CHARACTERISTICS OF CONTROLLED-CLEARANCE PISTON-CYLINDERS FOR PRESSURE RANGES UP TO 1 GPA

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 piston-cylinders, characterization experiments based on the Heydemann-Welch model were performed to estimate the effective area of them. The results for the piston-cylinders of different pressure ranges are exemplified in this paper. Some of the piston-cylinders showed different characteristics from those expected by the model at higher pressures. To change the deformational characteristics in response of the jacket pressure, the area and position of the cylinder on which the jacket pressure is applied was changed by the change in the length of the sleeve in the housing. The 500 MPa piston-cylinder with shorter sleeve showed better linearity in the relationships between the jacket pressure and the cubic root of the piston fall-rate, resulting in the estimation of the zero clearance jacket pressure with smaller error.