As the core component of industrial boilers, boiler tubes are the key channel for heat transfer and medium transportation. During boiler operation, the heat generated by fuel combustion is transferred to the water or other media in the tube through the boiler tube, converting it into steam or hot water. However, over time, various substances will continue to accumulate on the inner and outer walls of the boiler tube, so cleaning is essential.
The cleanliness of boiler tubes directly affects many key links in industrial production. Keeping boiler tubes clean can significantly improve energy efficiency, reduce fuel waste, and reduce production costs; from a safety perspective, avoid accidents such as overheating and tube bursts caused by fouling and corrosion, and ensure the safety of personnel and equipment; at the regulatory level, comply with industry standards and safety regulations to avoid penalties due to violations; at the same time, good cleaning and maintenance can also extend the service life of the boiler and reduce equipment replacement costs. This article will discuss in depth how to efficiently clean industrial boiler tubes.
Scaling refers to various deposits formed on the surface of boiler tubes. Common types include soot, scale, ash accumulation and corrosion products. Soot is a mixture of carbon particles and other impurities produced by incomplete combustion of fuel; scale is mainly formed by the crystallization of calcium, magnesium and other ions in water at high temperature; ash accumulation is the ash produced during the combustion process attached to the tube wall; corrosion products are generated due to chemical reactions between the tube wall and the medium or environment.
The formation of scaling is related to many factors. Incomplete combustion, such as improper fuel-air ratio, will lead to a large amount of soot; impurities such as calcium, magnesium, and iron contained in water are very easy to form scale under high temperature and pressure; pollutants such as sulfur and nitrogen contained in the fuel will not only affect the combustion efficiency, but also aggravate the corrosion of the tube wall. In addition, unstable boiler operating parameters and improper water quality treatment will also accelerate the scaling process.
Scaling has a significant negative impact on industrial boilers. First, the deposits will form an insulating layer, hindering heat transfer and causing a significant drop in thermal efficiency. According to industry data, soot deposition can reduce the thermal efficiency of the boiler by 5% - 15%, and the presence of scale is more likely to reduce the thermal efficiency by 15% - 30%. Reduced thermal efficiency means that more fuel is needed to achieve the same production capacity, increasing operating costs. Secondly, scaling will increase the local temperature of the boiler tube, accelerate the corrosion and aging of the tube wall, increase the risk of failures such as tube bursts and leaks, and even cause explosion accidents in severe cases. In addition, frequent fault repairs will lead to extended equipment downtime, affecting production continuity and corporate economic benefits.
Before cleaning the boiler tube, the boiler must be shut down in strict accordance with the operating procedures. Turn off the fuel supply, stop the combustion process, and isolate the boiler after the pressure and temperature in the boiler drop to a safe range. Close all pipeline valves connected to the boiler to ensure that no medium flows in or out, and release the remaining pressure in the system to prevent accidents during the cleaning process.
Completely drain the residual medium inside the boiler and related pipes to avoid residual liquid from interfering with the cleaning work or causing safety hazards. At the same time, ensure that the cleaning area is well ventilated. Mechanical ventilation equipment can be used to promptly discharge harmful gases that may be generated during the cleaning process, such as acid and alkali gases volatilized during chemical cleaning, to ensure the health and safety of the operators.
Operators must wear appropriate personal protective equipment, including acid and alkali resistant gloves, goggles, dust masks or gas masks, etc. Choose the corresponding level of protective equipment according to the cleaning method and potential risks. For example, when performing chemical cleaning, chemical protective gloves and full-face gas masks are required to prevent acid and alkali solutions from splashing into the skin or inhaling harmful gases into the respiratory tract.
Strictly follow the maintenance manuals and operating guidelines provided by the boiler manufacturer, and comply with relevant industry standards and specifications such as OSHA and ASME. These standards and guidelines cover all aspects from cleaning processes to safe operations, and are an important basis for ensuring safe and efficient cleaning work.
Rotary tube cleaners
Rotary tube cleaners are driven by motors to make the brush head or scraper rotate at high speed inside the boiler tube, using mechanical friction to remove lighter deposits such as scale and ash on the tube wall. When selecting the brush head material, it is necessary to determine it according to the type of dirt and the material of the tube wall. Nylon brush heads are suitable for removing light dirt and have good protection for the tube wall; brass brush heads have moderate hardness and can be used to remove medium-hard scale; and steel brush heads are suitable for removing stubborn hard scale, but they must be used with extreme caution because they are very easy to damage the tube wall, even if the tube wall is thick, leaving scratches and accelerating corrosion. It is usually only considered for use under the supervision of experienced professionals with special alloy pipes, and non-metallic or soft metals such as brass brush heads are preferred.
Soot blower
Soot blower is a cleaning device installed inside the boiler. It can use steam or compressed air as power to spray high-speed airflow to the surface of the boiler tube through a nozzle to blow off the attached soot, ash, etc. Its biggest advantage is that it can be cleaned online during the operation of the boiler without stopping the machine, which reduces the impact on production. This method is widely used in coal-fired and oil-fired boilers, and can effectively keep the boiler tubes clean and maintain thermal efficiency.
Pipe cleaning technology
Pipe cleaning technology uses a tool called a "pipe cleaner" whose shape and size match the pipeline. It is pushed by the medium to run inside the pipe, scraping and removing dirt on the pipe wall. Pipe cleaning technology is suitable for straight and long pipes and can effectively remove various deposits from the pipe wall. However, this method also has certain limitations, such as it is not suitable for pipes with many bends or large changes in pipe diameter, and the pipe cleaner may be stuck during operation. It is necessary to evaluate the pipeline condition in advance and formulate countermeasures.
Pickling
Pickling is mainly used to remove mineral scale in boiler tubes, such as calcium carbonate, calcium sulfate, etc. Common pickling agents include hydrochloric acid, sulfuric acid, citric acid, etc. During the pickling process, corrosion inhibitors need to be added to inhibit the corrosion of the metal pipe wall by the acid, and the pH value and cleaning time of the solution are strictly controlled. After pickling, neutralization, rinsing and other subsequent treatments should be carried out in time to prevent residual acid from causing secondary corrosion to the tube wall.
Alkaline washing
Alkaline washing is mainly used to remove oil and grease and to pre-treat for pickling. Commonly used alkaline cleaning agents include sodium hydroxide and sodium carbonate. Alkaline washing can effectively dissolve grease dirt and remove some metal oxides. When performing alkaline washing, it is necessary to pay attention to controlling the concentration and temperature of the solution to avoid damage to the tube wall due to excessive concentration or improper temperature.
Chelation cleaning method
The chelating cleaning method uses chelating agents such as ethylenediaminetetraacetic acid (EDTA) to form stable complexes with metal ions such as iron, calcium, and magnesium to dissolve them from the tube wall. It is particularly suitable for treating iron-based deposits. This method is less corrosive to metal materials and is suitable for boiler tubes with more sensitive materials, but the cleaning cost is relatively high and requires professional equipment and operating skills.
High-pressure water jet cleaning
High-pressure water jet cleaning uses high-pressure water flow, usually tens to hundreds of MPa, to spray onto the surface of the boiler tube through a special nozzle, using the impact force of the water flow to break and flush out dirt. This method has the advantages of high cleaning efficiency, no chemical pollution, and no damage to the tube wall. However, during the operation, attention should be paid to the safety protection of the high-pressure water flow to avoid harm to personnel. At the same time, the water flow parameters should be reasonably controlled to prevent deformation of the tube wall due to excessive water flow pressure.
Ultrasonic cleaning
Ultrasonic cleaning is based on the principle of cavitation. When ultrasonic waves propagate in the cleaning liquid, a large number of tiny bubbles will be generated. These bubbles will quickly burst under the alternating action of high and low pressure, generating a strong impact force to peel off the dirt from the tube wall. This method does not require contact with the tube wall and is suitable for boiler tubes with complex structures that are difficult to clean by mechanical methods, and will not cause wear to the tube wall.
Dry ice cleaning
Dry ice cleaning is the process of spraying dry ice particles onto the surface of the pipe wall under the action of high-pressure airflow. Dry ice cleaning is the process of spraying dry ice particles onto the surface of the pipe wall under the action of high-pressure airflow. Dry ice particles sublimate at the moment of impact, absorbing a large amount of heat to cause local rapid cooling of the dirt, generating thermal stress to make it brittle or lose its viscosity. At the same time, the kinetic energy of the particles generates impact force, and the expansion of the high-pressure gas generated by sublimation further peels off the loose dirt. This method leaves no residue and does not damage the pipe wall. It is particularly suitable for sensitive systems with high cleanliness requirements, such as boilers in the food and pharmaceutical industries.
Explosive slag removal (only for large boilers)
Explosive slag removal is a professional cleaning technology for large boilers. By placing a small amount of explosives at a specific position inside the boiler, the shock wave generated by the explosion is used to shake off the stubborn slag attached to the pipe wall. This method requires professional operation and strict safety assessment and protective measures to ensure that the cleaning effect is achieved without affecting the safety of the boiler structure.
After the cleaning work is completed, the boiler tube needs to be fully inspected. Using an endoscope (such as a borescope) for internal observation can visually check the cleanliness of the pipe wall and whether there is any damage; using ultrasonic testing technology, it can detect changes in pipe wall thickness, evaluate the degree of corrosion, and promptly discover potential safety hazards.
Measure the corrosion rate of the pipe wall through professional instruments to determine whether the cleaning process causes excessive corrosion to the pipe wall. At the same time, detect the residual chemicals after cleaning to ensure that their concentration meets safety standards and avoid the adverse effects of residual substances on subsequent operations.
Record all data during the cleaning process in detail, including cleaning methods, cleaning agents used, cleaning time, inspection results, etc. These records are not only an important basis for corporate compliance operations, but also help to trace and analyze when equipment problems occur, while meeting insurance claims and other requirements.
During the operation of industrial boilers, contaminants such as scale and ash will gradually form on the surface of the boiler tubes. These attachments act as insulation layers, seriously hindering heat transfer and forcing the boiler to consume more fuel to achieve the expected heat output. Studies have shown that regular cleaning of boiler tubes can improve energy efficiency by 10% - 15%. Taking a medium-sized enterprise that consumes 10 tons of coal per day under ideal full-load conditions as an example, theoretical estimates show that through efficient cleaning management, about 365 - 547.5 tons of coal can be saved each year. The actual amount of savings depends on the actual operating load rate and operating time of the boiler. , significantly reducing the operating costs of the enterprise and greatly improving economic benefits. In addition, clean boiler tubes can make the heat exchange process more complete, reduce energy waste, and help enterprises achieve green and low-carbon development goals.
Boiler tube scaling and corrosion are one of the main causes of equipment failure. When the scale thickness reaches a certain level, it will cause local overheating, causing deformation or even rupture of the tube wall; while corrosion will weaken the strength of the pipeline and increase the risk of leakage. These failures are often sudden and lead to unplanned downtime. By establishing a scientific cleaning and maintenance mechanism, failures caused by scaling and corrosion can be effectively prevented. According to statistics, companies that insist on regular cleaning have an average reduction of 40% - 60% in the number of unplanned shutdowns, which greatly ensures production continuity. Stable equipment operation can not only improve equipment utilization, but also avoid order delays and customer loss caused by production stoppages, and maintain the company's good market reputation.
Overheating and pipe bursting are one of the most dangerous types of accidents in industrial boiler operation. When the boiler tube is covered with dirt, the heat cannot be dissipated in time, which will cause the tube wall temperature to rise sharply, and the pipe burst will occur when it exceeds the material's bearing limit. High-temperature and high-pressure steam and hot water are sprayed out instantly, which may cause serious burns to operators and even cause secondary disasters such as fire and explosion. Regular cleaning of boiler tubes can effectively reduce the risk of accidents such as overheating and pipe bursting. At the same time, during the cleaning and maintenance process, the boiler tubes can also be fully inspected to promptly discover and eliminate potential safety hazards, build a solid safety line for personnel and equipment, and maintain stable operation of the enterprise.
In order to ensure public safety and environmental protection, industry regulatory authorities have formulated strict inspection standards and specifications for boiler equipment, and usually require companies to conduct annual or semi-annual inspections. The cleanliness of boiler tubes is one of the important contents of the inspection. If the boiler tubes are found to be severely scaled or corroded beyond the standard, the company will face warnings, fines, or even be ordered to suspend production for rectification. Therefore, companies must attach importance to the cleaning and maintenance of boiler tubes, establish complete maintenance files, and ensure that the equipment is always in compliance. Through regular cleaning, not only can the inspection of regulatory authorities be successfully passed, but also the company's high attention to production safety and environmental protection can be demonstrated, and a good corporate social image can be established.
In the equipment insurance clauses, it is usually clearly stipulated that companies need to regularly maintain and maintain the equipment to reduce the probability of risk. As the core component of the boiler, the cleaning and maintenance status of the boiler tube is an important basis for the insurance company to assess claims. If the equipment is damaged due to failure to clean and maintain as required, the insurance company may refuse to pay on the grounds that the company has not fulfilled its maintenance responsibilities. On the contrary, maintaining good maintenance records and cleaning conditions will help meet the requirements of insurance clauses. Detailed cleaning and maintenance records, such as cleaning time, methods, inspection results, etc., can serve as strong evidence to ensure that the company can successfully obtain insurance compensation when equipment problems occur, reduce economic losses, and ensure the stability of the company's capital chain.
When choosing a cleaning method, multiple factors need to be considered comprehensively. The first is the type of dirt. Different dirt requires targeted cleaning methods; the second is the layout and structure of the boiler tube. The complex structure may limit the application of certain cleaning technologies; the type of boiler will also affect the choice of cleaning methods. For example, the dirt characteristics of coal-fired boilers and gas-fired boilers are different, and the cleaning focus and methods are also different. In addition, it is necessary to determine whether to use daily simple cleaning or periodic deep cleaning based on the frequency of cleaning needs; at the same time, weigh the advantages and disadvantages of manual cleaning and automated cleaning systems and make a choice based on the actual situation of the company. Regardless of the method used, having a professionally trained maintenance team is the key to ensuring cleaning results and equipment safety.
Boiler tube cleaning work is highly professional and dangerous, so it is recommended that it be operated by a qualified engineer or professional team. Professionals have received systematic training and are familiar with various cleaning techniques and safety regulations. They can formulate reasonable cleaning plans based on the actual situation of the boiler to ensure that the cleaning work is completed safely and efficiently. Personnel who carry out boiler tube cleaning work must have the corresponding professional qualifications and rich practical experience. In some small fire tube boiler systems, if the company's internal employees have received professional training and meet the safety operation requirements, they can perform daily cleaning and simple maintenance work under strict supervision. However, for large and complex boiler systems, and when special cleaning methods such as chemical cleaning and explosive slag removal are involved, must be performed by a professional team to ensure cleaning results and equipment safety.
There are many ways to clean industrial boiler tubes, each with its own applicable scenarios and advantages and disadvantages. From traditional mechanical cleaning and chemical cleaning to advanced high-pressure water jet cleaning, ultrasonic cleaning and other technologies, companies should make reasonable choices based on their own boiler characteristics and needs. Regular boiler tube cleaning can not only improve energy efficiency and reduce the risk of failure, but also ensure production safety and comply with regulatory requirements. It is recommended that companies pay attention to the cleaning and maintenance of boiler tubes, formulate scientific and reasonable maintenance plans, regularly evaluate the condition of boilers, and arrange professional cleaning in a timely manner to ensure the safe and efficient operation of industrial boilers.
