Finite element analysis of pressure distortion coefficient and piston fallrate in a simple pressure balance

A finite element method (FEM) developed by the University of Cassino and th e Istituto di Metrologia "G. Colonnetti" (IMGC, Turin) to optimize the desi gn and use of simple pressure balances was applied while the most important operating and design parameters of the piston-cylinder units were varied. In particular, the influence of size, geometrical uncertainties and superfi cial roughness on the pressure distortion coefficient and on the piston fal l rate was considered. Finally an analysis was carried out using the real c learance profile of the IMGC-100-NNtc unit based on dimensional measurement s made at the IMGC. The comparison between the experimental values obtained at the IMGC and the numerical values, of both the pressure distortion coef ficient and the piston fall rate, show excellent agreement.