3.7 Fuel oil system
Fuel storage and distribution play a crucial role in the smooth and efficient operation of ships, which are essential for global trade, transportation, and naval activities. Ships rely on a variety of fuels to power their engines, such as diesel, heavy fuel oil and liquefied natural gas (LNG). Fuel storage systems in ships are designed to accommodate the considerable energy requirements during long voyages, ranging from short-haul trips to transoceanic journeys. The distribution of fuel on board ships involves a network of piping, valves, pumps, and other equipment necessary to transport fuel from storage tanks to the engines or other auxiliary machinery. The distribution system is designed to ensure a reliable supply of fuel to the engines while maintaining the safety of the crew and the vessel.
Various piping systems, provided for bunkering, storage, transfer, offloading and treatment of fuel oils. The following systems are provided for diesel engines that operate on heavy fuel oils: fuel oil transfer system, fuel oil treatment system and fuel oil supply system.
1. Fuel oil transfer system: this system receives and stores fuel and delivers it to settling tanks. Fuel oils are loaded through deck fill connections that have sample connections provided to permit the fuel to be sampled as it is taken aboard. HFO is loaded in storage tanks fitted with heating coils. In preparation for use, HFO is transferred to the fuel oil settling tanks via FO transfer pumps which are equipped with a suction strainer. Piping is so arranged that the pumps can transfer fuel between storage tanks and then to the deck connections for offloading. Settling tanks are used to permit gross water and solids to settle on the bottom.
2. Fuel oil treatment system: from the settling tanks fuel oil is transferred to the service tanks via FO treatment system. For cleaning of heavy fuel oils (HFO) the two stage process is commonly used. The fuel is heated in a settling tank to about 50-60°C and then is drawn out by the purifier inlet pump. The inlet pump delivers the fuel to a thermostatically-controlled heater which raises the fuel temperature to about 80°C, and hence to the centrifugal purifier. The dry purified fuel is then transferred to a centrifugal clarifier by the purifier discharge pump. After clarification, the clarifier discharge pump delivers the fuel to the service tank for the engine use.
3. Fuel oil supply system: this system supplies the fuel from the service tank to the diesel engine. The system consists of: a supply flow meter, supply pumps, circulating pumps, preheaters, the final filter, a viscosity controller, a FO venting box.
The pressurised system is preferable while operating the diesel engine on high viscosity fuels. It can be delivered as a modular unit (fuel oil supply module), tested and ready for service supply connections.