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CN-122016955-A - Multi-mode detection method for integrity of coating on inner wall of heat exchanger tube bundle

CN122016955ACN 122016955 ACN122016955 ACN 122016955ACN-122016955-A

Abstract

The invention discloses a multi-mode detection method for the integrity of a coating on the inner wall of a heat exchanger tube bundle, and belongs to the technical field of performance evaluation and corrosion monitoring of protective coatings on metal surfaces. The method takes electrochemical impedance spectroscopy EIS as a core, combines electrokinetic polarization PDP and open circuit potential OCP monitoring, and assists in endoscopic visual inspection to realize nondestructive, localization and dynamic evaluation and life prediction of the inner wall coating of the heat exchanger tube bundle. By adopting the multi-end beam-shaped electrode design, the whole performance evaluation and the local defect positioning of the coating can be realized in the tube bundle, and the problems that the traditional method is single in detection means and difficult in real-time early warning and positioning are solved. The system has high integration level, and is suitable for on-line intelligent monitoring and maintenance management of industrial sites.

Inventors

  • ZHAO LIN
  • YAN MAOCHENG
  • FAN WEIHUA
  • GAO BOWEN

Assignees

  • 中国科学院金属研究所

Dates

Publication Date
20260512
Application Date
20260128

Claims (8)

  1. 1. The multi-mode detection method for the integrity of the coating on the inner wall of the heat exchanger tube bundle is characterized by comprising the following steps of: (1) Electrolyte solution is filled in a tube bundle of the heat exchanger, a multi-end bundle-shaped counter electrode is inserted, the electrode is formed by integrating a plurality of single electrodes with exposed platinized sections arranged at intervals, and the exposed sections of each electrode are distributed along the length direction of the tube bundle; (2) The tube bundle is used as a working electrode, the multi-end beam-shaped counter electrode is used as a counter electrode and a reference electrode, connecting to a multi-channel electrochemical measurement device; (3) Performing a multi-modal electrochemical assay comprising: a) The open circuit potential is continuously monitored, so that early warning of coating defects is realized; b) Electrochemical impedance spectrum test, evaluating the state of the coating and carrying out defect positioning; c) Potentiodynamic polarization test, finally evaluating the protection effect and corrosion condition of the coating; (4) And determining an abnormal section according to the electrochemical detection result, and performing visual positioning and morphology recording by adopting an endoscope.
  2. 2. The multi-mode detection method for the integrity of the coating on the inner wall of the heat exchanger tube bundle according to claim 1, wherein the length of a single electrode of the multi-end bundle-shaped counter electrode is 3-10m, the length of a bare platinized segment is 0.1-0.5m, and the interval between adjacent bare segments is 0.5-2m.
  3. 3. The method for multimodal detection of the integrity of the coating on the inner wall of a heat exchanger tube bundle according to claim 1, wherein the electrolyte solution is a 1M NaCl solution.
  4. 4. The multi-mode detection method for the integrity of the coating on the inner wall of the heat exchanger tube bundle according to claim 1, wherein the open circuit potential monitoring frequency is once every 1-10 minutes, and early damage of the coating is judged through the potential negative shift amplitude and the trend.
  5. 5. The method for multi-modal detection of the integrity of the coating on the inner wall of a heat exchanger tube bundle according to claim 1, wherein the electrochemical impedance spectroscopy test is performed in the frequency range of 10 mHz-100 kHz, the shielding performance of the coating is evaluated through the low-frequency impedance modulus, and the defects are located through the local impedance change.
  6. 6. The multi-mode detection method for the integrity of the coating on the inner wall of the heat exchanger tube bundle according to claim 1, wherein the potentiodynamic polarization scanning speed is 0.5-2 mV/s, and the scanning range is carried out within +/-0.3V based on the open-circuit potential.
  7. 7. The method for multimodal detection of heat exchanger tube bundle inner wall coating integrity according to claim 1, further comprising obtaining one or more parameters of film resistance, pore resistance, charge transfer resistance according to electrochemical impedance spectrum fitting.
  8. 8. The multi-mode detection method for the integrity of the coating on the inner wall of the tube bundle of the heat exchanger according to claim 1, wherein the endoscope probe can be positioned to a specific section in the tube bundle for image acquisition according to the electrode number corresponding to the electrochemical abnormality signal.

Description

Multi-mode detection method for integrity of coating on inner wall of heat exchanger tube bundle Technical Field The invention relates to the technical field of performance evaluation and corrosion monitoring of protective coatings on metal surfaces, in particular to an integrity multi-mode intelligent detection method suitable for internal coatings of heat exchanger tube bundles. Background The heat exchanger is a key device in the fields of chemical industry, electric power, ships and the like, and the inside of a tube bundle is always in a high-temperature, high-pressure, high-flow-rate and corrosive medium environment. To extend the service life, the inner walls of the tube bundle are often sprayed with an anti-corrosive coating, such as an epoxy coating, a phenolic coating, and the like. The inner wall of the tube bundle has small space, is difficult to spray by the conventional method, is easy to form a spray dead angle, and has various defects of spraying leakage and pinholes. And after a certain operation period, the surface of the coating is easy to crack, break and the like. The above-mentioned drawbacks will seriously affect the service life of the coating, resulting in failure of the coating. The existing heat exchanger tube bundle inner wall coating defect detection method has more problems, and physical detection means such as endoscopy and the like are adopted for performance evaluation. The traditional pressure drop method, vortex or endoscope can only find macroscopic damage and can not early warn early failure, and a single EIS only gives 'average' information, so that positioning is difficult to realize. In the prior art, although research on coating evaluation by adopting an electrochemical impedance spectrum or a polarization curve is carried out, the research is limited to a laboratory environment, and a systematic multi-mode intelligent detection system is not formed yet because the research is not combined with on-site online monitoring, intelligent early warning and life prediction. Therefore, there is a need for an intelligent evaluation method with impedance detection as a core and multi-modal fusion. Disclosure of Invention The invention aims to provide a multi-mode intelligent detection and evaluation method for the integrity of a coating inside a heat exchanger tube bundle, which aims to solve the problems that the detection means is single, the real-time monitoring cannot be realized and the defect positioning is difficult in the prior art. The multi-mode detection method for the integrity of the inner wall coating of the heat exchanger tube bundle is a multi-mode nondestructive detection and service life evaluation method for the integrity of the inner wall coating of the heat exchanger tube bundle, which is suitable for the multi-mode intelligent detection method for the integrity of the inner wall coating of the heat exchanger tube bundle, and is based on Electrochemical Impedance Spectroscopy (EIS), integrates electrokinetic potential polarization (PDP), open Circuit Potential (OCP) and local impedance imaging, and can accurately and intuitively position the defects of the inner wall coating by combining tube bundle endoscopy. In order to achieve the above purpose, the invention adopts the following technical scheme: A multi-mode detection method for the integrity of a coating on the inner wall of a heat exchanger tube bundle comprises the following steps: 1) And the measurement electrode is installed and detected by adopting a special multi-end beam-shaped electrode, and the design simultaneously takes the whole evaluation and defect positioning into consideration. When in use, the inner wall of the heat exchanger tube bundle is filled with electrolyte solution, and 1M NaCl solution is generally selected. Both ends are sealed by rubber plugs. The multi-end beam-shaped counter electrode passes through the middle of the rubber plug and penetrates through the inside of the whole heat exchanger tube bundle. And the multi-end beam-shaped counter electrode is adopted to realize the integral evaluation of the coating and the positioning of the defect position. The multi-terminal beam electrode design is shown in fig. 1, and a plurality of local conductive electrodes S1, S2, S3 are used. . . The electrode is integrated, and the length of a single electrode can be different according to the design of the tube bundle, and is generally about 5 m. The single electrode adopts copper wire, and both ends remain measuring port, are connected with measuring equipment. The single electrode S1 is exposed outside by 0.2m at the position 0.8m on one side of the initial position, and other electrodes are kept sealed and insulated. The surface of the exposed area is platinized, and the exposed area is fully covered. The single electrode S2 has a 0.2m platinized treatment area at a starting position of 1.8m, and the other electrode S2 is kept sealed and insulated. And by analogy, selecting diffe