JP2013024573A - Impulse line blockage diagnosis availability determination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically determine whether a level of blockage specified can be detected.SOLUTION: An impulse line blockage diagnosis availability determination system comprises: a blockage specification part 10; a blockage characteristic computing part 11; a deformation characteristic computing part 12; a pressure propagation model computing part 13; and an evaluation determination part 14. A desired blockage level as a determination target is specified from the blockage level specification part 10. The blockage characteristic computing part 11 obtains flow characteristics of the blockage from the specified blockage level. The deformation characteristic computing part 12 obtains a deformation ratio for a pressure variation of an element constituting a pipe line system. The pressure propagation model computing part 13 obtains a pressure propagation model by using the obtained flow characteristics and deformation characteristics of the blockage. The evaluation determination part 14 evaluates pressure propagation characteristics of the obtained pressure propagation model and determines whether the specified blockage level can be detected by an applied impulse line blockage diagnosis method through comparison with a reference value.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure guiding tube clogging diagnosis availability determination system for determining whether clogging generated in a pressure guiding tube branched from a process pipe can be diagnosed.

  Conventionally, in the process industry field, for example, a pressure transmitter or a differential pressure transmitter is used to detect a process variable and control the process. The pressure transmitter is also called a pressure transmitter, and the differential pressure transmitter is also called a differential pressure transmitter. The pressure transmitter measures absolute pressure and gauge pressure, and the differential pressure transmitter measures the differential pressure between two points, and is used to measure process variables such as pressure, flow rate, liquid level, and specific gravity. In general, when measuring a process variable using a pressure / differential pressure transmitter (hereinafter simply referred to as a transmitter), the process pipe through which the fluid to be measured flows passes through a narrow pipe called a pressure guiding pipe. Introduce measurement object to transmitter.

  FIG. 10 shows a schematic diagram of a system (pressure measurement system) using a pressure transmitter. In this pressure measurement system, the pressure transmitter 1 detects the pressure of the fluid guided through the pressure guiding pipe 3 branched from the process pipe 2.

  FIG. 11 shows a schematic diagram of a system (differential pressure measurement system) using a differential pressure transmitter. In this differential pressure measuring system, the differential pressure transmitter 4 detects the pressure difference of the fluid guided through the pressure guiding pipes 3-1 and 3-2 branched from the process pipe 2. In this system, the process pipe 2 is provided with a differential pressure generating mechanism (orifice or the like) 5, and the pressure guiding pipes 3-1 and 3-2 are branched from positions before and after sandwiching the differential pressure generating mechanism 5. ing.

  In the system configuration of such a pressure measurement system or differential pressure measurement system, depending on the object to be measured, solid matter or the like may adhere to the inside of the pressure guiding tube, and the pressure guiding tube may be clogged. If the impulse tube is completely clogged, the process variables cannot be measured accurately, so the impact on the plant is enormous. However, since pressure is transmitted to the transmitter until the pressure guiding tube is completely clogged, the clogging effect is unlikely to appear in the process variable measurement.

  In order to solve such a problem, a remote seal type pressure transmitter which does not require a pressure guiding tube has been put into practical use. However, there are very many plants that measure process variables using a pressure guiding tube, and it is required to implement a pressure guiding tube clogging diagnosis function online.

  In order to solve this problem, a method and an apparatus for diagnosing clogging of a pressure guiding tube using a pressure fluctuation of a fluid have already been proposed.

  For example, Patent Document 1 shows that clogging of a pressure guiding tube can be detected from a decrease in the maximum fluctuation range (difference between the maximum value and the minimum value) of the pressure signal.

  Patent Documents 2 and 3 disclose apparatuses and methods for detecting and diagnosing clogging of a pressure guiding tube using the magnitude of fluctuations in pressure and differential pressure, and parameters calculated therefrom.

  Patent Document 4 discloses a device / method for diagnosing the state of a pressure guiding tube from a statistic or a function reflecting the magnitude of fluctuation, such as a standard deviation of fluctuation extracted from a differential pressure and a power spectral density. .

  Patent Document 5 discloses an apparatus / method for diagnosing clogging based on the speed of rocking, such as the number of vertical movements of pressure rocking. The invention described in Patent Document 5 is described in other Patent Documents 1 to 4 in that it is based on the speed (frequency) of rocking rather than the amplitude of rocking of pressure or differential pressure. This is different from the invention described above, but is common in that the fluctuation of pressure or differential pressure is used.

Japanese Patent Publication No.7-111473 Japanese Patent No. 3139597 Japanese Patent No. 3129121 Special table 2002-538420 gazette JP 2010-127893 A Japanese Patent No. 3147275 JP 2007-47012 A

Mini Special Feature "Recent Progress in Control of Distributed Parameter Systems", Measurement and Control, Vol. 19, No. 11 (1980) Eisuke Shoda: Control engineering (Engineering basic course (11)), Baifukan (1982) Shuichi Adachi: Basics of System Identification, Tokyo Denki University Press (2009)

  However, it is not always clear how much clogging can be detected by the conventional method of detecting clogging of the pressure guiding tube. Of course, it is possible to know the degree of clogging that can be detected by preparing an actually clogged pressure guiding tube or a simulated clogging and conducting an actual flow experiment (an experiment performed by actually flowing a fluid). However, it is not always the case that an experiment can be performed in advance under the same conditions as the actual diagnosis plant. If the degree of clogging that can be detected can be estimated without experimentation, it is thought that useful knowledge can be obtained even if the estimated value is rough, but such a method has not been provided yet.

  The degree of clogging that can be detected is expected to be affected by the type of fluid and its physical properties (eg, density, viscosity, bulk modulus). If so, just because a clog can be detected under certain conditions of one fluid does not mean that the same clog can be detected under different conditions of another fluid.

  For this reason, even though clogging can be detected by the conventional technique, it is usually difficult to know the degree unless a real flow experiment is performed under the same conditions.

  The present invention has been made to solve such a problem, and the object of the present invention is to clog a pressure guiding tube that can automatically determine whether or not a specified degree of clogging can be detected. The object is to provide a diagnosis availability determination system.

  In order to achieve such an object, the present invention is a system for determining whether or not a clogging diagnosis of a pressure guiding tube for determining whether or not a clogging generated in a pressure guiding tube branched from a process pipe is possible is possible. Based on the degree of clogging specified as a judgment target, and a deformation characteristic calculation means for calculating a deformation characteristic with respect to a pressure change of an element constituting the pipe system using a communicating pipe and a fluid flowing through these pipes. Pressure for calculating the pressure propagation model of the pipeline system from the clogging characteristic calculating means for calculating the flow characteristic of the clogging, the deformation characteristics calculated by the deformation characteristic calculating means and the flow characteristics of the clogging calculated by the clogging characteristic calculating means Propagation model calculating means, and evaluation judging means for evaluating and determining the pressure propagation model calculated by the pressure propagation model calculating means To.

  According to the present invention, the deformation characteristics with respect to the pressure change of the elements constituting the pipe system (for example, the pressure receiving surface (diaphragm) of the transmitter, the fluid filling the inside of the pressure guiding pipe, the pipe wall of the pressure guiding pipe) are calculated. The flow characteristic of the clogging is calculated from the degree of clogging specified as the judgment target, and the pressure propagation model of the pipeline system is calculated from the calculated deformation characteristic and the flow characteristic of the clogging. The calculated pressure propagation model Is evaluated. In the present invention, the calculated evaluation determination result of the pressure propagation model is used as a determination result of whether or not the designated degree of clogging can be detected.

  According to the present invention, the deformation characteristic with respect to the pressure change of the elements constituting the pipeline system is calculated, and the flow characteristic of the clogging is calculated from the degree of clogging specified as the determination target. Since the pressure propagation model of the pipeline system is calculated from the flow characteristics of the pipe, and the calculated pressure propagation model is evaluated and judged, it is automatically judged whether or not the specified degree of clogging can be detected. It becomes possible to do.

It is a figure which shows the pressure measurement system at the time of normal. It is a figure which shows a pressure measurement system when a pressure guiding tube is clogged. It is a figure explaining the factor (The flow rate characteristic of clogging, the deformation rate of the element which comprises the pipe line system between clogging-transmitters) which influences the pressure propagation characteristic in a pressure guiding pipe. It is a figure which shows the state which put the assumption that each pressure is equal on both sides of the clogging in a pressure guiding tube. It is a figure explaining a mode that the differential equation model (pressure propagation model) regarding pressure propagation is obtained from the element which affects the pressure propagation characteristic in a pressure guiding pipe. It is a figure which shows the example of the element which comprises the pipe line system between transmitters from clogging. 1 is a configuration diagram of a clogging diagnosis availability determination system according to Embodiment 1. FIG. 6 is a configuration diagram of a clogging diagnosis availability determination system according to Embodiment 2. FIG. FIG. 10 is a configuration diagram of a clogging diagnosis availability determination system according to a third embodiment. It is the schematic of the system (pressure measurement system) using a pressure transmitter. It is the schematic of the system (differential pressure measurement system) using a differential pressure transmitter.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, before the description of the embodiments, the background to the idea of the present invention and the principle of the present invention will be described.

[Background]
Various diagnostic methods have been proposed as methods for diagnosing clogging of a pressure guiding tube that detects clogging of the pressure guiding tube using fluctuations in pressure and differential pressure, but although the detection principle is different, the physical phenomenon used is The same. That is a phenomenon in which clogging (blockage) in the pressure guiding tube acts as a low-pass filter for pressure propagation in the conduit.

  Hereinafter, the pressure measurement system shown in FIG. 10 will be described as an example. In the differential pressure measurement system shown in FIG. 11, there is no essential difference with respect to the present invention except that there are two pressure guiding tubes. Therefore, the pressure shown in FIG. 10 uses a pressure transmitter as a transmitter. A measurement system will be described as a representative example.

  FIG. 1 shows a normal pressure measurement system. In this case, since the pressure guiding tube 3 is not clogged, the fluctuation (up and down movement) of the pressure of the fluid (process fluid) in the process pipe 2 is transmitted to the pressure transmitter 1 almost as it is, and the pressure transmission is performed. Pressure fluctuations in the vessel 1 occur.

  However, as shown in FIG. 2, when clogging (clogging) 6 occurs in the pressure guiding tube 3, the clogging (clogging) 6 functions as a low-pass filter for pressure propagation, and the pressure fluctuation detected by the pressure transmitter 1 is It becomes attenuated as compared with the case where there is no clogging (blocking) 6. In particular, the higher the frequency, the larger the attenuation width. Clogging of the pressure guiding tube 3 is detected by capturing this from changes in the amplitude and frequency of oscillation.

  As a result of studying the pressure propagation characteristics in the pressure guiding tube 3, the inventors have found that the main factors affecting the characteristics are the flow characteristics of the clogging (blocking) 6 (ease of fluid flow), clogging (blocking) 6 The fluid 7 (see FIG. 3) in the pressure guiding tube 3 between the pressure transmitter 1 and the pressure receiving surface of the pressure transmitter 1 in contact with the fluid 7 (the end of the communication pipe 8 inside the pressure transmitter 1) It is considered that there are two deformation ratios of the elements constituting the pipeline system such as the diaphragm 9 and the pipe wall 3a of the pressure guiding tube 3 with respect to the pressure change. And the pressure propagation characteristic model was constructed | assembled from the characteristic of these two elements, and the method of determining the propriety of the clogging of a pressure guiding pipe using the model was devised. In the following, the principle of the method will be described and then the details will be described.

[Principle of the Invention]
Strictly speaking, the pressure propagation characteristic model in the pressure guiding tube 3 should be modeled as a distributed constant system. However, since the distributed constant system is difficult to handle, the following explanation is based on a simplified lumped constant system model on the assumption that the pressures are equal on both sides of the clogging (blocking) 6 (see FIG. 4). In many cases, there is no problem even if it is performed based on a lumped parameter system model. Since the details of the distributed constant system and the lumped constant system are described in Non-Patent Document 1, description thereof is omitted here.

  This lumped parameter system model is composed of the above-mentioned two main elements (flow rate characteristics of clogging, deformation rate of elements constituting the pipeline system). Hereinafter, each will be described with reference to FIG.

The flow rate characteristic of the clogging (clogging) 6 is determined by the pressure difference (differential pressure) at both ends of the clogging (clogging) 6 and the degree of clogging. The pressure on the process piping side when viewed from the clogging (clogging) 6 is P ₁ (t), the pressure on the side where the pressure transmitter 1 is located (hereinafter referred to as the detection end side) is P ₂ (t), and clogging (clogging) If the flow rate flowing through 6 is represented by Q (t) (the direction of flow from the process piping side to the detection end side is positive), the flow rate characteristic of the clogging (blocking) 6 has the following relationship. The function f in the equation is a function determined by the degree of clogging. T represents time.

  Next, the fluid 7 in the pressure guiding tube 3 between the clogging (blocking) 6 and the pressure transmitter 1, and the pressure receiving surface 9 of the pressure transmitter 1 in contact with the fluid 7 and the tube wall 3 a of the pressure guiding tube 3. Described below is the deformation rate of the elements (see FIG. 6) constituting the pipeline system such as the pressure change. The amount of deformation of these elements increases and decreases in proportion to the pressure change (time differentiation). Then, the fluid 7 flows in and out through the clogging (clogging) 6 by an increase / decrease of the deformation amount (provided that there is no leakage). From the above, the flow rate Q (t) flowing through the clogging (blocking) 6 is expressed by the following equation.

  Note that C, which is a proportionality constant in this equation, is a constant representing the ease of deformation of the elements (see FIG. 6) constituting the pipeline system with respect to pressure changes. Hereinafter, this constant C is referred to as a deformation rate. When expressed as a mathematical expression, it is expressed as the following expression.

  Here, V is the volume of the fluid 7 in the pressure guiding tube 3 between the clogging (blocking) 6 and the pressure transmitter 1. The larger C is, the larger the sum of the deformation amount of each element due to the pressure change, that is, the easier it is to deform.

  Here, if Q (t) is eliminated from the equations (1) and (2), a differential equation model (pressure propagation model) relating to pressure propagation is obtained.

  If such a mathematical model is obtained, the pressure propagation characteristic from the process pipe 2 to the pressure transmitter 1, that is, the attenuation of the pressure fluctuation is estimated by analyzing the model or performing simulation using the model. It becomes possible. In the present invention, this is utilized to determine whether or not the pressure guiding tube clogging diagnosis is possible.

  In addition, although this invention assumes using the method of diagnosing clogging of a pressure guiding tube mainly using the pressure fluctuation of a fluid, it is not restricted only to it. That is, the present invention is effective even with other clogging diagnosis methods as long as the phenomenon that clogging (clogging) in the pressure guiding tube acts as a low-pass filter for pressure propagation in the pipe is used.

  For example, in Patent Documents 6 and 7, a stepped waveform is superimposed on an operation signal of a control valve (control valve) of a process pipe to which a transmitter is connected, and a pressure guiding tube is obtained from a response of pressure or differential pressure to the signal. A technique for diagnosing clogging is disclosed.

  These technologies utilize the fact that the pressure response waveform changes because clogging in the impulse line acts as a low-pass filter when changes in pressure and differential pressure caused by the operation of the control valve propagate to the transmitter. doing. Even in such a method, if the principle of the present invention is used, it is possible to estimate a response change due to clogging, and therefore it is possible to determine whether or not a pressure guiding tube clogging diagnosis is possible.

  Hereinafter, specific embodiments will be described by taking a pressure measurement system as an example, as in the principle of the invention described above.

[Embodiment 1]
FIG. 7 shows a configuration diagram of the clogging diagnosis availability determination system according to the first embodiment. The system according to the first embodiment includes a clogging degree designating unit 10, a clogging characteristic calculation unit 11, a deformation characteristic calculation unit 12, a pressure propagation model calculation unit 13, and an evaluation determination unit 14 (14A). Yes. 14 A of evaluation determination parts have the pressure propagation characteristic evaluation part 141, the memory | storage part 142 which memorize | stores a reference value, and the determination part 143.

  In this system, the clogging degree designating unit 10 designates a desired clogging degree as a determination target. The clogging characteristic calculation unit 11 obtains the flow characteristic of the clogging (differential pressure at both ends of the clogging—the characteristic of the flow rate flowing through the clogging) from the specified degree of clogging and sends it to the pressure propagation model calculation unit 13. In this case, as a method for obtaining the flow rate characteristic of clogging, there are a method using a theoretical formula, a method using a measured value, and the like.

[Method using theoretical formula]
The method using a theoretical formula obtains the differential pressure-flow rate characteristic of clogging from various laws known in fluid dynamics. For example, if the flow in the clog is a laminar flow and the clogged portion has a cylindrical shape, the following relational expression can be obtained from the Hagen-Poiseuille equation.

  Where μ is the viscosity of the fluid, l is the clogging length, d is the clogging diameter, and π is the circumference. Using this equation, when the clogging length and clogging diameter are given, a relational expression between the pressure difference across the clogging and the flow rate through the clogging can be obtained.

[Method using measured values]
In the method using the actually measured value, a closed flow path that simulates clogging is prepared, and the relationship of the equation (1) is obtained by measuring the differential pressure-flow rate characteristic. In addition, if the degree of clogging (diameter and length) is prepared and measured, and the result is interpolated (interpolated), the characteristics under various conditions other than the measured conditions are estimated and used. Is also possible.

In addition, a method based on system identification is also conceivable. In this method, the pressure at both ends of clogging (ie, P ₁ and P ₂ ) is measured at the same time, the pressure transmission characteristic from P ₁ to P ₂ is obtained by the system identification method, and the flow path characteristic of clogging is obtained from the result. It is. However, as shown by the equation (1), this characteristic depends on the deformation rate C of the elements constituting the pipeline system, in addition to the clogging channel characteristic. Therefore, this method is possible only when there is a measuring device with known C. Since the details of the system identification method are described in Non-Patent Document 3, detailed procedures are omitted here.

  The deformation characteristic calculation unit 12 calculates a deformation rate with respect to a pressure change of the entire pipeline system or an element that is particularly easily deformed in the pipeline system, and supplies the calculated deformation rate to the pressure propagation model calculation unit 13 as a deformation characteristic. send. The main elements are the fluid itself and the pressure-receiving surface (diaphragm) of the pressure transmitter. In the following, first, a general method for obtaining the deformation rate of these two elements will be described, and then other elements and other methods will be described.

  The deformation rate of the fluid itself can be calculated from the following equation if the bulk modulus of the fluid is known.

  Here, K is the bulk modulus of the fluid, and V is the volume of the fluid that fills between the clogging and the pressure transmitter.

  Note that V varies depending on the clogging position. For example, if it is easy to clog a specific location, if the volume of the pipe line between the location and the pressure transmitter is V, it can be determined whether or not it can be detected when the location is clogged.

  In general, the smaller the deformation rate C, that is, the smaller the V is, the more difficult it is to detect clogging. Therefore, if V is calculated assuming the location closest to the pressure transmitter among the possible locations of clogging. The case where clogging detection would be most difficult can be evaluated.

In addition, there is a method for obtaining the deformation rate of the fluid by obtaining the right side (dV / dP ₂ ) of the equation (3) from the gas equation of state.

  As for the deformation rate of the pressure receiving surface (diaphragm) of the pressure transmitter, if it can be obtained from the design specification of the pressure receiving surface, it is most certain to use the numerical value.

  Depending on the fluid, only one of the two may be considered. For example, in the case of a compressible fluid, the deformation rate of the fluid is often much higher than that of the pressure-receiving surface, and in most cases it is sufficient to consider only that of the fluid. On the other hand, in the case of an incompressible fluid, since the fluid hardly deforms, in most cases, it is sufficient to consider only the deformation rate of the pressure receiving surface.

  In addition, the pressure guiding tube also deforms with pressure. However, in the case of the most commonly used metal pressure guiding tube, the deformation rate is usually small compared to the two elements described above. Therefore, it can usually be ignored. However, it may be necessary to consider when the pressure guiding tube is a soft resin.

  Moreover, the method by system identification is also possible like the flow path characteristic of clogging. This method is effective when the value of C cannot be obtained by the method described so far. When this method is used, a simulated blockage having a known differential pressure-flow rate characteristic is required. Also, it should be noted that what is directly obtained by this method is not the individual deformation rate of each element constituting the pipeline system, but the sum thereof. When it is necessary to obtain individual deformation ratios, it is recommended to perform a plurality of experiments by changing the volume V of the fluid that fills between the simulated blockage and the pressure transmitter (the pressure receiving surface of the pressure transmitter is deformed to V). Although it does not depend, the amount of deformation of the fluid is proportional to V).

  The pressure propagation model calculation unit 13 uses the clogging flow characteristic obtained by the clogging characteristic calculation unit 11 and the deformation characteristic obtained by the deformation characteristic calculation unit 12 to generate a pressure transmitter from the connection point between the process pipe and the pressure guiding pipe. The pressure propagation model up to is obtained by calculation. There are various types of models. If the differential equation model expressed by the equation (4) is used, nonlinear dynamic characteristics can be expressed. On the other hand, in the case where the flow rate characteristic of clogging is expressed in the form as shown in Equation (5), the pressure propagation model can be expressed by a linear time-invariant dynamic model. For example, it can be expressed by a differential equation such as equation (7) or a transfer function such as equation (8). Since the transfer function expression is described in detail in Non-Patent Document 2, description thereof is omitted here.

Here, s represents a Laplace operator, and P ₁ (s) and P ₂ (s) represent Laplace transforms of P ₁ (t) and P ₂ (t). R is a coefficient that determines the flow characteristics of the clogging. For example, if the flow in the clogging is a laminar flow and the clogged portion has a cylindrical shape, the theoretical formula is a constant defined by equation (9): Become. Equation (8) means that the transfer characteristic from the connection point between the process pipe and the pressure guiding pipe to the pressure transmitter is characterized by a first-order low-pass filter whose time constant is RC.

  In addition, as a form of the pressure propagation model, a step response, a frequency response, etc. can be used. A distributed constant system model may be used.

  In the evaluation determination unit 14 </ b> A, the pressure propagation characteristic evaluation unit 141 evaluates the pressure propagation characteristic of the pressure propagation model calculated by the pressure propagation model calculation unit 13. Based on the evaluation result of the pressure propagation characteristic evaluated by the pressure propagation characteristic evaluation unit 141, the determination unit 143 stores whether or not the degree of clogging specified by the applied pressure guiding tube clogging diagnosis method can be detected. The comparison is made with the reference value stored in 142. Note that the determination result may vary depending on the pressure guiding tube clogging diagnosis method to be applied and the pressure transmitter used therefor. This is because the performance of clogging detection depends on the diagnostic method and the specifications / performance of the pressure transmitter.

[Embodiment 2]
FIG. 8 shows a configuration diagram of the clogging diagnosis availability determination system according to the second embodiment. The feature of the system of the second embodiment is that it is determined whether or not diagnosis is possible by simulating a pressure waveform when clogged by a simulation using a pressure propagation model.

  In this system, the evaluation determination unit 14 (14B) includes an evaluation unit 144, a storage unit 145 that stores a reference value, and a determination unit 146. The evaluation unit 144 includes a pressure waveform generation unit 144A, a clogging waveform simulation unit 144B, and a clogging index evaluation unit 144C. Each will be described below. Since the process of obtaining the pressure propagation model is the same as that in the first embodiment, the description thereof is omitted.

  The pressure waveform generation unit 144A generates a signal similar to the process piping pressure waveform at the time of diagnosis. Although it is a pressure waveform here, for example, if it is a diagnostic technique by pressure fluctuation like patent documents 1-5, a pressure waveform will be a pressure fluctuation waveform. Moreover, if it is the method of superimposing a step-shaped pressure change like patent document 6, 7, a pressure waveform will become a step-shaped waveform.

  There are several ways to generate a pressure waveform. For example, if the pressure waveform is a pressure fluctuation waveform, collect the pressure fluctuation waveform using the pressure transmitter that is the same as the diagnosis target without clogging the pressure guiding tube to be diagnosed. There is a method to use. Since this method uses the pressure fluctuation waveform that is actually the object of diagnosis as it is, the accuracy of the determination is increased. There is also a method in which the power spectrum density is estimated from the collected pressure fluctuation signal, and a signal having the same power spectrum is generated and used in a pseudo manner. Such a signal can be generated by a combination of a sequence of normal random numbers (random numbers following a normal distribution) and a filter. This method is effective when a sufficiently long pressure fluctuation waveform cannot be directly collected.

  When the pressure fluctuation waveform cannot be collected directly from the pressure guiding tube to be diagnosed, the method described above is used based on data collected at other pressure measurement points and other processes with similar operating conditions and fluid characteristics. It is possible to use a method of generating a swing waveform in a pseudo manner. In addition, if the nature of the pressure fluctuation of the fluid in relation to the power spectral density is theoretically known to some extent, it can be generated by using it.

  The same applies to the case where the pressure waveform used for diagnosis is a stepped waveform. It is conceivable to collect the pressure response waveform when the stepped operation signal is superimposed on the control valve without clogging the pressure guiding tube and use it as it is, or to use the stepped waveform as it is as a simulated pressure signal. .

  The clogging waveform simulation unit 144B uses the signal generated by the pressure waveform generation unit 144A and the pressure propagation model calculated by the pressure propagation model calculation unit 13 to be observed by the pressure transmitter when the pressure guiding tube is clogged. A simulated pressure waveform signal will be generated by simulation. As a generation method, numerical simulation by a computer is the most common, but other methods are also possible. For example, if an electric circuit equivalent to a pressure propagation model is prepared and a signal generated by the pressure waveform generation unit 144A is applied to the circuit as an electric signal, a simulated waveform at the time of clogging can be obtained as an electric signal as an output. .

  The clogging time index evaluation unit 144C applies the applied pressure guiding tube clogging diagnosis method to the simulated pressure waveform signal generated by the clogging time waveform simulation unit 144B and obtains an index that is a criterion for clogging. Evaluate the indicators for clogging. The determination unit 146 compares the index obtained by the clogging index evaluation unit 144C with the reference value stored in the storage unit 142, and determines whether or not the designated degree of clogging can be detected.

[Embodiment 3]
FIG. 9 shows a configuration diagram of a clogging diagnosis availability determination system according to the third embodiment. In the system of the third embodiment, the evaluation determination unit 14 (14C) includes a reference model storage unit 147 and a pressure propagation characteristic comparison determination unit 148. Since the process of obtaining the pressure propagation model is the same as that in the first embodiment, the description thereof is omitted.

  The reference model storage unit 147 stores, as a reference model, a pressure propagation model corresponding to a situation that can be detected by the applied pressure guiding tube blockage diagnosis method. For example, it can be detected if the time constant of the step response from the process pipe to the pressure transmitter is 1 [s] or more, or can be detected if the amplitude is 1/10 or less at 5 [Hz], The characteristics given in such a form are retained in a form that can be compared with the pressure propagation model (if necessary, converted). If possible, holding in the same format as that used by the pressure propagation model calculation unit 13 is preferable in terms of facilitating later comparison.

  The pressure propagation characteristic comparison / determination unit 148 compares the pressure propagation model calculated by the pressure propagation model calculation unit 13 with the reference model stored in the reference model storage unit 147, and the attenuation characteristic of the pressure propagation model is the reference model. It is determined that clogging can be detected.

  For example, it is assumed that both the pressure propagation model and the reference model are expressed in the transfer function format of equation (8). Here, if the reference model is a transfer function of equation (8) such that the time constant is 1 [s] or more, the time constant of the pressure propagation model to be compared is 1 [s] or more. It is determined that clogging can be detected and if it is less than 1 [s], it cannot be detected. Thus, the present embodiment is characterized in determining whether or not clogging can be detected through a model.

  In the first to third embodiments described above, the pressure measurement system using the pressure transmitter (FIG. 10) has been described, but the differential pressure measurement system using the differential pressure transmitter (FIG. 11) is the target. In the same manner, it is possible to determine whether or not a diagnosis for clogging in the pressure guiding tube is possible. In this case, the differential pressure measurement system has two pressure guiding tubes, but the pressure propagation model of the pressure guiding conduit may be used for each pressure guiding tube to determine whether or not diagnosis is possible.

  The pressure guiding tube clogging diagnosis availability determination system according to the present invention is a pressure measuring system using a pressure transmitter as a pressure guiding tube clogging diagnosis availability judgment system for determining whether or not diagnosis is possible for clogging occurring in a pressure guiding tube branched from a process pipe. And a differential pressure measurement system using a differential pressure transmitter.

  DESCRIPTION OF SYMBOLS 1 ... Pressure transmitter, 2 ... Process piping, 3, 3-1, 3-2 ... Impulse pipe, 3a ... Pipe wall, 4 ... Differential pressure transmitter, 5 ... Differential pressure generation mechanism (orifice etc.), 6 ... Clogging (Blocking), 7 ... fluid, 8 ... communication pipe, 9 ... pressure receiving surface (diaphragm inside pressure transmitter), 10 ... clogging degree designating part, 11 ... clogging characteristic calculating part, 12 ... deformation characteristic calculating part, 13 ... Pressure propagation model calculation unit, 14 (14A, 14B, 14C) ... evaluation determination unit, 141 ... pressure propagation characteristic evaluation unit, 142 ... storage unit, 143 ... determination unit, 144 ... evaluation unit, 144A ... pressure waveform generation unit, 144B ... clogging waveform simulation unit, 144C ... clogging index evaluation unit, 145 ... storage unit, 146 ... determination unit, 147 ... reference model storage unit, 148 ... pressure propagation characteristic comparison determination unit.

Claims (11)

A pressure guiding tube blockage diagnosis availability determination system for determining whether or not a diagnosis for clogging occurring in a pressure guiding tube branched from a process pipe is possible,
A deformation characteristic calculating means for calculating a deformation characteristic with respect to a pressure change of an element constituting the pipe system, wherein the pressure guiding pipe and a communication pipe communicating with the pressure guiding pipe and a fluid flowing through the pipe are used as a pipe line system;
Clogging characteristic calculating means for calculating the flow rate characteristic of the clogging from the degree of clogging specified as a judgment target;
Pressure propagation model computing means for computing a pressure propagation model of the pipeline system from the deformation characteristics computed by the deformation characteristics computing means and the clogging flow characteristics computed by the clogging characteristics computing means;
An evaluation determining unit that evaluates and determines the pressure propagation model calculated by the pressure propagation model calculating unit. In the pressure guiding tube blockage diagnosis availability determination system according to claim 1,
2. A pressure guiding tube blockage diagnosis availability determination system characterized in that a mathematical model approximated by a lumped parameter system is used as the pressure propagation model of the conduit system. In the pressure guiding tube blockage diagnosis availability determination system according to claim 2,
The following equation (1) is used as a mathematical model approximated by the lumped parameter system.

However, in the above equation (1), P1 (t) is the pressure on the process piping side when viewed from the clogging, P2 (t) is the pressure on the detection end side when viewed from the clogging, and f is a function that determines the flow rate characteristics of clogging. t is time, C is a deformation rate with respect to a pressure change of elements constituting the pipeline system. In the pressure guiding tube blockage diagnosis availability determination system according to claim 3,
As a mathematical model approximated by the lumped parameter system, the function f (P ₁ (t) −P ₂ (t)) in the equation (1) is expressed as a linear function of P ₁ (t) −P ₂ (t). A system for determining whether or not a pressure guiding tube is clogged is characterized by using the following equation (2) replaced by a certain (P ₁ (t) −P ₂ (t)) / R.

However, in the above equation (2), R is a coefficient that determines the flow characteristics of clogging. In the pressure guiding tube blockage diagnosis availability determination system according to claim 3,
A system for determining whether or not a pressure guiding tube is clogged is characterized by using a model expressed by a transfer function as a mathematical model approximated by the lumped parameter system. In the pressure guiding tube blockage diagnosis availability determination system according to claim 1,
The evaluation determination means includes
Pressure propagation characteristic evaluating means for evaluating pressure propagation characteristics of the pressure propagation model calculated by the pressure propagation model calculating means;
Determination means for comparing with a reference value whether or not the specified degree of clogging can be detected by a clogging diagnosis method applied based on the result evaluated by the pressure propagation characteristic evaluation means. A system for determining whether or not a pressure guiding tube is clogged. In the pressure guiding tube blockage diagnosis availability determination system according to claim 1,
The evaluation determination means includes
Pressure waveform generation means for generating a signal similar to the process pipe pressure waveform at the time of diagnosis;
Using the signal generated by the pressure waveform generating means and the pressure propagation model calculated by the pressure propagation model calculating means, a simulated pressure waveform signal that will be observed when the pressure guiding tube is clogged is generated by simulation. Clogging waveform simulation means,
A clogging time index evaluating means for applying an applied pressure guiding tube clogging diagnosis method to the simulated pressure waveform signal generated by the clogging time waveform simulating means to obtain an index serving as a judgment criterion for clogging;
A pressure guiding tube blockage diagnosis comprising: a determination unit that determines whether or not the specified degree of clogging can be detected by comparing an index obtained by the clogging index evaluation unit with a reference value. Acceptability determination system. In the pressure guiding tube blockage diagnosis availability determination system according to claim 1,
The evaluation determination means includes
Reference model storage means for storing, as a reference model, a pressure propagation model corresponding to a situation that can be detected by a clogging diagnosis method for a pressure guiding tube to be applied;
Whether the reference model stored in the reference model storage means and the pressure propagation model calculated by the pressure propagation model calculation means are compared, and whether or not the specified degree of clogging can be detected based on the comparison result And a determination means for determining whether or not a pressure guiding tube blockage diagnosis is possible. In the determination system for determining whether or not the pressure guiding tube is clogged according to any one of claims 1 to 8,
The clogging characteristic calculation means includes:
A Hagen-Poiseuille equation is used when calculating the flow rate characteristic of the clogging. In the determination system for determining whether or not the pressure guiding tube is clogged according to any one of claims 1 to 8,
Pressure detecting means for detecting the pressure of the fluid guided from the pressure guiding tube;
The deformation characteristic calculation means includes:
When the fluid is an incompressible fluid, the deformation characteristic of the pressure receiving surface of the pressure detecting means is calculated as the deformation characteristic. In the determination system for determining whether or not the pressure guiding tube is clogged according to any one of claims 1 to 8,
Pressure detecting means for detecting the pressure of the fluid guided from the pressure guiding tube;
The deformation characteristic calculation means includes:
When the fluid is a compressive fluid, the deformation characteristics include the volume elastic modulus of the fluid, and the volume of the fluid that satisfies a gap between the clogging designated as the determination target and the pressure detection means. A system for determining whether or not a pressure guiding tube is clogged is characterized by calculating a deformation characteristic of the pressure guiding tube.

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