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Nine common device problems and solutions for ball cleaning of condensers Abstract: The ball cleaning device is widely used in thermal power plant turbine-generator sets to clean the fouling inside the heat exchange tubes of condensers during operation; the performance of this cleaning device directly affects the degree of cleanliness of the condensers as well as their heat transfer efficiency. However, the rubber ball cleaning technique suffers from various issues such as poor suitability of the equipment used, uneven distribution of the rubber balls, low recovery rates, balls escaping or getting stuck and thus blocking the heat exchange tubes, high water resistance in the secondary filters, as well as uneven cleaning and insufficient cleaning effectiveness. Only by upgrading it with an online chemical cleaning method that allows operation to continue can the cleanliness factor of the condenser be ensured, thereby completely resolving common problems such as a decrease in the condenser’s vacuum level, an increase in exhaust temperature, and an increase in the terminal difference. Keywords: condenser ball cleaning ； Condenser ball cleaning issue ； Online chemical cleaning of condensers ； Low condenser vacuum ； High condenser exhaust temperature ； Large condenser terminal difference ； Energy conservation and emission reduction technologies. I. Condenser rubber ball cleaning device: The rubber ball cleaning device is a system widely used in thermal power plant turbine-generator sets to clean the dirt accumulated inside the heat exchange tubes of the condenser during operation. The performance of this cleaning device directly affects the degree of cleanliness of the condenser as well as its heat transfer efficiency. The rubber ball cleaning device consists of an electrical control cabinet, pipelines, valves, distributors, rubber ball pumps, a ball loading chamber, a ball collection net, and rubber balls. There are various types of rubber balls used for cleaning, including ordinary rubber balls, peeled rubber balls, and silicone rubber balls. The gel ball cleaning device keeps the condenser cooling tubes (copper tubes, stainless steel tubes, or titanium tubes) clean at all times, which extends the service life of these heat exchange tubes and enables automatic control to reduce labor intensity ； It is an essential device for ensuring the safe operation of the condenser and improving the economic efficiency of the power plant. II. 12 Common Problems with the Equipment Used in the Condenser Ball Cleaning Technology System. Common problem 1: Structural defects in the mesh plates of the ball collection net. The ball collection net in the condenser ball cleaning system features a folding-type mesh plate design; it performs well at the beginning of operation, but over time it tends to undergo elastic deformation, and the gaps between the mesh plates can lead to balls escaping or falling through. Common problems with the equipment used for cleaning condenser rubber balls No. 2: Design flaws in the ball extraction port of the collection net. The design flaws in the location of the ball extraction port on the collection net of the condenser rubber ball cleaning device make it easy for balls to get stuck; once blocked, a large number of rubber balls accumulate on the collection net. The ball collection time is long, the collection efficiency decreases, and debris such as filler tends to accumulate on the ball collection net. Common problems with equipment related to the gel ball cleaning technology for condensers: Issue 3 – Lack of a secondary filter in the system. The absence of a secondary filter for protection in the gel ball cleaning system for condensers allows fillers and other debris to enter the water chamber, blocking the heat exchange tubes and deteriorating the operating conditions of the gel ball system. Common problems with equipment related to the gel ball cleaning technology for condensers: 4. Quality defects in gel balls. The ordinary foam-based sponge gel balls, peeled rubber gel balls, silicone gel balls, etc., that are currently widely used in condenser gel ball cleaning systems vary in quality. In some cases, the size of these gel balls increases significantly after soaking and swelling, exceeding the design specifications; as a result, they cannot pass through the heat exchange tubes properly, leading to blockages ； Some rubber balls, after soaking and swelling, become much smaller than the size specified in the design, which renders cleaning of these rubber balls practically ineffective. On-site tests also showed that most of the new gel balls are 1–2 mm smaller in diameter than that of the heat exchange tubes, indicating certain issues with the quality and design selection of the existing gel balls. If the density of the rubber balls is lower than that of the circulating water, they remain floating during the cleaning process, failing to clean the heat exchange tubes in the condenser evenly; as a result, there are many areas that are not cleaned, leading to low cleaning efficiency. ▲Common problems with the equipment used for online rubber ball cleaning of condensers in thermal power plants: low recovery rate of rubber balls, issues related to ball loss, and a low cleaning efficiency. Problem 5: Low recovery rate of rubber balls. The reasons for this low recovery rate include low pressure of the circulating cooling water and low flow rate of this water; as a result, there is not enough pressure for the rubber balls to pass through the heat exchange tubes. Additionally, if the diameter of the cooling water pipes becomes smaller due to scaling, or if the rubber balls expand in diameter due to absorption of water, these factors also contribute to the problem. If the resistance is high, the rubber ball will get stuck in the tube ； The design of the actuator for the ball-catching net is unreasonable; the axis of the net is driven by an electric device, and the positioning adjustments of the actuator are inadequate, which prevents the net from closing properly. As a result, a large gap forms between the housing and the inner wall, leading to balls escaping or leaking through ； The gaps in the mesh panels of the ball collection net are uneven, causing the net to become contaminated and leading to balls getting stuck or trapped ； When the collection net becomes dirty and clogged, causing the pressure difference to rise and reach the set limit, some of the rubber balls will be lost during the backwashing of the collection net ； The flow field distribution in the condenser water chamber contains dead zones and vortices, which lead to the accumulation of rubber balls in the water chamber. Failure to remove these balls in a timely manner results in a low recovery rate of rubber balls by the condenser’s rubber ball cleaning device. Common problems with the equipment used for ball cleaning of condensers, issue 6: Control issues of the device. The ball cleaning systems used for the online cleaning of condensers in current thermal power plant turbine-generator sets are, in most cases, operated entirely manually. Tasks such as switching the receiving chamber valves, controlling the operation of the receiving nets, changing valves, feeding balls, counting balls, and replacing rubber balls are all carried out manually, which results in high labor intensity and complex operations. Moreover, this approach hinders the continuous operation of the rubber ball system, and the cleaning efficiency of this system cannot be ensured. Common issue 7 regarding the equipment used for cleaning condenser balls: excessive power of the ball pump. Typically, most thermal power plant operators do not give proper consideration to the selection of ball pumps that are suitable for their needs. In plants where the cooling area of the condenser is small, ball pumps with excessive power are often used. This not only leads to unnecessary waste but also causes high-speed water flow generated by these pumps to disrupt the circulation of water in the condenser, resulting in an increase in the temperature of the water at the condenser inlet. This, in turn, reduces the vacuum level of the condenser. This is why the ball pump systems in many thermal power plants are not utilized effectively, or even avoided altogether. Common issue 8 regarding the equipment used for cleaning condenser balls: short service life of the balls. The balls used in condenser ball cleaning systems generally have a short service life. To reduce costs, power plant operators do not replace these balls or add additional ones once their wear exceeds the specified limit, which results in a decline in the effectiveness of the cleaning process. To ensure proper operation, it is necessary to check the rubber balls once a month, and replace them every six months as needed; this also increases operating costs and workload. Common problems with the gel ball cleaning technique for condensers: 9. The cleaning effect is not significant, and the cleaning efficiency is low. The gel ball cleaning system performs poorly – the gel balls are not distributed evenly, the recovery rate is low, there is leakage of gel balls, and these balls can block the heat exchange tubes as well as the secondary filters. Additionally, there is high water resistance, resulting in uneven cleaning. Gel ball cleaning is effective against algae, biological sludge, and soft deposits, but its effect on hard deposits in condensers is limited. To maintain an adequate cleaning efficiency for the condenser, it is necessary to combine this method with online chemical cleaning while the unit is still running. ▲ Comparison before and after online chemical cleaning of the heat exchange tubes in the condenser of steam turbine generators in thermal power plants. III. Upgrade of the gel ball cleaning technology for condensers – Online chemical cleaning without shutting down the plant. The gel ball cleaning technology for condensers has certain drawbacks in various aspects; whereas the online chemical cleaning technique developed on the basis of the traditional shutdown-based cleaning method avoids the need to shut down the plant for cleaning, thus preventing losses in power generation efficiency ； Cleaning processes that take a long time, and require manual operation, monitoring, and maintenance ； The disadvantages of high cost investment and significant losses in power generation efficiency can be overcome by achieving thorough cleaning with a high cleaning efficiency in terms of operation, safety, and economic performance, while making as few modifications as possible to the existing equipment. Online chemical cleaning of condenser fouling without shutting down the plant is a cleaning technology that has evolved from the traditional method of chemical cleaning carried out while the plant is shut down. Online chemical cleaning of the condenser can be carried out without shutting down the plant; it takes a short amount of time and does not require any downtime, thereby reducing losses resulting from power generation interruptions. The HS-186 multi-functional agent, which includes properties for sterilization, removal of sludge, cleaning of scale, and metal passivation, is used in this process. This results in low cleaning costs and short processing times. Online cleaning can be conducted for around 10 hours, during which moss and other microorganisms, as well as dust, are removed. Meanwhile, scale within the tubes is cleared, and corrosion of metal components is prevented ； Online chemical cleaning of the condenser for removing scaling can be carried out at any time, without the need to wait for major or minor maintenance of the unit. This approach not only reduces significantly the consumption of chemicals and wastewater, but also prevents corrosion inside the condenser, making it a safe, environmentally friendly, and efficient solution. Online chemical cleaning of the condenser can be carried out without shutting down the unit, thereby ensuring an optimal cleanliness level. After the cleaning is completed, the key performance indicators of the condenser reach the following values: A. Vacuum level increases by ≥1.0–2.0 kPa; B. Temperature difference decreases by ≤3.0 degrees Celsius; C. Exhaust gas temperature decreases by ≤2.0°C; D. Power generation increases by ≥2% under the same air supply conditions as before. Colleagues and friends, in addition to these eight conventional condenser cleaning methods—chemical cleaning, high-pressure water cleaning, projectile cleaning, online gel ball cleaning, online ultrasonic cleaning, online robotic cleaning, online spiral thread cleaning, and again chemical cleaning—what other condenser cleaning techniques are you aware of? Which condenser cleaning technology do you think offers the best overall performance at present? Regarding issues such as corrosion and scaling in condensers, online cleaning and descaling techniques that allow operations to continue without shutdown, as well as online descaling techniques for boiler scaling without interrupting operations, Yan Hui from Beijing University of Chemical Technology at I86OO475З86 is always available to discuss these issues and exchange experiences and insights. Students are also welcome to communicate about new technologies related to condenser cleaning. Nine common device-related problems in condenser ball cleaning and their solutions ▲Comparison of the advantages and disadvantages of 8 common techniques for online condenser cleaning and cleaning when the condenser is shut down. IV. Technical upgrades to condenser ball cleaning devices: Cases of using online chemical cleaning to address issues such as increased terminal temperature difference, rising exhaust temperature, and decreased vacuum level. Operational conditions of the condenser in the Xuzhou Tongshan biomass cogeneration project before performing online chemical cleaning without shutting down the plant. The Xuzhou Tongshan biomass cogeneration project features a 35MW high-temperature, ultra-high pressure reheated steam turbine generator set, along with a 130t/h high-temperature, ultra-high pressure reheated circulating fluidized bed biomass boiler. This project uses agricultural straws and forestry waste as primary raw materials; it processes over 600,000 tons of straws per year and generates around 300 million kWh of electricity annually. It provides enterprises in the equipment manufacturing industrial park with combined supply of cooling, heating, electricity, and compressed air. The rubber ball cleaning device used for the online cleaning of the condenser in the steam turbine generator set of the Xuzhou Tongshan biomass cogeneration project does not yield significant cleaning results, resulting in a low cleaning efficiency. The control panel of the steam turbine generator set indicates a low vacuum level in the condenser, a large temperature difference at the condenser, and a high exhaust temperature from the condenser. ▲The low cleaning efficiency of the online rubber ball cleaning system in the condenser of the thermal power plant results in a low vacuum level in the condenser, as well as a larger temperature difference at the condenser outlet. At 2:58 p.m. on April 14, 2023, in the control room of the biomass cogeneration plant in Tongshan, Xuzhou, a screenshot showing the condition of the condenser before online cleaning was displayed on the control panel, as shown in the image above. The boiler’s gas supply rate is 114.5 t/h, the vacuum level is -87.4 kPa, the exhaust steam temperature is 51.6°C, and the terminal difference is 17.1 degrees Celsius. The power generation capacity is 30.69 MW/H. Scaling on the condenser clearly leads to a low vacuum level in the condenser as well as a large terminal difference; this reduces the thermal efficiency of the turbine unit, increases the standard coal consumption for power generation, and results in a significant decrease in power output. ▲Operation status of the condenser in the steam turbine generator set at the control room of a thermal power plant after online partial chemical cleaning without shutting down; operation status of the condenser with scaling, also without shutdown, following online partial chemical cleaning. At 5:01 a.m. on April 23, 2023, in the control room of the biomass cogeneration project’s thermal power plant in Tongshan, Xuzhou, a screenshot was taken of the condition of one half of the condenser after approximately 5 hours of online chemical cleaning without any shutdown, as shown in the image above. The boiler’s steam supply rate is 118 t/h; the vacuum level increased to -96.0 kPa, while the exhaust steam temperature dropped to 36.2°C. The terminal difference decreased from 17.1 degrees Celsius to 6.5 degrees Celsius, returning to normal levels. The power generation capacity increased to 33.71 MW/H, with a net increase of 3.020 MW per hour – representing a 10% increase in power generation. This results in an additional About 72,000 kWh of electricity generated per day. At a cost of 0.7 yuan per kWh for biomass-based power generation, this translates to an additional profit of about 50,000 yuan per day. All operating parameters of the condenser have returned to normal. ▲Operation status of the condenser in the turbine unit’s control room of a thermal power plant after full chemical cleaning on both sides without shutting down; operation status of the condenser with scaling present but still without shutdown, following full chemical cleaning on both sides without interruption. At 4:21 a.m. on April 24, 2003, in the control room of the biomass cogeneration power plant in Tongshan, Xuzhou, a screenshot was taken of the condition of the other half of the condenser after approximately 5 hours of chemical cleaning carried out online without shutting down, as shown in the image above. The boiler’s steam supply rate is 115.4 t/h; the vacuum level increased to -97.6 kPa, the exhaust steam temperature dropped to 31.8°C, and the terminal temperature difference decreased to 3.7 degrees Celsius. It became necessary to stop one of the circulation pumps, as otherwise overcooling would also affect power generation efficiency. As a result, the power generation capacity increased only to 32.75 MW per hour. V. Conclusion: The online chemical cleaning technology that allows for cleaning of the condenser without shutting it down serves as an advanced alternative to ball cleaning. Its application in the 35MW high-temperature, ultra-high-pressure reheated steam turbine generator set of the Xuzhou Tongshan biomass cogeneration project shows that scaling on the heat exchange tubes of the condenser has a significant impact on power generation. This online cleaning technology manages to resolve issues such as increased exhaust temperature, reduced vacuum level, and increased terminal difference in the plant’s condenser within 10 hours. Compared to the chemical or mechanical/physical cleaning methods that require shutting down the traditional condenser due to scaling, the online chemical cleaning technology for condensers that allows operation to continue enables maintaining the condenser’s cleanliness factor and preventing corrosion inside it. It achieves good results in terms of operation, safety, and cost-effectiveness, with minimal modifications to existing equipment, within a relatively short period of time. It is proven that the online chemical cleaning technology for condensers without shutdown has practical significance for adoption and promotion in the thermal power industry. Nine common device problems in condenser ball cleaning and their solutions (Yan Hui)