METHOD FOR DETECTING BROKEN VALVE STEM

摘要

A method of providing an indication and alarm of a possible failure in a flu id control valve stem, plug or seat in a process control system having a microprocessor based valve positioner. The drive pressure, drive signal and valve position feedback are monitored. If greater than a predetermined chang e in the drive pressure or the valve position feedback is detected, then a second series of detection steps is initiated. In the second detection steps the present set point to process value relationship, such as flow rate or other process variable is compared to a stored test cycle derived set point to process value relationship for the same set point. If there is a process val ue change, then the operator is alerted as this change may indicate there is a damaged valve stem, plug, or seat problem which needs to be inspected.