BERCLAMP-ON ULTRASONIC FLOWMETER

Abstract

A clamp-on ultrasonic flowmeter includes pairs of ultrasonic transducers arranged on an exterior of a pipeline, and an electronic measuring/operating circuit for operating the transducers and for registering and evaluating measurement signals and for providing measured values of volume flow or flow velocity. The pairs are implemented as 1-traverse or 2-traverse pairs. One-traverse pairs are arranged on opposite sides of the pipeline, and 2-traverse pairs are arranged on a same side of the pipeline. At least three pairs are arranged on the pipeline and are distributed peripherally. Adjoining pairs of a number of pairs have an inner angle down to a minimum inner angle (MIA) between one another measured about a pipeline axis, which minimum inner angle obeys the following relationship:

MIA=360°/(T*N*F(T,N))

with T as number of traverses and F(T,N)=0.38+0.62*T+(0.048−0.01*T{circumflex over ( )}2)*(N−2){circumflex over ( )}2.

Claims

1-10. (canceled)

11. A clamp-on ultrasonic flowmeter working according to the travel time difference principle for measuring flow velocity, or volume flow, of a medium flowing through a pipeline of circularly shaped cross section, comprising: a plurality of pairs of ultrasonic transducers, which are arranged on an exterior of a pipeline section, wherein each ultrasonic transducer of a pair is adapted to transmit ultrasonic signals into the pipeline section and to receive ultrasonic signals of the other ultrasonic transducer of the pair, wherein the ultrasonic transducers of each pair define a measurement path and are arranged especially in a longitudinal section plane of the pipeline section; an electronic measuring/operating circuit for operating the ultrasonic transducers as well as for registering and evaluating measurement signals of the ultrasonic transducers as well as for providing measured values of volume flow or flow velocity; wherein the pairs are implemented as 1-traverse pairs or as 2-traverse pairs, wherein the ultrasonic transducers of a 1-traverse pair are arranged on opposite sides of the pipeline section, and wherein the ultrasonic transducers of a 2-traverse pair are arranged on a same side of the pipeline section, wherein at least three pairs are arranged on the pipeline section and distributed peripherally, wherein adjoining pairs of a number of pairs (N) have, in each case, an inner angle down to a minimum inner angle (MIA) between one another measured about a pipeline axis, which minimum inner angle obeys the following relationship:
MIA=360°/(T*N*F(T,N)), with T as number of traverses and F(T,N)=0.38+0.62*T+(0.048−0.01*T{circumflex over ( )}2)*(N−2){circumflex over ( )}2.

12. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein T=1 and wherein angles between different neighboring pairs differ from one another by less than 6*(N−2)° and, especially, less than 6*(N−2)°−2° and preferably less than 6*(N−2)°−4°, or wherein T=2 and wherein angles between different neighboring pairs differ from one another by less than (60/N+8−N)° and, especially, less than (60/N)+6−N)° and preferably less than (60/N+4−N)°.

13. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein T=1 and a minimum total angle (MTA) is given by the following relationship:
MTA=(N−2)*(360°/N)+MIA, wherein the minimum total angle describes a minimum angle spanned by all pairs.

14. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein the pairs are either 1-traverse pairs or 2-traverse pairs.

15. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein the pairs have an equal separation from a flow disturbance relative to a midpoint of their measuring paths.

16. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein the pairs have relative to a midpoint of their measuring paths a maximum separation of 40 ID.

17. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein T=2.

18. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein the pipeline section is a component of the clamp-on ultrasonic flowmeter and is integrated into the pipeline.

19. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein the electronic measuring/operating circuit is adapted to calculate measured values of volume flow or flow velocity via an averaging of a measured variable of the ultrasonic signals.

20. The clamp-on ultrasonic flowmeter as claimed in claim 11, wherein N is less than 6.

Description

[0033] The invention will now be described based on examples of embodiments presented in the appended drawing, the figures of which show as follows:

[0034] FIGS. 1a) and b) clamp-on ultrasonic flowmeters;

[0035] FIGS. 2a) and b) by way of example, 1-traverse arrangements of the invention;

[0036] FIGS. 3a) and b) by way of example, 2-traverse arrangements of the invention;

[0037] FIG. 1a) shows a clamp-on ultrasonic flowmeter 1 having a pair 10 of ultrasonic transducers 11 arranged as a 1-traverse pair 10.1 on opposite sides of an exterior 13.1 of a pipeline section 13. The ultrasonic transducers are arranged offset in parallel with a pipeline axis 13.2, such that a measuring path 12 between the ultrasonic transducers extends inclined relative to a flow direction of the medium. In this way, ultrasonic signals experience a flow dependent lengthening or shortening of a signal travel time. A midpoint 12.1 of the measuring path 12 lies, in such case, on the pipeline axis.

[0038] FIG. 1b) shows a clamp-on ultrasonic flowmeter 1 having a pair 10 of ultrasonic transducers 11, which are arranged as a 2-traverse pair 10.2 on a same side of an exterior 13.1 of a pipeline section 13. The ultrasonic transducers are arranged offset in parallel with a pipeline axis 13.2, such that a measuring path 12 between the ultrasonic transducers extends inclined to a flow direction of the medium. In this way, ultrasonic signals experience a flow dependent lengthening or shortening of a signal travel time. A midpoint of the measuring path 12 lies, in such case, on an inside of a pipeline wall.

[0039] In the case of a circularly shaped cross section of the pipeline, the ultrasonic transducers of a pair lie, in both cases, in a longitudinal section of the measuring tube extending along the measuring tube axis.

[0040] The pipeline section can, in such case, be part of the flowmeter, wherein in the case of construction of a measuring point the flowmeter is integrated via the pipeline section into a pipeline. The pipeline section corresponds then to a measuring tube of the clamp-on ultrasonic flowmeter. Alternatively, the clamp-on ultrasonic flowmeter has no measuring tube and the ultrasonic transducers are then placed on the outside of an existing pipeline or pipeline section.

[0041] FIGS. 2a) and b) show, schematically, arrangements of the invention of the ultrasonic transducers of a 1-traverse clamp-on ultrasonic flowmeter having three, respectively four, ultrasonic transducer pairs in a front view, wherein, for purposes of illustration, for each pair, only the upstream, or only the downstream, lying pair is shown.

[0042] In the relationship MIA=360°/(T*N*F(T,N)) with T as number of traverses, N as number of ultrasonic transducer pairs, MIA as minimum angle between any neighboring pairs and F(T,N)=0.38+0.62*T+(0.048−0.01*T{circumflex over ( )}2)*(N−2){circumflex over ( )}2, in the case of three pairs, the ultrasonic transducers (solid circles) can, for example, be spaced at an angle 120° from one another, however, the angle between two pairs can also be less, namely at least MIA, in such case, 115°, such as shown with the dashed circles. For purposes of perspicuity, the minimum angle is only shown between one pair of neighboring ultrasonic transducer pairs. The angles are measured about the pipeline axis 13.2. In the case of four pairs, the ultrasonic transducers can be spaced from one another by an angle of 90°, however, the angle can also be less, namely at least MIA, in such case, 78°. Similar considerations hold also for five or more pairs.

[0043] Especially, the number N of pairs covers a minimum total angle MTA, which is given by the following relationship: MTA=(N−2)*(360°/N)+MIA. In this way, the arrangement of the pairs is still robust and a fluctuation range of a measurement error due to a randomly selected orientation is yet smaller.

[0044] In an embodiment, when T=1, the angles between different neighboring pairs differ from one another by less than 6*(N−2)° and, especially, less than 6*(N−2)°−2° and preferably zo less than 6*(N−2)°−4°.

[0045] FIGS. 3a) and b) show, schematically, arrangements of the invention of the ultrasonic transducers of a 2-traverse clamp-on ultrasonic flowmeter having three, respectively four, ultrasonic transducer pairs in a front view, wherein, for purposes of illustration, for each pair, only the upstream, or only the downstream, lying pair is shown.

[0046] In the relationship MIA=360°/(T*N*F(T,N)) with T as number of traverses, N as number of ultrasonic transducer pairs, MIA as minimum inner angle between any neighboring pairs and F(T,N)=0.38+0.62*T+(0.048−0.01*T{circumflex over ( )}2)*(N−2){circumflex over ( )}2, in the case of three pairs (solid circles), the ultrasonic transducers can, for example, be spaced from one another at an angle 120° (solid circles), however, the angle can also be less, namely at least MIA, in such case, 37°, such as shown with the dashed circles. The angles are measured about the pipeline axis 13.2. In the case of four pairs, the ultrasonic transducers can be spaced from one another by an angle of 90°, however, the angle can also be less, namely at least MIA, in such case, 27°. Similar considerations hold also for five or more pairs. For purposes of perspicuity, the minimum inner angle MIA is only indicated between one pair of neighboring ultrasonic transducer pairs

[0047] In this way, a robust measuring performance is obtained, which is little dependent on an orientation of the ultrasonic transducers relative to the flow disturbance. A remaining, approximately constant measurement error can then be easily compensated.

[0048] In an embodiment, when T=2, the angles between different neighboring pairs differ from one another by less than (60/N+8−N)° and, especially, less than (60/N+6−N)° and preferably less than (60/N+4−N)°.

[0049] The pipeline has a circularly shaped cross section in the region of the ultrasonic transducer arrangement.

[0050] The minimum total angle MTA is, in such case, a smallest angle, which extends from a first pair of ultrasonic transducers to a last pair of ultrasonic transducers N−2.

List of Reference Characters

[0051] 1 clamp-on ultrasonic flowmeter [0052] 10 pair of ultrasonic transducers [0053] 10.1 1-traverse pair [0054] 10.2 2-traverse pair [0055] 11 ultrasonic transducer [0056] 12 measuring path [0057] 12.1 midpoint of measuring path [0058] 13 pipeline section [0059] 13.1 exterior [0060] 13.2 pipeline axis [0061] 20 electronic measuring/operating circuit [0062] N number of pairs [0063] T number of traverses [0064] MIA minimum inner angle