Common cleaning processes and procedures for heat exchangers

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Heat exchanger cleaning: Heat exchangers need to be cleaned due to corrosion, erosion, and scale buildup caused by the fluids they handle. Below are several common cleaning methods, with specific implementation details as follows: Mechanical descaling method – When there is slight blockage or accumulation of debris and scale in the tube bundle of a shell-and-tube heat exchanger, stainless steel rods or low-carbon copper discs can be used to remove these deposits by inserting them from one end and pulling them out from the other end. For light deposits, a specialized pipe cleaning brush can be used, one end of which is fitted with thick iron wire; by pulling this brush through the heat exchange tubes, the deposits or foreign objects that are not firmly attached to the tubes can be removed after repeating the process several times. When the fouling inside the pipe is severe or the pipe is completely blocked, it can be cleaned by using a soft metal rod to probe it. When the opening of a pipe is clogged by scale or foreign objects, manual methods such as shoveling, cutting, scraping, and brushing can be used to deal with it. High-pressure water jet cleaning: This method utilizes high-pressure water generated by a high-pressure water pump, which is delivered directly to the area to be cleaned through a specialized cleaning gun. The pressure range for adjustment is 0~100 MPa. When the scaling is not too severe, a pressure of around 40 MPa can be selected. When the structure is rigid and compact, a high-alloy nozzle can also be inserted into the tube to carry out cleaning at higher pressure. This method is generally used to remove scale from the inside of tubes in shell-and-tube heat exchangers, or to clean the scale and debris on the surface of the heat exchanger housing and tube bundles in devices where these tube bundles can be removed. For example, in the cleaning process of U-tube heat exchangers: (1) The cleaning personnel must wear appropriate personal protective equipment ； (2) Adjust the water pressure appropriately based on the conditions of the equipment itself, paying attention to the safety of both personnel and the equipment ； (3) Try using a water gun ； (4) Clean the tubes and shell side of the heat exchanger; if the equipment’s head has been removed, a safety zone should be established in the direction in which the water gun sprays water during cleaning, with a dedicated person to monitor it. Chemical descaling involves first conducting a chemical analysis of the scaling substances, and then deciding on the solvent to be used for cleaning. Generally, alkaline cleaning is used for sulfate and silicate scale, while acidic cleaning is used for carbonate scale. For oil-based scale and coking, substances such as sodium hydroxide, sodium carbonate, laundry powder, and detergents are used in combination with water in specific proportions for cleaning. When using chemical cleaning, it is necessary to consider adding a corrosion inhibitor. After chemical cleaning, rinse several times with clean water until the water becomes neutral. In addition to the above cleaning methods, the automatic sponge ball cleaning method can also be used.