JPS60211175A - Valve opening control device of pneumatic regulating valve - Google Patents

Abstract

PURPOSE:To prevent a lowering of a valve lift of a regulating valve due to a lowering of control air pressure by keeping the control air pressure in a diaphragm chamber as it was before during a fixed time after receivers a switch signal from an abnormality diagnosis device. CONSTITUTION:When an abnormality diagnosis device 17 detects abnormality, and a switching device 15 is switched according to a switch signal 18a, a valve opening command signal 14 is supplied to an emergency electropneumatic converter 30a. If a switch valve 13 and an emergency booster relay 30c are kept as they are cut off by a cutoff valve 40 during a time T after sending the switch signal 18a, even at the time of switching, the air pressure in a diaphragm chamber 12 is not discharged to the outside through the emergency booster relay 30c, but kept as it is to prevent a lowering of a valve lift of a regulating valve 11 caused by switching.

Description

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

FIG. 1 shows a diagrammatic system diagram of an example of a conventional device of this type. In FIG. diaphragm chamber 1.
Its valve lift is adjusted depending on the air pressure in 2. 20
is a regular pneumatic control device consisting of a regular electro-pneumatic converter 20α, a regular positioner 20b, and a regular booster relay 201-. 30 is an emergency pneumatic control device, and an emergency electro-pneumatic converter 3
0α, an emergency positioner 30h, and an emergency booster relay 300. Reference numeral 17 denotes an abnormality diagnostic device which transmits a switching signal 18α when detecting an abnormality in the regular or emergency air pressure control devices 20 and 30. 15 is a switching device which receives a switching signal 18α from the abnormality diagnostic device 17 and outputs a valve opening command signal 1.
4 to either the regular air pressure control device 20 or the emergency air pressure control device 30, the emergency air pressure control device 3o
The control air pressure output from the diaphragm chamber 12 is supplied to the diaphragm chamber 12.

During normal operation, the electrical valve opening command signal 14 supplied from the outside is sent to the regular electro-pneumatic converter 20α via the switch 15, where it is converted into a pneumatic signal.

The 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 sent to the regular positioner 2ob, and in the regular positioner 20b, the relationship with the valve lift signal of the control valve 11 supplied thereto is expressed by the following formula L=aP-1-b (where a and b are It is adjusted to satisfy the constant> and output to the regular booster relay 200.The regular booster relay 200 increases this pressure and outputs it as control air pressure.This control air pressure is passed through the switching valve 13 to the diaphragm chamber. 12.

If the air pressure in the diaphragm chamber 12 becomes high, the control valve 1
The valve lift of the control valve 11 increases, and as the air pressure in the diaphragm chamber 12 decreases, the valve lift of the control valve 11 decreases, and there is a gap between the valve lift and the valve opening command signal 14 as shown in FIG. A linear function relationship holds true.

The valve lift signal and valve opening command signal 14 are sent to the abnormality diagnostic device 1.
7, and it is determined here whether or not the relationship between the two has deviated from the allowable change range indicated by diagonal lines in FIG. When the deviation occurs, a switching signal 18a is output from the abnormality diagnostic device 17 to the switching valve 13 and the switching device 15, and the switching signal 18α switches the switching valve 13 and the switching device 15, and the switching signal 18a is outputted from the abnormality diagnostic device 17 to the switching valve 13 and the switching device 15. Control valve 1 by the control air pressure
1 is controlled. That is, the valve opening command signal 14 is transmitted to the switching device 15.
The air pressure is sent to the emergency electro-pneumatic converter 3oα through the emergency acid positioner 30b and the emergency booster relay 3oc.
VC supplied.

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.

In order to solve the above-mentioned problems, the present invention attempts to prevent fluctuations in the valve lift of the control valve when switching the switching valve 13 and the switching device 15. Abnormalities in the control valve whose valve lift is adjusted accordingly, the normal air pressure control device and the emergency air pressure control device that receive the valve opening command signal and output the corresponding control air pressure, and any of the above air pressure control devices. an abnormality diagnostic device that issues a switching signal when detecting the abnormality diagnostic device; and upon receiving the switching signal from the abnormality diagnostic device, the valve opening command signal is switched to either the normal air pressure control device or the emergency air pressure control device and manually operated. a switching device; and a switching valve that receives a switching signal from the abnormality diagnostic device, switches either the control air pressure output from the normal air pressure control device or the emergency air pressure control device, and supplies the controlled air pressure to the diaphragm chamber. Valve opening of an air-operated control valve, characterized in that it is provided with a pressure maintenance device that receives a switching signal from the abnormality diagnostic device and thereafter maintains the control air pressure in the diaphragm chamber as before for a certain period of time. Located in the control device.

In the present invention, upon receiving switching No. 48 from the abnormality diagnostic device,
After that, we installed a pressure maintenance device that maintains the control air pressure in the diaphragm chamber as before for a certain period of time, so the valve lift of the control valve due to the decrease in control air pressure in the diaphragm chamber that occurs immediately after the switching valve and switching device is switched. can prevent a decline in Then, at the time when the pneumatic pressure control device which has been switched after a certain period of time outputs the control pneumatic pressure corresponding to the valve opening command signal, the valve lift of the control valve can be adjusted by this pneumatic pressure control device.

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

In FIG. 5, reference numeral 40 denotes a shutoff valve that is interposed in the control air flow path from the emergency booster relay 300 to the switching valve 13. 41 is a signal delay device which, when receiving the switching signal 18α, sends a delayed switching signal 18b delayed by a certain period of time T to the shutoff valve 40 to open it, as shown in FIG. That is, the shutoff valve 40 is fully closed during normal operation, but becomes fully open when it receives the delayed switching signal 18A.

During normal operation, when the valve lift of the control valve 11 is controlled by the regular pneumatic pressure regulator 20, the valve opening command signal 14 is manually input to the regular electro-pneumatic converter 20α by the switch 15, and the emergency electro-pneumatic converter is used. It is not input to the device 30α. Therefore, since the output of the emergency electro-pneumatic converter 30α and the output of the emergency positioner 30b 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 and switches the switch 15 using the switching signal 18α, the valve opening command signal 14 is supplied to the emergency electro-pneumatic converter 30α, but is also supplied to the emergency booster relay 300 as a pneumatic signal. Immediately after switching, the emergency booster relay 30
The 0 output is atmospheric pressure, and there is a delay until the pressure reaches the pressure corresponding to the valve opening command signal 14. Therefore, if there is no cutoff valve 40, the air pressure in the diaphragm chamber 12 will temporarily decrease during switching, and the valve lift of the control valve 11 will temporarily decrease.

However, after the switching signal 18α is transmitted by the shutoff valve 40, T
If the switching valve 13 and the emergency booster relay 30'C are kept shut off for a certain period of time, the air pressure inside the diaphragm ridge 12 will not be released to the outside through the emergency booster relay 300 even during switching. , is maintained as it is, so 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 300 reaches the pressure corresponding to the opening command signal 14 with a slight delay after the switching of the switching valve 1.3, so the output of the emergency booster relay 300 reaches the pressure corresponding to the opening command signal 14 after switching of the switching valve 1.3.
By opening the valve 0, the emergency air pressure control device 30
Write control can be started by

Therefore, it is possible to switch from the regular pneumatic pressure control device 20 to the emergency pneumatic pressure control device 30 without causing unnecessary disturbance to the plant at the time of switching. The other structures and operations are similar to those shown in FIG. 1, and corresponding parts are designated by the same reference numerals.

A second embodiment of the present invention is shown in FIG. 7, in which a cutoff valve 50 is interposed in the control air flow path between the switching valve 13 and the diaphragm chamber 12. 51 is a signal holder which, when receiving the switching signal 18α, transmits a cutoff signal 18h to the cutoff valve 50 for a certain period of time T to cut it off, as shown in FIG. That is, the shutoff valve 50 is fully open during normal operation, and the temperature
- Fully closed when receiving the shutoff signal 18h.

Then, the abnormality diagnostic device 17 detects an abnormality and the switching signal 18
After transmitting α and switching the switching valve 13 and switching device 15, the emergency booster relay 307? By closing the shutoff valve 50 for a time T until the output from the valve becomes the control air pressure corresponding to the valve opening command signal 14, the pressure inside the diaphragm 12 is maintained as it is, and the valve lift of the control valve ii is temporarily increased. After the output of the emergency booster relay 30C reaches the control air pressure corresponding to the valve opening command signal 14, the shutoff valve 50 is opened and the emergency air pressure control device 30 lifts the control valve 11. control. In this way, when switching from the regular pneumatic pressure control device 20 to the emergency pneumatic pressure control device 30, a temporary decrease in the valve lift of the control valve 11 is prevented and no unnecessary disturbance is caused to the plant. The other configurations and functions are the same as those shown in FIG. 1, and corresponding parts are given the same reference numerals.

In the above embodiment, when switching from the regular air pressure control device to the emergency air pressure control device, the control air pressure in the diaphragm chamber is maintained as it is for a certain period of time.
Even when switching from the emergency air pressure control device to the regular air pressure control device, the control air pressure in the diaphragm chamber can be maintained as it is for a certain period of time. Further, the valve opening command signal is not limited to an electrical one, but may be a mechanical or liquid one.

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 may be made without departing from the spirit of the present invention). be.

[Brief explanation of the drawing]

1 to 4 show an example of a conventional valve opening control device for an air-operated control valve.
The figure shows the valve opening command signal and the air output from the electro-pneumatic converter.
Figure 3 is a diagram showing the relationship between the valve opening command signal and the valve lift of the control valve. Figure 4 is a diagram showing the relationship between the valve opening command signal and the valve lift of the control valve. FIG. 5 and 6 show a first embodiment of the present invention, FIG. 5 is a diagrammatic system diagram, and FIG. 6 is a diagram showing the relationship between the switching signal and the time of the delayed switching signal. 7 and 8 show a second embodiment of the present invention, and FIG.
The figure is a diagrammatic system diagram, and FIG. 8 is a diagram showing the relationship between the switching signal and the cutoff signal time. 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
) Pressure maintenance device...40,41゜50.51 Sub-Agent Patent Attorney Kaihon Important Papers 17 Figure 5 Between Numbers 6 and 8 Figure Between Words 7

Claims (1)

[Claims] A control valve whose valve lift is adjusted according to the control air pressure in the diaphragm chamber, a regular 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 any of the above. an abnormality diagnostic device that transmits a switching signal when detecting an abnormality in the pneumatic pressure control device, and a valve opening command signal that is sent to the normal pneumatic pressure control device or the emergency pneumatic pressure control device upon receiving the switching signal from the abnormality diagnostic device. A switching device that switches to input the control air pressure to either the normal air pressure control device or the emergency air pressure control device in response to a switching signal from the abnormality diagnostic device, and switches the control air pressure output from the normal air pressure control device or the emergency air pressure control device to the diaphragm chamber. A pneumatic actuator equipped with a switching valve for supplying the air, characterized in that it is equipped with a pressure maintenance device that receives a switching signal from the abnormality diagnostic device and then maintains the control air pressure in the diaphragm chamber as before for a certain period of time. Valve opening control device for type control valves.