JPH0223809B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a protection control device that performs a protection control operation based on the output of a detector. This invention relates to a protection control device that prevents this from occurring.

[Background of the invention]

FIG. 1 shows vacuum equipment as an example of a system to which the present invention is applicable.

The vacuum equipment shown in FIG. 1 includes a gas generator 1,
A pressure regulating tank 2 for temporarily storing gas, gas usage equipment 3, a pressure regulating valve 4 provided between the gas generator 1 and the pressure regulating tank 2, a pressure gauge 5 provided in the pressure regulating tank 2, and this pressure gauge 5. A controller 6 is provided between the pressure regulating valve 4 and the pressure regulating valve 4, and a cutoff valve 7 is provided between the pressure regulating tank 2 and the gas usage equipment 3. The pressure regulating valve 4 is operated by a controller 6 based on a signal from a pressure gauge 5.
The inflow gas amount is controlled through the pressure adjustment tank 2 to maintain the pressure in the pressure adjustment tank 2 at a set value. Furthermore, when an abnormality occurs in the gas generator 1 or the pressure regulating tank 2, the sheath valve 7 prevents the abnormality from spreading to the gas usage equipment 3 based on a signal from the pressure gauge 5. This vacuum equipment 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 leakage. An interlock is provided to close the valve 7.

FIG. 2 shows an interlock by a protection control device according to the prior art, and FIG. 3 shows a measurement circuit that produces a contact signal of the pressure level shown in FIG. 2. Third
As shown in the figure, in the measurement circuit, a pressure transmitter 11
The pressure measurement signal from the pressure alarm generator 12 is compared with a predetermined pressure standard value reference signal, and when the pressure measurement signal as an input signal becomes larger than the reference signal, the high pressure contact is turned ON. It is supposed to work like this.

However, the conventional technology has the disadvantage that the valve automatically closes due to a malfunction due to a malfunction of the pressure measuring device as a detector. 2 out of 3 with redundancy
Measures such as automatic closure using logic such as these have been implemented, but the increase in the number of measuring devices poses a problem of increasing economic burden.

[Purpose of the invention]

An object of the present invention is to provide a protection control device that prevents a protection control operation for a controlled object from being performed even if the detector itself fails.

[Summary of the invention]

In order to achieve the above object, the present invention uses a comparator to compare the output value from a detector that measures a process amount with a specified value, and automatically performs a protective operation when the output value deviates from the specified value. In order to achieve this, in the protection control device in which the protection control signal is output from the comparator, the protection control signal from the comparator is passed through a timer and a gate circuit, and the output value from the detector is compared via a differentiator. The gate circuit is configured to gate-control the gate circuit based on a detector failure signal as a judgment result holding output obtained from the comparator in the event of a detector failure. This is what I did.

[Embodiments of the invention]

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

That is, FIG. 4 shows a pressure gauge 5 as a detector attached to the pressure adjustment tank 2 of the vacuum equipment shown in FIG.
The measurement circuit is shown below. A circuit that monitors the rate of change of the detector output signal, which is a component of the present invention, is newly provided, and when the rate of change shows a predetermined value or more, the rate of change exceeds the specified value. It is designed to turn on a contact signal indicating a certain condition.

More specifically, 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. As described above, 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 becomes larger than the pressure standard value reference signal. However, in the pressure change rate monitoring circuit 13, the pressure measurement signal from the pressure transmitter 11 is passed through a differentiator to obtain the change rate of the pressure measurement signal, and the change rate signal is compared with a predetermined pressure change rate reference signal. If the rate of change signal becomes larger than the pressure change rate reference signal,
The pressure transmitter 11 is determined to be malfunctioning and a contact is turned on to indicate that the pressure change rate is greater than a specified value.

Now, FIG. 5 shows a protection system according to the present invention in which when the rate of change exceeds a predetermined value, the interlock signal due to high pressure is nullified by a signal indicating that the rate of change is greater than the specified value. The interlock in the control device is shown, and FIG. 5 shows each circuit part that constitutes the interlock.

In this Figure 5, a has an input/output logic of A+
A gate (OR circuit) where B = C, b is a gate (1-input negative AND circuit) whose input/output logic is A/=C, and c is a gate whose input/output logic is =B. (NOT circuit or inversion circuit).

In the interlock shown in Fig. 5, the interlock signal due to high pressure is set so that the interlock signal due to high pressure is not output before the pressure change rate monitoring circuit outputs a signal indicating that the pressure change rate is above the specified value. A timer is used to delay the time.

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

In this embodiment, a solenoid valve that closes by a spring force when the power is turned off is used as the stop valve 7. Whether the sheath valve 7 is an electric valve that opens and closes using the driving force of an electric motor or a pneumatic valve that operates using air pressure, the operating circuit is different, but the intended operation is the same. An operating switch for opening and closing the sheath valve 7 is usually installed on a control panel that remotely controls the sheath 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, pressure adjustment tank 2, and gas usage equipment 3 are evacuated to a specified vacuum state by gas exhaust equipment (not shown). In this state, the pressure indication value of the pressure gauge 5 installed in the pressure adjustment tank 2 gradually decreases, and the contact signal of the pressure adjustment tank pressure high
It will be in the OFF state. Also, since the rate of pressure change in the pressure gauge 5 is small, the contact signal indicating that the rate of pressure change in the pressure adjustment tank is higher than the specified value is also turned OFF.
It is in a state of being In this state, when the windshield valve switch installed on the control panel is set to the open position, the coil of the windshield valve (electromagnetic valve) 7 is energized, and the electromagnetic force overcomes the spring force. is to be released. The control circuit consisting of an OR circuit and a 1-input negative AND circuit is configured to self-maintain as a flip-flop so that even when the stop valve switch returns to the intermediate position by a spring, the stop valve 7 remains open. ing. On the other hand, when the stop valve switch is set to the closed position, the self-holding circuit of the stop valve 7 is disconnected by the 1-input negative AND circuit.
The sheath valve 7 is in a non-energized state and is closed by the spring force. Therefore,
When the vacuum equipment shown in Figure 1 reaches a vacuum state below the specified pressure, the operator can open and close the shutter valve 7 by opening and closing the shutter valve switch. It is something that Normally, the opening valve 7 is opened to generate gas from the gas generator 1,
Gas is supplied to the gas usage equipment 3 while maintaining a specified pressure state, and the pressure regulating valve 4 is automatically controlled so as to automatically maintain this specified pressure state. In case of normal operation,
It is operated in the above state, but if the pressure in the pressure regulating tank 2 gradually increases in this operating state, as explained in FIG. The interlock signal due to the high pressure is turned on and operates the time element, and after a predetermined time has elapsed, the self-holding of the chopper valve 7 is automatically released and the chopper valve 7 is closed. However, if the pressure transmitter 11 malfunctions, the pressure measurement signal will change rapidly.
Since the signal indicating that the pressure change rate in the pressure change rate monitoring circuit 13 is equal to or higher than the specified value is also turned on at the same time, this signal blocks the interlock signal due to the pressure adjustment pressure height. It is not automatically closed. To explain in more detail, FIG. 6 shows the operation of each component when an air leakage abnormality occurs. As shown in Figure 6, when there is an air leakage abnormality, the pressure gauge signal gradually increases as shown in Figure a, but the rate of pressure change is below the specified value, so the pressure change rate monitoring circuit outputs is not activated, and therefore only the pressure alarm generator is activated and the shutoff valve 7 is automatically closed. However, as shown in Figure 7, which shows the operation of each component in the event of a detector failure (high reading abnormality), the pressure gauge signal rises rapidly due to the detector failure, and the pressure alarm generator and pressure change The rate monitoring circuits will operate almost simultaneously. However, within the time set by the timer, the signal from the pressure change rate monitoring circuit prevents the signal from the pressure alarm generator from being transmitted to the downstream.
The opening valve 7 is not closed and remains open.

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. Among these, there are many failure modes in which a failure in the pressure receiving section gradually changes the indicated value, and there are many modes in which failure in the amplifier section causes a sudden change in the output signal. Therefore, detection of a detector failure in the present invention is for an amplifier failure,
This means that there is no protection against a failure of the pressure receiver that causes the indicated value to gradually change. However, if the indicated value changes gradually, if the operator constantly monitors the indicated value behavior, it is possible to recognize an abnormality in the pressure detector before the automatic interlock operates, and take necessary countermeasures. This is not a particular problem as it can often be taught.

FIG. 8 also shows an example in which the control mode of the controller 6 is switched from automatic mode to manual mode in response to a signal indicating that the rate of pressure change is greater than the specified value.

As shown in Fig. 8, it is normally in automatic mode, and PID (comparison/integration/derivation) control is performed based on the difference between the pressure detector output and the specified value so that the pressure detector output reaches a predetermined specified value. The pressure regulating valve 4 is automatically controlled via the device 21. However, 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 the automatic mode to the manual mode by the manual setting device 22, and the abnormal pressure detector signal is It is designed to prevent automatic control by
Generally, when the pressure detector output increases, the pressure regulating valve 4 operates in the closing direction, and therefore the pressure in the pressure regulating tank 2 decreases. In many cases, it is sufficient for the operator to manually switch the mode for the first time when an alarm occurs when the rate of pressure change exceeds the specified value.

By the way, the pressure detector of the pressure adjustment tank 2, that is,
If a malfunction occurs in the pressure gauge 5, the pressure detector is maintained while eliminating the effects of the malfunction, but the pressure during this maintenance is not shown in Figure 1, but it is Since pressure gauges are also installed in the generator 1 and the gas usage equipment 3, the system will be operated under the instructions from these pressure gauges. However, by taking measures such as promptly replacing the malfunctioning part of the pressure detector with a spare part, the system can be restored to normal condition 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 the malfunction of the cutoff valve 7 due to a failure of the pressure gauge 5, and therefore it is possible to improve the operating rate of the plant.

Furthermore, although the probability of occurrence of equipment abnormalities such as cracks in tanks and piping is very small, the risk associated with the occurrence of equipment abnormalities is high, so protective measures are provided to prevent such occurrences. The probability of a malfunction occurring in the detector used to activate the protection means is usually higher than the probability of occurrence of equipment abnormality such as a crack, so protection against the above-mentioned high-risk abnormality reduces the operating rate of the equipment. According to the present invention, malfunctions due to detector failures can be detected early and easily, and protective measures can be prevented from operating, thereby reducing the probability of plant stoppage due to detector malfunctions and improving plant availability. It becomes possible to improve the

Note that the present invention is particularly effective when applied to a plant that is operated continuously for a long period of time and is difficult to restart. Further, although the present invention has been described with reference to vacuum equipment, the present invention is applicable not only to vacuum equipment but also to general equipment such as pressure vessels. For example, the present invention can also be applied to equipment such as a nuclear reactor plant, where the reactor vessel is normally maintained at high pressure and is operated, but where the reactor is automatically shut down when the pressure exceeds a specified value. is applicable. In nuclear reactor plants, redundancy is legally required for measurement circuits that directly protect the reactor, so the present invention is applied to measurement and control circuits in reactor auxiliary equipment that indirectly lead to reactor shutdown. If applied, the effect will be great.

〔Effect of the invention〕

As explained above, according to the present invention, when the rate of change of the output signal from the detector exceeds a predetermined value, it is assumed that the detector itself has failed, and the detector signal is subsequently disabled. This has the effect of reliably preventing malfunctions caused by the detector output in the event of a detector failure, thereby improving the operating rate of the plant.

[Brief explanation of drawings]

FIG. 1 is a diagram showing vacuum equipment as an example of a system to which the present invention is applicable, FIG. 2 is a diagram showing an interlock in a protection control device according to the prior art, and FIG.
FIG. 4 shows a measuring circuit according to the prior art, FIG. 4 shows a measuring circuit including means for monitoring the rate of change of a detector output signal, which is a component of the present invention, and FIG. 5 shows a protection control according to the present invention. Figures 5a to 5c are diagrams showing the interlocks in the device; Figures 5a to 5c are diagrams for explaining the functions of the circuit parts that make up the interlocks;
The figure is an explanatory diagram of the operation of each component device in the case of an abnormal air leak in the embodiment of the present invention shown in FIGS. 4 and 5, and FIG. 7 is an explanatory diagram of the operation of each component device in the case of a detector failure. FIG. 8 is a diagram for explaining automatic mode switching of the controller based on the pressure change rate set value. 5... Pressure gauge as a detector, 11... Pressure transmitter, 12... Pressure alarm generator, 13... Rate of change monitoring circuit.

Claims (1)

[Claims] 1. By comparing the output value from the detector that measures the process amount with a specified value using a comparator, the comparator can automatically perform a protective operation when the output value deviates from the specified value. In a protection control device that outputs a protection control signal, the protection control signal from the comparator can be passed through a timer and a gate circuit, and the output value from the detector can be passed through a differentiator to the comparator to output the detector output from the setter. A protection control device characterized in that the gate circuit is gate-controlled based on a detector failure signal as a judgment result holding output obtained from the comparator in the event of a detector failure by comparing the rate of change.