Determination of nominal dimensions and permissible variations in dimensions of critical parts of foreign machinery units

Introduction. Developing and adapting domestic technologies aimed at the maintenance and repair of foreign equipment is impossible without design documentation. The object of the study was the volumetric hydraulic drive Sauer-Danfoss of 90 series consisting of a hydraulic pump 90R100 and a hydraulic motor 90M100. The purpose of the study is to determine the nominal dimensions and permissible variations in dimensions of critical parts that affect efficiency of the foreign hydraulic drive. Materials and Methods. The first series of bench tests was devoted to finding the ranges of variation of significant factors influencing the volumetric efficiency. In the second series, there were constructed regression models and by using the steepest ascend method, there were determined the values of critical parts wear and clearances in the critical parts connections affecting efficiency of the hydraulic drive Sauer-Danfoss. The nominal values of dimensions and permissible variations in dimensions of the hydraulic drive critical parts were determined by the dimensional analysis method. Results. The bench tests made it possible to determine the ranges of changes in critical parts wear and clearances in the critical parts connections of volumetric hydraulic drives that affect the volumetric efficiency. There has been proposed and implemented a comprehensive approach to determining the nominal dimensions and permissible variations in dimensions of critical parts of foreign equipment units. This approach suggests a combination of experimental studies (bench tests) and the method of dimensional analysis. For the new volumetric hydraulic drive Sauer-Danfoss series 90 the following values are received: diameter of a hole in the cylinder block under the piston 22.7+0,006 mm, piston diameter 22.7-0,004 mm, diameter of a hole in the rear cover under the spool 9.5+0,004 mm, spool diameter 9.5-0,0025 mm. Discussion and Conclusion. There have been determined the nominal values of dimensions, permissible variations in dimensions of critical parts, and the values of technological clearances in the critical parts connections of the new volumetric hydraulic drive Sauer-Danfoss series 90 that affect its efficiency. The results obtained are the basis for the development of technology to restore the efficiency and increase the durability of the volumetric hydraulic drive units of foreign origin.