|dc.description.abstract||Research has shown that unmanned merchant vessels are possible, and researchers have claimed that larger autonomous vessels can be seen within 10 years. For oceangoing vessels, one of the biggest challenges is to get systems and machinery to work reliably for up to 4 weeks without maintenance. Therefore, a need to identify the systems that can be solely maintained in port, and those systems that will require redesign is present.
Reliability-Centered Maintenance (RCM) is a procedure that determines what must be done to ensure that any physical asset continuous to do whatever its users wants it to do in its present operating context. The procedure is a thorough process that identifies critical failures for an asset in its operating context, and determines whether maintenance tasks can reduce the risk to an acceptable level. If no maintenance tasks are found to be applicable and effective in the operating context, the process requires one-time changes, such as redesign, modification or change of the item s operating context. For an oceangoing merchant vessel that is to be used in a new operating context, where no maintenance will be possible for up to four weeks, the procedure can be used to identify the critical failures and whether the risk can be reduced by means of maintenance, or if one-time changes are necessary. In this thesis, those critical failures that cannot be managed effectively by maintenance has been defined as barriers.
This thesis establishes a step-by-step procedure for how to use RCM principles for identification of barriers. The procedure is considered to be a very useful tool for identifying and breaking barriers in design of unmanned engine rooms for merchant vessels. However, to effectively and successfully perform the procedure, a group consisting of an RCM facilitator well versed in RCM principles and experts with in-depth knowledge about the systems is strongly recommended.
The procedure is used in a case study to identify barriers in a fuel oil system that uses HFO, as this is the most common fuel used today on oceangoing merchant vessels. The analysis has been performed on the fuel system under normal seagoing conditions, and the functional failure analysed is Supplies no fuel to the engine . As the RCM process only focuses on the maintenance, other procedures the crew may have such as opening and closing of hand-operated valves falls outside of the scope.
Four barriers were identified in the analysis: plugging of the by-pass filter, plugging of the ME automatic backflush filter, plugging of the transfer pump filter and plugging of the flowmeter filter. These failure modes are identified as barriers because cleaning of the filters too often are required less than 4 weeks after the last cleaning. As the operating context states that maintenance cannot be performed at intervals less than 4 weeks, and the risk is considered to be unacceptable, the failures are considered to be barriers. The conclusion is therefore that one-time changes such as redesign, modification or change of operating context for the fuel system is necessary in order for an oceangoing merchant vessel to be able to sail without maintenance personnel with an acceptable risk. As the frequency of cleaning tasks are a direct function of the condition of the fuel, a one-time change that can be effective on all identified barriers is change of fuel. A comparison made with an FMECA analysis from a vessel running on diesel fuel indicate that this will have a significant effect.||