Load management for main engine
For the main engines in a direct-drive or gear-drive configurations, there is not much that can be done as far as load management is concerned as normally ships have one main engine and load management normally applies to cases with more than one engine. It should be noted that it is easy to show that the slow steaming leads to the main engine’s operation at low loads at a less efficient load factor. Overall, this low-efficiency operation of main engine has been accepted by industry since the impact of reductions in ship speed on a ship’s fuel consumption is much more effective than increases in the main engine’s SFC for slow steaming cases. Therefore, in main engines, non-optimal operation may be allowed due to slow steaming because of slow steaming greater benefits from much lower fuel consumption. However, in such conditions and if slow steaming is going to continue for long term, changes to engines performance characteristics are recommended via changes to turbochargers, injection system and other engine settings (engine adjustments for slow steaming optimized operation). No matter what load the main engine is operating under, it is mostly recommended that the main engine load should be kept at a reasonably steady level under normal operation. This is achieved by keeping the engine speed (RPM) constant. Frequent changes to the shaft rpm, thus engine load, are not efficient and must be avoided. When we need to reduce the output power of the main engine to reduce the consumption of the fuel and we apply the slow steaming, in this case the reduction of the output power is proportional to the consumption of fuel per hour, but at the same time, we are consumption more amount fuel per kW per hour output by the main engine. It is necessary to have in account the problems of damage and maintenance that the slow steaming cause in the engines.
Fuel Coefficient and Fuel Consumption in Relation to the Load Management
The fuel consumption of a ship depends upon the power developed. Indeed, the overall efficiency of power plant is often measured in terms of the Specific Fuel Consumption, which is the consumption per unit of power, expressed in kg/kWh. Efficient diesel engines may have a SFC of about 0.180 kg/kW h (MariEMS 2017).