JP2009053083A - Pressure sensing device and pressure sensing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensing device and a pressure sensing system capable of detecting clogging of a connecting pipe, at low cost and at a high sensitivity. <P>SOLUTION: A differential-pressure/pressure transmitter 2 as a pressure detector, is provided with connecting pipes 6a, 6b connected to mutually different positions of a pipe 4, wherein a fluid X flows, a sensor unit 11 for detecting a static pressure and the differential pressure between the pressure inside the connecting pipe 6a and the pressure inside the connecting pipe 6b, and a detection part 19 for detecting clogging of at least one of the connecting pipes 6a, 6b, based on the magnitude of the ratio between fluctuation of the differential pressure and that of the static pressure detected by the sensor unit 11. Specifically, the detection part 19 finds the dispersion or the average value of the ratios between fluctuations in the differential pressure and fluctuations of the static pressure, and by comparing these values with predetermined thresholds, or the like, diagnoses the existence of the clogging of at least the one of the connecting pipes 6a, 6b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure detector and a pressure detection system.

  One type of pressure detector is provided with a throttle mechanism such as an orifice plate in the middle of a pipe through which fluid flows, and detects the pressure on the upstream side (high pressure side pressure) and the pressure on the downstream side (low pressure side pressure) of the throttle mechanism, There is a pressure detector for obtaining a differential pressure signal indicating the differential pressure and a static pressure signal indicating the static pressure. This type of pressure detector includes a pressure guiding pipe that is located upstream of the throttle mechanism and connected to the pipe, and a pressure guiding pipe that is located downstream and connected to the pipe, and the fluid that passes through the pressure guiding pipe By detecting this pressure, the high pressure side pressure and the low pressure side pressure are detected.

The differential pressure signal and the static pressure signal obtained by the pressure detector are transmitted to the host computer via an analog transmission line or a digital transmission line. For details of the conventional pressure detector, refer to, for example, the following Patent Documents 1 to 9.
JP 2006-329846 A JP 2006-105707 A JP 2005-274501 A JP 2006-329847 A JP 2004-354280 A JP 2004-294175 A JP 2004-132817 A US Pat. No. 6,654,697 US Pat. No. 6,907,383

  By the way, in the pressure detector described above, when a fluid having a high viscosity such as crude oil flows in the pipe, a fluid having a large amount of impurities / solids flows in the pipe, or the fluid flowing in the pipe is solidified by a low outside air temperature. If this is the case, the pressure guiding tube may be clogged. When the pressure guiding tube is clogged, the pressure detector does not detect the high pressure side pressure or the low pressure side pressure of the fluid flowing in the pipe, but detects the pressure inside the pressure guiding tube where the clogging has occurred. Thus, the differential pressure signal and the static pressure signal obtained in step 1 become meaningless values.

  Conventionally, detection of clogged pressure tubes has been largely dependent on the experience and intuition of skilled workers, such as capturing changes from normal operating conditions, but in recent years a method for automatically detecting clogged pressure tubes has been proposed. ing. For example, in Patent Document 8 described above, clogging of a pressure guiding tube is automatically performed based on a change in a calculation result of a spectral density of a process value such as a differential pressure value and a change in a calculation result of an autocorrelation coefficient with a previous detection result. A method of detecting is disclosed. Further, in the above-mentioned Patent Document 2, there is a method for automatically detecting clogging of a pressure guiding tube by calculating a dispersion ratio of a minute change amount of a differential pressure signal and a dispersion ratio of a minute change amount of a static pressure signal. It is disclosed.

  However, in the method disclosed in Patent Document 8, it is necessary to perform an operation such as FFT (Fast Fourier Transform), so that a high-speed and large-scale digital circuit and a memory for sampling are required. There is a problem that the cost of the pressure detector increases. In addition, the installation location of the pressure detector is often in a hazardous atmosphere, and a large-scale circuit is not suitable because it is restricted by energy. Furthermore, in recent years, low power consumption that can be driven by a battery has been demanded, and when using a circuit such as FFT, there is a problem that it is necessary to achieve both high-speed processing, low power consumption, and downsizing. .

  Further, the method disclosed in Patent Document 2 does not necessarily require a large-scale digital circuit as in Patent Document 8. However, in Patent Document 2, the dispersion ratio of the minute time change (time derivative) of the differential pressure signal measured by the two types of the short time counter and the long time counter and the minute time change (time derivative) of the static pressure signal. ), And the variance ratio of the second derivative of the differential pressure signal and the variance of the second derivative of the static pressure signal are calculated. This is also redundant.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure detector and a pressure detection system that can detect clogging of a pressure guiding tube at low cost with high sensitivity.

In order to solve the above problems, a pressure detector of the present invention includes first and second pressure guiding pipes (6a, 6b) connected to different positions of a pipe (4) through which a fluid (X) flows, and the first In a pressure detector (2) comprising a sensor (11) for detecting a differential pressure and a static pressure between a pressure in one pressure guiding tube and a pressure in the second pressure guiding tube, the pressure difference detected by the sensor A detection unit (19) for detecting clogging of at least one of the first and second pressure guiding pipes based on the ratio of the swing and the swing of the static pressure is provided.
According to the present invention, the differential pressure and static pressure in the first and second pressure guiding pipes connected to different positions of the pipe through which the fluid flows are detected by the sensor, and the fluctuation of the differential pressure detected by the sensor is detected. Based on the ratio of the ratio of the vibration to the static pressure, at least one of the first and second pressure guiding tubes is detected by the detection unit.
Further, in the pressure detector of the present invention, the detection unit calculates a calculation unit (19a) for obtaining at least one of an average value and a dispersion value of a ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure, A diagnostic unit (19b) is provided for diagnosing the presence or absence of clogging of at least one of the first and second pressure guiding pipes by comparing a value obtained by the calculation unit with a predetermined threshold value.
Further, in the pressure detector of the present invention, the detection unit calculates a calculation unit (19a) for obtaining at least one of an average value and a dispersion value of a ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure, At least one of the first and second pressure guiding pipes from a comparison between a current value obtained by the calculation unit and a value obtained in the past by the calculation unit, or a tendency of a change in the value obtained by the calculation unit. And a diagnosis unit (19b) for diagnosing the presence or absence of clogging.
In the pressure detector of the present invention, the diagnosis unit diagnoses the degree of clogging of at least one of the first and second pressure guiding pipes by comparing a value obtained by the calculation unit with a plurality of threshold values. A display unit (17) for displaying information indicating the degree of clogging diagnosed by the diagnostic unit is provided.
Furthermore, the pressure detector of the present invention includes a communication unit (18) for transmitting at least one of the detection result of the sensor and the calculation result of the calculation unit to a higher-level management device.
The pressure detection system of the present invention includes a pressure detector (2) installed in a pipe (4) through which a fluid (X) flows, and a management device (3) that manages the pressure detector (1). ), The pressure detector according to the present invention is provided as the pressure detector, and the management device detects the fluctuation of the differential pressure and the fluctuation from the detection result of the sensor transmitted from the pressure detector. It is characterized in that at least one of an average value and a dispersion value with respect to the fluctuation of the static pressure is obtained, and the presence or absence of clogging of at least one of the first and second pressure guiding pipes is diagnosed using the value.
Moreover, the pressure detection system of this invention is a pressure detection system provided with the pressure detector (2) installed in the piping (4) through which the fluid (X) flows, and the management apparatus (3) which manages the said pressure detector. In (1), the pressure detector according to the present invention is provided as the pressure detector, and the management device is configured to change the calculation result of the calculation unit transmitted from the pressure detector. It is characterized by diagnosing the presence or absence of clogging of at least one of the first and second pressure guiding tubes.

  According to the present invention, the differential pressure and static pressure in the first and second pressure guiding pipes connected to different positions of the pipe through which the fluid flows are detected by the sensor, and the detected differential pressure fluctuation and static pressure are detected. Since clogging of at least one of the first and second pressure guiding pipes is detected on the basis of the ratio of the pressure fluctuation, and a conventional large-scale digital circuit is not required, There is an effect that the clogging of the first and second pressure guiding pipes can be detected at low cost with high sensitivity.

  Hereinafter, a pressure detector and a pressure detection system according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of a pressure detection system according to an embodiment of the present invention. As shown in FIG. 1, the pressure detection system 1 of this embodiment includes a differential pressure transmitter 2 (pressure detector) and a host computer 3 (management device). The differential pressure transmitter 2 and the host computer 3 are connected to each other via a wired or wireless analog transmission line or digital transmission line (not shown).

  The differential pressure transmitter 2 is installed in a pipe 4 through which the fluid X flows. This differential pressure transmitter 2 includes a pressure guiding pipe 6a (first pressure guiding pipe) connected to a pipe 4 on the upstream side of an orifice 5 (throttle mechanism: see FIG. 2) installed in the pipe 4, and a downstream side. A pressure guiding pipe 6b (second pressure guiding pipe) connected to the pipe 4 is provided, and a differential pressure and a static pressure in the pressure guiding pipes 6a and 6b are detected. As shown in FIG. 1, the differential pressure transmitter 2 can detect the temperature and mass flow rate of the fluid X in addition to the static pressure and the differential pressure.

  FIG. 2 is a block diagram showing an internal configuration of the differential pressure transmitter 2. As shown in FIG. As shown in FIG. 2, the differential pressure transmitter 2 includes a sensor unit 11, a frequency counter 12, an oscillation circuit 13, a central processing unit (MPU: Micro Processing Unit) 14, a RAM (Random Access Memory) 15, an EEPROM (Electrically Erasable). A Programmable Read Only Memory (16), a display unit 17, a communication unit 18, and a ROM (Read Only Memory) 20 are provided. The sensor unit 11 includes a first sensor unit 11a including a resonator 21a, a transformer 22a, an amplifier 23a, and a drive circuit 24a of a silicon resonant sensor, and a vibrator 21b, a transformer 22b, an amplifier 23b, and a drive circuit 24b of a silicon resonant sensor. The 2nd sensor part 11b which consists of.

  3A and 3B are diagrams illustrating a configuration of a sensor chip on which a silicon resonant sensor is formed, in which FIG. 3A is a perspective view, and FIG. 3B is a cross-sectional view taken along line AA in FIG. FIG. As shown in FIG. 3, the sensor chip 30 has a substantially rectangular parallelepiped shape formed of silicon, and a recess 31 is formed at the center of the bottom surface 30 b of the sensor chip 30, so that the center of the sensor chip 30 on the surface 30 a side. Is the diaphragm 32. As shown in FIG. 3A, the vibrator 21 a is attached to the end of the diaphragm 32 on the surface 30 a of the sensor chip 30, and the vibrator 21 b is on the surface 30 a and the center part of the diaphragm 32. Is attached.

  On the surface 30a of the sensor chip 30, a pair of wires connected to the vibrator 21a extend in the vertical direction along the plane of the paper, and an excitation terminal 33 is provided at the end of one of the wires forming the pair. A detection terminal 34 is provided at the end of the other wiring. Similarly, on the surface 30a of the sensor chip 30, a pair of wirings connected to the vibrator 21b extend in the vertical direction along the paper surface, and an excitation terminal 35 is provided at the end of one of the paired wirings. The detection terminal 36 is provided at the end of the other wiring pair. The excitation terminal 33 is connected to the drive circuit 24a in FIG. 2, and the detection terminal 34 is connected to the transformer 22a in FIG. Similarly, the excitation terminal 35 is connected to the drive circuit 24b in FIG. 2, and the detection terminal 36 is connected to the transformer 22b in FIG.

  A magnetic field is applied to the silicon resonant sensor having the above configuration from above or below along the paper surface of FIG. 3A, and when a current is passed through the vibrators 21a and 21b, the vibrators 21a and 21b are predetermined. Vibrates at the natural frequency of. The transformer 22a, amplifier 23a, and drive circuit 24a provided in the first sensor unit 11a are circuits for vibrating the vibrator 21a at its natural frequency. The transformer 22b, amplifier provided in the second sensor unit 11b 23b and the drive circuit 24b are circuits for vibrating the vibrator 21b at its natural frequency.

  Further, the fluid through the pressure guiding tube 6a is guided to the front surface 30a side of the sensor chip 30 shown in FIG. 3, and the fluid through the pressure guiding tube 6b is guided to the back surface 30b side (inside the recess 31). For this reason, when the diaphragm 32 is distorted in accordance with the pressure difference in the pressure guiding pipes 6a and 6b, the vibrators 21a and 21b are stretched or compressed to change their own tension, and the inherent vibration of the vibrators 21a and 21b. The frequency changes as shown in the following equation (1).

但し、上記（１）式中の各変数は以下の通りである。
ｆ ：固有振動数
Ｅ ：シリコンのヤング率
ρ ：シリコンの密度
ｌ ：振動子の長さ
ｈ ：振動子の厚さ
ε ：張力
ε_０ ：初期張力
ε_ｄｐ：差圧による張力変化
ε_ｓｐ：静圧による張力変化
尚、ε＝ε_０＋ε_ｄｐ＋ε_ｓｐなる関係がある。

However, each variable in the above equation (1) is as follows.
f: the natural frequency E: Young's modulus of silicon [rho: density of the silicon l: length of the transducer h: thickness of the vibrator epsilon: Tension epsilon _0: initial tension epsilon _dp: tension change due to the differential pressure epsilon _sp: static Tension change due to pressure Note that there is a relationship of ε = ε ₀ + ε _dp + ε _sp .

  Here, as shown in FIG. 3, the vibrator 21 a is attached to the end of the diaphragm 32, and the vibrator 21 b is attached to the center of the diaphragm 32. For this reason, changes in the natural frequencies of the vibrators 21 a and 21 b are different depending on the amount of distortion of the diaphragm 32. In the present embodiment, the differential pressure and static pressure in the pressure guiding tubes 6a and 6b are detected by detecting changes in the natural frequencies of the vibrators 21a and 21b.

  When the natural frequency of the pressure guiding pipes 6a and 6b changes, the transformer 22a, the amplifier 23a, and the drive circuit 24a provided in the first sensor unit 11a drive the vibrator 21a with the changed natural frequency. The transformer 22b, the amplifier 23b, and the drive circuit 24b provided in the second sensor unit 11b drive the vibrator 21b at the natural frequency after the change. For this reason, the drive circuits 24a and 24b output signals (signals for driving the vibrators 21a and 21b) indicating the natural frequencies of the vibrators 21a and 21b to the frequency counter 12.

  The frequency counter 12 samples the signals output from the first sensor units 11a and 11b using the reference clock output from the oscillation circuit 13, and counts the number of pulses of each signal. Here, the sampling period of the frequency counter 12 is about several tens of msec. The oscillation circuit 13 supplies a reference clock having a predetermined frequency to the frequency counter 12 and the MPU 14. The MPU 14 operates in synchronization with the reference clock supplied from the oscillation circuit 13 and comprehensively controls the operation of the differential pressure transmitter 2. Further, the MPU 14 implements the detection unit 19 by software by reading and executing a program stored in the ROM 20. The ROM 20 may be built in the MPU 14 or provided outside.

The detection unit 19 includes a data collection calculation unit 19a (calculation unit) and a diagnosis unit 19b. The detection unit 19 obtains the natural frequency of the transducers 21a and 21b from the number of pulses counted by the frequency counter 12, and the above equation (1). The pressure differential pressure and the static pressure in the pressure guiding pipes 6a and 6b are obtained from the above, and clogging of at least one of the pressure guiding pipes 6a and 6b is detected based on the ratio of these minute time changes (hereinafter referred to as oscillation). To do. In the following description, the natural frequency of the vibrator 21a and _{f c,} the natural frequency of the vibrator 21b to _{f r}

Data acquisition calculating unit 19a is counted natural frequency of the pulse number f _c the frequency counter _12, the seek f _r, (1) impulse line 6a from the equation, the pressure within 6b differential pressure and static The pressure is obtained, and further, at least one of the average value and the dispersion value of the ratio of the fluctuation of the differential pressure between the pressure guide pipes 6a and 6b and the fluctuation of the static pressure is obtained. Specifically, the data acquisition calculating unit 19a is the natural frequency f _c, the f _r determined from the number of pulses output from the frequency counter 12, for each sampling period of the frequency counter 12, connecting pipe 6a, the pressure in 6b The differential pressure signal x (i) indicating the differential pressure and the static pressure signal y (i) indicating the static pressure are obtained using the following equations (2) and (3).

但し、上記（２），（３）式中におけるｉは正の値（整数）をとる変数である。また、ａ，ｂ，ｋ，ｌは正の定数であり、ｃ，ｍは定数である。尚、ｆ_ｃ（ｉ），ｆ_ｒ（ｉ）は、ｉ番目のサンプリング時に求められた振動子２１ａ，２１ｂの固有振動数を意味する。

However, i in the above formulas (2) and (3) is a variable that takes a positive value (integer). Further, a, b, k, and l are positive constants, and c and m are constants. Note that f _c (i) and f _r (i) mean the natural frequencies of the vibrators 21a and 21b obtained at the i-th sampling.

Further, the data collection calculation unit 19a obtains the fluctuation dx (i) of the differential pressure signal x (i) obtained using the above equation (2) using the following equation (4), and the above (3). The fluctuation dy (i) of the static pressure signal y (i) obtained using the equation is obtained using the following equation (5). In the present embodiment, the sampling period of the frequency counter 12 is about several tens of msec. Therefore, the fluctuation dx (i) of the differential pressure signal is a change in the differential pressure in a minute time of about several tens of msec, and the fluctuation dy (i) of the static pressure signal is a static pressure in a minute time of about several tens of msec. Is a change.

Here, the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal vary depending on the degree of clogging of the pressure guiding pipes 6a and 6b. Now, the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal are obtained by simulation, normalized by the following equation (6), and plotted on the xy plane, the result shown in FIG. 4 is obtained. It is done.

  FIG. 4 is a simulation result showing changes in the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal. The simulation results shown in FIG. 4 are for the case where the fluid flowing in the pipe 4 is water, and a valve whose opening degree can be freely set is attached to the pressure guiding pipe 6a to adjust the opening degree of the valve. It was obtained. 4A is a simulation result when the pressure guiding tube is not clogged, FIG. 4B is a simulation result when the pressure guiding tube is slightly clogged, and FIG. It is a simulation result when the pressure pipe is completely clogged.

  As shown in FIG. 4A, when there is no clogging, the plotted result of the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal may be almost circular. I understand. On the other hand, referring to FIG. 4 (b) and FIG. 4 (c), the plots at the upper and lower parts of the graph decrease as the degree of clogging becomes worse, but the plots at the left and right parts of the graph start to be dense. . That is, in FIG. 4, the phase difference based on the ratio of the fluctuation of the differential pressure between the pressure guide pipes 6a and 6b and the fluctuation of the static pressure changes according to the degree of clogging of the pressure guide pipes 6a and 6b. Represents that.

Table 1 below is a table showing the average value and the dispersion value of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure in each case of FIGS. 4 (a) to 4 (c).

  Referring to Table 1, it can be seen that the average value and the variance value vary greatly depending on the degree of clogging. Specifically, as the degree of clogging increases, the average value decreases and the variance value also decreases. As shown in FIG. 4, this is consistent with the fact that the plots are concentrated on the left and right sides of the graph as the degree of clogging increases. From the above, using at least one of the average value and the dispersion value of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure is advantageous in diagnosing the presence or absence of clogging of the pressure guiding tubes 6a and 6b.

The data collection calculation unit 19a collects the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal for N cycles (N is an integer of 2 or more) obtained in the past. The average value avg_p (k) of the ratio of the fluctuation of the differential pressure and the fluctuation of the static pressure at a certain time point k is obtained by using the following equation (7), or at a certain time point k using the following equation (8): The variance var_p (k) of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure is obtained.

  The data collection calculation unit 19a stores the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal obtained in the past in the RAM 15. Thereby, if the data collection calculation part 19a reads the past value from RAM15, said average value and dispersion | distribution can be calculated | required. The average value and the variance value are also stored in the RAM 15. The calculation of the average value and the variance may be performed every sampling cycle of the frequency counter 12, or may be performed every predetermined cycle.

  The diagnosis unit 19b diagnoses whether or not at least one of the pressure guiding tubes 6a and 6b is clogged by comparing the value (at least one of the average value and the variance value) obtained by the data collection calculation unit 19a with a predetermined threshold value. To do. Alternatively, the diagnosis unit 19b obtains the current value (at least one of the average value and the variance value) obtained by the data collection calculation unit 19a and the value obtained in the past (at least one of the average value and the variance value). The presence or absence of clogging of at least one of the pressure guiding pipes 6a and 6b is diagnosed based on a tendency of comparison or a change in a value (at least one of an average value and a dispersion value) obtained by the data collection calculation unit 19a.

For example, the diagnosis unit 19b calculates the value of the variance var_p (k) of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure obtained by the data collection calculation unit 19a using the above equation (8) as follows: By classifying according to Table 2, the presence or absence of clogging of the pressure guiding pipes 6a and 6b is diagnosed.

  That is, in the example of Table 2 above, two threshold values “1” and “0.01” are used, and if the value of dispersion var_p (k) is 1 or more, the pressure guiding tube is diagnosed as normal (no clogging), The alarm classification is “normal”. If the value of variance var_p (k) is larger than 0.01 and smaller than 1, it is diagnosed that the pressure guiding tube tends to be clogged, and the alarm classification is set to “warning”. Further, if the value of the variance var_p (k) is 0.01 or less, it is diagnosed that the pressure guiding tube is clogged, and the alarm classification is set to “alarm”. Thus, the type of alarm can be changed according to the degree of clogging.

  In this example, the case where diagnosis is made by comparing the value of the variance var_p (k) of the ratio of the fluctuation of the differential pressure and the fluctuation of the static pressure with a predetermined threshold is described. A similar diagnosis may be performed by comparing the average value avg_p (k) of the ratio of the dynamic and static pressure fluctuations with a predetermined threshold. Alternatively, in order to improve the accuracy of diagnosis, both the value of variance var_p (k) and the average value avg_p (k) may be compared with a predetermined threshold value.

  Further, the diagnosis unit 19b calculates the regression line shown in FIG. 5 from the average value avg_p (k) and the variance var_p (k) stored in the RAM 15, so that the pressure guiding tubes 6a and 6b are calculated from the tendency of these changes. Diagnose the presence or absence of clogging. FIG. 5 is a diagram illustrating an example of a regression line obtained by the diagnosis unit 19b. In the graph shown in FIG. 5, the horizontal axis represents time, and the vertical axis represents the variance var_p of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure.

  In FIG. 5, the symbol “x” with the reference symbol V1 indicates the value of the variance (the value of var_p (k1)) obtained at the time point k1, and the symbol “×” with the reference symbol V2 indicates the time point k2. The dispersion value (value of var_p (k2)) obtained at the time is shown. Similarly, the symbol “x” with the symbol V3 indicates the value of the variance (the value of var_p (k3)) obtained at the time point k3, and the symbol “x” with the symbol Vp indicates the value at the time point kp. The dispersion value (var_p (kp) value) obtained sometimes is shown. Note that the time points k1 to k3 are past time points, and the time point kp is the current time point (= t0). The intervals between these time points k1 to kp are arbitrary, and are set to arbitrary intervals equal to or longer than the sampling period.

In FIG. 5, a straight line with a symbol L <b> 1 is a regression line obtained from the values of the variances var_p (k <b> 1) to var_p (kp). The regression line L1 can be expressed as a function of time t using arbitrary variables a and b as shown in the following equation.
var_p (t) = a · t + b
Furthermore, numerical values “0.01” and “1” shown on the vertical axis of the graph in FIG. 5 are threshold values used by the diagnosis unit 19b to diagnose clogging, and are the same as the threshold values shown in Table 2. Is.

  When the diagnosis unit 19b obtains the regression line L1, the diagnosis unit 19b obtains the intersection C1 between the regression line L1 and the threshold “1”, and the expected arrival time T1 (the intersection C1 of the intersection C1) required until the variance value becomes the threshold “1”. The difference between the time t1 and the current time t0) is obtained. Similarly, the diagnosis unit 19b obtains the intersection C2 between the regression line L1 and the threshold “0.01”, and the expected arrival time T2 (the time t2 of the intersection C2) required until the variance reaches the threshold “0.01”. And the difference between the current time t0). Thereby, the tendency of the change of the dispersion value is obtained, and the presence or absence of clogging of the pressure guiding pipes 6a and 6b is predicted or diagnosed early.

  In this example, the case of diagnosing using the tendency of change in the value of variance var_p of the ratio of fluctuation of differential pressure to fluctuation of static pressure is taken as an example. A similar diagnosis may be performed using the tendency of change in the average value avg_p of the ratio to the oscillation. Alternatively, in order to improve the accuracy of diagnosis, diagnosis may be performed by determining the tendency of change for both the value of variance var_p (k) and the average value avg_p (k).

The RAM 15 is an average value of the differential pressure signal fluctuation dx (i) and the static pressure signal fluctuation dy (i) calculated by the data collection calculation unit 19a, and the ratio of the differential pressure fluctuation to the static pressure fluctuation. avg_p (k), variance var_p (k), and other various values are temporarily stored. The EEPROM 16 stores various variables and constants used for obtaining the natural frequencies f _c and f _r of the vibrators 21a and 21b necessary for program execution by the MPU 14, threshold values used for diagnosis by the diagnosis unit 19b, and other various information. Remember. The ROM 20 stores various programs executed by the MPU 14.

  The display unit 17 includes a display device such as an LCD (Liquid Crystal Display), and the detected differential pressure and static pressure in the pressure guiding pipes 6a and 6b and an alarm (depending on the degree of clogging). Alarm that changes alarm type) and other various information. The communication unit 18 communicates various information with the host computer 3 shown in FIG. Specifically, at least one of the detection result of the differential pressure and the static pressure of the pressure in the pressure guiding pipes 6a and 6b, the average value of the fluctuation of the differential pressure and the fluctuation of the static pressure, and the value of dispersion, or diagnosis Information indicating the diagnosis result of the unit 19b is transmitted to the host computer 3. The communication unit 18 can perform communication (wired communication, wireless communication, communication using an analog signal, communication using a digital signal) according to the connection form between the differential pressure transmitter 2 and the host computer 3. Is possible.

  The host computer 3 manages the differential pressure transmitter 2 based on information transmitted from the differential pressure transmitter 2. In general, the host computer 3 is connected to a plurality of differential pressure transmitters 2 via a transmission path (not shown), and centrally manages the plurality of differential pressure transmitters 2. Here, as described above, the differential pressure transmitter 2 obtains the fluctuation of the differential pressure and the fluctuation of the static pressure in the pressure guiding pipes 6a and 6b, and at least the average value of these ratios and the dispersion value. One of them was calculated, and the clogging of the pressure guiding pipes 6a and 6b was diagnosed by comparison with a threshold value or the like. However, such a function may be provided in the host computer 3 so that the host computer 3 can diagnose clogging of the pressure guiding pipes 6a and 6b.

  That is, the detection unit 19 realized by the MPU 14 of the differential pressure transmitter 2 is realized by the host computer 3, and the differential pressure and static pressure of the pressure in the pressure guiding pipes 6 a and 6 b transmitted from the differential pressure transmitter 2. From the detection result, at least one of the ratio of the differential pressure fluctuation and the static pressure fluctuation and the dispersion value are obtained, and the presence or absence of at least one of the pressure guiding pipes 6a and 6b is diagnosed using this value. You may do it. Alternatively, at least one of the pressure guiding pipes 6a and 6b is determined based on the tendency of change in at least one of the average value and the dispersion value of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure transmitted from the differential pressure transmitter 2. The presence or absence of clogging may be diagnosed.

  Next, the operation of the differential pressure transmitter 2 described above will be described in detail. FIG. 6 is a flowchart showing processing performed in the differential pressure transmitter 2. The processing shown in FIG. 6 is performed by turning on the power of the differential pressure transmitter 2, or by operating the host computer 3 to instruct the differential pressure transmitter 2 to start the operation explicitly. Is started.

  When the operation of the differential pressure transmitter 2 is started, a drive signal is output from the drive circuit 24a provided in the first sensor unit 11a and the drive circuit 24b provided in the second sensor unit 11b. The vibrators 21a and 21b provided in the sensor chip 30 shown in FIG. Then, signals indicating the natural frequencies of the vibrators 21 a and 21 b (signals for driving the vibrators 21 a and 21 b) are output from the first sensor units 11 a and 11 b, and these signals are input to the frequency counter 12.

When the signals from the first sensor units 11a and 11b are input, the frequency counter 12 samples each of these signals using the reference clock output from the oscillation circuit 13, and counts the number of pulses of each signal. The number of pulses counted by the frequency counter 12 is input to the MPU 14. Next, the data collection calculation unit 19a of the detection unit 19 implemented in software by the MPU 14 obtains the natural frequencies f _c and f _r of the transducers 21a and 21b from the number of input pulses, respectively. 2) and (3), for each sampling period of the frequency counter 12, a differential pressure signal x (i) indicating the differential pressure between the pressure guide pipes 6a and 6b and a static pressure signal y ( i) is obtained and stored in the RAM 15 (step S11).

  Next, the data collection calculation unit 19a obtains the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal by using the above-described equations (4) and (5), respectively, in the RAM 15. Store (step S12). Referring to equations (4) and (5), the past differential pressure signal x (i-1) and static pressure signal y (i-1) are used to obtain the swings dx (i) and dy (i). However, when the swings dx (i) and dy (i) are first obtained, for example, the above-described differential pressure signal x (i-1) and static pressure signal y (i-1) are predetermined. The initial value may be stored in the RAM 15. Then, the data collection calculation unit 19a calculates the ratio between the fluctuation dx (i) of the differential pressure signal and the fluctuation dy (i) of the static pressure signal and stores it in the RAM 15 or the EEPROM 16 (step S13).

  Next, the data collection calculation unit 19a reads the ratio between the fluctuation dx (i) of the differential pressure signal for the N cycles obtained in the past and the fluctuation dy (i) of the static pressure signal from the RAM 15 or the EEPROM 16, and described above. The average value avg_p (k) of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure at a certain time point k is obtained using the equation (7), or at the certain time point k using the above-described equation (8). The variance var_p (k) of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure is obtained (step S14). Note that either one of the average value avg_p (k) and the variance var_p (k) may be obtained, or both may be obtained. These calculated values are stored in the RAM 15 or the EEPROM 16.

  When the above processing is completed, the diagnosis unit 19b of the detection unit 19 diagnoses whether or not the pressure guiding tubes 6a and 6b are clogged using the values obtained by the data collection calculation unit 19a (step S15). For example, by reading the threshold value stored in the EEPROM 16 and comparing the value of the variance var_p (k) with the read threshold value, the presence or absence of clogging of the pressure guiding tubes 6a and 6b is diagnosed according to Table 2 described above. Note that the same diagnosis as this diagnosis may be performed only on the average value avg_p (k), or may be performed on both the average value avg_p (k) and the value of the variance var_p (k). Further, the past values stored in the EEPROM 16 are read out, a regression line similar to the regression line shown in FIG. 5 is calculated, and a tendency of change in at least one of the average value and the dispersion value is obtained, and the pressure guiding pipes 6a, You may diagnose the presence or absence of clogging of 6b.

  Next, as a result of the above clogging diagnosis, it is determined whether or not the pressure guiding pipes 6a and 6b are clogged in the diagnosis unit 19b (step S16). When it is determined that the pressure guiding pipes 6a and 6b are clogged (when the determination result is “YES”), the detection unit 19 outputs information indicating the warning or alarm shown in Table 2 and FIG. Then, these are displayed on the display unit 17. Further, the detection unit 19 transmits information indicating this warning or alarm to the host computer 3 via the communication unit 18 (step S17). When the above process is completed and when it is determined in step S16 that the pressure guiding pipes 6a and 6b are not clogged (when the determination result is “NO”), the process returns to step S12.

  In the flowchart shown in FIG. 6, when it is determined in step S16 that the pressure guiding pipes 6a and 6b are clogged, information indicating a warning or an alarm is displayed on the display unit 17 in step S17, and then the steps are uniformly performed. Returning to the processing of S12. However, the processing may be changed according to the warning or alarm such that the diagnosis is stopped in the case of an alarm and the diagnosis is continued in the case of a warning. In the flowchart shown in FIG. 6, when it is determined in step S16 that the pressure guiding pipes 6a and 6b are not clogged, the process simply returns to step S12, but the display unit 17 displays a normal state. May be.

  As described above, according to the present embodiment, the fluctuation of the differential pressure between the pressure guide pipes 6a and 6b and the fluctuation of the static pressure are respectively calculated, and the pressure guide pipe 6a is calculated based on the magnitude of these ratios. , 6b is detected, the clogging of the pressure guiding tubes 6a, 6b can be detected at low cost with high sensitivity. More specifically, the average value and variance of the ratio of the fluctuation of the differential pressure and the fluctuation of the static pressure are obtained, compared with a predetermined threshold value, or the tendency of the change in value is obtained, thereby clogging. From this initial stage, clogging of the pressure guiding pipes 6a and 6b can be detected with high accuracy. Thus, the user can take measures such as investigation, inspection, and maintenance of the pressure guiding pipes 6a and 6b before clogging actually starts or before clogging completely occurs. Is possible. Furthermore, if the detection unit 19 provided in the differential pressure transmitter 2 is realized by the host computer 3, the pressure guiding pipes 6a, 6b can be clogged at low cost without modifying the already installed differential pressure transmitter 2. It is also possible to detect with high sensitivity.

  As mentioned above, although the pressure detector and pressure detection system by embodiment of this invention were demonstrated, this invention is not restrict | limited to embodiment mentioned above, It can change freely within the scope of the present invention. For example, in the above embodiment, the case where the sensor chip 30 capable of detecting the differential pressure and the static pressure in the pressure guiding pipes 6a and 6b is described, but the differential pressure in the pressure guiding pipes 6a and 6b is described. The present invention can also be applied to a case where a sensor for detecting the pressure and a sensor for detecting a static pressure are provided.

  FIG. 7 is a block diagram showing an internal configuration of a modified example of the differential pressure transmitter. The differential pressure transmitter shown in FIG. 7 includes a differential pressure sensor 41 that detects the differential pressure between the pressure guide pipes 6a and 6b, and a static pressure that detects the static pressure of the pipe 4 connected directly or via the pressure guide pipe 7. A pressure sensor 42 and a detection unit 43 are provided. The detection unit 43 corresponds to the detection unit 19 shown in FIG. In FIG. 7, the components other than the differential pressure sensor 41, the static pressure sensor 42, and the detection unit 43 are not shown.

  The detection unit 43 includes a data collection unit 43a, a calculation unit 43b, and a diagnosis unit 43c. The data collection unit 43 a collects the detection result of the differential pressure sensor 41 and the detection result of the static pressure sensor 42. The calculation unit 43b calculates the fluctuation of the differential pressure between the pressure guide pipes 6a and 6b and the fluctuation of the static pressure of the pipe 4 using the various data collected by the data collection unit 43a. Further, an average value and a variance of the ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure are obtained. The diagnosis unit 43c is the same as the diagnosis unit 19b shown in FIG. 2, and compares the calculation result of the calculation unit 43b with a predetermined threshold value, or obtains the tendency of the change in the calculation result of the calculation unit 43b. Thus, the clogging of the pressure guiding pipes 6a, 6b, and 7 is detected.

  Also in the differential pressure transmitter having the above-described configuration, the fluctuation of the pressure difference in the pressure guiding pipes 6a and 6b and the fluctuation of the static pressure of the pipe 4 are calculated, and based on the magnitude of these ratios. Since clogging of the pressure guiding pipes 6a, 6b, and 7 is detected, clogging of the pressure guiding pipe can be detected at low cost with high sensitivity. In addition, although the structure which provided the detection part 43 shown in FIG. 7 in the differential pressure transmitter may be sufficient, this detection part 43 can also be provided in the host computer which manages a differential pressure transmitter.

  Moreover, in the said embodiment, the orifice was mentioned as an example and demonstrated as an aperture_diaphragm | restriction mechanism installed in the piping 4. In FIG. However, the present invention is not limited to this, and the present invention can also be applied when a nozzle or a venturi pipe is provided as a throttling mechanism.

It is a figure which shows the outline | summary of the pressure detection system by one Embodiment of this invention. 3 is a block diagram showing an internal configuration of a differential pressure transmitter 2. FIG. It is a figure which shows the structure of the sensor chip in which the silicon resonant sensor was formed. It is a simulation result which shows the change of fluctuation | variation dx (i) of a differential pressure signal, and fluctuation | variation dy (i) of a static pressure signal. It is a figure which shows an example of the regression line calculated | required by the diagnostic part 19b. 3 is a flowchart showing processing performed in a differential pressure transmitter 2. It is a block diagram which shows the internal structure of the modification of a differential pressure transmitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure detection system 2 Differential pressure transmitter 3 Host computer 4 Piping 6a, 6b Pressure guiding pipe 11 Sensor part 17 Display part 18 Communication part 19 Detection part 19a Data collection calculation part 19b Diagnosis part X Fluid

Claims (7)

A first and a second pressure guiding pipe connected to different positions of a pipe through which a fluid flows, and a sensor for detecting a differential pressure and a static pressure between the pressure in the first pressure guiding pipe and the pressure in the second pressure guiding pipe A pressure detector comprising:
A detector for detecting clogging of at least one of the first and second pressure guiding pipes based on a magnitude of a ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure detected by the sensor; A pressure detector. The detection unit is a calculation unit for obtaining at least one of an average value and a dispersion value of the ratio of the fluctuation of the differential pressure and the fluctuation of the static pressure;
The diagnostic part which diagnoses the presence or absence of the clogging of at least one of the said 1st and 2nd pressure guiding pipe by comparing the value calculated | required in the said calculation part with a predetermined threshold value. Pressure detector. The detection unit is a calculation unit for obtaining at least one of an average value and a dispersion value of the ratio of the fluctuation of the differential pressure and the fluctuation of the static pressure;
At least one of the first and second pressure guiding pipes from a comparison between a current value obtained by the calculation unit and a value obtained in the past by the calculation unit, or a tendency of a change in the value obtained by the calculation unit. The pressure detector according to claim 1, further comprising: a diagnosis unit that diagnoses the presence or absence of clogging. The diagnosis unit compares the value obtained by the calculation unit with a plurality of threshold values to diagnose the degree of clogging of at least one of the first and second pressure guiding tubes,
The pressure detector according to claim 2, further comprising a display unit that displays information indicating a degree of clogging diagnosed by the diagnostic unit.   The pressure detection according to any one of claims 2 to 4, further comprising: a communication unit that transmits at least one of the detection result of the sensor and the calculation result of the calculation unit to a higher-level management device. vessel. In a pressure detection system comprising a pressure detector installed in a pipe through which a fluid flows, and a management device that manages the pressure detector,
The pressure detector includes the pressure detector according to claim 5,
The management device obtains at least one of an average value and a dispersion value of a ratio between the fluctuation of the differential pressure and the fluctuation of the static pressure from the detection result of the sensor transmitted from the pressure detector, A pressure detection system for diagnosing the presence or absence of clogging of at least one of the first and second pressure guiding pipes using a value. In a pressure detection system comprising a pressure detector installed in a pipe through which a fluid flows, and a management device that manages the pressure detector,
The pressure detector includes the pressure detector according to claim 5,
The management device diagnoses the presence or absence of clogging of at least one of the first and second pressure guiding pipes from the tendency of change in the calculation result of the calculation unit transmitted from the pressure detector. .

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