Advancements in Pipe Robot Technology for Power Plant Boiler Header Inspection and Cleaning

Power stations are critical facilities responsible for supplying electricity to meet the needs of both daily life and industry. Within power station engineering, the role of pipelines is paramount. However, due to the intricate internal management of these pipelines, it is often challenging for regular staff to visually assess their operational conditions. As a result, the testing and cleaning of pipelines have become persistent challenges in the industrial landscape. To ensure that pipelines remain in normal and stable working condition, the development of a service intelligent tool was essential, leading to the creation of pipeline cleaning robots. These robots are designed to adapt to the complex internal structures of pipelines, perform intelligent movement, conduct internal cleaning, and carry out essential state detection, effectively addressing the challenges posed by pipeline maintenance and safeguarding the quality of pipeline facilities.

1 Power Station Boiler Header

1.1 Challenges in Power Station Boiler Header Maintenance

The maintenance of heating furnace internal structures in power stations is a task that demands stringent cleaning requirements. The short heating time of boilers, combined with various factors such as the quality of pipe fittings and over-parameter operation, often leads to burst pipes. The primary cause of these bursts is the accumulation of machining and manufacturing residues in the throttle holes of the collection box or the heating surface tubes. This accumulation results in rapid surface overheating, eventually leading to burst pipes. Burst pipe incidents not only disrupt the normal start and stop of wind power generation equipment but also pose significant safety hazards, resulting in substantial losses for the power station.

Currently, traditional methods are still prevalent for checking the cleanliness of collection boxes. Before installation, workers carry out acid washing and pipe blowing, followed by manual speculum inspections. In this process, an endoscope probe line is manually inserted into the header, and foreign materials are identified and removed using hand-controlled methods. However, these traditional techniques come with limitations such as restricted inspection distances, low efficiency, time-consuming procedures, and labor-intensive efforts. They may also lead to leakage and inspection blind spots due to factors like unwelded receiver seat angle weld roots and incomplete melting combinations, hindering accurate measurements.

For container inspection, the changing aperture size and inconsistent diameters present a challenge, requiring pipeline automation robots to adapt to varying diameters. Additionally, given the small internal space of containers, the presence of metal weld seams, receiver seat openings, and machining residues, a pipeline robot must be compact and possess excellent obstacle-crossing capabilities. Conventional wheeled pipeline robots struggle to achieve this level of agility, and even tracked pipeline robots face difficulties in meeting size and performance requirements for cleaning tests.

1.2 Main Cleaning Methods for Power Station Boilers

Presently, one of the primary methods for cleaning hot coal furnaces in power stations involves manual labor. Workers enter the furnace chamber to clean dirt and ash and remove hot coal residue. This cleaning method is relatively simple and practical; however, its effectiveness is limited, making it a time-consuming and labor-intensive process. Moreover, during ash cleaning, dust and debris can pose health risks to workers, leading to occupational diseases and environmental pollution. To address these challenges, the development of small intelligent robots suitable for inspecting and cleaning boiler high-temperature header tanks is an urgent need. These robots can provide efficient and effective solutions to the complexities associated with maintaining power station boiler headers.

2 Introduction to Pipeline Robot Technology

2.1 Versatility of Pipeline Robots

Pipeline robots represent the fusion of traditional mechanical engineering and modern electronic technology. This innovation results from the convergence of disciplines such as computer science, control science, and mechanics, profoundly impacting both industrialized production and scientific research. These robots have gained popularity for their ability to replace manual labor in challenging work environments, freeing workers from extreme conditions, and simultaneously enhancing work efficiency and quality.

Industrial production robots have been widely adopted in various sectors, including the automotive and metallurgical industries. On the other hand, service robots are designed to perform tasks such as cleaning, transportation, monitoring, regular inspections, and testing, offering valuable services to people. Service robots often need to adapt to changing environments and time constraints, requiring a high degree of coordination to achieve their operational objectives.

In the contemporary era, numerous industries and experts have dedicated significant efforts to researching service robots. Cleaning, in particular, stands out as one of the most prominent applications of service robots. In the current age of high automation control, continuous improvement and advancement of pipeline cleaning robot technology have become increasingly significant.

2.2 Advantages of Pipeline Robots

One of the most critical tasks in power station boiler header inspection and maintenance is addressing the following key areas:

• Removal of accumulated dust on the surface of the water-cooled wall.
• Elimination of slag scale on the fire side of the water-cooled wall pipe surface.
• Inspection for damage, corrosion, and softening of the pipe wall, including alterations in the pipe wall’s shape.

Traditional manual methods suffer from several shortcomings, including long operating cycles, low efficiency, high costs, and a propensity for safety accidents. These methods not only fail to guarantee the quality of cleaning and testing but also fall short of meeting the evolving needs of society.

In 1997, the Harbin Institute of Technology Robotics Research Laboratory, in collaboration with Tianli Robotics Engineering Co., Ltd., developed a suitable robot for power station boiler inspection and cleaning. This robot is equipped with functions such as slag removal, thickness measurement, and laser marking. It utilizes crawler mobility to traverse the tube wall for descaling and cleaning. The robot’s design incorporates an effective adsorption and motion function module, enabling it to move along the pipe wall and securely attach itself for optimal cleaning performance.

3 Pipeline Robot Technology Analysis

In the context of pipeline robots, it is crucial to consider the pipeline environment and related technical standards, with a specific focus on communication stability and power supply. The choice of power supply for pipeline robots plays a significant role in ensuring the robot’s motion control system and pipeline cleaning safety. An ideal power source for pipeline robots is built-in lithium batteries, which offer the necessary energy to support the robot’s normal operations.

Pipeline robots are capable of executing movement, detection, and cleaning tasks within pipelines due to their advanced structural design. These robots integrate a range of components, including mobile devices, steering devices, mechanical operating arms, cleaning devices, unloading devices, detection devices, and control systems. Among these components, the primary devices that influence the working performance and technical parameters of pipeline robots include the design of the moving device, steering device, cleaning device, unloading device, and mechanical operation arm.

3.1 Types of Robot Movement

1. Peristaltic Mobile Type: Peristaltic mobile pipeline robots draw inspiration from the locomotion of peristaltic walking animals. They are typically simulated in two forms: (1) using a metal structure with the ability to mimic peristaltic walking for robot propulsion, and (2) employing pneumatic systems to simulate peristaltic walking for robot locomotion.
2. Tracked Mobile Type: Tracked mobile robots are designed with reference to tracked vehicles like heavy tanks and excavators. In the realm of robotics, two common forms are bipedal and tripedal tracked walking robots. Tripedal robots often possess more robust driving capabilities compared to bipedal ones, albeit with slightly reduced maneuverability.
3. Roller Mobile: Roller mobile robots draw inspiration from automobile driving and walking. They are typically electrically driven, but due to their small wheel diameter, they have limited mobility and traction capabilities.
4. Legged Mobile Type: Legged mobile robots are designed to emulate human and animal walking on legs. These robots typically feature two or more legs, enabling flexible movement in various complex environments, making them well-suited for pipeline exploration. However, this complexity also comes with intricate operation modes.
5. Piston Rod Mobile Type: The working principle of piston rod mobile robots resembles the movement of an automobile engine’s crankshaft in a cylinder. In this scenario, the pipeline represents the engine cylinder, and the pipeline robot serves as the piston rod. During movement, the two ends of the pipeline robot are isolated, creating a pressure difference that enables locomotion. Additionally, these robots incorporate various sensors for information acquisition, enhancing their capabilities.

The choice of movement type depends on the specific requirements of the pipeline inspection and cleaning tasks, as well as the environmental conditions in which the robot will operate. Each movement type offers distinct advantages and may be suited for different applications within the pipeline.

3.2 Adsorption Mechanisms

Intelligent robots commonly utilize various adsorption methods, including vacuum pump adsorption, magnetic adsorption, and thrust adsorption, each with its own set of advantages and disadvantages:

1. Vacuum Pump Adsorption: This method offers a robust adsorption force but is susceptible to issues when the wall surface finish is inadequate or when cracks are present, which can lead to leakage and reduced adhesion.
2. Magnetic Adsorption: Hydro-magnetic adsorption doesn’t require additional kinetic energy, and it provides a high level of safety. However, it relies on a larger thrust when separating the magnet body from the wall.
3. Electromagnetic Induction Adsorption: This method enables efficient clutching between the magnet body and the wall, even during high-speed movement. However, it requires the continuous use of electromagnetic energy to maintain adhesion, and the electromagnetic body itself can be quite heavy.
4. Thrust Adsorption: This approach does not suffer from leakage issues and exhibits strong adaptability to the wall’s surface. However, it is associated with noisy operation, structural complexity, and relatively lower efficiency.

The choice of adsorption method depends on the specific application, environmental conditions, and the required level of adhesion and safety.

3.3 Moving Mechanisms

The mobility of pipeline robots is crucial for their effectiveness, and different moving mechanisms are employed to navigate within pipelines:

1. Frame-Type: Frame-type robots excel in two-dimensional multi-directional movement and exhibit strong obstacle-crossing capabilities. They can adapt well to complex wall surfaces.
2. Wheel-Type: Wheel-type robots can overcome high obstacles, often utilizing passive suspension mechanisms or multi-section wheels for enhanced freedom of movement. However, they have limited sliding friction capacity and may experience alignment issues or detachment.
3. Foot-Type: Foot-type robots have strong collaborative functions and can cope with complex wall surfaces. However, they present challenges in terms of movement, and their mechanical intelligence requirements are high, resulting in complex motions.
4. Crawler-Type: Crawler automated robots have the ability to traverse obstacles, including platforms and fences. They possess strong surface sliding friction. However, they consume significant energy, and checking the roll generated by the crawler walking mechanism can be inconvenient and challenging, leading to difficulties in accurate measurements. They are also relatively bulky.

The choice of the moving mechanism depends on the specific requirements of the pipeline inspection and cleaning task, including the nature of the pipeline’s interior, the required precision, and the environmental conditions. Building wall moving robots need to adapt to the diverse surfaces and complex structural environments typically found in construction settings, and the selection of the right moving mechanism is essential for their successful productization.

3.4 Power and Drive Mechanisms

Pipeline robots employ various drive methods, primarily falling into four categories: automatic control principles, hydraulic drive systems, electromechanical transmission control, and gear drive. Presently, the most common drive methods involve electrical and pneumatic technologies. Electrical drive systems are preferred for their precise control capabilities, allowing for orientation and power control. For example, when navigating inside a spiral steel pipe, automation control along a parallel line can enable comprehensive cleaning of the entire interior. To achieve linear motion, low voltage DC brushless motors with excellent control characteristics are chosen as the prime mover for the robot’s operation. The power supply is regulated by a dedicated driver, and by adjusting the current and controlling the drive mechanism, the speed ratio between the motor and the input shaft can be fine-tuned, completing the motion control system of the robot.

3.5 Pipeline Robot Operating Arm

The operating arm mechanism of a pipeline robot is designed to perform cleaning, loading, and unloading functions to facilitate effective pipeline maintenance. Considering the specific working conditions within power station boiler header pipes, a 3-degree-of-freedom mechanical operating arm is an ideal choice. The arm can be equipped with a vacuum cleaner head at the end and a dust-absorbing hose running along its length. To ensure that the mechanical arm seamlessly fits the pipeline environment, it should have a well-designed attitude joint structure and be driven by a suitable drive motor. Additionally, to maintain the robot’s lightweight and agility, the rods of the mechanical operating arm should be carefully selected for optimal functionality while keeping the overall weight in check. This ensures that the robot operates effectively in its intended environment.

3.6 Pipeline Inspection Organization

The pipeline inspection center comprises essential components such as a control board, crawler, monitoring camera, and more. During operation, the control board is used to manipulate the crawler, guiding it to carry inspection instruments into the pipeline for a thorough examination. In the inspection process, the pipeline intelligent robot promptly transmits video footage of the pipeline’s internal structure to the maintenance center. This enables maintenance personnel to analyze common issues within the pipeline’s internal structure. The system software leverages deep learning technology to provide algorithmic insights based on image features. Vision cameras are employed to observe real-time video recordings of the inspection area. Through artificial intelligence technology and the use of multiple scanners, the system can perform deep learning of the test area, extract the relevant primary parameters, and accomplish three-dimensional reconstruction of the pipeline. Remote control is used to manipulate the robot during the inspection process.

3.7 Pipe Cleaning Mechanism

Pipeline cleaning is achieved within the pipeline cleaning robot through the internal fan of the robot’s box. This process fully utilizes aerodynamic principles. When the robot’s internal fan rotates at high speed, it creates negative pressure within the robot’s box, effectively generating a relative vacuum environment. In this vacuum, debris is drawn into the system. The inhaled debris typically includes metal dust, which is channeled through the robot’s dust hose into the robot’s dust collection box. As air circulates within the robot’s internal space, the hose’s interior volume increases. Due to gravity, metal dust freely descends to the bottom of the dust collection box, awaiting removal once the robot completes its operation. This cleaning mechanism efficiently manages and collects debris from within the pipeline.

4 Conclusion

In summary, regular testing and cleaning of boiler header piping equipment within power stations are crucial to ensure the performance and safety of these critical components. This paper has provided a concise overview of dedicated robot technology for pipeline inspection, demonstrating its potential to significantly reduce the workload of human operators. When properly applied, this technology can greatly enhance the safety and reliability of inspection and cleaning tasks within complex boiler pipeline environments. It is anticipated that the adoption of pipeline robotics will continue to grow in the future, benefiting various industries.

The analysis of pipeline robotics technology presented in this paper is intended to offer valuable theoretical support to the inspection industry, as well as contribute to the advancement of power station boiler equipment and the broader development of the robot industry.

[Source]Wang Feng, Wang Yanming, Liu Ruiping, Dong Guangshan, Research on Pipe Robot Technology for Detection and Cleaning of Power Plant Boiler header