Jamie, there are guys far better qualified to discuss this than I am, but the biggest factor is the faster warm up/ cool down cycle- while a coal fire grows gradually, and can be banked between runs or allowed to die off a bit before dumping the fire, an oil burner is essentially "on" or "off", with varying degrees of "on". Even the lowest heat level is very intense.

Heating/ cooling cycles are very hard on a firebox, causing cracking, over-stressing staybolts and firebox sheets, etc. Depending on the firebox design, considerable firebrick can be required which may not be required in a coal fired engine.

Sanding the flues to remove oily sludge can erode various surfaces such as tube and flue beads, superheater returns (ends), staybolt and rivet heads. This may or may not be worse than "cinder cutting" on a coal burner- that can be a function of the coal quality and type of service the engine is in.

We discussed "lighting off the bricks" here in a previous thread- a practice which, if properly done, saves much time and effort, but if badly done can cause a fair bit of grief. I once watched an experienced fireman light CP 1201 off the bricks when the engine was too cold, causing an impressive firebox explosion. The engine lost a lot of firebrick but was still serviceable althugh her draft characteristics were drastically changed: I fired her three days later and she was a bear to handle, with a very rough fire that was hard to fine tune to produce 1201's characteristic nearly clear stack. Replacement of the firebrick, I'm sure, was a fairly expensive job.

The type of oil being burned will affect maintenance and operation as well- biofuel, recycled veggie or lube oil, clean diesel, or Bunker C (which is apparently a very nasty fuel, producing a lot of minor explosions or fire outages as it burns).

Design and placement of the oil burner is critical, to avoid focusing too much heat on one spot and ruining the metal.

Hopefully this helps, and I'm sure your question will bring out a wealth of detail from the many fellows on the list who spend a big part of their lives rebuilding boilers and fireboxes.

Steve

When I was in the Navy I operated high pressure boilers that ran at 1275 PSI at 1000*F superheat. We usually took 24 hours to go from cold iron to operating pressure. shutting down consisted of just shutting down & maintaing water level.
Now if we pushed it we could be up on line in two hours but that was just too hard on the boilers & piping. In the Navy emergency's do happen & I think the shortest warm up time I remeber was around 5 hours. Huricane on it's way & we had to get out to sea.
When we fire up #401 we do it slowly & give everything a chance to expand. When shutting down we let the boiler cool down on low fire for a while & then shut off the fuel. The boiler metal & the water in the boiler help cool the boiler down slowly. If done properly there is no more damage to the boiler than having a coal fire. Just use common sense.

Dave Huffman

Steam power plants pulverise coal into dust then blow it into the boiler fire as almost a gas form, to bad steam engineering in loco's never got to that point .I'm sure they would use less coal an produce less smoke.

But they did! Somewhere I have information I was sent from a friend in Australia about a coal dust firing system experimented with, sort of an atomizing injector like a large and less dense oil burner that blew a column of pulverized coal dust into the firebox in a stream of air. Probably Hugh knows where you can link to that information. My copy is lost in the stacks around here somewhere.......

dave

I have the same problem with info filed in stacks!

IIRC, the Aussies used pulverized firing for burning "brown" coal (some sort of low grade stuff like lignite) and it worked pretty well. There were some earlier experiments in the U.S. with pulverized coal firing (1930's?) which weren't too successful, but the Australian project was in the 1950's and seemed to work pretty well. David Wardale looked into it in South Africa in the 1980's. He discussed it at length with a sales engineer for a company that made the equipment (even gave the guy an extended cab ride in a 25NC to show him what the conditions were) and the supplier was confident that their equipment would work in a steam locomotive.

Pulverized (or micronized as he called it) coal firing would kind of be the best of both worlds: instant response to steam demands like oil firing, no ashpan to deal with, no problems with clinkering or cleaning fires, but use of cheap coal rather than expensive oil.

Didn't the N&W's steam turbine Loco use pulverised coal in it's water tube boiler??

Dave H.

Firing a boiler with oil done properly has no danger to the boiler. And in my experience the ability to simply turn on the fire everyday far outweighed the storage and manpower problems associated with coal. Some may claim it "Doesn't smell right" but they are rarely operators who say that. Go figure.

I hear you Jim. Here in Illinois it is hard to get proper sized & good quality coal for a hand fired engine.
With oil, when you shut the fire down flue time stops. If you bank a coal fire over night, that flue time just ticks away.

DBH

No, it used a conventional stoker and burned normal lump coal, but it did have a "traveling chain" grate which apparently worked pretty well. These are common in stationary boilers but AFAIK this was the only locomotive application.

And as far as sanding, I'm told you don't need to on a coal fired engine because the coal dust scours the tubes. So either way you're getting abrasives in your tubes. I would like to know if there is documented damage in the modern day through sanding tubes.

I think coal fly ash is more abrasive than most sand. I guess it would make a difference of which coal you are using. Good question really,

Dave H.