Abstract: In the offshore engineering construction， the cleanliness of equipment and instrumentation pipelines plays a vital role in the safe and long-lasting operation of production platforms. Oil flushing as an efficient pipeline cleaning method， the existing studies have focused on analyzing the oil-flushing process itself， while paying little attention to improving flushing efficiency or optimizing the methodology. In this manuscript， the oil flushing equipment， construction process， factors affecting oil flushing efficiency are studied. Then the characteristics of series and parallel flushing methods are compared. Finally， an oil flushing device that can be used in multiple parallel flushing is proposed， and numerical simulation of the oil flow characteristics in the device is carried out based on ANSYS Fluent. According to the results of the simulation， three optimized forms of single column structure， symmetric structure and staggered structure are proposed， and the flow distribution characteristics of the three optimized structures are compared with those of the original structure. The research results show that the flow distribution consistency of the oil in the form of symmetric structure is the highest， and its four branch flow basically meets the flow requirement of 43.73L/min， which can realize multiple parallel flushing.

Key words: offshore engineering, oil flushing, numerical simulation, method optimization