Abstract:
In response to the complex environment within coal storage silos, characterized by enclosed spaces and inadequate lighting, which poses challenges for traditional methods in detecting defects in wear-resistant lining plates, this paper adopts 3D laser scanning technology to inspect and evaluate the condition of wear-resistant lining plates inside a coal storage silo at Huanghua Port. By employing 3D laser scanning, a three-dimensional (3D) model of the silo’s internal structure is constructed. This paper introduces the point cloud data processing flow and data analysis methods. By combining 3D model cloud images and grayscale imagery, the identification and analysis of defects such as lining plate detachment and wear are achieved. The feasibility and effectiveness of 3D laser scanning technology in detecting defects in wear-resistant lining plates in coal storage silos are verified, providing a basis for the maintenance and repair of silos.
1. Introduction
China’s resource endowment is characterized by an abundance of coal, a scarcity of oil, and insufficient natural gas. Consequently, coal storage silos play a crucial role in energy storage and distribution. However, due to the enclosed nature and inadequate lighting within these silos, traditional inspection methods face significant challenges in accurately detecting defects in wear-resistant lining plates. This paper presents an innovative approach using 3D laser scanning technology to address these challenges.
2. Overview of 3D Laser Scanning Technology
2.1 Principle and Advantages
3D laser scanning technology operates by emitting laser beams to scan the target surface and collecting point cloud data through sensors. The collected data is processed to construct a precise 3D model of the scanned object. This technology offers numerous advantages:
- Safety: It avoids the safety risks associated with personnel entering coal silos, where toxic, flammable, and explosive gases may be present.
- High Precision: With high-speed acquisition and high-precision sensors, it provides millimeter-level measurement accuracy, enabling the timely detection of tiny cracks or deformations.
- Efficiency: Compared to manual inspection methods, 3D laser scanning can collect a vast amount of data in a short period, enhancing inspection efficiency and reducing production downtime caused by inspections.
- Comprehensiveness: It can scan the entire internal space of coal silos, including difficult-to-reach areas such as the top and sidewalls, ensuring no issues are overlooked.
2.2 Technical Parameters
Table 1 presents the technical parameters of the 3D laser scanner used in this study.
| Item | Technical Parameters | Specifications |
|---|---|---|
| Laser Class | Class 1 | – |
| Beam Divergence Angle | <0.3 mrad | – |
| Beam Diameter | 3.5 mm (at 0.1 m) | – |
| Maximum Range | 187.3 m | – |
| Minimum Range | 0.3 m | – |
| Resolution | 0.1 mm | – |
| Measurement Rate | 1,016,000 points/s | – |
| Linear Error | ≤1 mm | – |
| Laser System | Distance Noise: 0.3 mm rms; Fully Enclosed Vertical System with Rotating Mirror; 320° Field of View; Resolution: 0.0004°; Accuracy: 0.007° mms | – |
| Deflection Unit | Horizontal System Rotates Around Vertical Axis; 360° Field of View; Resolution: 0.0002°; Accuracy: 0.007° mms | – |
| Focus Range | 1 m to ∞ | – |
| Panoramic Image Quantity | 42 | – |
| HDR Camera | Recording Time: Approximately 3:30 m (depending on environmental lighting) | – |
3. Application in Wear-resistant Lining Plate Inspection
3.1 Project Background
The coal storage silo at Huanghua Port, with a diameter of 40 m and a height of 43 m, utilizes pressed microcrystalline plates as wear-resistant lining plates, adhered to the concrete wall using microcrystalline mortar. During normal use, partial detachment of these plates occurs. This study employs 3D laser scanning technology to inspect and assess defects such as detachment areas, detachment sizes, and structural damage levels, providing data support for subsequent repair plans.
3.2 Data Collection and Processing
The 3D laser scanning process involves scanning the entire internal space of the silo, collecting point cloud data, and constructing a 3D model of the silo’s internal structure. Subsequently, professional software is used to process the point cloud data, generate 3D models, and analyze grayscale imagery to comprehensively determine the types of defects in the wear-resistant lining plates.
3.3 Defect Analysis
For ease of statistical explanation, the coal storage silo is divided into the northern and southern compartments along the axis of the central dividing beam. The covered areas of the pressed microcrystalline plates are categorized into four main regions: silo sidewall, support decompression surface, funnel area, and central dividing beam surface. The funnel area is further subdivided into N1, N2, N3, S1, S2, and S3 zones.
Due to the enclosed and lightless interior of the coal storage silo, the collection of color and texture information is impossible. Therefore, texture mapping cannot be performed on the 3D model constructed from point cloud data. Instead, comprehensive judgment on the types and distribution of defects in the wear-resistant lining plates is made by combining the different information features presented in grayscale imagery and 3D model cloud images. Known defects in coal storage silo wear-resistant lining plates mostly include lining plate detachment, coal accumulation, liquid accumulation, and structural damage, which exhibit the following characteristics:
- Pressed Microcrystalline Plate Characteristics: In grayscale imagery, the plates are regularly distributed like tiles. In 3D cloud images, the plates form a continuous curved surface without significant concave-convex features. The plates exhibit the highest diffuse reflection, with the thickest and most abundant point cloud data.
- Coal Accumulation Characteristics: Laser beams have low reflectivity against black coal, and carbon elements, with a regular hexagonal structure, tend to exhibit specular reflection rather than diffuse reflection. Coal appears black in grayscale imagery, with coal accumulations distributed in heaps. In 3D cloud images, coal accumulations appear as irregularly shaped protrusions with less corresponding 3D point cloud data due to their difficulty in diffuse reflection.
3.4 Verification of Results
After 3D laser scanning, explosion-proof lights were placed inside the silo, and cameras were used to take photos of标志性 positions where detachment occurred. These photos were used to verify the modeling and statistical analysis data. A comparison between the 3D model images generated using 3D laser scanning technology and the photos taken using a DSLR camera. The defect defects are consistent, verifying that the use of 3D laser scanning technology for detecting the detachment locations and areas of pressed microcrystalline plates in coal storage silos is a safe, efficient, and reliable technique.
4. Discussion
The successful application of 3D laser scanning technology in the inspection of wear-resistant lining plate defects in the coal storage silo at Huanghua Port demonstrates the technology’s significant potential in enhancing inspection safety, accuracy, and efficiency. Through automated data collection and high-precision measurement, it enables the generation of 3D models and grayscale imagery of the internal space of coal storage silos, allowing for the timely detection and assessment of defects such as lining plate detachment and wear.
Research results indicate that 3D laser scanning technology not only reduces the risks and costs associated with manual inspections but also provides comprehensive, multidimensional visual data, aiding in better maintaining the structural safety of coal storage silos and providing accurate data support for subsequent repair plans, thereby ensuring the long-term stable operation of coal storage silos. As the technology further develops and improves, 3D laser scanning technology is expected to find wider application in the field of structural inspection and assessment.
5. Conclusion
The successful practical application of 3D laser scanning technology in the inspection of wear-resistant lining plate defects in the coal storage silo at Huanghua Port highlights the technology’s tremendous potential in enhancing inspection safety, accuracy, and efficiency. By automating data collection and leveraging high-precision measurement, it is capable of generating 3D models and grayscale imagery of the internal space of coal storage silos, enabling the timely detection and evaluation of defects such as lining plate detachment and wear.