NIST Calibration Services for Gas Flow Meters: Piston Prover and Bell Prover Gas Flow Facilities

Abstract

This document provides a description of the small and medium range gas flow calibration facilities at the National Institute of Standards and Technology (NIST), Fluid Flow Group, as reported in NIST Special Publication 250 for Test Nos. 18010C-18040C and 18050S, Flow Rate Measurements. The Fluid Flow Group can perform gas meter calibrations and special tests at flows between 3.7 x 10^-5 m³/min and 1.4 m³/min (0.001 and 51 standard cubic feet per minute) using positive displacement techniques. The flow rate of gas passing through the meter under test is determined from pressure, temperature, volume, and transit time measurements of a displaced volume of gas. Two types of displacement devices are used: mercury-sealed piston provers and bell gasometers, or bell provers. This report describes the techniques used for calibrating meters and presents the uncertainty analysis associated with such calibrations.