JPS5983017A - Liquid level detecting device - Google Patents

Abstract

PURPOSE:To prevent the discharge of a purging gas to the outside and to obtain a liquid level device having no detecting error, by sucking the purging gas in a tank with a hermetically sealed structure by a pump, controlling the gas so that a constant flow rate is obtained, and returning the gas into the tank. CONSTITUTION:A liquid level detector has a tank 9 with a hermetically sealed structure and a pipe 10, whose one end is connected to the upper end of the tank 9. The purging air in the tank 9 is taken out by the pipe 10. A pump 11 is connected to the other end of the pipe 10. A flow rate regulator 6 is connected to the down stream side of the pump 11. In this constitution, the liquid level of a radioactive waste liquid tank in an atomic power plant, a solution tank wherein a gas including poisonous components is accumulated, and the like can be detected without error and without discharging the purging gas into the ambient air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid level detection device for a liquid storage tank such as radioactive waste liquid.

[Technical background of the invention]

For example, in a liquid level detection device for a radioactive waste liquid storage tank in a nuclear power plant, since the stored liquid is a radioactive fluid, it is required to be able to measure the level remotely without directly coming into contact with the stored liquid to prevent personnel from being exposed to radiation.

FIG. 1 is a schematic diagram of a liquid level detection device of type 177-2 used for such purpose. As illustrated,
A purge pipe 3 is installed in a storage tank 2 with a closed structure in which the liquid 1 is stored, and purge air is supplied from an air supply means 5 through the pipe 4 to the base end of the purge pipe 30. ,
Purge air is discharged into the liquid 1 from the tip of the purge pipe 3.

A flow rate regulator 6 is provided in the middle of the tube 4, and the flow rate regulator 6 discharges air from the electric resistance stitch into the liquid 1. Numeral 7 is a vent pipe provided at the upper end of the storage tank 2, and the air inside the storage tank 2 is discharged to the outside through the vent pipe 7. The pens 1 to 7 are provided with filters (not shown) to prevent radioactive substances floating in the air in the storage tank 2 from being released into the outside air.・Ru.

Several pressure detectors 8 are installed in the tube 4 to detect the air pressure within the tube. The back pressure P in the tube 4 caused by discharging air from the purge tube 3 into the liquid 1 is expressed by equation (1).

P=f(+Pv・・・・・・・・・・・・・・・
......(1) [However, H: Static pressure of air corresponding to the level of liquid 1 in storage tank 2 Pv: Dynamic pressure of air at the tip of purge pipe 3] Here, dynamic pressure Pυ is air However, since the flow rate (flow rate) of the air at the tip of the purge pipe 3 is kept constant by the flow rate regulator 6, the back pressure P is proportional to the flow rate of the liquid 1 in the storage tank 2.
The liquid level (static pressure H) can be measured by the pressure detector 8.

[Problems with background technology]

I～However, in the liquid level detection device having such a configuration, if a problem occurs in the filling inside the vent pipe 7,
As shown in FIG. 2, the storage tank 2 becomes completely sealed. Therefore, the back pressure P becomes as shown in equation (2).

P = H+' Pv + P ・・・・・・・・・
(2) [However, P: Pressure of the air in the space within the storage tank 2] Therefore, due to such pressure Px, the measured value of the pressure detector 8 includes an error.

[Object of the Invention] The present invention was made based on the above-mentioned circumstances, and an object of the present invention is to provide a liquid level detection device that prevents the purge gas from being released to the outside in a storage tank and is free from detection errors.

[Summary of the invention]

In the present invention, the above-mentioned object is achieved by suctioning the purge gas in the sealed storage tank with a pump, controlling the flow rate to a constant level, and then returning it to the storage tank.

[Embodiments of the invention]

FIG. 3 is a schematic diagram of an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. In Figure 3, 9
A storage tank 10 (one end of which is connected to the upper end of the storage tank 9) has a closed structure, and the air inside the storage tank 9 is taken out to the outside through this pipe 10.The other end of the pipe 10 A bonder 11 is connected to the tank 9, and air in the storage tank 9 is sucked into a pump 11 through a pipe 10.

A flow rate regulator 6 is connected to the downstream side of the pump 11, and the downstream side of the flow rate regulator 6 is connected to the base end of a purge pipe 30 via a pipework 2. A pressure detector 8 is attached in the middle of the pipe 12.

A switching valve 13 is connected in the middle of the pipe 10.

The storage tank side of this switching valve 13 is normally open (during detection), but when the flow rate regulator 6, pressure detector 8, etc. are maintained or inspected, the storage tank side is closed and the air or clean gas is is sucked into the pump 11, and air containing radioactive particles remaining in the flow rate regulator 6 and the like is purged.

With the above configuration, when detecting the liquid level, air for purging the upper space in the storage tank 2 is supplied to the pump 11.
The liquid is sucked in, controlled to have a constant flow rate by the flow rate regulator 6, and discharged from the tip of the purge pipe 3 into the liquid 1 in the storage tank 2. Therefore, the purge air forms a closed loop, and radioactive particles in the air are never released outside this closed loop. In addition, the air pressure P in the upper space of the storage tank 2 is not only applied to the liquid level in the storage tank 2, but also applied to the pressure detector 8 via the pipe 10, pump 11, flow rate regulator 6, etc. , regarding the back pressure measurement by the pressure detector 8, the influence of the pressure py is canceled and the above equation (1) holds true.

〔Effect of the invention〕

According to the present invention, a purge gas is released into the outside air at a liquid level such as a radioactive waste liquid storage tank of a nuclear power plant or a solution storage tank where gas containing toxic components accumulates, where there is a risk of public exposure due to release into the atmosphere. It is possible to detect this without any error.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are schematic diagrams of a conventional liquid level detection device, and FIG. 3 is a schematic diagram of an embodiment of the present invention. 1...Liquid, 6...Flow rate regulator, 8...
...Pressure detector, 9° storage tank, 11...Pump application agent Patent attorney Kikuchi, Department 5, 3rd cause

Claims (1)

[Claims] A pump for suctioning purge gas in a storage tank having a sealed structure; a flow rate regulator provided downstream of the pump to control the flow rate of the purge gas to be constant; A purge pipe for discharging downstream purge gas into the liquid in the storage tank, and a pressure detector for detecting the pressure of the purge gas downstream of the flow rate regulator. Liquid level detection device.