近年来，国内进口了不少其他国家早期生产的工程机械，特别是从俄罗斯进口了许多挖掘机，随着时间的推移，这些机械的可靠性在逐渐下降，特别是液压系统的故障率越来越高。为了摆脱困境，许多单位开始用国产零部件改装原有液压系统，我们发现许多改装者只注重大部件的选用和改 In recent years, many imported construction machinery imported from other countries in the country, especially the excavators imported from Russia, have gradually declined in reliability over time, especially the failure rate of hydraulic systems has come more and more The higher. In order to get out of the dilemma, many units began to use the domestic parts refit the original hydraulic system, we found that many modified only focus on the selection of large parts and change