A move to condensing

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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PeteThePen1
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A move to condensing

Post by PeteThePen1 » Sat Apr 08, 2017 3:44 pm

Hi Colleagues

Having bounced off the 'Search' tool and been unable to find the wealth of information I know we have on the topic of condensers and hotwells I thought I had better put up a post.

The context is that I am overhauling Frances Ann and now have the boiler and engine mounted upon a trolley. So I will soon be in a position to weigh the 'empty' boat but that will get posted as and when it happens. What I am doing is trying to optimise the pipe runs which for very valid reasons, take some odd routes. With the plant out on the trolley access is easy and smoothing things will not be difficult. It also struck me that it was time to see if I could incorporate the condenser which is installed under the hull but not plumbed.

The engine is a vee twin so I have decided to follow the lead of Lopez Mike and others who have skipped the air pump and simply let back pressure push the condensate into the hotwell. I hope to re-find the thread on hotwells, but can state that I intend to fit a filter on the outlet from the hotwell to catch the final drops of oil.

I am uncertain what sort of float valve to use on the hotwell so suggestions would be welcomed. The pipe from the exhausts to the condenser will be 22mm OD but I think the pipe to the hotwell can be done in 15 mm OD. I probably will need to make a custom fitting to ensure that the outlet pipe goes to the bottom of the condenser end casting otherwise the system will deliver no water until the whole of the condenser is full of water.

There is a sea cock which I have drawn as supplying the hand pump and the injector. Not shown is the filter which I need to fit. There is also a reserve water tank in a locker but it is not very big. It would keep things going in an emergency for a short while only hence the sea cock supply. I am not sure whether to plumb it in to the engine feed pump so that the plant could be run in puffing mode.

Things I am dithering about include whether to try to include an exhaust steam feed water heater as there are points where the two flows are almost adjacent. Should I also consider what would happen if the feed pump failed (say the belt frayed and broke)? I guess in that case one would need to switch to puffing and the injector fed from the sea cock quite fast.

Anyway, here is version 1 of the design:

Image

(Apologies - my editing of the excess white space seems to have failed)
Regards

Pete
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Lopez Mike
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Re: A move to condensing

Post by Lopez Mike » Sat Apr 08, 2017 11:50 pm

I see very suitable float valves in what we call here, "feed stores". In other words, places where you can buy food and supplies for raising animals like sheep and horses. I believe you have those in G.B.? The animals, I mean. The valves are used to keep the water level up in animal watering tanks. Quite inexpensive.

Exhaust feed water heaters are simple and reliable as long as you provide a pressure relief valve just before the feed water reaches the feed water shut off valve. I have seen several feed water heaters collapsed by forgetting to open that valve. Most feed water pumps can develop rather high pressures when the output is blocked.

Now mind you I don't recommend that you follow my lead on this but it is a measure of what can be done. I've plumbed pretty much all of my water piping with ordinary rubber covered 1/4" I.D. air hose. And in many cases it is just clamped over the end of a 1/4" O.D. copper pipe with a very ordinary hose clamp. Or two when I feel especially virtuous. The exception is between the feed water pump and the boiler as the peak pressures can rise a lot when thing happen like forgetting to open the feed water valve at the boiler (Not again!).

The advantage of this, other than horrifying Fred and several others, is that the hose can be strung anywhere. It's all been running fault free for years with pressures up to 150 p.s.i.
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Lopez Mike
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Re: A move to condensing

Post by Lopez Mike » Sat Apr 08, 2017 11:52 pm

One more thing. I would be wary of installing any piping such that you cannot get to the joints when underway. Those are the points that will surely act up.
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TahoeSteam
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Re: A move to condensing

Post by TahoeSteam » Sun Apr 09, 2017 8:20 am

I would put the filter on the feed water intake rather than the condensate return. I might cause an extra unwanted bit of backpressure being on the discharge side. A shell and tube or some other heat exchanger would be quite beneficial, especially with the high exhaust temps of a single expansion twin. I'd certainly have a way to have your makeup water available for the engine feed pump, either by plumbing into the pump directly, or to the hotwell ( if you had vacuum it could be plumbed into the exhaust, pulling makeup water into the system that way). I'd also make the sea chest intake available to the engine feed pump as well. No reason to paint yourself in a corner by not making all water sources available for all methods of feeding the boiler.
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