The Mutual Improvement Classes of the old steam railways still continue for today's preservation volunteers. This is one of a series of posts from notes of talks given by Jan. To find them all, select label 'MIC'.
1. Introduction
When steam locomotives come out of traffic, a number of activities are carried out as part of Disposal. If the loco is not required the next day, the fire will often be withdrawn, leaving a clear firebox and ashpan ready for the next turn of duty, although many railways prefer to leave some clean fire in the firebox to allow it to cool more slowly. If a large locomotive is to be steamed the next day, the fire will be cleaned and a maintaining fire built up to last overnight. When small locomotives are required next day, the fire may be withdrawn or a small warming fire may be left in the firebox. The smokebox char should be removed and, if possible, the locomotive coaled and watered before stabling.
2. Safety
Disposal can be a heavy and dirty process and it is usually carried out by staff who have been on duty for a number of hours and may be suffering from fatigue. Cumbersome and hot fire-irons have to be dragged around and hot clinker may need to be thrown off the footplate in areas where there may be other people. It is also often carried out at dusk or in darkness, increasing the hazards. For these reasons, incidents are most likely during disposal and you must thus redouble your efforts not to put yourself or others at risk. Failure to maintain adequate boiler pressure during disposal may result in shunting movements being carried out with only partially effective brakes.
3. Coming 'On shed'
The fireman will normally be able to reduce his firing rate prior to coming 'on shed', so as to minimise the amount of fire to be disposed and avoid disposing unburnt coal. However, nice judgement is called for so as to preserve adequate boiler pressure for any shunting which is required and to allow the boiler to be filled before leaving the engine. As the boiler pressure drops, not only will the tractive effort of the locomotive be reduced but it may be impossible to create the correct level of vacuum and the braking effort of the steam brake (if fitted) will be reduced.
4. Drawing the fire
If the fire has been well-managed and correctly 'run-down' this job is not too bad, even on a large engine. On a 'traditional' steam locomotive, an assortment of fire-irons is used to push the remaining fire and ash through the firebars into the ashpan, leaving the whole of the grate clear. The aim is to slide the fire-iron up and down the firebars, dislodging any matter adhering and helping the ash to drop through the air spaces. Avoid digging the end of the firebar into the air spaces as it is all too easy to unintentionally dislodge firebars and drop them into the ashpan. A Pricker (with an L-shaped end) is best used on its side. A fire-iron with an intentional kink (the Bent Dart) is good for reaching the back corners of the firebox. Particularly on a long firebox, a Rake is useful to move the used fire forward and backwards until it drops through the firebars. Small amounts of soft clinker may be broken up and pushed through the air spaces: anything substantial needs to be shovelled out ('paddled out') through the firehole door with the Clinker Shovel and dropped over the side of the footplate. Clinker shovels invariably get badly distorted with the heat, making the clinker removal operation difficult and time-consuming - one of the best incentives for careful firing which will largely avoid creation of clinker and ease disposal. If necessary, the firebox Deflector Plate (also called the Smokeplate or Baffleplate) may be removed to give more space for operating the fireirons. The Deflector Plate can be lifted out carefully on the back of the firing shovel, but remember that it will remain hot for some time and certainly shouldn't be placed on a wooden cab floor!
Locomotives with a Drop Grate (like 'Flying Scotsman') provide a means of dumping clinker into the ashpan without resorting to a Clinker Shovel, but care is necessary to avoid blocking the hinge with ash, preventing the drop section from being raised again.
Modern locomotives may be fitted with a Rocking Grate which allows clinker to be broken up 'on the road' by rocking the left side or right side of the grate. During disposal, operating the rocking action to its fullest extent will quickly discharge the whole fire into the ashpan. If a Hopper Ashpan is also fitted, ashpan doors can be opened to directly discharge the ash. Ensure that there is no build-up of ash to prevent the doors from properly reclosing, and, once closed, ensure that all catches are properly set to prevent the doors unexpectedly opening.
Although modern practice is to discharge ash into some form of wheeled skip which can be afterwards lifted out of the pit, traditional practice carried out at most preserved railways deposits ash directly into the pit. Where the luxury of a Hopper Ashpan is absent, the contents of the ashpan are scraped into the pit by opening all the Damper Doors and wielding an Ashpan Rake from the pit underneath the engine. This can be an unpleasant task and, where possible, a water hose should be used to cool the ash and minimise the dust. Ash will normally collect on the brake rigging and the various pipes running underneath the locomotive. Make sure that it is brushed off or sluiced off with water before finishing.
5. Filling the boiler
Once the fire is removed, all dampers and the firehole door should be shut to minimise the cold air entering the firebox, which can chill the firebox tubeplate and encourage leaks through too rapid cooling. For this reason, any subsequent movements of the locomotive under its own power should be confined to short, light engine movements.
As the boiler pressure starts to drop, the temperature of the steam will fall and the hot water will contract. One or both injectors should be put on to ensure that, even when cold, the water will be well up the gauge glass. As the pressure falls, injectors may need adjusting: the water flow will need to be reduced as the pressure drops, otherwise the injector may 'knock off'. Once the boiler is full, make sure that the injector steam and water cocks are fully closed.
Make sure the blower valve is off and shut any auxiliary valves applicable to the particular locomotive, for instance, the steam cock supplying the brake or atomiser. Where a main shut-off cock on a manifold is to be closed, do not over-tighten or it may be difficult to open again. Where backhead injectors are provided with square-headed shut-off cocks, close these with a suitable spanner (if so instructed) but avoid overtightening.
Finally, the gauge glass (or gauge glasses) should be isolated and the pressure within relieved by opening and then closing the blow-down cock. Before the engine is left, the handbrake should be hard on, reverser placed in mid-gear, regulator closed and cylinder drain cocks opened.
