RU200262U1 - WAVEGUIDE FOR ATTACHING THE OVERLAY ULTRASONIC FLOWMETER TO PIPELINES PASSING CRYOGENIC TEMPERATURE PRODUCTS - Google Patents

Abstract

The utility model relates to measuring instruments, more specifically to means for fastening ultrasonic flow meters for pipelines operating at cryogenic temperatures, in particular to means for fastening overhead electro-acoustic transducers.

The utility model relates to measuring instruments, more specifically to ultrasonic flow meters for pipelines operating at cryogenic temperatures, in particular to overhead electroacoustic transducers.

The technical result of the utility model is the possibility of using overhead ultrasonic flow meters on cryogenic temperature pipelines.

The specified technical result is achieved due to the fact that the waveguide for attaching the attached ultrasonic flow meter is fixed longitudinally to the pipeline, where Lamb wave sensors are located at the ends of the waveguide. In this case, the ends of the waveguide are bent and brought out of the cryogenic temperature zone, and the waveguide itself is made of the same material and the same thickness as the walls of the pipeline.

Description

The utility model relates to measuring instruments, more specifically to means for fastening ultrasonic flow meters for pipelines operating at cryogenic temperatures, in particular to means for fastening overhead electro-acoustic transducers.

All types of ultrasonic flow meters (UZM) can be divided into 2 groups: cut-in UZM (UZM) and overhead UZM (UZM). They differ in the way the wave is introduced into the measured medium. VUSM use a hole specially cut in the pipeline to enter the ultrasonic signal into the measured medium. The LPGS are located on the outer surface of the pipe and use the pipe wall as a resonator that transmits the generated wave to the measured pipe.

LPGM have long established themselves in the market of both oil and gas industries.

The main element of the NUSM is an electroacoustic transducer.

The electroacoustic transducer generates an ultrasonic wave of a certain frequency, which passes through the pipe wall into the measured flow at an acute angle to the pipe axis. At the exit from the stream, the signal is received by the same sensor, which emits a counter signal. On the basis of ultrasonic sounding of the transported medium, two measurement methods are usually constructed. One is based on measuring the time of flight of the signal between the sensors, the second is based on analyzing the signal reflected in the sensor.

Time-of-flight measurement is based on the difference in sound travel time upstream and downstream, proportional to the flow velocity.

The Doppler method of measurement is based on the change in the frequency of a wave when it is reflected from a moving object depends on the speed of the object (impurity).

In existing flow meters, both methods use a clip-on sensor with an angled prism as a means of generating ultrasonic waves in the pipeline wall. In an infinite solid, a sound wave exists in the form of both transverse and longitudinal waves. Most LPGMs use a prism to convert P-waves in the prism to P-waves in the pipeline wall, which are then re-emitted into the measured medium as P-waves.

However, in a solid body bounded by surfaces, which is the pipeline wall, there are other more complex types of waves. These are Rayleigh surface waves and Lamb waves.

Lamb wave is a complex elastic wave formed by a combination of standing and traveling waves.

A Lamb wave occurs in the pipe wall if the wavelength is a multiple of the wall thickness. In this case, due to reflection from the walls, complex resonance phenomena arise in the plate, leading to the formation of a traveling wave. Each reflection from the pipe / liquid interface in the liquid generates a wave directed inward of the measured flow. The result is a wide measuring beam.

SLMMs with Lamb guided wave sensors offer particular advantages.

A wide beam has a number of advantages over other methods of generating probe radiation. These properties follow from the features of the propagation of the Lamb wave in the pipeline wall.

For a sensor wavefront with conventional shear waves, interference in the wall and in the medium will cause the measurement signals to fail.

The wavefront of the wide beam is clean and coherent, including the portion of the beam entering the sensor. The entire beam works, which is much more efficient than even with in-line sensors.

As a result, wide beam LMMs have numerous advantages over other types of SLMs.

A narrow beam can be completely blocked by solid or liquid inclusions in a gas stream, gas bubbles in a liquid, etc. This practically does not affect a wide beam, leading only to a loss of amplitude and not affecting the measurement accuracy.

No precise sensor alignment required.

Extraneous noise propagating along the flow, from valves, etc., does not enter the sensors due to the specific angles of propagation of a wide beam.

The ability to additionally control the equipment due to the detection of that part of the radiation that propagates along the wall.

The resonant nature of wave generation allows one to receive signals of higher amplitude compared to transverse wave sensors, which turns out to be especially important when working with gases.

-Lack of "blowing" of the beam allows you to achieve high dynamic ranges for measuring the flow rate and measure almost any value of the actual flow without reconfiguring the system.

Lamb wave LPGS have a number of characteristics that allow them to hold a significant market share among other types of flow meters.

LPGS do not create resistance to flow; do not create pressure losses; are not afraid of hydro and pneumatic impacts; have no moving parts.

Does not contribute to the formation of hydrates and the accumulation of dirt in the chambers of the insertion sensors; there is no physical wear of the overhead sensors by solid particles (sand, pieces of concrete, etc.), which is typical for turbine, vortex flow meters and a measuring diaphragm; there are no impulse lines susceptible to blockage due to the formation of hydrates and dirt; there is no need for a special installation of filter elements to eliminate the indicated interference; no need to use special materials to protect against corrosion caused by hydrogen sulfide; minimal maintenance costs.

For the first time, the Lamb wave Lamb sensor was developed by the founder of Controlotron Corp., USA Joseph Baumoel in 1983. The Lamb wave was generated by converting a longitudinal wave caused by a piezoelectric plate in a plastic prism with a fixed angle of inclination into a Lamb wave in the metal wall of the pipe.

This solution is also reflected in the patent US4373401.

At present, overhead flowmeters with Lamb waves are manufactured by such companies as Siemens (formerly Controlotron, USA) and Flexim (Germany).

For conventional fluid applications where the ultrasound signal loss is not very large, high-tech Lamb wave LBMs compete with cheaper solutions.

However, for applications in the gas industry, Lamb wave LPGs are indispensable, since other overhead flowmeters practically do not work in gas.

As a result, Siemens (formerly Controlotron, USA) is the only company in the world that produces flowmeters with clamp-on sensors on a calibrated pipe for commercial flow measurements with the highest accuracy (0.15% for liquid, 0.25% for gas).

The disadvantage of clamp-on Lamb wave meters is the large range of different sensor sizes available to cover the maximum pipe size range. This is caused by the resonant nature of the Lamb waves and the need to select the size of the piezoelectric element for a certain frequency, depending on the wall thickness.

The presence of a large number of standard sizes of sensors causes problems with cumbersome mounting of sensors on a pipe, especially in multichannel measurements. The number of fastening systems corresponds to the number of standard sizes of sensors.

A modern sensor with a prism (see: RU169297U, publ .: 03/14/2017.) Contains: a prism, a cover, a piezoelectric element, current leads, a damper, a thermal compensator, a pressure plate, an acoustic matching, an electrical board, an electrical connector, a thread, electrodes.

The main part of the sensor of the classic wide-beam NUSM is an inclined prism, on the beveled part of which there is a flat piezoelectric element. The angle of inclination of the piezoelectric element to the axis is necessary to fulfill the condition for the excitation of a directed wave in the material of the wall of the diagnostic pipeline. It is calculated based on the acoustic properties of the prism and pipeline materials. The dimensions of the piezoelectric element and the prism are determined by the wall thickness of the pipeline, for which the transducer is designed to operate.

The presence of a prism forces the manufacturer to deal with parasitic reflected signals inside it, match the impedances of the system elements, minimize attenuation in the prism body, etc. Rejection of the prism will significantly change the properties of the system.

The use of alternative methods for generating and receiving Lamb waves without the use of a prism will allow overcoming the disadvantages of modern LSMM and obtaining a number of innovative properties of flow meters.

New technologies in microelectronics open up new possibilities for improving the accuracy characteristics of overhead flowmeters, their convenience and expanding the range of applications.

The use of prismless methods of generating directed Lamb waves has long been considered difficult and impractical. Even the very application of Lamb waves until the 90s was limited to research purposes. This is due to their complex nature. And only the advent of sufficient computing power has revived interest in calculating the propagation of these waves.

Other methods of inputting ultrasonic waves are possible, for example, using periodic structures in the form of a multi-element guided wave transducer (MWC). This is due to the possibility of exciting the Lamb wave using a set of emitters located directly on the pipeline in the desired direction and operating in a specific sequence. Each of these elements can be considered as a source of a cylindrical wave. Wavefronts from many narrow piezoelectric elements will interfere, creating a total wavefront. The sequence is given by a tunable oscillator that can induce a predetermined superposition of acoustic fields within the sample.

In Fig. 1, one can see the formation of the direction of the wave front using periodic structures, where 1 is the wave front, 2 is the piezoelectric element, α is the input angle.

By varying the linear delay, it is possible to vary the angle of input of α radiation into the sample. With the help of a computer, these edges 1 can be delayed and synchronized in phase and amplitude in an arbitrary manner, thus controlling the direction and shape of the ultrasonic beam. By changing the frequency of the generator, you can control the wavelength and choose the mode and speed of the Lamb wave.

Structurally, MPNV are a set of piezoelectric elements 2 of various shapes, as a rule, rectangular, separated by gaps. In practice, it is a set of equidistantly spaced, electrically and acoustically decoupled strip piezoelectric elements of the same type, installed along one line on a common tread. For the purposes of flow measurement, it is the one-dimensional linear MPNV located along the pipeline axis that is suitable.

Depending on the task, the design of the sensor can be different. In the simplest case, it can be a set of piezoelectric elements glued to the sample with a period that is a multiple of the wavelength.

For example, it can be a single sensor consisting of a piezo matrix. The piezo matrix can be made of equally spaced piezoelectric rods included in a polymer base.

Another type of matrix can be made on the basis of a single piezoelectric substrate and a periodic set of electrodes.

As a substrate, you can use piezoelectric ceramics, piezoelectric composite or a thin film of polyvinylidene fluoride (PVDF). PVDF is a very flexible and cheap piezoelectric material.

The properties of the substrate determine the properties of the resulting sensor, such as flexibility, energy output, and the frequency range of the excited wave. Varying materials, the structure of the transducer, its shape allows you to select the most effective solution for a specific task, depending on the purpose of the application.

In addition to placing a prefabricated sensor on the sample, it becomes possible to form a piezoelectric layer directly on the surface of the object under study during its operation. This is possible due to the recently appeared method of applying a piezoelectric from a liquid phase.

A specially prepared liquid containing piezoelectric powder is sprayed onto the sample and after drying creates a thin layer of piezoelectric. The deposition of metallized electrodes completes the creation of the sensor directly on the object under study. In this way, sensors can be applied either during operation, or immediately upon release from production of critical structural elements for subsequent monitoring.

The development of this method will simplify and reduce the cost of methods for studying structures. At present, specialists in the field of non-destructive testing are interested in the development of such sensors. They are interested in the generation of directed waves inside thin sheets, rails, and extended metal structures. Guided wave propagation and reflection analysis enables product integrity to be monitored. The main task of developing sensors for flaw detectors using directed waves is to increase the efficiency of energy input into the traveling wave component to increase the long-range probe probing and reduce energy losses on surfaces. The probing range of long samples can reach tens of meters.

In the field of non-destructive testing, the problem is formulated differently: the purpose of wave generation is to leave it as much as possible in the pipe wall and achieve its propagation as far as possible from the source of generation.

For flow measurement, a different result is needed - the wave with the maximum energy return must enter from the pipeline into the measured medium. When the wave interacts with the passing flow, a time delay occurs in the signal proportional to the flow velocity. Thus, the wave-generating device must be designed so that the wave front moves in a medium with a given angle.

For flow measurement purposes, a wave type is needed that not only propagates along the waveguide, but is also effectively re-emitted into the medium transported inside the pipeline.

Too long a propagation distance along the wall is even harmful, as it can lead to spurious signals due to distant reflections. Therefore, the task is to develop flow meter sensors that are most suitable in frequency and design to obtain the most efficient generation of guided wave modes, leakage waves.

The development of methods and materials for the generation of Lamb waves has recently attracted more and more interest of specialists in the field of non-destructive testing. This is primarily due to the ability of these waves to propagate over considerable distances without attenuation.

Their energy losses are small, in comparison with body waves, due to the fact that the surfaces (plates or pipes) act as a waveguide, reflecting the wave in the preferred direction. This can often be the only solution to the problem of accessing a remote area of the structure and being able to control a large area from one point.

Body waves can only cover a small area of localization and scanning is required to capture a wider area. And while they can provide accurate and reliable measurements, it takes time and effort to inspect extended objects.

Lamb waves can be used to inspect any structure as long as it is a natural waveguide. Areas hidden under water, underground, under insulation and concrete become accessible for inspection.

This leads to a significant reduction in the cost and reliability of monitoring the state of the object.

The use of Lamb waves makes it possible to move from non-destructive testing (NDT) methods to methods of monitoring the state of a structure (MSC).

Traditional ultrasound diagnostic methods cannot provide continuous monitoring of the condition, as they require a large number of sensors. Traditional methods can only control small specific areas where cracks or corrosion are anticipated.

The use of Lamb waves and small, cheap sensors allows constructions to be equipped with built-in sensors or placed on finished structures. This allows continuous monitoring of the structure throughout the entire life cycle. A new kind of “smart” materials is emerging - “smart” designs. The sensor system of "smart" designs should be networked and supported by a system for collecting, processing data and making decisions.

The first “smart” structures should be oil and gas pipelines, pressure vessels, nuclear reactors, aircraft structures.

The use of innovative MPNV sensors will not only make it possible to reduce the cost of the NUSM, increase their accuracy, reliability and convenience, but also add new functions. In addition to the classic functions for measuring the flow rate and analyzing the composition, the function of monitoring the integrity of the pipeline itself can be added, which is especially important for underground and other hidden pipelines.

However, when liquefied natural gas (LNG) is used due to a sharp increase in production and consumption in the world, there is a need for a means of measuring its quantity. The peculiarity of working with LNG is that it exists at ultra-low temperatures no higher than -160 ° C. At cryogenic temperatures, a significant change in the physical properties of materials occurs, which requires the use of special methods of work in the region of such temperatures.

In this connection, the above-described known measurement methods, when the sensitive elements are in the body of the pipe, are not suitable, in view of their rapid failure under the influence of low temperatures.

As a result, bulky and expensive flow meters are used today, such as the ALTOSONIC V ultrasonic flow meter (LNG) by KROHNE (for example, see: http://www.s-ng.ru/pdf/main_1630.pdf), which are not overhead, technically complex and expensive to manufacture and maintain.

The closest analogue is the solution for the patent US2017160240A, publ .: 08.06.2017. In it, an overhead flowmeter is applied to the investigated section of the pipeline longitudinally like a waveguide of a certain shape, and Lamb wave sensors are placed at the ends of the waveguide.

In the prototype, ultrasonic transducers include an acoustic bonding plate and a bonding layer. The interconnect layer may contain a suitable interconnect material such as Teflon tape, grease, gel, or other viscous material applied to the surface of the interconnect plate that faces the conduit to provide an acoustic connection between the interconnect plate and the conduit.

The ultrasonic transducer is located inside the ultrasonic transducer frame, which abuts against the ultrasonic transducer from opposite sides and encloses a spring that applies force to the inner surface of the ultrasonic transducer frame and to the upper part of the ultrasonic transducer. The frame of the ultrasonic transducer additionally adjoins the inner walls of the housing on three sides and contacts the guides along which the frame of the ultrasonic transducer slides to manually move the ultrasonic transducer to the required position inside the housing.

Thus, the compressed spring maintains an acoustic bond between the connecting plate, the connecting layer and the outer surface of the pipeline. When the latches are released or open, a spring within the ultrasonic transducer frame lifts the housing until the bottom edge of the housing releases the top of the support plate that allows the housing to rotate, thereby exposing the ultrasonic transducers through a hole in the bottom of the housing for easy access. ...

The technical problem of the prototype is the impossibility of using this overhead flowmeter at cryogenic temperatures, since the sensors are located in the zones of cryogenic temperatures and will be damaged.

The task of the utility model is to propose a solution for expanding the area of application of overhead ultrasonic flow meters (ULM) to cryogenic temperatures.

The technical result is the possibility of using overhead ultrasonic flow meters on cryogenic temperature pipelines.

The specified technical result is achieved due to the fact that the declared waveguide for attaching an overhead ultrasonic flow meter, fixed longitudinally to the pipeline that passes the products of cryogenic temperatures, where the Lamb wave sensors are located at the ends of the waveguide, characterized in that the ends of the waveguide are bent and brought out of the cryogenic temperature zone , and the waveguide is made of the same material and the same thickness as the walls of the pipeline.

The part of the waveguide in contact with the pipeline wall is cylindrical with an inner radius corresponding to the outer radius of the pipeline. It is possible that the acoustic contact between the waveguide and the pipe is made due to cryogenic lubrication, and the ends of the waveguide at the locations of the sensors are made flat.

It is possible that the waveguide is made as part of the pipeline itself, where the waveguide is welded into the pipeline, replacing the corresponding part of the pipeline wall.

Brief Description of Drawings

In Fig. 1, you can see the formation of the direction of the wavefront using periodic structures.

Figure 2 shows the principle of placing the flow meter on the pipeline by inserting into the pipe body (A - side view in section, B - top view, C - end view in section).

Figure 3 shows the principle of placing the flow meter on the pipeline by applying and using cryogenic lubricant (A - side view in section, B - top view, C - end view in section).

In the drawings: α - entry angle, 1 - wave front, 2 - piezoelectric element, 3 - pipeline, 4 - waveguide, 5 - bent end of the waveguide, 6 - sensor, 7 - welding, 8 - cryogenic lubricant.

Implementation of the utility model

To expand the area of application of the NUSM to cryogenic temperatures, it is proposed to remove all sensitive elements from the low temperature range. Since the Lamb guided Lamb wave LPGS use the metal wall of the pipeline as a waveguide, it is natural to use this property to move the sensor out of the cryogenic temperature range. For this it is only necessary to use a waveguide of the appropriate configuration.

The utility model is implemented as follows.

On the investigated section of the pipeline 3 (see Fig. 2 or Fig. 3), a waveguide 4 of a certain shape is laid longitudinally to the pipeline 3, the ends 5 of which are bent and brought outside the zone of cryogenic temperatures. Lamb wave 6 sensors are located at the ends of the waveguide. Waveguide 4 is made of the same material and the same thickness as the walls of the pipeline 3. The part of the waveguide 4 in contact with the wall of the pipeline 3 has a cylindrical shape with an inner radius corresponding to the outer radius of the pipeline 3.

Acoustic contact between the waveguide 4 and the pipe 3 is carried out by cryogenic lubricant 8 (see figure 3). The ends of the waveguide at the locations of the sensors 6 are flat.

Sensors 6 at the ends of the waveguide excite a Lamb wave 1, which propagates along the waveguide 4 and, at the point of acoustic contact with the tube 3, excites a Lamb wave with the same parameters in the tube wall. The pipe wall 3, in turn, excites ultrasonic waves 1 in the liquid inside the pipeline 3, which are reflected from the opposite wall, return to the waveguide and reach the sensor 6.

Thus, a flow meter with an additional waveguide 4 works similarly to a flow meter with sensors 6 directly on the pipe wall 3.

All dimensions of the waveguide 4 depend on the material and dimensions of the pipe 3 and are selected for a specific task.

In the described design of the waveguide 4 there is a drawback associated with the occurrence of additional acoustic contact between the waveguide 4 and the pipe wall 3. At cryogenic temperatures it is difficult to select a lubricant 8 (see figure 3) to create an immersion layer.

This problem is solved in that the waveguide 4 is made part of the pipeline 3 itself, by welding the waveguide 7 into the pipeline by welding, and replacing the corresponding part of the wall with it, as shown in Fig. 2.

In this case, the sensors 6 at the ends 5 of the waveguide 4 excite the Lamb wave 1, which is re-emitted directly into the liquid. In this case, there is no additional signal loss due to the lack of interaction with the wall.

Any type of Lamb wave sensors, both traditional and MPNV, can be used as sensors in this design.

Claims (3)

1. Waveguide for attaching an overhead ultrasonic flow meter, fixed longitudinally to the pipeline, where the Lamb wave sensors are located at the ends of the waveguide, characterized in that the ends of the waveguide are bent and brought out of the cryogenic temperature zone, and the waveguide is made of the same material and the same thickness, similar to the pipeline walls, the acoustic contact between the waveguide and the pipe is made due to cryogenic lubrication, and the ends of the waveguide at the locations of the sensors are made flat. 2. A waveguide according to claim 1, characterized in that the part of the waveguide in contact with the pipeline wall is cylindrical with an inner radius corresponding to the outer radius of the pipeline. 3. Waveguide according to claim 1 or 2, characterized in that the waveguide is made as part of the pipeline itself, where the waveguide is welded into the pipeline, replacing the corresponding part of the pipeline wall.

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