It is logical analysis which is gradually close to break. The basic idea is comprehensive analysis and condition judgment. That is to say, maintenance personnel determine the cause of failure by experience through observation, listening, touching and simple testing and understanding of the hydraulic system. When a hydraulic system fails, there are many possible causes of failure. Using logical algebraic method, the possible fault causes are listed, and then logical judgment is made one by one according to the principle of first easy then difficult. Finally, finding the fault and the specific conditions.

In the process of fault diagnosis, maintenance personnel are required to have basic knowledge of hydraulic system and strong analytical ability, so as to ensure the efficiency and accuracy of diagnosis. However, the diagnosis process is complicated, which requires a lot of inspection and verification work, and it can only be analyzed qualitatively. The fault causes of diagnosis are not accurate enough. In order to reduce the blindness and experience of the system fault detection, the traditional fault diagnosis method can not meet the requirements of modern hydraulic system. With the development of hydraulic system from continuous production to automatic control, there are many modern fault diagnosis methods.

The expert diagnosis system based on artificial intelligence, which imitates the method of solving problems by experienced experts in a certain field by computer. Through inputting the fault phenomenon into the computer by the man-machine interface, the computer can calculate the cause of the fault based on the input phenomenon and the knowledge in the knowledge base, and then output the cause through the man-machine interface, and put forward the maintenance scheme or preventive measures. These methods bring broad prospects for fault diagnosis of hydraulic system and lay a foundation for fault diagnosis automation of hydraulic system. However, most of these methods require expensive detection equipment, complex sensor control system and computer processing system. Some of them are difficult to study and are generally not suitable for field application. A simple and practical method for fault diagnosis of hydraulic system is introduced below.