Hydraulic Protection Jaw Crusher Hydraulic System

Principle and Commissioning Methods of the Hydraulic Protection Jaw Crusher Hydraulic System:

1. The system circuit is divided into three sections with different pressures using check valves and hydraulically controlled check valves. The pressure values of these three sections should be determined based on the minimum pressure required for the material to be crushed at the site.

2. Due to the nature of this hydraulic system's operation, the pump may frequently remain idle during crushing operations, with leaked oil being continuously replenished by the hydraulic accumulator. When the oil pressure in the accumulator (and its circuit section) drops below the controller's set pressure, the pressure controller sends a signal, causing the pump to start running; when the pressure rises to the pressure controller's switching point, the pump stops running. The lower limit of the pump's working pressure and the set pressure value of the accumulator pressure controller are determined based on the working pressure required for crushing operations. The lower limit of the pump's working pressure is adjusted to be slightly higher than the set pressure of the accumulator pressure controller; the action pressure of the iron discharge relief valve is adjusted to be slightly higher than the pressure of the accumulator.

3. The main valve determines the pressure state in the high-pressure chamber of the cylinder interface.

4. During normal crushing operations, the solenoid is de-energised, and the main valve is open. At this point, pressure oil from the pump or accumulator flows into the high-pressure chamber of the cylinder to compensate for leakage and maintain the required operating pressure.

5. Troubleshooting process: When the jaws come into contact with an unbreakable object, the oil pressure inside the cylinder rises sharply, causing the pressure to reach the set value of the pressure controller. The pressure controller sends a signal, energising the solenoid of the control valve, which reverses and closes the main valve while opening the hydraulic control check valve. As a result, the oil supply from the pump and accumulator to the cylinder is cut off. The oil in the cylinder is squeezed out by the moving jaw and returns to the oil tank. After a time interval (estimated time required for obstacle clearance), once the obstacle clearance operation is completed, the power supply to the obstacle clearance solenoid valve is cut off, and the hydraulic control check valve is closed. The system then returns to the previously described normal state. The obstacle clearance process is equipped with a manual control device. Simply press the ‘Manual Iron Clearance’ button to enter the obstacle clearance state. Once the action time is complete, the system returns to the crushing operation state.

6. Manual forced obstruction clearance process: During the aforementioned obstruction clearance process, if the moving jaw is jammed by material and cannot retract, and the obstruction cannot be normally cleared, manual forced obstruction clearance can be performed. High-pressure oil is introduced into the low-pressure chamber of the cylinder, while the high-pressure chamber of the cylinder is connected to the oil tank. The pressure oil in the low-pressure chamber pushes the piston backward, forcibly pulling the moving jaw through the elbow plate to widen the discharge opening and clear the obstruction. The operating procedure is as follows: close the shut-off valve, enter maintenance mode, press the ‘Maintenance Retraction’ button, and the hydraulic system will automatically perform the aforementioned actions. After clearing the obstruction, open the shut-off valve, exit maintenance mode, and the system will return to normal operation.

7. Alarm devices for abnormal temperature, oil level, and filter status: To ensure the system operates within normal ranges, an oil temperature control device is installed. When the oil temperature exceeds the upper limit of the set temperature, the oil pump stops running until the oil temperature returns to normal. An automatic heating control system is installed. An electric contact thermometer is mounted on the oil tank to display the oil tank temperature and control the electric heater. When the oil temperature falls below the lower limit set value (recommended range: 15–25°C), the electric heater automatically activates; when it exceeds the set value, the electric heater automatically stops. A liquid level controller is installed on the oil tank. When the liquid level drops below the lower limit position of the liquid level controller, an oil tank low oil level alarm signal is issued, and the oil pump cannot start. The filter is equipped with a blockage signal device. When the filter is blocked, the pressure difference between the two ends of the filter increases, triggering an alarm to remind staff to replace the filter element promptly.

8. The electromagnetic relief valve is used to start the pump at zero pressure. After the pump starts, the control system controls the electromagnet to switch the unloading valve, increasing the system pressure. The pressure valve serves as the final safety valve for the equipment.

9. Pressure setting: The system operating pressure is set based on the strength (hardness) of the material to be crushed.

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