Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

do steam locos spew sparks and fire most of time?

35 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    October, 2001
  • From: OH
  • 16,117 posts
Posted by BRAKIE on Friday, October 13, 2017 4:46 PM

Stix,I fully again it does look like it been touched up simply because of the fire coming from the stack-that would require a lot of hard firing just to keep steam up.




  • Member since
    September, 2013
  • 82 posts
Posted by shahomy on Friday, October 13, 2017 5:51 PM

thanks for those links, stix...i checked em could very well be right!

Am i ever gonna be able to lay any track???

  • Member since
    September, 2003
  • 5,306 posts
Posted by Overmod on Saturday, November 04, 2017 10:46 AM

Ye gods, so many posts, so much wack information... Smile

The short answer to the original question: most of the time, no.  In fact when firing to a ‘clear stack’ or even light haze there will probably be few fines carried over or pieces of glowing ash abruptly getting caught up and ejected.  If the engine slips, however, or something changes in the firing, that can change almost in an instant.  Here is some of what I have learned or seen about this:

First, there are several reasons why the ‘sparks’ are there; first related to a characteristic of ‘overfiring’  or excessive fines/trituration in fuel delivery which causes particles of unburned or ignited fuel to be lifted and carried in the draft, and second related to the amount and distribution of oxygen in the combustion plume (it’s intentionally close to a reducing atmosphere).  This is compounded by visible radiant combustion stopping within no more than a few inches of the rear tubeplate.

Now remember that the gas at admixture with steam in the front end is still at very elevated temperature, the steam does not for a variety of reasons quench it much before ejection, and turbulence due to good entrainment means good mixing with ambient air ... the dormant combustibles will happily wake to complete their combustion.

Sandaoling is an extreme case of the same phenomenon reported for many Big Boys, and for a similar reason: ‘subbituminous’ fuel that has to be fired so fast and in so friable a state that much of the combustion actually occurs without touching grates at all, a bit similar to proper practice in oil firing but with much less heat release per lb. or measure of volume.  Those  Chinese effects are very real when observed.

Oil firing has something of the opposite problem: unburnt fuel even at ‘soot’ size tends to be sticky even at fairly elevated temperature, and has to be ‘encouraged out’ by sanding the flues as described.  This is not a normal requirement on most coal-burning engines.  Note that it produces a RICH black plume that would be a dandy lambent flame if it were above ignition temperature or there were any kind of a flameholder after the front end (think the fire in the locomotive at Lac Megantic) — the fact that you never see this in actual service should, I hope, get you thinking.

Much of the performance if ‘modern’ big steam is made possible in part via the ‘self-cleaning front end’ which is really kind of a euphemism.  Prior to introduction of the arrangement, stuff carried forward through the Master Mechanic front end would be caught by internal screens (these replaced the external stuff in diamond or cabbage stacks) and would fall into a bottom-dump receptacle that had to be regularly checked.  The self-cleaning arrangement bangs and scrubs any cinders across the screen until they break up enough to pass through it, and at least in theory the screen can then serve as a flame barrier for anything ‘glowing’ as it goes through.  Plugging the relatively fine mesh needed to reduce cinders ‘effectively’ will of course progressively reduce draft on the fire until someone goes and bangs the screens open again.  Modelers who are interested in this stuff can find interesting illustrations in the Locomotive Cyclopedias of the era (the 1922 edition is now free online; the ‘41 and ‘47 are precious troves of detail; the ‘52 has some fascinating detail but already shows the great dying-off).

It is difficult to assure there will be no re-ignition if carried-over particles under some combinations of fuel, firing, and running unless some kind of external filter above the nozzle is fitted (one Canadian practice was wire ‘baskets’ over the stack top in fire season).  The effect both on performance of the front end and on required fuel and water consumption for a given amount of work required become increasingly prominent at either high speed or high steam mass flow.

  • Member since
    November, 2015
  • 1,011 posts
Posted by ATSFGuy on Thursday, November 16, 2017 10:37 AM

The wood burners with those unique ballon shaped smoke stacks did, so spark arresters were placed on top of the smoke stack to prevent forest fires.

  • Member since
    March, 2002
  • From: Milwaukee WI (Fox Point)
  • 9,303 posts
Posted by dknelson on Thursday, November 16, 2017 11:27 AM

Some years back I was railfanning a local railyard when a diesel switcher, probably an ex-Milwaukee Road MP15 which had been sitting idle for some time was coupled onto a VERY long cut of cars and worked like the devil to move them.  It was pitch black outside and yes I saw plenty of sparks shooting into the air.  Very impressive.

I have been trackside on a grade when a hard working coal fired steam locomotive went by, and yeah there was a shower of cinders that rained down afterwards.  Glad I wasn't wearing a white shirt, but they did get in my hair which I only realized during the next morning's shampooing - and then I checked the pillow!

Dave Nelson

  • Member since
    February, 2004
  • From: Central Ohio
  • 403 posts
Posted by basementdweller on Saturday, November 18, 2017 2:40 PM

In our fire station we have a log book from 1927, there were a lot of fires along the right of way and some roof fires that were logged as "spark from locomotive" as the cause. No wood burners around here. 

We are not talking one or two fires here and there,  these were a common occurrence. 

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Users Online

Search the Community

Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!