Linearity error in Clamp-on ultrasonic flowmeters due to the installation on pipes made of dispersive materials

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This article analyses and explains the implications that dispersive materials have over the linearity in flow measurement when a Clamp-on ultrasonic flowmeter is used. This is of capital importance because dispersive materials are commonly used in the manufacture of transducer wedges and pipes. The evaluation of this phenomenon has been tested by experimental measurement. The used setup consisted of a water flow calibration facility where a commercial Clamp-on ultrasonic flowmeter was installed on it and its flow measurement was compared with a reference flowmeter. Two experiments have been conducted. A first experiment was performed to evaluate only the effect produced by the fact that the transducer wedge is made of dispersive material. For this reason, an ultrasonic flowmeter was installed on a pipe made of non-dispersive material, in this case, an INOX pipe. Linearity error introduced by the wedge was below 1%. This error complies with the accuracy specification of the ultrasonic flowmeter given by the manufacturer (±1.5%). Finally, a second experiment consisted of installing the ultrasonic flowmeter on a dispersive pipe (PVC pipe) in order to measure the worst condition (both materials, wedge and pipe, were dispersive). Under this condition, the linearity error was increased until it reaches a value of 6.4%. Moreover, in case of a dispersive material pipe, the bigger the pipe thickness is, the bigger non-linearity error is reached.Peer ReviewedPostprint (published version

Characterization of nonhomogeneity in the dispersive properties of the materials used in pipes

This article is focused on the characterization of the lack of homogeneity in the dispersive acoustic properties of polymeric materials used in industrial pipes. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this paper, studies the variation in the propagation velocity, as a function of the intensity of the acoustic signal. In these cases, pipes made of PVC, PP and PVDF, which are commonly used in industrial installations, have been characterized. For each type of pipe, high and low acoustic intensity signals have been applied in order to reproduce working conditions that typically appear in the pipe wall below the transducers in commercial Clamp-on ultrasonic flowmeters (UFMs). Under these conditions, acoustic velocity maps have been created for the three materials under test. These maps reveal two effects that are not usually taken into account. The first one is the variation of the propagation velocity with the power density of the ultrasonic signal and the second one is the nonhomogeneous behaviour along the pipe surface. Finally, the acoustic maps reflect how a stronger acoustic signal produces greater behaviour differences in the materials under test. The characterized phenomenon of lack of homogeneity in dispersive acoustic properties, produces a variation in the zero flow error in Clamp-on UFM caused, so as not to fulfil the reciprocity criterion.Postprint (published version

Influence on the accuracy of clamp-on ultrasonic flowmeters due to the recombination of multiple propagation paths

Clamp-on ultrasonic flowmeters geometry includes four different materials in the ultrasound propagation path: wedge, coupling material, pipe and liquid. In this case, oblique incidence ultrasonic beam generated by the emitter transducer is split into several paths caused by multiple reflections in pipe wall or because of propagation mode conversion at interfaces. These multiple paths are recombined at the reception transducer aperture, producing a single signal whose amplitude and phase depend on which proportion each path contributes. The objective of this paper is to quantify this phenomenon and analyses the implications it has on the accuracy of Clamp-on ultrasonic flowmeters as a function of the fluid that flows inside the pipe. According to simulations, based on 2D ray tracing model and experimental measurements, the variations in the recombination signal at the reception transducer produces a linearity error that in case of the installation under test, Z-mode transducers configuration on PVC pipe, could reach a value of 3.2%.Postprint (published version

Splitting of the ultrasounic beam path in clamp-on ultrasonic flowmeters due to propagation through dispersive materials

This article explains how a multi-frequency ultrasonic beam path is split due to passing through dispersive materials and the implications that it has in flow measurement using a Clamp-on ultrasonic flowmeter. The importance of knowing this phenomenon is because dispersive materials are commonly used in the manufacture of transducer wedges and plastic pipes. Splitting of the ultrasonic beam path occurs when the incident angle is not normal to the surface of the pipe and a coupling wedge is necessary. The diffraction angle is produced at the boundaries among materials with different propagation velocities (according to Snell’s law), and furthermore, in dispersive materials, the propagation speed depends on frequency. Therefore, when the excitation signal contains several frequential components, each frequency travels with a different velocity. Under this circumstance, different diffraction angles are produced for each frequency at the boundaries between materials. As a result of splitting the path, the ultrasonic beam widens and the reception transducer aperture becomes too small to receive all the frequential components contained in the ultrasonic beam. Thus, when the ultrasonic beam is carried by the liquid flowing inside the pipe, the reception transducer receives different frequential contributions, producing change in its spectral composition. As a consequence of the mixing of these frequencies, the reception signal is modulated in phase and amplitude. Moreover, modulation will change as a function of frequential composition that is combined at the reception transducer. This is the origin of the linearity error in Clamp-on ultrasonic flowmeters.Postprint (published version

Zero-flow offset variation in ultrasonic clamp-on flowmeters due to inhomogeneity and nonlinearity of pipe materials

The objective of this paper is to measure the zero-flow offset variation in ultrasonic Clamp-on flowmeters produced by using pipes made of materials with a nonhomogeneous and nonlinear behavior. The evaluation of this phenomenon has been tested by the experimental measurement, the experiments consist of measuring the variation in the flow measurement when in ``no-flow condition,'' the transducers are moved along the pipe. Experimental results reveal that the reciprocity criterion is not fulfilled when nonhomogeneous and nonlinear pipe materials are used. Consequently, in these types of pipes materials, it is necessary to calibrate the offset when transducers are installed, and probably will need recalibration if the transducers are displaced to another position on the pipe. However, in installations, where it is not possible to stop flow in order to calibrate, the flowmeter will have an error in the measured value and this error will depend on the acoustic characteristics of the pipe material.Peer ReviewedPostprint (author's final draft

Characterization of nonhomogeneity in the dispersive properties of the materials used in pipes

This article is focused on the characterization of the lack of homogeneity in the dispersive acoustic properties of polymeric materials used in industrial pipes. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this paper, studies the variation in the propagation velocity, as a function of the intensity of the acoustic signal. In these cases, pipes made of PVC, PP and PVDF, which are commonly used in industrial installations, have been characterized. For each type of pipe, high and low acoustic intensity signals have been applied in order to reproduce working conditions that typically appear in the pipe wall below the transducers in commercial Clamp-on ultrasonic flowmeters (UFMs). Under these conditions, acoustic velocity maps have been created for the three materials under test. These maps reveal two effects that are not usually taken into account. The first one is the variation of the propagation velocity with the power density of the ultrasonic signal and the second one is the nonhomogeneous behaviour along the pipe surface. Finally, the acoustic maps reflect how a stronger acoustic signal produces greater behaviour differences in the materials under test. The characterized phenomenon of lack of homogeneity in dispersive acoustic properties, produces a variation in the zero flow error in Clamp-on UFM caused, so as not to fulfil the reciprocity criterion

Zero-flow offset variation in ultrasonic clamp-on flowmeters due to inhomogeneity and nonlinearity of pipe materials

The objective of this paper is to measure the zero-flow offset variation in ultrasonic Clamp-on flowmeters produced by using pipes made of materials with a nonhomogeneous and nonlinear behavior. The evaluation of this phenomenon has been tested by the experimental measurement, the experiments consist of measuring the variation in the flow measurement when in ``no-flow condition,'' the transducers are moved along the pipe. Experimental results reveal that the reciprocity criterion is not fulfilled when nonhomogeneous and nonlinear pipe materials are used. Consequently, in these types of pipes materials, it is necessary to calibrate the offset when transducers are installed, and probably will need recalibration if the transducers are displaced to another position on the pipe. However, in installations, where it is not possible to stop flow in order to calibrate, the flowmeter will have an error in the measured value and this error will depend on the acoustic characteristics of the pipe material.Peer Reviewe

Influence on the accuracy of clamp-on ultrasonic flowmeters due to the recombination of multiple propagation paths

Clamp-on ultrasonic flowmeters geometry includes four different materials in the ultrasound propagation path: wedge, coupling material, pipe and liquid. In this case, oblique incidence ultrasonic beam generated by the emitter transducer is split into several paths caused by multiple reflections in pipe wall or because of propagation mode conversion at interfaces. These multiple paths are recombined at the reception transducer aperture, producing a single signal whose amplitude and phase depend on which proportion each path contributes. The objective of this paper is to quantify this phenomenon and analyses the implications it has on the accuracy of Clamp-on ultrasonic flowmeters as a function of the fluid that flows inside the pipe. According to simulations, based on 2D ray tracing model and experimental measurements, the variations in the recombination signal at the reception transducer produces a linearity error that in case of the installation under test, Z-mode transducers configuration on PVC pipe, could reach a value of 3.2%

Linearity error in Clamp-on ultrasonic flowmeters due to the installation on pipes made of dispersive materials

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This article analyses and explains the implications that dispersive materials have over the linearity in flow measurement when a Clamp-on ultrasonic flowmeter is used. This is of capital importance because dispersive materials are commonly used in the manufacture of transducer wedges and pipes. The evaluation of this phenomenon has been tested by experimental measurement. The used setup consisted of a water flow calibration facility where a commercial Clamp-on ultrasonic flowmeter was installed on it and its flow measurement was compared with a reference flowmeter. Two experiments have been conducted. A first experiment was performed to evaluate only the effect produced by the fact that the transducer wedge is made of dispersive material. For this reason, an ultrasonic flowmeter was installed on a pipe made of non-dispersive material, in this case, an INOX pipe. Linearity error introduced by the wedge was below 1%. This error complies with the accuracy specification of the ultrasonic flowmeter given by the manufacturer (±1.5%). Finally, a second experiment consisted of installing the ultrasonic flowmeter on a dispersive pipe (PVC pipe) in order to measure the worst condition (both materials, wedge and pipe, were dispersive). Under this condition, the linearity error was increased until it reaches a value of 6.4%. Moreover, in case of a dispersive material pipe, the bigger the pipe thickness is, the bigger non-linearity error is reached.Peer Reviewe

Splitting of the ultrasounic beam path in clamp-on ultrasonic flowmeters due to propagation through dispersive materials

This article explains how a multi-frequency ultrasonic beam path is split due to passing through dispersive materials and the implications that it has in flow measurement using a Clamp-on ultrasonic flowmeter. The importance of knowing this phenomenon is because dispersive materials are commonly used in the manufacture of transducer wedges and plastic pipes. Splitting of the ultrasonic beam path occurs when the incident angle is not normal to the surface of the pipe and a coupling wedge is necessary. The diffraction angle is produced at the boundaries among materials with different propagation velocities (according to Snell’s law), and furthermore, in dispersive materials, the propagation speed depends on frequency. Therefore, when the excitation signal contains several frequential components, each frequency travels with a different velocity. Under this circumstance, different diffraction angles are produced for each frequency at the boundaries between materials. As a result of splitting the path, the ultrasonic beam widens and the reception transducer aperture becomes too small to receive all the frequential components contained in the ultrasonic beam. Thus, when the ultrasonic beam is carried by the liquid flowing inside the pipe, the reception transducer receives different frequential contributions, producing change in its spectral composition. As a consequence of the mixing of these frequencies, the reception signal is modulated in phase and amplitude. Moreover, modulation will change as a function of frequential composition that is combined at the reception transducer. This is the origin of the linearity error in Clamp-on ultrasonic flowmeters