Abstract
Ship diesel engine disassembly and assembly (SDEDA) is essential for ship inspection and maintenance and navigation safety. The SDEDA consists of various machinery parts and operations. It is crucial to develop a system of SDEDA operations to improve the efficiency of disassembly and assembly (D&A). Considering the “AND” and “OR” relations (modeled as links) among the D&A operations (modeled as nodes), an “AND/OR” network is developed to extend a specialized graph model for the D&A sequencing problem in the context of education and training. Then, we devised a mixed-integer linear program (MILP) to optimize the SDEDA sequence based on the AND/OR network. Considering the flow balance in the AND/OR network, we developed exact algorithms and random search algorithms using breadth-first, branch cut and depth-first strategies to minimize the cost of the shortest path that represents an optimal sequence of D&A operations. To the best of our knowledge, it is the first try to formulate the D&A operations by an extended network model. Numerical experiments show that the proposed algorithms are practical for solving large-scale instances with more than 2000 D&A operations. The breadth-first shortest-path algorithm outperforms the MILP solver from the perspective of solution quality and computing time, and all developed algorithms are competitive in terms of computing time.
Highlights
A diesel engine is ship equipment that is essential for navigation and various shipping operations [1]
Different from general disassembly and assembly (D&A) operations that are conducted at specialized workshops or even factories, the Ship diesel engine disassembly and assembly (SDEDA) is generally handled on ships in ocean shipping. e skills of the seafarer operators are so crucial at such occasions that the D&A operations must be optimized, and we try to standardize the optimal SDEDA processes for education purposes
G (V, A) defines a directed graph, where V is a set of nodes representing D&A operations, consisting of “AND,” “OR,” and common nodes; A is a set of directed arcs indicating the process, linking operation and one of its subsequent operations
Summary
A diesel engine is ship equipment that is essential for navigation and various shipping operations [1]. Due to the complexity of the equipment structure, the disassembly process needs to strictly follow the procedural principles: “from top to bottom,” “from the outside to the inside,” and “first removing, last installing.” We conclude these principles according to the positions and the sequences of operating the parts. E current procedures are still facing the problems of time-consuming and requiring additional studies Because of these issues, this paper establishes the AND/OR network optimization procedures to investigate them. E shortest path is significant for the D&A operations because it represents a sequence of assembling or disassembling parts of the engine with the minimum time cost and operational cost. We established an MILP ((1)–(12)) to minimize the arc costs of the shortest path according to the balance of inflow and outflow in the path as well as AND/OR logic relationship between the nodes by using the notations as follows. S is a virtual origin when we try to sequence the parts for removing d gradually; d is a virtual origin when we try to sequence the parts for assembling them into a whole from s
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