Thread Content
Structure and operation of electro-hydraulic actuators: Components of the LBZN electro-hydraulic actuator: The LBZN electro-hydraulic actuator is suitable for controlling various types of valves, such as slide valves, plug valves, and butterfly valves. It consists of the following components； ?? The iSA controller and its auxiliary components — infrared remote control, electrical control box, wiring box, etc.?? Oil source and hydraulic control circuit — including level/temperature switches, pressure sensors, unloading solenoid valves, jog solenoid valves, electro-hydraulic proportional valves, motor-pump assemblies, etc. ? Actuators – including cylinders, manual mechanisms, displacement sensors, etc. Operation and fault diagnosis: 1. Valve position control – The 420mA control signal sent remotely, along with the 420mA valve position signal transmitted by the displacement sensor, are simultaneously and in real time captured by the iSA controller. Inside the iSA, these signals are compared, subjected to PID processing, and amplified. Ultimately, this results in an output current that drives the electro-hydraulic proportional valve PSV, causing the valve spool to move and thereby generating hydraulic flow. This flow controls the movement of the cylinder. Additionally, the displacement sensor POT is used to establish a position feedback loop, ensuring that the valve position remains stable. The local regulation control process is basically the same; only that the local control signals are generated internally by the iSA controller. 2. Valve position locking: In the event of signal loss, feedback loss, or tracking loss, the valve position will lock in place. When locking occurs, the proportional valve PSV loses power, cutting off the oil flow to cylinder SFG via the proportional valve, thereby causing oil to get trapped in the cylinder and resulting in the valve position being locked. 3. Jog control of valve position: When performing jog control, the locking function is first used to cut off the control oil circuit of the proportional valve. At this point, when the solenoid valve SOL1 is jogged, applying voltage to the solenoid at either the valve-opening end or the valve-closing end will activate the control oil circuit of the cylinder, thereby enabling jogged on/off control of the valve. Manual control of the valve position: This involves disconnecting all hydraulic and electrical control circuits, and using mechanical manual methods to control the valve’s operation. During manual control, the manual directional valve MV1 is switched to the “manual position” to connect the two chambers of the cylinder to the return oil channel; then the manual clutch is closed. The valve is actuated by turning the handwheel. 4. Implementation of the self-protection function: When the iSA controller receives a self-protection signal, it will mobilize all available resources to ensure the reliable execution of self-protection. 5. Routine maintenance: The electro-hydraulic actuator can be put into normal use once it has been installed and calibrated. To leverage the advantages of electro-hydraulic actuators, improve their reliability in use, keep them in good working condition, and ensure they perform as intended, users should carry out scientific maintenance of these actuators in accordance with the following requirements. Daily maintenance places certain requirements on the operator; the operator must possess the following skills: an understanding of the product’s working principles, knowledge of the function of each component, and proficiency in various operating methods. 6. Routine inspection items: The system pressure should be between 8 and 12 MPa; the parameter value should range from 0 to 100%, corresponding to the actual valve position. The input parameter value also ranges from 0 to 100%, matching the actual signal. The proportional valve parameter should be close to 0%. The parameter value for pressure should correspond to the reading on the pressure gauge, with a deviation of nearly 0%. The oil temperature should be between 15°C and 60°C. The fluid level should fall between the high- and low-level indicators, with no leaks present. There are no alarms from the ISA; the oil filter is in poor condition. 7. Fault Handling 1) The system pressure fails to rise; a low system pressure alarm is triggered. ① The shut-off valve MV2 is not closed – close MV2. ② The phase sequence of the 380VAC power supply is incorrect, causing the oil pump to rotate in the wrong direction; adjust the wiring of the 380VAC power supply. ③The liquid level is too low, causing the pump to run dry; top up or replace the oil entirely. ④The relief valve is faulty; the relief pressure was reset, and the relief valve was replaced. ⑤The internal leakage of the pump is too high; replace the pump. ⑥The oil suction filter or oil suction pipe is blocked. Replace the filter element of the oil suction filter and clean the oil suction pipe. When carrying out repairs, all the oil in the tank must be drained first, after which the maintenance access panel should be opened to proceed with the repairs. 2). The actuator does not move after a position control signal is sent from the control room. ① Lock it in place; identify the cause of the locking and then release the lock. ②The system is currently in local adjustment mode; switch to remote adjustment mode. ③The system is in jog mode, either remotely or locally; switch to remote control. ④The system pressure is too low; repeat the operation once the pressure is established. With MV1 in the “manual” position, switch MV1 to “automatic”. ⑤The spool of the proportional valve does not move; while a remote setpoint signal is applied, it is possible to check the parameters – namely the numerical values of the proportional valve. If there is no change, then, after ruling out the above possible faults, it can be assumed that there is a problem with the iSA controller or the proportional valve itself. Once the cause of the fault is identified, the corresponding component must be replaced. 3). Vibration or abnormal noise of the actuator ① Air is mixed in the cylinder; bleed air from the cylinder. ②If the cylinder wall is worn or the piston rod seal is damaged, replace the cylinder or its seals. ③The iSA controller is faulty; replace the iSA controller. 4). Loss of control over system pressure: ① Faulty pressure sensor; replace the pressure sensor. ②The iSA controller is faulty; replace the iSA controller. ③The unloading solenoid valve SOL2 is faulty; replace SOL2. ④The hydraulic check valve is faulty; replace it with a new one. 5). Excessive temperature rise in the hydraulic system: ① Pump failure; replace the pump. ②Failure of high/low pressure control; replace the pressure sensor or iSA controller. ③The iSA controller is faulty; replace the iSA controller. Replace the iSA controller