METHOD FOR DETECTION OF PIPELINE VIBRATIONS AND MEASURING INSTRUMENT

Abstract

A method for detection of pipeline vibrations with a measuring instrument connected to a pipeline system through which a medium to be measured flows, the measuring instrument having at least one transducer for detection of an input variable and for output of an output variable and at least one evaluation unit. The method involves detecting the input variable, relaying of an output variable based on the input variable to the evaluation unit, determinating the measured value of the measured variable from the output variable. Monitoring of the operating state of a system is achieved in that the measured variable characterizes the medium located within the pipeline system, that the sampling rate for detection of the input variable is at least twice as high as the frequency of the pipeline vibration and a frequency analysis of the brief fluctuations of the measured variable is conducted.

Claims

1. A method for detection of pipeline vibrations with a measuring instrument for detecting a measured variable, the measuring instrument being connected to a pipeline system through which the medium which is to be measured flows, and the measuring instrument having at least one transducer for detection of an input variable and for output of an output variable and at least one evaluation unit, comprising the following method steps: detecting the input variable by the transducer, relaying an output variable based on the input variable to the evaluation unit, determining the measured value of the measured variable from the output variable with the evaluation unit, wherein the measured variable a medium located within the pipeline system, wherein said detecting of the input variable is performed with a sampling rate that is at least twice as high as a frequency f.sub.Pipe of pipeline vibration and wherein the evaluation unit conducts a frequency analysis of brief fluctuations of the measured variable.

2. The method as claimed in claim 1, wherein for determination of the measured variable, an averaging of at least two measured values of the measured variable is performed.

3. The method as claimed in claim 1, wherein the measured variable is at least one of a flow rate of the medium, a pressure of the medium and a temperature within the medium.

4. The method as claimed in claim 1, wherein the frequency analysis is performed using a Fourier transform.

5. The method as claimed in claim 1, wherein a frequency or frequency spectrum is determined by means of the frequency analysis.

6. The method as claimed in claim 1, wherein the measuring instrument has a transmitting unit for emitting a measurement signal which has the input variable into the medium, and wherein the method has the following addition method steps: emitting a measurement signal into the medium, and receiving a transmission signal which has been transmitted through the medium by the transducer.

7. The method as claimed in claim 1, wherein the input variable is at least one of a propagation time of a measurement signal, a phase of the measurement signal, a pressure of the medium, a deformation of a body located on the pipeline system, and a phase of pipe vibrations of inlet-side and outlet-side regions of a pipe which has been set into vibrations.

8. The method as claimed in claim 1, wherein the at least one transducer is at least one of a piezoelectric transducer, a detector coil, a strain gauge, a pressure sensor, and an ultrasonic.

9. The method as claimed in claim 1, wherein a frequency spectrum of vibration of the pipeline system in a defect-free state is stored in the evaluation unit and wherein at least one of measured frequency and measured frequency spectrum is compared to the stored frequency spectrum of the vibration of the pipeline system in the defect-free state.

10. A measuring instrument for detection of a measured variable and constructed for attachment to a pipeline system through which a medium to be measured flows, comprising at least one transducer adapted for detection of an input variable and for output of an output variable and at least one evaluation unit, the evaluation unit being configured determining a measured variable characteristic of the medium flowing within the pipeline system from the output variable, and for carrying out a frequency analysis of brief fluctuations of the measured variable, wherein the at least on transducer has a sampling rate for detection of the input variable that is at least twice as high as a frequency f.sub.Pipe of a pipeline vibration of interest.

11. The measuring instrument as claimed in claim 10, wherein at least one transduce is adapted to detect at least one of a propagation time, a phase of a measurement signal, a pressure of the medium, a deformation of a body located on the pipeline system, and a phase of pipe vibrations of inlet-side and outlet-side regions of a pipe which has been set into vibrations as the input variable.

12. The measuring instrument as claimed in claim 10, wherein the measuring instrument is at least one of a flow rate measuring instrument and a pressure measuring instrument.

13. The measuring instrument as claimed in claims 10, further comprising at least one transmitting unit for emitting a measurement signal containing the input variable.

14. The measuring instrument as claimed in claims 10, wherein the at least one transducer is at least one of a piezoelectric transducer, a detector coil, a strain gauge, a pressure sensor and an ultrasonic transducer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a first exemplary embodiment of a method in accordance with the invention,

[0026] FIG. 2 shows a first exemplary embodiment of a measuring instrument in accordance with the invention based on ultrasonic waves in the medium,

[0027] FIG. 3 shows a second exemplary embodiment of a measuring instrument in accordance with the invention based on vortices produced in the medium and

[0028] FIG. 4 shows a third exemplary embodiment of a measuring instrument in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] First of all, the method according to FIG. 1 is described, and with reference being made at the same time to the physical features which are shown in FIGS. 2 to 4.

[0030] A method 1 for detection of pipeline vibrations with a measuring instrument 2 for detecting a measured variable is shown and described in FIG. 1, for the case in which the measuring instrument 2 is attached to a pipeline system 3 through which the medium which is to be measured flows. The measuring instrument 2 has at least one transducer 4 for detection of an input variable and for output of an output variable, and at least one evaluation unit 5.

[0031] In a first step 6, the input variable is detected by the transducer 4 with a scanning rate which has been fixed beforehand. Then, in a next step 7, the transducer 4 relays an output variable which is based on the input variable to the evaluation unit 5. In a next step 8, the evaluation unit 5 determines a measured value of the measured variable from the output variable. In a next step 9, at least two measured values of the measured variable are averaged in order to be able to yield a noise-free value of the measured variable. Finally, in a next step 10, the evaluation unit 5 carries out a frequency analysis of brief fluctuations of the measured variable. In the illustrated exemplary embodiment, the evaluation unit 5 determines the frequency spectrum of the fluctuations.

[0032] In this method, the sampling rate for detection of the input variable is more than twice as high as the frequency f.sub.Pipe of the pipeline vibration of interest. In this respect, it is ensured that the brief fluctuation of the measured variable which corresponds to a pipeline vibration can also be displayed time-resolved within the scope of this method.

[0033] In the illustrated method, the frequency spectrum of the brief fluctuations of the measured variable is determined. This frequency spectrum, in a next step 11, is compared to a frequency spectrum of the vibration of the pipeline system 3 in the defect-free state, which latter spectrum is filed in the evaluation unit 5. Changes in the frequency spectrum, for example, in the value or in the amplitude of the frequencies, indicate a defect in the pipeline system 3 or of components connected to the pipeline system 3. In this respect, the described method 1 constitutes an especially simple and reliable method for detection of pipeline vibrations 3 and for monitoring of the operating state of the pipeline system 3.

[0034] FIG. 2 shows a first exemplary embodiment of a measuring instrument 2 in operation which is suitable for carrying out a method as claimed in the invention for detection of pipeline vibrations. In this exemplary embodiment, the measuring instrument 2 is a flow meter which is attached to a pipeline system 3. A medium whose volumetric flow is being measured flows through the pipeline system 3 in this exemplary embodiment. The flow meter comprises a transmitting unit 12 for emitting a measurement signal which has the input variable, here, an ultrasonic signal 13, into the medium.

[0035] Moreover, the flow meter comprises a transducer 4 which is suitable for detection of the ultrasonic signal 13 with a fixed sampling rate and for output of an output variable to the evaluation unit 5. In this exemplary embodiment, the transducer 4 measures the propagation time of the ultrasonic signal 13 through the medium. Here, the transducer 4 is likewise made as a transmitting unit 12, and the transmitting unit 12 is likewise a transducer 4, both are ultrasonic transducers here. In this respect, using the measuring instrument 2 both the propagation time of the measurement signal in the flow direction of the medium and also oppositely to it are measured, the evaluation unit 5 being configured such that it determines the velocity from the propagation time difference and the flow rate of the medium therefrom.

[0036] Moreover, the evaluation unit 5 is also configured such that it carries out a frequency analysis of brief fluctuations of the flow rate and then compares the frequency spectrum which has been obtained in this way to a stored frequency spectrum which corresponds to the defect-free state.

[0037] In this respect, the described measuring instrument 2 can determine not only the flow rate of the medium, but at the same time can monitor the operating state of the pipeline system 3 or of components connected to the pipeline system 3 (such as, for example, pumps, valves, etc.).

[0038] FIG. 3 shows a second exemplary embodiment of a measuring instrument 2 which is attached to a pipeline system 3, comprising a transmitting unit 12 for emitting a measurement signal which has the input variable into the medium, a transducer 4 and an evaluation unit 5. The measurement signal which has been emitted into the medium in this illustrated exemplary embodiment is likewise an ultrasonic signal 13.

[0039] As in the above described exemplary embodiment, the evaluation unit 5 determines both the flow rate of the medium through the pipeline system 3 and also the frequency spectrum of the vibration of the pipeline system 3 from the brief fluctuations of the flow rate. In this respect, the illustrated exemplary embodiment likewise has the advantage that, on the one hand, the measured variable, here the flow rate, is determined, and also at the same time the pipeline system 3 is monitored.

[0040] In the exemplary embodiment shown in FIG. 3, the flow rate is determined by the controlled excitation of vortices by a baffle barrier 14 in the medium which can be recorded as pressure or velocity fluctuations. Here both the transmitting unit 12 and also the transducer 4 are ultrasonic transducers, the transmitting unit 12 feeding ultrasonic signals 13 as measurement signals into the medium and the transducer 4 receiving the signals which have been transmitted through the medium. In passage through a vortex the transducer records a phase-modulated signal, as a result of which the vortex frequency and in this respect the velocity of the medium can be determined.

[0041] FIG. 4 likewise shows a measuring instrument 2 which is attached to a pipeline system 3, comprising two transducers 4, here two strain gauges, and two evaluation units 5. In the illustrated exemplary embodiment the pipeline system 3 is made u-shaped, one transducer 4 and one evaluation unit 5 being attached to each leg. Here, to determine the flow rate, the pipeline system 3 through which the medium has flowed is set into vibration, the strain gauges detecting the vibrations of the respective legs. The mass flow rate is determined according to the Coriolis principle by a comparison of the phases of the vibrations of the legs.

[0042] At the same time, the evaluation units 5 determine the frequency spectrum of a brief fluctuation of the flow rate. In this respect, the exemplary embodiment of a measuring instrument 2 described here is suitable for both determining the flow rate of the medium through the pipeline system 3, and also at the same time, for monitoring the operating state of the pipeline system 3.