JP4665163B2 - Leak inspection method and leak inspection apparatus - Google Patents

Description

  The present invention relates to a leakage inspection method and a leakage inspection apparatus for inspecting leakage of fluid from pipes and tanks.

  When a fluid such as fuel gas or petroleum is transported by piping or stored in various pressure tanks, it is very important to inspect the presence or absence of fluid leakage. This is because leakage of these fluids leads to loss of the fluid itself, danger of ignition, environmental pollution, and the like.

  Among these methods for inspecting leakage, the most basic method is a pressure type leakage inspection method. In this method, the fluid in the pipe or tank is pressurized to a predetermined pressure, and the pressure change of the fluid in the pipe or tank is measured while the pipe or tank is closed, thereby inspecting the presence or degree of fluid leakage. To do.

  However, the pressure of these fluids changes due to changes in ambient temperature. Therefore, in this pressure type leak inspection method, in order to improve the accuracy of the leak inspection and make it a reliable inspection, when measuring the pressure change of the fluid in the pipe or the tank, the pressure fluctuation component is It is necessary to determine whether it is caused by the leakage of the fluid or the temperature change of the fluid and appropriately remove the change caused by the temperature change of the fluid.

  Therefore, attempts have been made to eliminate such temperature-induced fluctuations by performing temperature correction using the measured fluid or the temperature of the piping or tank wall.

  For example, Patent Document 1 discloses that a pipeline is pressurized to a predetermined pressure and the pressure is measured, the fluid temperature is measured, temperature correction is performed based on the fluid temperature, and the pipeline is based on the corrected pressure value. A technique for detecting the leakage of the image is disclosed.

  In Patent Document 2, the pipe wall temperature or ambient temperature of the pipe is measured at the measurement start time and at the measurement time, and the pressure change correction value is determined based on the temperature at the measurement time and the temperature at the specific start time. Is disclosed in consideration of heat transfer from the pipe to the air in the pipe, and the leakage of the pipe is detected using this pressure change correction value.

JP 2001-27576 A Japanese Patent No. 3488198

  However, both of these techniques perform temperature correction on the assumption that the fluid and the thermal dynamics of the piping or tank are known. Therefore, it is necessary to know these characteristics in advance. If the characteristics are unknown or the target characteristics are different from the assumed characteristics, it is not possible to detect leakage with high accuracy. In addition, since actual pipes and tanks have a large spatial extent and are governed by complicated boundary conditions, there are few cases where simple dynamics as described in the above-mentioned patent document are described.

  In addition, these temperature correction methods assume that the fluid and the thermal dynamics of the piping or tank are constant, that is, the system is invariant in time, and the characteristics of the inspection object itself have changed. Sometimes I can't respond. However, the actual thermal dynamics and temperature effects of piping and tanks usually change depending on the surrounding conditions such as weather conditions.

  As described above, in the conventional technology that requires knowledge of the thermal characteristics and applies the fixed correction method, the temperature-induced variation in the fluid pressure change can be reliably and accurately determined according to the change in the situation. It was difficult to remove.

  The present invention has been made in view of such problems, and its purpose is to provide a highly accurate measurement of the temperature-induced fluctuation in the pressure change of the fluid in the pipe or tank in the pressure-type leak test according to the change in the situation. It is an object of the present invention to provide a leakage inspection method and a leakage inspection apparatus that can be surely removed by the above.

The leakage inspection method of the present invention measures the pressure of a fluid in a container to obtain a measurement pressure, and measures at least one of the temperature of the fluid in the container, the temperature of the container wall, and the temperature around the container. Output the estimated value of the temperature-induced pressure component occupying the measured pressure based on the measured temperature and estimate the characteristics based on the error signal that is the difference between the measured pressure and the estimated value of the temperature-induced pressure component The temperature-induced pressure component is adaptively estimated by the output of the adaptive estimator, and the temperature-induced pressure component is subtracted from the measured pressure to obtain the temperature-compensated pressure. Based on this, the container is inspected for leaks. In this case, using a digital filter with the aforementioned adaptive estimator is preferably so as to adaptively estimate the temperature caused pressure components by the output of the digital filter, further the error signal as said temperature compensation pressure It is more preferable to use.

  Here, “fluid” refers to a substance in which two or more phases of gas, liquid or solid are mixed in addition to a substance in a single phase composed of gas or liquid, and a mixture of a plurality of them. It also includes the meaning. Further, the “container” means a “vessel” that fills the inside thereof with a fluid, and is a superordinate concept that includes the above-described piping, a tank having a larger volume than the piping, and the like. Further, “the pressure of the fluid in the container” means not only the absolute pressure of the fluid in the container but also the relative pressure with other fluids. In addition, “adaptive estimation” is not a uniform estimation based on a certain relationship. For example, the estimation method changes depending on the situation, such as the time of inspection and the position of the inspection target. It means that By comprising in this way, estimation according to the situation can be performed. The “adaptive estimator” means means for performing the adaptive estimation as described above. For example, in addition to “digital filters” such as FIR (Finite Impulse Response) filters and IIR (Infinite Impulse Response) filters. Including neural networks and fuzzy estimators. That is, the “adaptive estimator” is a superordinate concept including a “digital filter”.

The leakage inspection apparatus of the present invention is provided with the following structural requirements (A) to (E).
(A) Pressure measuring means for measuring the pressure of the fluid in the container (B) Temperature measuring means for measuring at least one of the temperature of the fluid in the container, the temperature of the container wall, and the temperature around the container ( C) Based on the measured temperature measured by the temperature measuring means, the estimated value of the temperature-induced pressure component occupying the measured pressure measured by the pressure measuring means is output, and the measured pressure and the estimated value of the temperature-induced pressure component are An adaptive estimator that adaptively estimates the temperature-induced pressure component by adaptively changing the estimated characteristics based on the error signal that is the difference (D) Temperature-induced pressure adaptively estimated by the output of the adaptive estimator Temperature compensation means for obtaining the temperature compensation pressure by subtracting the component from the measured pressure (E) Inspection means for inspecting the leakage of the container based on the change in the temperature compensation pressure obtained by the temperature compensation means. There it is composed of the adaptive estimator is de digital filter is preferably so as to estimate the temperature caused pressure component adaptively by the output of the digital filter, further the temperature compensating means, as the temperature compensation pressure It is more preferable to use the error signal.

  In the leakage inspection method and the leakage inspection apparatus of the present invention, the temperature-induced pressure component in the measurement pressure is adaptively estimated based on the measurement pressure and the measurement temperature, and the temperature-induced pressure component is subtracted from the measurement pressure to obtain the temperature. Compensation pressure is required. The container leakage inspection is performed based on the change in the temperature compensation pressure. When an adaptive estimator is used, the temperature-induced pressure component is adaptively estimated based on this output, and an error signal is used as the temperature compensation pressure.

  According to the leakage inspection method and the leakage inspection apparatus of the present invention, the temperature-induced pressure component occupying the measured pressure of the fluid in the container is adaptively estimated, and leakage is performed based on the change of the temperature compensation pressure subtracted from the measured pressure. Since the inspection is performed, the temperature-induced fluctuations in the fluid pressure change can be reliably removed with high accuracy according to the change in the situation, and the highly accurate and reliable leak inspection can be performed. it can.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a schematic configuration of a leakage inspection system according to the first embodiment of the present invention. This leakage inspection system includes a pipe 2 to be inspected and a leakage inspection apparatus 1 that performs inspection.

  The pipe 2 serves as a path for transporting fluids such as fuel gas and petroleum, for example, and fills these fluids. The pipe 2 has a pair of valves 21A and 21B at predetermined positions. These valves 21 </ b> A and 21 </ b> B close a predetermined piping region when performing a leakage inspection. Various fluids other than those described above can be applied as the fluid. Hereinafter, in the present embodiment, a case where the fluid filled in the pipe 2 is a gas will be described.

  The leak test apparatus 1 includes an air cylinder 11, a piston 12, a linear actuator 13, a pressure sensor 14, a temperature sensor 15, an adaptive estimation unit 161, a subtraction unit 162, a control determination unit 17, and a drive unit. 18 and a display unit 19.

  Here, the pressure sensor 14 in the present embodiment is a specific example of the “pressure measuring unit” in the present invention, and the temperature sensor 15 is a specific example of the “temperature measuring unit” in the present invention. 161 is a specific example of the “adaptive estimator” in the present invention, the subtraction unit 162 is a specific example of the “temperature compensation unit” in the present invention, and the control determination unit 17 is the “inspection unit” in the present invention. It is one specific example.

  The air cylinder 11, together with the piston 12 and the linear actuator 13, causes a fluid having an inflow mass flow rate G (t) (kg / s) to flow into the pipe 2 and pressurizes the fluid in the pipe 2. Specifically, the linear actuator 13 drives the air cylinder 11 and the piston 12 so that a fluid having an inflow mass flow rate G (t) flows into the pipe 2. The linear actuator 13 is further driven by a drive unit 18 as will be described later. In addition, as what pressurizes the fluid in the piping 2, it is not restricted to the combination of the linear actuator 13 and the air cylinder 11, For example, the combination of pressure sources, such as a compressor, and an electromagnetic valve, an electric or manual pump, or Other combinations such as a combination of a moving coil and a diaphragm may be used.

  The pressure sensor 14 measures the pressure of the fluid in the pipe 2. The pressure sensor 14 is disposed at a predetermined position of the pipe 2. The pressure (pressure signal P (t)) measured by the pressure sensor 14 is output to the adaptive estimation unit 161 and is used when adaptively estimating a temperature-induced pressure component described later. Note that the pressure measured by the pressure sensor 14 is not limited to an absolute pressure. As will be described later, gauge pressure (pressure difference between the pressure P in the pipe 2 and atmospheric pressure (external pressure)), and the like. It may be a relative pressure with the fluid.

  The temperature sensor 15 measures at least one of the temperature of the fluid in the pipe 2, the temperature of the pipe wall of the pipe 2, and the temperature around the pipe 2. Similar to the pressure sensor 14, the temperature sensor 15 is disposed at a predetermined position of the pipe 2. The temperature (temperature signal x (t)) measured by the temperature sensor 15 is output to the adaptive estimation unit 161 in the same manner as the pressure signal P (t), and is used when adaptively estimating the temperature-induced pressure component. It is like that.

  Based on the pressure signal P (t) output from the pressure sensor 14 and the temperature signal x (t) output from the temperature sensor 15, the adaptive estimation unit 161 occupies the temperature-induced pressure in the pressure signal P (t). It has a function to estimate components adaptively. Specifically, an estimated value y (t) of the temperature-induced pressure component is output based on the temperature signal x (t), and the pressure signal P (t) and the estimated value y (t) of the temperature-induced pressure component are Based on the error signal e (t) (= P (t) −y (t)), which is a difference between the two, the estimated characteristic is adaptively changed, and the temperature-induced pressure component y (t ) Is adaptively estimated. Although details of the adaptive estimation method will be described later, the temperature distribution in the fluid in the pipe 2 exists by adaptively estimating the temperature-induced pressure component in the measured pressure of the fluid in the pipe 2 as described above. Even in a situation where the pressure changes from time to time, the temperature-induced fluctuation in the fluid pressure change can be adaptively removed according to the situation.

  The subtractor 162 subtracts the temperature-induced pressure component y (t) adaptively estimated and output by the adaptive estimator 161 from the pressure signal P (t) output from the pressure sensor 14 to thereby obtain the temperature compensated pressure. That is, it has a function for obtaining the error signal e (t). The error signal e (t) obtained in this way is output to the control determination unit 17 and also to the adaptive estimation unit 161, and the estimation characteristics of the adaptive estimation unit 161 are adaptively adjusted as described above. It is used when changing.

  As these adaptive estimation sections 161, for example, various adaptive estimator configurations such as a neural network and a fuzzy estimator can be applied in addition to digital filters such as an FIR filter and an IIR filter. Also, various configurations can be applied as an adaptive algorithm (an algorithm that adaptively changes the estimation characteristics based on the error signal e (t)). For example, when the adaptive estimation unit 161 is configured by an FIR filter, an LMS (Least Mean Square) algorithm, an RLS (Recursive Least Square) algorithm, a block adaptation algorithm, or the like can be applied as an adaptive algorithm.

  The control determination unit 17 has a function of controlling the drive unit 18 and a function of determining the presence or absence of fluid leakage from the pipe 2 based on the error signal e (t) output from the subtraction unit 162. Have. Although the details of the determination method will be described later, by using the temperature compensation pressure at each time point, that is, the error signal e (t), it is possible to determine the variation due to temperature in the pressure change by the true pressure change after removal. It is like that. The presence / absence of the leakage determined by the control determination unit 17 or the result of the leakage is output to the display unit 19.

  The drive unit 18 has a function of driving the linear actuator 13 based on a control signal from the control determination unit 17. The display unit 19 has a function of displaying the result on a display or the like and notifying the user based on the presence or absence of the leakage determined by the control determination unit 17 or the result of the degree. Note that as a means for notifying the user, instead of (or in addition to) displaying on a display or the like, sound may be performed using a speaker or the like. The same applies to the following examples.

  Next, a general pressure-type leakage inspection method when the fluid is a gas will be described first.

FIG. 2 is a diagram for explaining an equation of state of the gas filled in the pipe 2 and schematically shows the state. The pipe 2 is filled with a gas having a pressure P, a volume V ₀ , a mass M, a molecular weight m, and a temperature T. In addition, a gas having an inflow mass flow rate G (t) (kg / s) flows into the pipe 2, and a leakage flow rate Q (m ³ / s) and a leakage density ρ (kg / m ³ ) from the pipe 2. Gas is leaking.

  In this case, the equation of state of the gas filled in the pipe 2 is represented by the following equation (1). Here, R represents a gas constant.

When the equation (1) is differentiated with respect to time t, the time change is represented by the following equation (2). Moreover, when both sides of the formula (2) are divided by the formula (1), the following formula (3) is obtained. Furthermore, if the time change of pressure P, mass M, and temperature T is small and the secondary minute term can be ignored, the following equation (4) is obtained. The initial pressure P ₀ , the initial mass M ₀ , and the initial temperature T ₀ each represent values in the initial state (time t = 0).

  Here, as described above, since there is an inflow and leakage of gas in the pipe 2, the mass M of the gas in the pipe 2 can be expressed by the following equation (5). Further, when the gas leakage is very small, the leakage flow rate Q can be approximated by a Poiseuille flow. In this case, as shown in FIG. 3, when the pressure in the pipe 2 is P and the atmospheric pressure (external pressure) is Patm, the leakage flow rate Q is proportional to the pressure difference ΔP as shown in the following equation (6). . Here, the pressure difference ΔP = P−Patm (gauge pressure), ΔL is the thickness of the pipe wall of the pipe 2, a is the equivalent radius of the portion where the gas is leaking, and μ is the viscosity coefficient of the gas. The actual leak hole is neither a circular cross section nor perpendicular to the wall, but the leak flow rate Q can be equivalently described as in equation (6).

Next, when Expression (5) and Expression (6) are substituted into Expression (4), the following Expression (7) is obtained. Also, ([rho / M ₀₎ is ≒ (1 / V _0), the ^{(πa 4 / 8μΔL) = k} ( leakage coefficient) to define, can be expressed as the following equation (8). Further, since the atmospheric pressure Patm is a constant, (dP / dt) = (d / dt) · ΔP, and therefore, when the pressure P in the equation (8) is described by the pressure difference ΔP, the following equation (9 ). Here, P ₀ is an initial pressure expressed in absolute pressure.

  This equation (9) is a basic equation used in the pressure type leakage inspection method, and generally, the presence or absence of gas leakage is determined by the following steps S11 to S13.

  Step S11: The inflow mass flow rate G (t) is caused to flow into the pipe 2 to increase the gauge pressure ΔP of the gas in the pipe 2 (set (dΔP / dt)> 0) (pressurization step).

  Step S12: The pipe 2 is closed (inflow mass flow rate G (t) = 0).

  Step S13: The pressure drop (value of (dΔP / dt) in the case of (dΔP / dt) <0) is observed to determine the presence or absence of gas leakage or its extent. This is because, in the equation (9), when there is gas leakage (leakage coefficient k ≠ 0), the second term causes the pressure difference ΔP in the pipe 2 to drop.

In this way, a pressure-type leak test can be performed using equation (9). However, when the inflow mass flow rate G (t) = 0, in addition to the second term (− (k / V ₀ ) · ΔP), the right side of the equation (9) is the third variation that is caused by temperature. The term ((1 / T) · (dT / dt)) exists. Therefore, when the value of k is obtained without considering the variation due to temperature as in step S13, an error occurs and the accuracy of the leakage inspection deteriorates. Further, when the value of the third term is larger than that of the second term, no pressure drop occurs ((dΔP / dt)> 0), and there is a possibility that gas leakage may be missed. Therefore, if the third term in the equation (9) can be appropriately obtained and removed, a leakage inspection considering the temperature-induced variation can be performed, and the inspection accuracy is improved. In the leakage inspection method of the present embodiment, the above-described adaptive estimation unit 161 and subtraction unit 162 adaptively estimate and remove the temperature-induced pressure component in the measured pressure at each time point, so that in the equation (9) The third term is appropriately obtained and removed.

  Next, the leakage inspection method of the present embodiment will be described focusing on a characteristic part, that is, a method of adaptively estimating and removing a temperature-induced pressure component in the measured pressure at each time point.

  Step S21: As in step S11 described above, the inflow mass flow rate G (t) is caused to flow into the pipe 2 to increase the gas gauge pressure ΔP in the pipe 2 (pressurization step). Specifically, the linear actuator 13 drives the air cylinder 11 and the piston 12 to cause the inflow flow rate G (t) to flow into the pipe 2, thereby increasing the gauge pressure ΔP.

Here, the inflow mass flow rate G (t) (kg / s) is expressed by the following equation (4) where the gas density is ρ (kg / m ³ ) and the inflow volume flow rate is V (t) (m ³ / s). 10).

    G (t) = ρ · V (t) (10)

However, the amount of gas inflow is very small with respect to the volume of the gas in the pipe 2, and the change in the density ρ of the gas can be ignored. At this time, the inflow mass flow rate G (t) is assumed to change gradually to such an extent that the temperature of the gas in the pipe 2 can be considered constant at each time point. In other words, the inflow mass flow rate G (t) is set so that the compression and expansion of the gas in the pipe 2 can be regarded as an isothermal change. In the case of the present embodiment, for example, if the displacement and effective cross-sectional area of the air cylinder 11 are L (t) = ΔL · sin (2πf ₀ t) and S, respectively, The mass flow rate G (t) can be expressed as the following formula (11).

G (t) = ρ · S · (dL (t) / dt)
= (2πf ₀ · ρSΔL) cos (2πf ₀ t) (11)

  Step S22: The pressure of the gas in the pipe 2 is measured by the pressure sensor 14, and at least one of the temperature of the fluid in the pipe 2, the temperature of the pipe wall of the pipe 2, and the temperature around the pipe 2 is measured by the temperature sensor 15. Measure one. Then, each of the pressure sensor 14 and the temperature sensor 15 outputs a pressure signal ΔP (t) and a temperature signal x (t) expressed in gauge pressure to the adaptive estimation unit 161.

  Step S23: The adaptive estimation unit 161 adaptively estimates the temperature-induced pressure component y (t) in the pressure signal ΔP (t) based on the pressure signal ΔP (t) and the temperature signal x (t). This temperature-induced pressure component y (t) is determined by the average temperature of the entire pipe 2, and measures at least one of the temperature of the fluid in the pipe 2, the temperature of the pipe wall of the pipe 2, and the temperature around the pipe 2. This is not the temperature signal x (t) itself, but is closely related. In other words, they are mutually coherent signals. Therefore, the adaptive estimation unit 161 outputs the estimated value y (t) of the temperature-induced pressure component based on the temperature signal x (t), and based on the error signal e (t) output from the subtraction unit 162. The estimated characteristic can be adaptively changed, and the temperature-induced pressure component y (t) can be adaptively estimated by the output of the adaptive estimation unit 161. Specifically, for example, the aforementioned FIR filter or the like outputs the estimated value y (t) of the temperature-induced pressure component, and for example, the aforementioned LMS algorithm or the like adaptively changes the estimated characteristic based on the error signal e (t). And the process of converging the error signal e (t) is executed.

  Here, an example when the adaptive estimation unit 161 is configured with an FIR filter will be described. First, when the temperature signal x (t) is described in a discrete time system, it can be expressed as the following expression (12) using an N-dimensional vector (N: a natural number of 2 or more).

  In this case, the temperature-induced pressure component y (t) and the error signal e (t) are expressed by the following equations (13) and (14).

Here, h _N ^(t) is an N-dimensional vector as shown in the following equation (15) and represents the impulse response of the FIR filter. Further, the subscript T in the equation (15) represents transposition of the vector.

The value of the impulse response h _N ^(t) is adaptively changed by an adaptive algorithm. Specifically, for example, in the case of the LMS algorithm, the value of the impulse response h _N ^(t) adaptively changes as shown in the following equation (16).

Here, the step gain α is a constant determined according to the nature of the input signal (in this case, the temperature signal x _N (t)). Therefore, it is determined to some extent from the experience side according to the specific adaptation situation. The initial value of the impulse response h _N ^(t) may be a normal zero vector. However, when the impulse response of the system is predicted to some extent, for example, when the impulse response of the filter under similar conditions is known, the initial value of the filter is used to shorten the time required for filter adaptation. Is preferably used.

In this way, when the adaptive estimation unit 161 is configured by the FIR filter and the LMS algorithm, the adaptive estimation unit 161 first estimates the temperature-induced pressure component from the temperature signal x _N (t) according to Equation (13). A value y (t) is determined. Then, in the subtracting unit 162, the error signal e (t) is obtained by Expression (14). Next, according to the equation (16), the impulse response h _N ^(t) is updated from the temperature signal x _N (t) and the obtained error signal e (t) to become an impulse response h _N ^{(t + 1)} . Then, by using the updated impulse response h _N ^{(t + 1)} , an estimated value (t) of the temperature-induced variation y is obtained again by Equation (13). In this way, the process of adaptively changing the estimation characteristic of the adaptive estimation unit 161 is repeated, so that the impulse response h _N ^(t) finally converges to a constant value. The error signal e (t) at this time is not only the “error signal” of the adaptive estimation unit 161 but also the temperature compensation pressure at each time point as described above. Therefore, by using this error signal e (t), it is possible to perform a leakage inspection based on the true pressure change after removing the temperature-induced variation in the pressure change.

  Step S24: Similar to step S13 described above, the pressure fluctuation is observed, and the presence or absence of gas leakage is determined, that is, the leakage inspection is performed. At this time, an error signal e (t) that is a temperature compensated pressure obtained by the adaptive estimation unit 161 and the subtraction unit 162 is used. The control determination unit 17 determines the presence or absence of this gas leakage or the extent thereof. In this embodiment, the phase difference between the error signal e (t) that is the temperature compensation pressure and the inflow mass flow rate G (t) in the equation (11) is used in this embodiment. When there is no leakage, these phase differences are 90 degrees, but when there is leakage, a phase shift proportional to the size of the leakage occurs. The result determined by the control determination unit 17 is displayed on the display or the like in the output unit 19. Thereby, the user can know the result of the leak test. This is the end of the leakage inspection method of the present embodiment.

  As described above, in the present embodiment, the adaptive estimation unit 161 is based on the pressure signal ΔP (t) of the gauge pressure output from the pressure sensor 14 and the temperature signal x (t) output from the temperature sensor 15. Thus, the temperature-induced pressure component y (t) occupying the pressure signal ΔP (t) is adaptively estimated, and the subtracting unit 162 subtracts this from the pressure signal ΔP (t) (temperature compensation pressure (error signal e (t))) Since the control determination unit 17 performs the leakage inspection of the pipe 2 based on the change in the temperature compensation pressure, for example, there is a temperature distribution in the fluid in the pipe 2 and it changes every moment. Even if it is a situation or the case where the thermal dynamics of the pipe 2 is unknown, the temperature-induced fluctuation in the fluid pressure change is reliably removed with high accuracy according to the situation change. be able to. Therefore, a highly accurate and highly reliable leak test can be performed.

  In addition, since the leakage inspection can be performed with high accuracy, the time and cost spent for the inspection can be greatly reduced. In particular, when the adaptive estimation unit 161 is configured by an LMS algorithm, the algorithm is simple, and thus a leak inspection system can be constructed using inexpensive and small-scale hardware.

  Furthermore, the adaptive estimation unit 161 can be configured by a general adaptive estimator and algorithm, and an optimal leakage inspection system can be constructed according to the conditions of the inspection target.

  In this embodiment, when the inflow mass flow G (t) and the temperature signal x (t) are uncorrelated, that is, in step S22, the pipe 2 is closed as in step S12 (inflow mass flow rate). G (t) = 0) is not necessary, and the case where the temperature-induced pressure component y (t) can be adaptively estimated while increasing or decreasing the pressure of the fluid in the pipe 2 has been described. If there is a correlation between the inflow mass flow G (t) and the temperature signal x (t), adaptive estimation may be performed after the piping 2 is closed as in step S12. Even when configured in this manner, the present embodiment and effects can be obtained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  In the first embodiment, an example of the leakage inspection method for the fluid filled in the pipe 2 has been described. In the present embodiment, the tank 5 having a larger volume than the pipe 2 is filled. An example of a leakage inspection method for fluid will be described. In order to simplify the description, the same parts as those in the first embodiment will be described below with the same reference numerals.

  FIG. 4 shows a schematic configuration of the leakage inspection system according to the present embodiment. This leakage inspection system includes a tank 5 to be inspected and a leakage inspection apparatus 4 that performs inspection.

  The tank 5 serves as a reservoir for storing fluids such as fuel gas and petroleum, and fills these fluids inside. The tank 5 has a valve 51 for closing the tank at a predetermined position.

  The leakage inspection apparatus 4 includes a pump 41, an electromagnetic valve 42, a pressure sensor 14, a plurality of temperature sensors 451 to 454, an adaptive estimation unit 461, a subtraction unit 162, a control determination unit 17, and a drive unit 48. And a display unit 19

  Here, the temperature sensors 451 to 454 in the present embodiment are a specific example of “temperature measuring means” in the present invention, and the adaptive estimation unit 461 is a specific example of “adaptive estimator” in the present invention. .

  The pump 41 is for flowing a fluid into the tank 5. The electromagnetic valve 42 is for closing the tank 5 during pressure measurement. That is, in the present embodiment, unlike the first embodiment, adaptive estimation is performed after the tank 5 is closed. The pump 41 and the electromagnetic valve 42 are driven by a driving unit 48 as will be described later.

  Similar to the temperature sensor 15 in the first embodiment, the temperature sensors 451 to 454 measure at least one of the temperature of the fluid in the tank 5, the temperature of the wall of the tank 5, and the temperature around the tank 5. Measure. The plurality of temperature sensors 451 to 454 are arranged at predetermined positions of the tank 5. Unlike the first embodiment, the plurality of temperature sensors 451 to 454 are arranged because the tank 5 in the present embodiment is larger than the pipe 2 in the first embodiment as described above. This is because the temperature may vary depending on the location. The temperatures (temperature signals x1 (t) to x4 (t)) measured by the temperature sensors 451 to 454 are output to the adaptive estimation unit 461 in the same manner as the temperature signal x (t) in the first embodiment. It is used when adaptively estimating the pressure fluctuation due to temperature.

  The drive unit 48 has a function of driving the pump 41 and the electromagnetic valve 42 based on a control signal from the control determination unit 17.

  The adaptive estimation unit 461 is based on the pressure signal ΔP (t) of the gauge pressure output from the pressure sensor 14 and the temperature signals x1 (t) to x4 (t) output from the plurality of temperature sensors 451 to 454, respectively. Thus, it has a function of adaptively estimating the temperature-induced pressure component y (t) in the pressure signal ΔP (t). Specifically, the estimated value y (t) of the temperature-induced pressure component is output based on the plurality of temperature signals x1 (t) to x4 (t), and the pressure signal ΔP (t) and the temperature-induced pressure component The estimation characteristic is adaptively changed based on the error signal e (t) that is a difference from the estimated value y (t), and the temperature-induced pressure component y (t) is adaptively changed by the output of the adaptive estimation unit 461. Estimated. Unlike the adaptive estimation unit 161 in the first embodiment, the tank 5 is estimated by the plurality of temperature signals x1 (t) to x4 (t) as described above in the first embodiment. This is because it is larger than the pipe 2 and may be subjected to different temperature fluctuations depending on the location. Also, various configurations can be applied to the configuration of the adaptive estimator and the configuration of the adaptive algorithm in the adaptive estimation unit 461 as in the case of the adaptive estimation unit 161. Note that the details of the adaptive estimation method are the same as in the case of the adaptive estimation unit 161, and a description thereof will be omitted.

  Here, the adaptive estimator 461 of the present embodiment is characterized by only the adaptive estimation of the temperature-induced pressure component y (t) and the temperature compensated pressure (error signal e (t)) based on it, and leakage. This is the point where a period during which no inspection is performed is provided. This takes into account that it may take a long time for the adaptive estimation unit 461 to converge depending on the statistical properties of temperature fluctuations, and so on. By performing the leakage inspection after estimating the dynamics, it is possible to greatly shorten the period during which the tank 5 is pressurized for the leakage inspection.

  As described above, in the present embodiment, since only the adaptive estimation of the temperature-induced pressure component y (t) and the temperature compensation pressure based on the temperature estimation pressure are obtained, and the period during which the leakage inspection is not performed is provided, the first In addition to the effects of the embodiment, the leakage inspection can be performed more efficiently.

  Although the present invention has been described with reference to the first and second embodiments, the present invention is not limited to these embodiments, and various modifications can be made.

  For example, in the above embodiment, the adaptive estimation method when the adaptive estimation units 161 and 461 are configured by the FIR filter and the LMS algorithm has been described. However, the adaptive estimation units 161 and 461 and the subtraction unit 162 are described. May be constructed with other adaptive estimators and algorithms as described above. Even in this case, it is possible to obtain the same effect as that of the above embodiment.

  Further, in the above-described embodiment, the adaptive estimation units 161 and 461 have been described with the temperature signal x (t) as an input and outputting the estimated value of the temperature-induced pressure component in the pressure signal ΔP (t). However, on the contrary, the adaptive estimation units 161 and 461 may be configured to receive the pressure signal ΔP (t) and output an estimated value of the temperature that is the cause signal, and further combine them. You may make it comprise. Even in these cases, the same effect as in the case of the above-described embodiment can be obtained.

  In the above embodiment, the case where the fluid filled in the pipe 2 or the tank 5 is a gas has been described. However, this fluid may be a liquid, and the present invention is illustrated in FIG. As shown in the leakage inspection system shown above, including a fluid in which gas and liquid Lq are mixed, a mixture of two or more phases of gas, liquid, or solid, and more It can also be applied to what you have. However, for example, when air and a gas-liquid two-phase substance are mixed in the tank 5, if the vapor pressure of the substance changes and the composition ratio of the gas in the tank 5 changes, the fluid in the container Will be affected. Thus, the influence of the composition ratio of the fluid may have to be taken into consideration. Further, for example, when the piping 2 or the tank 5 is deformed due to a change in external conditions such as the support state of the tank 5, the pressure of the fluid in the container is affected.

  Therefore, when the leakage inspection is performed in consideration of the change in the shape of the container and the change in the composition ratio of the fluid in the container as described above, for example, as in the leakage inspection system shown in FIG. In addition to the plurality of temperature sensors 451 to 453 described above, a strain sensor 655 that measures the shape change amount of the tank 7, a vapor pressure sensor 656 that measures the composition ratio of the fluid in the tank 7 based on the vapor pressure of the fluid, and the like. What is necessary is just to comprise so that it may arrange | position. Specifically, the adaptive estimation unit 661 in the leakage inspection apparatus 6 has a shape output from the strain sensor 655 in addition to the plurality of temperature signals x1 (t) to x3 (t) output from the temperature sensor 451. The temperature-induced pressure component y (t) may be adaptively estimated based on the variation signal x5 (t) and the vapor pressure signal x6 (t) output from the vapor pressure sensor. Even in this configuration, from the viewpoint of the configuration of the adaptive estimation unit 661 and the adaptive algorithm, only the number of dimensions in the vector of the signal input to the adaptive prediction unit 661 increases. In the embodiment, there is no difference in principle from the case where a plurality of temperature signals x1 (t) to x4 (t) are used, and the same effect as in the above embodiment can be obtained. Although both the strain sensor 655 and the vapor pressure sensor 656 are installed in FIG. 5, only one of them may be installed. Further, instead of (or in addition to) the vapor pressure sensor 5 shown in FIG. 5, a composition sensor that directly measures the composition ratio of the fluid in the tank 7 or a density that measures the composition ratio of the fluid by its density. You may comprise so that a sensor etc. may be arrange | positioned.

  In the above embodiment, the temperature-induced pressure component is adaptively estimated using the absolute pressure (pressure signal P (t)) or gauge pressure (pressure signal ΔP (t)) measured by the pressure sensor 14. Although the case has been described, for example, the reference container 8 is arranged separately from the tank 7 to be inspected as in the leakage inspection apparatus 6 shown in FIG. 5 and the pressure in the reference container 8 and the tank 7 A differential pressure sensor 64 that measures a differential pressure with respect to the pressure may be provided, and the differential pressure (pressure signal P ′ (t)) measured by the differential pressure sensor 64 may be used. In this leakage inspection device 6, first, the electromagnetic valves 43 and 43 are opened, and the tank 41 and the reference container 8 are pressurized by the pump 41 so as to have the same pressure. After that, the pressure difference between the pressure in the reference container 8 and the pressure in the tank 7 is measured by closing the electromagnetic valves 43 and 44. Here, since the ambient temperatures of the tank 7 and the reference container 8 are the same, the pressures of the fluids inside the tank 7 and the reference container 8 are affected by substantially the same temperature. Therefore, the effect of removing the temperature influence can be further enhanced by adopting a configuration in which the differential pressure between the pressure in the reference container 8 and the pressure in the tank 7 is measured in this way. Further, in the configuration of FIG. 5 for measuring such a differential pressure, since the temperature measurement range required for the differential pressure sensor 64 becomes small, a sensor with higher sensitivity (small resolution) can be used, and the tank Even slight pressure fluctuations within 5 can be detected. Furthermore, there is also an effect that it is not affected by atmospheric pressure fluctuation, which causes a problem in measurement by gauge pressure.

  As shown in FIG. 5, the fluid filled in the reference container 8 includes gas, liquid, or solid, including the mixture of gas and liquid Lq, as in the case of the tank 7. The two or more phases can be mixed. Further, the reference container 8 may be arranged in the tank 7. As in the case of the tank 7, various sensors such as the above-described temperature sensor, strain sensor, and vapor pressure sensor may be arranged at a predetermined position of the reference container 8. Furthermore, in the example shown in FIG. 5, the differential pressure between the pressure in the reference container 8 and the pressure in the tank 7 is directly measured by the differential pressure sensor 64, but the respective pressures are measured separately. The pressure may be obtained.

  In the present invention, the temperature of the fluid in the pipe 2 and the tank 5 measured by the temperature sensors 15 and 451 to 454, the temperature of the wall of the pipe 2 and the tank 5, or the temperature around the pipe 2 and the tank 5 are forced. It may be changed as desired. When the temperature is forcibly changed in this way, it is possible to add a temperature fluctuation having an optimum property to the adaptive algorithm to be used, and thus it is possible to further improve the efficiency and accuracy of the leakage inspection. .

  The leakage inspection method and leakage inspection apparatus of the present invention can be used in all industrial fields where leakage inspection is performed, such as fuel gas piping equipment, various pressure vessels, and quality inspection of industrial products.

1 is a schematic configuration diagram of a leakage inspection system according to a first embodiment of the present invention. It is a schematic diagram for demonstrating the equation of state of the gas with which it filled in piping. It is a schematic diagram for demonstrating the relationship between a leakage flow rate and a pressure. It is a schematic block diagram of the leakage inspection system which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram of the leakage inspection system which concerns on the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,4,6 ... Leak inspection apparatus, 11 ... Air cylinder, 12 ... Piston, 13 ... Linear actuator, 14 ... Pressure sensor, 15, 451-454 ... Temperature sensor, 161, 461, 661 ... Adaptive estimation part, 162 DESCRIPTION OF SYMBOLS ... Subtraction part, 17 ... Control determination part, 18, 48 ... Drive part, 19 ... Display part, 2 ... Pipe, 21, 51 ... Valve, 41 ... Pump, 42, 43 ... Electromagnetic valve, 5, 7 ... Tank, 64 ... Differential pressure sensor, 655 ... Strain sensor, 656 ... Vapor pressure sensor, 8 ... Reference container, P (t), ΔP (t) ... Pressure signal, x (t) ... Temperature signal, y (t) ... Temperature-induced pressure Component (estimated value), e (t) ... error signal (temperature compensation pressure), Lq ... liquid.

Claims (16)

A leakage inspection method for inspecting the presence or absence of fluid leakage from the container based on the pressure change when the fluid in the container is pressurized or decompressed,
Measuring the pressure of the fluid in the vessel to determine the measured pressure;
Measuring at least one of the temperature of the fluid in the container, the temperature of the container wall of the container, and the temperature around the container to obtain a measurement temperature;
An estimated value of the temperature-induced pressure component occupying the measured pressure is output based on the measured temperature, and an estimated characteristic is adaptively based on an error signal that is a difference between the measured pressure and the estimated value of the temperature-induced pressure component The temperature-induced pressure component is adaptively estimated by the output of the adaptive estimator to be changed,
By subtracting the temperature-induced pressure component from the measured pressure, a temperature compensation pressure is obtained,
Leakage inspection method for performing leakage inspection of the container based on a change in the temperature compensation pressure. Using digital filters and said adaptive estimator,
The leak inspection method according to claim 1, wherein the temperature-induced pressure component is adaptively estimated based on an output of the digital filter. The leakage inspection method according to claim 2, wherein the error signal is used as the temperature compensation pressure. The leakage inspection method according to claim 1, wherein a difference between a pressure of a fluid in a reference container filled with a fluid and a pressure of a fluid in the container is used as the measurement pressure. Measure the shape change amount of the container to further determine the measured shape change amount,
The leakage inspection method according to claim 1, wherein the adaptive estimator adaptively estimates the temperature-induced pressure fluctuation amount in consideration of the measurement shape change amount. Measuring the composition ratio of the fluid in the container to further determine the measured fluid composition ratio;
The leakage inspection method according to claim 1, wherein the adaptive estimator adaptively estimates the temperature-induced pressure fluctuation in consideration of the measurement fluid composition ratio. The leak inspection method according to claim 1, wherein only a time period during which the leak inspection is not performed is provided by performing only adaptive estimation of the temperature-induced pressure component and obtaining the temperature compensation pressure. The leak inspection method according to claim 1, wherein the temperature of the fluid in the container, the temperature of the container wall of the container, or the temperature around the container is forcibly changed. A leakage inspection device for inspecting the presence or absence of fluid leakage from the container based on the pressure change when the fluid in the container is pressurized or depressurized,
Pressure measuring means for measuring the pressure of the fluid in the container;
Temperature measuring means for measuring at least one of the temperature of the fluid in the container, the temperature of the container wall of the container, and the temperature around the container;
Based on the measured temperature measured by the temperature measuring means, the estimated value of the temperature-induced pressure component occupying the measured pressure measured by the pressure measuring means is output, and the estimated value of the measured pressure and the temperature-induced pressure component An adaptive estimator for adaptively estimating the temperature-induced pressure component by adaptively changing the estimation characteristics based on an error signal that is a difference between
Temperature compensation means for obtaining a temperature compensation pressure by subtracting a temperature-induced pressure component adaptively estimated by the output of the adaptive estimator from the measured pressure;
A leakage inspection apparatus comprising: inspection means for performing a leakage inspection of the container based on a change in temperature compensation pressure obtained by the temperature compensation means. The adaptive estimator is implemented with a digital filter, the leakage inspecting device according to claim 9, wherein the estimating the temperature caused pressure component adaptively by the output of the digital filter. The leak inspection apparatus according to claim 10, wherein the temperature compensation unit uses the error signal as the temperature compensation pressure. The leak test apparatus according to claim 9, wherein the pressure measuring unit measures a difference between a pressure of a fluid in a reference container filled with a fluid and a pressure of the fluid in the container. Further comprising a shape change amount measuring means for measuring the shape change amount of the container,
The leakage according to claim 9, wherein the adaptive estimator adaptively estimates the temperature-induced pressure fluctuation amount in consideration of the measured shape change amount measured by the shape change amount measuring unit. Inspection device. A composition ratio measuring means for measuring a composition ratio of the fluid in the container;
The leak test according to claim 9, wherein the adaptive estimator adaptively estimates the temperature-induced pressure fluctuation in consideration of a measurement fluid composition ratio measured by the composition ratio measurement means. apparatus. The period for performing only the adaptive estimation of the temperature-induced pressure component by the adaptive estimator and the temperature compensation pressure by the temperature compensation means and not performing the leak test is provided. Leakage inspection device described in 1. The leak inspection apparatus according to claim 9, further comprising temperature changing means for forcibly changing the temperature of the fluid in the container, the temperature of the container wall of the container, or the temperature around the container.

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