Dynamic Analysis of Slurry Letdown Valves at H-Coal Pilot Plant

摘要

Mechanical Technology Incorporated (MTI) is under contract to provide technical services for the improvement of performance of critical equipment required in the coal conversion process plants. A key service required in these plants is the level control of the effluent separator of the reactor vessel where coal conversion process takes place. This function is usually served by discharge of the liquid phase slurry in the separator through valves commonly called letdown valves. A number of technical problems have been experienced with the slurry letdown valves in the pilot plant operations. These include: excessive wear rate of critical valve components as a result of erosion, corrosion, and flashing; breakage of valve trim as a result of excessive flow induced vibration (fatigue) and/or sudden high bending load; breakage of valve stem as a result of excessive structure vibration (fatigue) of valve body, actuator, and associated piping; and coking formation in the valve eventually causing plugging. An approach to providing engineering data necessary for the understanding and eventual reduction/elimination of these problems is vibration measurement and structural analysis, including design analysis of structural damping characteristics. MTI has performed the following analysis for the understanding of the basic vibration phenomenona of the slurry letdown valves and made actual vibration measurements of the letdown valves presently under operation at the H-Coal pilot plant: lateral natural frequency and mode shape calculations of the valve stems; axial natural frequency calculations of the stems including the actuators; and valve body natural frequency calculations, including calculations for nearby piping and supports. (ERA citation 08:019433)