Tribological Interaction between Piston and Cylinder of a Model High Pressure Hydraulic Pump

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Abstract
Conventional high-pressure hydraulic piston pumps require a delicate balance between clearance, surface finish, and pump materials if a long, efficient life is to be maintained. A cam-operated single cylinder pump has been used to test several pump material combinations using two chemically different hydraulic fluids. The main parameters monitored were the degree of mutual electrical insulation attained and the physical drag of the piston on the cylinder due to both viscous shear and asperity interaction. It was found that for hardened steel pistons and cylinders an optimum surface finish of approximately 8 μinches CLA gave the best results with both fluids. Results are explained on the basis of micro-asperity hydrodynamic lift.