JPS60139901A - Air-operated control valve control unit - Google Patents

Abstract

PURPOSE:To prevent wrong diagnosis by providing a judging unit which sets a time constant in accordance with the deviation value between the control valve opening command and the lifted amount of the valve, executes the primary delay processing to the opening command according to the time constant, and finally judges the generation of abnormal condition when the deviation value between the processed command signal and the lifted amount of the valve exceeds a prescribed value. CONSTITUTION:In a device wherein the amount of the opening of a control valve 20 is controlled by a diaphragm device 21 supplied with the pressurized air from an air pressure control mechanism 23 in accordance with a valve opening command signal 24, provided is an abnormality diagnosing device 27 which is input with the valve opening command signal 24 and a valve lift signal 26 detected by a valve lift meter. The abnormality diagnosing device 27 comprises a deviation detector 100 which detects the deviation value between the signals 24, 26, a time constant setting device 101 which sets a time constant in accordance with the deviation output, and a primary delay processing circuit 102 which executes the primary delay processing to the valve opening command signal 24 using the time constant. When the deviation value between the output signal from the primary delay processing circuit 102 exceeds the prescribed value, the judging unit 103 judges the generation of an abnormal condition.

Description

[Detailed description of the invention] TECHNICAL FIELD This invention relates to an improvement in a pneumatically actuated control valve control system.

As an example of a conventional air-operated control valve control device, there is a one-to-one relationship between the opening command signal and the valve lift signal of the air-operated control valve.
Some systems utilize the existence of this relationship to monitor the deviation between the opening command signal and the valve lift signal, and determine that there is an abnormality when the deviation exceeds a set value. However, the valve has a delay in operation, and even if it is normal, a deviation occurs temporarily.

Figure 1 shows the relationship, where a is the opening command signal, b
indicates the valve lift signal.

For this reason, in order to avoid misdiagnosis, the conventional configuration has been to increase the set value, but if a failure occurs, there will be a delay in detecting the failure.

The present invention has been made to solve these problems, and an object of the present invention is to provide an air-operated control valve control device that can quickly detect failures without causing erroneous valve diagnosis.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a schematic diagram showing an embodiment of the apparatus of the present invention. Reference numeral 20 denotes a control valve for adjusting the flow rate of a desired fluid, and this control valve 20 can be opened by a predetermined opening degree by a diaphragm 2 provided in a diaphragm chamber (not shown). The Guyafram 21 is configured to be supplied with pressurized air according to an opening command signal 24 of the control valve 20 from an air pressure control mechanism 23 to be described later. The opening command signal 24 is supplied not only to the air pressure control mechanism 23 but also to an abnormality diagnostic device 27, which will be described later. The pneumatic control mechanism 23 includes an electropneumatic converter 23a1 and a positioner 23b1.
The booster is made up of -23c. diaphragm 2
The valve lift signal 26 which is the outlet of 1 is detected by a lift meter, and this detected valve lift signal 26 is sent to the abnormality diagnostic device
is being supplied to. On the other hand, valve lift signal 2
6 is connected to the positioner via a feedback link 22.
23b.

As shown in the third drop, the abnormality diagnostic device 27 includes a deviation detector 100, a time constant setter 101, and a first-order delay circuit 102.
, from the determiner 103)1. child? (2) The valve lift signal 26 and opening command signal 24 supplied to the abnormality diagnostic device 27 are input and calculated to diagnose the presence or absence of an abnormality.

Hereinafter, the operation of the air-operated control valve control device configured as described above will be explained. The opening degree control of the control valve 20 is performed as follows.

Normally, the opening degree is adjusted using the opening command signal 2, which is supplied from the outside.
4 is converted into an air signal by an electro-pneumatic converter 23h. In a steady state, the relationship between this air pressure signal and the opening command signal 24 is a linear function as shown in FIG. The positioner 23b operates the control valve lift □ and outputs the pneumatic pressure signal p,
@.

When b is a constant, it is adjusted to satisfy the following equation (1).

L=aP+b・・・・・・・・・(1)Here L)
If a P + b, increase the outlet air pressure of the positioner 23b, and increase the positioner 23b if L (ap + b),
The outlet air pressure of 23b is lowered. Booster relay 23a is an amplifier to ensure that the diaphragm pressure matches the outlet pressure of positioner 23b. If the diaphragm pressure is higher than the outlet pressure of the positioner 23b, the air inside the diaphragm 21 is exhausted to the atmosphere and the pressure of the diaphragm 21 is lowered. Moreover, if the pressure of the diaphragm 21 is low, air is pumped into the diaphragm 2''1.

If the diaphragm 21 is "high pressure" the valve lift signal 26 will rise and if the fire is low the valve lift signal 26 will fall. In this way, a linear function relationship as shown in FIG. 5 is established between the positioner 23b valve lift signal 26 and the opening command signal 24.

Now, supplying and exhausting the required amount of air to the diaphragm 2) by the booster relay 23c is not instantaneous and takes time. Therefore, when the opening command signal 24 changes, the diaphragm pressure will have a time lag. This means that the valve lift signal 26 satisfies the relationship shown in Figure 5 with some time delay.

When stopping, the time delay with respect to the valve lift signal 2''6 (D'opening command signal '24) can be described as a '1st-order lag as shown in FIG. In order to cope with the case where the opening command signal 24 changes, the signal passed through the first-order delay processing circuit 102 and the valve valve position signal 26 are compared. The amount of air supplied to the diaphragm 21 and the amount of air exhausted from the diaphragm 21 are different, and therefore, the time delay in the opening direction and the time delay in the closing direction of the valve lift signal 26 are also different. Figure 7 shows the relationship.

Therefore, when the opening command signal 24 increases, that is, when the valve lift signal 26 is in the opening direction, and when the opening command signal 24 decreases, that is, when the valve lift signal 26 is in the closing direction, the first order in FIG. The time constant of the delay processing circuit 1θ2 must be changed. Here, when the opening command signal 24' is increasing, the deviation obtained by subtracting the valve lift signal 26 from the opening command signal 24 is a positive value, and when the opening command signal 24- is decreasing, the deviation is negative. The value is . Therefore, the first-order delay processing circuit 10
The time constant 2 may be set based on the sign of the deviation.

The deviation detector 100 of the abnormality diagnostic device 27 shown in FIG. 3 calculates the deviation obtained by subtracting the valve lift signal 26 from the opening command signal 24.If the deviation is positive, the deviation is in the increasing direction.If the deviation is negative, the deviation is in the decreasing direction. The time constant setter 6-101 receives the signal from the deviation detector 100 and sets the time constant T1 if the signal is increasing, and sets the time constant T2 if the signal is decreasing. The first-order delay processing circuit 102 is a time constant setter 10
1 to the opening command signal 24 using the time constant set in
Perform next delay processing. The determiner 103 is the first-order delay processing circuit 1
If the difference between the output of 02 and the valve lift signal 26 is within a specified value, it is determined to be normal, and if it exceeds the specified value, it is determined to be abnormal. In FIG. 8, the shaded area is a normal area, and the other areas are areas determined to be abnormal.

According to the present invention described above, a deviation detector detects a deviation between an opening command signal and a valve lift signal of an air-operated control valve;
A time constant setter that receives the output signal from the deviation detector and sets a predetermined time constant; and a first-order lag process that performs first-order lag processing on the opening command signal using the time constant of the time constant setter. Since the configuration includes a circuit and a determiner that determines an abnormality when the deviation between the output signal of the first-order delay processing circuit and the valve lift signal exceeds a specified value, abnormality diagnosis can be performed using conventional equipment. It is possible to provide an air-operated control valve control device that is more accurate than the previous one and does not cause misdiagnosis.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the opening command signal and valve lift signal of a conventional air-operated control valve control device, and FIG. 2 is a schematic configuration diagram showing an embodiment of the air-operated control valve control device of the present invention. Figure 3 is a schematic diagram of the abnormality diagnostic device shown in Figure 2, Figures 4 and 5.
The figures are a characteristic diagram showing the relationship between the opening command signal and the outlet air pressure of the electro-pneumatic converter and a characteristic diagram showing the relationship between the opening command signal and the valve lift signal to explain the operation of the same embodiment. 7 is a diagram showing the relationship between the valve lift signal and the opening command signal to explain the operation of the same embodiment, and FIG. 8 is the output of the first-order delay processing circuit to explain the operation of the same embodiment. It is a figure showing the relationship between a signal and a valve lift signal. 20...Control valve, 21...Diaphragm, 22...
・Feedback link, 23...pneumatic control mechanism,
23a...Electro-pneumatic converter, 23b...Pososhota, 2
3c...Booster relay, 24...Opening command signal,
26... Valve lift signal, 27... Abnormality diagnostic device, 33
... Valve lift meter, 100 ... Deviation detector, 101.
・・Time constant setter, 102 ・・1st order lag processing circuit, 1
03... Judgment device. Applicant's sub-agent Patent attorney Takehiko Suzue = 9- Bacteria 4 Figure 6 Figure 57i Time Figure 7 Continued from page 1 1 5-

Claims (1)

[Claims] a deviation detector that detects the deviation between the opening command signal and the valve lift signal of the air-operated control valve; a time constant setting device that receives the output signal from the deviation detector and sets a predetermined time constant; a first-order lag processing circuit that performs first-order lag processing on the opening command signal using a time constant of a constant setting device; and a deviation between the output signal of this first-order lag processing circuit and the valve lift signal that exceeds a specified value. A pneumatic control valve control device equipped with a determination device that determines that something is abnormal.