JP2014134999A - Valve diagnosis apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and accurately determine normality/abnormality of a valve.SOLUTION: Useless time Tdand delay time T86in a step response at an initial stage of valve operation are acquired and a ratio α(α=Td/T86) of the acquired useless time Tdto the delay time T86is set as a reference representative index value. Useless time Tdand delay time T86in a step response at diagnosis of the valve are acquired and a ratio α(α=Td/T86) of the acquired useless time Tdto the delay time T86is set as a diagnosis target index value. A relative error εRof the diagnosis target index value αto the reference representative index value αis calculated, and when the relative error εRexceeds a threshold εRth, abnormality of the valve is determined. It is also available to use a ratio of useless time Td to settling time Tss instead of a ratio of useless time Td to delay time T86.

Description

  The present invention relates to a valve diagnostic device for diagnosing normality / abnormality of a valve whose valve opening degree is controlled via a positioner.

  2. Description of the Related Art Conventionally, in a chemical plant or the like, a positioner is provided for a valve (control valve) used in the flow rate process, and the valve opening degree of the valve is controlled by this positioner.

  FIG. 10 shows a configuration of a valve diagnosis system (offline diagnosis system) in a system in which a positioner and a valve disclosed in Patent Document 1 are combined. In the figure, 101 is a positioner, 102 is a valve (control valve), 103 is an upper application, and the upper application 103 and the positioner 101 are connected via a communication line 104.

In this valve diagnosis system, the host application 103 includes a data analyzer, gives a step input to the positioner 101, and acquires data indicating the valve opening of the valve 102 that changes in response to the step input as a step response. calculates a total evaluation index _{Df O (Deviation from First Order Characteristic} ) from the step response.

The comprehensive evaluation index Df _O is inherently a step response of valve + positioner, defined as the response characteristics of the ideal is primary delay characteristic, how much the waveform of the measured step response, the response of the first-order lag is ideal This is a value calculated as to whether or not the waveform is distorted.

Specific calculation formula for total evaluation index Df _O, since it is described in Patent Document 1 is omitted here, the value of the total evaluation index Df _O is large, that is much away from the ideal waveform Therefore, the evaluation of response characteristics is low. Conversely, if the value of the total evaluation index Df _O is small, since much closer to the ideal waveform, the evaluation of the response characteristic is increased. In a valve diagnostic system shown in Patent Document 1 determines normal or abnormal valve 102 from the value of the total evaluation index Df _O.

JP 2003-308101 A

As described above, in the valve diagnosis system disclosed in Patent Document 1, an ideal response characteristic is defined as a first-order lag characteristic, and the comprehensive evaluation index Df _O is calculated from the acquired step response. However, in the actual plant is not necessarily the response characteristics of the ideal due to various factors such as the type of size and fluid valves, not always perform appropriate valve diagnostic just because using the comprehensive evaluation index Df _O. In addition, has a complex formula for calculating the comprehensive evaluation index Df _O, take the time to calculate the comprehensive evaluation index Df _O.

  In Patent Document 1, the dead time Td from the acquired step response (time until reaching 10% of the step width after step input), the time constant Tc (after step input, the step response is 63.2 of the step width). % Time (delay time T63)), settling time Tss (time until step response is within ± 1% of step width after step input), overshoot (overshoot amount with step width as full span) (Unit:% FS)), and determination of dynamic characteristic index values such as undershoot (undershoot amount (unit:% FS) with a step width as a full span).

  If dynamic characteristic index values such as dead time Td, time constant Tc, and settling time Tss obtained from this step response are used, it is possible to determine whether the valve 102 is normal or abnormal from the change in the dynamic characteristic index value. Conceivable. However, as described in Patent Document 1 (see the description in paragraph [0040]), there are many dynamic characteristic index values, and it is difficult to judge the validity of the evaluation of the dynamic characteristics. I don't know what to do. For example, even if the time constant Tc is out of the normal range, the dead time Td and the settling time Tss may be normal. Even if the dead time Td is out of the normal range, the time constant Tc and the settling time Tss are normal. Therefore, it is difficult to accurately determine whether the valve 102 is normal or abnormal only by looking at changes in one dynamic characteristic index value such as the dead time Td, the time constant Tc, and the settling time Tss.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a valve diagnostic apparatus that can easily and accurately determine whether a valve is normal or abnormal. .

  In order to achieve such an object, the valve diagnostic apparatus according to the present invention provides a step input to the positioner in the valve diagnostic apparatus for diagnosing normality of a valve whose valve opening degree is controlled via the positioner, Step response acquisition means for acquiring data indicating the valve opening degree of the valve that changes in response to the step input as a step response, and representative index values representing a plurality of dynamic characteristic index values obtained from the acquired step responses. Representative index value calculation means to be obtained, reference representative index value storage means for storing the representative index value obtained in the normal operation state of the valve as a reference representative index value, and diagnosis of the representative index value obtained in the diagnosis operation state of the valve The target index value is compared with the diagnostic target index value and the reference representative index value, and the normal / abnormal judgment is performed based on the comparison result. Characterized in that it comprises a means.

  In this invention, the step response acquisition means gives a step input to the positioner and acquires data indicating the valve opening of the valve that changes in response to the step input as a step response. The representative index value calculating means obtains a representative index value representing a plurality of dynamic characteristic index values obtained from the acquired step response. For example, a ratio (Td / T86) between the dead time Td obtained from the acquired step response and the delay time T86 (time until the step response reaches 86.5% of the step width after step input) is a ratio type index value. This ratio type index value (Td / T86) is used as a representative index value, or the dead time Td and settling time Tss obtained from the acquired step response (after step input, the step response is within ± 1% of the step width) The ratio (Td / Tss) with respect to the time to become is determined as a ratio index value, and the ratio index value (Td / Tss) is used as a representative index value. A plurality of dynamic characteristic index values obtained from the acquired step response may be vectorized, and the sum (vector sum) of the vectorized dynamic characteristic index values may be used as a representative index value. That is, in the present invention, a representative index value is obtained as an index value obtained by integrating a plurality of dynamic characteristic index values obtained from a step response, and the movement of the entire waveform of the step response is expressed by this representative index value.

  In the present invention, the representative index value obtained in the normal operation state of the valve is stored as the reference representative index value, and the representative index value obtained in the diagnosis operation state of the valve is used as the diagnosis target index value. The target index value and the reference representative index value are compared, and normality / abnormality of the valve is determined based on the comparison result. For example, the representative index value at the initial operation of the valve is set as the reference representative index value, and each time the valve diagnosis operation (step response inspection) is performed, the relative error of the diagnosis target index value with respect to the reference representative index value is obtained. When a predetermined threshold value is exceeded, it is determined that the valve is abnormal.

  According to the present invention, the representative index value representing the movement of the entire waveform of the step response is used, and the representative index value obtained in the normal operation state of the valve is set as the reference representative index value. And the representative index value (diagnostic target index value) obtained in the diagnostic operation state of the valve, the change in the waveform of the step response is surely captured, and the normality of the valve can be judged easily and accurately. Can be done.

It is a figure which shows the principal part of the valve diagnostic system (offline diagnostic system) using one Embodiment of the valve diagnostic apparatus which concerns on this invention. It is a flowchart which shows operation | movement at the time of the operation | movement initial stage of the valve | bulb performed by the apparatus management system in this valve diagnostic system. It is a figure which illustrates the step input to the positioner in this valve diagnostic system, and the step response obtained from a valve. It is a flowchart which shows the operation | movement at the time of the offline diagnosis of the valve | bulb performed with an apparatus management system. It is a figure which shows the tolerance | permissible_range of the relative error of the diagnostic object index value with respect to a reference | standard representative index value. It is a functional block diagram of the principal part of an apparatus management system. It is a figure which shows the dead time Td in step response, delay time T63, T86, T98, settling time Tss, overshoot, and undershoot. It is a figure which shows the contents of dead time Td, delay time T63, T86, T98, settling time Tss, overshoot, and undershoot. It is a figure which shows the example which sent the opening degree setting signal (step input of several steps) which changes in steps from an apparatus management system as an execution command of a step response inspection. It is a figure which shows the structure of the valve | bulb diagnostic system (offline diagnostic system) in the system which combined the positioner and valve | bulb shown by patent document 1. FIG.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a main part of a valve diagnosis system (offline diagnosis system) using an embodiment of a valve diagnosis apparatus according to the present invention.

  In FIG. 1, 1 is a positioner, 2 is a valve (control valve), 3 is a device management system, 4 is a controller, and the device management system 3 and the controller 4 are connected via a bidirectional communication line 5. 4 and the positioner 1 are connected to each other through a two-line transmission line 6 of 4 to 20 mA.

  In this valve diagnosis system, the device management system 3 is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with these hardware. It has a valve diagnosis function. This equipment management system 3 corresponds to the valve diagnostic device referred to in the present invention.

[Initial operation of valve]
FIG. 2 is a flowchart showing the initial operation of the valve 2 performed in the device management system 3. The equipment management system 3 sends an execution instruction for the step response inspection to the controller 4 in accordance with an instruction from the operator at the beginning of the operation of the valve 2, that is, at the beginning of the operation of the plant in which the valve 2 is installed (step S101). In this example, as the simplest example, it is assumed that an opening setting signal (step input of one step) from 0% to 75% for the valve 2 is sent to the controller 4 as a step response inspection execution command (SP).

  The controller 4 receives the step input from the device management system 3, converts the received step input into a current signal of 4 to 20 mA, and sends it to the positioner 1. The positioner 1 converts the step input sent as a current signal of 4 to 20 mA into an air pressure signal, and gives the converted air pressure signal to the operating device 2-1 of the valve 2. Control. During the control of the valve opening, the valve opening (actual opening) of the valve 2 is fed back to the positioner 1. Thereby, in the positioner 1, data indicating the valve opening degree of the valve 2 that changes in response to the step input is obtained as the step response.

  FIG. 3 shows the step input to the positioner 1 and the step response obtained from the valve 2. A stepped waveform I (recording time (horizontal axis) −input signal (SP value [%]) (vertical axis)) shown in FIG. 3 is a step input, and the waveform changes with a delay from the waveform I. II (recording time (horizontal axis) −valve opening (PV value [%]) (vertical axis)) is the step response.

  The positioner 1 has a dead time Td from the step response obtained from the valve 2 (time until reaching 10% of the step width after the step input) and a delay time T86 (after the step input, the step response has a step width of 86. Time to reach 5%) and settling time Tss (time until step response is within ± 1% of step width after step input) are acquired as dynamic characteristic index values, and the acquired dynamic characteristic index The values (Td, T86, Tss), step input and step response data are sent to the controller 4 as inspection result data. The inspection result data is transmitted to the controller 4 by HART (Highway Addressable Remote Transducer) communication. The controller 4 sends the inspection result data sent from the positioner 1 to the device management system 3.

Device management system 3 takes in the inspection result data sent from the controller 4 (step S102), obtains the dead time Td from the inspection result data as an initial dead time Td ₀ (step S103), the delay time T86 Obtained as the initial delay time T86 ₀ (step S104), and the ratio between the obtained initial dead time Td ₀ and the delay time T86 ₀ is obtained as α ₀ = Td ₀ / T86 ₀ (step S105). The ratio α ₀ is stored in the memory M1 as a reference representative index value (step S106).

That is, the device management system 3 can obtain the ratio type index value α ₀ obtained as the ratio Td ₀ / T86 ₀ between the dead time Td _{0 at the} beginning of the operation of the valve 2 and the delay time T86 _{0 in} the normal operation state of the valve 2. The representative index value obtained in the normal operation state is stored in the memory M1 as the reference representative index value. The device management system 3 stores the inspection result data sent from the controller 4 in the CSV file format as the inspection result history.

[Valve offline diagnosis]
FIG. 4 is a flowchart showing an operation at the time of offline diagnosis of the valve 2 performed in the device management system 3. The device management system 3 sends an execution command for step response inspection to the controller 4 in accordance with an instruction from the operator during offline diagnosis of the valve 2 (step S201). Also in this example, as the simplest example, an opening setting signal (step input of one step) from 0% to 75% for the valve 2 is sent to the controller 4 as a step response inspection execution command (SP). .

  The controller 4 receives the step input from the device management system 3, converts the received step input into a current signal of 4 to 20 mA, and sends it to the positioner 1. The positioner 1 converts the step input sent as a current signal of 4 to 20 mA into an air pressure signal, and gives the converted air pressure signal to the operating device 2-1 of the valve 2. Control. During the control of the valve opening, the valve opening (actual opening) of the valve 2 is fed back to the positioner 1. Thereby, in the positioner 1, data indicating the valve opening degree of the valve 2 that changes in response to the step input is obtained as the step response.

  The positioner 1 obtains the dead time Td, the delay time T86, and the settling time Tss as dynamic characteristic index values from the step response obtained from the valve 2, and the obtained dynamic characteristic index values (Td, T86, Tss) and step inputs and The step response data is sent to the controller 4 as inspection result data. The controller 4 sends the inspection result data sent from the positioner 1 to the device management system 3.

The device management system 3 takes in the inspection result data sent from the controller 4 (step S202), acquires the dead time Td from this inspection result data as the dead time Td _N at the time of the current diagnosis (step S203), and the delay time. T86 is acquired as a delay time T86 _N at the time of the current diagnosis (step S204), and a ratio between the acquired dead time Td _N and delay time T86 _N at the time of the current diagnosis is obtained as α _N = Td _N / T86 _N (step S204). S205). That is, the ratio type index value α _N obtained as the ratio Td _N / T86 _N between the dead time Td _N and the delay time T86 _N at the time of the current diagnosis of the valve 2 is the representative index obtained at the current diagnosis operation state of the valve 2. The representative index value obtained in this diagnostic operation state is set as the diagnosis target index value.

The device management system 3 reads the reference representative index value (representative index value obtained in the normal operation state) α ₀ stored in the memory M1 (step S206), and the diagnosis target index value (step S205) calculating the relative error .epsilon.R _N relative to the reference representative index value alpha ₀ of the current representative index values obtained in the diagnostic operating state) alpha _N (step S207). In this example, the relative error εR _N is calculated as εR _N = | (α _N × 100 / α ₀ ) −100 |, but is calculated as εR _N = | α _N −α ₀ | / α ₀ ). Also good.

The device management system 3 compares the threshold IpushironRth which is predetermined relative error .epsilon.R _N calculated in step S207, if the relative error .epsilon.R _N exceeds the threshold IpushironRth (step S208 YES), the valve 2 is determined to be abnormal (step S209), if the relative error .epsilon.R _N does not exceed the threshold IpushironRth (NO in step S208), the valve 2 is determined to be normal (step S210).

In this embodiment, there is a threshold εRth to 20% of relative error .epsilon.R _N. Therefore, in this embodiment, as shown in FIG. 5, if the relative error in the positive / negative direction of the diagnosis target index value α _N with respect to the reference representative index value α ₀ is within ± 20% (allowable range). The valve 2 is determined to be normal, and if it is outside the ± 20% range (allowable range), the valve 2 is determined to be abnormal. In addition, the allowable range of the relative error is not limited to ± 20%, but may be + 20% only, −20% only, or the like.

As described above, in this embodiment, the dead time Td ₀ and the delay time T86 ₀ are obtained from the step response at the beginning of the operation of the valve 2, and the ratio α ₀ between the dead time Td ₀ and the delay time T86 ₀ is obtained. It is stored as a reference representative index value, and the ratio α _N between the dead time Td _N and the delay time T86 _N obtained in the diagnostic operation state of the valve 2 is used as the diagnosis target index value, and this diagnosis target index value α _N and the reference Whether the valve 2 is normal or abnormal is determined based on the comparison result with the representative index value α ₀ .

In this normal / abnormal judgment operation of the valve 2, the ratio-type index value obtained as α = Td / T86 is an index value obtained by integrating a plurality of dynamic characteristic index values obtained from the step response, and the entire waveform of the step response is calculated. It expresses movement. In the present embodiment, the ratio type index value α representing the movement of the entire waveform of the step response is used as the representative index value, and the representative index value α ₀ obtained from the step response at the initial operation of the valve 2 is used. (Representative index value α ₀ obtained in the normal state of the valve 2) is used as a reference representative index value, and the representative representative index value α ₀ and the representative index value (diagnosis target index value) α obtained in the diagnostic operation state of the valve By comparing with _N , the change in the waveform of the step response is surely captured, and whether the valve 2 is normal or abnormal can be determined easily and accurately.

FIG. 6 shows a functional block diagram of the main part of the device management system 3. The device management system 3 gives a step input to the positioner 1 via the controller 4, and acquires a step response acquisition unit 3-1 that acquires data indicating the valve opening of the valve 2 that changes in response to the step input as a step response. A representative index value calculation unit 3-2 for obtaining a ratio-type index value α = Td / T86 as a representative index value representing a plurality of dynamic characteristic index values obtained from the acquired step response, and an initial operation of the valve 2 A representative index value storage unit 3-3 that stores a representative index value (representative index value obtained in a normal operation state) α ₀ as a reference representative index value, and a representative index value α obtained in a diagnostic operation state of the valve 2 _N is a diagnosis target index value, the diagnosis target index value α _N is compared with the reference representative index value α ₀ stored in the reference representative index value storage unit 3-3, and the valve 2 is determined based on the comparison result. normal And a normal or abnormal determining unit 3-4 determines normal.

  In the above-described embodiment, the ratio α (α = Td / T86) between the dead time Td and the delay time T86 is used as the representative index value. However, the ratio β of the dead time Td and the settling time Tss ( β = Td / Tss) may be used as the representative index value.

  In the above-described embodiment, the dead time Td, the delay time T86, and the settling time Tss are acquired as the dynamic characteristic index values from the step response obtained from the valve 2, but the delay time T63 (time constant Tc) is obtained. The delay time T98, overshoot (% FS), undershoot (% FS), and the like may also be acquired as dynamic characteristic index values. FIG. 7 shows dead time Td, delay times T63, T86, T98, settling time Tss, overshoot, and undershoot in step response, and FIG. 8 shows dead time Td, delay times T63, T86, T98, settling time Tss, overshoot. Shows the contents of the shoot and undershoot.

  When the dead time Td, delay times T63, T86, T98, settling time Tss, overshoot, undershoot, etc. are acquired as dynamic characteristic index values, the ratio γ (γ = Td) between the dead time Td and the delay time T98. / T98) is used as the representative index value, or the ratio σ (σ = Tss / T86) of the settling time Tss and the delay time T86 is used as the representative index value. There are various possibilities. Also, a plurality of obtained dynamic characteristic index values may be vectorized, and the sum (vector sum) of the vectorized dynamic characteristic index values may be used as the representative index value.

  In the above-described embodiment, the dynamic characteristic index values (Td, T86, Tss) obtained from the step response and the step input and step response data are used as inspection result data from the positioner 1 via the controller 4 to the device management system 3. However, only the dynamic characteristic index values (Td, T86, Tss) obtained from the step response may be sent to the device management system 3. Further, instead of obtaining the dynamic characteristic index values (Td, T86, Tss) in the positioner 1, the dynamic characteristic index values (Td, T86, Tss) are obtained from the step response data sent in the device management system 3. It may be.

  In the above-described embodiment, the device management system 3 has the valve diagnosis function. However, the controller 4 may have the valve diagnosis function, and the positioner 1 may have the valve diagnosis function. It may be. When the controller 4 is provided with a valve diagnosis function, the controller 4 is equipped with the valve diagnosis device referred to in the present invention. When the positioner 1 is provided with a valve diagnosis function, the valve diagnosis device according to the present invention is mounted on the positioner 1.

In the embodiment described above, as the simplest example, the opening setting signal from 0% to 75% (step input of one step) is used as the execution instruction of the step response inspection, but as shown in FIG. An opening setting signal (step input of a plurality of steps) that changes stepwise may be used as an execution command for the step response inspection. In this case, for example, each time the diagnostic operation (step response inspection) of the valve 2 is performed, the index value α _N = Td _N / T86 _N of each step is obtained, and the reference representative index value α ₀ = Td _{0 of} each step. / T86 calculated relative error .epsilon.R _N for _0, relative error .epsilon.R _N is at every step does not exceed the IpushironRth, so as to determine that the normal valve 2.

In the above-described embodiment, the ratio α ₀ between the dead time Td _{0 at the} beginning of the operation of the valve 2 and the delay time T86 ₀ is stored as the reference representative index value. However, the representative index value calculation unit 3-2 The representative index value obtained in the normal operation state of the valve 2 is selected from the representative index values α _N obtained by the above, and the average value of the selected representative index values α _N is selected as the reference representative index. You may make it memorize | store as value (alpha) ₀ .

  In the above-described embodiment, the positioner 1 is integrated with the valve 2, but may be a separate positioner. Further, communication between the positioner 1 and the controller 4 is not limited to HART communication, but may be fieldbus communication or the like.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Positioner, 2 ... Valve (control valve), 2-1 ... Operation device, 3 ... Equipment management system, 3-1 ... Step response acquisition part, 3-2 ... Representative index value calculation part, 3-3 ... Reference | standard representative Index value storage unit, 3-4 ... normal / abnormal judgment unit, 4 ... controller, 5 ... communication line, 6 ... transmission path.

Claims (7)

In a valve diagnostic device for diagnosing normality of a valve whose valve opening degree is controlled via a positioner,
Step response acquisition means for giving a step input to the positioner and acquiring data indicating the valve opening of the valve that changes in response to the step input as a step response;
Representative index value calculating means for obtaining a representative index value representing a plurality of dynamic characteristic index values obtained from the acquired step response;
Reference representative index value storage means for storing the representative index value obtained in a normal operation state of the valve as a reference representative index value;
The representative index value obtained in the diagnostic operation state of the valve is used as a diagnostic target index value, the diagnostic target index value is compared with the reference representative index value, and normality / abnormality of the valve is determined based on the comparison result. And a normal / abnormal judgment means. The valve diagnostic device according to claim 1,
The representative index value calculation means includes:
A valve-type diagnostic apparatus characterized in that a ratio-type index value obtained by combining predetermined operating characteristic index values among a plurality of dynamic characteristic index values obtained from the step response and determining a ratio thereof is determined as the representative index value. In the valve diagnostic device according to claim 1 or 2,
The reference representative index value storage means includes
The valve diagnostic apparatus characterized in that the representative index value at the time of operation of the valve is stored as a reference representative index value. In the valve diagnostic device according to claim 1 or 2,
The reference representative index value storage means includes
Storing, as a reference representative index value, an average value of a plurality of representative index values selected as a representative index value obtained in a normal operation state of the valve among the representative index values obtained by the representative index value calculating means. A characteristic valve diagnostic device. In the valve diagnostic device according to any one of claims 1 to 4,
The normal / abnormal judgment means comprises:
A valve diagnosis device characterized by obtaining a relative error of the diagnosis target index value with respect to the reference representative index value, and determining that the valve is abnormal when the relative error exceeds a predetermined threshold value. In the valve diagnostic apparatus according to any one of claims 1 to 5,
The representative index value calculation means includes:
Td / T86, which is the ratio between the dead time Td obtained from the step response and the time T86 until the step response reaches 86.5% of the step width after giving the step input, is used as the representative index value. What is required is a valve diagnostic device. In the valve diagnostic apparatus according to any one of claims 1 to 5,
The representative index value calculation means includes:
Td / Tss, which is a ratio between the dead time Td obtained from the step response and the settling time Tss until the step response is within ± 1% of the step width after giving the step input, is the representative index value. A valve diagnostic device characterized by obtaining as follows.

Images