On the effect of the mounting angle on single-path transit-time ultrasonic flow measurement of flare gas: a numerical analysis

Abstract

The oil and gas industry needs accurate flow measurement since it is required by law, and so, considered as a field of legal metrology. Nevertheless, curves and other commonly found obstacles may affect the quality of flow measurements, due to disturbances to the flow, such as swirl and asymmetries in the velocity profile. Single-path ultrasonic flow meters are often used to measure the flow rate in flare gas installations, even though they are sensitive to such disturbances. The present paper uses numerical tools to obtain disturbed flow fields downstream from single-and double-elbow pipe installations, aiming to investigate the effects of the mounting angle on disturbed ultrasonic flow measurements, taking into consideration the contributions of all velocity components. Several transducer mounting angles from 0° to 180° are assessed varying the Reynolds numbers (based on the pipe diameter D) from 10 4 to 2 × 10 6 and axial positions up to 80D downstream from the curve. Results indicate that the correction factors for installation effects are mostly greater than in the guidelines and regulations, which suggests that, in real situations, the flow rate is being underestimated. Moreover, badly located measuring installations may be upgraded just by changing the mounting angle of the ultrasonic transducers.

Experimental Determination Influence of Flow Disturbances behind the Knife Gate Valve on the Indications of the Ultrasonic Flow Meter with Clamp-On Sensors on Pipelines

“…Efforts to determine the errors of ultrasonic flow meters’ indications in non-standard measurement conditions have been made by many researchers [ 20 , 21 ]. Aspects taken into consideration were different methods of mounting the flow meters’ heads along with the mounting accuracy [ 22 , 23 , 24 ], the influence of various types of elements disturbing the flow [ 25 , 26 , 27 , 28 ] as well as the impact of factors such as the temperature [ 29 , 30 ] or fluid pollution [ 31 ].…”

Submerged Wall Instead of a Penstock Shutoff Valve—Alternative Protection as Part of a Refurbishment

“…The accuracy of those discharge measurements are typically 0.25% for laboratory applications [37] and is in the range of 1% for very big penstocks, like that of the Three Gorges Power Station with a penstock diameter of 12.4 m [38]. It also depends on the correct location and design of the instrumentation [39][40][41], which is critical for a correct measurement.…”

A virtual flow meter downstream of various elbow configurations

“…Various studies have been conducted to assess the effects of elbow configurations on the downstream flow development, especially with regard to flow meter performance. As for numerical studies, the flow development downstream of both single and double elbows out-of-plane has been investigated with regard to varying inflow conditions (Weissenbrunner et al [34,35]), Reynolds numbers (Martins [16], Holm et al [12]), circumferential and axial mounting positions of ultrasonic flow meters and the sensitivity of the associated simulations (Martins et al [17,18]), comparison with measured data from laser Doppler velocimeters (Moniz Pereira [22]) and ultrasonic velocity profilers (Tsuzuki et al [31]). Other numerical studies have examined the flow adaptivity of ultrasonic flow meters downstream of a SE (Zheng et al [41]), the effects of pipe wall roughness downstream of a double elbow out-of-plane (Morrison and Tung [23]) and the flow behind 180 • elbows with different curvature radii (Bilde et al [1]).…”