Measurement system for determining physical parameters of a pipe fluid system

Abstract

A measurement system for determining a physical parameter of a piping fluid system, comprising: - a pair of constraining elements configured to reduce surface vibratory deformation at an outer surface of each end of the piping fluid system; wherein each constraining element comprises a support frame configured to be detachably mounted on a pipe of the piping fluid system; and a fixing element configured to be detachably mounted to mechanically couple the support frame with the outer surface of the pipe; - an excitation system configured to generate a mechanical vibratory spectrum at the surface of the piping fluid system; and - a vibratory measurement device configured to be mechanically coupled to the outer surface of the piping fluid system and configured to provide the mechanical vibratory spectrum of the piping fluid system.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a measurement system for determining physical parameters of a pipe fluid system. BACKGROUND

[0002] Density measurement is an important measurement in industrial processes (delivering relevant information about product and process quality). Most of the available density sensing systems are invasive, requiring insertion of a fluid contacting device into the process, partially even invasive, requiring protruding members into the flowing material. This leads to long installation times and requires interruption of the process at installation time, in addition to already high costs of the equipment, in case of retrofit also high costs, e.g. Coriolis or vibrating fork sensors. The opening in the process pipe created by the insertion of additional equipment also involves a safety hazard of potential leaks, which requires additional effort in sealing and safety measures.

[0003] For non-invasive measurement, mainly nuclear radiation based densitometers are used, where the amount of radiation absorbed by the fluid is related to the density, using calibration and theoretical models. While this technology provides robust and accurate measurements even in harsh conditions, the radioactive hazard and the high costs of using this equipment make it rather unpopular, limiting its use. SUMMARY

[0004] The vibration characteristics of a given pipe fluid system depend on several physical parameters, such as pipe wall thickness, diameter and length, material properties, fluid density, pressure, temperature, etc. Typically, the pipes of a pipe fluid system have various vibration modes, which depend on the boundary conditions of the pipe and the process conditions and / or changes of the process conditions of the fluid enclosed by the pipe, so that from the measured mechanical vibrations in the mechanical vibrations of the pipe, a certain physical property, such as the density of the fluid of the pipe fluid system, has to be determined, all parameters and their influence on the vibrations have to be known. If the required parameters are known with sufficient accuracy, the frequency of the vibration mode, which is sensitive to the considered physical property, such as the density of the fluid, can be determined by a suitable model calculation at least within a few percent of the determined physical property. This prediction can be used to identify the relevant mode in the actual vibration spectrum, even if its frequency deviates slightly from the predicted value due to tolerances in the dimension and material data.

[0005] The accuracy of the prediction of the frequency of the density sensitive mode is crucial for the determination of the physical property, in particular in case it is based on vibration measurements. The accuracy of the prediction depends on the quality of the available information about the parameters of the process, including the temperature and pressure of the process fluid of the pipe fluid system and the geometry and material data of the pipe.

[0006] Process data such as temperature and pressure are often measured in industrial processes and information can be obtained with sufficient accuracy. Parts of the piping geometry, e.g. diameter and wall thickness, can be determined from the installation documentation of the piping system and are usually constant along the process line.

[0007] However, the piping section length and the boundary conditions at the ends of any piping section have a large influence on the mechanical vibration spectrum generated by mechanical excitation. Sections of industrial piping can extend over 10 cm to 20 cm or even several meters, the ends of these sections can be coupled to various flange types, where the transition contains a wall thickness change, a conical flange transition or a butt-welded flange or a threaded connection. The large span of possible lengths can lead to large variations in the measured frequencies caused by mechanical excitation of the mechanical vibration spectrum. In some cases, the resulting frequencies of the modes sensitive to the physical property to be measured can be very low and can overlap with the vibrations of the system initiated by the coupling mechanics, thus making the discrimination of the desired density influence difficult. In other cases, too high frequencies can lead to undesirable high requirements on the sensing equipment.

[0008] Various boundary conditions that can not be known accurately in advance can additionally make the modeling and measurement of the relevant mechanical vibration modes difficult and inaccurate. For example, the perimeter of a weld can be non-uniform and the resulting local variations in the dimensions and material properties of a welded pipe can strongly influence the excited vibration modes. Threaded pipe connections can adversely affect the vibrations by creating undesirable damping. Similarly, if a piping section has local support, attached cable routing or clamping fixtures, undesirable damping can be introduced. All such design elements can cause severe vibration attenuation or frequency shifts and affect the accuracy of the predictive frequency modeling.

[0009] For these reasons, if the frequency analysis of mechanical vibrations is used to determine physical parameters of a piping fluid system, it is highly desirable to control the length of the piping section used to determine the mechanical vibration spectrum and it is highly desirable to control the boundary conditions at the two ends of the piping section and along the length of the piping section in order to measure the vibrations. It is highly impractical to expect to find a piping section in any process system that has a length and boundary conditions corresponding to the needs of the modeling of the vibration spectrum.

[0010] Aspects of the invention relate to a measurement system for determining physical parameters of a piping fluid system, a restriction element, a kit of parts comprising features of the measurement system, and the use of a restriction element having the subject matter as described in the independent claims. Advantageous modifications of the invention are set out in the dependent claims. All combinations of at least two of the features disclosed in the description, claims and figures fall within the scope of the invention. In order to avoid repetition, features disclosed according to the method will also be applied according to the mentioned system and vice versa can be claimed.

[0011] Throughout the description of the present application, the order of the program steps is presented in a way that makes the process easy to understand. However, the person skilled in the art will realize that many process steps can also be executed in a different order and lead to the same or corresponding results. In this sense, the order of the process steps can be changed accordingly. Counters are provided for some features to improve readability or make the allocation clearer, but this does not mean that there are certain features.

[0012] To achieve these and other advantages and in accordance with the purpose of the present application, as embodied and broadly described herein, there is provided a measurement system for determining physical parameters of a pipe fluid system, comprising:

[0013] - a pair of limiting elements configured to reduce surface vibration deformation at an outer surface of each end of the measurement system and / or of the pipe fluid system, wherein each limiting element comprises:

[0014] - a support frame configured to be detachably mounted on a pipe of the pipe fluid system; and

[0015] - a fixing element configured to be detachably mounted to mechanically couple the support frame with an outer surface of the pipe;

[0016] - an excitation system configured to generate a mechanical vibration spectrum on a surface of the pipe fluid system; and

[0017] - a vibration measurement device configured to be mechanically coupled to the outer surface of the pipe fluid system and configured to provide the mechanical vibration spectrum of the pipe fluid system.

[0018] According to one aspect, each of the limiting elements is configured to individually dampen surface vibrations of the pipe of the pipe fluid system at the location where the limiting element is mounted, preferably to determine and / or define a vibration spectrum of a pipe section, preferably located between the pair of limiting elements, if the vibration spectrum is generated by the excitation system.

[0019] The expansion of the measurement system can be defined by the distance between the pair of limiting elements, preferably the distance between the pair of limiting elements can determine and / or define a vibration spectrum of the pipe fluid system of the pipe at a pipe section where the measurement system is located and / or mounted.

[0020] Each limiting element can define and / or induce a local node, thereby causing the rest of the pipe, preferably between the two limiting elements, to vibrate with an amplitude of a corresponding height, in turn enabling the generation and / or measurement of a vibration spectrum, and the correlation based on a model for determining physical properties of the fluid of the pipe fluid system.

[0021] According to one aspect, the limiting elements are mounted individually to the pipe. This means that the limiting elements are not mounted and / or carry the pipe itself. The measurement system can be configured such that the pipe is not fixed and / or mounted to the environment by the limiting elements, but the limiting elements are individually mechanically coupled to the outer surface of the pipe to define local nodes of surface vibrations at the location where the limiting elements are mounted on the pipe, preferably the pipe of the pipe fluid system, with respect to the surface of the pipe.

[0022] The measurement system can determine physical parameters of the pipe fluid system, including pairs of limiting elements, wherein the limiting elements are configured to define a pipe section of the pipe fluid system for generating a vibration spectrum between the limiting elements such that a frequency analysis of the mechanical vibrations is performed. That is, because the pairs of limiting elements can control the length of the pipe section that is used to determine the mechanical vibration spectrum and to control the boundary conditions at both ends of the section of the pipe and along the length of the pipe section such that the vibrations are measured. Preferably, for such defined measurement systems, a modeling of the vibration spectrum can be calculated. To this end, the limiting elements can be configured to dampen the surface vibrations at the location where the limiting elements are mounted on the pipe of the pipe fluid system. And the pipe section that builds the measurement system can be chosen in such a way that between the pairs of limiting elements, the pipe is not mechanically coupled to the environment of the pipe, preferably in such a way that the defined measurement system is built for which a modeling of the vibration spectrum can be performed and the vibration spectrum is calculated.

[0023] The excitation of the pipe section vibrations can be performed by various solutions, for example an impact excitation using a periodic device, such as a solenoid or a manual impact hammer, or a continuous excitation using an electromagnetic or mechanical device, or simply by exploiting the system vibrations if they are strong enough.

[0024] The pipe fluid system can include any pipe configured to include a fluid. Such section of the pipe can be described by characteristic data of the pipe that characterizes the geometry and material properties of the pipe fluid system. Preferably, the section of the pipe chosen for the application of the measurement system, which is based on mechanical vibrations, is straight, without joints or additions.

[0025] The limiting elements for defining the vibration mode can be configured to be coupled to the pipe to delimit a pipe section of the pipe fluid system to modify the pipe fluid system such that a specific mechanical vibration spectrum including a specific mechanical vibration mode can be generated, wherein the limiting elements can be configured to reduce surface vibration deformations, in particular radial, lateral and bending vibration deformations of the pipe surface at the location where the limiting elements are coupled to the pipe. The limiting elements can be configured to be detachably mounted to the pipe and mechanically coupled to the pipe. The vibrations and / or preferably surface vibrations of the pipe at the location where the limiting elements are coupled are reduced and / or damped to define a predictable vibration mode of the pipe between the limiting elements.

[0026] By mechanically coupling the restriction elements to the pipe, the section of the pipe is defined for measuring the vibration properties, which can be accurately predicted by physical calculations. This enables the use of model-based calculations of the physical properties of the fluid in the pipe based on the vibration properties of the pipe fluid system.

[0027] This is not possible for any system that does not have the defined restriction of the measurement section, as any system can include flanges, connections, fittings or accessories, which add so much complexity to such a system that it is practically impossible to predict the vibration properties.

[0028] The generated mechanical vibration spectrum on the surface of the pipe fluid system changes due to changes in the fluid inside the pipe, thereby changing the physical parameters of the pipe fluid system, which in turn enables the determination of the parameters and / or conditions of the fluid of the pipe fluid system using model calculations of the vibrations and vibration modes of the pipe based on the parameters of the pipe, such as the material and / or wall thickness and / or diameter of the pipe and / or the temperature of the pipe, etc., as discussed further below.

[0029] The restriction elements can be configured to provide a suitable mechanical impedance match or impedance step to the pipe, resulting in a desired reduction in the amplitude of the vibration modes below the restriction elements. The impedance match or step is achieved by a combination of sufficient stiffness and / or mass and / or damping of the clamp related to the stiffness and mass of the pipe, and can be determined and / or adapted by numerical modeling for any pipe configuration. As a result of the impedance match / step, the restriction clamp will not show relevant radial eigenfrequencies below the frequency of the ring or bending modes of the pipe, which should be reduced or suppressed.

[0030] The distance between the restriction elements can define the length of the pipe fluid system.

[0031] Preferably, the length of the pipe fluid system can comprise 5 to 15 times the outer diameter of the pipe. Even more preferably, the length of the pipe fluid system is between 0.2 m and 1 m.

[0032] The limiting elements can be mechanically coupled to the pipe of the pipe fluid system at both ends of the pipe section to define a measurement length of the pipe fluid system. Mechanically coupled to the pipe, the limiting elements can create defined nodes of vibration at the location of the limiting elements (similar to welded flanges) by locally suppressing radial and bending vibration modes around the circumference of the pipe, wherein the mechanical vibration spectrum of the vibration modes of the pipe section between the limiting elements can be used to determine the physical parameter. In other words, the vibration of the pipe at the location of the limiting elements is reduced in such a way that the distance between the limiting elements defines a predictable vibration mode that can be excited. The reduction and / or suppression of the vibration of the pipe can preferably be implemented in a way that minimally affects the vibration mass factor. In addition, the limiting elements can exclude vibration damping effects as well as vibration sources generated in the area of the pipe outside the pipe fluid system, thereby contributing to an improved vibration signal quality compared to a measurement on an arbitrary pipe without limiting elements coupled to the pipe.

[0033] The use of these limiting elements defines a pipe fluid system in any industrial pipe system at a section of the pipe, which has a defined length and well-defined boundary conditions at both ends and along the entire length. This enables an accurate prediction of the frequency of the mechanical vibration spectrum of at least one vibration mode that can be sensitive to the physical parameter, for example the density of the fluid of the pipe fluid system. The respective sensitive mode can be determined using analytical or finite element modeling calculations. The limiting elements contribute to the exclusion of attenuation from existing components of the pipe system, such as threaded connections, mounted clamps and conduits, etc. In addition, the limiting elements can be used as a defined support for excitation and / or sensing components required for a frequency analysis method for determining the physical parameter, for example a density or viscosity measurement.

[0034] The pipe fluid system defines a pipe section of the existing pipe system that does not contain any mechanical attachment structures, such as clamps, accessories, flanges, joints, etc. The pipe fluid system can first not contain any accessories or can be stripped of accessories to define the pipe fluid system. The length of the pipe fluid system can typically be chosen to be more than 5 times the outer diameter of the pipe, preferably about 10 times the outer diameter of the pipe. For practical reasons, in particular for large-diameter pipes, the length can be limited to no more than 1 m, preferably no more than 50 cm.

[0035] The pipe fluid system is preferably defined on a straight section of the pipe, but can include bends of the pipe. Preferably, the section of the pipe defining the pipe fluid system has a constant cross-section and a constant wall thickness along the entire measurement length. The influence of boundary conditions outside the pipe fluid system can be suppressed by using the limiting elements defining the pipe fluid system.

[0036] Defining a pipe fluid system using pairs of restriction elements enables accurate prediction of the vibrational behavior of the restricted pipe section in terms of the physical properties of the enclosed fluid (e.g. density, viscosity or flow rate) by generating defined boundary conditions for the vibrating pipe section. The definition of the pipe fluid system is achieved by restricting the elements with a specific design, including fixed elements and a support frame. The fixed elements (e.g. contact rings) substantially suppress most of the radial movement (i.e. most of the radial and bending vibration components of the pipe surface at the location of the restriction elements), thereby creating a sufficient approximation of local nodes of vibration. The circumferential fixed elements can be rings with a sufficient width to reduce axial bending vibrations, or at least two consecutive cutting edges in contact with the pipe line, or at least two rings of discrete support pins. In the latter case, the minimum number of discrete support pins is related to the vibration modes used to determine the physical properties, in particular to the number of vibration nodes around the circumference. The support frame of the restriction elements can act as a positioning and alignment device for the fixed elements and can provide the required stiffness of the structure of the restriction elements.

[0037] Using the described measurement system to determine the physical parameters of a pipe fluid system provides the following components: for determining the fluid density in a process pipe, for example, in a simple, robust, non-invasive manner based on the vibrational spectral analysis of the pipe fluid system, thereby providing a solution at an acceptable cost and with a simple installation (minimum calibration required for increased use of density measurements for process monitoring and optimization).

[0038] Thereby, the described measurement system can be used to determine the physical parameters of a pipe fluid system without requiring a priori knowledge of the correlation between the vibrational spectrum of the pipe fluid system and the physical properties of the internal fluid, as required for any industrial pipe system, including fittings and flanges. This is because the pipe fluid system by using pairs of restriction elements forms a well-defined system. This well-defined measurement system can overcome the requirement for in-situ calibration of at least two calibration points for each physical property to be considered.

[0039] In other words, the described measurement system for determining physical parameters is using a vibration mode that is sensitive to the physical properties of the fluid, such as density or pressure, which are summarized under the name "ring-like vibration mode".

[0040] Advantageously, the measurement system provides a solution by which a measurement section with a desired length and well-defined boundary conditions is restricted within any industrial pipe system. This enables the determination of physical parameters, such as the density or viscosity of the fluid of a pipe fluid system, by analyzing the mechanical vibration spectrum of any pipe generated by an excitation system.

[0041] According to one aspect, the measurement system comprises a temperature sensor configured to determine a temperature of an outer surface of the pipe fluid system.

[0042] According to one aspect, the measurement system comprises a determination electronics configured to determine a physical parameter of the pipe fluid system based on the provided mechanical vibration spectrum, wherein the determination electronics is connected by electrical signals to the vibration measurement system and / or to the temperature sensor.

[0043] This means that the determination electronics is configured to determine the physical properties of the fluid of the pipe fluid system by the vibration frequency change within the mechanical vibration spectrum, preferably using a selected vibration mode and sensitivity determined from known elastic and geometric properties of the pipe fluid system.

[0044] According to one aspect, the measurement system comprises an input / output interface to input characteristic data of the pipe of the pipe fluid system and / or process fluid data of the pipe fluid system and / or to output the physical parameter of the pipe fluid system.

[0045] According to one aspect, the measurement system comprises a support structure (e.g. a cantilever beam) and / or a protective enclosure, and the vibration measurement system and the excitation system; the support structure is configured to carry the excitation system and to enable the excitation system to generate mechanical excitation pulses; the protective enclosure encloses the pair of limiting elements.

[0046] The protective enclosure protects the measurement system from external disturbances and external influences on its vibration behavior, for example by attenuating contact or contamination of the measurement section, damage to the excitation and sensors, external noise, etc. This is a way to create defined and stable boundary conditions for the vibrating pipe along the entire length of the pipe fluid system. The enclosure can be mounted around the pipe outside the limited measurement section to prevent any mechanical coupling between the limiting clamps, which could influence the vibration response, i.e. the mechanical vibration spectrum.

[0047] The limiting elements can comprise a cantilever beam to carry components for exciting vibrations, for example an electromagnetic coil carrying an impact hammer body or other excitation components. Alternatively or additionally, the limiting elements can comprise a cantilever beam to carry sensing devices for measuring the mechanical vibrations of the pipe over the length of the pipe fluid system, for example accelerometers or microphones.

[0048] According to another aspect, a limiting element for reducing surface vibration deformations (e.g. radial and / or lateral and / or bending vibration deformations) of a pipe surface of a pipe fluid system is presented, the limiting element comprising:

[0049] a support frame configured to be detachably mounted at a pipe of the pipe fluid system; and

[0050] - a fixing element configured to be detachably mounted to mechanically couple the support frame with the outer surface of the pipe.

[0051] This means that the limiting element (e.g. clamp) for reducing the annular mode at the outer surface of the pipe fluid system is configured to be detachable from the pipe.

[0052] The fixing element that suppresses the vibrations over a certain length of the pipe is configured to be detachably coupled to the pipe and configured to be in close contact with the pipe surface around the circumference of the pipe.

[0053] The fixing element can be configured to be continuous along the circumference, e.g. with a (semi-)circular cutting edge and / or comprising discrete support pins along the circumference line. Discrete support pins are easy to implement and suitable to cope with roundness tolerances, e.g. by using stud screws. Discrete support pins can preferably, but not necessarily, be arranged equidistant around the circumferential surface of the pipe.

[0054] Discrete support pins used as fixing elements can be adapted to the vibration mode to be suppressed. For example, for the so-called n2 mode, having four nodes around the circumference of the pipe, at least 4xn = 8 support pins are needed to successfully suppress this vibration mode. For higher vibration modes, more support pins are needed, always corresponding to at least four times the order of the vibration mode.

[0055] If the fixing element is implemented using discrete support pins, the support pins can preferably be aligned, i.e. arranged to build a ring, the multiple support pins can be positioned at the same angular position relative to the pipe (within the two limiting elements (relative to each other)). Preferably, the support pins should also be aligned with the position of the excitation force.

[0056] The fixing element is supported and fixed in place by a support frame that provides a dual function:

[0057] - firmly connects and aligns all components of the fixing element, in particular in case of two separate contact rings and discrete support pins, such that any relative radial displacement of the pipe circumference at all points of contact with the pipe surface is prevented.

[0058] The circumferential (preferably bending) stiffness of the frame ensures that the circumferential vibrations are strongly reduced or suppressed under the mechanical coupling area of the fixing element.

[0059] The axial bending stiffness of the frame ensures that the two contact rings within one limiting element are fixed in the same plane and thus no bending mode components (e.g. m modes) are "going through" the limiting element, i.e. nodes with respect to longitudinal bending vibrations are created under the limiting clamp.

[0060] - providing a defined mass and stiffness rigidly connected to the fixation element, thereby significantly increasing the eigenfrequency of the restriction element above the eigenfrequency of the pipe vibration frequencies to be measured. This ensures a large degree of damping of the relevant pipe vibration modes.

[0061] The support frame is configured to be detachable to enable mounting of the restriction element of a pipe enclosing a fluid system, thereby providing sufficient stiffness and clamping force for clamping. The support frame comprises at least two segments to enable mounting on an existing pipe, but additionally or alternatively the support frame can comprise a plurality of segments. The segments can be joined by hinges, latches, form fits, e.g. using dovetail, or bolted connections.

[0062] The support frame can be configured to provide sufficient stiffness for mechanical coupling of the fixation element with the outer surface of the pipe. The support frame can be configured to provide sufficient mass, corresponding to at least the mass of the pipe segment to which the fixation element is mechanically coupled, to reduce and / or dampen any radial movement of the pipe surface along the clamping line defined by the fixation element at the pipe surface to define a vibration mode.

[0063] The fixation element can be mechanically coupled to the pipe to reduce local vibrations of the pipe at the coupling site with the pipe, and can be configured to reduce and / or dampen local vibrations of the pipe within the extension of the pipe, corresponding to at least the thickness of the pipe.

[0064] According to one aspect, the support frame of the restriction element is configured to be detachably mounted at the pipe by means of several frame elements, wherein the frame elements are configured to mechanically engage to build the support frame; and the support frame is configured to comprise the outer surface of the pipe.

[0065] According to one aspect, the fixation element of the restriction element comprises a contact ring and / or a pair of contact rings and / or a pair of cutting edge rings.

[0066] The contact ring mechanically supported by the support frame is configured to be mechanically coupled to the surface of the pipe to dampen or at least reduce radial vibrations of the pipe, e.g. movement of the pipe surface, around the entire circumference of the pipe, and can have a width equal to the diameter of the pipe wall.

[0067] Alternatively or additionally, the fixation element of the restriction element comprises a pair of contact rings and / or a pair of cutting edge rings that are separate and substantially parallel, forming a substantially line contact with the pipe, along which the pipe is tightly clamped in a linear contact manner, thereby preventing any radial movement of the pipe surface along these lines. The distance between the two substantially parallel contact rings and / or cutting edge rings corresponds to or exceeds at least one pipe wall thickness to create a node on the surface of the pipe with respect to the longitudinal bending vibration modes to be measured.

[0068] According to an aspect, the axial thickness of the contact ring and / or the distance between the pair of contact rings and / or the distance between the pair of cutting edge rings corresponds at least to the wall thickness of the pipe and preferably at least to a thickness of twice the wall thickness of the pipe of the pipe fluid system.

[0069] The coupling of the individual fixing elements along the pipe within a distance corresponding to the wall thickness of the pipe can effectively reduce local vibrations of the pipe surface by explicitly defining a node of vibration at the site of the limiting element to improve the accuracy of the determined physical parameter.

[0070] According to an aspect, the fixing element of the limiting element comprises a plurality of discrete support pins arranged between the support frame and the outer surface of the pipe to mechanically couple the support frame to the outer surface of the pipe such that surface vibration deformations, e.g. radial, lateral and bending vibration deformations of the pipe surface of the pipe fluid system, are reduced.

[0071] This plurality of discrete support pins can be arranged in at least two parallel rows around the circumference of the pipe and supported by the support frame. Thereby, the number of support pins within each individual row can be at least four times the mode number n of the vibration modes which are intended to be locally suppressed at the site of the limiting element. For example, if the mode number is n2, such a mode comprises four nodes resulting in 8 pins.

[0072] According to an aspect, the fixing element of the limiting element is mechanically coupled to the support frame using a thermal compensation element to compensate the mechanical coupling with respect to thermal expansion of the pipe and / or wherein the fixing element is mechanically coupled to at least one tuned mass.

[0073] The use of a thermal expansion compensation element can compensate for differences in thermal expansion between the pipe and the limiting element. This compensation can help to keep the mechanical coupling of the limiting element to the outer surface of the pipe constant to improve the determination of the physical parameter regardless of temperature changes, since differences in the mechanical coupling can influence the vibration behavior of the pipe.

[0074] For example, springs with high stiffness for supporting each support pin coupling the support frame with the support pin can tune the contact force of the body support pin with the pipe surface. Alternatively or additionally, the frame segments can be coupled using springs at the joints between the frame segments to adjust the force of the coupling of the segments and thereby provide an overall elasticity or flexibility of the support frame. Alternatively or additionally, the support frame can be tailored to a defined flexibility to allow for thermal expansion compensation without sacrificing the vibration suppression effect.

[0075] According to an aspect, the limiting element comprises a sensor for determining the strength of the mechanical coupling between the support frame and the outer surface of the pipe via the fixing element.

[0076] The use of a temperature sensor system and / or a force sensor system enables monitoring of the thermal expansion of the coupling between the restriction element and the pipe and the resulting modified clamping force, which can influence the determination of the physical parameters. This information can then be used to compensate for the changes in the coupling, resulting in a higher accuracy of the measurements.

[0077] According to one aspect, the restriction element comprises a mobile element for adjusting the strength of the mechanical coupling between the support frame and the outer surface of the pipe.

[0078] This adjustment can be used to compensate for the thermal expansion of the diameter of the pipe.

[0079] The use of a mobile element for adjusting the strength of the mechanical coupling, such as a piezoelectric actor, a heating element, etc., enables, for example, adjusting the contact force and the effective stiffness of the support point with the surface of the pipe.

[0080] According to one aspect, the restriction element comprises a temperature sensor for determining the temperature of the outer surface of the pipe.

[0081] Since the temperature of the material of the pipe influences the vibrations of the pipe, knowing the temperature can improve the accuracy of the determined physical parameters.

[0082] According to another aspect, a kit of parts comprises the measuring system features according to the measuring system described above, preferably comprising the restriction element as described above.

[0083] Advantageously, such a kit of parts enables an operator to set up a measuring system at any arbitrary pipe system to determine the physical parameters of the corresponding pipe fluid system.

[0084] According to one aspect, the use of a restriction element as described above for a measuring system as described above is proposed.

[0085] By precisely defining the length of the pipe for developing the vibration modes, the use of a restriction element as described can improve the accuracy of the measurements using a measuring system as described above.

[0086] A method for determining the physical parameters of a pipe fluid system is provided, comprising the following steps. In one step, a pipe within the pipe fluid system is provided, the pipe fluid system having known characteristics, such as material data and / or geometry of the system, in particular having a defined length, as defined by the distance between the restriction elements.

[0087] In another step, a mechanical model vibration spectrum of the pipe fluid system is calculated using analytical or preferably more accurate finite element (FEM) calculations.

[0088] In a further step, the sensitivity of the selected vibration modes of the pipe sections within the pipe fluid system to changes in the physical properties of the internal fluid, such as density, pressure, is calculated, for example using FEM or analytical calculations.

[0089] To this end, the vibration spectrum for different densities or pressures is calculated and the sensitivity is defined as the change in frequency divided by the change in the physical property.

[0090] In a further step, a mechanical vibration spectrum of the pipe fluid system is provided, which is generated by an excitation of the pipe fluid system, and the selected vibration modes predicted in the mechanical model are identified.

[0091] In a simultaneous step, process fluid data, such as temperature and / or pressure, are provided by real-time measurements.

[0092] In a further step, the identified frequency (es) of the measurement mode (s) are related to the initial state of the physical quantities, such as the density of the fluid and / or the pressure and / or the temperature of the fluid and they are defined as initial state. The initial values of the physical quantities are preferably derived from dedicated measurements, such as probe extraction for the density of the fluid, but can also be a qualified estimate based on information about the process.

[0093] In a further step, the pipe is excited continuously or intermittently and the vibration spectrum is measured, including the extraction of the measurement mode frequencies. Additionally or alternatively, the physical quantities of the fluid pipe system can be measured, such as the temperature of the fluid and / or the pipe, and / or the pressure of the fluid.

[0094] In a further step, the changes in the physical properties relative to the initial values are calculated based on the changes in the frequencies, the sensitivities defined above and the real-time process fluid data, such as the pressure of the fluid and / or the temperature of the fluid and / or the pipe.

[0095] A method of measuring the frequency of a vibration can comprise the following steps:

[0096] In a first step, a section of a pipe of a pipe fluid system is selected. In a next step, geometry and / or material data are determined, such as the length of the section of the pipe fluid system and / or the diameter of the pipe and / or the wall thickness of the pipe and / or the Young's modulus of the material of the pipe. In a next step, frequency and sensitivity prediction calculations are performed on the pipe of the pipe fluid system using FEM and / or analytical models to provide an output of the frequencies with the selected modes at a reference temperature and a value of the sensitivity to changes in the density of the fluid and / or changes in the pressure of the fluid. In a next step, a limiting clamp is installed, a system for exciting the vibration of the pipe is installed, and a vibration sensor for determining the vibration of the pipe is installed. An electronic device is connected to the vibration sensor for signal processing and determining the physical parameters.

[0097] In a further step, the system is used to generate vibrations of the pipeline to excite the vibrations and to determine a vibration spectrum. The temperature of the pipeline is determined and at least one relevant frequency of the vibration mode is extracted from the vibration spectrum to define the parameter as a starting point. In a further step, the density of the fluid of the pipeline fluid system is determined, for example by probe extraction, and stored as an initial and / or calibration density together with the extracted frequency of the initial vibration spectrum. In a further step, the vibrations of the pipeline fluid system are generated continuously and at least one relevant frequency of at least one relevant mode is extracted from the vibration spectrum. The temperature of the pipeline fluid system is continuously measured and optionally the pressure of the section of the pipeline is determined. In a further step, the physical parameter, for example the density change of the fluid relative to the initial state, is calculated using the frequency change and a predetermined sensitivity to temperature and pressure changes.

[0098] The mechanical model vibration spectrum comprises a part or several parts of the overall mechanical vibration spectrum of the pipeline fluid system, including the pipeline, wherein the pipeline can be partially or completely filled by a fluid, such as a gas and / or a liquid and / or a mixture and / or a slurry.

[0099] Any individual vibration mode depends on the geometric data of the pipeline and / or the material properties of the pipeline, the temperature of the pipeline and the internal pressure of the pipeline and the process fluid data of the pipeline fluid system.

[0100] Alternatively or additionally, the mechanical vibration spectrum can comprise a plurality of different vibration modes for determining the physical parameter, for example the density, of the fluid within the pipeline.

[0101] If data of at least two different modes of the mechanical vibration spectrum are used, i.e. measurements of at least two different vibration modes are performed, the accuracy and reliability of the determination can be improved. In this case, the "acceptable criteria" for estimating the density or other physical parameter of the fluid must be met by both vibration modes, thereby increasing the reliability of the determination.

[0102] The mechanical excitation comprises any mechanical excitation, including a pulse that impacts the outer surface of the pipeline of the pipeline fluid system.

[0103] In a further step of the method, the determined physical parameter can be output, for example using an interface and / or a screen. This output of the determined physical parameter can comprise the most likely fluid density.

[0104] Alternatively or additionally, the method comprises the step of continuously evaluating the frequency peak shift of the mechanical vibration spectrum and determining the corresponding physical parameter, for example the density of the fluid.

[0105] Alternatively or additionally, the method comprises providing another mechanical vibration frequency spectrum at a later time, wherein the mechanical vibration frequency spectrum provided at a previous time can be used as a reference measurement, which is calibrated with a one-off probe extraction and offline density measurement to improve the accuracy of determining the physical parameter, such as the density of the fluid of the pipe fluid system.

[0106] The pipe fluid system can be any pipe configured to comprise a fluid. Preferably, the pipe fluid system can be a pipe configured to comprise a fluid and can comprise a vibration mode limiting element that facilitates defining a vibration mode of the pipe of the pipe fluid system within a defined section of the pipe. Such section of the pipe can be described by characteristic data of the pipe, which characterizes the geometry and material properties of the pipe. Preferably, the pipe section is straight without joints and additions.

[0107] Each individual limiting element can be any flange connected to the pipe, such as a welded flange and / or a butt-welded flange and / or a threaded connection. Alternatively or additionally, at least one of the limiting elements can be a limiting element configured to be mechanically coupled to the pipe to delimit a pipe section of the pipe fluid system with respect to a vibration mode for modifying the pipe fluid system to enable generating a specific mechanical vibration frequency spectrum comprising a specific mechanical vibration mode.

[0108] The distance between the limiting elements can define a length of the pipe fluid system.

[0109] The characteristic data of the pipe of the pipe fluid system can comprise geometry data of the pipe and / or the pipe fluid system, which can be generated by local measurements and / or provided by technical data and / or data about the material of the pipe and / or an expected frequency range and / or an expected vibration frequency spectrum and / or a pipe surface temperature.

[0110] The process fluid data can comprise an expected density of the fluid and / or a fluid pressure value and / or a fluid temperature and / or an expected fluid.

[0111] The mechanical model vibration frequency spectrum can be provided by a theoretical model of the pipe fluid system, preferably using finite element calculations.

[0112] In other words, a method for determining a density and / or a density change of a process fluid within a pipe is described. A mechanical vibration spectrum of a pipe fluid system can be generated by exciting the pipe fluid system to vibrate and measuring the excitation response to derive a quantitative value of a change of a physical property of the fluid in the pipe using the measured change of vibration characteristics, e.g. vibration frequencies and pre-calculated frequency sensitivities to the physical property change. Determining the physical parameter based on the measured vibration characteristics can be done using an algorithm, based on vibration characteristics and / or based on a measurement of the pipe geometry and / or with a knowledge or estimation of the pipe material properties and / or measured pipe surface temperature modeling components for providing a mutual dependency of vibration characteristics and physical properties from the above parameters.

[0113] According to one aspect, the length of the pipe fluid system is defined by vibration mode limiting elements at both ends of the pipe fluid system.

[0114] Using such limiting elements mechanically coupled to the pipe of the pipe fluid system can improve the accuracy and provide a pipe fluid system with a certain size for generating the desired mechanical vibration spectrum.

[0115] According to one aspect, the mechanical vibration spectrum of the pipe fluid system is provided by an acoustic signal acquisition system acoustically coupled to the pipe fluid system and / or a vibration measurement system mechanically coupled to an outer surface of the pipe fluid system.

[0116] According to one aspect, the method comprises filtering the provided vibration spectrum using process fluid data and a model vibration spectrum corresponding to the process fluid data.

[0117] The filtering can limit the frequency range of the provided vibration spectrum with respect to higher and lower frequency values depending on the process fluid data and the model vibration spectrum corresponding to the process fluid data. Such a limitation of the predicted frequency range based on the initial FEM calculation facilitates the identification of relevant vibration modes in the actually measured spectrum.

[0118] According to one aspect, the method comprises providing a temperature of an outer surface of the pipe fluid system and determining the mechanical model vibration spectrum additionally based on the temperature of the outer surface of the pipe fluid system.

[0119] Advantageously, the determined temperature of the outer surface of the pipe fluid system improves the accuracy compared to an estimated temperature of the fluid and / or a temperature of the pipe material of the pipe fluid system.

[0120] According to one aspect, the method comprises providing an internal pressure of the pipe fluid system and determining the mechanical model vibration spectrum additionally based on the internal pressure of the pipe fluid system.

[0121] Advantageously, the determined internal pressure of the piping fluid system increases the accuracy compared to the estimated pressure of the fluid.

[0122] According to one aspect, the physical parameters comprise a density of the process fluid of the piping fluid system and / or a viscosity of the process fluid of the piping fluid system and / or a flow rate of the process fluid of the piping fluid system.

[0123] At least for determining the viscosity of the process fluid, parts of the mechanical vibration spectrum are compared with respect to the form of the spectrum, e.g. the peak value of the mechanical model vibration spectrum or the width of the ring-down time.

[0124] According to one aspect, the characteristic data of the piping of the piping fluid system comprise a diameter of the piping and / or a thickness of the piping and / or a material of the piping of the piping fluid system and / or a length of the piping fluid system and / or an elastic material data of the pipe wall.

[0125] According to one aspect, the theoretical model of the vibration spectrum of the piping fluid system is based on a finite element calculation or an analytical model calculation for the piping fluid system used for the measurement.

[0126] Advantageously, determining the theoretical model of the vibration spectrum based on a finite element calculation enables an increased accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0127] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. The drawings show:

[0128] Figure 1 schematic illustration of a piping fluid system with a restriction element attached to the piping and a corresponding vibration mode;

[0129] Figure 2 schematic illustration of different types of restriction clamps;

[0130] Figure 3 schematic illustration of different types of restriction clamps comprising discrete support points;

[0131] Figure 4 schematic illustration of a measurement system for determining physical parameters of a piping fluid system;

[0132] Figure 5 schematic illustration of a restriction clamp with a continuous contact ring;

[0133] Figure 6 schematic illustration of a restriction clamp with two rows of discrete support points acting as a contact ring;

[0134] Figure 7schematic of a restriction clamp with two rows of discrete support points acting as a contact ring, comprising elastic elements;

[0135] Figure 8 schematic of a restriction clamp comprising a compliant frame; and

[0136] Figure 9 schematic of a restriction clamp with a flexible frame having two frame segments and an additional tuned mass;

[0137] Figure 10 schematic of a) a circumferential vibration mode; and

[0138] b) an axial vibration mode. DETAILED DESCRIPTION

[0139] Figure 1 A pipe fluid system 110 is schematically depicted comprising a pipe 116 and a flowing or stationary fluid 120 at a section of the pipe 116 comprising a pipe joint 118, wherein restriction elements 112, 114 are mechanically coupled to the pipe 116. As such, the section of the pipe 116 is modified to build a pipe fluid system 110 having a defined length between the two restriction elements 112, 114 for vibration-based density sensing measurements, which are less sensitive to disturbances outside the section. This means that in comparison to a form of the pipe in the middle of the pipe fluid system 140 during vibration, the restriction elements 112, 114 are configured to locally reduce the vibration at the location where they are coupled to the pipe 16, as indicated by the constant form of the pipe 142. Respective vibration modes 140, 160 are indicated as examples. The modes are characterized by the deformation of the pipe in two mutually perpendicular planes, respectively. A circumferential deformation 140 and a longitudinal deformation 160. Any combination of these two deformation types is possible, characterized by a combination of characteristic numbers n and m, which are related to the number of nodes of the vibration in a given plane. Examples refer to a combination n2m1, but other vibration modes can be used to perform the determination of the physical parameter.

[0140] Figure 2 Examples of configurations of restriction elements in the form of longitudinal cross sections 210, 220, 230 and a lateral cross section 240 are schematically depicted, the lateral cross section 240 comprising a continuous contact ring 232 mechanically coupled to the pipe 116 by a frame 250 surrounding the pipe, wherein the contact ring is configured as one ring comprising a defined width, as comprised by the restriction element 210; two narrow rings, as comprised by the restriction element 220; or two rings formed as cutting edges, as comprised by the restriction element 230.

[0141] Figure 3An example configuration of a restriction element is schematically depicted by longitudinal cross sections 310 and 320 and lateral cross sections 330, 340, 350, 360, and 370, where the fixation element comprises various numbers and arrangements of discrete support pins arranged, for example, in two rows 310 or three rows 320, equidistantly arranged 330, 340, 360, 370, or irregularly arranged 350, with different numbers of support pins for mechanically coupling the frame of the restriction element to the pipe of the pipe fluid system. The frame of the restriction element corresponds to the frame of the restriction element shown in Figure 2

[0142] Figure 4 A measurement system 400 for a pipe 116 is schematically depicted, which comprises restriction elements 112, 114 to delimit a section of the pipe 116 for vibration measurement. The measurement system 400 comprises an excitation system 412 for generating mechanical vibrations, for example by an impact on the surface of the pipe 116. The excitation system 412 is coupled to a cantilever 410 to be mechanically separated from the pipe 116 within the pipe fluid system 110. The measurement system 400 comprises a vibration measurement system 430, for example a vibration sensor, and a temperature sensor 440, as well as a protective enclosure 450 covering the measurement section comprising the pipe fluid system 110. The acceleration acquisition system 430 and the temperature sensor 440 are coupled by signals to determining electronics 420. Outside the section of the pipe 116 containing the pipe fluid system 110, the pipe 116 is connected to a pipe joint 118 and to pipe flanges 174 at each side of the pipe 116.

[0143] Figure 5 A restriction element 510 is schematically depicted, which comprises two consecutive contact rings 517 to provide a double contact line configured to be mechanically coupled to the pipe 116. The restriction element 510 comprises two sections of a support frame 512, 514 configured to be coupled to the pipe 116 by engagement elements 516 and 518.

[0144] Figure 6 A restriction element 610 is schematically depicted in perspective view a) and lateral cross section b), which comprises two rows of discrete support points 620 acting as fixation elements configured to couple a support frame 614 to the pipe 116.

[0145] Figure 7 ​A restriction element 710 is schematically depicted, shown in respective views a) and lateral cross-section b), comprising two rows of discrete support points 720 acting as fixation elements, configured to couple a support frame 714 containing elastic members 716, e.g. springs, to compensate for thermal expansion differences, i.e. to keep constant the mechanical coupling force between the support frame 714 and the pipe 116.

[0146] Figure 8 A restriction element 810 is schematically depicted, comprising a compliant frame 818, i.e. a frame, having a tailored bending stiffness, aimed at achieving a small compliance to thermal expansion differences, and still maintaining the required stiffness for vibration suppression. This tailored bending stiffness can be provided by the frame 814, the specific form element 818 and the choice of material and thickness of the frame 814 as shown in Figure 8 The frame 814 is coupled to the pipe 116 through discrete support points 820, and the four segments of the support frame 814 are coupled through joining elements 816, e.g. threaded joints.

[0147] Figure 9 A restriction element 910 is schematically depicted, corresponding to the restriction element 810 of Figure 8 but having two segments of the support frame 914, configured to be flexible through a specific form element 918. In addition, the restriction element 910 comprises at least one tuned mass 930, mechanically coupled to the support points 920 to tailor the natural frequency of the restriction element 910, and thus improve the local reduction of pipe vibrations. In Figure 9 only one tuned mass is shown, which can be placed at each support pin 920 around the entire perimeter of the support frame 914.

[0148] Figure 10 a) schematically depicts a circumferential vibration mode of the pipe, where the mode is indicated by the number n and the number of nodes is indicated by the following formula: n = (number of nodes) / 2.

[0149] Figure 10 b) schematically depicts an axial vibration mode of the pipe, where the mode is indicated by the number m and the number of nodes is indicated by the following formula: m = (number of nodes) - 1.

[0150] The modes depicted by Figure 10 a) and b) can be generated within a segment of the pipe fluid system, defined by a restriction element mechanically coupled to the pipe.

Claims

1. A measurement system (400) for determining a physical parameter of a piping fluid system (110), comprising: a pair of limiting elements (112, 114) configured to reduce surface vibration deformation at an outer surface of each end of the piping fluid system (110); wherein each limiting element (112, 114) comprises a support frame (250) configured to be detachably mounted on a pipe (116) of the piping fluid system (110); and a fixation element (232) configured to be detachably mounted for mechanically coupling the support frame (250) with an outer surface of the pipe (116); an excitation system (412) configured to generate a mechanical vibration spectrum at a surface of the piping fluid system (110); and an acceleration acquisition system (430) configured to be mechanically coupled to an outer surface of the piping fluid system (110) and configured to provide a mechanical vibration spectrum of the piping fluid system (110); wherein the limiting elements (112, 114) are configured to create defined nodes of pipe vibration at locations around a perimeter of the pipe where the limiting elements locally suppress radial and bending vibration modes, wherein a mechanical vibration spectrum of vibration modes of a pipe section between the limiting elements can be used to determine the physical parameter.

2. The measurement system (400) according to claim 1, comprising a temperature sensor (440) configured to determine a temperature of the outer surface of the piping fluid system (110).

3. The measurement system (400) according to claim 2, comprising determining electronics (420) configured to determine a physical parameter of the piping fluid system (110) based on the provided mechanical vibration spectrum, wherein the determining electronics (420) are connected by electrical signals to the acceleration acquisition system (430) and / or to the temperature sensor (440).

4. The measurement system (400) according to any one of claims 1-3, comprising an input / output interface to input characteristic data of the pipe (116) of the piping fluid system (110) and / or process fluid data of the piping fluid system (110), and / or to output a physical parameter of the piping fluid system (110).

5. The measurement system (400) of claim 3, comprising: a support structure (410) configured to carry the excitation system (412) and to enable the excitation system (412) to generate a mechanical excitation; and / or a protective enclosure (450) enclosing the pair of limiting elements (112, 114); and the acceleration acquisition system (430); and the excitation system (412).

6. The measuring system (400) according to any one of claims 1-3, wherein the support frame (250) is configured to be detachably mounted on the pipe (116) by means of several frame elements (512, 514), wherein the frame elements (512, 514) are configured to mechanically engage to build the support frame (250); and the support frame (250) is configured to comprise an outer surface of the pipe (116).

7. The measuring system (400) according to any one of claims 1-3, wherein the fixation element (232) comprises a contact ring and / or a pair of contact rings and / or a pair of cutting edge rings.

8. The measuring system (400) according to claim 7, wherein an axial thickness of the contact ring and / or a distance between the pair of contact rings and / or a distance between the pair of cutting edge rings corresponds at least to a wall thickness of the pipe (116) of the pipe fluid system (110).

9. The measuring system (400) according to claim 7, wherein an axial thickness of the contact ring and / or a distance between the pair of contact rings and / or a distance between the pair of cutting edge rings corresponds at least to a thickness of twice a wall thickness of the pipe (116) of the pipe fluid system (110).

10. The measuring system (400) according to any one of claims 1-3, wherein the fixation element (232) comprises a plurality of discrete support pins (620, 720, 820, 920) arranged between the support frame (250) and the outer surface of the pipe (116) to mechanically couple the support frame (250) to the outer surface of the pipe (116) for reducing the surface vibration deformation (116) of the pipe fluid system (110).

11. The measuring system (400) according to any one of claims 1-3, wherein the fixation element (232) is mechanically coupled to the support frame (250) using a thermal compensation element for compensating the mechanical coupling with respect to thermal expansion of the pipe (116), and / or wherein the fixation element (232) is mechanically coupled to at least one tuned mass (930).

12. The measuring system (400) according to any one of claims 1-3, wherein the limiting element (112, 114) comprises a sensor for determining an intensity of the mechanical coupling between the support frame (250) and the outer surface of the pipe (116) via the fixation element (232).

13. The measuring system (400) according to any one of claims 1-3, wherein the limiting element (112, 114) comprises a mobile element for adjusting an intensity of the mechanical coupling between the support frame (250) and the outer surface of the pipe (116).

14. A kit of parts comprising features of the measuring system (400) according to any one of claims 1 to 13.

15. Use of a measuring system according to any one of claims 1 to 13 for determining a physical parameter of a pipe fluid system (110).

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