I would like to know what are some of the methods you folks use for cooling down your boilers when you don't have the time to let them cool down on there own, due to a 31 day. I have used the CN method where you "cycle" the water over night and the side sheets are cool enough to touch in the AM. Some folks claim this is to hard on the boiler and I was wondering what others do.

> I would like to know what are some of the
> methods you folks use for cooling down your
> boilers when you don't have the time to let
> them cool down on there own, due to a 31
> day. I have used the CN method where you
> "cycle" the water over night and
> the side sheets are cool enough to touch in
> the AM. Some folks claim this is to hard on
> the boiler and I was wondering what others
> do. i am not sure how the cnr did it however there are many details inthe railway age of the 1940s. they all seem to think its not how fast you do if but how evenly. i like the way the up did it they put a pump on the delivery pipe for input and out the blow down and ran the water in and out until cool this could be done in 2 hours for a big boy. it worked for them. regards bb


staybolt2@netscape.net

The UP method sounds about the same as the CN Canadian National. You basically introduce cool water into the boiler (slowly) and at the same time keep the blow-down open. The toughest part is to keep the water level in the glass at a constant level. The water should never fall below the crown during the event. This does provide an even cooling and does not hold you up when you are pressed for time to get the boiler wash done and the engine fired up for the weekend. Anyone else care to share what they do?

This is an intersting question. Now that the days that the boiler is above atmospheric pressure are considered a service day I can see where a shorter cool down period may be desirable. I also wonder if even leaving the boiler cool normally will anyone except UP ever reach the 1472 service days.

We, on the 3751, already use a circulating pump during steam ups. This is a pump attached to the blowdown and the feedwater line on the injector side. This provides very even heat during the up cycle. This method could also be used during cool down by employing a big radiator and fan in the system loop. Would this cool the boiler too fast though and cause fatigue from movement in the sheet intersections?

Santa Fe used to do a hot boiler wash. This is where the boiler was blown completely down into a holding tank. The boiler washed and then new hot water from a clean side holding tank pumped back in. This way the boiler was washed, refilled and the locomotive back on the road in 12 hours. I don't think that the boilers suffered from this procedure.

Also the water that was removed from the boiler was cleaned, treated and reused.

> This is an intersting question. Now that the
> days that the boiler is above atmospheric
> pressure are considered a service day I can
> see where a shorter cool down period may be
> desirable. I also wonder if even leaving the
> boiler cool normally will anyone except UP
> ever reach the 1472 service days.

For a service day to be used up, it requires boiler pressure above atmospheric AND a fire in the firebox. If the fire is killed and the boiler is allowed to cool on it's own, the pressure may take a couple of days to fall to zero, but those days after the day the fire is killed are NOT service days.

There was much discussion and controvery over methods of cooling down and boiler washing back in steam days. What it came down to was that railroads didn't have the luxury of allowing 2 or 3 days for a boiler to cool down to wash it. Especially when one considers (and this is far too often overlooked today) that many railroads had to wash boilers weekly or even more often, due to lousy water conditions that defied complete treatment. Allowing several days to cool down and fire up would have kept a locomotive out of service longer than it was in service. That would have been unacceptable, and even more so during wartime or other power-short times.

UP's and many other road's method was to blow the hot boiler out and replace it with very hot water until the pressure went to zero, then the washout was done with hot water, and the boiler refilled with a mix of steam and hot water, then fired up. The wash itself took only a couple of hours, which shows what can be done with a gang of experienced men equipped with the proper tools and equipment can do.

Some roads did a water change between full washes. Again, this was prevalent where water conditions were very bad. While this wasn't as effective as a full wash, it took less time and it did get rid of the concentrations of solids and salts and sludge and other junk that accumulates in the boiler.

I thought I would point out a few things about thermal stress in a boiler. First there will always be some stress due to the nature of the beast, we as boiler operators can minimize this stress but the only way to avoid it is to not heat the boiler up. The boiler is made of many parts that are all different shapes, thickness, and even materials. They will never all act the same due to these differences. Also the heat is not evenly distributed as the firebox end is hottest and the smokebox end is coolest. The circulating water in the boiler is the only thing that prevents damage from the intense heat produced by combustion

An important thing to remember is that a boiler feels the heat stress more from the fireside than the waterside. Preventing large quantities of cold air from entering the firebox in the period of time once the fire is out is probably the best way to prevent too much thermal stress.

There are many schools of thought on how draining a boiler should be done. A current theory for boilers is to drain the boiler hot. If the boiler is drained while the water temperature is well above 212 degrees all remaining water will flash to steam and the remaining heat will make the boiler dry bone dry. This is done now in industry to prevent damage to the waterside such as corrosion and pitting.

The important thing is to train your people, have a procedure that is based on research, and follow it consistently.

Forgotten Delaware
tom@forgottendelaware.com