Control valves are exposed to natural ageing, contamination and mechanical stress during operation. Regular verification is required to ensure the precise control of the control valve’s position over the long term.
To control the valve, the RT 305.05 electro-pneumatic positioner converts a DC signal into a pneumatic measurement and control signal. Position control is carried out pneumatically via the pneumatically actuated diaphragm of the actuator. The positioner requires compressed air as auxiliary power for this purpose. Without auxiliary power, the control valve assumes the safety position ‘closed’.
The RT 305.05 is connected pneumatically and electrically to the RT 304 calibration stand. The pneumatic operating pressure is set via a precision pressure regulator on the RT 304. The electrical input signal is set via an industrial controller on the RT 304.
For verification, the valve’s end positions are approached via a controller. The zero point and the span are set using adjusting screws on the drive rod. Test points for the input signal and the stroke are compared across the entire measuring range, and the characteristic curve of the positioner is recorded.