(155a) Control Valve Performance – Troubleshooting and Understanding Dynamic Performance Metrics

Poor control valve performance continues to be a widespread source of poor control loop performance. In the 1990’s, a study of over 5000 control loops revealed that 30% of the loops were INCREASING process variability due to poor valve performance. Decades later, on a recent control foundation improvement project, over 50% of the loops had poor performance due to significant control valve performance issues. This presentation explores the process-related symptoms of poorly performing control valves, the source of these issues and insights on how to fix or avoid these problems. ANSI/ISA-75.25.01 test procedures and valve response metrics will be explained. These metrics include dead band, resolution, lost motion, process gain and step response time. A simulation of these valve response metrics will be presented. Valve performance troubleshooting techniques will be discussed, including the use of the position “readback” signal available from “smart” valve positioners.