JPS6017317A - Device for preventing detector from malfunction - Google Patents

Abstract

PURPOSE:To interrupt an input to a means for controlling an output from a detector precisely at the abnormal state of the detector to prevent the detector from malfunction by providing the titled device with a monitoring means of the variation factor of a signal outputted from the detector and a means for interrupting the input of the detector output to the control means. CONSTITUTION:A pressure measuring signal from a pressure transmitter 11 for a pressure gauge 5 fitted to a pressure regulated tank 2 for a vacuum equipment is inputted to a pressure alarm generator 12 and the pressure variation factor monitoring circuit 13. The pressure variation factor monitoring circuit 13 finds out the variation factor of the pressure measuring signal outputted from the pressure transmitter 11 through a differentiator, and if the variation factor signal exceeds a reference signal, turns on a contact corresponding to the prescribed value or more of the pressure variation rate. When the pressure transmitter 11 is failed, the pressure measuring signal is suddenly changed, so that a signal line closing a disconnection valve 7 by a pressure regulated tank pressure high signal outputted from the pressure alarm generator 12 is blocked and the disconnection valve 7 is kept at the opened status.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a detector malfunction prevention device, and more particularly, to a detector malfunction prevention device suitable for preventing air leakage in vacuum equipment, for example.

[Background of the invention]

FIG. 1 shows vacuum equipment as an example of a system targeted by the present invention.

The vacuum equipment shown in this FIG. It includes a pressure gauge 5 provided in the regulating tank 2, a controller 6 provided between the pressure gauge 5 and the pressure regulating valve 4, and a shield 7 provided between the pressure regulating tank 2 and the gas usage equipment 3. There is. The pressure regulating valve 4 is operated by a controller 6 based on a signal from a pressure gauge 5.
The amount of inflowing gas is controlled through the pressure regulating tank 2, and the pressure in the pressure regulating tank 2 is controlled to a set value. The said Sha Arai 7 is
When an abnormality occurs in the gas generator 1 or the pressure regulating tank 2, a signal from the pressure gauge 5 is used to prevent the abnormality from spreading to the gas usage equipment 3. This vacuum equipment is a vacuum equipment that is always operated under negative pressure, and it is necessary to strictly prohibit the mixing of air, which is the surrounding gas.

In the vacuum equipment described above, conventionally, in order to deal with abnormal air leakage in the gas generator 1 or pressure adjustment tank 2, when the signal of the pressure gauge 5 exceeds a specified value, it is determined that there is an air leak and Arai An interlock is provided to close 7.

Figure 2 shows an interlock as a conventional technology, and the third
The figure shows a measurement circuit that generates the high pressure contact signal shown in FIG. 2.

In the measurement circuit shown in FIG. 3, the pressure measurement signal from the pressure transmitter 11 is input to the pressure alarm generator 12 and compared with a predetermined pressure standard value reference signal, and when the input signal becomes larger than the reference signal. When the pressure is high, the contact e is turned on.

However, the above-mentioned conventional technology has the disadvantage that the Arai will automatically close if the pressure measuring device malfunctions as a detector.In order to avoid automatic closing due to the malfunction of the pressure measuring device as much as possible, the pressure measuring device is made redundant and two outs. Measures have been taken to automatically close the system using logic fees such as Ob3, but the increase in the number of measuring devices poses a problem of increasing economic burden.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an economically advantageous detector malfunction prevention device that can reliably prevent input of the detector output to the control means when the detector is abnormal.

[Summary of the invention]

A feature of the present invention is that in a system equipped with a detector that measures a process quantity and a control means that automatically performs a posture maintenance operation when the output of the detector deviates from a specified value, the output signal of the detector is The present invention includes means for monitoring the rate of change, and means for blocking input of the detector output to the control means when the rate of change exceeds a predetermined value. This made it possible to reliably achieve the above objective.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained by taking the vacuum equipment shown in FIG. 1 as an example, and further based on the embodiments shown in FIGS. 4 to 8.

FIG. 4 shows a measurement circuit of a pressure gauge 5 as a detector attached to the pressure regulating tank 2 of the vacuum equipment shown in FIG. In other words, the circuit serves as a means for monitoring the rate of change of the output signal of the detector, which is a component of the present invention, and when the rate of change shows a predetermined value or more, the rate of change exceeds the specified value. A measurement circuit for turning the contact signal 'kON' is shown.

In the measurement circuit shown in FIG. 4, the pressure measurement signal (process amount) from the pressure transmitter 11 is input to both the pressure alarm generator 12 and the pressure change rate monitoring circuit 13. The pressure alarm generator 12 compares the input signal with a predetermined pressure standard value reference signal, and turns on the high pressure contact when the input signal is larger than the pressure standard value reference signal. In the pressure change rate monitoring circuit 13, the pressure measurement signal from the pressure transmitter 11 is passed through a differentiator to determine the change rate of the pressure measurement signal, and the change rate signal is compared with a predetermined pressure change rate reference signal to determine the change. When the rate signal becomes sharper than the pressure change rate reference signal,
Turn ON the contact whose pressure change rate is higher than the specified value.

Next, FIG. 5 CI) shows the rate of change regulation as a means for blocking input of the detector output to the control means when the rate of change, which is a component of the present invention, exceeds a predetermined value. An interlock is shown in which a high pressure interlock signal is bypassed and the pressure high signal is invalidated by a signal exceeding the above value, and FIG. 5 (II) shows a circuit portion constituting the interlock.

In this FIG. 5 (II), (a) shows an OR circuit that outputs a signal C from either signal A or B, and (b) shows an OR circuit that outputs a signal C from any signal A or B.
(C) shows a NOT circuit in which a signal opposite to the A signal is output as a B signal.

In the interlock shown in FIG. 5(1), the pressure high signal is delayed by a timer so that the pressure high signal does not operate before the pressure change rate monitoring circuit operates.

Next, this interlock will be explained in more detail in relation to the vacuum equipment shown in FIG.

In this embodiment, the shield 7 employs a solenoid valve that closes with a spring force when the power is turned off. Whether the Sharai 7 is an electric valve that opens and closes using the driving force of an electric motor or an air valve that operates using air pressure, the operation circuit is different, but the intended operation content is the same. An operation switch for opening and closing the shutoff valve 7 is normally installed on a control panel that remotely controls the shutoff valve 7.

Further, the operation of the vacuum equipment shown in FIG. 1 will be explained as follows.

That is, before starting the operation of the vacuum equipment, the gas generator 1,
The pressure adjustment tank 2 and the gas usage equipment 3 are equipped with gas exhaust equipment (
(not shown) is evacuated to a vacuum state defined by In this state, the pressure indication value of the pressure gauge 5 installed in the pressure regulating tank 2 decreases, and the contact signal indicating the pressure in the pressure regulating tank is turned OFF'. Also, pressure gauge 5
Since the rate of change in pressure is small, the contact signal whose rate of change in pressure in the pressure regulating tank is equal to or higher than the specified value is also in an OFF state. In this state, when the cutoff valve switch installed on the control panel is set to the open position, the coil of the cutoff valve (electromagnetic valve) 7 is excited, the electromagnetic force overcomes the spring force, and the cutoff valve 7 is opened. The control circuit is configured to self-maintain so that the shutoff valve 7 remains open even when the shutoff valve switch is returned to the intermediate position by a spring. When the shutoff valve switch is set to the closed position, the self-holding circuit of the shutoff valve 7 is cut off, so the shutoff valve 7 is placed in a non-excited state, and the shutoff valve 7 is closed by the spring force. Therefore, when the Makabe equipment shown in FIG. 1 reaches a vacuum state below a specified pressure, the shutoff valve 7 is opened and closed by the operator operating the shutoff valve switch. The shutoff valve 7 is fully opened, gas is generated from the gas generator 1, and the gas is supplied to the gas usage equipment 3 while maintaining a specified pressure state. The pressure regulating valve 4 is designed to automatically maintain this specified pressure state.
is automatically controlled. In normal operation, it is operated in the above state, but if the pressure in the pressure regulating tank 2 increases during this operating state, as explained in Fig. 4, the pressure will exceed the predetermined pressure value. When this occurs, the pressure adjustment tank pressure high signal is turned on to fully operate the timer element, and after a predetermined time has elapsed, the self-holding of the shutoff valve 7 is automatically cut off and the shutoff valve 7 is closed. However, if the pressure transmitter 11 malfunctions, the pressure measurement signal will change rapidly.
Since the signal of the pressure change rate monitoring circuit 13 that is higher than the specified value of the pressure change rate is also turned on at the same time, the signal line where the shutoff valve 7 is automatically closed due to the high pressure signal of the pressure regulating tank is blocked, so the shutoff valve 7 is automatically closed. Not closed.

Next, FIG. 6 shows the pressure change rate monitoring circuit as means for monitoring the rate of change of the output signal of the detector, and the circuit for controlling the output of the detector when the rate of change exceeds a predetermined value. The operation of each component when an air leakage abnormality occurs in a system to which all detector malfunction prevention devices including the above-mentioned interrots % as a means for blocking input is applied will be shown. In Fig. 6, when an air leak occurs, the pressure gauge signal rises as shown in Fig. 6 (a), and the rate of increase is less than the specified pressure change rate, so the pressure change rate monitoring circuit output does not operate. , only the pressure alarm generator is activated and the sheath valve 7 is automatically closed.

Next, FIG. 7 shows all the operations of each component when a detector failure (abnormal high reading value) occurs.

In Fig. 7, the pressure gauge signal rises rapidly due to a detector failure, and the pressure tube shaft generator and pressure change rate monitoring circuit output operate almost simultaneously, but within the time set by the timer, the pressure change rate Since the monitoring circuit output signal prevents the transmission of the pressure alarm generator's operation, the shutoff valve 7 was not closed but remained open! Stay in Mani.

Normally, the causes of failure of a pressure sensor, which is a pressure gauge, are broadly classified into failures in the pressure receiving part and failures in the amplification part. There are many failure modes in which a failure in the pressure receiving part causes the indicated value to gradually change, and a failure mode in which the failure in the amplifier part often causes a sudden change in the output signal.

Thus, the detector abnormality detection system of the illustrated embodiment of the present invention is designed to protect against failures in the amplifier section, and is not protected against failures in the pressure receiving section that causes gradual changes in indicated values. However, if the indicated value changes gradually, the operator can monitor the indicated value behavior, recognize an abnormality in the pressure detector, and take countermeasures before the automatic interlock operates. There are many cases.

Next, FIG. 8 shows a state in which the control mode of the controller 6 is switched from the fully automatic mode to the manual mode in response to a signal exceeding the pressure change rate specified value.

As shown in FIG. 8, normally the pressure detector output is automatically controlled in automatic mode via a PID (proportional, integral, differential) controller 21 so that it reaches a predetermined set value. There is. If a signal indicating that the pressure change rate is higher than the specified value is generated, the mode changeover switch 23 is automatically switched from automatic mode to manual mode using the manual setting device 22, and automatic control is disabled using the abnormal pressure detector signal. prevent.

When the pressure detector output output increases, the pressure control valve 4 operates in the closing direction, and the pressure in the pressure regulating tank 2 decreases. In many cases, it is sufficient for the operator to manually switch modes when an alarm occurs with a rate of change greater than the specified value.

If the pressure detector of the pressure regulating tank 2, that is, the pressure gauge 5, becomes abnormal, the input of the pressure detector output to the control means is blocked as described above, and the abnormal pressure detector must be maintained. However, although the pressure control valve during this maintenance is not shown in Figure 1, pressure gauges are also installed in the gas generator 1 and gas equipment 3, so the pressure control valve is operated based on the instructions from the pressure gauge. However, by taking measures such as replacing the malfunctioning part of the pressure detector with a spare part, normal operation can be restored in a short period of time, so the burden on the operator does not increase significantly.

According to the above-mentioned embodiment, it is possible to prevent malfunction of the shielding well 7 due to an abnormality in the pressure gauge 5, and therefore it is possible to improve the operating rate of the plant.

Although the probability of occurrence of equipment abnormalities such as cracks in tanks and piping is very small, the risk associated with such equipment abnormalities is high, so protective measures are provided against them. The probability of a malfunction occurring in a detector that activates the protection means is usually higher than the probability of occurrence of equipment abnormalities such as cracks, so protection against the above-mentioned high-risk abnormalities reduces the equipment operating rate. By applying the invention, detector malfunctions can be detected early and easily and protective measures can be prevented from operating, reducing the probability of plant stoppages due to detector malfunctions and improving plant availability. It becomes possible to do this.

Note that the present invention is particularly effective when applied to printing that operates continuously for a long period of time and in which restarting the plant is not easy.

Although the embodiments of the present invention have been described with reference to vacuum equipment,
The present invention is applicable not only to vacuum equipment but also to equipment such as pressure vessels. For example, for equipment such as nuclear reactor plants, where the reactor vessel is normally maintained at high pressure and operated, the reactor is fully automatically shut down when the pressure exceeds a specified value. The invention is applicable. In a nuclear reactor plant, redundancy is legally required for the measurement circuit that directly protects the reactor, so applying the present invention to the measurement and control circuit of the reactor auxiliary equipment that indirectly leads to reactor shutdown. , the effect is a dog.

〔Effect of the invention〕

According to the present invention described above, there is provided a means for monitoring the rate of change of the output signal of the detector, and when the rate of change exceeds a predetermined value, all input to the control means for the detector output is blocked. If the response characteristics of the process to be measured are taken into account, and a rapid response that exceeds the rate of change in the process quantity at the time of an assumed abnormality is detected, the detector signal is determined to be an abnormality in the detector itself. As a result, in the event of a detector abnormality, the input of the detector output to the control means can be reliably blocked, which not only has the effect of improving the operation rate of the plant, but also improves the structure. Since it is simple, it has an excellent economical effect.

[Brief explanation of the drawing]

Figure 1 is a diagram showing vacuum equipment as one system to which the present invention is applied, Figure 2 is a diagram showing an interlock metal according to the prior art, Figure 3 is a diagram showing a measuring circuit according to the prior art, and Figure 4 is a diagram showing a measuring circuit according to the prior art. FIG. 5 (
1) is a diagram showing an interlock as means for blocking input of the detector output to the control means when the rate of change, which is a component of the present invention, exceeds a predetermined value;
Figure (II) (a) to (C) are explanatory diagrams of the circuit parts that constitute the same interlock, and Figure 6 is the same as Figures 4 and 5.
In the embodiment of the present invention shown in the figure, an explanatory diagram of the operation of each component device when an air leakage abnormality occurs, FIG. 7 is an explanatory diagram of the operation of each component device when the same detector fails, and FIG. 8 is a pressure change rate of the detector FIG. 3 is a diagram showing the relationship between set values and mode switching of the controller. DESCRIPTION OF SYMBOLS 1... Gas generator, 2... Pressure adjustment tank, 3... Gas usage equipment, 4... Pressure regulation valve, 5... Pressure gauge as a detector, 6... Pressure controller , 7... breaker,
11...Pressure transmitter, 12...Pressure alarm generator, 1
3... Rate of change monitoring circuit, 21... ID controller, 22
...Manual setting device, 23...Mode selection switch. Agent Patent Attorney Masami Akimoto 2nd Figure 3 Figure 11 1Z Figure 6 Figure -'1

Claims (1)

[Claims] 1. In a system equipped with a detector that measures a process quantity and a control means that automatically performs a protective action when the output of the detector deviates from a specified value, monitor the rate of change of the output signal of the detector. A device for preventing malfunction of a detector, comprising: means for preventing input of the detector output to the control means when the rate of change exceeds a predetermined value.