Hydrocarbon Liquid Flow Calibration Service

This document provides a description of a 2 liter hydrocarbon liquid flow calibration standard operated by the National Institute of Standards and Technology (NIST) Fluid Metrology Group to provide flowmeter calibrations for customers. This facility uses a passive piston prover technique where fluid is driven by pumps while the measuring piston is pushed by the fluid over a measured length during a measured time. This facility is presently operated using MIL-C7024C fluid, but other fluids could be used to offer a different range of fluid properties. The facility has uncertainty of ± 0.01 % (k=2 or approximately 95 % confidence level) over the flow range 0.19 L/min to 5.7 L/min (0.05 gal/min to 1.5 gal/min). In this document, we provide an overview of the hydrocarbon liquid flow calibration service and the procedures for customers to submit their flowmeters to NIST for calibration. We derive the equation for calculating flow at the meter under test, including the corrections for storage effects caused by changes in fluid density and connecting volume (due to temperature changes). Finally we analyze the uncertainty of the flow standard, give supporting data, and provide a sample calibration report.