Gravimetric Calibration of Volumetric Standards with Capacities Exceeding Five Gallons

摘要

Recently, the demand for volumetric measurements with smaller measurement uncertainties has dramatically increased. Several market-based factors are driving this trend. With record increases in the price of petrochemical products, the potential cost of measurement uncertainty is greater than ever before. The cost of downtime for high delivery volume petrochemical measuring systems also continues to increase. Meter manufacturers have developed new electronic technologies to address the need for increased accuracy. More efficient volume standards have been developed to decrease down time. These advances in measurement technologies have necessitated similar improvements in calibration technology. In response, the metrology laboratories of several State Weights and Measures programs are moving to establish gravimetric measuring capabilities for larger volume standards. This paper will examine the process of performing calibrations of large volumetric artifacts using the gravimetric method. The paper will discuss the required instrumentation, calibration materials, handling equipment, environment, and calculations. The limiting factors of the procedure and measurement uncertainties are examined. Also covered are the lessons learned as the process has developed and areas of concern that must still be addressed. Measurement results for several large volume gravimetric processes are examined.