Yang-Suk Kim’s research while affiliated with Kepco and other places

This study analyzed the rate of loading (ROL) phenomenon, which is generated during the operation of a motor operated valve (MOV) under fluid pressure conditions. ROL is one of the most important parameters for an MOV performance evaluation. This paper includes the analysis results for the characteristics of ROL and the effect of fluid pressure on the ROL. Dynamic and static test were performed to analyze the ROL effect for flexible wedge gate valve. The result of this analysis confirmed that the ROL is generated under fluid pressure condition and that the ROL value under high differential pressure condition appeared to be higher than under low differential pressure condition. According to the test results of multiple valves, the ROL appeared to become higher, as the differential pressure increased, and under the high differential pressure condition, it accounted for approximately 17.6% of the thrust loss. In addition, the ROL effect was negligible in valves with a low differential pressure (below 1100kPa).

The valve performance has been evaluated from the theoretical equation based on design information such as packing thrust, spring preload and friction coefficient(). The accuracy of those data can be lower than that of vendor's initial design data. Especially, the friction coefficient can be degraded with time than the original condition and the valve performance calculated using the previous friction coefficient can not be available. Accordingly, this paper is describing a new performance evaluation method of valve based on diagnostic test data which are acquired from a site valve tested in static and dynamic conditions. Especially, this paper provides a new method using friction coefficient() which is derived from the diagnostic test data acquired in the valve's design basis condition.