1. Main relief valve
The main relief valve sets the maximum pressure during the entire hydraulic system operation. When the system pressure exceeds the set pressure of the main relief valve, the main relief valve is opened to overflow the hydraulic oil back to the fuel tank to avoid excessive pressure in the oil circuit to protect the entire hydraulic system.
2.Working principle
The main relief valve is installed between the pump port side (P) and the oil return channel (4): when the system pressure P is lower than 31.9MPa (325kg / cm²): the pressure of the poppet (2) on the spring (1) Close down, no oil flows in the small hole in the unloading plunger (3), and the lifting head (2) is firmly fixed under the action of the Zen spring force. At this time, the pressure oil of the system is disconnected from the fuel tank path, and the system pressure can be maintained.
When the system pressure P is higher than 31.9MPa (325kg / cm²): the lifting head (2) is pushed to the left against the force of the spring (1), and oil flows in the small holes in the unloading plunger (3), unloading The plunger (3) was pushed to the left due to the pressure difference between the front and back. The pressure oil returned to the tank through the oil return channel, and the system pressure dropped to 31.9 MPa (325 kg / cm²).
When the system pressure P is higher than 31.9MPa (325kg / cm²): the lifting head (2) is pushed to the left against the force of the spring (1), and oil flows in the small holes in the unloading plunger (3), unloading The plunger (3) was pushed to the left due to the pressure difference between the front and back. The pressure oil returned to the tank through the oil return channel, and the system pressure dropped to 31.9 MPa (325 kg / cm²).
2.Secondary overflow
(1) Structural function
Increase the pressure of the hydraulic system for a short period of time, lasting about 5-8 seconds. Use this feature when encountering large rocks or tree roots during the excavation
(2) Working principle
There is a control button on the operation handle. Pressing it can control the tapping solenoid valve to switch on the pilot control oil, as shown in the figure below: