Firing up steam locomotives/rapid startup

I've never heard such a thing, other than hooking up a locomotive to house steam.

We would pre-heat our steam locomotive before an operating day in cold weather, but that's about it. Getting pressure on the gauge was not something we wanted to do--just preheat the water a bit.

You definitely don't want to stress the boiler by heating too fast.

One of the worst things you can do to a steam locomotive boiler is to fire it up too fast. A too-fast fire up sets up tremendous mechanical stresses in the boiler that can break staybolts.

I once witnessed a fast fire up on a steam locomotive where the firebox was hot and steam pressure was showing on the gauge, but the front of the boiler just behind the smoke box was still cool to the touch, at ambient temperature! The boiler was creaking and banging loudly as it tried to deal with the huge mechanical stresses within it, caused by the temperature difference between the front and back end of the boiler. The result was a locomotive that was ready for service just a couple of hours after the fire was lit...with six broken staybolts!

A locomotive boiler is a huge chunk of steel. All that steel has to be bought up to temperature slowly, so that the boiler becomes "heat soaked" evenly. When firing up the 765, we take at least eight hours to get steam up, and more often closer to twelve hours. Taking our time allows all that steel to heat evenly, minimizing the thermal and mechanical stresses put on the boiler.

@bigkid posted:

One of the drawbacks was waiting for the car to build up a head of steam, compared to the rapidly improving gasoline engine cars or the early electric cars that were quite popular. They developed something called a 'flash boiler' (or something like it) , that could bring it up to full steam quickly.

Of course, the big difference here is size. A Stanley Steamer is nearly microscopic in size compared to a full-size steam locomotive. Even compared to our tiny 0-4-0T, which itself takes six hours to heat.

I appreciate the responses, including Rich. The thermal load to get something the size of a steam engine boiler to full temp/pressure is huge, and thinking about Rich's response it would be staggering forces on the boiler due to uneven heating. I wondered if some bright person figured out a way around that, but other than maybe keeping the boiler fired to some degree, which obviously would be costly fuel wise and other wise, it sounds like that never changed. It is another reason of course why steam was replaced by diesels, cold starting diesel engines can be interesting, but it doesn't take much before they are ready to go.

This past June my family and I visited the Great Smokey Mountains Railroad. While I was talking to one of the employees he stated that they could take the 1702 from “stone cold” to ready to go in 6 hours. I didn’t think that sounded right, but I’m not an expert so I didn’t call him out on it.

Old heads told me that Santa Fe used natural gas, available in the roundhouse, to slowly heat up water in the boiler from a burner in the firebox, before beginning the oil firing (which was used to make steam).  The oil was pre-heated in the tender using steam from the roundhouse stationary boiler, so that it could flow and be atomized in the firebox.  The process took hours, usually at least one 8-hour shift.

As to flash boilers, steam generators aboard Diesel and electric locomotives were flash boilers, capable of quickly producing lower pressure steam in a volume useful for train line steam, but not even close to enough to run a steam locomotive.

They were cylindrical in design, with water tubes coiled helically around the inside.  The tubes were filled with water, and then diesel fuel was atomized downward from the top.  Also at the top was a spark plug which ignited the fuel.  Steam buildup was achieved in just minutes.  The fire cycled on and off as needed to maintain the desired steam pressure for passenger car heat, hot water, and steam ejector air conditioning (on cars so equipped).  

They could build up soot if not properly adjusted, and then would become difficult, failing to re-ignite when required.  If that occurred, the Diesel Fireman* was usually sent to open the peep hole glass door, light a fusee and put it into the boiler through the hole and then quickly close and secure the door.  A somewhat explosive ignition would then occur from the atomized fuel and the collected fuel from failed attempts at re-igniting.  Normally, the concussion removed enough of the accumulated soot to enable automatic re-ignition to resume, although adjustment of the fuel/air mixture by shop forces would be required to fix the problem.  In general, railroad steam generators operated as intended, but could not be relied upon to be trouble-free.

*  The second engine service employee in the cab of passenger trains, whether officially referred to as Fireman or Assistant Engineer, depending on the union agreement in effect on a particular carrier.