JPS6034056B2 - liquid level indicator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level gauge, and more particularly to a liquid level indicating device that automatically controls valve operation to eliminate errors in liquid level display due to temperature differences with the inside of a container.

A liquid level gauge is installed outside the container to detect the height of the liquid level in a container such as a boiler drum, but if the temperature inside the container differs from the temperature around the liquid level meter, an error will occur in the liquid level display.

FIG. 1 shows the installed state of the liquid level gauge, in which a liquid level gauge 1 is connected to a container 5 via a steam pipe 3 and a canned water pipe 4.
Thereby, the liquid 10 in the container 5 is introduced into the liquid level gauge 1, and the liquid level is confirmed through the glass 6. Since this liquid level gauge is placed in the atmosphere, there is likely to be a temperature difference between it and the inside of the container 5, which causes an error in the liquid level display. Especially when the container is at high temperature and high pressure, when the temperature of the liquid in the level gauge drops, the specific gravity of the liquid in the level gauge will be greater than that of the liquid in the container, and the liquid level will fall in response to the difference. Therefore, an error Δh occurs with respect to the true liquid level. In order to eliminate such display errors of the liquid level gauge, it is necessary to create a passage around the liquid level gauge to keep the liquid level gauge warm by creating a passage through which the steam extracted from the container passes, or to install a special electric heater. Although this method has been implemented, it is uneconomical and has various inconveniences, such as complicating the equipment and requiring a special heat source for heating the level gauge. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a device that can accurately display the liquid level without making major modifications to the liquid level gauge.

In short, this invention provides a temperature sensor for each of the liquid level gauge and the container, and a drain pipe for the liquid level gauge.If the temperature difference between the liquid in the liquid level gauge and the liquid in the container exceeds a certain value, By automatically controlling the valves installed in the piping and drain pipe connecting the surface gauge and the container, the temperature of the liquid level gauge is made equal to the temperature inside the container, and the liquid level is accurately displayed. Prior to inventing this device, the inventors conducted the following experiments.

In this experiment, when saturated steam and saturated water were contained in a container, the temperature drop of saturated water in a liquid level gauge and the accompanying specific volume were compared. The container used in this experiment is a can with a water level of 241 cm, and the liquid level gauge is on the diameter 11 side and the length is 2.
This is the one on the 41st side. Figure 2 shows the above experimental results in a graph, where graph a shows a steam pressure of 200k9.
/lump g, graph b shows 150k9'g, and graph shows 100kg/c flow g. As is clear from this graph, the liquid level display error Δh increases as the temperature inside the liquid level gauge decreases. Note that the line 10a (Δh=0) in the figure indicates the water level inside the can. It was also confirmed that the higher the steam pressure, the greater the error caused by a small temperature drop. FIG. 3 shows a water level gauge showing an embodiment of the present invention.
A drain pipe 12 with 1 is connected. A steam valve 13 and a can water valve 14 are provided in the steam pipe 3 and the can water pipe 4, which connect the container 5 and the water level gauge 1, respectively.
And the can water valve 14 is connected to the control box 15 along with the drain valve 11.
are connected to each other by control circuits 18a, 18b, and 18c. Reference numeral 16 is a temperature sensor placed on the thermometer side of the canned water 10 in the container 5, and reference numeral 17 is a temperature sensor placed on the liquid level gauge 1, and these temperature sensors 16 and 17 are also connected to the control box 15. It is connected to input each measured temperature. In the above device, canned water 10 in container 5
The water level is constantly monitored via the glass 6 of the liquid level gauge 1 (in the case of high pressure, use a multi-boat type).

On the other hand, temperature sensors 16 and 17 constantly transmit and input the can water temperature in the container and the can water temperature in the liquid level gauge to the control box 15 as temperature signals. As time passes, the temperature of the canned water in the liquid level gauge decreases, creating a temperature difference between it and the canned water in the container. When this temperature difference reaches a preset value, the control box 15 opens a valve. Perform operations to restore the water level gauge's readings to normal. FIG. 4 shows an example of this operation for returning the water level indicator to normality. In addition, in order to keep the display error △h of the liquid level gauge 1 within the allowable value, the pressure inside the can must be 200k.
In the case of 9/enemy, the temperature difference between the can water in the container 5 and the liquid level gauge 1 is about 300, and in the case of the 150k9/c fin, it is about 7℃, 100.
In the case of k9/en, it is desirable to start the operation to return the liquid level gauge to normal when the level reaches approximately 1000 (see Figure 2). Next, an example of the operating procedure of the above-mentioned liquid level gauge will be explained with reference to FIG.

In addition, No. in the figure. 13V, No. 14V and M. 11
V indicates the steam valve 13, can water valve 14, and drain valve 11 shown in Fig. 3, and the diagonal lines in the figure indicate that the valves are closed, and the non-shaded areas indicate that they are closed. Indicates the state in which Further, arrow T indicates the passage of time. First, the control box 15 opens the steam valve 13 and can water valve 14 when the difference in temperature detected by the temperature detectors 16 and 17 reaches a certain value as described above, and temporarily stops the function of the liquid level gauge 1. do. (
Symbol A indicates the range in which the water level gauge is functioning. ) After a certain short time t has passed and the two valves 13 and 14 are reliably closed, the drain valve 11 is opened and the liquid level gauge indication normal return operation B is performed. First, operate the drain valve 11 as described above to drain the canned water remaining in the level gauge 1 into the drain pipe 1.
2, it is discharged to the outside. Once the canned water has been drained,
By opening the steam valve 13, the operation port is operated, the liquid level gauge 1 is warmed, and the remaining canned water is almost completely discharged to the outside by steam. The steam valve 13 is closed again for a certain period of time t.
2 (same as above, this is a short period of time to confirm that the valve operation has been completed, and the same applies hereafter), and then the canned water valve 14 is opened. This warms the can water pipe 4, and when it reaches a predetermined temperature, the can water valve 14 is closed. After the time has elapsed, open the steam valve 13 again to warm up the inside of the level gauge 1 and perform step 2, and when the temperature reaches the predetermined temperature, close the drain valve 11 to stop releasing steam to the outside. do. When the closed state of the drain valve 11 is confirmed after a period of time has elapsed, the canned water valve 14 is also opened in addition to the steam valve 13 to complete the liquid level gauge indication normal return operation B, and the liquid level gauge 1 is functional. Return to range A. When the temperature difference between the can water in the container 5 and the liquid level gauge 1 reaches a predetermined value, the control box 15 performs the above-mentioned valve operations to keep the error in the indication of the liquid level gauge 1 within the permissible value. . By carrying out this invention, it is possible to always keep the error in the indication of the liquid level gauge within the permissible value, and furthermore, it is possible to achieve the effect that the valve operation can be automatically performed by the control box, thereby saving labor.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional liquid level gauge, Fig. 2 is a line diagram showing the relationship between canned water temperature drop and liquid level display error, and Fig. 3 is a system diagram of the liquid level indicating device according to the present invention. FIG. 4 is a block diagram showing an example of valve operation. 1...Liquid level gauge, 3...Steam pipe, 4...
...Canned water pipe, 5... Container, 10... Canned water, 11... Drain valve, 12... Drain pipe, 13...・Steam valve, 14... Can water valve, 16, 17... Temperature detector, 18a, 18
b, 18c...circuit. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 In a pressure vessel with a liquid level gauge connected to a pressure vessel via a steam pipe with a steam valve and a can water pipe with a can water valve, and a drain pipe with a drain valve connected to the liquid level gauge, the inside of the vessel and the liquid level Temperature detectors were placed inside the meter, and a circuit was installed to connect these steam valves, canned water valves, drain valves, and each temperature detector to a control box and control these valves according to commands from the control box. A liquid level indicating device characterized by: