The pressure difference (moving force) of the main valve repaired by the excavator appears repeatedly, that is, the faster the flow of the balance hole, the larger the flow, which is determined by the amount of oil escaping from the pilot valve. In addition, the greater the circuit pressure, the more oil, and the spring of the pilot valve becomes soft? Loosen the adjusting screw so that the low pressure can open the pilot valve, so the set pressure should also be reduced. (refer to conical valve core for repair) the leakage valve of pilot valve is not installed properly, resulting in oil leakage. If the leakage is small, it is not a big problem. When the leakage is large, the main valve acts, and the oil escapes from the oil port (reason? Refer to the cone valve core type for repair). The opening of the pilot valve is poor for excavator repair
The path indicated by the arrow is blocked and the pressure is set to rise because the resistance causes the same amount of oil to flow through the circuit higher than usual. The main valve is not open. (the reason for the poor opening refers to the conical valve core type) the balance hole is blocked, the hole is blocked, the differential pressure of the main valve is increased, the valve is opened in advance, and the pressure drop is set. If the hole is closed, the main valve opens after the circuit reaches the opening pressure of the pilot valve, and opens under the pushing pressure of the pressure. Even if you want to return, the balance chamber becomes a vacuum and cannot return. It becomes an open state.
The spring of the main valve softens, and even the pressure difference on both sides of the main valve will not move, so the set pressure will drop. Replace the spring at this time. If the main valve cannot move due to the influence of dirt, it can only be opened or closed to death. Even if the action is blocked, the pressure difference is smaller than the position where the valve cannot be opened at ordinary times, so the set pressure rises. On the contrary, when the pressure difference is not lower than normal, the valve cannot be closed. Therefore, when the circuit pressure is lower than the set pressure, the valve must be closed.
When you do the following things will change the performance of the valve installed, so it is absolutely prohibited to do it. Replace irregular spring. Handle the seat and change the caliber. The edge of the balance hole (lifting type) is rounded or damaged, and the diameter is changed. (pilot type)
