Method for altering deformational characteristics of controlled-clearance piston-cylinders

A new controlled-clearance pressure balance has been developed to improve the hydraulic pressure standard for pressures up to 1 GPa. For several controlled-clearance (CC) piston-cylinders, characterization experiments based on the Heydemann–Welch (H–W) model were performed to estimate the pressure dependence of the effective area. The results of the experiments, specifically, the changes in the piston fall-rate and the generated pressure in response to the applied jacket pressure, are summarized for CC piston-cylinders of different pressure ranges. At pressures higher than a few hundred MPa, the characteristics of some piston-cylinders differed from those predicted by the H–W model. In this paper, a method for altering the deformational characteristics of CC piston-cylinders is examined. It was found that adjusting the area of the outer surface of the cylinder to which the jacket pressure is applied is an effective method for obtaining deformational characteristics that satisfy the conditions of the H–W model.