SPIRAX SARCO POSITIONER EP500

The EP500 is a 2 wire loop powered positioner requiring a 4-20 mA control signal, and is designed for use with linear pneumatic valve actuators. The positioner compares the electrical signal from a controller with the actual valve position and varies a pneumatic output signal to the actuator accordingly.

Description

SPIRAX SARCO POSITIONER EP500

Introduction-

The SPIRAX SARCO POSITIONER E500 is a 2 wire loop powered positioner requiring a 4-20 mA control signal, and is designed for use with linear pneumatic valve actuators. The positioner compares the electrical signal from a controller with the actual valve position and varies a pneumatic output signal to the actuator accordingly. A mounting kit is supplied to suit all pneumatic actuators compliant with the NAMUR standard.

Operating principle-

The current signal (1) flows in the coil (2) and generates a magnetic field which attracts the flapper (3) tapping the nozzle (4). As a consequence of this the pressure inside the actuator increases and the valve moves. When the valve stem (5) moves it generates through the feedback lever (6) and the feedback spring (7) a negative feedback which moves the flapper away from the nozzle and stops the valve movement.Changes in the current signal will induce changes in the valve positioning.This mechanism will build a linear correspondence between the current signal and the valve position expressed in percentage of the valve stroke. The valve opening at 4 mA and at 20 mA can be adjusted manually as illustrated in Figure 1.