A substation fire-fighting pipe network fault detection method based on fluorescent tracer

Abstract

The application discloses a kind of based on fluorescent tracer substation fire-fighting pipe network flaw detection method, comprising the following steps: S1: the outer wall of fire-fighting pipe network is cleaned, rusted and dry treated;S2: coating fluorescent response flaw detection coating and curing;S3: fluorescent tracer is mixed with fire-fighting water;S4: start fire-fighting pump, and detection medium is filled into fire-fighting pipe network and maintains design pressure maintaining value;S5: after pressure maintaining, the outer wall of pipe network is checked;S6: if found abnormality is marked, enter S7, if no abnormality is found, fire-fighting pipe network is temporarily defect-free, enter S9;S7: repair the leakage point position marked in S6;S8: return S4 and recheck;S9: complete flaw detection work;The flaw detection method is replaced by radioactive tracer medium by safe fluorescent tracer medium, and using fluorescent response flaw detection coating and optical identification means, realize the rapid positioning and intuitive discrimination of fire-fighting pipe network leakage point position, greatly improve detection efficiency and accuracy.

Description

Technical Field

[0001] This invention relates to the field of substation safety management and control technology, and in particular to a method for detecting flaws in substation fire protection pipelines based on fluorescence tracing. Background Technology

[0002] As a critical node in the power system, the safe and stable operation of substations directly affects the reliability of the entire power grid. Among the various safety facilities in substations, fire protection networks play an irreplaceable role. Substations are filled with a large number of oil-immersed equipment (such as transformers and reactors) and high-voltage cables, all of which are high-fire-load areas. Once a fire breaks out, it spreads extremely rapidly. Fire protection networks (especially fixed fire extinguishing systems such as water spray and fine water mist) can be automatically or manually activated at the first sign of a fire to precisely or comprehensively extinguish the fire on the burning equipment. Before the arrival of the fire brigade, the fire protection network is the most effective means of controlling the fire and preventing it from spreading to other equipment (leading to an escalation of the accident). Especially for large oil-immersed transformers, water spray systems can quickly cool the equipment casing and emulsify the oil at high temperatures, suppressing combustion and explosion. In the cable layers or tunnels of substations, cable fires are often concealed and produce toxic fumes. Fire protection networks can effectively suppress cable fires in confined spaces without anyone entering. As a core component of the power grid, substations contain equipment worth tens of millions or even hundreds of millions of yuan. The efficient activation of fire protection pipe networks can minimize equipment damage and reduce direct economic losses. Therefore, the maintenance and regular testing of fire protection pipe networks are crucial and cannot be ignored.

[0003] If welded joints, flange connections, tees, elbows, or local pipe wall defects exist in the substation fire protection piping network, they are prone to leakage during later operation. This not only affects the reliability of fire water supply but also increases operation and maintenance costs. Currently, the overall hydrostatic test is used for flaw detection in key areas of the fire protection piping network. However, the overall hydrostatic test can only reflect whether there is a leak in the system, and it is difficult to accurately locate specific defects. In addition, although ultrasonic, radiographic, or partial disassembly inspections can be used for defect identification, they have high equipment requirements, are complex to operate, and have limited coverage, especially in buried, suspended ceiling, mezzanine, or complex laying environments. Therefore, there is an urgent need for a safer, more intuitive, and easy-to-implement flaw detection solution for fire protection piping networks. Summary of the Invention

[0004] To overcome the above problems, the purpose of this invention is to provide a flaw detection method for substation fire protection pipelines based on fluorescence tracing. This flaw detection method replaces the radioactive tracing medium with a safe fluorescent tracing medium and utilizes a fluorescent response flaw detection coating and optical recognition methods to achieve rapid location and intuitive identification of leakage points in the fire protection pipeline network.

[0005] The technical solution adopted in this invention is:

[0006] A method for flaw detection of substation fire protection pipelines based on fluorescence tracing includes the following steps:

[0007] S1: Clean, remove rust, and dry the outer wall of the fire protection pipe network;

[0008] S2: Apply a fluorescent response flaw detection coating evenly to the easily leaking areas on the outer wall of the fire protection pipeline and then cure it;

[0009] S3: Add the fluorescent tracer to the fire-fighting water at the set concentration and mix thoroughly;

[0010] S4: Start the fire pump and fill the fire pipeline with the detection medium containing fluorescent tracer that has been fully mixed in S3, and maintain the design pressure value for 24 to 48 hours;

[0011] S5: After the pressure holding period is completed, the outer wall of the pipeline network shall be inspected by visible light inspection or ultraviolet light irradiation.

[0012] S6: If an area with enhanced color development or abnormal fluorescence is found, it is identified as a suspected leak point and marked. Proceed to S7. If no enhanced color development or abnormal fluorescence is found, the fire protection pipeline network is not defective. Proceed to S9.

[0013] S7: Discharge the test medium in the fire protection pipeline, flush with clean water 2-3 times, and repair the leak points marked in S6;

[0014] S8: Return to S4 for re-inspection;

[0015] S9: Complete the flaw detection work.

[0016] As a further description of the present invention, the easily leaking areas in S2 include welded joints, flange connections, tee bends, and areas with historical defects.

[0017] As a further description of the present invention, the fluorescent response flaw detection coating in S2 includes materials such as weather-resistant and waterproof base material, fluorescent pigment, dispersant, film-forming aid, weather-resistant aid, and deionized water. All materials are mixed evenly in a certain proportion and then coated by brushing or spraying.

[0018] As a further description of the present invention, the coating thickness of the fluorescent response flaw detection coating is 0.5mm-1.2mm.

[0019] As a further description of the present invention, the concentration of the fluorescent tracer in S3 is determined based on the fire-fighting pipeline volume, branch length, and target detection sensitivity, and the formula for calculating the concentration is as follows:

[0020] ;

[0021] in, To determine the final concentration of the tracer that needs to be added to the fire protection pipe network,

[0022] This is the lowest detectable concentration of the instrument in an ideal water sample.

[0023] For safety reasons,

[0024] This is the physical length of the longest branch in the fire protection pipe network.

[0025] For reference length,

[0026] The length attenuation coefficient,

[0027] This is the total volume of the fire protection pipe network.

[0028] The volume of water sample required for a single sampling or testing.

[0029] As a further description of the present invention, the mass ratio of the fluorescent tracer to the fire-fighting water in the S3 addition concentration is 1:5000 to 1:20000.

[0030] As a further description of the present invention, in step S5, an image acquisition terminal may also be used to take pictures or record videos of the fluorescent area.

[0031] As a further description of the present invention, the fluorescent tracer in S3 is a water-soluble fluorescent tracer, including one or more combinations of sodium fluorescein, rhodamine B, or acridine orange.

[0032] As a further description of the present invention, the specific method for maintaining the design pressure value in S4 is as follows: after the fire pump is started to fill water and purge the air in the pipe, all outlet valves are closed, and the pressure in the pipe is maintained within ±5% of the design pressure value by the pressure boosting pump. Pressure data is recorded every 8 hours during the pressure holding period.

[0033] As a further description of the present invention, the ultraviolet light irradiation method in S5 uses an ultraviolet light wavelength of 365nm or 395nm, and the ambient light illuminance during irradiation is not higher than 50 lux.

[0034] The beneficial effects of this invention are:

[0035] 1. Significantly improves the detection rate and location accuracy of minute leaks in fire protection pipelines. This flaw detection method enhances detection sensitivity through a dual response mechanism of "fluorescent tracer + fluorescent responsive coating." During a pressure holding process lasting 24-48 hours, even extremely small leaks with a flow rate of only milliliters / hour are sufficient to allow a sufficient amount of fluorescent tracer to seep out of the pipe wall and infiltrate the fluorescent responsive coating on the outer wall. Under 365nm or 395nm ultraviolet light irradiation, these micro-leaks, completely imperceptible to the naked eye, will appear as clear and bright fluorescent spots. Experimental verification shows that this method can detect penetrating defects with a diameter of less than 0.1mm, with a sensitivity 2-3 orders of magnitude higher than the traditional pressure testing method, ensuring the fire safety of substations.

[0036] 2. This method enables precise location of leaks. Fluorescent signals are directly displayed at the leak point, accurately indicating its location. For overhead pipelines, the fluorescent dots are visually displayed on the pipe wall surface; for buried pipelines, the coating can be observed at inspection wells or examined using an endoscope; for pipelines penetrating walls, the fluorescent signal appears along the leakage path. This precise location capability upgrades maintenance work from "vague investigation" to "precision strikes," significantly reducing unnecessary excavation, dismantling, and repair work.

[0037] 3. Significantly improves maintenance efficiency, shortens pipeline downtime, and enables large-scale rapid screening. The final judgment of maintenance and repair using this flaw detection method only requires maintenance personnel to inspect the pipeline with a UV lamp after the pressure holding is completed. For overhead pipelines, drones equipped with UV imaging equipment can be used for automatic inspection, which is even more efficient. Attached Figure Description

[0038] Figure 1 This is a flowchart of a substation fire protection pipeline flaw detection method based on fluorescence tracing proposed in this invention. Detailed Implementation

[0039] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0042] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0043] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for 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. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] like Figure 1 As shown, this invention provides a method for flaw detection of substation fire protection pipelines based on fluorescence tracer technology. This method cleverly combines the high sensitivity of fluorescence tracer technology with the reliability of pressure testing. By pre-coating the outer wall of the fire protection pipeline with a fluorescent responsive coating and adding a fluorescent tracer to the detection medium, efficient and accurate location of leaks in the pipeline is achieved. When a leak occurs, water carrying the fluorescent tracer seeps out and reacts specifically with the fluorescent responsive coating on the pipe wall, producing a significant fluorescence signal or color change, thus making even minute leaks readily apparent. This method not only greatly improves detection efficiency and accuracy but is also simple to operate and cost-effective, making it ideal for the regular maintenance of fire protection pipelines in the complex environment of substations.

[0046] Example 1:

[0047] A method for flaw detection of substation fire protection pipelines based on fluorescence tracing includes the following steps:

[0048] S1: Clean, remove rust, and dry the outer wall of the fire protection pipe network.

[0049] In this embodiment, this step is fundamental to ensuring that the subsequent coating can adhere firmly and perform optimally. Substation fire protection pipelines are located in outdoor or semi-outdoor environments for extended periods, inevitably leading to the accumulation of dust, oil, and varying degrees of corrosion on the pipe walls. Directly coating these contaminants or rust layers will severely affect the adhesion between the fluorescent response coating and the substrate, causing the coating to peel off and interfering with the generation and observation of fluorescent signals.

[0050] In this embodiment, a high-pressure water gun combined with a neutral detergent is first used to preliminarily rinse the outer wall of the fire-fighting pipeline to remove surface dust, dirt, and oil. For areas with severe oil contamination, an appropriate amount of organic solvent (such as acetone or industrial alcohol) can be used for wiping and cleaning. Subsequently, for the rust layer on the pipe wall surface, an angle grinder with a wire brush or abrasive wheel is used for mechanical rust removal. The rust removal grade should meet the St2 or Sa2 standard in relevant regulations, meaning that there should be no visible grease or dirt on the surface, and it should be firmly adhered to its substrate. If conditions permit, sandblasting can be used for important pipe sections or areas with severe rust to achieve a higher level of cleanliness and roughness, further enhancing the coating adhesion. After rust removal, dry compressed air is used to blow away the pipe wall surface to remove residual dust and particles. Finally, the treated pipeline is allowed to dry completely in natural conditions to ensure that the pipe wall surface is absolutely dry and free of moisture. If the ambient humidity is too high, a hot air blower can be used for auxiliary drying.

[0051] S2: Apply a fluorescent response flaw detection coating evenly to the easily leaking areas on the outer wall of the fire protection pipeline and then cure it.

[0052] After surface treatment is completed, key and vulnerable links in the pipeline network need to be protected and monitored. The easily leaking areas referred to in S2 are high-risk locations identified based on fluid mechanics principles and engineering experience.

[0053] Specifically, the areas prone to leakage include welded joints, flange connections, tee bends, and areas with historical defects.

[0054] In this embodiment, welded joints are high-risk areas for stress concentration and potential microcracks due to the presence of heat-affected zones and weld formation defects; flange connections rely on gaskets for sealing, and gasket aging or uneven bolt preload can easily lead to leakage; at tees and elbows, the medium flow direction changes, and the pipe wall is easily thinned due to long-term scouring and impact; historical defect areas are places where problems have occurred and have been repaired, and the risk of leakage recurring is relatively high.

[0055] The fluorescent response flaw detection coating used in this embodiment is a functional composite coating. The fluorescent response flaw detection coating comprises a weather-resistant and waterproof base material, fluorescent pigment, dispersant, film-forming aid, weather-resistant aid, and deionized water. The weather-resistant and waterproof base material can be acrylic emulsion, epoxy resin emulsion, or polyurethane emulsion, etc., providing the coating with basic film-forming properties and adhesion to the substrate, while also imparting excellent weather resistance and waterproofness, ensuring that the coating does not chalk or crack during long-term outdoor use. The fluorescent pigment is the core functional component of this coating. Its mechanism of action is that when leaked water carries specific metal ions or encounters a specific pH environment, the molecular structure of the fluorescent pigment changes, thereby producing a fluorescence "on" or "quench" effect. For example, 8-hydroxyquinoline derivative fluorescent dyes can be used, which can undergo complexation reactions with metal ions such as iron and aluminum, emitting bright fluorescence under ultraviolet light. The dispersant is used to ensure that the fluorescent pigment is uniformly dispersed in the base material, preventing agglomeration and ensuring coating performance. Film-forming aids can lower the minimum film-forming temperature of emulsions, enabling coatings to form continuous and dense coatings over a wider temperature range. Weather-resistant additives (such as UV absorbers and light stabilizers) can delay the aging and degradation of coatings in outdoor environments, extending their service life.

[0056] All materials are mixed in a specific ratio. In a concrete formulation example, the mass percentages of each component can be: 100 parts weather-resistant and waterproof base material (e.g., pure acrylic emulsion), 5-15 parts fluorescent pigment (e.g., 8-hydroxyquinoline-5-sulfonic acid), 0.5-1.5 parts dispersant (e.g., sodium polycarboxylate), 2-6 parts film-forming aid (e.g., alcohol ester dodecyl), 1-3 parts weather-resistant aid (e.g., benzotriazole UV absorber), and 10-30 parts deionized water. During preparation, the dispersant and a portion of the deionized water are first mixed. The fluorescent pigment is then slowly added while stirring, and the mixture is dispersed at high speed for 30 minutes to form a color paste. The color paste is then added to the weather-resistant and waterproof base material, followed by the film-forming aid, weather-resistant aid, and the remaining deionized water. The mixture is stirred at low speed until homogeneous, and finally filtered through a sieve.

[0057] The prepared coating is evenly applied to the leak-prone areas treated with S1 by brushing or spraying. For irregular surfaces such as welds, brushing offers better operability, ensuring the coating fully penetrates the weld recesses. For large flanges or pipes, spraying is more efficient and produces a more uniform coating. The coating thickness for the fluorescent response flaw detection is 0.5mm-1.2mm. A coating that is too thin may not provide sufficient fluorescent signal intensity and offers insufficient protection; a coating that is too thick is prone to cracking or sagging during curing and increases costs. Controlling the thickness within this range ensures both the mechanical strength and protective performance of the coating, while also ensuring the effective excitation and identification of the fluorescent signal. After coating, depending on the type of base material used, allow it to cure at room temperature for 24-72 hours, or heat-cure according to the product instructions, until the coating is completely dry and forms a strong, transparent protective film.

[0058] S3: Add the fluorescent tracer to the fire-fighting water at the set concentration and mix thoroughly.

[0059] After the fluorescent responsive coating is applied to the outer walls of the S1 and S2 fire-fighting pipe networks, this step involves installing "markers," i.e., fluorescent tracers, on the detection media inside the fire-fighting pipe network. In this embodiment, the fluorescent tracer is a water-soluble fluorescent tracer, including one or more combinations of sodium fluorescein, rhodamine B, or acridine orange. These tracers have the advantages of good water solubility, stable properties, and the ability to be excited to emit strong fluorescence even at extremely low concentrations. They are also relatively safe for humans and the environment, meeting the requirements for fire-fighting water. When sodium fluorescein is selected, its excitation wavelength is approximately 490 nm and its emission wavelength is approximately 514 nm; the excitation wavelength of rhodamine B is approximately 550 nm and its emission wavelength is approximately 570 nm. These wavelengths can all be excited using a portable ultraviolet lamp or a light source of a specific wavelength.

[0060] The concentration of the fluorescent tracer is a key parameter that determines the detection sensitivity and controls the detection cost. If the amount added is too small, the concentration of tracer that leaks out will be too low, and it may not be effectively captured and responded to by the fluorescent reactive coating; if the amount added is too large, it will waste reagents, increase detection costs, and may impose an unnecessary burden on the environment.

[0061] Specifically, the concentration of the fluorescent tracer in S3 is determined based on the fire duct network volume, branch length, and target detection sensitivity. The formula for calculating the concentration is as follows:

[0062] ;

[0063] in, The final concentration of the tracer to be added to the fire protection pipeline network (unit: g / L or mass ratio ppm).

[0064] The minimum detectable concentration of the instrument in an ideal water sample is given by the unit [missing information]. This value should remain consistent. It can be obtained through prior laboratory testing. For example, for Rhodamine B, a concentration of 0.1 ppb (μg / L) might be detectable in pure water using a portable fluorescence detector, while the clear detection threshold using a 365nm UV lamp and human eye observation might be 1-10 ppb. In this embodiment, if visual observation with a UV lamp is used as the primary determination method, 5 ppb is acceptable.

[0065] For safety margin, it is usually taken as Redundancy is introduced considering factors such as adsorption on the inner wall of the pipeline, quenching of impurities in the water, and dilution by water flow.

[0066] This is the physical length of the longest branch in the fire protection pipeline network, in meters (m). This parameter reflects the distance the tracer needs to travel from the injection point to the farthest end of the network; the longer the distance, the more pronounced the dilution and adsorption effects along the way.

[0067] The reference length is a constant used for normalization, with the unit being meters. It is usually taken as the standard pipeline length used when calibrating the testing instrument or an empirical benchmark value (such as 100m) and is used to quantify the attenuation compensation caused by the length.

[0068] The length attenuation coefficient is a dimensionless empirical parameter representing the proportion of additional concentration compensation required per unit distance relative to a reference length. Its value typically ranges from 0.1 to 0.5. In this embodiment, for metal pipes, 0.2 is acceptable.

[0069] The total volume of the fire protection pipe network, in L or m³.

[0070] This refers to the volume of water sample required for a single sampling or testing. (Units: ...) Maintain consistency. Because the detection method of this invention involves observing the pipe wall coating, rather than collecting water samples, therefore... It is a theoretical reference value. In the formula, This reflects the ratio of macroscopic network concentration to local concentration at a microscopic leak point. It can be understood that the tracer at the leak point originates from a small portion of the surrounding water; therefore, to ensure the concentration of the seepage at the leak point is sufficiently detectable, the average concentration of the entire network needs to be appropriately increased. To simplify the calculation, we can... Let's set it to a unit volume, such as 1L. This is the value of the total volume of the pipeline network.

[0071] Assume the total volume of the fire protection pipeline network of a certain substation The longest branch is 5000L. The value is 150m. Rhodamine B was selected as the tracer. The concentration is 0.005 mg / L (i.e., 5 ppb). Take SF = 3. , =100m, =1L. The calculation is as follows:

[0072] =0.005mg / L×3×(1+0.2×150 / 100)×(5000L / 1L)=97.5mg / L.

[0073] The concentration of the tracer should be 97.5 mg / L, which is approximately a mass ratio of 1:10256. Based on calculations, the mass ratio of fluorescent tracer to fire-fighting water in the S3 dosage is typically controlled between 1:5000 and 1:20000, which is consistent with the above calculations. In actual operation, the calculated amount of fluorescent tracer can be dissolved in a small amount of warm water in a container to prepare a stock solution. This stock solution is then slowly poured into the fire pump through its suction pipe or the fire water tank's inlet, while maintaining pump circulation or using other stirring methods to ensure the tracer is evenly mixed throughout the entire pipe network system.

[0074] S4: Start the fire pump and fill the fire pipeline with the detection medium containing fluorescent tracer that has been fully mixed in S3, and maintain the design pressure value for 24 to 48 hours.

[0075] After thorough mixing, start the fire pump to fill the entire fire pipeline network with the detection medium (water) containing the fluorescent tracer. During the filling process, open the air vent valve at the highest point of the pipeline network until no more air bubbles appear continuously in the discharged water flow, ensuring that the air in the pipeline network is completely purged to avoid affecting pressure stability and detection results. After the pipeline network is full of water, close all air vent valves and outlet valves to form a closed system. Continue to start the fire pump or use a dedicated pressure booster pump to slowly increase the pressure in the pipeline network to the design holding pressure value. This design holding pressure value should be determined according to the technical specifications of the fire pipeline network and is usually the system's working pressure. For example, for a temporary high-pressure fire water supply system, the test pressure may be 1.5 times the working pressure.

[0076] Maintain the design pressure for 24 to 48 hours. The duration of the pressure maintenance depends on the size and complexity of the pipeline network and the expected leak detection sensitivity. For newly built or critical pipeline networks in operation, 48 hours is recommended to allow sufficient time for minor leaks to occur and for enough tracer to seep out. During the pressure maintenance period, pressure gauge readings may fluctuate due to changes in ambient temperature or minor leaks. This example requires maintaining the pressure within ±5% of the design pressure. If the pressure drops too quickly beyond this range, it indicates a significant leak, and the test should be stopped, the leak located, and the test resumed. For precise pressure control, a pressure-stabilizing pump or pressure tank can be used in conjunction with a pressure controller for automatic pressure replenishment, and the pressure change curve throughout the entire pressure maintenance period should be recorded.

[0077] S5: After the pressure holding period is completed, the outer wall of the pipeline network shall be inspected by visible light inspection or ultraviolet light irradiation.

[0078] After a 24-48 hour pressure test, if leaks are found in the pipeline, water containing fluorescent tracers will seep out of the pipe wall under pressure and soak into the pre-coated fluorescent response flaw detection coating. Inspection work can then commence after the pressure test is completed.

[0079] There are two inspection methods. One is visible light inspection, which is mainly for certain types of fluorescent responsive coatings. When these coatings come into contact with leaked water, in addition to the fluorescence effect, a visible color change will occur (e.g., from white to yellow or red). This can be observed directly with the naked eye under natural light or flashlight illumination. The other, more advanced and sensitive method is ultraviolet (UV) light irradiation. Inspectors use a portable UV lamp to irradiate the area coated with the fluorescent responsive flaw detection coating. The UV light irradiation method uses a wavelength of 365nm or 395nm, which is the optimal excitation wavelength range for most commonly used fluorescent tracers (such as sodium fluorescein and rhodamine B). Under UV irradiation, if there is a leak in the area, the exudate will react with the coating and emit bright characteristic fluorescence (e.g., rhodamine B emits orange-red fluorescence, and sodium fluorescein emits yellow-green fluorescence), creating a strong contrast with the background coating.

[0080] To obtain optimal observation results, the inspection should be conducted in a low-light environment, requiring an ambient light level not exceeding 50 lux, such as at night or by setting up a shaded area. Inspectors should walk slowly along the pipeline, evenly illuminating each potentially leak-prone area with a UV lamp. Once a suspected leak is found, it should be marked and re-verified using a higher-powered UV lamp or fluorescence detector. To record the inspection process and results, an image acquisition terminal can be used in step S5 to photograph or record videos of the fluorescent areas. This can be a DSLR camera equipped with a specific filter, an industrial endoscope with night vision and fluorescence enhancement capabilities, or a drone. By taking photos and videos, the inspection results can be archived in image form, establishing a visualized pipeline health record for easy later comparison and traceability. The image acquisition terminal can clearly record the location, shape, and size of the fluorescent spots, providing an intuitive basis for subsequent maintenance decisions.

[0081] S6: If an area with enhanced color development or abnormal fluorescence is found, it is identified as a suspected leak point and marked, proceeding to S7; if no enhanced color development or abnormal fluorescence is found, the fire protection pipeline network is currently without defects, proceeding to S9.

[0082] This is the judgment stage of the entire inspection results. If, during the S5 inspection, a color change in the coating is observed under visible light, or abnormal fluorescent bright spots or areas are observed under ultraviolet light, the location is determined to be a suspected leak point. At this time, the inspectors need to use a marker or spray paint to clearly and permanently mark the leak point on the outer wall of the pipe and record its coordinates. If, after a comprehensive and meticulous inspection, no color enhancement or fluorescence abnormalities are found in any coated area, it can be concluded that the fire protection pipeline network is defect-free under the current test pressure and time conditions, and the flaw detection work can be successfully completed.

[0083] S7: Discharge the test medium in the fire protection pipeline, rinse with clean water 2-3 times, and repair the leak points marked in S6.

[0084] Once a leak is detected, further action is required. First, open the drain valve at the bottom of the fire hydrant network to safely and environmentally discharge the detection medium containing the fluorescent tracer into the wastewater treatment system or a designated location, avoiding environmental pollution. After discharge, inject clean tap water into the network, start the fire pump for circulation flushing, and then discharge again. Repeat this process 2-3 times until no obvious fluorescent tracer is detected in the discharged water. After cleaning, the leak point marked in S6 can be repaired. Depending on the specific leak, repair measures may include: replacing the gasket at the flange connection and retightening the bolts; repairing leaks in welds; replacing or patching corroded or perforated pipe sections, etc. Repair work should be carried out by qualified professionals and in accordance with relevant construction specifications.

[0085] S8: Return to S4 for re-inspection.

[0086] After the repair work is completed, the problem cannot be considered completely resolved. A re-inspection must be conducted to verify the repair effectiveness. According to S8 requirements, it is necessary to return to step S4, which involves refilling the pipeline with a detection medium containing a fluorescent tracer and conducting a pressurized test for 24-48 hours again. During the re-inspection, special attention should be paid to the areas that were marked and repaired, as well as surrounding potentially affected areas. If no fluorescent signal reappears in these areas during the re-inspection, the repair is considered successful. If the signal reappears, it indicates that the problem has not been fundamentally resolved or that the repair process introduced new defects, requiring repeated repairs and testing until all leaks are completely eliminated.

[0087] S9: Complete the flaw detection work.

[0088] When no defects are found during all inspections, or when any defects found are repaired and pass a re-inspection, the fluorescent tracer-based flaw detection work on the substation fire protection pipeline network can be declared complete. The testing unit should issue a formal testing report, which should record in detail the testing process, the concentration of the tracer added, the holding pressure and time, the location of the leaks found and their treatment, and the final re-inspection results, and attach the image data taken in S5 as evidence.

[0089] Example 2:

[0090] In S2, considering the environmental differences of substations in different regions, higher requirements are placed on the weather resistance of the coating in areas with strong corrosive environments and intense ultraviolet radiation. Therefore, the weather-resistant and waterproof base material in the fluorescent response flaw detection coating is replaced from acrylic emulsion to fluorocarbon resin emulsion, which has better overall performance. Fluorocarbon resin, due to the high-energy CF bonds in its molecular structure, possesses superior weather resistance, corrosion resistance, and self-cleaning properties, better protecting the pipe wall and extending the service life of the fluorescent coating. Simultaneously, to further improve the concealment and visual effect of the coating while ensuring detection sensitivity, the amount of fluorescent pigment is adjusted to 10-20 parts, and the coating thickness is controlled at 0.8mm-1.0mm to obtain a fuller fluorescent response.

[0091] In S3, the fire protection piping network of the substation was precisely calculated according to the calculation formula in Example 1. The total volume of the fire protection piping network was calculated. The longest branch is 12000L. The range is 300m. Considering the slightly different response characteristics of fluorocarbon coatings to tracers, a safety factor SF of 5 is chosen. Sodium fluorescein is selected as the tracer. (Visual inspection under UV lamp) Take 2 ppb. Substitute into the formula: =0.002mg / L × 5 × (1 + 0.2 × 300 / 100) × (12000L / 1L) = 192mg / L. The calculated dosage concentration is approximately 192mg / L, which is a mass ratio of approximately 1:5208, still within the recommended range of 1:5000 to 1:20000. After addition, circulate the mixture using the fire pump for 2 hours to ensure uniform mixing.

[0092] In S4, the maximum time for maintaining the design pressure value is 48 hours.

[0093] During the S5 inspection, a faint yellow-green fluorescence was found at a flange connection, the location of which matched the historical defect record. After taking photos and recording the information, it was confirmed as a leak point. Subsequent steps were the same as in Example 1.

[0094] Example 3:

[0095] This embodiment is basically the same as Embodiment 1, except that the detection process and judgment method have been refined.

[0096] When applying the fluorescent response flaw detection coating in S2, in addition to coating the easily leaking areas, fluorescent reference color blocks are also set at the starting point, ending point, branches, and every 50 meters of straight pipe section of the fire protection pipeline. These color blocks are coated with the same material as the easily leaking areas, but are smaller in area (e.g., 10cm × 10cm) and covered with a protective film to prevent direct contact with the external environment. Before and after the pressure holding test, these reference color blocks are photographed using the same UV lamp and image acquisition terminal to record their original fluorescence intensity and color. During the S5 inspection, the fluorescence signal of the leaking area is compared with the original signal of the reference color block. If the fluorescence intensity of the leaking area is significantly higher than (or the color is different from) that of the reference color block, it can be judged as a positive result. Introducing reference color blocks can effectively eliminate misjudgments caused by factors such as UV light intensity attenuation, changes in ambient light, and coating aging, making the test results more objective and accurate.

[0097] In the S5, the image acquisition terminal utilizes a drone equipped with a hyperspectral imaging camera for inspection. The drone automatically flies along a preset route, performing a comprehensive scan of the overhead fire hydrant network. The hyperspectral imaging camera can simultaneously acquire spectral and image information for each pixel. Because fluorescent tracers possess unique characteristic emission spectra, by processing and analyzing the acquired hyperspectral data, the software can automatically identify areas with tracer characteristic spectra and mark the precise locations of suspected leaks on the 3D model. This method significantly improves the efficiency and accuracy of inspections of large-area, complex pipe networks, especially high-altitude pipelines, achieving automation and intelligence in flaw detection.

[0098] Example 4:

[0099] This embodiment is basically the same as Embodiment 1, with the focus on the precise control of the S4 pressure holding step and the quantitative analysis after the S5 check.

[0100] In S4, a more precise automated control scheme is used to maintain the design pressure value. Specifically, after the fire pump starts, fills the pipes with water, and expels air, all outlet valves are closed. The inlet of the fire pipeline is connected to a small variable frequency booster pump. A high-precision pressure sensor (accuracy class 0.25) and an electrical contact pressure gauge are installed on the outlet pipe of the booster pump. The upper and lower limits of the pressure holding value are set on the control cabinet. For example, if the design pressure holding value is 1.2 MPa, the start pressure is set to 1.14 MPa (-5%), and the stop pressure is set to 1.26 MPa (+5%). During the 24-48 hour pressure holding period, if the pressure in the pipeline drops to 1.14 MPa due to minor leakage or temperature decrease, the pressure sensor transmits a signal to the controller, automatically starting the booster pump to replenish water and increase the pressure in the pipeline. When the pressure rises back to 1.26 MPa, the booster pump automatically stops. This process repeats, strictly controlling the pipeline pressure within ±5% of the design pressure holding value. Meanwhile, the data logger automatically records pressure data every 8 hours and generates a pressure-time curve. By analyzing the number of times the booster pump is started and the cumulative amount of water added each time, the total leakage can even be indirectly estimated. The pressure recording data will be part of the final test report, proving that the test process meets the specifications.

[0101] During the inspection of S5, in addition to visual inspection, a portable fiber optic fluorescence spectrometer was used to quantitatively analyze each suspected leak point. The inspector placed the fiber optic probe against the pipe wall coated with a fluorescent layer and pressed the measurement button. The spectrometer recorded the emission spectrum of that point under specific wavelength excitation. Since different fluorescent substances and concentrations have characteristic spectral shapes and peaks, comparison with the spectrum of the standard tracer solution prepared in S3 further confirmed whether the leaked substance was the tracer added, thus ruling out interference from other fluorescent substances. Simultaneously, based on the intensity of the fluorescence peaks, the severity of the leak could be semi-quantitatively assessed, providing a basis for prioritizing repairs.

[0102] In summary, this invention provides a fluorescent tracing-based flaw detection method for substation fire protection pipelines. Through a technical approach of "external coating, internal addition, long-term pressure holding, and precise detection," it transforms passively waiting for leaks into actively tracing and detecting them, effectively solving the challenges of traditional methods in detecting minute leaks. This method boasts advantages such as high detection sensitivity, accurate location, relatively simple operation, and quantifiable recording capabilities, making it significant for improving the fire safety level of substations and the entire power industry.

[0103] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0104] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A method for detecting flaws in substation fire protection pipelines based on fluorescence tracing, characterized in that, Includes the following steps: S1: Clean, remove rust, and dry the outer wall of the fire protection pipe network; S2: Apply a fluorescent response flaw detection coating evenly to the easily leaking areas on the outer wall of the fire protection pipeline and then cure it; S3: Add the fluorescent tracer to the fire-fighting water at the set concentration and mix thoroughly; S4: Start the fire pump and fill the fire pipeline with the detection medium containing fluorescent tracer that has been fully mixed in S3, and maintain the design pressure value for 24 to 48 hours; S5: After the pressure holding period is completed, the outer wall of the pipeline network shall be inspected by visible light inspection or ultraviolet light irradiation. S6: If an area with enhanced color development or abnormal fluorescence is found, it is identified as a suspected leak point and marked. Proceed to S7. If no enhanced color development or abnormal fluorescence is found, the fire protection pipeline network is not defective. Proceed to S9. S7: Discharge the test medium in the fire protection pipeline, flush with clean water 2-3 times, and repair the leak points marked in S6; S8: Return to S4 for re-inspection; S9: Complete the flaw detection work.

2. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The easily leaking areas in S2 include welded joints, flange connections, tee bends, and areas with historical defects.

3. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The fluorescent response flaw detection coating in S2 contains materials including weather-resistant and waterproof base material, fluorescent pigment, dispersant, film-forming aid, weather-resistant aid, and deionized water. All materials are mixed evenly in a certain proportion and then coated by brushing or spraying.

4. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 3, characterized in that, The coating thickness of the fluorescent response flaw detection coating is 0.5mm-1.2mm.

5. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The concentration of the fluorescent tracer in S3 is determined based on the fire duct network volume, branch length, and target detection sensitivity. The formula for calculating the concentration is as follows: ； in, To determine the final concentration of the tracer that needs to be added to the fire protection pipe network, This is the lowest detectable concentration of the instrument in an ideal water sample. For safety reasons, This is the physical length of the longest branch in the fire protection pipe network. For reference length, The length attenuation coefficient is... This is the total volume of the fire protection pipe network. The volume of water sample required for a single sampling or testing.

6. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The mass ratio of fluorescent tracer to fire-fighting water in the S3 addition concentration is 1:5000 to 1:20000.

7. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, In step S5, an image acquisition terminal can also be used to take pictures or record videos of the fluorescent area.

8. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The fluorescent tracer in S3 is a water-soluble fluorescent tracer, including one or more combinations of sodium fluorescein, rhodamine B, or acridine orange.

9. A method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The specific method for maintaining the design pressure value in S4 is as follows: after the fire pump is started to fill the pipe with water and purge the air inside the pipe, all outlet valves are closed, and the pressure inside the pipe is maintained within ±5% of the design pressure value by the pressure boosting pump. Pressure data is recorded every 8 hours during the pressure holding period.

10. The method for detecting flaws in substation fire protection pipelines based on fluorescence tracing according to claim 1, characterized in that, The ultraviolet light irradiation method in S5 uses an ultraviolet light wavelength of 365nm or 395nm, and the ambient light illuminance during irradiation is not higher than 50 lux.

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