A steam compensation guided wave radar liquid level detector for nuclear power plants

Abstract

The present invention relates to the technical field of liquid level measurement in nuclear power plants, and specifically discloses a steam compensation guided wave radar liquid level detector for nuclear power plants, comprising a sealing leakage monitoring device, a measuring sleeve welded at the bottom end of the lower shell of the sealing leakage monitoring device, a flange welded on the outer wall of the lower shell, and a measuring guide rod arranged inside the measuring sleeve, and the two are coaxial. The liquid level detector of the present invention is suitable for liquid level measurement of a secondary circuit of a nuclear power plant, and can provide accurate liquid level measurement data for the unit under various circuit operating conditions and when the operating conditions change.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid level measurement in nuclear power plants, and in particular relates to a steam compensation type guided wave radar liquid level detector for nuclear power plants. Background Art

[0002] The liquid level measurement of the secondary circuit of a nuclear power plant needs to go through the following working conditions: negative pressure condition, high temperature, high pressure saturated steam rated power condition and power change condition. Conventional liquid level instruments, such as differential pressure level transmitters and float level gauges, cannot achieve automatic and accurate measurement under all working conditions due to the limitations of their own measurement principles.

[0003] Guided wave radar level meter is a new type of liquid level instrument. It adopts the principle of time domain reflection and is very mature in the working conditions of low temperature and pressure. However, in the measurement of the secondary circuit liquid level of nuclear power plants with high temperature, high pressure and variable working conditions, the existing steam compensation guided wave radar liquid level instrument has serious distortion in actual application. It has been verified that the main reason is that the instrument detector has insufficient anti-condensation and insufficient anti-interference functions, which leads to the failure of steam compensation and distortion of the instrument measurement value. Insufficient anti-condensation function means that the saturated steam in the high temperature and high pressure liquid level working environment is easy to condense into water when it is cold due to the unreasonable design of the internal structure of the detector. The periodic process of condensed water gathering and falling in the steam compensation section affects the periodic change of the dielectric constant in the high temperature and steam environment of the instrument, thereby directly affecting the periodic measurement drift of the instrument. The lack of anti-interference work is due to the fact that the steam compensation section of the existing instrument is too short and the steam compensation section is set near the liquid level connection port. This design means that it is easy to multiply the steam compensation deviation, causing serious distortion of the instrument measurement value.

[0004] In addition, existing high-temperature steam-type guided wave radar level gauges still have problems in actual applications, such as the lack of a leakage warning device in the detector and the inability to provide early warning of detector failure conditions. Some installation forms require the isolation of the nuclear power plant's secondary circuit heater for replacement, which affects the economy and safety of the nuclear power plant, and seriously hinders the promotion and application of high-temperature steam-type guided wave radar level gauges in the secondary circuits of nuclear power plants. Summary of the invention

[0005] The object of the present invention is to provide a steam compensation guided wave radar liquid level detector for a nuclear power plant, which has strong anti-condensation water and anti-interference capabilities.

[0006] The technical solution of the present invention is as follows:

[0007] A steam compensation guided wave radar liquid level detector for a nuclear power plant, comprising a sealing leakage monitoring device, a flange, a measuring sleeve, and a measuring guide rod;

[0008] The sealing leakage monitoring device comprises an upper metal material sealing ring, an upper high temperature resistant low dielectric material sealing ring, an upper shell, a lower shell, a high temperature resistant low dielectric material filling A, a high temperature resistant low dielectric material filling B, a lower metal material sealing ring, and a lower high temperature resistant low dielectric material sealing ring;

[0009] An upper high temperature resistant low dielectric material sealing ring is provided on the inner side of the upper metal material sealing ring;

[0010] The upper metal sealing ring is arranged above the upper shell, and the two are connected by threads;

[0011] A high temperature resistant low dielectric material filling A is provided on the upper inner side of the upper shell;

[0012] The lower shell is arranged below the upper shell;

[0013] A lower metal sealing ring is provided on the inner upper part of the lower shell, and the top end of the lower metal sealing ring contacts the bottom end of the upper shell;

[0014] A lower high temperature resistant low dielectric material sealing ring is provided on the inner side of the lower metal material sealing ring;

[0015] A high temperature resistant low dielectric material filling A is provided at the inner lower part of the lower shell;

[0016] A high temperature resistant low dielectric material filling B is laid on the side wall of the cavity surrounded by the inner lower part of the upper shell and the inner upper part of the lower metal material sealing ring, and the inner cavity of the high temperature resistant low dielectric material filling B serves as a leakage detection cavity;

[0017] Welding a measuring sleeve at the bottom end of the lower shell of the sealing leakage monitoring device, and welding a flange on the outer side wall of the lower shell;

[0018] The measuring guide rod is arranged inside the measuring sleeve, and the two are coaxial.

[0019] A steam compensation section is processed in the middle of the measuring sleeve. The outer diameter of the steam compensation section is the same as the outer diameter of the measuring sleeve, and the inner diameter of the steam compensation section is larger than the inner diameter of the measuring sleeve.

[0020] The length of the steam compensation section is 400-900 mm, which can reduce error amplification disturbance.

[0021] The position of the steam compensation section is 500-520 mm higher than the normal maximum liquid level.

[0022] The upper metal material sealing ring is seamlessly wrapped with the upper high temperature resistant low dielectric material sealing ring, and the lower shell, the lower metal material sealing ring and the lower high temperature resistant low dielectric material sealing ring are seamlessly wrapped to play a sealing and heat insulating role.

[0023] The measuring sleeve is provided with connecting holes arranged at equal intervals along the axial direction, which are used to balance the liquid levels inside and outside the measuring sleeve.

[0024] The lower shell and the upper shell are connected via threads.

[0025] The lower shell and the outer part of the upper shell are fixed by annular spot welding.

[0026] When performing liquid level detection, high-frequency electromagnetic wave signals propagate from the instrument processor along the measuring guide rod.

[0027] At the upper metal material sealing ring and the upper high temperature resistant low dielectric material sealing ring, due to the increase in impedance, a positive reference waveform is fed back;

[0028] When there is no leakage, the upper and lower end surfaces of the leak detection cavity will form negative and positive standard feedback waveform signals in turn due to the change of impedance; when the leaked liquid in the leak detection cavity reaches a certain amount, the impedance continues to decrease, the negative feedback waveform exceeds the leakage alarm threshold, and the instrument will automatically trigger the leakage alarm;

[0029] Due to the change of impedance at the upper and lower end surfaces of the steam compensation section, two standard feedback waveform signals, positive and negative, are formed in turn. By calculating the time difference between the two signals and combining the fixed length of the steam compensation section, the dielectric constant of the measurement environment is calculated, and the liquid level measurement value in the high-temperature steam environment is automatically compensated.

[0030] When measuring the liquid level, a large negative feedback liquid level waveform signal will be formed at the measuring liquid level surface due to the large reduction in impedance.

[0031] The remarkable effects of the present invention are:

[0032] (1) The liquid level detector of the present invention has the function of preventing steam condensation, thereby improving the accuracy of high-temperature steam environment instrument measurement and being able to automatically and accurately compensate for the measurement error caused by the change in the dielectric constant of the measurement environment.

[0033] (2) The liquid level detector of the present invention sets the steam compensation section in a stable steam flow field and extends the steam compensation section, thereby improving anti-interference performance. At the same time, a leakage monitoring device is added, and the detector has a leakage alarm function.

[0034] (3) The liquid level detector of the present invention is suitable for measuring the liquid level of the high-pressure heater, low-pressure heater, condenser, and steam-water separation reheater drain of the secondary circuit of a nuclear power plant, and can provide accurate liquid level measurement data for the unit under various operating conditions of the circuit, such as high and low temperature environments under negative pressure, normal pressure, and high pressure, as well as when the operating conditions change. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the liquid level detector of the present invention;

[0036] Figure 2 This is a schematic diagram of a seal leakage monitoring device;

[0037] Figure 3 This is a typical waveform diagram of liquid level detection.

[0038] In the figure: 1. Sealing leakage monitoring sealing device; 2. Sealing flange; 3. Steam compensation section; 4. Measuring sleeve; 5. Measuring guide rod; 1-1. Upper metal sealing ring; 1-2. Upper high temperature resistant low dielectric material sealing ring; 1-3. Upper outer shell; 1-4. Lower outer shell; 1-5. High temperature resistant low dielectric material filling A; 1-6. High temperature resistant low dielectric material filling B; 1-7. Lower metal sealing ring; 1-8. Lower high temperature resistant low dielectric material sealing ring; 1-9. Leakage detection cavity. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1 A steam compensation guided wave radar liquid level detector for a nuclear power plant shown in the figure comprises a sealing leakage monitoring device 1, a flange 2, a steam compensation section 3, a measuring sleeve 4, and a measuring guide rod 5.

[0041] like Figure 2 As shown, the sealing leakage monitoring device 1 includes an upper metal material sealing ring 1-1, an upper high temperature resistant low dielectric material sealing ring 1-2, an upper outer shell 1-3, a lower outer shell 1-4, a high temperature resistant low dielectric material filling A1-5, a high temperature resistant low dielectric material filling B1-6, a lower metal material sealing ring 1-7, and a lower high temperature resistant low dielectric material sealing ring 1-8.

[0042] The high temperature resistant low dielectric material has the characteristics of high temperature resistance, poor thermal conductivity and low dielectric constant, such as PEEK material.

[0043] The metal material has the characteristics of high temperature resistance and corrosion resistance, such as 316L stainless steel material.

[0044] An upper high-temperature resistant low-dielectric material sealing ring 1-2 is seamlessly wrapped on the inner side of the upper metal material sealing ring 1-1, and both of them play a role of sealing and heat insulation.

[0045] The upper metal material sealing ring 1-1 is arranged above the upper shell 1-3, and the two are connected by threads.

[0046] A high temperature resistant low dielectric material filling A1-5 is provided on the inner upper part of the upper shell 1-3, which has heat insulation and sealing effects.

[0047] The lower shell 1-4 is arranged below the upper shell 1-3, the two are connected by threads, and fixed by annular spot welding on the outside. The upper shell 1-3 and the lower shell 1-4 are made of stainless steel.

[0048] A lower metal sealing ring 1-7 is provided on the inner upper part of the lower housing 1-4, and the top of the lower metal sealing ring 1-7 contacts the bottom of the upper housing 1-3. A lower high temperature resistant low dielectric material sealing ring 1-8 is provided on the inner side of the lower metal sealing ring 1-7.

[0049] The lower shell 1-4, the lower metal material sealing ring 1-7 and the lower high temperature resistant low dielectric material sealing ring 1-8 are seamlessly wrapped to play a sealing and heat insulating role.

[0050] A high temperature resistant low dielectric material filling A1-5 is provided at the inner lower part of the lower shell 1-4, which has heat insulation and sealing effects.

[0051] On the side wall of the cavity surrounded by the inner lower part of the upper outer shell 1-3 and the inner upper part of the lower metal material sealing ring 1-7, a high temperature resistant low dielectric material filling B1-6 is laid, and the internal cavity of the high temperature resistant low dielectric material filling B1-6 serves as a leakage detection cavity 1-9.

[0052] The sealing leakage monitoring device 1 can work for a long time in the environment of 280-300° C. and 7 MPa in the secondary circuit of a nuclear power plant, and has functions such as high-temperature insulation, high-pressure sealing, and steam leakage monitoring.

[0053] A measuring sleeve 4 is welded to the bottom end of the lower shell 1 - 4 of the sealing leakage monitoring device 1 , and a flange 2 is welded to the outer side wall of the lower shell 1 - 4 .

[0054] The measuring guide rod 5 is arranged inside the measuring sleeve 4, and the two are coaxial.

[0055] The measuring sleeve 4 is provided with connecting holes arranged at equal intervals along the axial direction, which are used to balance the liquid levels inside and outside the measuring sleeve 4 so as to quickly make the liquid levels inside and outside the measuring sleeve 4 consistent when the working conditions change.

[0056] The outer diameter of the measuring sleeve 4 is 40 mm, the inner diameter is 35 mm, and the wall thickness is 2.5 mm. A steam compensation section 3 is processed in the middle of the measuring sleeve 4. The outer diameter of the steam compensation section 3 is 40 mm, the inner diameter is 38 mm, the wall thickness is reduced to 1 mm, and the inner diameter is enlarged. This design can avoid the interference of steam condensation water on the measurement.

[0057] The length of the steam compensation section 3 is 400-900 mm, which can reduce the error amplification disturbance. The steam compensation section 3 is located in a relatively stable area, 500-520 mm higher than the normal maximum liquid level.

[0058] When performing liquid level detection, a high-frequency electromagnetic wave signal propagates from the instrument processor along the measuring guide rod 5 .

[0059] like Figure 3 As shown, at the upper metal material sealing ring 1-1 and the upper high temperature resistant low dielectric material sealing ring 1-2, due to the increase in impedance, a positive reference waveform is fed back.

[0060] When there is no leakage, two standard feedback waveform signals, negative and positive, will be formed in turn on the upper and lower end surfaces of the leakage detection cavity 1-9 due to the change in impedance; when the leakage liquid in the leakage detection cavity 1-9 reaches a certain amount, the impedance continues to decrease, and the negative feedback waveform exceeds the leakage alarm threshold, the instrument will automatically trigger the leakage alarm.

[0061] Due to the change in impedance at the upper and lower end surfaces of the steam compensation section 3, two standard feedback waveform signals, positive and negative, are formed in turn; by calculating the time difference between the two signals and combining the fixed length of the steam compensation section 3, the dielectric constant of the measurement environment is calculated, thereby automatically compensating the liquid level measurement value in the high-temperature steam environment.

[0062] When measuring the liquid level, a large negative feedback liquid level waveform signal will be formed at the measuring liquid level surface due to the large reduction in impedance.

Claims

1. A steam compensation guided wave radar liquid level detector for a nuclear power plant, characterized in that: It comprises a sealing leakage monitoring device (1), a flange (2), a measuring sleeve (4), and a measuring guide rod (5); The sealing leakage monitoring device (1) comprises an upper metal material sealing ring (1-1), an upper high temperature resistant low dielectric material sealing ring (1-2), an upper shell (1-3), a lower shell (1-4), a high temperature resistant low dielectric material filling A (1-5), a high temperature resistant low dielectric material filling B (1-6), a lower metal material sealing ring (1-7), and a lower high temperature resistant low dielectric material sealing ring (1-8); An upper high-temperature resistant low-dielectric material sealing ring (1-2) is provided on the inner side of the upper metal material sealing ring (1-1); The upper metal material sealing ring (1-1) is arranged above the upper outer shell (1-3), and the two are connected via threads; A high temperature resistant low dielectric material filling A (1-5) is provided on the upper inner side of the upper shell (1-3); The lower shell (1-4) is arranged below the upper shell (1-3); A lower metal material sealing ring (1-7) is provided on the inner upper part of the lower outer shell (1-4), and the top end of the lower metal material sealing ring (1-7) is in contact with the bottom end of the upper outer shell (1-3); A lower high temperature resistant low dielectric material sealing ring (1-8) is provided on the inner side of the lower metal material sealing ring (1-7); A high temperature resistant low dielectric material filling A (1-5) is provided at the lower inner portion of the lower outer shell (1-4); A high temperature resistant low dielectric material filling B (1-6) is applied on the side wall of the cavity surrounded by the inner lower part of the upper shell (1-3) and the inner upper part of the lower metal material sealing ring (1-7), and the inner cavity of the high temperature resistant low dielectric material filling B (1-6) serves as a leakage detection cavity (1-9); A measuring sleeve (4) is welded to the bottom end of the lower shell (1-4) of the sealing leakage monitoring device (1), and a flange (2) is welded to the outer wall of the lower shell (1-4); The measuring guide rod (5) is arranged inside the measuring sleeve (4), and the two are coaxial; A steam compensation section (3) is machined in the middle of the measuring sleeve (4); the outer diameter of the steam compensation section (3) is the same as the outer diameter of the measuring sleeve (4), and the inner diameter is larger than the inner diameter of the measuring sleeve (4); The length of the steam compensation section (3) is 400-900 mm, which can reduce the error amplification disturbance; The position of the steam compensation section (3) is 500-520 mm higher than the normal maximum liquid level.

2. A steam compensation guided wave radar liquid level detector for a nuclear power plant as claimed in claim 1, characterized in that: The upper metal material sealing ring (1-1) and the upper high temperature resistant low dielectric material sealing ring (1-2) are seamlessly wrapped, and the lower shell (1-4), the lower metal material sealing ring (1-7) and the lower high temperature resistant low dielectric material sealing ring (1-8) are seamlessly wrapped, thereby achieving sealing and heat insulation effects.

3. A steam compensation guided wave radar liquid level detector for a nuclear power plant as claimed in claim 2, characterized in that: The measuring sleeve (4) is provided with connecting holes arranged at equal intervals along the axial direction, for balancing the liquid levels inside and outside the measuring sleeve (4).

4. A steam compensation guided wave radar liquid level detector for a nuclear power plant as claimed in claim 3, characterized in that: The lower shell (1-4) and the upper shell (1-3) are connected via threads.

5. A steam compensation guided wave radar liquid level detector for a nuclear power plant as claimed in claim 4, characterized in that: The lower shell (1-4) and the upper shell (1-3) are fixed externally by annular spot welding.

6. A steam compensation guided wave radar liquid level detector for a nuclear power plant as claimed in any one of claims 1 to 5, characterized in that: When liquid level detection is performed, a high-frequency electromagnetic wave signal is transmitted from the instrument processor along the measuring guide rod (5).

7. A steam compensation guided wave radar liquid level detector for a nuclear power plant as claimed in claim 6, characterized in that: At the upper metal material sealing ring (1-1) and the upper high temperature resistant low dielectric material sealing ring (1-2), due to the increase in impedance, a positive reference waveform is fed back; When there is no leakage, two standard feedback waveform signals, negative and positive, are formed in sequence on the upper and lower end surfaces of the leakage detection cavity (1-9) due to the change in impedance; when the amount of leaked liquid in the leakage detection cavity (1-9) reaches a certain amount, the impedance continues to decrease, the negative feedback waveform exceeds the leakage alarm threshold, and the instrument automatically triggers a leakage alarm; Due to the change in impedance, two standard feedback waveform signals, positive and negative, are formed in sequence at the upper and lower end surfaces of the steam compensation section (3). By calculating the time difference between the two signals and combining the fixed length of the steam compensation section (3), the dielectric constant of the measurement environment is calculated, thereby automatically compensating the liquid level measurement value in the high-temperature steam environment. When measuring the liquid level, a large negative feedback liquid level waveform signal will be formed at the measuring liquid level surface due to the large reduction in impedance.

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