JPS63225128A - Electrostatic capacity type level gage - Google Patents

Abstract

PURPOSE:To obtain a level gage being free from an error in measurement, excellent in the speed of transmission, capable of giving an adequate instruction or alarm and highly reliable, by providing slits in a ground tube in the axial direction thereof. CONSTITUTION:A slit 14 is provided in a length of about 1/3 of the full length of a ground tube 13 from the bottom thereof in view of the function of the tube, the maintenance of a capacity between the tube and a probe rod 12 and the protection thereof, and further several round holes 14A being larger than the width of the slit are provided in the intermediate positions of the slit 14 in consideration of the clogging due to solid constituents of a waste liquid. Although depending on the size of an apparatus, the width of the slit is preferably two to several millimeters, and the diameter of the hole is properly about double the width of the slit. Besides, the holes 14A are spaced properly at an interval of 40-60cm in the upper part and at an interval of 10-30cm in the fore end part. This constitution makes it possible to facilitate the circulation of the waste liquid between the inside of ground tube 13 and a vessel and to make a liquid level in the ground tube 13 follow a changing liquid level in the vessel in an instantaneous linkage thereto. In addition, the information of an adequate instruction or alarm is enabled by a connection of an appropriate alarming unit.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a capacitive liquid level needle.

(Prior Art) FIG. 3 is a sectional view showing a waste liquid transfer container 1 for storing and transporting radioactive waste liquid, and showing a state in which the container is filled with radioactive waste liquid 3 to a fixed amount. The entire waste liquid transfer container 1 is a pressure vessel, and this container is mounted on a transport vehicle, and an external pipe 5 is connected to a receiving port 4 at a predetermined location to receive the waste liquid. The waste liquid transfer container 1 that receives this radioactive waste liquid is covered with a thick jacket (not shown) on the outside because the radiation dose is high.

The liquid level in the waste liquid transfer container is detected by the liquid level needle 2.

Changes in liquid level, instructions, and alarms are reported via electrical signals to designated locations outside.

When the liquid level is accepted, a notification from the liquid level needle 2 is used to stop the operation of pumps and the like for the waste liquid transfer work being carried out at another location outside.

After receiving the waste liquid, the waste liquid transfer container 1 is transported by a transport vehicle to another location for waste liquid treatment, and work is performed to discharge the waste liquid out of the container. After connecting the external pipe 7 to the discharge port 6, compressed air is injected into the waste liquid transfer container 1 from the external pipe 9 through the air port 8, pressure is applied to the entire container, and this pressure forces the waste liquid into the pipe. 10 and discharge. During this discharge work, in order to forcibly remove the remaining waste liquid adhering to the inner wall surface of the container, pressurized water 18 is used from the cleaning water inlet 11.
Inject and clean the inner wall of the container with a spray.

The liquid level needle 2 that monitors the liquid level in the container during receiving and discharging operations uses a type called a capacitance type.
As shown in Fig. 4, this basic mechanism consists of a probe rod 12 and a gland pipe 13.
It consists of a double pipe. Although the detection unit itself is placed as close as possible to the bottom 16 of the waste liquid transfer container, a slight gap 17 is required in order to adjust the liquid level in the double pipe to the surroundings. Furthermore, a certain potential is applied to the probe rod 12 and the ground pipe 13 in advance, and a certain electric charge is always present through the waste liquid between the probe rod 12 and the ground pipe 13. Then, as the height of the waste liquid in the double pipe changes, the volume of the waste liquid between the probe rod 12 and the ground pipe 13 changes, and the value of the electric charge also changes. As a result, a change in liquid level results in a change in charge, which can be transmitted to the outside via a cable as an electrical signal.

When a pressure vessel such as this waste liquid transfer vessel is subjected to shocks such as cleaning, a capacitive liquid level needle is often used, with a gland pipe that serves as a protection. Because the liquid being handled is a highly radioactive substance, a device with a simple structure like this is used.

(Problems to be Solved by the Invention) However, the capacitance-type liquid level needle 2 having the above-described detection section structure has the following problems.

That is, since the radioactive waste liquid to be handled is not a simple liquid but contains a large amount of impurities such as various solid components such as used resin and waste sludge, the gap 17 between the tip of the detection unit and the bottom of the waste liquid transfer container is small. Therefore, impurities such as solid components get clogged here, and even though the liquid level 3 in the container changes, the liquid level 18 in the gland pipe does not follow suit, resulting in the phenomenon shown in Figure 5. occurs.

As a result, the measured liquid level is inaccurate and the external There is an error in the liquid level that is transmitted to the correct value.

In addition, due to the slow transmission speed of the liquid level, operations such as injecting and receiving waste liquid, pumping and discharging operations, etc. are delayed, and since the liquid to be handled is radioactive waste liquid, in the unlikely event of an accident, the work may become extremely dangerous. be.

The present invention has been made in consideration of the above-mentioned circumstances, and the liquid level in the gland pipe of the detection unit is linked to the changing liquid level in the container, eliminating measurement errors and achieving excellent transmission speed and appropriate control. The purpose is to obtain a highly reliable liquid level needle that reports instructions and alarms.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a ground pipe of a liquid level detection portion of a capacitive liquid level gauge.

A slit-shaped through hole is provided along the axial direction of the gland tube without sacrificing its function as a gland tube, that is, securing the volume between it and the internal probe rod, and the function of protecting the probe rod. be.

(Function) As a result, the waste liquid can flow between the inside of the gland pipe and the container, and the liquid level in the gland pipe can instantly follow the changing liquid level in the container.

(Embodiment) FIGS. 1 and 2 show a slit 14 according to an embodiment of the present invention.
Capacitance type liquid level gauge 2 to which a ground pipe 13 is applied
They are an overall view and a partial sectional view of A. As shown in this embodiment, the slit 14 is designed to serve as a gland pipe and to secure and protect the space between the probe rod 12 and the probe rod 12.
The slit 14 is provided with a length of about 3 mm, and in consideration of clogging by solid components of the waste liquid, a circular hole 14A larger than some slit widths is provided in the middle of the slit 14. Although the width of the slit depends on the size of the device, it is best to have a width of about 2 to several degrees, and the appropriate diameter of the hole is about twice the width of the slit. Hole spacing is 40~601 at the top and 10~30c at the tip.
m spacing is appropriate. Alternatively, the intervals between the holes may be gradually widened from the tip. However, since impurities such as solid components tend to stagnate downward, the circular hole 14A provided in a part of the slit is Further, the hole may not be circular but may be rectangular, and the slit 14 may be provided with a wide portion.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the gap at the tip of the detection part is smaller than the slit provided in the axial direction of the gland pipe, and even if a blockage such as solid matter occurs, the liquid level in the container will change. On the other hand, the liquid level inside the gland pipe changes accordingly.

As a result, the measured liquid level will be accurate, the liquid level transmitted to the outside will be the correct value, and errors will be eliminated.

In addition, the transmission speed of the liquid level is fast, and as a result, operations such as injection and reception of waste liquid, pressure-feeding and discharging operations, etc. can be carried out quickly, and safety can be sufficiently ensured.

[Brief explanation of drawings]

Fig. 1 is an overall view of a capacitive liquid level meter to which a ground pipe with a slit-like through hole is provided in the axial direction according to an embodiment of the present invention, and Fig. 2 is a cross section taken along line A-A in Fig. 1. Figure 3 is a sectional view of a conventional waste liquid transfer container, Figure 4 is an enlarged view of part B in Figure 3, and Figure 5 is an enlarged view of part B in Figure 3, where the liquid level does not follow. FIG. 2A...Capacitive liquid level gauge 12...Probe rod 13...Gland pipe 14...Slit 14A...Hole agent
Patent Attorney Nori Chika Yudo Hirofumi Mitsumata

Claims (2)

[Claims] (1) In a capacitive liquid level gauge that is equipped with a ground pipe with an open tip and a probe rod housed within the ground pipe, a slit is provided in the ground pipe along the axial direction. A capacitance type liquid level gauge characterized by: (2) The capacitive liquid level gauge according to claim 1, wherein the slit is provided with hole portions at intervals.