temperature of your hot well?

[wsmcycle]

What is your hot well temperature? I don't currently have a closed loop system. I suck up water from under the boat for make-up. It seems that it would be a nice advantage to put hot water back into the boiler and I wonder how hot the water could be and still have condensed in the closed system.

[Lopez Mike]

Others will surely chime in with numbers. I can tell you that, indeed, you do save some energy by feeding with warmer water.

The high limit depends on the amount of head on the suction side of your feed water pump. A near 212 F temperatures you cannot suck at all without vapor forming. This will cause almost any pumping system I can think of to stop working or slow way down. You could put the hot well above the pump and run some pretty high temps but it probably wouldn't come to that anyway.

I have stuck my finger in a number of hot wells and they varied from cold at a fresh start up to past edge of Ouch with a small hot well and a hard working boat. Most of us worry a little about letting the hot well get too hot but I haven't personally experienced pump malfunction from this cause. Debris in the check valves is entirely more common.

Don't forget the advantage of controlling the chemistry and purity of your feed water. Not all bodies of navigable waters are created equal. I don't like to put things in my boiler that I would be squeamish about drinking. Stuff tends to accumulate in there! You are, after all, running a distillation plant.

[steamboatjack]

The Hotwell should ideally be as hot as possible to drive off oxygen (about 90degC) however this does present other problems, mainly the fact that the feed pump suction low pressure could cause the hot water to vaporise and not all pumps are made of materials suitable for these temperatures. Condensing the exhaust to a high temperature would probably compromise the vacuum and could affect the air pump in a similar way. As usual with all things steam boating there is generally a trade off.
In the lake district we don't bother with such things, drawing straight from the lake and exhausting up the stack to keep the coal bright, this some way compensates for the extra power which a condensing plant produces.
Regards
Jack

[Lopez Mike]

Boy, Jack, I wish all of our steaming was done in such nice water as yours. I have seen water going into boilers around here that looked like soup stock. And then the stuff coming out at blow down time. Wow!

So do you have oxygen problems with lake water feed? And how can one deal with it? It would seem as though adding chemicals would be futile as they would go up the stack.

I've seen what the insides of locomotive boilers get like but they are well equipped with clean outs and it takes a remarkable amount of cleaning to keep ahead of things. In many areas of the U.S., the dissolved solids are so bad that tea kettles get choked up in no time. My own well water here is unfit for coffee. Since I don't lubricate my little boat engine, the only decent water I possess is in my boiler!

One trick used in U.S. locomotive service on hard water areas was to introduce the feed water into the top of the boiler through the steam space. It was asserted that doing so caused the solids to separate out in a softer form thus making it easier to dispose of them by blowing down.

[Mike Rometer]

It's not a lot different here in the Uk Mike, depending on where you live. Round here tap water is pretty hard (there are worse places), Scotland usually gets soft water. With regards water treatments it's generally a misconception that they go up the flue, most of it stays in the boiler as it has a higher boiling point, and then if you add more with the feed water the concentration goes up. Most full size steam railways don't bother treating at all as it is difficult to keep in check, and just rely on blowing down very regularly and washing out at intervals. Miniatures tend to blow down dry after each sesion.

[Lopez Mike]

Aha! I hadn't thought of the fact that the treatment chemicals might have a higher boiling point and might accumulate.

I store my boat boiler dry. I do a fairly hot (less than 10 p.s.i.) blow down and then burn a bunch of paper to dry it out all the way.

A somewhat more difficult problem for me is to get all of the water out of the piping, pumps and check valves. Usually I do O.K. but once in a while I miss a small pocket and lose a check valve lid or something in an occasional freeze.

I've thought about using some sort of antifreeze but I have visions of some sort of Nobel prize winning discovery in my boiler from left over exotic chemicals.

[wsmcycle]

I have a hand pump in my boat but I mainly rely on my injector to replenish the boiler. I think from what y'all have told me, a first step would be to install some tubing above my FT boiler to preheat the makeup water some. Thanks for the responses.

Regarding your closed systems I have a few holes in my understanding. I can see running the engine exhaust through a counter-flow heat ex-changer and condensing the steam. What I don't understand is how a pump could pull a continuous vacuum on the exhaust side without being almost continually cavitated. And, how could the condensation be so complete that no pressure builds up?
Thanks

[Mike Rometer]

I would suggest, be careful relying on an injector from a hotwell. They do not like hot feedwater, becoming increasingly more difficult as the temp rises.

[DetroiTug]

"install some tubing above my FT boiler to preheat the makeup water some."

Referred to as an "economizer". Of all the tweaks that I did to my Tug last summer, adding one of those in the smokehood had the largest effect. Went from losing pressure taking on feedwater to maintaining pressure while taking on feedwater. And this is just 15 feet of 3/8" copper. Going to replace it with 21 feet of 1/4 iron pipe in a pancake coil. Should do even better.

Nothing more annoying running the boat than closing the bypass and watching the pressure gauge drop with a good fire going.

-Ron

[Lopez Mike]

No one has, so far, responded your comment about condenser vacuum so I'll chime in.

Many of us use a keel condenser. The condensation is very complete in these units. The condensate is often at 'sea' temperature so pulling a vacuum is quite possible without serious problems with state changes.

There are certain things that will help. Having the condensate pump suck from a low point in the condenser is important.

In my case, I have a non-compound engine and I simply let the engine exhaust pressure displace the condensate from the keel condenser to the hot well. With a compound engine, any vacuum you can provide on the output of the low pressure cylinder helps significantly.

As Ron has noted, an economizer is well worth the trouble. It is, of course, after the feed water pump so creating vapor due to low pressure is not a problem. Your injector is largely its own economizer/feedwater heater so it is usually piped directly to the boiler.

I have only had injectors malfunction for two reasons other than obvious things like loose piping. Either the feed water to it is too hot or there is foreign matter in the nozzle. Installing a non-lifting injector high in the system is an occasional error.