The excavator repair before, to carefully read the random maintenance manual, to the hydraulic system has abasic understanding of. At present, small and medium-sized excavator hydraulic system almost is composed of a maincircuit and a pilot control circuit is composed of two parts; the main circuit adopts double loop double pump variableopen systems, hydraulic pilot control are quantitative system. By reading the technical data, the main parameters ofthe system, such as the main safety valve opening pressure, pilot control pressure and flow; familiar with the principle diagram, the symbol system of the functions and relationship of each branch circuit, the function; the structure and working principle of each hydraulic components should be to understand; analysis of possible causes of a fault;control the machines to understand each hydraulic components of the location, and the connection mode. The specific diagnosis of fault, should follow the principle of "outside to inside, from easy to difficult" sequence, thepossible causes of a fault of one by one investigation.
