JP4379680B2 - Pressure guiding tube blockage detection device - Google Patents

Description

BACKGROUND OF THE INVENTION
The present invention relates to a device for detecting clogging of a pressure guiding tube used in a pressure transmitter, a differential pressure transmitter, and the like, and more particularly to a pressure guiding tube blocking device that is not easily affected by transient pressure fluctuations.
[0001]
[Prior art]
In a pressure transmitter or a differential pressure transmitter, if the pressure guiding pipe that guides the pressure to the transmitter main body is clogged, an accurate pressure or differential pressure cannot be detected. Patent Document 1 and Patent Document 2 describe an invention of an apparatus for detecting such blocking of a pressure guiding tube. The outline of the invention described in Patent Document 2 will be described below.
[0002]
FIG. 5 shows the configuration of the conduit blockage device. An orifice 82 is installed in the pipe 81, and fluid flows in the direction of the arrow. The upstream pressure PH and the downstream pressure PL of the orifice 82 are taken out by the pressure guiding pipes 83a and 83b, respectively, and input to the differential pressure transmitter 84 to detect the differential pressure and the static pressure.
[0003]
The differential pressure and static pressure signals are input to the conduit blockage detecting device 9 to diagnose whether or not the pressure guiding tubes 83a and 83b are clogged. For this purpose, the differential pressure and static pressure signals are input to a swing calculation unit 911 in the dispersion calculation unit 91, and swing is calculated based on the following equations (3) and (4).
_Differential pressure fluctuation F _iΔP = ΔP _i −ΔP _i−1 (3)
Static pressure fluctuation F _iP = P _i −P _i−1 (4)
Here, ΔP _i and ΔP _i−1 are the current and previous differential pressures, and P _i and P _i−1 are the current and previous static pressures, respectively.
[0004]
The swing is input to the square sum calculating section 912, the following (5), the square sum sigma _{[Delta] P} of the differential pressure _fluctuation, the square sum sigma _P of the hydrostatic swing is calculated based on the equation (6) The These sums of squares are values representing the degree of variation in data and are equivalent to variance.
_{Sum of} squares of differential pressure fluctuation σ _ΔP = Σ (F _iΔP * F _iΔP ) / n (5)
Static pressure fluctuation square sum σ _P = Σ (F _iP * F _iP ) / n (6)
Note that n is the number of data to be integrated.
[0005]
These square sums are input to the determination unit 93 to determine whether or not the pressure guiding tube is clogged. Therefore, the ratio calculation unit 92 calculates a ratio between the square sum of the differential pressure fluctuation and the square sum of the static pressure fluctuation, and clogging is determined based on the ratio. In this way, it is possible to determine which one or both of the high pressure side and low pressure side pressure guide tubes are clogged.
[0006]
In addition, the correlation calculation unit calculates the cross-correlation between the differential pressure fluctuation and the static pressure fluctuation and the autocorrelation of the static pressure fluctuation according to the following equations (7) and (8). It is also determined whether the pressure tube is clogged.
Cross correlation between differential pressure fluctuation and static pressure fluctuation C1 = Σ (F _iΔP * F _iP ) (7)
Autocorrelation of static pressure fluctuation C2 = Σ ( _FiP * _FiP ) (8)
[Patent Document 1]
Japanese Patent No. 3129121 [Patent Document 2]
Japanese Patent Application No. 2002-297174 Specification [0007]
[Problems to be solved by the invention]
However, such a pipe blockage detecting device has the following problems.
[0008]
As is clear from the equations (3) and (4), the variance and correlation are calculated using the difference between the current measurement value and the previous measurement value as the fluctuation value. However, while the differential pressure or static pressure is transiently changing in one direction, the fluctuation value changes due to this fluctuation component, and accurate fluctuation can be calculated. Therefore, there is a problem that an accurate clogging determination cannot be performed.
[0009]
Accordingly, an object of the present invention is to provide a pressure guiding tube blockage detecting device capable of accurately determining clogging even when a differential pressure or a static pressure fluctuates in one direction.
[0010]
[Means for Solving the Problems]
In order to solve such a problem, the invention according to claim 1 of the present invention receives a differential pressure signal between two pressure guiding tubes and a static pressure signal of one of the pressure guiding tubes. a fluctuation calculating unit for calculating a swing of the signal, the output of the fluctuation calculating unit is input, a variance calculating unit for calculating the sum of squares of the static pressure swings square sum of the differential pressure swing the output of the variance calculating section is input, and a determination unit for detecting clogging of the impulse line, the determination unit and the square sum of the square sum and the differential pressure swing of the differential pressure swing It detects the 2 blockage of the impulse line from square sum ratio of sum of the static pressure swing, the swing operation unit, so as to calculate the swing in accordance with the following equation (9), the determination parts are the sum of squares of the differential pressure swing compared with a predetermined reference value, and when the variation of the 2 Nowahi is large, the two Shirube圧In which both has to be determined that clogged the. Unaffected by transient changes in pressure.
Swing value Fi = P (i) −2 × P (i−1) + P (i−2) (9)
However, P (i), P (i-1), and P (i-2) are differential pressure or static pressure signals at times i, i-1, and i-2, respectively.
[0012]
According to a second aspect of the present invention, in the first aspect of the present invention, the determination unit may include a pressure guiding tube on a side other than the pressure guiding tube that has obtained the static pressure signal when the square sum ratio is a value close to 1. It is determined that the pressure-guiding tube on the side from which the static pressure signal has been obtained is blocked when it is determined that the square sum ratio has a large variation. This can be detected when either pressure guiding tube is clogged.
[0014]
According to the third aspect of the present invention, the differential pressure signal between the two pressure guiding pipes and the static pressure signal of either of the pressure guiding pipes are input, and the swing calculation unit that calculates the swing of these signals, the output of the fluctuation calculating unit is input, a variance calculating unit for calculating the sum of squares of the static pressure swings square sum of the differential pressure swing, the output of the fluctuation calculating unit is input, is input a correlation calculation unit for calculating a correlation value which is the sum of the product of oscillation of the oscillating and the static pressure signal of the differential pressure signal was, the the sum of squares of the differential pressure swing to the variance calculating unit has calculated the correlation value sum of squares and the correlation calculation unit of the static pressure swing computed is input, and a determination unit for detecting clogging of the impulse lines, the square of the determination unit is the differential pressure swing It detects a blockage of the impulse line from the sum and the square sum ratio of the correlation value static pressure swing, the swing operation unit, the following (10) It is obtained so as to calculate the swing based on. Clogging can be detected without being affected by transient changes in pressure.
Swing value Fi = P (i) −2 × P (i−1) + P (i−2) (10)
However, P (i), P (i-1), and P (i-2) are differential pressure or static pressure signals at times i, i-1, and i-2, respectively.
[0016]
According to a fourth aspect of the present invention, in the third aspect of the invention, when the determination unit is clogged with a pressure guiding tube on a side other than the pressure guiding tube that has obtained the static pressure signal when the ratio is a value close to 1. It is determined that when the variation in the ratio is large, it is determined that the pressure guiding tube on the side where the static pressure signal is obtained is clogged. It can be detected that one of the pressure guiding tubes is clogged.
[0017]
Invention of claim 5, wherein, in the invention of claim 3 or claim 4, wherein said determination unit compares the sum of squares of the differential pressure swing with a predetermined reference value, the two guiding tube Both are determined to be clogged. It is possible to detect clogging of both pressure guiding tubes.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a pressure guiding tube blockage detecting device according to the present invention. In FIG. 1, reference numeral 1 denotes a swing calculation unit which _receives a differential pressure signal and a static pressure _signal and calculates and outputs a static pressure swing F _iPH and a differential pressure swing F _iΔP . The static pressure signal uses the pressure on the high pressure side.
[0019]
A dispersion calculating unit 21 receives the static pressure fluctuation F _iPH and the differential pressure fluctuation F _iΔP and calculates and outputs the differential pressure dispersion value D1 and the static pressure dispersion value D2. _{Reference numeral} 22 denotes a correlation calculation unit that _receives the static pressure fluctuation F _iPH and the differential pressure fluctuation F _iΔP and calculates and outputs the correlation coefficient D3 thereof. Reference numeral 3 denotes a determination unit that receives the differential pressure dispersion value D1, the static pressure dispersion value D2, and the correlation coefficient D3, and determines clogging of the pressure guiding tube from these values.
[0020]
Next, the differential pressure measurement will be described. FIG. 2 is a principle diagram of differential pressure measurement. A fluid flows in the pipe 41 in the direction of the arrow. An orifice 42 is installed in the middle of the pipe 41, and upstream and downstream pressures are guided to the differential pressure transmitter 6 through pressure guiding pipes 51 and 52. It can be considered that the pressure guiding pipes 51 and 52 are first order lag elements of the time constants TH and TL with respect to the pressure change, and that the time constants TH and TL increase when the pressure guiding pipe is clogged.
[0021]
The differential pressure transmitter 6 incorporates a pressure detection unit and an electric circuit, which serve as a first-order lag element 61 having a time constant Ttrans. Further, since there may be a problem in control if there is a minute fluctuation, the differential pressure signal and the high-pressure side or low-pressure side static pressure signal are output after being averaged as in 62.
[0022]
Next, the embodiment of FIG. 1 will be described in detail. Fluctuation calculating unit 1 below (11), calculates the static pressure fluctuation _{F IPH,} the differential pressure fluctuation _{F AiderutaP} based on equation (12). The subscript i indicates the value of time i.
Static pressure fluctuation F _{iPH at} time i = PH (i) −2 × PH (i−1) + PH (i−2) (11)
Differential pressure fluctuation F _iΔP = ΔP (i) −2 × ΔP (i−1) + ΔP (i−2) (12) at time i
Here, PH (i) is the static pressure signal at time i, and ΔP (i) is the differential pressure signal. That is, the current static pressure (differential pressure) and the previous static pressure (differential pressure) are added, and then twice the previous static pressure (differential pressure) is subtracted.
[0023]
Simply calculating the swing by subtracting the previous value from the current value tends to be positive when the pressure is increasing and tends to be negative when the pressure is decreasing. Since the determination is performed on the assumption that the swing is originally random, if there is such a tendency, a change in swing due to clogging of the pressure guiding tube cannot be distinguished from a change in the operating state, which may cause an erroneous determination. In the equations (11) and (12), the change in the operating state does not appear in the swing calculation, so that a correct determination can be made.
[0024]
This will be described with reference to FIG. FIG. 3 shows an example of changes in the measured pressure value, where the horizontal axis represents time and the vertical axis represents the pressure value. Curve 7 is a graph of the measured pressure, which increases while finely varying. ● is a measurement point. If the fluctuation is calculated by the difference between the current measurement value and the previous measurement value as in the conventional example, an increase component is included in the fluctuation value. On the other hand, since the equation (11) can be decomposed into the following equation (13), the increasing component is eliminated and does not appear in the oscillation _FiPH . Therefore, only the swing component can be extracted. The same applies to the differential pressure.
_FiPH = {PH (i) -PH (i-1)}-{PH (i-1) -PH (i-2)} (13)
[0025]
The dispersion calculation unit 21 calculates the dispersions D1 and D2 of the differential pressure fluctuation and the static pressure fluctuation based on the following equations (14) and (15).
_Differential pressure fluctuation dispersion D1 = Σ (F _iΔP × F _iΔP ) (14)
Static pressure fluctuation dispersion D2 = Σ ( _FiPH × _FiPH ) (15)
F _iPH and F _iΔP are the fluctuations of the static pressure and the differential pressure obtained by the equations (11) and (12), respectively. The addition is performed for n consecutive data.
[0026]
The correlation calculation unit 22 calculates a correlation coefficient D3 between the static pressure fluctuation and the differential pressure fluctuation based on the following equation (16).
Correlation coefficient D3 = Σ (F _iPH × F _iΔP ) (16)
Here, F _iPH and F _iΔP are the static pressure fluctuation and the differential pressure fluctuation obtained by the equations (11) and (12), respectively. Further, the subscript i indicates that a temporally equivalent value is used.
[0027]
The determination unit 3 determines clogging of the pressure guiding tube based on the input value. For this purpose, the dispersion ratio D4 is calculated by the following equation (17), and the correlation coefficient D5 is calculated by the following (18).
Dispersion ratio D4 = D1 / D2 (17)
Correlation coefficient D5 = D3 / D2 (18)
Here, D1 is the variance of the differential pressure fluctuation obtained by the above equation (14), D2 is the variance of the static pressure fluctuation obtained by the above equation (15), and D3 is the correlation coefficient obtained by the above equation (16). It is. The dispersion ratio D4, the correlation coefficient D5, and the differential pressure fluctuation dispersion D1 are compared with the reference values R4, R5, and R1 in the normal state to determine clogging.
[0028]
The dispersion ratio D4 can detect clogging of only the low pressure side impulse line or only the high pressure side impulse line. When the low pressure side pressure guiding tube is clogged, the low pressure side static pressure fluctuation is close to zero, so that the differential pressure fluctuation D1 is close to the high pressure side static pressure fluctuation D2. Therefore, the dispersion ratio D4 approaches 1. When the high-pressure side pressure guiding tube is clogged, the dispersion D2 of the static pressure fluctuation on the high-pressure side becomes small, so that the dispersion ratio D4 varies greatly.
[0029]
Correlation coefficient D5 can also detect clogging of only the low-pressure side impulse line or only the high-pressure side impulse line. When the low pressure side pressure guiding tube is clogged, the static pressure fluctuation on the low pressure side is close to zero, so the differential pressure fluctuation is close to the static pressure fluctuation on the high pressure side, and the correlation coefficient D5 approaches 1. When the high pressure side pressure guiding tube is clogged, the differential pressure fluctuation becomes close to the low pressure side static pressure fluctuation, and is not related to the high pressure side static pressure fluctuation. Therefore, the correlation coefficient D3 approaches zero. However, since the static pressure fluctuation is also reduced, the dispersion D2 of the static pressure fluctuation of the denominator approaches zero at the speed of the square. Therefore, the variation of the correlation coefficient D5 becomes large.
[0030]
Clogging of both the high-pressure side pressure guiding tube and the low-pressure side pressure guiding tube is determined by comparing the variance D1 of the differential pressure fluctuation with the value at the normal value calculated in advance. When both pressure guiding tubes are clogged, the fluctuation of the differential pressure is generally reduced. However, even if the pressure guiding tube on the high pressure side is clogged, the variance of the differential pressure fluctuation may be a normal value, so it is necessary to combine the determination with the dispersion ratio D4 or the determination with the correlation coefficient D5.
[0031]
FIG. 4 is a table summarizing the determination criteria described above. For the clogging of both pressure guiding pipes, the differential pressure fluctuation dispersion (differential pressure dispersion) D1 converges to zero, but may increase immediately before clogging. Variations in both the dispersion ratio D4 and the correlation coefficient D5 increase. For clogging of the high pressure side (H side) pressure guiding tube, the differential pressure dispersion D1 converges on the oscillation of the low pressure side (L side) but may increase immediately before clogging. Variations in both the dispersion ratio and the correlation coefficient increase.
[0032]
For the clogging of the low pressure side (L side) pressure guiding tube, the differential pressure dispersion D1 converges on the high pressure side (H side) oscillation, but may increase immediately before clogging. Both the dispersion ratio D4 and the correlation coefficient converge to 1. In a normal state, the dispersion ratio D4 and the correlation coefficient D5 both take a value of 0 to 1, but it approaches 1 when the high-pressure side and low-pressure side (H / L) swings are similar.
[0033]
Therefore, when either the high pressure side pressure guiding tube or the low pressure side pressure guiding tube is clogged by using any combination of the differential pressure dispersion D1 and the dispersion ratio D4 or the differential pressure dispersion D1 and the correlation coefficient D5. And it is possible to distinguish when both impulse lines are clogged.
[0034]
In this embodiment, the high-pressure side pressure is used as the static pressure, but the low-pressure side pressure can also be used. When the pressure on the low pressure side is used, the clogging of the high pressure side impulse line and the clogging of the low pressure side impulse line may be reversed in the above description.
[0035]
That is, with respect to the dispersion ratio D4, when the high pressure side pressure guiding tube is clogged, the fluctuation on the high pressure side becomes small, so that the differential pressure fluctuation is close to the static pressure fluctuation on the low pressure side, and the dispersion ratio approaches 1. When the low pressure side pressure guiding tube is clogged, the static pressure fluctuation on the low pressure side becomes close to zero, and the dispersion ratio varies greatly.
[0036]
Regarding the correlation coefficient D5, when the high-pressure side pressure guiding tube is clogged, the differential pressure fluctuation and the static pressure fluctuation are approximately the same, and the correlation coefficient D5 approaches 1. When the low pressure side pressure guiding tube is clogged, there is no correlation between the differential pressure fluctuation and the static pressure fluctuation, and the correlation value approaches zero. However, since the denominator approaches zero in the square, the variation increases.
【The invention's effect】
As is clear from the above description, the following effects can be expected according to the present invention.
According to the first aspect of the present invention, the differential pressure signal between the two pressure guiding tubes and the static pressure signal of one of the pressure guiding tubes are input, and the swing calculation unit that calculates the swing of these signals the output of the fluctuation calculating unit is input, a variance calculating unit for calculating the sum of squares of the static pressure swings square sum of the differential pressure swing, the output of the dispersion calculating unit is input, the and a judging unit for detecting clogging of impulse lines, the square of the determination unit square sum of the static pressure swings square sum of square sum and the differential pressure swing of the differential pressure swing detects a blockage of the impulse line from a sum ratio, the fluctuation calculating unit, so as to calculate the swing in accordance with the following equation (19), wherein the determination unit, the square sum of the differential pressure swing Is compared with a predetermined reference value, and when the variation of the square sum ratio is large, it is determined that both of the two pressure guiding tubes are clogged. It was.
Oscillation value Fi = P (i) −2 × P (i−1) + P (i−2) (19)
However, P (i), P (i-1), and P (i-2) are differential pressure or static pressure signals at times i, i-1, and i-2, respectively.
[0037]
Even if the plant is in a transient state and the pressure or differential pressure is rising or falling, these pressure changes do not appear to swing, so it is possible to accurately determine clogging of the pressure guiding pipe effective. In addition, even if the differential pressure or the pressure value changes due to a uniform temperature change or the like, these changes do not appear in oscillation, so that there is an effect that clogging can be detected accurately. Further, by using three values continued in time and subtracting twice the intermediate value, pressure fluctuation can be removed, and only the swinging portion can be taken out purely. Therefore, there is an effect that clogging of the pressure guiding tube can be accurately detected. Further, the determination unit compares the square sum of the differential pressure signal with a predetermined reference value, and when the variation of the square sum ratio is large, both of the two pressure guiding tubes are clogged. I decided to judge. There is an effect that it is possible to accurately detect clogging of both pressure guiding pipes without being affected by the state of the plant.
[0040]
According to a second aspect of the present invention, in the first aspect of the present invention, the determination unit is configured to introduce the static pressure signal on the side other than the pressure guiding tube when the square sum ratio is a value close to 1. It is determined that the pressure pipe is clogged, and when the variation in the square sum ratio is large, it is determined that the pressure guiding pipe on the side where the static pressure signal is obtained is clogged. There is an effect that it is possible to accurately detect that one of the pressure guiding tubes is clogged without being influenced by the state of the plant. In addition, there is also an effect that it is not necessary to check a normal value in advance.
[0042]
According to the third aspect of the present invention, the differential pressure signal between the two pressure guiding pipes and the static pressure signal of either of the pressure guiding pipes are input, and the swing calculation unit that calculates the swing of these signals the output of the fluctuation calculating unit is input, a variance calculating unit for calculating the sum of squares of the static pressure swings square sum of the differential pressure swing, the output of the fluctuation calculating unit is input, a correlation calculation unit for calculating a correlation value which is the sum of the product of oscillation of the oscillation of the inputted difference pressure signal and the static pressure signal, the square sum of the differential pressure swing to the variance calculating unit has calculated wherein the correlation value sum of squares and the correlation calculation unit of the static pressure swing computed is input, and a determination unit for detecting clogging of the impulse lines, the judgment unit of the differential pressure swings with the sum of squares and the square sum ratio of the static pressure swing and the correlation values to detect a blockage of the impulse line, the fluctuation calculating unit, following ( 0) was set to calculates the swing based on equation.
Swing value Fi = P (i) −2 × P (i−1) + P (i−2) (20)
However, P (i), P (i-1), and P (i-2) are differential pressure or static pressure signals at times i, i-1, and i-2, respectively.
[0043]
Even if the plant is in a transient state and the pressure or differential pressure is rising or falling, these pressure changes do not appear to swing, so it is possible to accurately determine clogging of the pressure guiding pipe effective. In addition, even if the differential pressure or the pressure value changes due to a uniform temperature change or the like, these changes do not appear in oscillation, so that there is an effect that clogging can be detected accurately. Further, by using three values continued in time and subtracting twice the intermediate value, pressure fluctuation can be removed, and only the swinging portion can be taken out purely. Therefore, there is an effect that clogging of the pressure guiding tube can be accurately detected.
[0046]
According to a fourth aspect of the present invention, in the third aspect of the present invention, when the ratio is a value close to 1, the determination unit is clogged with a non-pressure tube that has obtained the static pressure signal. When the variation in the ratio is large, it is determined that the pressure guiding tube on the side where the static pressure signal is obtained is clogged. There is an effect that it is possible to accurately detect that one of the pressure guiding tubes is clogged without being influenced by the state of the plant. In addition, there is also an effect that it is not necessary to check a normal value in advance.
[0047]
According to the invention of claim 5, wherein, in the invention of claim 3 or claim 4, wherein said determination unit compares the sum of squares of the differential pressure swing with a predetermined reference value, the two Judgment was made that both of the impulse lines were clogged. There is an effect that it is possible to accurately detect clogging of both pressure guiding pipes without being affected by the state of the plant.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a configuration diagram showing a state of differential pressure measurement.
FIG. 3 is a characteristic diagram showing the effect of the present invention.
FIG. 4 is a table showing criteria for detecting clogging.
FIG. 5 is a configuration diagram of a conventional pressure guiding tube blockage detection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oscillation calculating part 21 Dispersion calculating part 22 Correlation calculating part 3 Determination part 51,52 Pressure guiding tube

Claims (5)

The differential pressure signal between the two pressure guiding tubes and the static pressure signal of one of the pressure guiding tubes are input, and the swing calculation unit that calculates the swing of these signals and the output of this swing calculation unit are input. is a variance calculator for calculating the sum of squares of the static pressure swings square sum of the differential pressure swing, said a sum of squares static pressure swing of the differential pressure swing this variance calculating section has computed is square sum input of the dynamic, the and a judging unit for detecting a blockage of impulse lines, the judgment unit the the square sum electrostatic sum of squares and the differential pressure swing of the differential pressure swing with the square sum ratio of the sum of squares of the pressure swing detecting a blockage of the impulse line, the fluctuation calculating unit, so as to calculate the swing in accordance with the following equation (1),
The determination unit, a sum of squares of the differential pressure swing compared with a predetermined reference value, and when the variation of the 2 Nowahi is large, when both of the two impulse lines are clogged A pressure guiding tube blockage detecting device characterized in that a determination is made.
Swing value Fi = P (i) −2 × P (i−1) + P (i−2) (1)
However, P (i), P (i-1), and P (i-2) are differential pressure or static pressure signals at times i, i-1, and i-2, respectively.   The determination unit determines that the pressure guiding pipe on the side other than the pressure guiding pipe that has obtained the static pressure signal is clogged when the square sum ratio is close to 1, and the variation in the square sum ratio is large. 2. The pressure guiding tube blockage detecting device according to claim 1, wherein it is determined that the pressure guiding tube on the side where the static pressure signal is obtained is sometimes clogged. The differential pressure signal between the two pressure guiding tubes and the static pressure signal of one of the pressure guiding tubes are input, and the swing calculation unit that calculates the swing of these signals and the output of this swing calculation unit are input. is a variance calculator for calculating the sum of squares of the static pressure swings square sum of the differential pressure swing, a swing of the differential pressure signal the fluctuation calculating unit has calculated the static pressure signal swing is input, a correlation calculation unit for calculating a correlation value which is the sum of the product of oscillation of the oscillating and the static pressure signal of the differential pressure signal, of the differential pressure swing to the variance calculating unit has calculated sum of squares and the sum of squares and the correlation calculation unit of the static pressure swing is input the correlation value calculated, and a determination unit for detecting clogging of the impulse line, the determination unit is the differential pressure from sum of squares and the square sum ratio of the correlation value static pressure oscillation of the oscillating detects a blockage of the impulse line, the fluctuation calculating unit, the lower (2) impulse line blockage detection device is characterized in that so as to calculate the swing based on equation.
Swing value Fi = P (i) −2 × P (i−1) + P (i−2) (2)
However, P (i), P (i-1), and P (i-2) are differential pressure or static pressure signals at times i, i-1, and i-2, respectively.   The determination unit determines that the pressure guide tube on the side other than the pressure guide tube that has obtained the static pressure signal is clogged when the ratio is close to 1, and determines that the static pressure signal is large when the ratio varies greatly. 4. The pressure guiding tube blockage detecting device according to claim 3, wherein it is determined that the pressure guiding tube on the obtained side is clogged. The determination unit, according to claim 3 in which the square sum of the differential pressure swing compared with a predetermined reference value, characterized by being adapted to determine both of the two impulse lines are clogged Alternatively, the pressure guiding tube blockage detecting device according to claim 4.

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