Pre heating boiler water

[19copythree]

I have a 3/4" New Haven I-1 Pacific, built in 1938. It has pre-heater coil (three coils) in the smoke box
. It couldn't be simpler. No maintenance. No fuss. No Muss.

[michaellynn2]

Do coils in the smoke box make it hard to clean the flues??

[Bill Shields]

yes and no - the connecting piping can be annoying to layout and install, but if properly done should not get in the way (too much).

Attached is a photo of another way to do it.

[NP317]

I like that side mounted heater!
~RN

[B&OBob]

Thanks for the photo, Bill!
George Thomas, my father, built a free lance 4.75" 2-4-0 in 1966 that incorporated the smokebox feedwater heater shown in Bill's photo. The pre-heater consisted of the six or seven tubes about 4" long between two headers on the left side of the smokebox. It was connected between a water entry point in the bottom of the saddle where water entered the smokebox from the axle pump, and a smokebox tube sheet fitting. Did it do any good? Who knows -- the boiler is such a prodigious steam generator it didn;t matter! Thus when the original boiler failed at a firetube joint in the smokebox tube sheet, it was replacd by a new one generously built built by Bill Shields to essentially the same design of the original except for absence of the preheater and some of Bill's upgrades. No practical difference between performance of the new boiler compared to the original one could be detected; they both steamed like the dickens! The original preheater did not interfere with tube cleaning because it was completely out of the way. Additionally, Welsh or anthracite coal was always burned in this locomotive, so there was no accumulation of oily ash; flue cleaning was by use of an air lance made of 1/8: stainless tube from the firebox end.

At the risk of straying off topic, this locomotive is distinguished from typical layouts by a unique chassis/boiler design that permits separation of the boiler and chassis simply by removing four bolts in the saddle, and three at the drag beam. Feedwater, steam to cylinders, and exhaust, all pass through a flat interface joint in the saddle -- there are no other chassis/boiler connections. Water from the tender to the injector, 2-cyl axle pump and a VanBrocklin simplex pump are made directly to hose connectors on the boiler itself. Southern valve gear is controlled by a rotary hand wheel conveniently located at the back of the tender driving a flexible shaft to the chassis through a keyed sliding coupling to a screw reverser on the chassis. Cylinder drain cocks are actuated by a small single-stroke cylinder mounted on the smokebox (seen at right in the photo); a piston rod from the cylinder presses against a lever from the cyl cocks to actuate them. This design allows for assembly or removal of the boiler in five minutes, leaving the chassis completely free for cleaning, lubrication and conveniient one-man handling for transportation. It is not a superscale design, but it sure is convenient - especially when you get to be older than 65!

B&OBob

[Bill Shields]

something like this:

If it works...build 2!

[Berkman]

Any photos michaellynn2? Would love to see it!

[RET]

Hi,

If you look at the numbers, preheating boiler water doesn't do a lot for efficiency in our models, but if you want to be true to prototype, go for it!

Those of you with an engineering background will know that it takes 512 calories of heat energy to turn one gram of water into steam at atmospheric pressure. However, it only takes one calorie to raise one gram of water one degree centigrade. If you assume 20 degrees centigrade to be room temperature (a bit low, but it makes for easy numbers), then 80 calories will raise one gram of water to the boiling point at atmospheric pressure.

The numbers change a bit at higher pressures, but from this you can see that the major portion of the heat input is used in turning water into steam, not in warming it up. In real life, railroads were looking for every bit of savings they could find, so if you could preheat boiler water with waste heat and save a bit, it was worth it, especially when you were dealing with a steam engine that was probably only about 10% efficient on a good day (power output vs.heat energy input).

Just something to think about.

Richard Trounce.

[michaellynn2]

On my Southern Ps4, it does preheat the water very efficiently. If a pause is made in pumping tender water into it the feed water heater, the feed water heater becomes far too hot to touch. I have a check valve between the pump and the feed water heater in case the feed water heater begins to reach a boiling point, the expanding water will inject into the boiler and not feed back to the pump. Most of this heat comes from the smoke box gases heating the bottom of the heater body. This prevents a temperature shock of cold water being added to the hot boiler........... As far my posting pictures I am not sure how to do it and not get a nasty gram from Harold.

[michaellynn2]

Here is a photo I hope

[Fender]

One potential benefit of preheating the water before it goes into the boiler would be to drive out the dissolved oxygen. As the water temperature goes up, the ability to hold gases in solution goes down (chemistry 101). But the gases need to be released to the atmosphere before the water goes into the boiler.

[Berkman]

I think both the prototype elesco and worthington systems had some sort of venting on them. Without looking at drawings I'm not quite sure how it was arranged.