Design and Simulation Study of Automatic Dead Weight Rotator for Dead Weight Testers

It is well known that the Dead Weight Testers (DWTs) or Pressure Balances (PBs) are among the finest instruments for accurate high-pressure measurement, with low uncertainties in the pressure range of a few KPa to a few GPa. During the measurement process, either the piston or the cylinder of DWTs is made to rotate either manually or through a motor to minimise the frictional forces and to distribute the lubricating fluid in the crevice of the piston and cylinder (P-C) assembly. The majority of industrial DWTs are not equipped with a motor, and hence, the weights on the piston are rotated manually, which possibly contributes to the additional tangential forces. Also, by using manual rotation, the constant rpm of the piston is very difficult to maintain. To address these issues, the authors have proposed a novel design of a mechanical instrument designated as a dead weight rotator (DWR), which is capable of rotating the weights at constant rpm and can be accommodated in any type of DWT. The design is targeted for ~30 rpm rotation of the piston and for a dead weight of up to 100kg. In addition, simulation studies based on finite element analysis are carried out on the developed design to check the effects of the operation of DWR on the dead weights. The simulation results, including stress, strain, deformation analysis, and various design aspects of the DWR, along with their limitations and future scope, are discussed in detail. Ongoing work focuses on the fabrication and experimental design, which will be reported in due course.