Experimental validation of an analytical model for O-ring friction and leakage at high pressure

Abstract

The objective of this study was to validate existing analytical models of the friction force and leakage for O-ring seals at high pressure, where high pressure is defined as 2000 psi. A set of three pistons with 9, 6, and 4 mm bore were used in this experiment. Each piston had a single O-ring seal located in the cap end. To validate the friction force model, the force efficiency was measured by exerting a load on a piston and collecting pressure, load, and displacement measurements during constant piston descent. To validate the leakage model, a static leakage test was performed by measuring the displacement of the piston after being exposed to a constant load for an extended amount of time. Results indicated that the friction force efficiency model was valid for a range of pressures between 500 and 2000 psi, which indicates that the model for O-ring friction holds at high pressure. Results from the leakage test showed that the piston moved close to 600 microns during the first 12 hours of testing and did not move for the remaining 36 hours. This indicates that O-ring seals are leak-free, so the volumetric efficiency can be approximated to be 100%. Simple O-ring seal models can be used to compute the overall efficiency of small-scale hydraulic systems at high pressure.