After chemical or mechanical cleaning of a shell and tube heat exchanger on site, if the re-measured inlet and outlet pressure drop is still higher than the design range, check the following points in sequence: whether the baffle cut is aligned, whether the clearance between the tube bundle and the shell exceeds the standard, and whether there is residual scale on the inner wall of the heat exchange tubes. In particular, after cleaning, the pressure drop must be re-measured to confirm that it has returned to the design range. If the pressure drop has not decreased, it is recommended to use a borescope to randomly inspect the inner wall of the tube side.
When operations and maintenance personnel participate in model selection review, it is recommended to focus on checking two types of parameters: the first type is design pressure and design temperature, such as the GCH-280 with a design pressure of 1.6 MPa and a design temperature of 200°C; the second type is nominal heat exchange area and medium inlet/outlet pipe diameter, which must match the actual operating conditions of the system to avoid abnormal pressure drop caused by an undersized pipe diameter.
According to differences in medium corrosiveness, the tube side and shell side can respectively adopt carbon steel or stainless steel combined structures. For example, when the shell side carries cooling water, carbon steel can be selected; when the tube side carries a corrosive medium, a stainless steel tube bundle can be selected. When replacing the tube bundle on site, attention must be paid to the difference in linear expansion coefficient between the two materials to avoid concentrated thermal stress.
It is recommended to record inlet and outlet temperature, pressure drop, and flow rate every two hours. When the pressure drop rises by more than 15% above the initial value, or the temperature difference efficiency drops by 5%, cleaning or inspection of the baffles should be arranged. The GCH-280 has a nominal heat exchange area of 280 m² and is suitable for medium-load heat exchange conditions. During on-site installation, space must be reserved for tube bundle extraction.
If the outlet temperature is low while the heat source is normal, first check whether the shell side is short-circuited and whether the tube bundle is blocked. If the pressure drop suddenly increases, check the inlet filter and pipe openings for foreign matter. The shell and tube heat exchanger has a sturdy structure, but during maintenance it still must be disassembled and assembled according to operating procedures to avoid damaging the sealing gaskets.
