Orifice plate flowmeter intelligent anti-blocking system and method based on multivariate diagnosis

Abstract

The application provides a hole plate flowmeter intelligent anti-blocking system and method based on multivariate diagnosis, and belongs to the technical field of natural gas metering. The system comprises a filtering assembly arranged on the upstream side of a hole plate throttling device, a cleaning and blowdown system, a logic diagnosis control unit, a blowdown assembly arranged on the downstream side, and a liquid accumulation monitoring unit. The filtering assembly comprises a filtering plate with a built-in zigzag flow channel. By arranging multiple pressure taking points on the downstream side of the hole plate throttling device and comparing the pressure values of the pressure taking points in real time, it can be determined whether there is liquid accumulation at the bottom of the pipeline. When the liquid accumulation reaches a preset threshold, the system opens a liquid accumulation blowdown valve to blow down. The method performs the whole-process closed-loop automatic control of "monitoring-diagnosis-cleaning-verification" by the diagnosis control unit. The application can prevent the contamination and liquid accumulation from blocking the hole plate and the pressure taking port without interrupting the metering, improves the metering accuracy, has the functions of pipeline liquid accumulation fault diagnosis and blowdown, and prolongs the equipment maintenance period.

Description

Technical Field

[0001] This invention relates to the field of natural gas metering technology, and in particular to an intelligent anti-clogging system and method for orifice plate flowmeters based on multivariate diagnostics. Background Technology

[0002] Orifice plate flow meters are widely used in industrial process control due to their simple structure, robustness, durability, and cost-effectiveness. However, their measurement accuracy is highly dependent on the cleanliness of the fluid medium. Impurities such as solid particles, sludge, and hydrates carried in the fluid easily accumulate near the throttling element of the orifice plate; this phenomenon is called "fogging." Fogging alters the effective flow cross-sectional area of ​​the orifice plate, disrupting the pressure distribution before and after it, thus leading to significant and unpredictable measurement errors. Specifically: (1) Metering accuracy is easily affected by contamination: Solid and liquid impurities carried in natural gas can easily contaminate the orifice plate edge or block the pressure tap, resulting in inaccurate differential pressure measurement, which in turn affects the accuracy of flow calculation; the existing filter components have ambiguous flow channel parameters, low interception efficiency for impurities in natural gas and poor adaptability.

[0003] (2) Difficulty in detecting and handling liquid accumulation in pipelines: Liquid easily accumulates at the bottom of pipelines, especially near throttling devices, altering the flow field and causing metering errors. Filtration, liquid accumulation monitoring, and drainage components operate independently and cannot be dynamically adjusted according to operating conditions, resulting in low pollution prevention and drainage efficiency and large metering deviations. The lack of an automatic feedback mechanism after filter blockage easily leads to flow field turbulence, exacerbating the liquid accumulation problem. Existing technologies lack effective online monitoring and drainage methods, typically requiring gas outages for maintenance, affecting the continuity of gas supply.

[0004] (3) High maintenance cost and low efficiency: Due to pollution and liquid accumulation, the orifice plate flow meter needs to be shut down, disassembled, cleaned and repaired regularly. The operation is cumbersome, the maintenance cost is high, and the work efficiency is reduced.

[0005] Currently, the main solutions to the fouling problem of orifice plate flow meters and their limitations are as follows: (1) Periodic manual drainage: Operators manually open the drain valve to drain the sewage according to the preset maintenance plan or after observing obvious abnormal instrument readings. This method relies entirely on manual labor, and the response is not timely. It is a passive and reactive maintenance method, which not only increases labor costs, but may also lead to long-term inaccurate measurement data due to failure to handle the situation in a timely manner.

[0006] (2) Passive prevention through structural optimization: For example, the "valve-type orifice plate throttling metering device" disclosed in Chinese utility model patent CN222460754U aims to prevent liquid accumulation in the pipeline from entering the pressure-conducting pipe by horizontally installing the orifice plate, placing the pressure tapping hole on the top of the valve body, and adopting a vertical pressure-conducting pipe design, thereby ensuring the accuracy of the signal during gas metering. The core of this solution is to protect the measurement signal and passively prevent liquid accumulation through structural design, but it does not provide an active detection and removal mechanism for solid particle blockage.

[0007] (3) Complex measurement methods for specific fluids: For example, the "Integrated Dual Differential Pressure Tapping Circular Orifice Plate Gas-Liquid Two-Phase Flow Measurement Device" disclosed in Chinese Utility Model Patent CN209764327U uses a circular orifice plate and a three-point pressure tapping structure (forming two differential pressure values), combined with a specific algorithm to calculate the flow rates of the gas and liquid two-phase flows. Although this patent sets a drain port and drain valve below the pressure tapping ring chamber, its draining operation still requires manual triggering and does not achieve automation and intelligent diagnosis. Its innovation lies in the measurement method itself, rather than maintenance automation.

[0008] In summary, existing technologies either rely on passive prevention and manual intervention, or employ simple single-variable control logic, lacking a closed-loop automated solution capable of intelligent diagnosis, proactive cleaning, and effectiveness verification to fundamentally solve the clogging problem of orifice plate flowmeters. Therefore, there is an urgent need for a simple device capable of online anti-fouling and drainage functions to ensure the long-term accurate and stable operation of natural gas orifice plate flowmeters. Summary of the Invention

[0009] In view of this, the present invention aims to propose an intelligent anti-clogging system and method for orifice plate flow meters based on multivariate diagnosis, which can intelligently distinguish between real fouling and process fluctuations, automatically execute the complete process of "filtration-monitoring-discharge-verification", and significantly improve the long-term operational reliability and measurement accuracy of orifice plate flow meters.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows: an intelligent anti-clogging system for orifice plate flowmeters based on multivariable diagnostics, comprising: An orifice plate throttling device is installed on the main metering pipe section; The filter assembly is installed on the main metering pipe section and is located upstream of the orifice plate throttling device. Pressure taps are provided on the inlet and outlet sides of the filter assembly, and differential pressure sensors are connected to the pressure taps. The high-pressure end of the differential pressure sensor is connected to the pressure tap on the inlet side, and the low-pressure end of the differential pressure sensor is connected to the pressure tap on the outlet side. The cleaning and sewage discharge system is located upstream of the orifice plate throttling device and includes a pre-purge and backwash valve, a cleaning and sewage discharge valve, and a high-pressure pulse backwash pump. The pre-purge and backwash valve and the cleaning and sewage discharge valve are respectively connected to the inlet side and the internal flow channel of the filter plate through the high-pressure pulse backwash pump. The drain assembly, located downstream of the orifice plate throttling device, includes a collection tank connected to the bottom of the main metering pipe section, and a drain valve installed at the bottom of the collection tank, which is used to collect liquid accumulated at the bottom of the main metering pipe section. The liquid accumulation monitoring unit includes a main differential pressure transmitter, a flow computer control unit, and a first downstream pressure tap and a second downstream pressure tap installed on the main metering pipe section. The first downstream pressure tap is located at the upper part of the downstream pipe of the orifice plate throttling device, and the second downstream pressure tap is located at the lower part of the downstream pipe of the orifice plate throttling device. Pressure sensors are installed on the first and second downstream pressure taps respectively. The first and second downstream pressure taps are electrically connected to the flow computer control unit through the pressure sensors. The high-pressure end of the main differential pressure transmitter is connected to the upstream pressure tap of the orifice plate, and the low-pressure end of the main differential pressure transmitter is connected to the downstream pressure tap of the orifice plate. At the same time, the main differential pressure transmitter and the flow computer control unit are electrically connected. The logic diagnostic control unit contains a comparison circuit, a state machine logic, and a drive circuit. The comparison circuit compares the voltage signal of the differential pressure sensor with a preset threshold. The state machine logic outputs drive signals to the pre-purge and backwash valves and the cleaning drain valve in sequence according to the comparison result. The drive circuit converts the drive signals into opening and closing commands for the corresponding valves. The cleaning drain valve opens under the command of the state machine logic to realize the draining step. After completing the above steps, the comparison circuit reads the voltage signal of the differential pressure sensor of the filter component again and compares it with the preset warning threshold to confirm the cleaning effect.

[0011] Furthermore, the filter assembly includes a multi-layer labyrinthine microporous filter plate formed by sintering 3 to 5 layers of SS316L stainless steel wire mesh. The edge of the filter plate is sealed to the inner wall of the main metering pipe section via a flange. The filter plate has a labyrinthine flow channel with at least 5 turning angles of 120° to 150° and a total length of 30mm to 45mm, forming a flow path for inertial impact to capture solid particles. An inlet for connecting a high-pressure pulse backwash pump is reserved on the upstream side of the filter plate, and a drain port for connecting a cleaning drain valve is reserved on the downstream side of the filter plate. The surface of the filter plate is covered with an anti-corrosion coating.

[0012] Furthermore, the thickness of each layer of stainless steel wire mesh in the filter plate is 0.15 mm, and the sintering temperature is 1150℃. The labyrinthine flow channel has a width of 150µm and a depth of 100µm; The anti-corrosion coating is polytetrafluoroethylene with a thickness of 0.3 mm.

[0013] Furthermore, in the sewage discharge component, the volume of the liquid collection tank is 0.5 m³ to 1.0 m³, and its material is carbon steel lined with epoxy resin, with a lining thickness of 2 mm. A capacitive liquid level sensor is installed inside the liquid collection tank to detect the liquid height in the tank. The liquid level sensor is a capacitive sensor with a measurement range of 0 - 1 m and a resolution of 0.5 mm. The accumulated liquid sewage discharge valve is connected to the bottom of the liquid collection tank through a sewage discharge pipe.

[0014] Furthermore, in the accumulated liquid monitoring unit, the pressure sensor is a piezoelectric sensor with a measuring range of 0 - 0.2 MPa and a sensitivity of 5 mV / V. The flow computer control unit includes a comparison circuit. Its input terminals are connected to piezoelectric pressure sensors respectively installed at the first downstream pressure tapping point and the second downstream pressure tapping point, and a liquid level sensor installed inside the liquid accumulation tank. When the comparison circuit detects that the upper and lower pressure differences in the metering main pipe section exceed the cleaning trigger threshold T1 or the liquid level exceeds the threshold H, it outputs a driving signal to the accumulated liquid sewage discharge valve to achieve liquid discharge.

[0015] Furthermore, the differential pressure sensor is a piezoresistive sensor with a rated measurement range of 0 - 0.5 MPa. The high-pressure pulse backwashing pump is a two-stage centrifugal pump with a maximum output pressure of 1.5 MPa, and it自带 a proportional valve to achieve pressure regulation within the range of 0.5 MPa - 1.5 MPa.

[0016] Furthermore, the internal program of the programmable logic controller uses a ladder diagram to implement the state machine logic. Its internal comparison circuit includes an analog-to-digital converter, which converts the analog voltage output by the differential pressure sensor into a digital signal and compares it with the stored warning threshold T2.

[0017] Furthermore, the system includes an RS-485 communication interface, which outputs digital alarm codes according to the Modbus RTU protocol.

[0018] The present invention also provides an intelligent anti-blocking method for an orifice flowmeter based on multi-variable diagnosis, including the following steps: Normal operation state: Continuously monitor the main differential pressure ΔP1 of the orifice and the differential pressure ΔP2 of the filter component, calculate and output the flow rate according to the main differential pressure ΔP1, and at the same time, calculate the flow rate change rate dQ / dt according to the main differential pressure ΔP1. Blockage warning and diagnosis: When it is monitored that the differential pressure ΔP2 of the filter component exceeds the preset cleaning trigger threshold T1, the system enters the active monitoring state; in this state, the system will judge whether the flow rate change rate dQ / dt is less than the preset stability threshold T3; when |dQ / dt| < T3, the system confirms that blockage has occurred. Automatic cleaning and sewage circulation: After a blockage is confirmed, the system automatically enters the cleaning and sewage circulation state and performs a series of actions in sequence, including pre-purging, high-pressure pulse backwashing, final sewage discharge, and stabilization, or isolation, pre-purging, high-pressure pulse backwashing, final sewage discharge, and stabilization. Cleaning effect verification: After the cleaning and sewage discharge cycle is completed, the system enters the verification state; after the normal flow is restored and the fluid is stabilized, the new baseline value of the differential pressure ΔP2 of the filter component is reread. If the new baseline value is lower than the warning threshold T2, it proves that the cleaning is effective and the system returns to normal operation. If the new baseline value is still greater than or equal to the warning threshold T2, the system can repeat the automatic cleaning and sewage discharge cycle or issue a serious fault alarm after multiple failed attempts.

[0019] Compared with existing technologies, the intelligent anti-clogging system and method for orifice plate flowmeters based on multivariate diagnostics described in this invention has the following advantages: (1) Accurate diagnosis and avoidance of misjudgment: By introducing the differential pressure (ΔP2) of the filter component and the rate of change of flow (dQ / dt) as collaborative diagnostic variables, a multivariate diagnostic model was constructed. This enables the system to accurately distinguish between differential pressure rise caused by actual fouling and differential pressure rise caused by process fluctuations, fundamentally solving the defect of single-variable control logic being prone to false alarms; (2) Closed-loop fully automatic control, unattended operation: This invention realizes closed-loop automatic control of the entire process from "monitoring-diagnosis-cleaning-verification". Through multiple sets of pressure taps set up above and below the pipeline, online real-time monitoring of pipeline liquid accumulation is realized. Once blockage and liquid accumulation are detected, sewage discharge can be carried out without interrupting the supply and without affecting normal metering, which greatly reduces the gas outage time caused by maintenance and improves the pipeline's operating efficiency and gas supply guarantee capability; (3) High-efficiency filtration and cleaning structure: The innovative "multi-layer labyrinth microporous filter structure" not only provides extremely high particle capture efficiency and dirt holding capacity, but its structure is also very conducive to cleaning and regeneration through high-pressure backwashing, ensuring the long-term effectiveness of the system. (4) High system integration: It integrates filtration, sensing, control and actuator into one intelligent and self-maintaining flow measurement "subsystem", which can be easily integrated into existing or new orifice plate flow meter installations, and has strong practicality and promotion value. (5) Simple structure, easy to modify and promote: The components of this invention have simple structures and can be modularly installed on existing orifice plate flowmeter pipe sections. Modification is convenient, cost is controllable, and it has strong applicability and promotion value. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of an intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics. Figure 2 This is a schematic diagram of the flow channel cross-section of the filter plate in the filter assembly. Figure 3 This is a flowchart of the state machine for the linkage control logic.

[0021] Explanation of reference numerals in the attached figures: 1. Main metering pipe section; 2. Filter assembly; 3. Orifice plate throttling device; 4. Upstream pressure tap of orifice plate; 5. Downstream pressure tap of orifice plate; 6. Flow computer control unit; 7. First downstream pressure tap; 8. Second downstream pressure tap; 9. Main differential pressure transmitter; 10. Collection tank; 11. Liquid drain valve; 12. Differential pressure sensor for filter assembly; 13. Logic diagnostic control unit; 14. Cleaning and draining system; 15. Integrated filter and draining module; 16. Pre-purge and backwash valve; 17. Cleaning and draining valve; 21. Inlet; 22. Outlet; 23. SS316L stainless steel mesh; 24. Labyrinth flow channel; 25. Steering angle. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] This invention relates to an intelligent anti-clogging system (method) for orifice plate flowmeters, capable of automatically diagnosing, clearing, and verifying blockage status based on multivariate diagnostics. It is an intelligent anti-fouling and sewage discharge system and its control method, suitable for metering scenarios in long-distance natural gas pipelines containing impurities and prone to condensation. For example... Figure 1 As shown, this invention provides an intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics, comprising: 1. Filter Component 2: Located upstream of the orifice plate throttling device 3. The core of this component is a detachable, multi-layered labyrinthine microporous filter plate, used to effectively intercept and adsorb impurities and condensate in the gas before it enters the orifice plate. Its edges are sealed to the inner wall of the metering main pipe section 1. Multiple tortuous flow channels are evenly distributed on the filter plate, forming a labyrinthine flow channel 24. When natural gas flows through this filter plate, solid impurities and some droplets in the gas are adsorbed or intercepted by the filter material due to inertial collision. Simultaneously, the tortuous labyrinthine flow channel 24 design prolongs the contact time between the gas and the filter material, improving the filtration effect and providing a certain degree of flow stabilization.

[0025] 2. Drainage assembly: Located downstream of the orifice plate throttling device 3. This assembly includes a collection tank 10 communicating with the bottom of the pipe, and a drain valve 11 installed at the bottom of the collection tank 10. The collection tank 10 is used to collect liquid accumulated at the bottom of the pipe.

[0026] 3. Liquid Accumulation Monitoring Unit: At least two sets of pressure taps are installed at different locations above and below the orifice plate throttling device 3 downstream of the pipe. By comparing the pressure difference between the upper and lower pressure taps at the same cross-section in real time, it can be determined whether there is liquid accumulation at the bottom of the pipe. When the pressure at the bottom is significantly higher than the pressure at the top, it indicates that liquid has accumulated.

[0027] 4. Control and Execution Unit: The signal from the liquid accumulation monitoring unit is transmitted to the flow computer control unit 6. When the detected pressure difference exceeds a preset threshold, the controller issues a command to automatically open the liquid accumulation drain valve 11 for drainage, or to send an alarm signal to the operator for manual operation of the liquid accumulation drain valve 11. After drainage is completed, the valve closes.

[0028] The multi-layer labyrinthine microporous filter plate is made of multiple layers of micron-sized metal wire mesh sintered together, with a labyrinthine tortuous flow channel formed in the middle layer through an etching process. When fluid enters the filter plate vertically, it is forced to undergo multiple sharp turns through these channels, efficiently capturing solid particles using the principle of inertial impact.

[0029] Specifically, the system includes: Orifice plate throttling device 3 is installed on metering main pipe section 1; The filter assembly 2 is installed on the metering main pipe section 1 and is located upstream of the orifice plate throttling device 3. Pressure taps are provided on the inlet 21 side and the outlet 22 side of the filter assembly 2, and differential pressure sensors are connected to the pressure taps. The high-pressure end of the differential pressure sensor is connected to the pressure tap on the inlet 21 side, and the low-pressure end of the differential pressure sensor is connected to the pressure tap on the outlet 22 side. The cleaning and backwashing system 14 is located upstream of the orifice plate throttling device 3. It includes a pre-purge and backwash valve 16, a cleaning and backwashing valve 17, and a high-pressure pulse backwashing pump. The pre-purge and backwash valve 16 and the cleaning and backwashing valve 17 are respectively connected to the inlet 21 side of the filter plate and the internal flow channel through the high-pressure pulse backwashing pump (pressure range 0.5MPa to 1.5MPa) to realize the pre-purge and backwashing steps. The drain assembly, located downstream of the orifice plate throttling device 3, includes a collection tank 10 connected to the bottom of the main metering pipe section 1, and an electromagnetic liquid collection drain valve 11 installed at the bottom of the collection tank 10. The collection tank 10 is used to collect the liquid accumulated at the bottom of the main metering pipe section 1. The liquid accumulation monitoring unit includes a main differential pressure transmitter 9, a flow computer control unit 6, and a first downstream pressure tap 7 and a second downstream pressure tap 8 installed on the main metering pipe section 1. The first downstream pressure tap 7 is located at the upper part of the downstream pipe of the orifice plate throttling device 3, and the second downstream pressure tap 8 is located at the lower part of the downstream pipe of the orifice plate throttling device 3. Pressure sensors are installed on the first downstream pressure tap 7 and the second downstream pressure tap 8 respectively. The first downstream pressure tap 7 and the second downstream pressure tap 8 are electrically connected to the flow computer control unit 6 through the pressure sensors to obtain the upper and lower pressures in real time and form a voltage difference signal. The high-pressure end of the main differential pressure transmitter 9 is connected to the upstream pressure tap 4 of the orifice plate, and the low-pressure end of the main differential pressure transmitter 9 is connected to the downstream pressure tap 5 of the orifice plate. At the same time, the main differential pressure transmitter 9 and the flow computer control unit 6 are electrically connected. The logic diagnostic control unit 13 internally includes a comparison circuit, a state machine logic, and a drive circuit. The comparison circuit compares the voltage signal of the differential pressure sensor with a preset threshold. The state machine logic outputs drive signals sequentially to the pre-purge and backwash valve 16 and the cleaning drain valve 17 based on the comparison result. The drive circuit converts the drive signals into opening and closing commands for the corresponding valves. The cleaning drain valve 17 opens under the command of the state machine logic to perform the draining step. After completing the above steps, the comparison circuit reads the voltage signal of the differential pressure sensor 12 of the filter assembly again and compares it with the warning threshold to confirm the cleaning effect. In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Preferably, the filter assembly 2 includes a multi-layer labyrinthine microporous filter plate formed by sintering 3 to 5 layers of SS316L stainless steel wire mesh. The edge of the filter plate is sealed to the inner wall of the metering main pipe section 1 via a flange. The filter plate is provided with a labyrinthine flow channel 24, which has at least 5 turning angles 25 of 120° to 150° and a total length of 30mm to 45mm, forming a flow path for inertial impact to capture solid particles. An inlet 21 for connecting a high-pressure pulse backwash pump is reserved on the upstream side of the filter plate, and a drain port for connecting a liquid discharge valve 11 is reserved on the downstream side of the filter plate. The surface of the filter plate is covered with an anti-corrosion coating.

[0032] Preferably, the thickness of each layer of stainless steel wire mesh in the filter plate is 0.15 mm, and the sintering temperature is 1150℃. The labyrinthine flow channel 24 has a width of 150µm and a depth of 100µm; The anti-corrosion coating is made of polytetrafluoroethylene (PTFE) with a thickness of 0.3 mm.

[0033] Preferably, in the sewage discharge assembly, the volume of the liquid collection tank 10 is 0.5m³ to 1.0m³, and the material is carbon steel lined with epoxy resin with a lining thickness of 2mm; the liquid collection tank 10 is equipped with a capacitive liquid level sensor to detect the liquid level in the tank. The liquid level sensor is a capacitive sensor with a measurement range of 0-1m and a resolution of 0.5mm; the liquid discharge valve 11 is connected to the bottom of the liquid collection tank 10 through a sewage discharge pipe.

[0034] Preferably, in the liquid accumulation monitoring unit, the pressure sensor is a piezoelectric sensor with a range of 0-0.2 MPa and a sensitivity of 5 mV / V; The flow computer control unit 6 includes a comparison circuit, whose input terminal is connected to a piezoelectric pressure sensor installed on the first downstream pressure tap 7 and the second downstream pressure tap 8 respectively, and a liquid level sensor installed in the liquid collection tank. When the comparison circuit detects that the pressure difference between the upper and lower parts of the metering main pipe section 1 exceeds the cleaning trigger threshold T1 or the liquid level exceeds the threshold H, it outputs a drive signal to the liquid discharge valve 11 to realize liquid discharge.

[0035] Preferably, the differential pressure sensor is a piezoresistive sensor with a rated measurement range of 0-0.5 MPa; The high-pressure pulse backwash pump is a two-stage centrifugal pump with a maximum output pressure of 1.5MPa and a built-in proportional valve to achieve pressure regulation within the range of 0.5MPa-1.5MPa.

[0036] Preferably, the internal program of the programmable logic controller implements the state machine logic using a ladder diagram. The internal comparison circuit includes an analog-to-digital converter that converts the analog voltage output by the differential pressure sensor into a digital signal and compares it with the stored warning threshold T2.

[0037] Preferably, the system includes an RS-485 communication interface that outputs digital alarm codes according to the Modbus RTU protocol. The RS-485 communication interface is a serial communication standard widely used in industrial environments and is connected to the diagnostic control unit 13 (DCU), so it will not be elaborated here.

[0038] The present invention also provides an intelligent anti-blocking method for orifice flowmeters based on multivariate diagnosis. This method is executed by the logic diagnosis control unit 13 (DCU) and includes the following steps: Normal operation state: Continuously monitor the main differential pressure ΔP1 of the orifice and the differential pressure ΔP2 of the filter component, calculate and output the flow rate based on the main differential pressure ΔP1, and at the same time, calculate the flow rate change rate dQ / dt based on the main differential pressure ΔP1; Blockage warning and diagnosis: When it is monitored that the differential pressure ΔP2 of the filter component exceeds the preset cleaning trigger threshold T1, the system enters the active monitoring state; in this state, the system will judge whether the flow rate change rate dQ / dt is less than the preset stable threshold T3; when |dQ / dt| < T3, the system confirms that blockage has occurred; Automatic cleaning and sewage discharge cycle: After confirming the blockage, the system automatically enters the cleaning and sewage discharge state and sequentially executes a series of actions including pre-blowing, high-pressure pulsed backwashing, final sewage discharge, and stabilization, or sequentially executes a series of actions including isolation, pre-blowing, high-pressure pulsed backwashing, final sewage discharge, and stabilization; Verification of cleaning effect: After the cleaning and sewage discharge cycle ends, the system enters the verification state; after the normal flow is restored and the fluid is stabilized, the new baseline value of the differential pressure ΔP2 of the filter component is read again. If the new baseline value is lower than the warning threshold T2, it proves that the cleaning is effective and the system returns to the normal operation state; if the new baseline value is still greater than or equal to the warning threshold T2, the system can repeat the automatic cleaning and sewage discharge cycle or issue a serious fault alarm after multiple attempts fail.

[0039] In the actual application process, the system of the present invention is installed on the main natural gas measurement pipeline 1. Upstream of the orifice throttling device 3, a filter component 2 is installed. The inside of the filter component 2 is a filter plate with a zigzag flow channel. When natural gas flows in from the left and passes through the filter component 2, the solid impurities and droplets carried in it are effectively intercepted, and the cleaned gas continues to flow to the orifice throttling device 3. Orifice upstream pressure tapping points 4 and orifice downstream pressure tapping points 5 are respectively provided on both sides of the orifice throttling device 3, and the pressure signals of these two pressure tapping points are sent to the main differential pressure transmitter 9 for calculating the differential pressure of the main flow path.

[0040] Its core components include: a standard orifice plate throttling device 3, an integrated filter drain module 15, a main differential pressure sensor, a filter assembly differential pressure sensor 12, a logic diagnostic control unit 13 (DCU), a cleaning drain valve 17, a high-pressure backwash pump, and actuators such as an orifice plate liquid accumulation monitoring and drain module. The integrated filter drain module 15 is installed in the upstream pipeline of the orifice plate throttling device 3 via a flange connection.

[0041] Hardware Core (I): Integrated Filtration and Sewage Discharge Module 15 This module forms the physical basis for achieving efficient filtration and automatic cleaning. For example... Figure 2 As shown, its key internal component is the filter plate.

[0042] 1. Structure: The filter plate is made of 3 to 5 layers of SS316L stainless steel wire mesh, which are sintered and pressed at high temperature. Before sintering, the wire mesh of the middle layer is chemically etched to form a labyrinthine tortuous microchannel with a width of 100μm-250μm and a depth of 80μm-150μm.

[0043] 2. Flow Path and Mechanism: The fluid enters from inlet 21 and passes vertically through the filter plate. Inside, the fluid is forced to undergo multiple sharp turns 25 at angles 120° to 150° along the labyrinthine flow channel 24. According to the principle of inertial impact, denser solid particles cannot follow the fluid through sharp turns due to inertia, thus impacting and adhering to the flow channel walls and the wire mesh surface, and are effectively intercepted.

[0044] 3. Outlet 22: The purified fluid flows out from outlet 22 and enters the downstream orifice plate throttling device 3 for flow measurement. The module housing has a pressure tap for installing the differential pressure sensor 12 (ΔP2) of the filter assembly, an inlet 21 for connecting the high-pressure backwash pump, and a drain port for connecting the cleaning drain valve 17.

[0045] 4. Software Core: The Logic Diagnostic Control Unit 13 (DCU) is the intelligent core of this invention, and its operating logic is based on... Figure 3 The state machine model shown.

[0046] (1) This logic depends on the following key input variables and thresholds: a) Input variables: b) ΔP1: Orifice plate differential pressure, used to calculate flow rate.

[0047] c) ΔP2: Differential pressure of the filter assembly, characterizing the degree of clogging of the filter plate.

[0048] d)dQ / dt: The instantaneous flow rate change rate calculated from ΔP1, used to determine the stability of the operating condition.

[0049] e) Configurable threshold: f) T1 (Cleaning Trigger Threshold): The upper limit value of ΔP2. If it is exceeded, cleaning may be required. For example, 8 kPa.

[0050] g) T2 (Warning Threshold): The warning line of ΔP2, lower than T1. For example, 4 kPa.

[0051] h) T3 (Flow Stability Threshold): The upper limit of the allowable fluctuation of dQ / dt. If this value is exceeded, the system considers it a process adjustment and will inhibit the cleaning action.

[0052] (2)State Transition Description: a) Normal Operation: The system enters this state after power-on or successful cleaning. The Logic Diagnostic Control Unit 13 (DCU) continuously monitors ΔP1, ΔP2, and dQ / dt. If ΔP2 > T1, the system will enter the Active Monitoring state.

[0053] b) Active Monitoring: After entering this state, the system does not immediately clean but starts to determine whether |dQ / dt| is less than T3. This is a crucial diagnostic step. If |dQ / dt| >= T3, it indicates that the current increase in ΔP2 may be caused by a sharp increase in flow rate, and the system will continue to monitor and wait for the flow to stabilize. If |dQ / dt| < T3, it is confirmed as a real blockage, and the system switches to the Cleaning & Blowdown state.

[0054] c) Cleaning & Blowdown: In this state, the DCU automatically controls the actuator according to the preset program: a. Pre-blow: Quickly open the cleaning and blowdown valve 17 for two seconds to discharge large deposits using the pipeline pressure. b. Backwashing: Close the cleaning and blowdown valve 17, start the high-pressure pump, and perform 5 pulsed backwashings (for example, each pump works for 0.5 seconds and pauses for 1 second) to strip the particles embedded in the maze flow channel with high-pressure reverse fluid. c. Final blowdown: Open the cleaning and blowdown valve 17 again for three seconds to thoroughly discharge all the impurities stripped by the backwashing from the system. d. Stabilization: Close all the actuator valves and wait for 5 seconds to prepare for entering the next state. In addition, if in the Active Monitoring state, ΔP2 continuously remains higher than T1 for more than the preset time (for example, 30 minutes) and still does not meet the cleaning conditions, the system will also forcefully enter the Cleaning & Blowdown state (corresponding to the "Cleaning Timeout" path in the figure) to handle the slow but continuously intensifying blockage.

[0055] d) Verification / Cleaning Check: After cleaning, the system enters this state. Restore the fluid flow, wait for 30 seconds to stabilize, and the DCU reads the new ΔP2 value.

[0056] • If ΔP2 < T2 (Warning Threshold), it is determined that the cleaning is successful, and the system switches back to the Normal Operation state.

[0057] • If ΔP2 ≥ T2, the cleaning effect is considered unsatisfactory. The system will automatically return to the cleaning and sewage discharge state and repeat the cleaning process. If ΔP2 still exceeds the limit after repeating the cleaning process a preset number of times (e.g., 3 times), the system will switch to a system fault state.

[0058] e) System Fault: The system enters this state when multiple cleaning attempts fail, sensor (ΔP1, ΔP2) readings are abnormal (e.g., less than zero), or actuator feedback fails. The DCU will send a critical fault alarm to the main control system (SCADA / DCS) and record the fault code, indicating that manual intervention is required.

[0059] Hardware Core (II): Orifice Plate Liquid Accumulation Monitoring and Drainage Module The key feature of this module is that, in addition to the conventional downstream pressure tapping point 5 of the orifice plate throttling device 3, liquid accumulation monitoring units are added at the top and bottom of the pipeline.

[0060] Liquid accumulation monitoring unit: At a distance of 1-2 times the pipe inner diameter downstream of the orifice plate throttling device 3, an upper first downstream pressure tap 7 and a lower second downstream pressure tap 8 are set radially downstream along the pipe. The distance between the pressure taps is 1 / 3 of the pipe diameter, and each is equipped with a high-precision pressure sensor. The pressure signals from these two pressure taps are sent to the flow computer control unit 6. The flow computer control unit 6 compares the pressure values ​​of the first downstream pressure tap 7 (pressure value represented by P7) and the second downstream pressure tap 8 (pressure value represented by P8) in real time, and determines the liquid accumulation by calculating the difference between "lower pressure tap P8 - upper pressure tap P7" (denoted as ΔP3). 1) Normal operating conditions: ΔP3≤0.005MPa (no liquid accumulation) 2) Warning condition: 0.005MPa<ΔP3≤0.01MPa (small amount of liquid accumulation) 3) Sewage discharge condition: ΔP3 > 0.01 MPa (large amount of liquid accumulation) Sewage discharge components include a collection tank 10 (volume: 0.5m³-1m³, material: carbon steel lined with epoxy resin) and an electric liquid discharge valve 11 (nominal diameter: 25mm, response time: ≤1s). The bottom of the collection tank 10 is equipped with a liquid level sensor (measuring range: 0-1m, accuracy: ±1mm) to double verify the liquid volume.

[0061] When the flow control unit 6 detects that the pressure difference between P8 and P7 exceeds the preset alarm value, it determines that liquid accumulation has occurred in the pipeline. At this time, the flow control unit 6 can automatically open the liquid drain valve 11 to discharge the liquid collected in the collection tank 10. After the draining is completed, the liquid drain valve 11 automatically closes. The entire process is completed online without manual intervention and does not affect the normal metering of natural gas.

[0062] Through the above structure, the present invention achieves comprehensive protection for orifice plate flowmeters by combining "prevention" (filtration and anti-fouling) and "post-treatment" (liquid accumulation monitoring and sewage discharge), effectively solving the problem of inaccurate measurement caused by pollution and liquid accumulation, ensuring the long-term stability and accuracy of the metering system, and has significant practical value and economic benefits.

[0063] To verify the effectiveness of the system of the present invention, a simulation experiment was conducted. The experimental data are recorded in the table below, where T1 is set to 8 kPa, T2 is set to 4 kPa, and the |dQ / dt| stability threshold T3 is set to 5%.

[0064] Table 1 Experimental Data Recording Table The data from EXP-001 shows that the system of this invention can automatically complete the entire closed loop of "normal operation → monitoring → cleaning → verification → restoration to normal operation". The data from EXP-002 shows that the multivariate diagnostic logic of this invention (especially the dQ / dt judgment) can effectively avoid false cleaning caused by process fluctuations (flow rate change rate of -52.0% in EXP-002-02); at the same time, the verification mechanism and repeated cleaning function (EXP-002-04) ensure satisfactory cleaning results even under harsh operating conditions.

[0065] In summary, this invention creatively solves the industry problem of inaccurate measurement caused by fouling in orifice plate flow meters by combining a unique hardware structure with intelligent multivariable diagnostic control logic, providing an efficient, reliable and fully automated solution.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics, characterized in that, include: The orifice plate throttling device (3) is installed on the metering main pipe section (1); The filter assembly (2) is installed on the metering main pipe section (1) and is located upstream of the orifice plate throttling device (3). Pressure taps are provided on the inlet (21) side and the outlet (22) side of the filter assembly (2), and a differential pressure sensor is connected to the pressure tap. The high pressure end of the differential pressure sensor is connected to the pressure tap on the inlet (21) side, and the low pressure end of the differential pressure sensor is connected to the pressure tap on the outlet (22) side. The cleaning and sewage system (14) is located upstream of the orifice plate throttling device (3) and includes a pre-purge and backwash valve (16), a cleaning and sewage discharge valve and a high-pressure pulse backwash pump. The pre-purge and backwash valve (16) and the cleaning and sewage discharge valve are respectively connected to the inlet (21) side and the internal flow channel of the filter plate through the high-pressure pulse backwash pump. The drain assembly, located downstream of the orifice plate throttling device (3), includes a collection tank (10) connected to the bottom of the metering main pipe section (1) and a drain valve (11) installed at the bottom of the collection tank (10), the collection tank (10) being used to collect the liquid accumulated at the bottom of the metering main pipe section (1). The liquid accumulation monitoring unit includes a main differential pressure transmitter (9), a flow computer control unit (6), and a first downstream pressure tap (7) and a second downstream pressure tap (8) set on the metering main pipe section (1). The first downstream pressure tap (7) is set at the upper part of the downstream pipe of the orifice plate throttling device (3), and the second downstream pressure tap (8) is set at the lower part of the downstream pipe of the orifice plate throttling device (3). Pressure sensors are installed on the first downstream pressure tap (7) and the second downstream pressure tap (8). The first downstream pressure tap (7) and the second downstream pressure tap (8) are electrically connected to the flow computer control unit (6) through the pressure sensors. The high pressure end of the main differential pressure transmitter (9) is connected to the upstream pressure tap (4) of the orifice plate, and the low pressure end of the main differential pressure transmitter (9) is connected to the downstream pressure tap (5) of the orifice plate. At the same time, the main differential pressure transmitter (9) and the flow computer control unit (6) are electrically connected. The logic diagnostic control unit (13) contains a comparison circuit, a state machine logic and a drive circuit. The comparison circuit compares the voltage signal of the differential pressure sensor with a preset threshold. The state machine logic outputs drive signals to the pre-purge and backwash valve (16) and the cleaning drain valve (17) in sequence according to the comparison result. The drive circuit converts the drive signal into the opening and closing command of the corresponding valve. The cleaning drain valve (17) opens under the command of the state machine logic to realize the drain step. After the above steps are completed, the comparison circuit reads the voltage signal of the differential pressure sensor (12) of the filter component again and compares it with the preset warning threshold to confirm the cleaning effect.

2. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 1, characterized in that: The filter assembly (2) includes a multi-layer labyrinthine microporous filter plate formed by sintering 3 to 5 layers of SS316L stainless steel wire mesh. The edge of the filter plate is sealed to the inner wall of the metering main pipe section (1) through a flange. The filter plate is provided with a labyrinthine flow channel (24), which has at least 5 turning angles (25) of 120° to 150° and a total length of 30 mm to 45 mm, forming a flow path for inertial impact to capture solid particles. An inlet (21) for connecting a high-pressure pulse backwash pump is reserved on the upstream side of the filter plate, and a drain port for connecting a cleaning drain valve (17) is reserved on the downstream side of the filter plate. The surface of the filter plate is covered with an anti-corrosion coating.

3. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 2, characterized in that: The thickness of each layer of stainless steel wire mesh in the filter plate is 0.15mm, and the sintering temperature is 1150℃. The labyrinthine flow channel (24) has a width of 150µm and a depth of 100µm; The anti-corrosion coating is made of polytetrafluoroethylene and has a thickness of 0.3 mm.

4. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 1, characterized in that: In the sewage discharge assembly, the volume of the liquid collection tank (10) is 0.5m³ to 1.0m³, and the material is carbon steel lined with epoxy resin with a lining thickness of 2mm. The liquid collection tank (10) is equipped with a capacitive liquid level sensor to detect the liquid level in the tank. The liquid level sensor is a capacitive sensor with a measurement range of 0-1m and a resolution of 0.5mm. The liquid discharge valve (11) is connected to the bottom of the liquid collection tank (10) through a sewage discharge pipe.

5. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 4, characterized in that: In the liquid accumulation monitoring unit, the pressure sensor is a piezoelectric sensor with a range of 0-0.2MPa and a sensitivity of 5mV / V; The flow computer control unit (6) includes a comparison circuit, whose input terminal is connected to a piezoelectric pressure sensor installed on the first downstream pressure tap (7) and the second downstream pressure tap (8), and a liquid level sensor installed in the liquid collection tank. When the comparison circuit detects that the pressure difference between the upper and lower parts of the metering main pipe section (1) exceeds the cleaning trigger threshold T1 or the liquid level exceeds the threshold H, it outputs a drive signal to the liquid discharge valve (11) to realize liquid discharge.

6. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 1, characterized in that: The differential pressure sensor is a piezoresistive sensor with a rated measurement range of 0-0.5 MPa; The high-pressure pulse backwash pump is a two-stage centrifugal pump with a maximum output pressure of 1.5MPa and a built-in proportional valve to achieve pressure regulation within the range of 0.5MPa-1.5MPa.

7. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 1, characterized in that: The internal programmable logic controller uses a ladder diagram to implement state machine logic. Its internal comparison circuit includes an analog-to-digital converter, which converts the analog voltage output by the differential pressure sensor into a digital signal and compares it with the stored warning threshold T2.

8. The intelligent anti-clogging system for orifice plate flowmeters based on multivariate diagnostics according to claim 1, characterized in that: The system includes an RS-485 communication interface and outputs digital alarm codes according to the Modbus RTU protocol.

9. A method for intelligent anti-clogging of an orifice plate flowmeter based on multivariable diagnosis using the intelligent anti-clogging system based on multivariable diagnosis as described in any one of claims 1-8, comprising the following steps: Normal operating condition: continuously monitor the main differential pressure ΔP1 and the differential pressure ΔP2 of the filter component (2), and calculate and output the flow rate based on the main differential pressure ΔP1. At the same time, calculate the flow rate change rate dQ / dt based on the main differential pressure ΔP1. Blockage warning and diagnosis: When the differential pressure ΔP2 of the filtration component (2) is monitored to exceed the preset cleaning trigger threshold T1, the system enters the active monitoring state; in this state, the system will determine whether the flow rate change rate dQ / dt is less than the preset stability threshold T3; When |dQ / dt| < T3, the system confirms that a blockage has occurred; Automatic cleaning and sewage discharge cycle: After confirming the blockage, the system automatically enters the cleaning and sewage discharge state and sequentially executes a series of actions including pre-purging, high-pressure pulse backwashing, final sewage discharge, and stabilization, or sequentially executes a series of actions including isolation, pre-purging, high-pressure pulse backwashing, final sewage discharge, and stabilization; Verification of cleaning effect: After the cleaning and sewage discharge cycle ends, the system enters the verification state; after restoring normal flow and waiting for the fluid to stabilize, the new baseline value of the differential pressure ΔP2 of the filtration component (2) is read again. If the new baseline value is lower than the warning threshold T2, it proves that the cleaning is effective and the system returns to the normal operating state; if the new baseline value is still greater than or equal to the warning threshold T2, the system can repeat the automatic cleaning and sewage discharge cycle or issue a serious fault alarm after multiple attempts fail.

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