How to Clean a Heat Exchanger: An Explanation of Cleaning Methods
Heat exchangers are everywhere, doing important work behind the scenes that we don’t usually notice. These little champs are part of the machinery we rely on every day, whether it’s the AC keeping us cool, power plants making electricity, or even the cars we drive. They’re like the unsung heroes, quietly helping out in the background. Their main gig is moving heat around efficiently, which is key for things like keeping our food cold and making chemicals. Even though they’re pretty common, most people don’t give them a second thought. It’s their low-key way of operating that lets them blend into all sorts of gadgets, playing a crucial role in how our tech-filled world keeps running smoothly.
Shell and tube heat exchangers are like a goldmine for making things work better because pretty much all of them get a bit less effective over time due to gunk building up inside of the tubes – known as fouling. Virtually all heat exchangers suffer from some degree of efficiency degradation due to fouling. While the inefficiency is difficult to quantify, it most certainly measures in the hundreds of billions of dollars or greater. This makes deciding how to clean heat exchangers an important step in saving on energy costs.
Best Practices for Maintaining Shell and Tube Heat Exchangers
Maintaining shell and tube heat exchangers is crucial to ensure optimal performance and longevity of equipment. Several factors play a key role in the maintenance of heat exchangers:
Heat Exchanger Cleaning
Regular cleaning is essential to remove fouling and deposits on both the tube and shell side. Fouling can include scales, sediments, corrosion products, and biological growth. Mechanical and chemical cleaning methods may be employed, such as using brushes, water jets, or cleaning solutions to dissolve deposits.
Inspections to Determine Tube Integrity
Periodic inspections help identify signs of corrosion, erosion, or leakage. Inspect the tubes, tube sheets, shell, and other components for any physical damage. Non-destructive testing methods, such as ultrasonic testing and eddy current testing, can be used to check for tube integrity and thickness.
Tube Cleaning tools
Consider employing tube cleaning devices, such as brushes or scrapers, to prevent fouling and deposit buildup inside the tubes. Automatic tube cleaning systems are emerging as best practice by maintaining heat transfer efficiency by keeping tubes free from contaminants preventatively while the heat exchanger is in operation.
Regularly analyze the properties of the fluids circulating in the heat exchanger. This can help identify potential issues, such as corrosion or contamination. Analysis should focus on both the shell side and tube side. Monitor and adjust chemical treatment programs as needed to prevent scaling, corrosion, or biological growth.
Check the integrity of seals and gaskets to ensure there are no leaks. Leaks reduce efficiency and can lead to cross-contamination between the tube and shell side fluids.
Temperature and Pressure Monitoring and Management
Monitor operating temperatures and pressures to ensure they are within design specifications. Deviations from the recommended ranges can indicate problems that need attention.
Often neglected, sensors that provide insufficient or wrong data can serve to mask heat exchanger problems and keep efficiency related problems hidden from managers.
Monitor vibrations to detect any abnormalities or excessive wear in rotating equipment such as fans or pumps. Excessive vibration can lead to mechanical failures.
Documentation, Data Analysis, Storage and Record Keeping
Maintain detailed records of maintenance activities, inspections, and any repairs. This information encourages maintenance discipline and can help track the performance of the heat exchanger over time and guide future maintenance decisions. Collection and evaluation of data generated in the heat exchanger ecosystem enables proper measurement and fault detection. Data is necessary for establishing heat exchanger optimization.
Training and Education
Maybe the most important aspect of heat exchanger optimization, leaders should ensure that personnel responsible for heat exchanger maintenance are well-trained and knowledgeable. Proper training leads to more effective troubleshooting and preventive measures.
By addressing these factors, operators can enhance the reliability and efficiency of shell and tube heat exchangers, ultimately extending exchanger operational life and minimizing downtime. Regular, effective preventive maintenance is key to achieving these goals.
Regarding the above management priorities, tube fouling is perhaps the most urgent management requirement due to its outsized impact on heat exchanger efficiency and operability. Per the US Department of Energy, fouling as little as a few microns thick can reduce the efficiency of a shell and tube heat exchanger by more than 10 percent.
What is tube fouling?
For perspective, or review for many, tube fouling refers to the accumulation of unwanted deposits or substances on the internal surfaces of the tubes within a shell and tube heat exchanger. Fouling affects almost all heat exchangers, including water-cooled chillers, and it can significantly impact the performance and efficiency of the equipment. The substances that contribute to fouling can vary and may include:
- Scales: Deposits of minerals, such as calcium carbonate or calcium sulfate, that precipitate out of the water or other fluids flowing through the tubes. Scales can reduce heat transfer efficiency.
- Sediments: Solid particles suspended in the fluid that settle on the tube surfaces over time. Sediments can accumulate and create a layer that hinders heat exchange.
- Corrosion Products: The result of chemical reactions between the fluid and the tube material, leading to the formation of corrosion by-products. Corrosion products can contribute to fouling and reduce the life of the tubes.
- Biological Growth: Microorganisms, algae, or bacteria that thrive in the fluid and attach to the tube surfaces. Biological growth can form biofilms, contributing to fouling and reducing heat transfer efficiency.
In shell and tube heat exchangers or water-cooled chillers, tube fouling is problematic because it decreases the overall heat transfer rate between the fluid inside the tubes and the fluid outside the tubes. This reduction in heat transfer efficiency leads to several negative consequences, including increased energy consumption, decreased cooling capacity, and potential equipment damage.
What are the best tube cleaning methods for shell and tube heat exchangers?
The problem of fouling is ubiquitous to heat exchangers and represents the largest barrier to optimized efficiency—but the solution the solution is generally straightforward. Simply put, if the internal surface of the heat exchanger’s tubes are kept clean during operation, the problem of fouling related inefficiency almost entirely disappears. So, what can we do to keep the tubes clean in an operating heat exchanger?
There are several options for fouling mitigation when choosing how to clean a heat exchanger, both as maintenance and preventative measures including:
- Manual cleaning during shutdown periods (planned or unplanned)
- Chemical injection during operation
- Chemical cleaning during shutdown periods
- Employ Automatic Tube Cleaning Systems (ATCS)
The above methods all require the same general management considerations for implementation, execution, and operations. The manager must carefully consider many issues when determining how to clean a heat echanger inclusin all methods, resources, and timelines.
When focusing specifically on tube cleaning, manual tube cleaning can be a challenging but necessary task. Manual tube cleaning remains the most common practice in choosing how to clean heat exchanger tubes. Several key issues can arise during the manual tube cleaning process, and addressing these challenges is crucial to maintaining the efficiency and performance of the exchanger.
Here are some key issues associated with manual tube cleaning in exchangers and chillers:
Labor Requirements: Manual tube cleaning is a labor-intensive process, especially in large heat exchangers or chillers. The time and effort required for manual cleaning can be significant, leading to increased maintenance costs and downtime.
Limited Accessibility: Sometimes the tubes may be difficult to access, making it challenging for maintenance personnel to reach and clean them thoroughly. This can result in incomplete cleaning translating to chronic reduced efficiency.
Potential for Damage: Improper cleaning techniques or the use of abrasive tools or brushes can damage the tube surfaces. Scratches or gouges on the tubes can compromise their integrity and reduce heat transfer efficiency. Furthermore, excessive use of cleaning chemicals can lead to tube damage.
Incomplete Cleaning: It can be challenging to achieve complete removal of deposits and fouling manually. In some cases, certain types of deposits (hard scale) may adhere strongly to the tube surfaces, making it difficult to eliminate them entirely through manual cleaning. When a heat exchanger is not completely cleaned, the growth and persistence in follow-on fouling can be magnified considerably.
Safety Challenges: When deciding on how to clean a heat exchanger, safety should also be considered. Cleaning often involves working in confined spaces, at heights, and with heavy rigging equipment for the removal of exchanger heads, often using caustic chemicals. All these activities present safety risks. Adequate safety measures, including training and proper equipment, are essential to mitigate these concerns and should be the prime managerial focus.
Downtime and Production Loss: Shutting down the exchanger or chiller for manual tube cleaning results in downtime, which can impact overall production or facility operations. Minimizing downtime and planning cleaning schedules carefully are crucial considerations. Modern ATCS systems greatly reduce the need for shutdown due to cleaning.
Environmental Impact: The cleaning chemicals used during manual tube cleaning may be hazardous or have environmental implications. It’s an important challenge to employ environmentally friendly cleaning solutions and properly dispose of waste in accordance with applicable regulations.
Frequency of Cleaning: Determining the appropriate frequency for manual tube cleaning is crucial. Cleaning too frequently can increase operational costs, while infrequent cleaning can lead to a decline in chiller efficiency.
Monitoring and Assessment: It can be challenging to monitor and assess the effectiveness of manual tube cleaning without advanced tools and technologies. Implementing monitoring systems and regular performance assessments are important for optimizing the cleaning process.
Turning to Modern Technology in Heat Exchanger Cleaning
The weaknesses of manual cleaning are considerable, and many leaders are turning to modern technology to reduce the churn, damage risk and sub-optimal effectiveness associated with manual cleaning. To address these issues, some facilities may explore alternative tube cleaning methods, such as automated or semi-automated systems, to improve efficiency, reduce labor intensity, and enhance overall chiller performance. When deciding how to clean a heat exchanger, regular preventive maintenance planning and adherence to best practices are essential.