There was Franco- crosti boilers fitted to some of the British standard 9F 2-10-0. They where with the feed heater in the middle under the boiler. They also had a chimney for lighting up in the normal place. They where later converted to the regular setup.

Porta Boilers included a section in the front half of the boiler which would house a similar type of feed water heater.

It would be posible to fit a multiple Lempor to the side of a boiler like that.

Thank you Nigel Day for the insight on lempor exhaust system.

What I don't understand are the benefits of using this kind of feedwater heater instead of a more conventional approach. Why was something like this not adopted for use on more locomotives back in the day?

scott

In stationary practice, this device would be referred to as an "economizer". The purpose is to extract all the heat from the exhaust gases that you can. These devices added an additional level of complication, cost, and maintenance complexity to the locomotive, so often they were judged not to be worthwhile. The resulting fuel savings may not have completely offset the increased costs of the equipment. The Italian railways apparently decided that they provided a net benefit, but AFAIK there were very few installations outside of Italy.

What Hugh says is correct. The alternative way to heat feed water is by using some of the exhaust steam.

Any way these are the main points in designing such a econamiser from the combustion and evaporation point.

As you increse the length the gasses travel the temprature drops. With super heating you want a maximum temprature of 500 degrees C in the smoke box. If the temprature is to low in the smoke box then the full savings of super heaters are not gained.(You can cool super heaters if the temprature drop in the flues is to much.) BUT there is alot of heat left in the gasses after the smokebox which for eficentcy you want to collect. So a second section of boiler/ heat exchanger is used beyond the normal smokebox with no super heaters,to heat the cold water feed before going to the hotter main boiler. Thats what the big cylinders are and why they 'return the gas flow under the main boiler to a side stack. The problems of corrosion and then high maintainace are caused when the gasses temprature fall bellow 200 degrees C which allows sulpher to form sulphuric acids which corrode the heat exchanger. Obviously all this has to be taken into accout when designing such a sytem and the draughting to maintain the correct temprature drop through the boiler.

That reminds me- there was an article in either "Live Steam" or "Modeltec" magazine (both magazines for miniature "live steam" locomotives about 20 years ago about a "poor man's economizer" fitted to a Crown Metal Works 4-4-0 used in an amusement park.

The main water supply for the engine was a cross-head pump delivering unheated feedwater directly to the boiler barrel (there was a steam injector for backup). They fitted a large copper pipe coil (something like 2 inch pipe size) into the smokebox; the coil was formed to the inside diameter of the smokebox. Feedwater from the cross-head pump went through this and then into the boiler.

IIRC, they were able to raise the temperature of the feedwater substantially with the coil, which provided significant fuel savings and better steaming. It'd be interesting to know how the device worked out long term.