it and cover it with a thick blanket, but that's probably taking it a bit far

Brian,

The eternal question! I remain unconvinced that for a 3" scale boiler blowing down hot results in a dry boiler. There is no other ventilation so even if the water is driven off the plate into the atmosphere within the boiler unless that atmosphere is subject to an air flow the moisture in the air trapped in the boiler will just re condense on the plates as the temperature equalises. Given that possibly your boiler probably doesn't have a man hole and the wash out plugs are small where will any decent air flow come from? I have a friend with a 4" scale foster boiler that is around 20 years old now and still on its original set of tubes! Annual ultrasound inspections show very little wastage and an internal endoscope inspection shows no scabbing on the tubes or evidence of pitting corrosion on the plates. The only 'repair' over the boiler's life has been welding in a new bush for the fusible plug due to wastage of the threads. His routine is to leave it full of treated water 12m of the year, during the winter it is protected by a low wattage black heater in the fire box. Whether the condition now is a result of his approach or due to exceptional quality material in the original build who knows? However I am following his example and have upped my treatment regime and certainly this year at its annual cold exam the internal condition looked much better than pervious.

I think it's one of those things where theory and practice do not always coincide and the proof is in the long term evidence / condition. Certainly when I have blown my 4" R&P hot and then removed the plugs a week later it has still been thouroughly wet inside (as viewed through a scope) hence my comments re ventilation (it has no man hole to knock in). I think with my 6" Savage boiler with a decent sized man hole and generous size washout plugs including one on the tube plate there is a greater chance of getting it dry if it is opened up while still warm but other than that I can't see how the moisture is going to get out! Certainly I wouldn't run a steel boiler without treatment. I have seen a 3" Marshal boiler run on plain water most weekends for around 7m of the year that scaled up on the inner firebox resulting in star cracking round the stays – scrap inside 8 years!

Paul.

I can share what the Royal Navy did in 1922, which I think makes good sense and is easily applied today. They blame most of the Navy's problems on the practice of blowing-down leaving the boiler wet and open to the air. Three causes are identified:

1. Ordinary corrosion is due to Carbon Dioxide and Oxygen. These are present in all natural water, and can also be absorbed from the air. The gases have little effect when the boiler is active, but cause rapid corrosion in damp corners. The recommended counter-measure is to fill the boiler completely with boiled water (ie with no dissolved oxygen), plus a little lime. Lime absorbs Carbon Dioxide and neutralises any other acid that may be in the water. Washing Soda and Caustic Soda are recommended as substitutes for Lime.
2. The second cause is an electrolytic reaction around any spots of rust that may have formed in the boiler. Rust creates new rust, which explains all my old car problems! The cure is to put a lump of sacrificial Zinc in the boiler and make sure it's electrically connected to the steel. It creates an electric potential such that the Zinc goes first leaving the steel unscathed. Sacrificial Zinc is sold for use in boats.
3. Third cause is a quality issue with 1922 steel that's probably been fixed. It's the tendency for sulphur impurities to create Iron-Manganese Sulphide within the metal. The sulphide reacts with water forming a very corrosive mix of Iron Sulphate and free Sulphuric Acid. The symptoms are 'rust cones' and rapid perforation of the plate. The cure for this is also Lime water.

Modern owners go to extraordinary lengths to protect big boilers in and out of service. But for our purposes I think completely filling with boiled water containing a dash of washing soda would slow internal corrosion effectively, and installing a Boat Anode as well should put a cap on it. The boiler should be sealed to stop atmospheric Carbon Dioxide and Oxygen getting back in.

Dave

Hello Kevin,

You secure it mechanically so that it is in good electrical contact