JP3308119B2 - Abnormality detection device for flow control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting device for a flow control system which can detect an abnormality of a device constituting a control loop, can improve the reliability of flow measurement, and can easily perform maintenance.

[0002]

2. Description of the Related Art FIG. 6 is an explanatory view of the configuration of a conventional example generally used in the past. For example, "Industrial Measurement Handbook" (edited by pneumatic instruments), edited by Yokogawa Electric Works, published by Tokyo Denki University Press Showa 41 Issued December 10, page 2
This is shown in FIGS.

In FIG. 6, reference numeral 1 denotes a conduit through which a measurement fluid 2 flows. 3 is a valve for controlling the flow rate of the measurement fluid, 4 is a valve 3
This is a positioner that controls the valve opening degree. Reference numeral 5 denotes a controller for controlling the positioner 4.

[0006] Reference numeral 6 denotes a flow meter main body which detects the flow rate of the measurement fluid controlled by the valve 3 and sends a detection signal to the controller 5. In this case, a differential pressure transmitter is used. Reference numeral 7 denotes a pressure guiding tube for transmitting the pressure of the measurement fluid 2 to the flow meter body 6. Reference numeral 8 denotes an orifice for generating a differential pressure according to the flow rate.

In the above-described configuration, the measurement fluid 2 is
Flows, the flow meter body 6 measures the flow rate of the measurement fluid 2. The flow measurement signal of the flow meter body 6 is sent to the controller 5 and compared with a target value. An adjustment signal is sent to the valve positioner 4 to open and close the valve 3.

[0006]

However, in such an apparatus, even when the impulse line 7 is clogged and there is an abnormality in the impulse line 7, the flow rate is so large that the output of the flowmeter main body 6 can be cut off. An abnormality can be detected when a change occurs or when an inspection such as a periodic inspection is performed, but it is often difficult to detect the abnormality.

[0007] The valve positioner 4, the controller 5, and the flow meter body 6 also have the same problem.

The only way to prevent these abnormalities before an output abnormality occurs is to predict them empirically from changes in the output or to find an abnormal state through regular inspection of the operator. From the safety side, frequent periodic inspections are necessary, and frequent inspections have the problem that it takes time and effort. Further, there is a problem that a sudden failure cannot be dealt with.

The present invention has been made to solve the above-mentioned problems of the prior art. SUMMARY OF THE INVENTION It is an object of the present invention to provide an abnormality detection device for a flow control system capable of constantly monitoring a state of a control loop and issuing an alarm when a failure of the control loop exceeds a predetermined level. Aim.

That is, it is possible to detect the abnormality of the device constituting the control loop, and to improve the reliability of the flow rate measurement.
An object of the present invention is to provide an abnormality detection device for a flow control system that is easy to maintain.

[0011]

In order to achieve this object, the present invention provides a pipeline through which a measurement fluid flows, a detection end for detecting a flow rate of the pipeline, and an output of the detection end. An abnormality detection device for a flow control system, comprising: a controller for control; and an operation terminal operated by a control signal of the controller to operate the flow rate of the pipeline, wherein the detection terminal upstream of a control loop from the operation terminal. It said check signal for changing the transmission signal when required is provided between the up
A check signal transmitting unit that is provided on the control loop and outputs instead of the control signal, and is provided between the operation terminal and the detection terminal on the upstream side of the control loop based on the check signal. Diagnostic means for detecting a change in the measurement signal and comparing it with a predetermined reference value to detect an abnormality in the device constituting the control loop and issuing a detection signal; and It is composed.

[0012]

In the above configuration, when diagnosing a failure of the control loop, the check signal transmitting means includes:
The control signal is output instead of the normal transmission signal for which the flow rate is controlled. The diagnostic means detects a change in the measurement signal based on the check signal, compares the change with a predetermined reference value, detects an abnormal state of the device constituting the control loop, and outputs a detection signal. Hereinafter, a detailed description will be given based on embodiments.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part configuration of an embodiment of the present invention. In the figure, the configuration of the same symbol as FIG. 6 represents the same function. Hereinafter, only differences from FIG. 6 will be described.

In the drawing, reference numeral 11 denotes an operation end, in this case, a detection end upstream of the valve 3 in the control loop, in this case, provided between the flowmeter main body 6 and, in this case,
This is a check signal transmitting means for outputting the output signal of the flow meter body 6 from the transmission signal α to the check signal β when required.

Reference numeral 12 denotes an operation terminal, in this case, a detection terminal upstream of the valve 3 in the control loop, in this case, provided between the flow meter main body 6 and detects a change in a measurement signal based on a check signal. Then, it is a diagnosing means for detecting an abnormality of a device constituting the control loop by comparing with a predetermined reference value and issuing a detection signal.

In the above configuration, when diagnosing a fault in the control loop, the output signal of the flowmeter main body 6 is switched from the normally transmitted transmission signal α to the check signal β by the check signal transmitting means 11. Output.
The diagnosing means 12 detects a change in the differential pressure based on the check signal β, compares it with a predetermined reference value, detects an abnormal state of the device constituting the control loop, and outputs a detection signal.

That is, the clogging diagnosis is normally performed at regular intervals T as shown in FIG. Needless to say, diagnosis may be performed at any time. Here, the vertical axis indicates the output amount, and the horizontal axis indicates the time axis. The same applies to the case where a graph is shown below.

FIG. 2 (b) is an enlarged view of FIG. 2 (a). In this case, the check signal is β in a direction lower than the actual output.
Indicates a change. In response to the check signal, the controller 5 changes in a direction to increase the flow rate of the measurement fluid 2 as shown in FIG. The change in this case is
It depends on the set value of the PID operation.

Since the control amount of the controller 5 changes,
As shown in FIG. 2D, the flow rate Q changes accordingly. The fact that the control amount of the controller changes in the direction of increasing the flow rate means that the opening degree of the valve valve 3 increases, and the flow rate Q also changes accordingly. Since the flow rate Q and the differential pressure ΔP have the following relationship, if the flow rate Q changes, the differential pressure ΔP around the orifice 8 also changes.

Q = K (ΔP) ^1/2 (1) K: proportionality constant When the opening degree of the valve 3 increases, the pressure loss generated in the valve 3 decreases as shown in FIG. Therefore, the pressure (static pressure) on the upstream side of the orifice 8 also increases.

Here, a case where the pressure guiding tube 7 is clogged will be considered as an example of the abnormality detection. If the impulse line 7 is normal,
As shown in FIG. 2F, the differential pressure Δ
The signal of P also changes. When the impulse line 7 is clogged, FIG.
As shown in (g), even when the flow rate changes, the signal of the differential pressure ΔP detected by the diagnostic means 12 does not change much.

The change in the signal of the differential pressure ΔP detected by the diagnosing means 12 in a state in which the pressure guiding tube 7 is not completely clogged and which is almost clogged has a slower response than when the pressure guiding tube 7 is normal (time constant). Is larger).

Therefore, the state of the response input to the diagnostic means 12 when the valve opening degree of the valve 3 is changed by the check signal transmitting means 11 is compared with that in the normal state, so that the pressure guiding pipe 7 is changed. Can be easily detected at any time as to whether the state is normal and not clogged.

An example of determining whether the pressure guiding tube 7 is in a normal state without being clogged is performed as follows, for example. It is determined whether the input differential pressure change amount y input to the diagnostic unit 12 after t seconds after the output of the check signal transmitting unit 11 is changed is larger or smaller than the set threshold value x.

FIG. 3A shows a state in which the measurement output value α of the flow meter body 6 is changed β by the check signal transmitting means 11 for checking.

FIG. 3B shows the output value α of the flow meter body 6.
Is changed by the check signal transmission means 11 and the corresponding input signal to the diagnosis means 12 in a normal state is shown. FIG. 3C shows a case in which the input differential pressure change signal amount y to the diagnostic means 12 after t seconds is larger than the set value x, the determination is “good”, and the impulse line 7 is clogged. The absence is determined by the diagnosis means 12.

FIG. 3D shows a case where the input differential pressure change signal amount y to the diagnostic means 12 after t seconds is smaller than the set value x, and the judgment is "No". A signal is output from the diagnostic means 12. Note that t and x are:
Set to an appropriate value based on the state of the input differential pressure change during normal operation.

As an example of the alarm output from the diagnosis means 12, for example, the following is performed. (1) In the case of a device having an LCD display, a predetermined error number is displayed on the LCD, or the display blinks.

(2) The output current is varied according to a predetermined rule. (3) If the device is compatible with a field bus, an error code is output to the field bus. As a result, since the check signal transmitting means 11 and the diagnosing means 12 are provided in the middle of the flow control system, the risk of erroneous control due to an abnormality in the system such as clogging of the pressure guiding tube 7 can be easily avoided at any time. be able to.

FIGS. 4 and 5 are explanatory diagrams of the operation of the main part of another embodiment of the present invention. The present embodiment relates to an abnormality detection device when the controller 5 has an abnormality. The configuration of the device is the same as that of FIG.

FIG. 4A shows the output of the check signal generating means 11 when the controller 5 is normal.
(B) Controller 5 when controller 5 is normal
FIG. 4C shows the flow rate Q when the controller 5 is normal, and FIG. 4D shows the input signal to the diagnostic means 12 when the controller 5 is normal.

FIG. 5A shows the output of the check signal generating means 11 when the controller 5 is abnormal, and FIG. 5B shows the output of the controller 5 when the controller 5 is abnormal.
(C) is the flow rate Q when the controller 5 is abnormal, FIG.
(D) is an input signal to the diagnostic means 12 when the controller 5 is abnormal.

With the above operation, the abnormality of the controller 5 can be detected by the diagnosis means 12. In the above-described embodiment, the pressure guiding tube 7 or the controller 5
However, the present invention is not limited to this case. For example, when there is an abnormality in each device in the flow control loop, for example, in the operation device, in this case, the valve positioner 4 or the valve 3 has an abnormality. Also in the case where there is, an abnormality can be detected.

[0034]

As described above, according to the present invention, a pipe through which a measurement fluid flows, a detection end for detecting a flow rate of the pipe,
A controller for control to which the output of the detection end is input,
An abnormality detecting device for a flow control system having an operation terminal operated by a control signal of the controller to operate the flow rate of the pipeline, provided between the operation terminal and the detection end upstream of a control loop. A check signal that changes the transmission signal when necessary is placed on the control loop.
A check signal transmitting means for outputting the control signal in place of the control signal, and detecting a change in a measurement signal based on the check signal provided between the operation terminal and the detection terminal on the upstream side of the control loop, and Diagnostic means for detecting an abnormality of a device constituting the control loop by comparing the reference value with a reference value and issuing a detection signal.

As a result, the check signal transmission means 11 and the diagnosis means 12 are provided in the middle of the flow control system.
The risk of erroneous control due to an abnormality in the flow control system can be easily avoided at any time.

Therefore, according to the present invention, it is possible to detect an abnormality in a device constituting a control loop, to improve the reliability of flow measurement, and to realize a flow control system abnormality detecting device which is easy to maintain. I can do it.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of FIG. 1;

FIG. 3 is an operation explanatory diagram of FIG. 1;

FIG. 4 is an explanatory diagram of an operation of a main part of another embodiment of the present invention.

FIG. 5 is an explanatory diagram of an operation of a main part of another embodiment of the present invention.

FIG. 6 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipeline 2 Measurement fluid 3 Valve 4 Valve positioner 5 Controller 6 Flowmeter main body 7 Pressure guiding tube 8 Orifice 11 Check signal generation means 12 Diagnostic means

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Fujita 2-9-132 Nakamachi, Musashino-shi, Tokyo Examiner in Yokogawa Electric Corporation Masayuki Mori (56) References JP-A-54-98475 (JP, A) ) Jpn. Sho 57-50703 (JP, U) Jpn. Hei 4-47707 (JP, U) JP 6-5197 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 1 / G01F 3 / G01F 15 / G01F 25 / G05B 23 / G05D 7 /

Claims (1)

(57) [Claims] 1. A pipe through which a measurement fluid flows, a detection end for detecting a flow rate of the pipe, a controller for control to which an output of the detection end is inputted, and the pipe operated by a control signal of the controller. An abnormality detecting device for a flow control system having an operation terminal for controlling a flow rate of a road, wherein a check signal provided between the operation terminal and the detection terminal on an upstream side of a control loop for changing a transmission signal when necessary is provided. On the control loop,
A check signal transmitting means for outputting in place of the control signal, and detects a predetermined reference value to change in the measured signal based on the check signal is provided until the detected end of the upstream side of the control loop from the operating end An abnormality detection device for a flow control system, comprising: a diagnosis unit for detecting an abnormality of a device constituting the control loop and generating a detection signal.