If during on-site maintenance you find that the heat exchanger connections do not match the piping, the sheath length is insufficient causing temperature measurement points to be distorted, or medium corrosion causes pitting on the sheath within one year, it is usually not a fault of the equipment itself, but rather key parameters were overlooked during the selection stage. The following points can be used by on-site maintenance personnel for troubleshooting.
Water, oil, air, and neutral chemical solutions have significantly different requirements for sheath materials. Carbon steel sheaths are suitable for mineral oil and neutral water, but are not suitable for long-term contact with weakly acidic or weakly alkaline solutions; stainless steel sheaths are more durable in corrosive media, but the procurement cost increases accordingly. Maintenance personnel should evaluate the initial procurement cost and full-cycle maintenance cost based on the medium composition and annual disassembly frequency, rather than only comparing unit prices.
Flange specifications, thread standards, and nozzle orientation directly affect installation man-hours. During selection, it is necessary to confirm the on-site pipeline nominal diameter, flange standard, and allowable installation space. If the interfaces do not match, on-site modification not only increases downtime but may also introduce new leak points due to welding or adapters.
The sheath length should cover the effective heat exchange area and ensure that the temperature sensing element can contact a representative temperature point. A sheath that is too short will cause temperature measurement lag, while one that is too long may interfere with medium flow. At the same time, the allowable temperature fluctuation range of the equipment must be clarified, and a margin should be reserved under frequent alternating hot and cold conditions to avoid gaps or deformation between the sheath and heat exchange tubes due to differences in thermal expansion.
The sheathed structure facilitates extraction of the core for inspection or cleaning, making it suitable for scenarios with frequent disassembly. During installation, maintenance space, drain port location, and vent direction must be considered. For horizontally installed heat exchangers, ensure that a drain port is provided at the lowest point of the shell to prevent medium residue from causing corrosion during shutdown.
After commissioning, inlet and outlet temperatures, flow rate, and pressure drop changes should be recorded. An abnormal increase in pressure drop usually indicates scaling or blockage, while a decrease in temperature difference may correspond to contamination of the heat exchange surface. It is recommended to stock sheaths or seals according to medium corrosiveness to shorten unplanned downtime.
