On site, a preliminary judgment can be made based on the deviation between the heat exchange outlet temperature and the design value, and changes in the shell-side pressure drop. When the outlet temperature drops by more than 5°C compared with the initial operating data, or the shell-side pressure drop increases by more than 15%, cleaning should be scheduled. Before cleaning, confirm that the medium has been drained and isolated. Carbon steel shells may be cleaned mechanically or chemically, while stainless steel shells must avoid the use of chlorine-containing cleaning agents.
Common causes include: fouling on the inner wall of the heat exchange tube bundle leading to a decrease in heat transfer coefficient, damage to the shell-side baffles causing fluid short-circuiting, and flow distribution of hot and cold media deviating from the design conditions. It is recommended to first check the readings of the flow meter and temperature transmitter, and then inspect the fixing status of the baffles and tube bundle. If the deviation persists, the actual heat load can be reviewed against the design parameters of a nominal heat exchange area of 4.5 square meters to determine whether it exceeds the selection range.
When the operating temperature is ≤400°C, the jacket material can be selected from carbon steel, stainless steel, or alloy materials according to the corrosivity of the medium. For neutral water or low-corrosivity oils, a carbon steel jacket can meet the service requirements; for media containing acids, alkalis, or chloride ions, a stainless steel jacket is recommended; for strongly corrosive conditions, the economic feasibility of alloy materials should be evaluated. The heat exchange tubes use seamless steel tubes or stainless steel tubes, and the material selection must match the shell material to avoid galvanic corrosion.
When shutdown exceeds one week, the medium in the shell side and tube side should be drained completely and purged with dry compressed air. The coating integrity on the surface of the carbon steel shell should be checked, and any rust found should be treated promptly. In cold environments, confirm that retained water has been drained to prevent the tube bundle from freezing and cracking. Before restarting, perform a tightness check at the design pressure of 1.6MPa and verify the calibration status of instruments within the operating temperature range of -20°C to 150°C.
