^4fA New Piston Gauge to Improve the Definition of High Gas Pressure and to Facilitate the Gas to Oil Transition in a Pressure Calibration Chain

摘要

^7fA new piston gauge for direct operation in gas up to 100 MPa has been developed. Its design seeks to make pressure deformation of the piston-cylinder more predictable and reproducible as well as making high pressure gas operation more practical. The piston-cylinders operate directly in gas but with a liquid lubricating the piston-cylinder gap. They are integrated into interchangeable modules that include all the components that affect the pressure deformation coefficient and a dedicated lubricating liquid reservoir. The modules mount the piston-cylinder in negative free deformation in which the measured pressure is applied to the full working length of the cylinder without abrupt pressure changes. Finite element analysis has been used to compare the new design to previous approaches. The new piston gauge has been crossfloated with reference oil piston gauges to determine the agreement between theoretical and experimental values of pressure deformation. In addition to operating in gas, the piston gauge platform and piston-cylinder modules can be completely liquid filled and operated hydraulically. This facilitates its calibration and makes it a useful tool for the transition from lower pressure gas to higher pressure oil in pressure calibration chains.