Large heat exchangers are mainly used in chemical, petroleum, metallurgy and other fields. However, after a period of use, large heat exchangers will experience problems such as scaling, clogging, and corrosion, which may lead to leakage and bring some hidden dangers and problems to enterprises. In response to such situations, what treatment measures should be taken?
Equipment Inspection: Before starting, confirm that the unit, piping, and valves are leak-free. In particular, check the plate heat exchanger's gaskets for aging or deformation to avoid contamination or corrosion caused by media mixing. Also, check the pump bearing lubrication and ensure the motor's direction of rotation is consistent with the markings.
Load Regulation Strategy: Based on changes in heating demand, the secondary water supply temperature is controlled by adjusting the opening of the primary electric control valve or the speed of the variable frequency pump. For example, during the initial heating period, the secondary water supply temperature can be set to 45°C and gradually increased to 55°C as the outdoor temperature drops, avoiding energy waste caused by frequent starts and stops.
Daily Inspections: During each shift, record the primary and secondary side temperature, pressure, and flow rate data, and observe the pump operating sound and motor temperature (usually ≤70°C). If pump vibration exceeds 4.5mm/s (ISO 10816 standard), immediately stop the machine for inspection.
Plate Maintenance: Disassemble and inspect the plate heat exchanger at least once a year to check for cracks, deformation, or aging of the gaskets. When replacing gaskets, use a material compatible with the media (e.g., EPDM for hot water, NBR for oil-containing media) and ensure that the plate arrangement is consistent with the original design.
Leakage Emergency: If a plate heat exchanger leak is detected, immediately close the primary and secondary inlet and outlet valves, drain the media, and then disassemble and inspect. Minor leaks can be corrected by tightening bolts or replacing gaskets. Perforated plates require complete replacement.
Overtemperature and Overpressure Handling: When the secondary water supply temperature exceeds the set value by 5°C or the pressure exceeds the design value by 10%, the system will automatically trigger an alarm and shut down. Operators will check the temperature sensor and regulating valve for malfunctions and switch to a backup unit if necessary.
Power Outage Recovery: After a sudden power outage, close the electric control valve first and then gradually open it after power is restored to avoid damage to the plate due to sudden pressure changes. Sensor data must also be recalibrated to ensure accurate control logic.
The operation of heat exchange units must comply with standards such as GB/T 15386-2008, "Plate Heat Exchangers," and TSG 21-2016, "Regulations on Safety Technical Supervision of Stationary Pressure Vessels." It is recommended to establish an operation log to record daily parameters, maintenance details, and abnormal conditions, and retain this log for at least three years to facilitate inspection by regulatory authorities.
Abnormal conditions must be tolerated and stored for at least three years for inspection by regulatory authorities.
When operating a large heat exchanger, especially during initial testing, proceed slowly, fully preheating the unit and gradually increasing the temperature. Preheat and adjust the pressure reducing valve after commissioning. When starting a large heat exchanger, open the cold-side valve first and then the hot-side valve after stabilization.When shutting down, close the hot-side valve first, then the cold-side valve. After a large heat exchanger is operating normally, close the steam-water heat exchanger's steam trap bypass valve. If the steam trap temperature is too low, such as below 50°C, the through-valve can be opened for operation. If the steam trap temperature is too high, such as above 90°C, and the condensing system is operating without pressure, close the bypass valve to prevent steam from passing through.
It is necessary to select a reasonable large heat exchanger unit, otherwise it is easy to cause damage to the heat exchanger unit. Use a fixed tube sheet heat exchanger unit, and the stress caused by the thermal expansion of the tube shell should not exceed the design stress range.Otherwise it is easy to cause deformation and damage of structural materials. An expansion joint structure should be used to increase stress, or a floating head type or U-shaped tube type should be selected to ensure that the tube bundle can expand and contract freely.
As an operator of a large heat exchanger unit, once there is a slight change in the process operating parameters, or when abnormalities or suspected internal leakage of the heat exchange equipment are found, portable instruments are used to detect, analyze and monitor each heat exchanger to check and confirm internal leakage.
Strictly implement procedures and process requirements, and strictly prohibit over-temperature, over-pressure, and overload operations. Implement equipment status inspections and strict equipment maintenance and regular overhauls to ensure that the equipment and heat exchange equipment are in good condition.
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