JP2007094794A - Control loop diagnostic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a control loop diagnostic device which eliminates subjective factors and enables identification of the factors, when a control loop is not sound by data based on an objective event. <P>SOLUTION: A control loop diagnostic device performs control operation using a measurement signal of flow rate of the measurement fluid by inserting a control valve in a duct in which the measurement fluid flows, and performs diagnosis of the soundness of the control loop which controls the control valve by the control signal obtained by the operation. This device is provided with an input process means to acquire and hold the measurement signal, the control signal and the signal of open degree of the control valve as monitoring data; and a change trend monitoring means which reads the monitoring data from this input process means, and monitors combination of patterns of the change trend of each monitoring data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a sound control loop in which a control valve is inserted into a conduit through which a measurement fluid flows, a control calculation is performed using a measurement signal of the flow rate of the measurement fluid, and the control valve is controlled by the control signal obtained by the calculation. The present invention relates to a control loop diagnostic apparatus for diagnosing sex.

  Patent Document 1 discloses a technique for diagnosing the soundness of a control loop from the behavior of a change in measured value by forcibly opening and closing a control valve inserted in a pipe line through which a measurement fluid flows. The present invention relates to a control loop diagnosis apparatus that diagnoses the soundness of a control loop while maintaining a normal control state.

  FIG. 3 is a functional block diagram illustrating a configuration example of a control system to which a conventional control loop diagnosis apparatus is applied. A indicates a field area, and B indicates a control system area. In the field area A, 1 is a conduit through which the fluid F flows, 2 is a control valve inserted into the conduit, and 3 is a transmitter also inserted into the conduit.

  In region B of the control system, reference numeral 4 denotes a controller, which inputs the measurement signal PV and the set value SV from the transmitter 3, outputs the control signal MV obtained by calculating the deviation to the control valve 2, and the flow rate of the fluid F Is set to the set value SV.

  Reference numeral 5 denotes a control loop diagnosis device that diagnoses the soundness of the control loop. In this control loop diagnostic apparatus, 51 is an input processing means, which acquires an alarm signal AL and a control mode signal MD as monitoring data from the measurement signal PV, the set value SV, the control signal MV and the controller 4.

  Based on the acquired monitoring data, the input processing means 51 calculates the tracking characteristics of the MV and PV with respect to the SV, the amplitude of the PV, the alarm occurrence status of the acquired data, the time ratio when the automatic control state is released, etc. at regular intervals, It is held in the monitoring data holding means 52.

  Reference numeral 53 denotes benchmark data holding means set in advance by the user. 54 is a performance measuring means for measuring the achievement level of the monitoring data held in the monitoring data holding means 52 with respect to the benchmark held in the benchmark data holding means 53.

  Reference numeral 55 denotes a diagnosis unit which acquires measurement data from the performance measurement unit 54, evaluates and diagnoses the control loop soundness and process problems based on a predetermined algorithm, and notifies the user.

JP 2002-076807 A

The conventional control loop diagnostic apparatus has the following problems.
(1) In the control loop, it is important to grasp the operating conditions of the controller and the control valve, which are the two elements having the adjustment function, but in the analog instrumentation, the behavior of the control valve is reflected as the adjustment result. It can be measured only as a measurement signal PV.

  For this reason, it is difficult to specify whether the cause when the control loop is not healthy is due to insufficient adjustment or malfunction of the control valve or due to the process. Of course, the details are not specified, and these are specified through on-site maintenance.

(2) The index that evaluates the soundness of the control loop is the degree of achievement with respect to the benchmark. Since the setting of this benchmark varies greatly depending on the subjective factors of the user, the objectivity of the diagnosis result becomes low, and the general control loop It cannot be a diagnostic device.

  The present invention has been made in order to solve the above-described problems, and eliminates subjective factors and makes it possible to identify factors when the control loop is not healthy by data based on objective events. The object is to realize a loop diagnosis device.

In order to achieve such a subject, the present invention has the following configuration.
(1) The soundness of a control loop in which a control valve is inserted into a pipe line through which the measurement fluid flows, the control calculation is performed using the measurement signal of the flow rate of the measurement fluid, and the control valve is controlled by the control signal obtained by the calculation In a control loop diagnostic device for diagnosing
Input processing means for acquiring and holding the measurement signal, the control signal and the opening signal of the control valve as monitoring data;
Change trend monitoring means for reading out the monitoring data from the input processing means and monitoring a combination of change tendency patterns of each monitoring data;
A control loop diagnosis apparatus comprising:

(2) The control trend diagnosis according to (1), wherein the change trend monitoring unit classifies each monitoring data into a change trend pattern of any one of ascending, descending, hunting, and no change. apparatus.

(3) an abnormal pattern holding unit that sets and holds an abnormal pattern of a control loop assumed in correspondence with a combination of patterns of change tendency of the monitoring data;
Diagnosis that outputs and holds abnormality diagnosis information together with time information when the abnormality pattern held in the abnormality pattern holding means matches the change tendency pattern of each monitoring data monitored by the change tendency monitoring means Means,
The control loop diagnostic apparatus according to (1) or (2), further comprising:

(4) The control loop diagnostic apparatus according to (3), further comprising diagnostic result notification means for displaying or sending diagnostic information held in the diagnostic means to a network.

As is apparent from the above description, the present invention has the following effects.
(1) When the control loop is not healthy, it is possible to objectively diagnose whether the cause is due to insufficient adjustment or malfunction of the control valve or due to a process factor.

(2) Moreover, since it becomes possible to specify the detailed part of the problem part, the maintenance work in the field performed so far is reduced, and the productivity improvement of a plant operation is anticipated.

(3) Since the diagnostic information has objectivity, it is possible to pass this information to a higher-level system and construct a medium- to long-term management system for plant equipment.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of a control system to which a control loop diagnosis apparatus of the present invention is applied. The same elements as those of the conventional apparatus described with reference to FIG. Hereinafter, the characteristic part of the present invention will be described.

  In FIG. 1, reference numeral 100 denotes a control loop diagnosis apparatus that forms a feature of the present invention. In this control loop diagnostic apparatus, 101 is an input processing means for monitoring the measurement signal PV transmitted from the transmitter 3, the control signal MV output from the controller 4, and the opening signal RV transmitted from the control valve 2. The data is acquired at regular intervals and stored in the monitoring data holding means 102.

  Reference numeral 103 denotes a change trend monitoring unit, which periodically accesses the monitoring data holding unit 102, classifies each monitoring data into a tendency of ascending, descending, hunting, and no change, and monitors a combination pattern thereof.

  Reference numeral 104 denotes an abnormal pattern holding unit, in which abnormal pattern information predicted by a combination of change patterns of monitoring data and factor information predicted by the pattern are set and held in advance by the user.

  Reference numeral 105 denotes a diagnosis unit, which inquires the abnormal pattern holding unit 104 for a combination pattern of change trends of each monitoring data monitored by the change trend monitoring unit 103. If there is a matching pattern, the abnormal pattern and its pattern Is stored in the diagnostic information holding means 106 together with the time information.

  107 is a diagnostic result notifying means, which displays the abnormal pattern stored in the diagnostic information holding means 106 and its occurrence time, and the factor information expected by the abnormal pattern preset and stored in accordance with a request from the user. Or notify the user with warnings, warnings and electronic mails via the network.

FIG. 2 is an example of a table in which abnormal patterns based on combinations of change trends of monitoring data are associated with factor information thereof, and the contents of this table are set and held in the abnormal pattern holding means 104. Hereinafter, abnormal patterns (a), (b), which are referred to from this table.
(C) and (d) will be described.

(A) Combination of patterns in which PV is not changed but MV and RV are increased:
In a system that is in equilibrium with a certain mass balance, the output of the controller increases (control valve opening command) to maintain the mass balance, and if the control valve opening increases as a result, the specified The reason is that the control valve opening is increased because the pressure required to flow the amount of the substance downstream is too low at the previous control valve opening.

The following factors can be considered as the root factor.
• Process piping and / or control valves are prone to blockage.
・ Since the discharge pressure of the pump or blower supplying substances to the system is throttled by the valve installed before or after them, the specified pressure cannot be secured.

(B) Combination of patterns in which PV does not change but MV and RV are lowered:
In a system balanced with a certain mass balance, the output of the controller decreases (control valve close command) to maintain the mass balance, and if the control valve opening decreases as a result, the The reason is that the pressure required to flow the amount of the substance downstream is too high at the previous control valve opening, so that the control valve opening is decreasing.

The following factors can be considered as the root factor.
-The plug and / or seat ring of the control valve is worn out, and the amount of substance passing through at the same opening is increasing.
• Material outflow (leakage from process piping, etc.) has occurred in the system upstream of the control valve.

(C) Combination of patterns in which PV rises, MV falls, and RV rises:
In a system that is in equilibrium with a certain mass balance, the output of the controller decreases (control valve close command) to maintain the mass balance, but the control valve does not follow it and MV and control valve The deviation of the opening continues to occur and the control valve is abnormal. As a possible factor, a pressure drop of a driving source (air or hydraulic pressure) can be considered.

(D) A combination of patterns in which RV does not change but MV increases or decreases regardless of PV behavior:
A control valve abnormality is also caused when the control valve opening does not change with an increase (or decrease) in the MV of the controller. As the assumed factors, the control valve stem is fixed and / or the gland packing is overtightened.

  In the embodiment of FIG. 1 described above, the controller 4 is shown as an independent element for the sake of simplicity, but it is equivalent to the function realized in the control station of the distributed control system. In addition, the control loop diagnosis apparatus 100 can be incorporated in a host device of the distributed control system. Alternatively, an embodiment in which the distributed control system is operated as an application of a user PC communicating with the distributed control system via a network may be used.

  According to the present invention, since diagnostic information has objectivity, this information can be passed to a higher-level system to construct a medium- and long-term management system for plant equipment. In other words, CBO (Condition Based Operation) in cooperation with control loop soundness diagnosis, and in addition to the above, high soundness including individual soundness diagnosis of sensors, transmitters and control valves A reliable CBO can be constructed.

  In addition, it is possible to realize equipment diagnosis by centrally managing the above CBO at the equipment level and efficient operation of equipment assets by CBM (Condition Based maintenance) that supports CBO over the medium to long term. It is.

It is a functional block diagram showing an embodiment of a control system to which a control loop diagnosis apparatus of the present invention is applied. It is the table which matched the abnormal pattern based on the combination of the change tendency of monitoring data, and its factor information. It is a functional block diagram which shows the structural example of the control system to which the conventional control loop diagnostic apparatus was applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pipe line 2 Control valve 3 Transmitter 4 Controller 100 Control loop diagnostic apparatus 101 Input processing means 102 Monitoring data holding means 103 Change tendency monitoring means 104 Abnormal pattern holding means 105 Diagnosis means 106 Diagnostic information holding means 107 Diagnostic result notification means

Claims (4)

A control valve is inserted into the pipe through which the measurement fluid flows, and a control calculation is performed using the measurement signal of the flow rate of the measurement fluid, and the soundness of the control loop that controls the control valve is diagnosed using the control signal obtained by the calculation In the control loop diagnostic device,
Input processing means for acquiring and holding the measurement signal, the control signal and the opening signal of the control valve as monitoring data;
Change trend monitoring means for reading out the monitoring data from the input processing means and monitoring a combination of change tendency patterns of each monitoring data;
A control loop diagnosis apparatus comprising:   The control loop diagnosis apparatus according to claim 1, wherein the change tendency monitoring unit classifies the monitoring data into a change tendency pattern of any one of ascending, descending, hunting, and no change. An abnormal pattern holding means for setting and holding an abnormal pattern of a control loop assumed corresponding to a combination of patterns of change tendency of the monitoring data;
Diagnosis that outputs and holds abnormality diagnosis information together with time information when the abnormality pattern held in the abnormality pattern holding means coincides with the change tendency pattern of each monitoring data monitored by the change tendency monitoring means Means,
The control loop diagnosis apparatus according to claim 1, further comprising: 4. The control loop diagnosis apparatus according to claim 3, further comprising a diagnosis result notifying unit that displays or sends the diagnosis information held in the diagnosis unit to a network.

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