Proper operation and maintenance of heat exchangers are of key importance for ensuring efficient and safe equipment performance. Heat exchangers play a crucial role in maintaining energy balance and the economic efficiency of technological processes. If heat transfer surfaces become contaminated or damaged, heat exchange efficiency decreases, leading to higher energy consumption and increased operating costs. Regular technical maintenance helps prevent such issues, extending equipment service life and reducing replacement frequency.
Improper maintenance can lead to serious breakdowns that require costly repairs or even full replacement of the heat exchanger. Preventive maintenance, on the contrary, helps to detect and eliminate minor faults in time, ultimately saving money and resources. In addition, proper operation of heat exchangers supports compliance with regulatory requirements and safety standards. Heat exchangers are often used in systems where temperature and pressure must be strictly controlled, and any deviation from the norms may pose a risk to personnel safety and the environment.
Efficient heat exchangers maintain stable temperature conditions during production, which is critically important for ensuring the quality of the final product. Improper operation may disrupt the technological process, reduce product quality, and increase the amount of defective output. Moreover, poorly maintained heat exchangers can cause leakage of hazardous substances or lead to inefficient resource use, increasing the carbon footprint and negatively impacting the environment.
Thus, proper operation and regular maintenance of heat exchangers not only improve energy efficiency and extend equipment service life, but also ensure safety, reduce operating costs, and minimize environmental impact.
What are tubular heat exchangers?
Tubular heat exchangers
Tubular heat exchangers are devices for transferring heat between two or more fluids separated by solid surfaces and capable of operating under different pressures. They consist of a bundle of tubes installed inside a shell through which heat transfer media circulate. Typically, one fluid flows inside the tubes, while the other flows outside them in the space between the tubes and the shell.
Main structural elements of tubular heat exchangers:
Tube bundle: The main part of the heat exchanger, consisting of many thin tubes made of high thermal conductivity materials (such as stainless steel, titanium, or copper alloys). The fluid flowing inside the tubes is called the “internal” heat transfer medium.
Shell (housing): The outer casing through which the “external” heat transfer medium circulates. It can be cylindrical or of another shape, ensuring optimal contact between the inner tubes and the external medium.
Tube sheets: Plates to which the tubes are fixed at both ends. They ensure tight separation of the two media and hold the tubes in place.
Heads or covers: Close the ends of the shell and serve for the inlet and outlet of heat transfer media. Depending on the design, they may be removable or fixed to facilitate access for cleaning and repair.
Principle of operation of tubular heat exchangers:
Heat is transferred from the hot fluid to the cold one through the tube walls. The hot medium gives up part of its heat to the tube walls, which in turn transfer this heat to the cold medium. The process may be single-pass or multi-pass depending on the design and flow direction.
Advantages of tubular heat exchangers:
High reliability and durability: Robust construction allows operation under high pressure and temperature, making them suitable for harsh conditions.
Versatility: A wide range of sizes and configurations allows use in various industries such as oil and gas, chemical, power generation, food, and others.
Disadvantages:
Size and weight: Tubular heat exchangers are often larger and heavier than, for example, plate heat exchangers.
Difficult cleaning: In some designs, access to internal tubes is limited, making cleaning and maintenance more complex.
Operation of tubular heat exchangers
Operation of tubular heat exchangers includes proper installation and start-up of equipment, control of operating parameters, and regular monitoring and analysis of the heat exchanger’s condition.
Proper installation and start-up
To ensure reliable operation, the tubular heat exchanger must be installed correctly. A suitable location must be selected to ensure easy access for maintenance and repair. The unit must be mounted on a strong base capable of withstanding its weight and operating vibrations. All connections (inlets and outlets for heat transfer media) must follow manufacturer recommendations to prevent leaks and equipment damage.
Before start-up, all joints and seals must be checked for tightness. It is also important to ensure that there are no foreign objects inside the tubes or shell that could cause blockages or damage heat transfer surfaces. After inspection and elimination of issues, a gradual start-up is performed, beginning at low pressure and slowly increasing to operating conditions.
Control of operating parameters
During operation, key parameters such as pressure, temperature, and flow rate must be monitored. Regular monitoring allows for timely detection of deviations and prevention of emergency situations.
Pressure: Must remain within the manufacturer’s specified range. Excessive pressure may damage tubes or connections, while low pressure reduces heat exchange efficiency.
Temperature: Monitoring inlet and outlet temperatures helps evaluate heat exchange efficiency. A reduced temperature difference may indicate fouling or damage to heat transfer surfaces.
Flow rate: Stable flow is essential for efficient operation. Deviations may indicate blockages, leaks, or other system issues.
Regular monitoring and analysis
Monitoring includes visual inspection and diagnostics using specialized equipment. Visual inspection detects visible damage, leaks, corrosion, or contamination. Diagnostic tools (such as ultrasonic thickness gauges or thermal imaging cameras) help identify hidden defects such as tube wall thinning or internal blockages.
It is also recommended to regularly analyze operating data (pressure, temperature, flow rate) to assess performance trends. If deviations are detected, corrective actions must be taken, such as cleaning, component replacement, or operational adjustment.
Main problems during operation and solutions
- Fouling and contamination of heat transfer surfaces
This is one of the most common issues caused by deposits (scale, sediment, corrosion products). It reduces heat transfer and increases flow resistance.
Solution: Regular cleaning (mechanical or chemical), monitoring fluid quality, and installing filters. - Corrosion
Caused by aggressive fluids, electrochemical processes, or poor water quality. Leads to leaks and wall thinning.
Solution: Use corrosion-resistant materials (stainless steel, titanium), control fluid composition, and inspect regularly. - Leaks
Caused by tube damage, seal failure, or poor connections.
Solution: Regular inspection, timely seal replacement, and repair of damaged parts. - Thermal stress and deformation
Rapid temperature changes can cause mechanical stress and structural damage.
Solution: Control temperature gradients, use expansion compensators, and ensure proper design. - Erosion
Caused by high-velocity flow with abrasive particles, leading to tube wear.
Solution: Reduce flow velocity, use wear-resistant materials, and install filters or cyclones.
Maintenance of tubular heat exchangers
Planned maintenance includes regular inspections, cleaning, and integrity testing. Frequency depends on operating conditions and may vary from monthly to annual.
Main maintenance procedures:
Inspection and diagnostics: Visual inspection for leaks, corrosion, and damage.
Operating parameter check: Monitoring pressure, temperature, and flow rate.
Cleaning: Mechanical or chemical removal of deposits.
Corrosion inspection: Using ultrasonic or other non-destructive testing methods.
Cleaning methods
Mechanical cleaning: Uses brushes, scrapers, or high-pressure water jets to remove deposits. May require partial disassembly.
Chemical cleaning: Uses acidic or alkaline solutions to dissolve scale, organic deposits, and corrosion products.
Inspection of corrosion and damage
Non-destructive testing methods such as ultrasonic thickness measurement, dye penetrant testing, or radiography are used to detect defects at early stages.
Repair and replacement
Tube repair: Replacement of damaged tubes, sealing leaks, or welding.
Seal replacement: Timely replacement of worn gaskets.
Tube sheet repair: Partial or full repair in case of damage or corrosion.
