Hot well size

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smokestackmag
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Re: Hot well size

Post by smokestackmag » Sun Jun 18, 2017 5:18 pm

A few years ago I was very unhappy with my hotwell. It was shallow and didn't have enough volume. I found a SS cylindrical tank 30" high x 9" diameter at the local thieving junkyard. That does very nicely. Have not run it dry. And, with it fairly full, it will always provide a good positive head to the FW pump. As far as heating the hotwell goes, I don't. I did manage to mount an open ended coil in it and went so far as to have a live steam FW heater piped in with the exhaust from that going to the coil in the hotwell. In the meantime, I had also made and installed a waste steam FW heater at engine exhaust and that was doing a fine job of heating the FW post hotwell and FW pump. I removed the live steam FW heater and now the only thing going to the coil is the waste steam from the Windermere Kettle. The condensate always comes back as cold as the water I'm steaming in.

A thought here.... What about floating something on top of the water in the hotwell to limit the contact with air? If there's nothing in the way this might be a solution. This is something I could do which would be more manageable than the aforementioned extra FW heater and the coil.

I'm interested to hear comments.
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Re: Hot well size

Post by fredrosse » Sun Jun 18, 2017 6:23 pm

Floating tank covers to preclude contamination have been used, and a vertical cylindrical tank is ideal for this setup. Even better, with a accordion style rubber diaphragm over the water to fully separate the water from the air. There are floating beans, plastic, and about 1 inch diameter, sold specifically to reduce air contamination, as well as heat loss from the surface of water. A reliable screen in the tank bottom is absolutely necessary so the pump absolutely cannot be clogged (famous last words).

In power plant practice, any temperature below the saturation temperature of the exhaust steam is called "condensate depression", and it is to be avoided, as the return condensate, at a lower temperature than the condensing temperature, needs to eventually be heated more than it would theoretically need to. In marine steam plants and electric utility stations (10,000 to 1,000,000 horsepower variety), the condensate depression is generally around 1 degree.

At 20 inches vacuum, the condensing temperature is 157 F, and the condensate should be above 150F, but our steamboat condensers, especially the keel cooler types, often make for much more condensate depression. The penalty for this condition is generally small.
smokestackmag
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Re: Hot well size

Post by smokestackmag » Sun Jun 18, 2017 6:41 pm

fredrosse wrote:Floating tank covers to preclude contamination have been used, and a vertical cylindrical tank is ideal for this setup. Even better, with a accordion style rubber diaphragm over the water to fully separate the water from the air. There are floating beans, plastic, and about 1 inch diameter, sold specifically to reduce air contamination, as well as heat loss from the surface of water. A reliable screen in the tank bottom is absolutely necessary so the pump absolutely cannot be clogged (famous last words).

In power plant practice, any temperature below the saturation temperature of the exhaust steam is called "condensate depression", and it is to be avoided, as the return condensate, at a lower temperature than the condensing temperature, needs to eventually be heated more than it would theoretically need to. In marine steam plants and electric utility stations (10,000 to 1,000,000 horsepower variety), the condensate depression is generally around 1 degree.

At 20 inches vacuum, the condensing temperature is 157 F, and the condensate should be above 150F, but our steamboat condensers, especially the keel cooler types, often make for much more condensate depression. The penalty for this condition is generally small.

Whooops! Sorry! First time I hit Quote. I guess I'm supposed to highlight. Anyway, to reply to Fred's answer (the last sentence), that's what I thought.
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Re: Hot well size

Post by Lopez Mike » Sun Jun 18, 2017 7:47 pm

Good ideas. Thanks.

I am much in love with my float valve in the hot well so the various schemes to seal the surface of the water from the air might prove awkward. I could close in the top above the float but observation of the conditions in there have proven helpful. When there is any malfunction, fortunately rare these days, it manifests itself in some sort of change right there such as a level variation or excess steam from the condenser output.

Smokestackmag. Do you any system of automatic regulation of either the hot well level or the boiler level? Of not, do you have to fiddle much with any manual adjustments?
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Re: Hot well size

Post by smokestackmag » Sun Jun 18, 2017 8:42 pm

To your questions, in order....

No and yes. I've wanted to fit a float valve but never got it done. And, to the fiddling.... some days I hit it just right and steam for hours with no input. Other times I'm messing with it every 10-15 minutes. But, at least I have something to do.
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Re: Hot well size

Post by Lopez Mike » Sun Jun 18, 2017 9:45 pm

The last thing I'm looking for is something to do.

Most of the time I'm hauling passengers and between keeping them from either falling overboard or sticking their feet in the engine, trying not to run aground or hit another boat or a dock, feeding the ever hungry firebox, answering questions like, "What do you use for fuel?" as I'm holding a hunk of wood in my hand, and I forget what else, dealing with one more control isn't welcome.

I really like watching other people with multicylinder engines and lots of auxiliary machinery deal with their boats but I'm rather busy.

There is a tug boat race in a couple of months near me that I always attend. I also have a medium sized mortar that I loan to the organizers to signal the starts. This year they are telling me that they are having a hard time finding a cannon boat and could I take care of that function please?

Let's see. Loading a cannon with open containers of black powder on a 24 foot boat that it sort of on fire anyway. What could go wrong?

I am looking into pre-sealed 1/2 pound packets of powder. That way the exposed handling of the explosives is done ashore and all I will need to do is poke a wire up the hole from the percussion cap to the chamber after loading. This, of course, leads to a discussion of whether the bow will fall off, not a trivial issue on this particular hull. I suspect a sheet of plywood over an inner tube might delay the inevitable catastrophe.

As Gene Romero said in On Any Sunday, "Wish me luck. I love Gardenias!"
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Re: Hot well size

Post by barts » Mon Jun 19, 2017 2:28 am

I often like to run Otter at the dock while I'm debugging various issues - usually air in the feed pump and the like. This results in reduced water flow over the condenser, and increased hot well temperature. In addition, sometimes I run the boat in the San Juans, where the water temperature is somewhere in the mid 50s F. Other times, we're in the San Francisco Delta and the water temperature may be in the 70s. All of this means the hot well temperature wanders around from perhaps 65F to 120 F or more. I'm happy to have the temperature lower, and rely on the feed water heater to pre-heat the water before it goes into the boiler.

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Re: Hot well size

Post by Lopez Mike » Mon Jun 19, 2017 2:52 am

Yeah. Feed water heater is in my future.

That helps with the efficiency issue but doesn't help with the problem of dissolved oxygen.

I try to keep a decently low pH in the boiler with some TSP from time to time so I'm probably not hurting anything.
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Re: Hot well size

Post by barts » Mon Jun 19, 2017 4:56 am

Lopez Mike wrote:Yeah. Feed water heater is in my future.

That helps with the efficiency issue but doesn't help with the problem of dissolved oxygen.

I try to keep a decently low pH in the boiler with some TSP from time to time so I'm probably not hurting anything.
Yup. TSP, and when I store the boiler it's filled w/ water straight from the supply (it doesn't freeze where we live).

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Re: Hot well size

Post by Lopez Mike » Mon Jun 19, 2017 5:12 am

When I shut down for more than a month or two I blow down hot while there are still some coals in the firebox. When the last whiff of steam exits at the whistle I close up tight. If I'm shutting down for the Winter I throw a small heater or a large light bulb in the firebox for a few days and then close things up.

It freezes here so I go over the entire boat piping system with my shop vacuum so there is no trapped water to bust things. So far, so good.

I do the same thing with the house in the fall when I leave for Baja. No water in anything and the main circuit breaker turned off. Dead house.
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