The impact of flow dynamics in the design of flow meters and metering stations

Commercially available flowmeters are provided with a calibration certificate, based on stationary flow conditions and do not include the impact of installation effects like swirl, a-symmetry, and piping and flow dynamics. Flow pulsations, valve noise and mechanical pipe vibrations can have a considerable impact on flowmeter accuracy in gas as well as in liquid flows. International standards like ISO, AGA and API, available for several flowmeter principles, sometimes refer to swirl, flow and piping dynamic effects, though they do not specify allowable amplitudes or frequencies. Investigations on the impact of piping and flow dynamics on differential pressure, turbine, vortex and Coriolis flowmeters have been published at several occasions. Ultrasonic noise of control valves is well known as a potential source of errors on ultrasonic flowmeters. The impact of mechanical pipe vibrations on vortex and Coriolis flowmeters can result in large errors if vibrations occur in the operating range of the flowmeter. Investigations on several commercially available flowmeters of this type have reported these phenomena for vortex and Coriolis flow meters. Several manufacturers, operating companies and engineering contractors have expressed their interest in developing a well-defined test for this type of applications. An absolute criterion for allowable pulsations or vibrations can hardly be defined as the impact on flowmeters differs for each flow metering principle and/or size. Therefore individual criteria should be developed for each type of flowmeter and its application. TNO Flow Centre has defined a project proposal to develop a test for flow-dynamic effects on flowmeters for gas and liquid applications and manufacturers and operators are invited to participate.