Natural Gas Flow Calibration Service

Abstract

This document describes NIST's high pressure natural gas flow calibration service (NGFCS). Flow calibrations are conducted offsite at the Colorado Experimental Engineering Station Incorporated (CEESI) in Garner, Iowa. A parallel array of nine turbine meter working standards (TMWS) are used to calibrate customer flowmeters over a flow range from 0.25 m³/s to 9 m³/s at nominal pressures of 7500 kPa and at ambient temperatures. Over this flow range the expanded uncertainty varies from 0.25 % to 0.27 % (increasing at lower flows). All flowmeter calibrations are traceable to NIST standards. In particular, each of the nine TMWS is traceable to the NIST's primary flow standards via a bootstrap process using critical flow venturis (CFVs), while auxiliary measurements (e.g., pressure, temperature, frequency, etc.) are traceable to the appropriate NIST standard. This document provides a detailed analysis of the bootstrap procedure used to establish NIST traceability and the uncertainty of this procedure. In addition, the document gives information about the flow measurement capabilities of the NGFCS (i.e., types of meters calibrated, calibration setup, calibration procedures, a sample calibration report, etc.).