“Transparent Pump”: An Approach to Visualize Lifetime Limiting Factors in Axial Piston Pumps

Abstract

The lifetime of axial piston pumps is depending on the application and it’s overall robustness to external loads, but even in ideal conditions pumps will fail eventually. The analytics to this problem are known to pump manufacturers. Bearing and shaft calculations paired with FEM models are invaluable tools, however the main questions remain with the rotating kit — cylinder block, piston, and slippers. If properly designed these parts should theoretically outlast the finite lifetime parts, such as roller bearings due to their hydrostatic and hydrodynamic bearings. In reality however failures still occur due to fatigue or other factors such as contamination or wear. This paper describes the approach to measure and quantify the physical effects that occur in the lubricating gaps of axial pumps by means of simulation and measurements. Simulations are done with cooperation of Purdue University and the Caspar FSTI tool. These simulations are used to locate potential lifetime affecting areas and analyze them. The analysis includes temperature and pressure distributions in the gap with changing operating conditions and studies of the influence of wear and deformation on the parts that are forming the lubricating gaps. After the most critical areas are located within the simulation environment, gap and temperature sensors are placed right at these critical locations. This is planned at two of the three main lubricating gaps — slipper and swash plate as well as cylinder block and valve plate. In addition pressure sensors are placed within many critical areas of the pump, such as the transitional zone between high pressure and low pressure on the valve plate, as well as in the displacement chamber. The first results for the slipper/swashplate investigation of this approach will be shown in this paper.