JPH0210401A - Process controller - Google Patents

Abstract

PURPOSE:To inexpensively and stably control a process by monitoring adjusting valve opening degree signals of both of first and second systems and temporarily stopping switching of a process variable in case of the variation of the process variable larger than a prescribed value. CONSTITUTION:In a controller of the process variable (for example, a water level), water level signals of water level transmitters 1 and 2 of first and second systems and opening degree signals of electric valves 7-10 before and after water adjusting valves of first and second systems are inputted to a water level controller 15, and respective water level adjusting valves 14 and 15 are controlled through water level electro-pneumatic transducers 5 and 6. With respect to the switching method of water level control systems, when the water level variation is larger than a preliminarily determined value or the detected water level reaches a water level rise alarm set value 62 or the detected water level reaches a water level reduction alarm st value 63 while the adjusting valve 14 of the second system is gradually opened, this gradual opening operation is temporarily stopped and its position is kept with a signal generator 57 by a changeover switch 56. The control is continued after release of this stop.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a process control device, and particularly to a process control device that enables stable process amount switching control.

[Conventional technology]

A conventional water level control switching method consisting of two lines will be explained with reference to FIG. Figure 3 shows water supply pump 13.12 to water tank 11.
This shows a water supply system. In the figure, 1 is a water level transmitter, 3 is a water level controller, 5 is an electro-pneumatic converter, 15 is a water level adjustment valve, 7 is a front valve of the water level adjustment valve, and 8 is a rear valve of the water level adjustment valve. 2.4.6, 14, 9 and 10 are devices corresponding to the codes 1, 3.5, 15, 7 and 8 of the second system. In this figure, the first system is currently in operation and the second system is on standby as a backup.

The procedure for switching the water level control system from the first system to the second system will now be described. First, the second system water level adjustment valve front and back valves 9 and 10 on the standby system side are fully opened, and the water level controller 4 of the second system is gradually opened in manual mode to gradually open the water level adjustment valve 14. At this time, the water level controller 4 of the second system must be operated slowly so that the water level of the water tank 11 does not generate a high water level alarm or a low water level alarm. Second system water level adjustment valve 1
4 opens, the water level adjustment valve 15 of the first system gradually closes under the automatic control of the water level controller 3 of the first system, and the opening degree of the water level adjustment valve of the first system and the opening degree of the second system water level adjustment valve are changed. When the levels are almost the same, the second system water level controller 4 is switched to automatic mode. Then, the first system water level controller 3 is switched to manual mode, and the first system water level adjustment valve 15 is gradually narrowed down. When the valve 15 is fully closed, the front and rear valves 7 and 8 are fully opened to complete the series of operations, and the water level switching control is completed.

[Problem to be solved by the invention]

The above-mentioned conventional technology requires a lot of effort and stress on the operator because it takes time to perform the switching operation. Also, fluctuations in the process (water level, flow rate, pressure, temperature) may occur due to individual differences among operators.
There were sizes. An object of the present invention is to be able to configure a simple system, provide inexpensive, and stable process control.

[Means to solve the problem]

In order to achieve the above object, the present invention monitors the regulating valve opening signals of both the first system and the second system.
When the rate of change (water level, flow rate, pressure, temperature) becomes greater than a predetermined value, (b) the set process amount (water level, flow rate, pressure).

This is accomplished by temporarily stopping the switching control when the temperature (temperature) reaches a high (or low) alarm value, and restarting the control when the condition disappears.

〔Example〕

An embodiment of the present invention will be described below. The present invention is a control device for process quantities (water level, flow rate, pressure, temperature), and will be explained using a water level control device as an example. FIG. 2 shows an input/output system diagram from the mechanical system necessary for the present invention. The water level control device 15 according to the present invention includes a water level signal of the first system water level transmitter 1, a water level signal of the second system water level transmitter 2, 1!
Opening signals of the activated front and rear water level adjustment valves 7 and 8,
The opening signals of the front and rear water level adjustment valves 9 and 10 of the second system water level adjustment valve are respectively inputted, and are also input to each of the water level adjustment valves 15 through the first system water level electro-pneumatic converter 5 and the second system water level electro-pneumatic converter 6. .14 is controlled.

FIG. 1 shows a control block diagram according to the invention.

This figure currently shows that the first system regulating valve 15 is in operation and the second system regulating valve 14 is on standby.The method for switching the water level control system from the first system to the second system will be explained below. . By pressing the regulating valve changeover switch 29, the front and rear valves 9, 10 of the second system regulating valve 14 are fully opened. By fully opening these 1 valves 9 and 10, a gradual opening signal 60 to the regulating valve 14 is created.
As a result, the signal of the second system controller 4 is transmitted to the gradual opening signal generator 53.
The signal is switched to B-+C by the signal changeover switch 52, and the regulating valve 14 is gradually opened. As the second system regulating valve 14 gradually opens, the first system regulating valve 15 gradually closes due to the automatic adjustment function. And a valve opening request signal 37.6 for the image adjustment valve.
5 become the same, the second system regulating valve gradual opening signal 60 is switched by the changeover switch 52, and the control system is set to automatic mode A.
−+C, and for the − system, the regulating valve gradual closing signal 31
As a result, the control system is set to gradual closing mode B-+C by the changeover switch 24, and the first system regulating valve 15 is fully closed by the signal from the gradual closing signal generator 25.

The above means that the normal control system has been switched from the first system to the second system control system. However, in normal switching, if the switching rate is too fast, the other automatic control system may not be able to follow up and an alarm may be generated. In FIG. 1, the second system regulating valve 14
(b) When the rate of change in water level becomes larger than a predetermined value 64, (b) Water level detection 51
When reaches the water level high alarm set value 62, (c) Water level detection 5
0 reaches the low water level alarm set value 63, the gradual opening operation is temporarily stopped and the signal generator 57 is activated by the changeover switch 56.
When the signal is released, the control is continued again. 15 is a control block diagram showing one embodiment of the present invention. This system can be easily configured by applying microprocessor technology.

In the embodiment, a case has been described in which water level is used as a process quantity, but a similar process control system can be constructed also in the case of flow rate, pressure, and temperature.

〔Effect of the invention〕

According to the present invention, operators can be relieved from the burden of conventional process control switching operations, which require a great deal of effort and tension.

[Brief explanation of the drawing]

Claims (1)

[Scope of Claims] 1. In a process control device which is provided in two series and includes a process amount adjusting valve and valves before and after the process amount adjusting valve, the first one which is currently stopped is operated by operating the adjusting valve changeover switch. Create a gradual opening signal by fully opening the front and rear valves of the series process amount regulating valve, gradually opening the first series process quantity regulating valve in a ramp shape, and generating an opening signal of the first series process quantity regulating valve; On the condition that the opening signal level of the second series process amount regulating valve which is about to be stopped becomes the same, the first series process quantity regulating valve is put into automatic mode, and on the other hand,
The first series process amount adjustment valve is gradually closed in a ramp shape,
A process control device characterized in that the front and rear valves of the second series process amount adjustment valve are fully closed. 2. In claim 1, when the rate of change of the process quantity becomes greater than a preset rate of change, or when the process quantity reaches a high alarm generation set value, or when the process quantity When the low alarm set value is reached, the ramp-like opening operation of the process amount adjustment valve is stopped, and the opening degree of the process amount adjustment valve is maintained at that position;
A process control device that is characterized in that it opens or closes again when these conditions disappear.