Flow Control - Jan 2012
by Sandro Esposito rather than smoothly touching it because the excessive friction caused the plug to stick and then release suddenly The valve cage plug and seat were repaired and the valve was put back together The plant was able to restart and the control valve controlled the flow of steam to the turbine as expected Offline diagnostic tools provided a valve signature that helped plant personnel make important maintenance decisions and Figure 4 A cutaway of a valve similar to the one described in Case Study 1 Metal debris had become stuck in the Lo dB Cage then allowed the team to document the control valves performance after it had been returned to service Case Study 2 Online Diagnostics Provides Advance Notice of Pending Problems By outward appearances all seemed well with a process at a chemical plant producing PTA for the plastics industry Operations personnel reported no problems with the process or the six inch control valve controlling it Online valve diagnostics OVD however told a different story the valve was showing signs of fatigue The control valve was adequately controlling the process but the actuator required more thrust than typical to move the valve back and forth The OVD technology detected that hysteresis had quadrupled in one month and found that positioning accuracy was poor Figure 5 It was only a matter of time before process integrity and the quality of the product being produced would be impacted The valve was flagged to be repaired during an upcoming minor outage At that time the actuator was taken apart and technicians found that a degraded o ring on the piston had created residue that prevented the piston from sliding smoothly within the piston chamber The o ring was replaced and the valve returned to service Operators immediately reported having more robust control not Our Valves Communicate Our complete selection of manual and automated valves can communicate in any method you prefer including basic mechanical switches proximity switches ASi and Devicenet Our Configurators Save You Time Use our online valve configurators to do your estimates online You can configure all the configurations shown and thousands of others Our People Want to Help Too If you have any questions at all call us we like to help Compact High Performance Automated Manual Valves Toll Free 1 800 899 0553 assuredautomation com 19 Walnut Avenue Clark NJ 07066 Tel 732 381 2255 Fax 732 381 2328 Email info@ assuredautomation com Circle 15 or Request Info Instantly at www FlowControlNetwork com CONFIGURATOR tomation assuredau com at THE him Meet www FlowControlNetwork com January 2012 23
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