The Steamboating Forum

Please could I mine your collective wisdom on hotwells? I am sure we have a detailed section on the topic, but my skills with "Search" seem to be rubbish today.

Initiating this topic on the SBA forum, the general impression that emerges is that one should have as big a hotwell as possible, probably equal to the boiler contents and then at least three compartments that have oilsorb mats to keep the nasty stuff oil out of the boiler.

Frances Ann, being a tiny Rose hull has very little spare space, so any solution I build is not going to be up to the SBA gold standard. I have a rectangular bain marie pan that might do nicely, at least from a size point of view (about a gallon) and could rise to two compartments.

However, the main steam line to the engine goes from the dome (150 psi max) directly to the engine in perhaps three feet of pipe. It strikes me that the steam should not have cooled that much but, as there is no superheating coil, is is basically warm and wet. I have also read somewhere that running with wet steam, there is really no need to lubricate the cylinders. If that is true, then should I not give up oiling thus removing the whole reason for having a big multi compartment hot well?

It seems such a simple solution that I feel that there must be a snag somewhere.

Regards

Pete

Pete,
I am not an expert, but I understand the Waverley relies on the water condensed from the steam for lubrication.

Many large marine steam engines worked with wet steam as the only cylinder lubrication, but close control af many parameters is needed. The Waverly, as well as the 2700 Liberty Ships built during WWII are examples of this condition. Often constrained (non-expanding) piston rings were used, as the typical split rings are forced against the cylinder with steam pressure, (acting on the inside diameter of the ring) and that condition is too high a contact pressure against the cylinder wall for water lubrication.

For a small launch engine, running at high pressure and high temperature steam (say 150 PSIG, 358F saturation temp), the cylinder and passages attain a temperature corresponding to "hot running". When the steam throttle is closed to slow down the launch, the cylinder pressure (and saturation temperature) goes down, and the hot cylinder walls (and hot slide valves) evaporate wetness, the cylinder (and valve surfaces) run dry, and they begin immediately to squeak and groan, asking for oil. When shutting down after a days run, cylinder surfaces, if free of oil, will rust overnight, and might seize the engine. Rust particles in the cylinder are also not good for cylinder wear. Hence it is good practice to give the cylinder a shot of oil when coming into a dock.

A key element here is to use very little oil, as separation of oil from water is difficult at best. Compounded oils, the kind that are so ideal for steam cylinders, is almost impossible to fully separate from water. Pure mineral oil will separate more easily and fully, but finding pure mineral oil is not easy. I use pure vetenary mineral oil, at least I know I am buying pure unadulterated mineral oil.

Do not use automotive oils, they all have detergents that form an unbreakable emulsion with water. Even automotive oils that are labeled "non-detergent" are indeed not, they are just labeled that way because they failed the detergent specification, but still will form unbreakable emulsions.

To expand on what Fred said, from a practical standpoint, it is wise (and a lot quieter!) to use oil, but it must be very little, and exactly the right thing. The Blackstaffe compound in my old Reciproca is equipped with a mechanical lubricator, set to deliver about 1/8 teaspoon of oil per day, just enough to prevent loud squeaking when throttling back. Also, the right oil is critical. Steam oil commonly used by non-condensing folks will laugh at any type of hotwell filter. I use Green Velvet PB&J 460 for steam oil, easily available here http://www.steamenginelube.com/lubeuse.html#pbjAll. I used Bounty paper towels as a filtering medium in my hotwell, and the cleanliness of it and the inside of my boiler couldn't be missed after the switch to PB&J.

I have a fairly small hot well. Perhaps less than a gallon. I don't use any cylinder lubrication on my 3 x 4 piston valve single. 140 p.s.i. max. pressure.

I have some Oilsorb pads wrapped around the ends of the suction lines for the two pumps. I have a cylinder of 1/4" galvanized steel mesh inside the wrapping of Oilsorb. I change them when they look horrible. The water is always clear with no oil film of course.

I had a squeak but it turned out to be the valve packing that had gotten loose and was chattering. I do have an occasional squeak on throttling back but it goes away after a short time. I look at my cylinder walls several times a year. They are always black and glossy.

The piston valve rings do tend to stick from being dry after a night or two. In my case, the upper valve and cylinder heads come off easily so I spray whatever I have in there and spin the engine over. When storing for the Winter I slather a bunch of chain saw bar oil inside the engine. Never sticks.

I use the bar oil for my external lube. Tough stuff. And cheeeep!

If not wanting to use 'wet' lubrication. Is there anything in the dry form that might ease the problem? I'm thinking of something like Teflon or Molybdenum Disulphide. Ordinary graphite would wash away. I believe the motor trade have experimented with Teflon coated rings and bores, may even be using them widely.

We've done a bit of experimentation with colloidal graphite in "Persistence" just suspended in water in a conventional pump lubricator. It lubricates VERY well in our limited experience so far. Problem is keeping it in suspension in the water requires occasional agitation. Also it will cake up where it doesn't completely enter the steam stream. I've read in the "Funnel" of others using it, but after much research I haven't seen any in-depth "how to" articles (maybe I missed it? I thought there was one or two I had read before!).

We will be doing more experimentation with it in the future.

You might also take a look at the article on Electrocoagulation article in the May/June 2015 issue of Steamboating magazine.
This is actually very simple, with an aluminum anode and a stainless or iron cathode and a few milliamps 12V DC causing
clumping and separation of the the oil from the water.

Something like this combined with a good Oil-sorb based filter and a non-compounded steam oil dispensed very
sparingly might well provide a pretty reasonable solution to the lubrication problem.

http://www.steamenginelube.com/orders-0 ... 20Cylinder

- Bart

Bart, I did not see that article...

Whats the potential for that method to speed up electrolysis in our marine environment?

TahoeSteam wrote:Bart, I did not see that article...

Whats the potential for that method to speed up electrolysis in our marine environment?

Well, I don't really know. However, given that this is basically grounds the hotwell to the = terminal
of the 12V source only when the plant is operating, I would guess this has little practical impact.

Those very worried about this sort of thing could use a isolated 12 V source (a tiny separate
12V batttery would work well).

Your mileage may vary.

- Bart