Identifying and eliminating weak points in ship’s machinery plants

Abstract

Autonomous sailing is considered by many to be the next big thing in the shipping sector. Many companies, including Rolls Royce and DNV are investing heavily in research that helps in the development of autonomous shipping. Most research is currently being done regarding autonomous navigation, communication and cyber security. What is often neglected in these studies is the need for maintenance within the engine room. With all ships having multiple crew members solely dedicated to keep the engine room going, their absence will have a big impact on the design of engine rooms.
This paper aims to find what equipment will become a weak point in engine rooms once these are no longer occupied and maintained by crew members, and how these weak points can be eliminated. With the absence of reliability data that corrects for maintenance and crew interference, this paper tries to find these weak points by analysing crew member behaviour. It is assumed that if a crew members spends more time on equipment, or deals with it more frequently, then that piece of equipment is less reliable.
In order to find what equipment can be seen as a weak point, a redundancy reduced risk index was created. This index is a combination of the frequency index, which states how often engineers spend time on equipment, the severity index, which lists the consequences of failure for equipment, and the redundancy index, which is dependent on the level of redundancy of components. The redundancy reduced risk index is split into three levels: low, medium, and high risk. Medium and high-risk components were considered weak points, while low risk components were not.
For all high risk and for most medium risk components, solutions were generated which will reduce the risk index of the components or system overall. For some components, the risk was deemed acceptable, as any solutions would be too costly to justify the risk reduction. Solutions were split into two categories: specific solutions, which were all catered to specific components, and a bulk solution, which was the installation of a second drive train. A second drive train would include a second main engine, gearbox, propeller and rudder.
With the solutions found, the two categories were subjected to a financial analysis to see if they are commercially viable. The solutions were applied to ships of four different sizes, ranging from a 6,000 GT feeder to an 85,000 GT capesize bulk carrier. For these ships, the OPEX were calculated and divided into four categories: Operational costs, fuel costs, capital costs and crew costs. The initial investment for the machinery plant was also calculated. This was the basis to finding the increased cost for solutions found in this paper.
Using these specific solutions, the machinery plants will become roughly 50% more expensive, while adding a second drive train will increase the machinery cost by 110%. It is assumed that these solutions will eliminate the need for a crew and therefore eliminate all crew costs. Using these figures, it was found that the specific solutions will lead to a potential yearly savings of $600,000.– for all ship sizes, and adding a second drive train will lead to a potential yearly savings of $500,000 – for the small ship and $163,000.– for the larger ships.
With both the specific solutions and the second drive train, the machinery plant is deemed reliable enough for continuously unmanned operation, which proves the technical feasibility of continuously unmanned engine rooms.