Fire door
A fire door is part of the boiler equipment on a steam locomotive .
That used to fire the firebox serving fire hole in the firebox back wall is closed by a fire door. While in the early days of steam locomotive construction sliding, double-sliding or simple revolving doors were predominantly used, from the development of German standard locomotives mainly the inward-opening tilting door of the Marcotty design was used. The main advantage of the tilting door is that it slams shut in the event of sudden overpressure in the fire box, which can occur when heating or superheater pipes burst, protecting staff from scalds or burns. To protect against strong burns, the Marcotty fire door has an easy-to-change protective sheet on the inside. The tilting door is operated by insulated handles on the counterweights by the locomotive driver or stoker and engages in the closed, open and half-open position (for working on the fire). On the side of the door in the door frame (door cupboard) there are air ducts with non-return flaps, through which air can flow into the fire box behind the closed door (upper air). This avoids a lack of air in the case of slagged fire and at the same time cools the fire hole ring. Two sizes of Marcotty fire door are known in German locomotives. While the small fire door is mainly installed on narrow-gauge and regional railway locomotives, the larger design is only found on regular-gauge steam locomotives.
Locomotives with mechanical grate loading ( stoker ), coal dust or oil firing also have fire doors of the simplest design, which are necessary to control the fire, to clean the grate or the fire box. These fire doors are often designed as revolving doors and locked with sash bolts . In the case of oil firing, noise insulation is usually installed.
Older steam locomotives or narrow-gauge locomotives are equipped with revolving or sliding doors (top picture). In the standard locomotives of the Deutsche Bundesbahn from 1950 , a simplified tilting door was often used, in which the side air ducts have been omitted. There is a small hatch above the door through which the fire can be observed when the fire door is closed.
Tilting door of the PM 36-2 of the PKP
Marcotty fire door, partially dismantled, during the refurbishment
