TSP in the boiler water

[dhic001]

Dry lay up of the boiler is very easy, and takes less than an hour, most of which can be spent doing other tasks. I come in from my run, berth and then pull what little remains of the fire and throw it overboard. The few remaining coals around the edge of the grate aren't an issue. I then either wait for the boiler pressure to drop a bit, or put the injector on and drop the boiler pressure to 40psi or thereabouts. I fully open the blowdown, and let it empty the boiler completely, leaving it open for a couple of minutes after the end of the blowdown. I open a vent at the top of the boiler (normally the whistle) and light a couple of bits of newspaper in the firebox. This drys the inside of the boiler out well, and to test put a mirror or piece of glass by the vent. If there are no water droplets or vapour forming on the glass, you know its completely dry. Then close all fitting tightly, put funnel cap on and close firebox up. As the boiler cools, it will actually form a vacuum inside, but because the boiler is completely sealed, no water will be able to get in. Provided your fittings are good and tight, you can leave it like this for years, and when you open it up, there will be absolutely no water inside.
Simply the best form of long term storage.
Daniel

[bushbuck]

A thought... Why not pump nitrogen into the boiler when not in use. I use nitrogen in my furnace that is used to heat treat knife blades to minimize oxidation. Nitrogen can be purchased in gas bottles at minimal cost. Nothing can then rust due to absence of oxygen.

[Ofcalipka]

What type of fitting are you using to fill the boiler with nitrogen and how can you be sure you've removed all the oxygen? I plan on using my new boat at least once a month so I don't think nitrogen is practical for my purposes at the moment.

[bushbuck]

I dont have a boat yet but talking from experience of other things. I get nitrogen from our local tyre shop in an old gas bottle. The gas bottle is pumped to 6 kpa and then from the bottle pumped into my furnace with a tyre inflator usually used on my compressor. I just adapted a bull nose to take the tyre inflator. The nitrogen is introduced into the top of the furnace after a small valve is opened at the bottom to exhaust oxygen with a vacuum pump. The nitrogen thus occupies a vacuum. I doubt that all the oxygen will be excluded. I am assuming that maybe with an environment saturated with nitrogen, the likelihood of oxidation is minimized. I can see the difference on knife blades heated in normal atmosphere compared to those in nitrogen, oxidation is much less. That's why I headed the comment: 'A thought". I am sure that some of the boffins on the forum will have an input.

[fredrosse]

From a previous post on this forum, this would be the "Cats Meow" method for layup, keeping the proper water level in the shutdown boiler, and an inert purge gas at a pressure slightly above atmospheric which would assure no corrosion:

Nitrogen is the best “blanket gas” to keep Oxygen out of a boiler that is not completely water filled. Nitrogen is much cheaper than Argon, and slightly lighter than Air, so it will not tend to accumulate in low bilges, etc. The Argon remains inert even at welding temperatures, but the Nitrogen can be considered as an inert gas for the temperatures we encounter within our equipment, up to several hundred F or C.

Nitrogen is used to fill our new heat exchangers in shipment, to prohibit entrance of Air and Humidity, which would cause rust. A heat exchanger, maybe 5 feet in diameter and 50 feet long will have a small (20-60 SCF) high pressure bottle of Nitrogen attached, with a regulator set at 1 PSIG to preclude the entrance of air. The Nitrogen is added at the factory, and the small bottle is used to keep the pressure slightly positive during transit and storage.

When filling with Nitrogen, a generous purge flow is needed to wash out all the humid air from a vessel that is initially filled with air. Alternately, if you can draw a high vacuum on the vessel to be protected, then fill with Nitrogen, no purge is required. Also, if the Nitrogen supply is initiated before the boiler cools below atmospheric pressure, no purge flow would be required, and no Oxygen would be present.

For a steaming boiler, all of the air (and Oxygen) should already be purged out, so attaching the small Nitrogen bottle with regulator set at 1 PSIG will need no purge, thus conserving the Nitrogen. As the boiler cools and approaches 1 PSIG conditions, the regulator will start to feed Nitrogen into the boiler as required. A good (Swagelok or similar) check valve should be installed in the Nitrogen feed line to prevent steam pressure (when the boiler is again fired and pressure rises) from flowing back to the regulator when steam pressure is above 1 PSIG. Tubing of 1/4 inch OD or even smaller is big enough for this job. Alternately, the Nitrogen regulator should be a non-bleed type (if pressure goes above the regulator setpoint, it will not vent off the discharge side of the regulator) to keep the hot steam away from the regulator, which is probably not rated for the steam temperature.

[bushbuck]

Very interesting indeed!!

[Ofcalipka]

I like the idea of nitrogen layup but am thinking of what I have on hand first. I have an argon tank for welding and if I fit a phuematic chuck to the adapter I have for running the engine on compressed air for maintenance I could back fill the boiler easily this way after everything has cooled down. I think this would be about as safe and easy, and cheap one could hope for while still being effective for layup that will prevent rust without any really special equipment.

[fredrosse]

When a boiler is closed up, if all valves are perfect, then the gas space within the boiler would remain unchanging. However many valves leak a little, according to the differential pressure applied, and the fluid that is leaking. A valve that leaks just a bit of water will usually leak gas more easily.

If, after steaming, you close all boiler valves, then when the boiler cools down a good vacuum will form. If the valves are leakproof, then the vacuum will stay until you heat the boiler up to 212F (100C). This is an ideal condition, and would protect the boiler internals from any corrosion, as no Oxygen would get in.

If you lay up the boiler hot, have the vacuum form, and after a few days the boiler has lost much of its vacuum, then air is leaking into the boiler, with corrosion products forming.

With an inert gas purge, if you pressurize the boiler with inert gas, and can keep the pressure positive throughout the layup, then no Oxygen can get in. But if there are some valve leaks, the inert gas will eventually leak out until the boiler internals reach atmospheric pressure. Then the normal temperature variations day by day will cause the gas inside the boiler to expand and contract, and cause the pressure to go up and down, breathing in air each day. So this all depends on how much your valves leak, compared to how much excess inert gas you have available.

With the small 1 psig regulator, an inert gas supply cylinder can last a long time, because the differential pressure leaking out of the boiler is very low, but constantly keeping the Oxygen out. The other method, filling the boiler to, say 100 psig with inert gas, (with no regulator) will promote high leakage initially, and pressure will fall over time, eventually leading to the “breathing air” mode.

Not to say that the high pressure inert gas will not work, but it is likely that it will admit air into the boiler much sooner than the inert gas regulator method

[Ofcalipka]

Wouldn't occasional checks of the boiler pressure guage let us know if the Argon or Nitrogen was leaking out and if it starts to look low we could just connect up the tank add a few PSI and good to go for a while longer? I don't plan on parking it for several years and forgetting about it as corrosion could and would still be attacking all the external bits anyways.

[fredrosse]

Yes, in that case YOU are essentially being the regulator. How often and how much gas to add again depends on the leak rates, which are highly variable. In my experience the safety valve is often a leaking valve, and you are not pernitted to remove or plug that valve.

For me, wet layup with deaerated water, filling the boiler completely with liquid, is the easiest path, but I will consider the Nitrogen regulator setup, certianly better, depending on how long the nitrogen bottle stays charged.