Even in an automated engine room, there is still a place for the Fireman/Watertender. Steam vessels, and motor vessels with auxiliary boilers, use vertical water tube type boilers to provide a heat source for various shipboard purposes, including cargo management, a low-speed power source supplanting the ship's main engines--usually diesel engines--for ship movement in operations like in-port maneuvering and docking, and crew or passenger comfort.
Keep your boiler operating, even if it is not your primary power source. If you are aboard a steam-powered ship, your ship's boiler runs on Bunker C fuel, also known as Number 6 Fuel Oil. Bunker C is very thick, it requires heating—to 120 to 140 degrees Ft-- before it will flow from the ship's saddle and deep tanks to the preheated service tanks, where it is heated to 230 to 240 F so that can be introduced into the boiler's burners to provide motive power for the ship.
If you are aboard a motor ship powered by diesel or diesel-electric motors your auxiliary boiler is fired by diesel fuel and produces steam that powers the ship's evaporators, providing hot and cold water for your vessel's crew and other people. The auxiliary boiler also provides a source of heat for compartment, offices, cabins and spaces.
Use your auxiliary boilers to provide a secondary power source, suitable for low-cost, low-speed main power for motor ships maneuvering in port. Your thrusters are diesel powered; final docking in some ports may depend on tugs, but power ahead and astern comes from by your auxiliary boiler system at bare steerage way.
At least one state has adopted regulations that provide severe limits on the amount of sulfur in marine fuels. This applies to diesel main propulsion, but exempts diesel-fired auxiliary boilers from the regulations, meaning that using the auxiliary boiler for port maneuvering will not flirt with a fine. The disadvantage in using your auxiliary boiler for maneuvering is the "lag" imposed by using a telegraph, rather than direct controls: your maneuvering orders must not only compensate for the mass of the ship, but for the lag time required for engine department personnel to manually adjust the boiler.
Keeping the auxiliary boiler fired in port also minimizes the costs that may be incurred as a result of using "required" electrical power from shore for on-board services, like heating, while the main engines and are shut down. The only electrical consumption aboard a vessel equipped with an auxiliary boiler should be for electrical services, water pumps and air circulation systems.
Tankers use auxiliary boilers in port to reduce the viscosity of crude oil. Its temperature must be 97 100 F or it will be too thick to flow through the cargo pumps. The tanker equipped with electric cargo tank heating can expect a hefty bill--paid in cash from the ship's safe--before departure. A ship equipped with an auxiliary boiler will escape that penalty. The same auxiliary boiler may power steam-driven crude oil pumps used for discharging the oil from the ship.
Auxiliary boilers also serve as an economizer at sea, allowing the diesel-fired mains to operate under a lighter load when assisted by the boilers. Called "co-generation," this power scheme represents a trade off in a competitive cargo environment. Those aboard might not notice trading a small loss of speed--2 to 3 knots--for fuel efficiency, but the savings in fuel used more than compensates for the 8 percent difference in speeds.
