Steel boiler storage.

Hello all.

Appreciate there will possibly be no right or wrong answer so am just after some opinions.

How should you store a 3" steel boiler.

Empty.
Full to the brim with an additive, when do you know is properly full ?
Half full with an additive.

Thanks.

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

Brian,

I think the best choice of those you list is to store if full with treated water, making sure you don't leave air pockets. I recall this is the approach used at the Crofton Beam engine pumping station on the Kennet and Avon canal near Malborough.

They have a spare boiler stored outside; I don't remember if they use treated water for that storage but they would need anti-freeze which strongly suggests a corrosion inhibitor is included in the mix

Regards

Brian

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.

One Norwegian railway blows down the boiler with a little bit of fire left in the box and then opens a convenient aperture and inserts lighted candles to remove most of the oxygen. The boiler is sealed after putting in the candles.

I have seen this done and helped put in the candles, so it isn't a joke on my part!

Andrew.

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

Just a thought - for dry storage, warm the boiler w small fire, purge water/steam space thoroughly with argon or nitrogen, seal up with gas flowing out of all openings actively, and leave under slight pressure of the inert gas ie 5 psi. Check periodically that positive pressure is still there, during storage. If it's all inert gas inside, under slight pressure, no oxygen or moisture can get in, and so there should be no corrosion happening inside.

Edited By Jeff Dayman on 11/05/2019 02:22:27

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

Leave it full of water.

Bri

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

+1

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

Thanks for all the reply's, appreciate you taking the time.

Martin Johnson, whats the process to blow down ?

Do i just let the boiler pressure drop down to about 10 psi then open the valve and let it all out ?

Edited By Brian Abbott on 11/05/2019 23:36:04

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.

There was a very good article in ME by Silly Old Duffer not long back which went into prevention of condensation.

As Paul says, after blowdown, even if you get all the liquid water out, the boiler is full of hot air saturated with moisture. When this cools down a lot of this moisture will condense onto the internal surface, just what you don't want. To get corrosion you need both liquid water and oxygen, so filling the boiler to the brim with de-oxygenated water would seem lie a good route, if you have copper tubes then de-ionised as well sounds good to prevent bi-metallic corrosion. This however does nothing for the external surfaces, a boiler full of water will have a large thermal inertia and so changes in ambient air temperature and humidity could result in condensation on the outside. Is this a problem?

In my working life I came across similar problems, we finished up tenting the item and blowing in de-humidified air. I believe this is the solution used by SS Great Britain, although their problem is worse because of the presence of chloride ions, see SS Great Britain

SOD's article went on to describe a control system which would switch on/off a dehumidifier as needed, you only want it when the dew point of the air is above the temperature of the steel. I think you could use a heater to warm the steelwork , but then you'd need insulation.

To summarise, if it were mine I'd build a reasonably air tight storage box for the whole engine, put a dehumidifier inside and build one of SOD's controllers. A halfway house which should deal with internal corrosion is to dehumidify the inside down to some level where the dewpoint is below anything it will actually see, and then fit the dessicant breathers I mentioned earlier

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

So, I'm new to this, how do you make sure the sacrificial Zinc is electrically connected to the steel, and does that mean you run a current through it?

Hello Kevin,

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

It's called cathodic protection and is very important in the marine world. The electrical connection has to be very low resistance as the driving voltages are very low.

Tim