The gravimetric test measure tank prover is accepted for use in meter verification but not approved by API as a proving device. When using a gravimetric tank prover, the most significant component is the certified weights used to calibrate the scale and the scale(s) itself. The scale is used to weigh the tank empty to establish tare weight, and also verify the weight of the product in the tank once a quantity is measured through the meter and into the scale tank. The volume amount is verified by the equipment mass weight on the scale. Once the weight of the product is determined, the product density must be verified and used to convert the mass measurement to a volumetric measurement for comparison to the meters registered volume.

Gravimetric test measure tank proving in a test lab environment is one way that displacement type prover’s manufacturers use to verify the volume of the measurement area of each size prover. When completing a water draw certification for a displacement prover, the weighted amount is determined by the amount of fluid registered between detector switch one and detector switch two. Once the weight of the distilled water is found, the temperature and pressure of the water in the prover body is used to convert to a certified volume amount. (Refer to API MPMS Chapters, 4.9.4, Chapter 12.2.4).