JP2879470B2 - Control valve with flow meter function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to a valve which is attached to a piping system such as steam or compressed air to regulate a fluid pressure, a flow rate, a temperature, a humidity, etc. on a secondary side. It relates to a valve having a flow measurement function.

<Conventional technology> In general equipment, fluid is controlled by installing only a control valve in front of equipment using fluid, but ideally a flow meter is additionally provided to enhance productivity and quality control. It is desired to aim at. For example, when the fluid is steam, the productivity is often constantly controlled by grasping the steam flow rate to the steam-using device. In other words, they aim to produce more with less consumption of steam.

Therefore, as a conventional production system, a control valve and a flow meter are provided independently.

<Problems to be Solved by the Invention> In the above system, installation work is troublesome, and the equipment itself is very large. At the present time, the idea of mounting a flow meter first is not easily implemented due to cost considerations. When the flowmeter is of a differential pressure type, the orifice is fixed, so that the measurement range is small.

Therefore, the technical problem of the present invention is to provide a control valve,
At the same time, the purpose of the present invention is to provide a small and inexpensive device incorporating the function of a flow meter as a whole.

<Means for Solving the Problems> According to the technical means of the present invention taken to solve the above problems, the drive unit operates based on an operation output signal from the controller to open the valve to a desired position. The control valve that controls the flow rate of the fluid passing therethrough is provided with means for detecting the pressure on the primary side and the secondary side of the valve, respectively, and the controller has a valve opening change and a Cv value at that time. The storage unit in which the relationship is stored in advance, the Cv value is obtained from the stored relationship based on the valve opening corresponding to the operation output signal output by the controller, and the obtained Cv value and the pressure detection unit are used. And a calculating unit for calculating the flow rate of the fluid passing through the valve from the pressure value of the above.

<Operation> Generally, the flow rate of a fluid passing through a valve can be determined by knowing the Cv value of the valve and the pressures before and after the valve. Here, the Cv value is a flow rate when the fresh water of 15.6 ° C. is flowed while maintaining the differential pressure between the inlet and the outlet of the valve at 0.07 kg / cm ² , in US gal / min.

Since the operation output signal (opening instruction signal) output from the controller to the valve and the opening of the valve driven and displaced by the signal are substantially equal, the opening of the valve can be known by the controller. Therefore, the Cv value corresponding to the valve opening commanded by the controller to the drive unit is obtained from the relationship between the valve opening and the Cv value stored in the controller. On the other hand, data is constantly input to the controller from the pressure detectors provided on the primary side and the secondary side of the valve, and the flow rate can be calculated from the value and the obtained Cv value.

<Example> An example showing a specific example of the above technical means will be described.

(See FIGS. 1 and 2) In this embodiment, a flowmeter function is added to a control valve for adjusting the pressure on the secondary side to a desired pressure. FIG. 1 shows an air-driven control valve. It is schematically shown and comprises a valve body 2, a drive unit 4, a controller 6, and an electro-pneumatic valve positioner 18. The valve body 2 has an inlet 8 and an outlet 10, and the two are communicated through a valve port 12. The inlet 8 is connected to the primary pipe 14 and the outlet
10 is connected to the secondary pipe 16 respectively.

The driving unit 4 applies an operating air pressure for driving to the upper surface of the diaphragm 20, and a spring 22 acting in the valve opening direction is provided on the lower surface. The stem 24 moves up and down by balancing both of them, and is provided at the lower end thereof. The opened valve 34 opens and closes the valve port 12. Reference number 28 is the stem 24, the valve 34
Is a lever that detects the displacement of the valve position and transmits it to the valve positioner 18.

The controller 6 compares the set pressure with the actually measured pressure from the secondary pressure detector 32, and outputs an operation output signal of the valve for converging the deviation based on the PID control through an electric line 38 to an electropneumatic valve positioner. In general, the percentage opening is converted into a current signal of 4 to 20 mA and sent to 18. The electropneumatic valve positioner 18 converts the driving air pressure (supply pipe 36) into an operating air pressure proportional to the operating output signal sent from the controller 6, and supplies the operating air pressure to the upper surface of the diaphragm 20 via the conduit 26. . Further, a correction operation is performed by the action of the valve positioner so that the opening degree of the valve accurately becomes the output pressure value from the controller 6. Therefore, the operation output signal (% valve opening) transmitted from the controller 6 and the actual valve opening almost coincide.

Next, the flow meter function will be described. Generally, the flow rate of the fluid passing through a valve can be determined by knowing the Cv value of the valve and the pressures before and after the valve. Here, in the case of the control valve, there is a problem that the Cv value changes according to the change in the opening degree of the valve, but this is solved by previously obtaining the change in the valve opening degree and the Cv value at that time. . FIG. 2 shows the relationship in a graph, and there are various relationships depending on the shape of the valve (40, 42, 44). Therefore, the relationship between the valve opening and the Cv value obtained as described above is stored in a computer in the controller 6.

On the other hand, although the pressure on the secondary side is detected by the pressure detector 32, the pressure on the primary side is further detected by the detector 30 and the signal value is sent to the controller 6 respectively. As described above, the opening degree of the valve is determined by the operation output signal sent from the controller 6 (% opening degree of the valve).
Therefore, the actual Cv value can be obtained from the relationship between the valve opening degree and the Cv value using the operation output signal. Therefore, the flow rate at that time can be calculated by the computer in the controller based on the Cv value and the detected primary and secondary pressures based on the following formula.

Q: Flow rate ΔP: Differential pressure P1: Primary pressure P2: Secondary pressure However, when P2 is smaller than (P1) / 2, to reach the critical flow velocity And

<Effect of the Invention> The flow rate can be obtained only by the control valve without separately providing a flow meter. In addition, since it is not necessary to separately provide a device or a member for the control valve, the control valve is very small and takes up a small space as a whole.

Further, since the valve opening instruction value from the controller is used as the actual valve opening, it is not necessary to newly provide a member for detecting the valve opening.

The conventional differential pressure type flow meter has a fixed orifice type, so the measurement range is limited. However, in the present invention, the variable orifice type allows measurement with a single unit over a wide range.

Since the valve port of the control valve and the orifice of the flow meter are used together, the pressure loss of the conventional flow meter is eliminated, and the fluid flows smoothly.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a control valve according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the% opening of the valve and the Cv value. 2: Valve body, 4: Drive unit 6: Controller, 8: Inlet 10: Outlet, 18: Electro-pneumatic valve positioner 30, 32: Pressure detector, 34: Valve

Claims (1)

(57) [Claims] 1. A control valve for controlling a flow rate of a fluid to be passed by operating a drive unit based on an operation output signal from a controller to open a valve to a desired position, comprising a primary side and a secondary side of the valve. A means for detecting the pressure on the side is provided, and the controller has a storage unit in which the relationship between the valve opening change and the Cv value at that time is stored in advance, and the controller corresponds to the operation output signal output by the controller. From the stored relationship based on the valve opening
A control unit for calculating a flow rate of a fluid passing through the valve from the obtained Cv value and the pressure value from the pressure detection means, and a control unit having a flow meter function.