Common faults of electronic expansion valves
The complex nature of electronic expansion valve systems introduces various points of failure. In practical applications, improper matching of components' installations and settings can lead to different types of malfunctions, most of which manifest in the electronic expansion valve body. Common issues include internal leakage, misalignment, and control failure.
Internal leakage can occur due to two primary reasons: excessive pressure differential and inadequate control. High pressure differentials between the inlet and outlet of the electronic expansion valve can exert thrust on the valve needle and stem, enlarging the gap between the needle and valve body and causing leakage. Moreover, reverse flow through the electronic expansion valve can generate upward thrust on the stem, resulting in reduced opening pressure when the valve is used in reverse.
Additionally, electronic expansion valves are driven by stepper motors, which enable speed and position control without the need for feedback loops. Due to the open-loop control nature of stepper motors, the controller calculates the motor's position based on the total number of pulses sent, leading to step loss during operation due to speed control, load torque, rotor inertia, and other factors.
During operation, the controller sends executing pulses to the electronic expansion valve based on sensor-detected superheat to control the valve's movement. Inertia effects during valve startup or shutdown can cause rotor lag or lead, resulting in step loss.
Furthermore, electronic expansion valves may experience execution failures, where the valve fails to operate at the specified opening as instructed by the controller. Mechanical jamming, incorrect wiring, and various electrical faults can lead to control failure in the valve mechanism.
Overall, these complexities in electronic expansion valve systems highlight the potential challenges and failure points that may arise in their operation.
