The Steamboating Forum

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.

You could install an economiser near the top of your boiler and preheat the water before it goes in the boiler.We discussed this somewhere on this site at length but I can't find it. Den

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 should produce.
Regards
Jack

steamboatjack wrote:Condensing the exhaust to a high temperature would probably compromise the vacuum

Of cause the steam chart dose not end under 100°C!
You always have a direct relation between possible vacuum and condensate temperature.
Also this is the reason why hot water will evaporate when a feed pump try to suck it from deep tanks.
You create a low pressure in the pipe and for each given temperature you will have a relating evaporating pressure.

Thing about boiling an egg in high mountains - because of the low pressure it will boil with less then 100°C and will take longer to become cooked.

It's always the same water with the same habit - so you can use the steam chart from 4°C up to 400°C and more - to find out the pressure (or even so called vacuum) for the relating boiling (or condensing) point.

I have this chart posted in my shop:
www.boilerroomservices.com/Facts/SteamTables.pdf

Note the last row along the bottom at around 900 psi. This is where the serious stuff starts in some electrical power plants and a few military engine rooms. Critical Point. Not fun to keep the piping together!

I'm told that a small leak at these pressures and temperatures can travel several feet in the air before condensing to visibility. A first look for a leak is done with a broom. Supposedly the invisible jet of steam will slice the broom.

I'm afraid in my system I can almost report the conditions as they do in a weather report; i.e. Dew Point.