The methodology used for valve performance testing consists of comparing the valve position demand to the true valve position measured by a dedicated position sensor. The ValveTester is particular helpful for evaluating control valve performance during normal operation.
With a user-defined 4-20 mA valve position command signal and a dedicated valve position feedback and any other relevant actuator signals, Enero’s ValveTester technology allows for online and offline dynamic performance diagnostics.
Figure 1 shows the performance of an electro-hydraulic unit that tracks changes in valve position demand very well. In this case, the valve backlash was 0.25%.
Figure 1: Hysteresis and Resolution Test for an electro-hydraulic actuator using the ValveTester
The frequency response of a control valve is one of the most critical parameters of a control loop as it truly represents the controller response capability to rapid stochastic disturbances.
Figure 2 shows an example of the frequency response of an electro-hydraulic control valve where the cutoff period was found to be 0.5 seconds and where the HawkView tool was utilized to generate the variable frequency sine wave.
Figure 2: Control valve frequency response using the ValveTester
Figure 3 shows the valve response to command signal step change. As opposed to slower pneumatic actuators, this electrohydraulic valve-actuator dynamics are very fast.
Figure 3: Step response of an electro-hydraulic valve unit. |
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