Online cyclic cleaning process for plate heat exchangers

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The cleaning methods for plate heat exchangers include online circulating cleaning and disassembly immersion cleaning. Before cleaning, scale samples can be analyzed based on the quality of the circulating water, allowing for the selection of the appropriate cleaning method. Today, the editor will mainly introduce the online cyclic cleaning process for plate heat exchangers: (1) Check whether the inlet and outlet valves of the heat exchange equipment can be closed tightly, to determine if a closed-loop cyclic cleaning is possible; add blind flanges if necessary ； (2) First, calculate the amount of pure cleaning agent required based on the heat exchange area of the heat exchanger and the thickness of the scale buildup ； (3) Based on the volume of the pipeline, prepare a container for holding the cleaning agent; the inner surface of the container must be clean and free of oxidation layers, or a container made of non-metallic material should be used ； (4) Isolate the equipment system and drain all the water from the heat exchanger ； 　　 (5) After using high-pressure water to clean the impurities such as silt and algae remaining in the pipes, seal the system ； 　　 (6) Pour an adequate amount of cleaning agent into the container, connect a transfer pump and connecting pipes, then turn on the switch to perform a closed-loop cleaning of the heat exchange equipment ； (7) Pump the required cleaning agent into the heat exchanger, allowing it to flow in from the bottom of the heat exchanger and out from the top. (Determine whether it is necessary to dilute the concentrate cleaning agent based on the operating conditions; the ratio shall be adjusted according to the actual conditions.) (8) Repeat the cleaning cycle until the recommended cleaning time is reached. During the cyclic cleaning process, due to the chemical reaction between the cleaning agent and the scale, visible dissolved scale impurities as well as foam can be found in the solution tank. The amount of gas generated during this reaction also increases, so excess air should be removed at all times through the vent valve. As the air is expelled, the space inside the heat exchanger increases, and appropriate amounts of water can be added; do not pour in a large amount of water at once, as this may cause water to overflow. 　　 (9) During the cycle, it is necessary to regularly check the effectiveness of the cleaning agent, which can be determined using pH test strips. If the solution is maintained at a pH of 2–3, the cleaning agent remains effective. If the pH value of the cleaner reaches 5–6, an appropriate amount of cleaner needs to be added. The pH value of the final solution remained unchanged for 30 minutes at 2–3, indicating that the cleaning effect had been achieved. (10) After the cleaning time has elapsed, recover the cleaning solution. Replace the liquid in the container with clean water to carry out cyclic cleaning and replacement, flushing away the scale and other impurities that have detached and remain in the heat exchanger until the pH level reaches 6–7, as determined using a pH test strip. The cleaning process also requires swapping the inlet and outlet pipes for repeated flushing. 　　 (11) After cleaning is complete, it can be turned on for operation or subjected to a pressure test to check for any leaks. In the event of a leak, carry out repairs promptly.