Optimizing the Performance of the Compare II Leak Calibration System

Abstract

The Compare II leak calibration system at Sandia National Laboratories has been used for the secondary calibration of leaks for over 30 years. This system calibrates leaks by the direct comparison of an unknown leak with a standard reference leak using a commercial leak detector. Over the years the leak detector remained the same but other components were changed such as replacing the oil diffusion pump with a turbomolecular pump, a new temperature chamber for the unknown leak, and using a molecular drag pump instead of a rotary vane pump. Testing on this system was conducted for two reasons. First was to determine the optimum operating conditions to enable this system to be used at peak efficiency. The second is this system is planned to be replaced with a newer system in the near future and this testing will help in determining the new system's requirements. Some of the tests, for example, was determining the time for the leak rate to stabilize when first installed on the system prior to calibration, and for the leak rate to stabilize when switching between the standard and unknown leak. Data for these and other tests conducted to optimize the performance of the Compare II leak calibration system are presented. The resulting improvements reduced calibration time from 9 hours to 5 hours and increased the number of leaks calibrated per week from 3 to 5, which significantly increased operational efficiency and reduced turnaround time for the customer.