Gas-liquid two-phase flow resistance-capacitance double-probe corrosion monitoring device

Abstract

A gas-liquid two-phase flow resistance-capacitance double-probe corrosion monitoring device mainly comprises a single-wire resistance probe measuring assembly and a single-wire capacitance probe measuring assembly. The monofilament resistance probes are arranged along the axial direction of the pipeline and cling to the inner wall, the monofilament capacitance probes are arranged along the radial direction of the pipeline and vertical to the inner wall, and the monofilament resistance probes and the monofilament capacitance probes are arranged along the pipeline in a staggered manner at intervals in the circumferential direction. Compared with the prior art, the single-wire resistance probe assembly and the single-wire capacitance probe assembly are combined, the corrosion condition and gas-liquid phase section distribution of the pipeline can be measured at the same time, the single-wire resistance probe assembly and the single-wire capacitance probe assembly are suitable for various flow patterns, the precision is high, the response speed is high, and a new technology and a new measurement means are provided for monitoring corrosion occurring parts and researching corrosion rules.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline corrosion monitoring, and particularly relates to a gas-liquid two-phase flow resistance-capacitance double-probe corrosion monitoring device for gas-liquid two-phase flow corrosion monitoring. Background Art

[0002] In the petroleum industry, gas-liquid two-phase flow is the most common fluid transportation state. Since there may be various corrosion media in gas-liquid two-phase flow, such as CO2, H2S, Cl - etc., the contact of these media with pipeline materials will accelerate electrochemical corrosion, resulting in a reduction in the pressure-bearing capacity of the pipeline, an increase in the risk of pipeline rupture. Severe corrosion will form perforations, trigger leakage accidents, and shorten the service life of the pipeline. In order to timely detect pipeline corrosion problems and avoid accidents, it is necessary to arrange corrosion monitoring devices on gas-liquid two-phase flow pipelines.

[0003] Currently, there are various pipeline corrosion monitoring methods, such as corrosion coupon monitoring method, corrosion probe monitoring method, field image FSM monitoring method, fixed-point thickness measurement monitoring method, etc. The principle of the corrosion coupon method is to calculate the corrosion rate of the pipeline through the ratio of the mass difference between the coupons installed in the pipeline at the front and back stages to the time interval. It is simple to operate but has a slow response speed and a long measurement period, and cannot monitor the corrosion situation of the pipeline in real time. The principle of the corrosion probe monitoring method is to reflect the corrosion condition of the pipeline through the probe. It is convenient to operate, has strong anti-interference ability, and is accurate in response. However, a single probe can only reflect the local corrosion condition of the pipeline, and the monitoring is not comprehensive. The principle of the field image FSM monitoring method is to capture and analyze the tiny electrical signal changes on the pipeline surface caused by corrosion to achieve real-time monitoring and evaluation of the corrosion process, and can perform full circumferential corrosion monitoring, but the implementation and maintenance costs are high and the technology is complex. The principle of the fixed-point thickness measurement monitoring method is to use the ultrasonic thickness measurement principle to determine the thinning of the pipeline wall thickness, so as to evaluate the pipeline corrosion rate and predict the remaining life. This method cannot accurately determine the most severely corroded part of the pipeline, resulting in ignoring some potential risk points.

[0004] Current research also shows that corrosion is closely related to the gas-liquid phase distribution, and traditional corrosion monitoring methods do not have the relationship between gas-liquid phase distribution and corrosion characteristics. To deeply explore the corrosion law, the present invention proposes a gas-liquid two-phase flow resistance-capacitance double-probe corrosion monitoring device, which realizes the simultaneous monitoring of the full circumferential corrosion condition of the gas-liquid two-phase flow pipeline and the gas-liquid phase distribution in the pipeline cross-section. Its advantages are high precision and fast response speed, providing a new technology and measurement means for monitoring the corrosion occurrence site and studying the corrosion occurrence law. Summary of the Invention

[0005] The present invention relates to a gas-liquid two-phase flow resistance-capacitance double-probe corrosion monitoring device, which is characterized in that: this system mainly includes a single-wire resistance probe measurement component and a single-wire capacitance probe measurement component.

[0006] The described single - wire resistance probe measurement assembly consists of a single - wire resistance probe, a resistance probe support, and a resistance measurement circuit. The single - wire resistance probe is made of a wavy - zigzag - shaped metal wire. The diameter of the single - wire resistance probe is less than 0.1 mm. Both ends of the single - wire resistance probe are respectively connected to measurement wires, and the measurement wires are led out from the top of the resistance probe support and connected to the resistance measurement circuit.

[0007] The described capacitance probe measurement assembly consists of a single - wire capacitance probe, a capacitance probe support, a capacitance measurement circuit, an inner metal electrode ring, and an outer metal electrode ring. The single - wire capacitance probe has a double - layer structure inside and outside. The center is a metal core, and the surface layer is an insulating layer. The thickness of the insulating layer is 1% - 5% of the diameter of the metal core. The inner metal electrode ring and the outer metal electrode ring are respectively in close contact with the inner wall and the outer wall of the monitored pipeline and are connected by an inner - outer ring short - wire to form an equipotential body. One end of the capacitance measurement circuit is connected to the metal core in the single - wire capacitance probe, and the other end is connected to the outer metal electrode ring.

[0008] The single - wire resistance probe is arranged along the axial direction of the pipeline and is closely attached to the inner wall. The single - wire capacitance probe is arranged along the radial direction of the pipeline and is perpendicular to the inner wall. In the circumferential direction, the single - wire resistance probe and the single - wire capacitance probe are arranged at intervals in an alternating manner. That is, in the circumferential direction, a single - wire capacitance probe is arranged between two single - wire resistance probes, and at the same time, a single - wire resistance probe is arranged between two single - wire capacitance probes.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] (1) By combining the single - wire resistance probe assembly and the single - wire capacitance probe assembly, the simultaneous measurement of the pipeline corrosion condition and the gas - liquid phase cross - section distribution is realized;

[0011] (2) By designing the wavy - zigzag - shaped single - wire resistance probe, the effective length of the resistance wire is increased, its resistance value is increased, and thus the resolution of corrosion and the sensitivity to corrosion are improved;

[0012] (3) By arranging the single - wire resistance probe assembly and the single - wire capacitance probe assembly at intervals in the circumferential direction of the pipeline, various states of the fluid and the wall surface inside the pipeline can be captured, realizing multi - parameter and multi - azimuth monitoring and improving the monitoring efficiency;

[0013] (4) The measurement result of the single - wire capacitance probe is not affected by parameters such as the salt content and temperature of the medium. The single - wire resistance probe has high sensitivity. The corrosion amount can be deduced by measuring the change of the fine resistance value, and then the corrosion rate can be obtained;

[0014] (5) Applicability to multiple flow patterns. This device can be used for measurement in various flow patterns such as annular flow, wavy flow, and stratified flow. Description of the Drawings

[0015] Figure 1 Schematic diagram of the composition of the present invention;

[0016] Figure 2 Schematic diagram of the distribution of the pipeline cross-section resistance probe assembly with double flanges of the present invention;

[0017] Figure 3 Schematic diagram of the structure of the single-filament resistance probe assembly of the present invention;

[0018] Figure 4 Schematic diagram of the structure of the single-filament resistance probe of the present invention;

[0019] Figure 5 Schematic diagram of the structure of the single-filament capacitance probe assembly of the present invention;

[0020] Figure 6 Schematic diagram of the measurement principle of the single-filament capacitance probe of the present invention;

[0021] Figure 7 Schematic diagram of the distribution of the probe assembly in the annular flow of the present invention;

[0022] Figure 8 Schematic diagram of the distribution of the probe assembly in the wavy flow of the present invention;

[0023] Figure 9 Schematic diagram of the distribution of the resistance-capacitance double probes in the pipeline of the present invention.

[0024] 1 - Single-filament resistance probe measurement assembly; 2 - Single-filament capacitance probe measurement assembly; 3 - Capacitance measurement circuit; 4 - Monitoring pipeline; 5 - Measurement wire; 6 - Resistance probe support; 7 - Single-filament resistance probe; 8 - Flange; 9 - Metal core; 10 - Insulating layer; 11 - Capacitance probe support; 12 - Single-filament capacitance probe; 13 - Outer ring of metal electrode; 14 - Inner ring of metal electrode; 15 - Resistance measurement circuit; 16 - Short wire between inner and outer rings; 17 - Metal wire. Detailed implementation manner

[0025] As Figure 1 shown, it mainly includes: a single-filament resistance probe measurement assembly 1 and a single-filament capacitance probe measurement assembly 2. The single-filament resistance probe measurement assembly 1 and the single-filament capacitance probe measurement assembly 2 are evenly spaced and staggered in the circumferential direction of the monitoring pipeline 4, that is, there is a single-filament capacitance probe measurement assembly 2 between two single-filament resistance probe measurement assemblies 1, and at the same time, there is a single-filament resistance probe measurement assembly 1 between two single-filament capacitance probe measurement assemblies 2. This layout can fully cover the pipeline cross-section and capture various states of the fluid and the wall surface in the pipeline, realizing multi-parameter and multi-directional monitoring.

[0026] As Figure 2As shown in the figure, the single-wire resistance probe measurement assembly 1 consists of a resistance probe bracket 6, a single-wire resistance probe 7, and a resistance measurement circuit 15. The single-wire resistance probe 7 is arranged along the axial direction of the pipeline and is closely attached to the inner wall of the pipeline. The single-wire resistance probe 7 is made of a wavy zigzag metal wire 17. The diameter of the single-wire resistance probe 7 is less than 0.1 mm. Both ends of the single-wire resistance probe 7 are respectively connected to the measurement wire 5. The measurement wire 5 is led out from the top of the resistance probe bracket 6 and is connected to the resistance measurement circuit 15. The resistance measurement circuit 15 is used to monitor the change of the resistance value of the single-wire resistance probe 7 in real time, and convert the resistance value into a voltage or current signal for transmission and processing; the resistance measurement circuit 15 uses the constant current and voltage measurement method for measurement. Flange 8 connectors are installed at both ends of the monitoring pipeline 4. Through the flange 8 connection, the rapid installation and non-destructive disassembly of the monitoring pipeline 4 can be realized, avoiding cutting or damaging the original pipeline when disassembling the monitoring pipeline 4, and ensuring the overall safety of the pipeline.

[0027] As Figure 3 and Figure 4 shown, the resistance probe bracket 6 is installed on the outer wall of the pipeline, providing stable support and fixation for the single-wire resistance probe 7. The single-wire resistance probe 7 is made of an ultra-fine metal wire 17. The metal wire 17 is designed in a wavy zigzag shape, aiming to increase the effective length of the resistance wire, improve the resistance value of the resistance wire, and further improve the resolution of corrosion, with a high sensitivity to the corrosion effect. When corrosion occurs on the inner wall of the pipeline, its resistance value will change, and then the corrosion rate can be obtained by measuring the resistance value; assuming the initial resistance value of the resistance wire is R0, after corrosion for a period of time, the resistance value of the resistance wire at time t becomes R t , then the corrosion rate within the two time instants t0 and t is:

[0028]

[0029] C R —Correction factor.

[0030] Therefore, by monitoring the resistance change of the resistance wire, the change of the corrosion environment during the test process can be indirectly reflected, and the higher the measurement frequency of the resistance value during the process, the finer the data obtained.

[0031] As Figure 5As shown, the monofilament capacitance probe assembly 2 is composed of a capacitance probe bracket 11, a monofilament capacitance probe 12, a capacitance measurement circuit 3, a metal electrode inner ring 14, and a metal electrode outer ring 13. The monofilament capacitance probe 12 has a double-layer structure inside and outside. The center is a metal core 9, and the surface layer is an insulating layer 10. The thickness of the insulating layer 10 is not less than 1% of the diameter of the metal core 9. The metal electrode inner ring 14 and the metal electrode outer ring 13 are respectively in close contact with the inner wall and the outer wall of the monitoring pipeline 4 and are connected by an inner and outer ring short wire 16 to form an equipotential body, which is used as an electrode of the capacitance measurement circuit 3. One end of the capacitance measurement circuit 3 is connected to the metal core 9 in the monofilament capacitance probe 12, and the other end is connected to the metal electrode outer ring 13.

[0032] As Figure 6 shown, when the monofilament capacitance probe 12 contacts a conductive liquid phase such as the water phase in the multiphase transportation pipeline, the conductive liquid phase and the metal core 9 form a cylindrical capacitor. The metal core 9 is one electrode of the capacitor, the conductive liquid phase is the other electrode of the capacitor, and the insulating layer 10 acts as the electrolyte of the capacitor. Its capacitance size is calculated by the following formula:

[0033]

[0034] L: The length of the liquid film in contact with the probe;

[0035] d1: The diameter of the metal core;

[0036] d2: The diameter of the insulating layer;

[0037] ε: The dielectric constant of the insulating layer material.

[0038] It can be seen from formula (2) that since d1, d2, and ε are all constants, the liquid film thickness and the probe capacitance value are linearly related and can be written as:

[0039] C = KL (3)

[0040] K is the linear coefficient of the monofilament capacitance probe, K = 2πε / ln(d1 / d2), and the value of K is only related to the probe material.

[0041] It can be seen from formula (2) that since the insulating layer 10 is very thin, d2≈d1, so the value of the denominator in formula (2) is very small, that is, the value of K in formula (3) is large, indicating that the measurement method of this monofilament capacitance probe has extremely high sensitivity.

[0042] As Figure 7 and Figure 8As shown, the single-wire capacitance probe measurement assembly 2 is arranged radially along the pipeline and perpendicular to the inner wall of the pipeline. The device designed in the present invention has 8 single-wire capacitance probes 12, so that the liquid film thickness at 8 characteristic points can be obtained, and then the gas-liquid phase cross-section distribution law can be obtained, which can provide gas-liquid phase cross-section distribution information for studying the corrosion law; the single-wire resistance probe measurement assembly 1 is arranged axially along the pipeline and closely attached to the inner wall of the pipeline. There are 8 single-wire resistance probes 7 in the example of the present invention, so that the resistance change at 8 characteristic points can be obtained, and then the corrosion depth in the diameter direction can be calculated, indirectly reflecting the change of the corrosion environment during the test process.

[0043] As Figure 9 shown, the metal electrode inner ring 14 is arranged on the inner wall of the pipeline, so as to ensure that there will be contact between the conductive liquid phase and the metal electrode inner ring 14 under any flow pattern. The metal electrode inner ring 14 and the metal electrode outer ring 13 are connected by the inner and outer ring short-circuit wire 16, and the two are equipotential bodies. One end of the capacitance measurement circuit 3 is connected to the metal core 9, and the other end is connected to the metal electrode outer ring 13, so that the liquid film height in the monitoring pipeline 4 can be measured.

[0044] The present invention realizes the simultaneous measurement of the circumferential corrosion condition of the pipeline and the gas-liquid phase cross-section distribution through the combination of the single-wire resistance probe measurement assembly and the single-wire capacitance probe measurement assembly. Moreover, the double-probe assemblies are distributed at intervals and staggered in the circumferential direction of the pipeline, and the gas-liquid distribution information at the corrosion probe can be obtained, so as to study the corrosion law, and further provide measurement tool support for corrosion research and control, and has a broad prospect of popularization and application.

Claims

1. A resistance-capacitance double-probe corrosion monitoring device for gas-liquid two-phase flow, characterized in that, Mainly including: A single - wire resistance probe measurement component (1) and a single - wire capacitance probe measurement component (2).

2. The corrosion monitoring device for gas-liquid two-phase flow with resistance-capacitance double probes according to claim 1, characterized in that: The single - wire resistance probe measurement component (1) is composed of a single - wire resistance probe (7), a resistance probe support (6), and a resistance measurement circuit (15). The single - wire resistance probe (7) is made of a wavy - broken - line - shaped metal wire (17). The diameter of the single - wire resistance probe (7) is less than 0.1 mm. Both ends of the single - wire resistance probe (7) are respectively connected to the measurement wire (5). The measurement wire (5) is led out from the top of the resistance probe support (6) and connected to the resistance measurement circuit (15).

3. The corrosion monitoring device for gas-liquid two-phase flow with resistance-capacitance double probes according to claim 1, characterized in that: The capacitance probe measurement component (2) is composed of a single - wire capacitance probe (12), a capacitance probe support (11), a capacitance measurement circuit (3), a metal electrode inner ring (14), and a metal electrode outer ring (13). The single - wire capacitance probe (12) has a double - layer structure inside and outside. The center is a metal core (9), and the surface layer is an insulating layer (10). The thickness of the insulating layer (10) is 1% - 5% of the diameter of the metal core (9). The metal electrode inner ring (14) and the metal electrode outer ring (13) are respectively in close contact with the inner wall and the outer wall of the monitoring pipeline (4) and are connected by an inner - outer ring short - wire (16) to form an equipotential body. One end of the capacitance measurement circuit (3) is connected to the metal core (9) in the single - wire capacitance probe (12), and the other end is connected to the metal electrode outer ring (13).

4. The corrosion monitoring device for gas-liquid two-phase flow with resistance-capacitance double probes according to claim 1, characterized in that: The single - wire resistance probe (7) is arranged along the axial direction of the pipeline and is closely attached to the inner wall. The single - wire capacitance probe (12) is arranged along the radial direction of the pipeline and is perpendicular to the inner wall. In the circumferential direction, the single - wire resistance probe (7) and the single - wire capacitance probe (12) are arranged at intervals and staggered, that is, in the circumferential direction, a single - wire capacitance probe (12) is arranged between two single - wire resistance probes (7), and at the same time, a single - wire resistance probe (7) is arranged between two single - wire capacitance probes (12).

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