Rust entrained in steam

[JonRiley56]

All,

First some history........ The earth cooled...........fast forward....my water tube was built in 1996 but never installed and steamed until I got it last year. It has seen limited use since then, only fired 10 times or so as I try to figure other stuff out with the boat.
It has black iron mud drums, down comers and steam drum, and the tubes are stainless steel.

I just sent my little southworth pump back to Ron for some tweaking and he commented that there is fine rust in the steam side of the pump. it is made from bronze and stainless, so it must be coming with the steam. I have also noticed that my condensate return is rusty.

I am using copper on all of the feed water piping. I have some black iron pipe in the steam supply to the engine, and also in the exhaust before it hits my condenser.

It is likely that I am "descaling" (too agressive a term..but the only one I've got) the boiler. It sat for a very long time and liely everything save the stainless developed a layer of rust. The other possibility is that I am picking it up in my piping.

Any thoughts ? Assuming I am getting it from the boiler, is there such a thing as a sediment filter for steam ?

thanks in advance for the help, desperately trying to get it put back together before Lee's Mills.

jon

[marinesteam]

Stainless can and does rust, after all it is steel. If the rust is showing up on only the stainless parts there may have been enough free iron on the surface and that in now showing up as rust. If it's also on the bronze, it's probably from an external source,

Ken

[fredrosse]

Boiler drums will rust, but if there is no water caryover this should not put rust into the steam. carying a high level water level can lead to carryover of some rust. Steel piping will rust also, but I have not noticed any problem in three years running with 1/2 inch steel piping from the separator tank to the engine, about 6 feet total length. The low portions of the piping are blown out during warmup to get rid of condensation here, and that will cary away rust particles. I do not use a strainer on the steamboat engine inlet, but on large steam turbines a strainer screen is often fitted. There are suitable strainers that come up on ebay frequently, with 150 PSI SWP rating. Get something with 60-80 mesh stainless screen. 20 mesh is typical, but that is too coarse for catching small particles. I have a 60 mesh strainer on my feed pumps' suction, that finally started to restrict the feef pump suction after 3 years. Cleaned out about 2-3 cubic inches of rust crud, all of it was formed in my carbon steel 15 gallon feed tank. From now on I will vacuum the tank clean every season.

I do not think a little rust is an issue for a larger slide valve engine, but would suggest you blowout the steam line with compressed air, or better yet, steam, before directing steam into the engine. A tee fitting just upstream of the engine throttle valve, with a manual blowoff valve (discharging to atmosphere) would be an easy installation. Plug the blowoff valve during normal operation, so you or a passenger will not accidently let off steam. The same setup can be fitted to the steam pump, which probably has smaller moving parts. Large steam plants do this setup for initial commisioning, to blow out all high pressure piping, but not as an annual event.

[JonRiley56]

Thanks Guys,

I have been carrying the water higher than in the past, it seems to make the whole system more stable. I have a steam dome on top of the steam drum and the main steam line comes out of that. I was figuring that my chacnes for carryover were limited with that set up.

Fred, on putting the "line clearing" valve in the steam line ahead of the engine: Could I just bring the stephenson gear to the middle, essentially covering most, if not all, of the port area in the steam chest, open the dreain valve on the steam chest and then crack the steam valve ? The condensate with any rust etc would then go into the steam chest and be forced out through the drain. If I put a valve ahead of it as a dump I will need to pipe it down to the floor so I dont blw snotty water everywhere. I already have plans to do that with my steam chest drain, I am putting in a gate valve plumbed to the bilge.

On the strainer, I saw them on the web and was wondering what size mesh I should get, thanks for the 60 to 80 recommendation. I noticed that it said some of them are "self cleaning" if you open the plug on the bottom. ( I would put a valve there). Does that work well ? I was thinking maybe I should put one in line ahead of my engine/pump steam valves, but dont want it to blind and plug up on me with no way of cleaning it while I am out.

As usual, thanks for the help !

jon

[barts]

I have a strainer on the main steam line and one on the burner. A ball valve on the cleanout means it only takes a few seconds to clean the strainer.

- Bart

[JonRiley56]

Hi Bart,

So basically you just crack the valve on the cleanout port and the steam blasts the build up off the screen ?

jon

[barts]

Hi Bart,

So basically you just crack the valve on the cleanout port and the steam blasts the build up off the screen ?

jon

Yup - seems to work fine, too.

This is the sort of thing: http://www.mscdirect.com/browse/Hose-Tu ... 4288031923

- Bart

[JonRiley56]

Hi Bart,

I got my strainer yesterday. If I put this as close to the steam valve on my engine as possible and have a valve on the cleanouot port that I can open, can it act as my way of dumping the steam line of water when I am starting up ?

jon

[fredrosse]

If you have just a blowdown valve on the strainer near the steam chest of the engine, then the valve should be plugged while underway, so that there could be no accidental opening/discharge of that valve by yourself or a passenger.

If you routinely blowdown the strainer, then there should be piping leading from the blowdown valve to a safe place, overboard, into a vented water tank, etc.

[JonRiley56]

Point well made Fred !

jon