Embedded Positioner with the Ability to Reduce the Variability Generated by Friction in Control Valves

A pneumatic control valve with an electropneumatic positioner is an essential element in the process industries, whatever the segment. Almost all industrial plants in the world have valves of this nature in significant quantities. The positioner is the interface between the control system and the control valve itself. As the valve is essentially a mechanical device, the positioner has the main function of serving as an secondary control loop between the primary loop controller and the control valve; and, as secondary functions, implementing the energy conversions of the actuator (electrical → mechanical) and the stem position sensor (mechanical → electrical). One of the biggest problems that afflicts the industry, with regard to valves, is the gradual increase in control loop variability due to increasing friction, proportional to valve operating time. This is the central point of this work: to develop a digital positioner that has the capacity to compensate the friction of the valve, allowing an increase in its operating time before a maintenance to change the gaskets, whose aging increases the friction index with the valve stem. Consequently, it increases the variability in the control loop into which the valve is. In addition, the equipment may act as a failure predictor.