(Original article in German from Chemie Technik)
Valves are indispensable in modern production processes, and their reliability and functionality are essential for ensuring smooth operation. Valve diagnostics must be performed while they are installed and under process conditions to detect early malfunctioning. Existing measuring methods in valve diagnostics are not yet sufficient for Industry 4.0 applications, as they do not provide enough data for intelligent processes.
Valves must function reliably in the production process, with tightness and functionality being essential during operation. In the event of malfunctions and emergencies, it must be ensured that they move into their intended safety position to fulfill their function. Thus, monitoring reliability and operating modes is crucial.
Limits of Previous Diagnostics
Up to now, limit switches or 0 to 90° travel measurements have been used for open-close valves. Both measurements do not provide sufficient information about the quality condition of the valve. Early detection of malfunctions is not possible, as no data is collected or curves recorded.
In the case of analog-controlled valves, so-called intelligent positioners are already used. These measure the travel from 0 to 90°, have open or close reporting, measure the runtime, and the pressure in the drive, thus providing information about the valve’s condition. However, the friction forces of the drive have a negative effect, as they are included in the measurement.
New Couplings for Direct Measurement
The torsion measuring coupling (TMK) and linear measuring coupling (LMK), developed by Wesa-Control, compensate for the disadvantages of the aforementioned measuring methods. With these two measuring methods, the quality condition and reliability of installed valves can be determined, closing a gap in valve diagnostics and enabling an intelligent process.
The measuring method is a direct measurement that captures the torque or pressing forces in the valves. The measurements are not runtime-dependent but force-dependent. The method detects the quality condition of the valve in its new state and continuously compares it with the operating state. The static and dynamic torque is measured.
The torsion measuring coupling (TMK) replaces the standard coupling in rotary drives, and the linear measuring coupling (LMK) is installed in the force direction of the drive. The evaluation can be performed through the control system or other evaluation systems. Subsequently, with the direct measurement, the quality condition of the seat assembly, gland packing, and valve spindle can be examined. Changes in the friction zones can indicate alterations in the overall condition of the valve. Both rotary and linear valves provide valuable measurement results, even when stationary.