Fire room

On a ship, the fire room, or FR or boiler room or stokehold, referred to the space, or spaces, of a vessel where water was brought to a boil. The steam was then transmitted to a separate engine room, often (but not always) located immediately aft, where it was utilized to power the vessel. To increase the safety and damage survivability of a vessel, the machinery necessary for operations may be segregated into various spaces, the fire room was one of these spaces, and was among the largest physical compartment of the machinery space. On some ships, the space comprised more than one fire room, such as forward and aft, or port or starboard fire rooms, or may be simply numbered. Each room was connected to a flue, exhausting into a stack ventilating smoke.

By their nature, fire rooms were less complex than their allied engine room and were normally supervised by less senior personnel.

On a large percentage of vessels, ships and boats, the fire room was located near the bottom, and at the rear, or aft, end of the vessel, and usually comprised few compartments. This design maximized the cargo carrying capacity of the vessel. The fire room on some ships was situated amid-ships, especially on vessels built from the 1880s to the 1990s.

Vessels typically contained several engines for different purposes. Main, or propulsion engines are used to turn the ship's propeller and move the ship through the water. The fire room got its name from the days when ships burned coal to heat steam to drive the steam engines or turbines; the room was where the stokers spent their days shoveling coal continuously onto the grates under the boiler; poor men could sometimes pay for a trip across the Atlantic by signing on to work as a stoker for a one way trip, laboring in exchange for a temporary place on the crew. Later heavy fuel oil came into use, first combined with coal, then alone, as the petroleum industry developed, and the cleaner, easier to transport, load and burn liquid was found to be far superior once the appropriate logistical network was set up. With coal power, there was a mechanism for removing ash from the grates, as they would build up rapidly over time (the lighter fly ash would be drawn up the stack with the smoke).

On a steamship, power for both electricity and propulsion is provided by one or more large boilers giving rise to the alternate name boiler room. The latter name was preferred in the British Navy, among others. High pressure steam from the boiler is piped to the engine room to drive reciprocating engines or turbines for propulsion, and turbo generators for electricity. When cruising, it was normal for a naval vessel to damp the fires on up to 2/3'rd of their boilers, and use the steam from only a few boilers in one or two fire rooms to power the engines at low power. When higher speeds were required, more boilers would be brought on line (they were rarely extinguished entirely, as re-lighting a boiler was time consuming). In rare occasions, when flank speed was called for, all boilers would be burning at once, generating a great deal of steam for high speed operation, but at a very inefficient rate of coal consumption. Merchant vessels had much less need for high speed, so they'd generally be satisfied with far fewer boilers, and much lower maximum speeds (and even then they would often save on fuel by not using all of the boilers, and traveling at a sedate 4-5 knots)

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Wikipedia