JPS60252882A - Control device of valve opening in pneumatically operated adjusting valve - Google Patents

Abstract

PURPOSE:To prevent an adjusting valve from changing its valve lift, by providing a signal delaying device between an abnormality diagnostic device and a selector valve while a shut off valve, blocking the air pressure, between an air pressure control device and the selector valve, in the case of a control device of valve opening in the pneumatically operated adjusting valve. CONSTITUTION:A signal delaying device 41 is provided between an abnormality diagnostic device 17 and a selector valve 13, outputting a switching signal with a delay. While a shut off valve 40, being interposed between an air pressure control device 20 and the selector valve 13, is operated when the switching signal is received from the abnormality diagnostic device 17. Accordingly, an adjusting valve can be prevented from decreasing its valve lift by enabling pressurized air in a diaphragm chamber to be maintained.

Description

[Detailed description of the invention] The present invention relates to a valve opening control device for an air-operated control valve.

FIG. 3 shows a diagrammatic system diagram of an example of a conventional device of this kind. In FIG. The diaphragm chamber 1
The valve lift is increased or decreased depending on the level of air pressure inside the valve. 20 is a regular air pressure control device, and a regular electro-pneumatic converter 2 (D,
It consists of a regular positioner 20h and a regular booster relay 20C. Reference numeral 30 denotes an emergency pneumatic control device, which includes an emergency electro-pneumatic converter 30a, an emergency positioner 30b, and an emergency booster relay 30C. 17 This is an abnormality diagnostic device that transmits a switching signal 18a when an abnormality in the regular air pressure control device 20 is detected. 15 is a switching device which receives a switching signal 18α from the abnormality diagnostic device 17 and sends the valve opening command signal 14 to either the electro-pneumatic converter 20a or 30α of the regular pneumatic pressure control device 20 or the emergency pneumatic pressure control device 30. Switch and input.

13 is a switching valve, which receives a switching signal 18α from the abnormality diagnostic device 17.
In response, either the control air pressure output from the booster relay 20C or 30C of the regular air pressure control device 20 or the emergency air pressure control device 30 is supplied to the diaphragm chamber 12. The valve lift signal 16 of the control valve 11 is input to the regular positioner 20h, the emergency positioner 30b, and the abnormality diagnostic device 17.

During normal operation, the electrical valve opening command signal 14 supplied from the outside is sent via the switch 15 to the regular electro-pneumatic converter 20α, where it is converted into a pneumatic signal PK. This air pressure signal P
and the valve opening command signal 14 have a linear function relationship as shown in FIG. This air pressure signal P is transmitted to the regular positioner 20.
If the valve lift signal 16 of the control valve 11 that is sent to the control valve 11 and supplied to the regular positioner 20b is L, then L
The relationship is the following formula L = αP + 6 (where α and S are constants)
The commonly used booster relay 20 is adjusted to satisfy the
Output to C. In the regular booster relay 20c, this is adjusted and output as control air pressure. This control air pressure is supplied into the diaphragm chamber 12 via the switching valve 13. Thus, if the pressure inside the diaphragm chamber 12 is higher than the outlet pressure of the regular positioner 20b, the regular booster relay 2oC exhausts the air inside the diaphragm chamber 12 to the atmosphere to lower the pressure inside the diaphragm chamber 12, and also lowers the pressure inside the diaphragm chamber 12. If the pressure is lower than the outlet pressure of the regular positioner 2 (l), air is sent into the tweeter flamm chamber 12.

If the air pressure in the diaphragm chamber 12 becomes high, the control valve 1
If the air pressure in the diaphragm chamber 12 becomes low, the valve opening 7 of the control valve 11 will become small. A linear function relationship as shown in the figure is established. Valve lift signal 16
and the valve opening command signal 14 are supplied to the abnormality diagnostic device 17,
Here, it is determined whether the relationship between the two deviates from the allowable change range indicated by diagonal lines in FIG. When a deviation occurs, that is, when an abnormality in the normal air pressure control device is detected, the abnormality diagnostic device 1
The switching signal 111E2 from 7 to the switching valve 13 and switching device 15
This switching signal 18α causes the switching valve 13 and the switching device 15 to switch, and the emergency air pressure control device 3
The control valve 11 is controlled by the control air pressure from zero.

That is, the valve opening command signal 14 is sent via the switch 15 to the emergency electro-pneumatic converter 30cLK f, the emergency positioner 30b,
The control air pressure output via the emergency booster relay 30C is supplied to the diaphragm chamber 12 via the switching valve 13.

In the above device, when switching the switching valve 13 and the switching device 15, the valve lift of the control valve 11 temporarily decreases, which may cause disturbance to the plant. That is, when the valve opening of the control valve 11 is controlled by the regular air pressure control device 20, the opening command signal 14 is input to the emergency electro-pneumatic converter 30α, and therefore the emergency electro-pneumatic converter The outputs of the booster 30α and the emergency positioner 30b are both zero, and the control air pressure output from the emergency booster relay 30C is atmospheric pressure. At that time, when the switching signal 18α is output from the abnormality diagnostic device 17, the switching valve 13 and the switching device 15 are switched simultaneously, but the opening command signal 14 is transmitted to the emergency electro-pneumatic converter 30α, the emergency positioner 30b, the emergency Since it takes time for the corresponding control air pressure to be output via the emergency booster relay 30C, the control air pressure output from the emergency booster relay 3 (C) remains at atmospheric pressure immediately after switching the switching valve 13. Therefore, the diaphragm chamber 12
Since the pressurized air inside is released into the atmosphere through the emergency booster relay 30C, the valve lift of the control valve 11 is temporarily reduced, which may cause disturbance to the plant.

In order to deal with the above-mentioned problem 9, the present invention switches the switching valve 13 and the switching device 15, and changes the valve lift of the control valve when changing the control by the regular air pressure control device to the control by the emergency air pressure control device K(j11!D). This is intended to prevent fluctuations, and its gist is a control valve that adjusts the valve lift according to the control air pressure in the diaphragm chamber, and a control air pressure that responds to the valve opening command signal. a normal pneumatic pressure control device and an emergency pneumatic pressure control device that output a normal pneumatic pressure control device, an abnormality diagnostic device that outputs a switching signal when an abnormality is detected in the normal pneumatic pressure control device, and a valve opening degree that is determined in response to a switching signal from the abnormality diagnostic device. a switching device that switches and inputs a command signal from the regular air pressure control device to the emergency air pressure control device;
a switching valve that receives a switching signal from the abnormality diagnostic device and switches the control air pressure output from the normal air pressure control device to the control air pressure output from the emergency air pressure control device, and supplies the control air pressure to the diaphragm chamber. In the things that
A signal delay device that delays a switching signal for a certain period of time is interposed between the abnormality diagnostic device and the switching valve, and a switching signal from the abnormality diagnostic device is received between the regular air pressure control device and the switching valve. The present invention provides a valve opening degree control device for an air-operated control valve, characterized in that a cutoff valve is installed to cut off the control air pressure output from the regular air pressure control device when the air pressure control device is operated.

In the present invention, the switching signal from the abnormality diagnostic device is delayed for a certain period of time via a signal delay device, and then output to the switching valve, and then output from the emergency air pressure control device. Delay switching of the switching valve until the corresponding value is reached. Then, by closing the shutoff valve in response to a switching signal from the abnormality diagnostic device, the control air pressure output from the normal air pressure control device is cut off, and the pressurized air in the diaphragm chamber is maintained as before. In this way, it is possible to prevent the valve lift of the control valve from decreasing due to a decrease in the control air pressure in the diaphragm chamber that occurs immediately after the switching valve and the switching device are switched. The valve lift of the control valve can be adjusted by the emergency pneumatic pressure control device at the point in time when the emergency pneumatic pressure control device, which has been switched after the light has passed for a certain period of time, outputs the control pneumatic pressure corresponding to the valve opening command signal.

The present invention will be specifically described below with reference to an embodiment shown in FIG.

In FIG. 1, a shutoff valve is installed in a control air flow path from a regular booster relay 200 to a switching valve 13 of a regular air pressure control device 20. In FIG. 41 is a signal delay device interposed between the abnormality diagnostic device 17 and the switching valve 13;
8α, as shown in FIG. 2, a delayed switching signal 18h delayed by a certain period of time T is sent to the switching valve 13 to switch it.

When the valve lift of the control valve 11 is controlled by the service pneumatic control device 20 during normal operation, the valve opening command signal 14 is inputted to the service electro-pneumatic converter 20α by the switching device 15, and the emergency electro-pneumatic It is not input to converter 30α.

Therefore, since the output of the emergency electro-pneumatic converter 30α and the output of the emergency positioner 30h are at atmospheric pressure, the output of the emergency booster relay 300 is also at atmospheric pressure.

When the abnormality diagnostic device 17 detects an abnormality in the regular air pressure control device 20 and switches the switch 15 according to the switching signal 18a, the valve opening command signal 14 is supplied to the emergency electro-pneumatic converter 30α. However, since there is a delay before the emergency booster relay 3oC outputs the corresponding control air pressure, the output of the emergency booster relay 300 is atmospheric pressure immediately after switching, and therefore this is the valve opening command. The switching valve 13 is not switched for a certain period of time T until the pressure corresponding to the signal 14 is reached, and the switching valve 13 is switched after this certain period of time T has elapsed. On the other hand, when the switching signal 18α is transmitted, the switching device 15
When the input to the regular use electro-pneumatic converter 20α is zero, the control air pressure of the regular use booster relay 200 becomes atmospheric pressure.
The switching valve 13 remains as before, so
There is a risk that the pressurized air in the diaphragm chamber 12 will be released from the regular booster relay 200, but the switching signal 18α
The shutoff valve 40 is closed at the same time that the
Since it is maintained as it is without being released to the outside through 0, it is possible to prevent the valve lift of the control valve 11 from decreasing due to switching.

The output of the emergency booster relay 30C is the switching signal 18α
Since the pressure corresponding to the opening command signal 14 is reached with a slight delay after the transmission of the switching valve 13, the emergency pneumatic pressure control device 3
Control can be started again by setting 0.

Therefore, when changing over, unnecessary disturbances are caused to the plant, and the VC
From the regular air pressure control device 20 to the emergency air pressure control device 30
It becomes possible to switch to The other structures and operations are similar to those shown in FIG. 1, and corresponding parts are designated by the same reference numerals.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. be.

[Brief explanation of the drawing]

One embodiment of the present invention is shown in FIGS. 1 and 2.
The figure is a diagrammatic system diagram, and FIG. 2 is a diagram showing the relationship between the switching signal and the delayed switching signal. 3 to 6 show an example of a conventional valve opening control device for an air-operated control valve.
The figure is a diagram showing the relationship between the valve opening command signal and the pneumatic signal output from the electro-pneumatic converter, and Figure 5 is a diagram showing the relationship between the valve opening command signal and the valve lift of the control valve. FIG. 6 is a diagram showing an allowable variation range between the valve opening command signal and the valve lift of the control valve. Control valve...11 Diaphragm...12 Regular air pressure control device...20 Emergency air pressure control device...30 Valve opening command signal...14 Switching signal...18α abnormality diagnostic device...17 Switching device...15 Switching valve...13
Signal delay device...41 Shutoff valve...40 Figure 1, Figure 3 (Foundation)

Claims (1)

[Claims] A control valve whose valve lift is adjusted according to the control air pressure in the diaphragm chamber, a normal air pressure control device and an emergency air pressure control device which receive a valve opening command signal and output a corresponding control air pressure, and the above-mentioned An abnormality diagnostic device that transmits a switching signal when detecting an abnormality in the normal air pressure control device, and upon receiving the switching signal from the abnormality diagnostic device, switches the valve opening command signal from the normal air pressure control device to the emergency air pressure control device. and a switching device that receives a switching signal from the abnormality diagnostic device to switch the control air pressure output from the normal air pressure control device to the control air pressure output from the emergency air pressure control device, and supplies the control air pressure to the diaphragm. A signal delay device that delays the switching signal for a certain period of time is interposed between the abnormality diagnostic device and the switching valve, and a signal delay device is interposed between the normal air pressure control device and the switching valve. A valve opening control device for an air-operated control valve, characterized in that a cutoff valve is installed to cut off the control air pressure output from the regular air pressure control device when receiving a switching signal from the abnormality diagnostic device.