During the operation of hydraulic solenoid valves, there is more or less internal leakage, which is related to the structure and working principle of the electromagnetic directional valve. A certain range of internal leakage is a normal phenomenon and cannot be completely avoided. The working principle of an electromagnetic directional valve is that after the electromagnetic iron is energized, it drives the push rod to cause relative movement of the valve core, thereby opening or closing the corresponding oil hole. In order to ensure smooth movement of the valve core in the valve body, a certain gap needs to be maintained between the two, otherwise the valve core of the hydraulic solenoid valve and the valve body will be in close contact and will not be able to move under the influence of friction.

The clearance between the valve body and valve core of a hydraulic solenoid valve is called the fitting accuracy. The matching accuracy needs to be strictly controlled within precise values to ensure the stability of the quality of the electromagnetic directional valve. Excessive internal leakage directly affects the efficiency of the hydraulic system's actuator and can easily cause malfunctions such as system malfunctions.

However, it should be pointed out that the fitting clearance of hydraulic solenoid valves is not simply a pursuit of precision, but rather the most suitable solution should be selected based on the requirements of working conditions and cost considerations. As is well known, hydraulic oil in hydraulic systems is easily mixed with small impurities and is difficult to completely eliminate. The usual practice is to use a single filter screen in the fuel tank to filter impurities. But this relatively simple, low-cost filter has limited accuracy and cannot effectively filter small impurities. The matching accuracy of the electromagnetic directional valve is higher than the filtering accuracy of the filter, and it is obvious that the valve core is easily blocked by unfiltered impurities, causing electromagnetic directional valve failure. For high-precision electromagnetic directional valves, it is usually recommended to use high-precision filtering equipment such as cotton cores, which will increase the supporting cost of the entire system. Therefore, the requirements for the internal leakage size of the electromagnetic directional valve should be flexibly mastered according to actual work requirements.

Sometimes there may be problems such as oil leakage on the connection surface of the electromagnetic directional valve. It is usually necessary to check whether the installation surface and bottom plate of the electromagnetic directional valve are flat, and the material of the connecting bolts should be consistent and the torque should be the same. The often overlooked issue is the hardness of the mounting surface O-ring. Sealing rings with lower hardness should not be used for sealing high-pressure systems, and can be replaced if necessary.