JPS6022729B2 - Liquid level detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level detection method for detecting that the liquid level of liquid sodium has reached a predetermined position.

The conventional liquid sodium level detection method is performed by providing a guide 2 within a liquid sodium container 1 and setting a liquid level detector 3 at a predetermined position within the guide 2, as shown in FIG. The liquid level detector 3 has a primary coil 4 as shown in Fig. 2a.
Two secondary coils 5 and 6 wound in opposite directions are provided adjacently on the top, and the secondary coils 5 and 6 are connected in series.
The liquid level detector 3 is installed in the guide 2 so that the position between the next coils 5 and 6 is the liquid level detection position.

In addition, in FIG. 2a, the black circle mark indicates the beginning of winding of the coil.

Now, when the primary coil 4 is excited with a power source having a frequency of 4 to arc HZ, the output voltage of the secondary coil changes as shown in FIG. 2b as the liquid level of the liquid sodium rises.

That is, the liquid level of the liquid sodium changes from the 0 point to the secondary coil 6.
The output of the secondary coil is zero until it reaches the lower end point A, and the output of the secondary coil is zero until the liquid sodium level exceeds the lower end point A of the secondary coil 6 and reaches the upper end point B of the secondary coil 6. The output increases monotonically until the liquid level of the liquid sodium exceeds the upper end point B of the secondary coil 6 and reaches the lower end C of the secondary coil 5. The output remains unchanged at point B and monotonically decreases until the liquid level of the liquid sodium exceeds point C at the lower end of the secondary coil 5 and reaches point D at the upper end of the secondary coil 5. When the liquid level rises beyond the end point D of the secondary coil 5, the output of the secondary coil becomes zero.

In addition, when the level of liquid sodium decreases, the opposite trend is observed.

Therefore, the liquid level of the liquid sodium IJ was detected when the output of the secondary coil reached the maximum, and the liquid level was located between points B and C in Figure 2b. Detected.

However, when the level of liquid sodium rises, A, B, B
', 〇, D route, ○, C', C, B, A when descending
There is a drawback that the distance between the secondary coils 5 and 6 becomes hysteresis.

In addition, in order to eliminate this hysteresis, it is necessary to make the interval between the two secondary coils as small as possible, and it has not been possible to completely reduce the hysteresis to zero due to engineering considerations.

The present invention has been made in view of the above, and aims to solve the above problems and provide a method for detecting the level of liquid sodium without hysteresis. Place two secondary coils rotated in the same direction next to each other, compare the output voltages of the two secondary coils,
This method is characterized in that the liquid level of liquid sodium is detected by detecting one of the points where the output voltages of the two secondary coils are equal.

The method of the present invention will be explained below using examples.

FIG. 3 is a sectional view of a liquid level detector to which the method of the present invention is applied. 7 is a liquid level detector, in which a primary coil 9 is wound on an iron core 8 made of bobbin-shaped electromagnetic steel with a partition in the center, straddling the partition in the center, and on the primary coil 9,
A secondary coil 10 is wound in the same direction as the primary coil in the section from one end of the iron core 8 to the central partition,
A secondary coil lj is wound on the primary coil 9 in a section from the other end of the iron D8 to the central partition in the opposite direction to the secondary coil 10, and is fixed in the outer cylinder 12.

This liquid level detector 7 is installed at a predetermined position within a guide 2 fixed within a liquid sodium container 1 as shown in FIG.

Therefore, each primary coil 9 and secondary coil 10 and 1
1 may be an insulated conductor, but for example, as shown in FIG. 4, a cable is used in which the conductor is constantan 13 and the conductor 13 is covered with a sheath 15 made of Inconel through magnesium oxide 14.

By using such a cable, an extremely long service life can be ensured when the cable is used, for example, for detecting the liquid level of liquid sodium as a refrigerant in a nuclear reactor or the like.

Therefore, if the coil of the liquid level detector 7 is shown as shown in FIG. The relationship with the liquid level position of liquid sodium is as shown in FIG. 5b. That is, until the liquid level of the liquid IJ volume reaches the lower end point A of the secondary coil from point 0, the output voltage of the secondary coil 11 and the output voltage of the secondary coil 10 are the solid line and the - point, respectively. An output of V2 is generated as shown by the chain line.

In this state, only the output of the secondary coil 11 is taken out.

Next, until the liquid level of the liquid sodium exceeds the lower end point A of the secondary coil 11 and reaches the upper end point B, the secondary coil 11
The output voltage of the secondary coil IQ decreases, and the output voltage of the secondary coil IQ remains unchanged at V2, and when the liquid sodium level reaches the upper end point B of the secondary coil '1, the output of the secondary coil 11 The voltage is V.

Here, the output voltage of the secondary coil 11 decreases and the output voltage of the secondary coil 10 is taken out from when it reaches the confirmation level point E, and thereafter the output voltages of the secondary coil 10 and the secondary coil 11 are compared.

Next, the level of the liquid sodium rises, and the output voltage of the secondary coil 11 remains V until it exceeds the upper end point B of the secondary coil 11 and reaches the lower end point C of the secondary coil 10. The output voltage of the coil 10 remains at V2.

Next, the level of the liquid sodium rises, and the output voltage of the secondary coil 11 remains unchanged at V until it exceeds the lower end point C of the secondary coil 10 and reaches the upper end point D of the secondary coil 10. , the output voltage of the secondary coil IQ decreases from V2, and when the liquid level reaches the upper end point D of the secondary coil 10, the output voltage of the secondary coil 10 becomes V, and the output of the secondary coil 10 The voltage and the output voltage of the secondary coil 11 become equal. Then, the liquid level rises and the upper end D of the secondary coil 10
When the point position is exceeded, the output voltages of the secondary coils 10 and 11 do not change and remain at V.

In the present invention, the output voltage of the secondary coil 11 is multiplied by (10) suppression of (V3-V2).

Therefore, the output voltage of the secondary coil 11 explained above changes from the solid line position in FIG. 5b to the right side (V3-V
Translate by 2). Therefore, the output voltages of the secondary coils 10 and 11 will match at the G point and the F point. However, as mentioned above, if the voltage is set below the confirmation level E, the output voltage of the secondary coil 10 is not taken out.
Since the output voltages of the secondary coils 10 and 11 are not substantially compared, they are not detected, and it is detected that the output voltages of the secondary coils 10 and 11 match only at point F.

Here, the liquid level detector 7 is fixed within the guide 2 so that the position of the point F coincides with the liquid level position of the liquid sodium to be detected. Therefore, when the liquid level of the liquid sodium reaches the position of point F due to a change in the level of the liquid sodium, this can be detected.

Next, in the above embodiment, the number of windings and coil lengths of the secondary coils 10 and 11 are the same, but if it is not possible to match them completely due to manufacturing reasons, etc., the secondary coils 10 and 11 The output voltage with respect to the liquid sodium level position is as shown in FIG. 6a, and there may be cases where the output voltages do not match each other.

However, as described above, since the output voltage of the secondary coil 11 is suppressed by a constant voltage, there always occurs a point where the output voltages of the secondary coils 10 and 11 match. Therefore, even if there is an imbalance between the secondary coils 10 and 11, the liquid level can be detected. That is, unlike the conventional method, the fifth
Unlike detecting the liquid level between points B and C of the secondary coils 10 and 11 in Figure A, the present invention applies a bias voltage to one of the secondary coils to detect hysteresis from the liquid level detection point. is resolved.

Further, as shown in FIG. 5b, the secondary coils 10 and 11
Even if the output voltage of the secondary coil 1 does not bend discontinuously at an acute angle with respect to the voltage axis and changes as shown in FIG.
Point F, where the output voltages of 0 and 11 become equal, does not move and does not affect the accuracy of liquid level detection. Further, as mentioned above, since the wavefront detection point is only point F, hysteresis does not occur.

Further, as shown in FIG. 7, when the liquid sodium level rises, the secondary coil 10, which becomes below the liquid sodium level after the secondary coil 11, has the same number of turns as the secondary coil 11, and has a coil length. If the length is made shorter than that of the secondary coil 11, the rate of change in the output voltage of the secondary coil 10 with respect to a change in the liquid level position of the liquid sodium increases, and the accuracy of detecting the liquid sodium level position can be improved. .

Next, although the above description is based on the case where point F is detected among the points F and G where the output voltages of the secondary coils 10 and 11 match, the output of the secondary coil 18 near point F is not extracted.
Of course, there is no problem even if the G point is detected.

Also, due to the rise or fall of the liquid sodium level, there is a temperature difference between the coil part that is below the liquid sodium level and the coil part that is above the liquid sodium liquid level due to the temperature of the liquid sodium.
The output voltage of the secondary coil increases, but as the liquid level rises to point F, the position of point F, where the output voltages of the secondary coils 10 and 11 match, only shifts to the right in FIG. 5b.
Even if the absolute value of the output voltage changes, the correlation with the liquid level position hardly deviates.

As explained above, according to the method of the present invention, hysteresis can be completely eliminated in liquid level detection of liquid sodium, and the liquid level position can be detected accurately.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the installation of a liquid level detector. FIGS. 2a, b, and c are diagrams for explaining a conventional liquid level detection method. 3 and 7 are cross-sectional views of a liquid level detector to which the method of the present invention is applied. FIG. 4 is a sectional view of an example of a conductor of a liquid level detector. FIGS. 5a and 5b and 6a and 6b are diagrams for explaining the method of the present invention. 7: liquid level detector, 8: iron core, 9: primary coil, 10 and 11: secondary coil. Masukani Shio 2 Sardine Puchite Diagram Gum Koji Gag Koji Puteku Crab Puta Diagram

Claims (1)

[Claims] 1 In a liquid level detection method in which the liquid sodium is mounted at a predetermined position in a liquid sodium container and detects when the liquid sodium level has reached a predetermined position, the first coil is wound in opposite directions on the primary coil. and a second secondary coil adjacent to each other;
A constant bias voltage is added to the output voltage of one of the first or second secondary coils to obtain an output voltage, and the first and second
Comparing the output voltages of the secondary coils, detecting one position where the output voltages of the first and second secondary coils are equal, and detecting that the liquid level of the liquid sodium has reached the position. A liquid level detection method characterized by: