JPH04236331A - Liquid level meter - Google Patents

Abstract

PURPOSE:To provide a liquid level meter which directly measures the liquid level in severe circumstances of high-temperature and high-pressure water and steam while a plurality of electrode rods are inserted into a pressure container. CONSTITUTION:As an electrode a fine wire of zirconium alloy is used. The surface of a conductive part thereof is coated with an oxide film for electrically insulation. Platium, gold or silver which is non-oxidizing is pressure-welded to the surface of an end part of an electrode rod where the electricity concentrates. In the liquid level meter thus obtained, a measuring electrode, a reference electrode and a comparison electrode which are formed into one body serving both as an electric conductor and as an electric insulator are arranged in a pressure container. Sine waves of 1kHz or so are applied to the meter in a manner not to influence a product and a test body. The change of the electric resistance when the measuring electrode comes in touch with the liquid is detected as the change of the liquid level.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level gauge, and more particularly to a liquid level gauge that directly measures the liquid level in harsh environments where high-temperature, high-pressure water and steam coexist by extracting the liquid level using electrical signals.

0002

[Prior Art] Conventional liquid level gauges measure the temperature below the boiling point of the liquid.
There are two methods for optically identifying the liquid level: (1) a glass level gauge taken out of the container, and (2) a transparent plate made of glass or sapphire fitted into the container. At temperatures above the boiling point of the liquid, there are two methods: (3) direct measurement inside the extraction pipe outside the container, (3) a method of detecting and measuring electromagnetic changes, and (4) a liquid level gauge using an ultrasonic oscillator. The liquid level gauge (1) cannot be used in high-temperature, high-pressure water and steam environments because the glass deteriorates. The liquid level gauge in (2) cannot be used if it is made of glass because it deteriorates in a high-temperature, high-pressure water or steam environment. Additionally, sapphire material has the disadvantage that it is affected by water stains and becomes difficult to identify. Furthermore, in this method, the heating element becomes asymmetrical, resulting in extremely poor temperature distribution. In the liquid level gauges (3) and (4), since the pipe is drawn out from the container, there is a temperature difference and the water level differs from the water level inside the container, resulting in an apparent liquid level. In addition, these liquid level gauges are structurally
The disadvantage is that the liquid level detection accuracy is extremely low. In this manner, high-accuracy liquid level detection cannot be achieved using conventional techniques in high-temperature, high-pressure water and steam environments. Regarding liquid level detectors using electrode rods at room temperature, a liquid level detection method using an electrical short circuit between electrodes is disclosed in JP-A-55-94112 or JP-A-57-567.
It is used in flowmeters such as No. 11. However, these level gauges cannot be used in high-purity water or high-temperature, high-pressure water environments.

0003

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid level gauge that can withstand high temperature and high pressure water and steam and has high detection accuracy, and also to provide a liquid level detector with high accuracy and a gas/liquid introduction pump. ,
The object of the present invention is to provide a liquid level gauge that can control the liquid level by a combination of an inlet valve, a pressure holding pump, and a discharge valve.

0004

[Means for Solving the Problems] The principle of the liquid level gauge of the present invention is that it consists of an electric circuit including a reference electrode in the liquid, a reference electrode outside the liquid, and a plurality of measuring electrodes between them. This method detects the liquid level by extracting the electrical signal generated by energizing a measurement electrode immersed in the liquid. The most important technology of the present invention is the production of compact electrode rods that are electrically conductive and electrically insulating in harsh environments of high temperature and high pressure water and steam. FIG. 1 is a sectional view of a single electrode rod made of a zirconium alloy material, and FIG. 2 shows the manufacturing process of the electrode rod made of a zirconium alloy material. Since the container in which the measurement is performed has a structure that maintains a high-temperature, high-pressure water and steam environment, the electrode rod 1 to be inserted is required to have a pressure-resistant seal. The pressure is maintained by a Teflon seal 4. For the sealing part, it is more effective to cover the electrode rod with a soft Teflon tube 5 due to its structure. However, the Teflon tube is used as an auxiliary tube because it deforms or deteriorates when exposed to high-temperature, high-pressure water and steam environments of 250° C. or higher. The electrode rod inside the container is a conductive material with a minute current collecting surface at its tip, and the outer surface other than the current collecting surface must be sufficiently electrically insulated. This solution focuses on the insulating properties of zirconium alloy's oxide film, and uses zirconium alloy for the electrode rod body, and micro-bonds non-oxidizing metals such as platinum, gold, or silver to the current collector. It's a method. That is, a zirconium alloy (zirconium, zircaloy, zirconium diobium alloy) thin wire was used for the conductive part of the electrode rod, and an oxide film 8 was provided on the outer surface (FIG. 1(b)), and the thickness of the oxide film 8 was 1. Although it is effective even if it is less than 1 micron, it is necessary to have a thickness of 1 to 50 microns as a mechanical protective film. The material of the current collecting surface 2 may be one or both of platinum, gold, and silver, with platinum being particularly optimal in terms of corrosion resistance. The zirconium alloy conductive material and the current collecting surface material are preferably joined by electrical resistance pressure welding, but they can also be manufactured by plating, screw fitting, brazing, welding, etc. Since zirconium alloy is an active metal, welding with dissimilar metals is extremely difficult. In addition, it is necessary to form a minute current collecting surface at the end of the zirconium alloy thin wire. FIG. 2 shows a method for producing a current collecting surface by electrical resistance pressure welding for producing electrode rods. A part of the conductive zirconium alloy thin wire 1 with metallic luster before insulation treatment is exposed and fitted with a copper material support 9, while the platinum thin wire 2, which is the current collecting surface constituent material, is supported by the copper material in the same way as the zirconium thin wire. Fix with tool 9 (FIG. 2(a)). This support 9 is directly connected to the welding machine electrode holder and serves to prevent overheating and bending of the current collecting surface material. FIG. 2-b shows a joined state immediately after welding, in which the fused portion 10 of the zirconium alloy and platinum material is extruded outward. FIG. 3 shows a photograph of the structure of the extruded part of the melted part. The extrusion of the melt part is
This is a suitable method for joining the new surfaces of two metals to each other. The outer periphery of the electrode rod after pressure welding is machined as shown in FIG. 2C at the portion discharged outward during welding, and the length of the current collecting surface in the longitudinal direction is arbitrarily machined according to detection accuracy. The length of the current collecting surface is preferably at least 0.2 mm to prevent mechanical damage and chipping due to corrosion. In the final process, the electrode rods are electrically insulated. In the electrical insulation treatment, the surface of the zirconium alloy conductor is oxidized by heating from 300° C. to 700° C. in the air or in high-temperature, high-pressure water and steam. The reason for determining the insulation treatment temperature is to form a structurally stable and dense oxide film; at temperatures below 300° C., the oxide film forms slowly and is thin, making it susceptible to mechanical damage. On the other hand, 70
This is because the oxide film formed becomes porous when treated at a high temperature exceeding 0° C., and there is a risk of it falling off and causing poor electrical insulation.

[0005]

[Operation] FIG. 4 shows the principle of the liquid level gauge of the present invention, and FIG. 5 shows a power supply circuit diagram of the present invention. The principle of the liquid level gauge is that when liquid comes into contact with the measuring electrode 14, the gap between the reference electrode 12 and the measuring electrode 14
This is detected as a potential difference between the electrodes by utilizing the change (in this case, decrease) in the electrical resistance value of the electrode. The power source is a sine wave oscillation circuit that applies a high frequency of about 1 kHz to the reference electrode, comparison electrode, and measurement electrode, respectively, and it is convenient to provide an amplitude variable device 22 to this circuit. The reason for using a sine wave oscillation circuit of approximately 1 kHz is to ensure that it does not adversely affect the untreated materials (products or test specimens) inside the container; applying DC power may change the corrosion potential and cause incorrect corrosion evaluation. This is not desirable, and the purpose is to eliminate this. In addition, the amplitude variable device 22 is provided because when the electrical conductivity of the liquid is very low, the liquid resistance is high even when the electrode contacts the liquid surface, and a sufficient potential for detection cannot be obtained. This is to increase the voltage amplitude so that the current can flow.

[0006]

Embodiment FIG. 6 shows an embodiment of the liquid level gauge of the present invention. This is a schematic example of detecting the liquid level in a pressure vessel in which high-temperature, high-pressure water and high-temperature, high-pressure steam coexist. The environment inside the pressure vessel is high-temperature, high-pressure water at 288° C. and 65 kg/cm 2 . Nine measuring electrodes 14 were set, and the positions of their current collecting surfaces were measured in advance and fixed via fixing plates. When the gas-liquid introduction valve 27 is opened, high-temperature, high-pressure water is introduced through the introduction pipe 29, causing the liquid level to rise and the measurement electrodes to be immersed one after another. To determine whether each measuring electrode 14 is immersed in the liquid, the pilot lamp 25, which is an indicator of the principle circuit shown in FIG. 4, is turned on to detect the liquid level. Further, in the circuit, the signal was converted into an analog signal and swept to a normal recorder 19. FIG. 7 shows an example of recording the liquid level over time. FIG. 8 shows a circuit diagram combining the liquid level gauge 24 and the liquid level controller 41. By programming the liquid level in the pressure vessel 32 of the corrosion tank in advance and connecting it to the introduction pipe 29, booster pump 42, and pressure holding valve 43 of the corrosion tank using the input and output of the liquid level gauge, it was possible to maintain an arbitrary gas-liquid interface. . In other words, due to the liquid level shortage signal from the liquid level gauge 24 and the controller 41, (1) the liquid level rises by driving the boost pump 42; (2)
In response to the over-level signal, the pressure-holding valve was driven to lower the level of the liquid and maintain a constant level. When circulating the liquid in the corrosion tank, it is always introduced at a constant rate using the boost pump 42, and the excess liquid is discharged by interlocking the liquid level gauge and the pressure holding valve 43 and returned to the water quality adjustment tank 45 through the return water introduction pipe 44. It was carried out in

[0007]

According to the present invention, a liquid level gauge that can withstand high temperature and high pressure water and steam and has high detection accuracy can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a single zirconium alloy electrode rod of the present invention.

FIG. 2 is an explanatory diagram of the manufacturing process of the zirconium alloy electrode rod of the present invention.

FIG. 3 is an explanatory diagram of the cross-sectional structure of the electrode rod after electric resistance pressure welding.

FIG. 4 is a diagram showing the principle of the liquid level gauge of the present invention.

FIG. 5 is a power supply circuit diagram of the present invention.

FIG. 6 is an explanatory diagram of an example of liquid level measurement in a high-temperature, high-pressure water autoclave.

FIG. 7 is an explanatory diagram of an example of liquid level measurement in a high-temperature, high-pressure water autoclave.

FIG. 8 is a block diagram of an embodiment of liquid level control measurement of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Zirconium alloy electrode rod, 2... Current collection surface material, 3... Electrode holder, 4... Seal part, 5... Teflon tube, 6... Push metal fitting, 7... Autoclave flange, 8... Oxide film, 9
...Copper support, 10. Melt-extruded metal interface, 11. Melt interface.

Claims (6)

[Claims] Claim 1: Using a zirconium alloy as an electrical conductor,
The outer peripheral surface is electrically insulated by applying an oxide film, and one end of the electrode rod is provided with a current collecting surface made of one or more of platinum, gold, or silver by electrical resistance pressure welding. liquid level gauge. 2. According to claim 1, a measurement electrode having an integrated structure, a reference electrode, and a reference electrode serving as the electrode rod, which serves as an electric conductor and an electric insulator, are disposed in a pressure vessel, and a liquid of the measurement electrode is disposed. A liquid level gauge that detects changes in electrical resistance due to contact as liquid level fluctuations. 3. According to claim 2, the electric signal generated by the liquid level gauge equipped with a measuring electrode, a reference electrode, and a comparison electrode for detecting fluctuations in the liquid level of high-temperature, high-pressure water is transmitted to a gas-liquid inlet valve and a gas-liquid discharge valve. A liquid level gauge equipped with a mechanism that controls the liquid level arbitrarily. 4. According to claim 2 or 3, the liquid level in the container is automatically controlled by linking the electric signal generated by the liquid level gauge to the gas-liquid introduction valve, the pressure boost pump, the gas-liquid discharge valve, and the pressure holding pump. Liquid level indicator. 5. A liquid level gauge according to claim 2, 3 or 4, wherein the measuring electrode, the reference electrode and the reference electrode are provided with a zirconium alloy support plate coated with an oxide film so that the position and material of the measuring electrode, the reference electrode and the reference electrode do not change due to high temperature and high pressure. . 6. The liquid level gauge according to claim 2, 3, 4 or 5, wherein a sine wave is used as the voltage applied to the liquid level detection electric circuit, and the amplitude can be varied.