A day in steam may call for a cup of tea, a chat, or just a brief pause.
However, with the standard-fitted SRS marine-type boiler, taking a break can be tricky – often ending either in a stone-cold fire or prematurely with the safety valves lifting. The challenge stems from the shallow firebed and the high burning temperature of coal (e.g., anthracite burns at roughly 900 - 1200 °C), which, under these conditions, requires a steady oxygen supply (via exhaust draught or blower) to stay alight.
There is, however, a very practical workaround that lets you step away for a break without needing to constantly adjust the fire or water level, making it easier to keep the boiler stable while you’re off the controls.
Stepping Away Without Surprises
Preparation for a break starts, like any other operational state with a steam boiler, a little beforehand. Aim to arrive at the station with a boiler pressure of around 100 PSI, ensuring a steady but not overly intense fire – hot enough to sustain itself for a few minutes, but not roaring. Fill the boiler nearly to the top, with the water level just shy of the upper part of the sight glass. This will drop the pressure to about 80 PSI, setting a stable base for the break – water level and pressure checked.
Next, the fire: stuff the firebox to the brim with charcoal. (Yes, I know there are tubes at the back of the firebox, but any stray charcoal will be sorted by the heat and draught later.) The big advantage of charcoal in this setup, compared to coal, is that it burns with minimal oxygen and can quickly ignite regular coal when oxygen is supplied.
Turn on the blower to make sure the layer touching the firebed ignites firmly, then reduce it so the charcoal is just barely smouldering. If you look into the firebox, the glowing areas should waft slightly, not burn hot – the blower just barely noticeable (ideally, in total silence). I usually double-check this by ear as well, right at the top of the smoke stack.
This setup prepares the boiler for at least half an hour of rest and will typically increase the pressure by around 5 PSI every 15 to 30 minutes during the break. If time allows, top up with more charcoal as needed if some has burnt away, or feed water to maintain proper levels depending on the length of your pause. When feeding water, you may need to build up a bit more pressure just beforehand – overall, during the break, aim to keep the pressure from falling below 80 PSI.
Back to Service
Once your tea or break comes to an end, gradually increase the fire’s temperature using the blower. This process should take about 10 minutes to clear space for coal and restore pressure, allowing you to feed water if needed and resume firing with regular coal.
If possible, I prefer a solo round or running with empty carts after a break to fully burn out the charcoal, establish a steady fire using coal alone, and bring the system back to an operational, balanced state – ready for the next, possibly heavy, passenger train.