Modern control valves with failure diagnostics

In the modern process automation industry control valves with digital positioners have the ability to communicate with the process control system. Additional important functions (automatic start-up and control loop self-optimization, alarm signals, detailed fault diagnosis) lead to a process integrated maintenance and more process plant reliability. In this paper, these possibilities and a new diagnostic software for control valves are presented. This tool only uses the sensors required for valve positioning anyway, and, in particular, by recording the control loop dynamics through evaluation of small diagnostic test signals with no mean value at short and little process disturbances so that all important control valve parameters can be monitored and determined on-line. Remarkable are the clear statements without the necessity for consulting an expert.