During design selection, it is common for the actual flue gas temperature to be slightly above the nameplate margin due to operating condition deviations. If the fin tube bundle of a tubular fin heat exchanger operates near the overheating limit for an extended period, oxidation at the connection between the fins and the base tube will accelerate, affecting heat transfer efficiency. It is recommended that during the hot commissioning stage, multiple temperature measurement points be arranged along the flue gas flow path to record the actual wall temperatures at the inlet and outlet of the fin tube bundle. If local areas are found to approach the allowable upper limit of the material, the flue gas bypass opening can be adjusted or additional temperature measurement points can be included in routine inspections. During maintenance intervals, focus on checking whether the fins in the high-temperature section are warped or discolored, and whether oxide scale has peeled off the outer wall of the base tube.
For high-temperature dust-laden flue gas, the fin spacing can be adjusted within the range of 8–12 mm. A smaller spacing increases the heat transfer area but raises the risk of ash bridging; a larger spacing provides a clearer ash removal channel. During maintenance, the sootblowing cycle should be determined based on the actual ash deposition rate. When using compressed air or sonic sootblowing, the nozzle angle should avoid the fin ends to reduce erosion thinning. During shutdown inspection, check whether ash has hardened at the weld joints connecting the fin roots to the tube wall. If necessary, clean with low-pressure water and dry promptly afterward to avoid corrosion on the tube bundle surface.
The design pressure, design temperature, and connection specifications of the heat exchanger are customized according to project requirements and should be clearly marked on the nameplate. After receiving the equipment, selection personnel should first verify whether the nameplate parameters are consistent with the process package data, paying particular attention to whether reasonable margins are reserved for the design temperatures on the flue gas side and the medium side. The operating and maintenance procedures should state that operation must not exceed the nameplate parameters, to avoid deformation of the fin tube bundle or failure of connection seals due to short-term overtemperature or overpressure.
During operation, inspections should monitor the trend of heat exchanger pressure drop; a continuous increase in pressure drop usually indicates ash deposition or blockage. Inlet and outlet temperatures should also be recorded; if the temperature difference narrows significantly, check whether the fin heat transfer surface is contaminated. During shutdown maintenance, open the inspection ports to observe the appearance of the tube bundle, mark local corrosion points for tracking, and clean the flange sealing surfaces and replace gaskets before reassembly. For long-term shutdown, drain the water from the medium side and keep the interior dry.
Fin tube bundles are custom components. It is recommended to stock a small number of fin tubes of the same specifications separately for the high-temperature and low-temperature sections to facilitate local replacement. Maintenance records should include sootblowing frequency, pressure drop data, wall temperature measurement readings, and cleaning details, providing a basis for the maintenance plan of the next operating cycle.
