Portable Piston Gas Prover for Field Calibration of Flowmeters

Abstract

Summary This paper describes a newly developed, unique piston-gas-prover system and its advantages for on-site gas flowmeter calibration to improve measurement accuracy. The gas prover was tested at a natural gas flow calibration facility and at the Colorado Engineering Experimental Station Inc. (CEESI) to demonstrate its measurement performance, repeatability, and accuracy. The piston prover, with a design similar to that of an existing piston liquid prover, is bidirectional and uses a special piston to move gas through a calibrated section of known volume. It is constructed to perform on-site calibration of such flowmeters as gas turbine or orifice meters at operating conditions. The unit can easily be set up in series with a field meter for calibration. Less than 4 in. of water pressure drop is required to operate the piston through the calibrated section. In the evaluation tests, a master turbine meter was calibrated on unprocessed natural gas. Test results show turbine pulse-count repeatability to be ±0.05%. The accuracy of the piston prover was also checked in series with an air calibration system at CEESI. This study showed that on-site calibration of a gas metering device can be conducted successfully with a portable piston-gas-prover system to improve flow measurement accuracy.