When the heat exchanger end cover is opened during maintenance, if uniform thinning or pitting corrosion is found at the tubesheet or nozzle connections, it is often not an operational issue but rather a failure during the selection stage to fully align material and medium operating conditions. For equipment customized to operating conditions such as the HDX-340 hot and cold heat exchanger, involving O&M personnel in selection verification can reduce the probability of subsequent unplanned shutdowns.
Point 1: First confirm medium corrosiveness, then verify material certificates. Under corrosive medium conditions, specifying a stainless steel grade based on experience alone is not reliable. The supplier should be required to provide material certificate documents with the delivery as the basis for incoming acceptance; retain records of medium composition and concentration in the O&M ledger to facilitate comparison of corrosion rates during each maintenance. If the medium concentration or temperature fluctuates periodically, the fluctuation range must be noted in the selection specification rather than giving only normal values.
Point 2: Parameter ranges are not guaranteed values; heat transfer area must be calculated according to operating conditions. Parameters such as heat transfer coefficient, fouling thermal resistance, and flow rate for the HDX-340 hot and cold heat exchanger are usually given as reference ranges, and the specific configuration should be based on operating condition calculation results. O&M personnel can compare actual hot and cold side inlet and outlet temperatures and flow rates to review whether the fouling thermal resistance values in the calculation report cover the scaling tendency of the plant's water quality or medium. Optimistic fouling thermal resistance values are a common cause of reduced heat transfer capacity after commissioning.
Point 3: Nozzle orientation and maintenance space must be settled at the selection stage. It is common on site that after the heat exchanger is in place, there is insufficient space to pull the tube bundle or remove the head. During selection, the equipment layout drawing must be used to confirm whether the shell-side and tube-side nozzle orientations and support leg heights match the existing piping and maintenance access. For operating conditions requiring periodic tube bundle extraction and cleaning, sufficient axial extraction distance should be reserved to avoid later piping modifications.
Point 4: O&M inspection items should be consistent with selection assumptions. Regularly inspecting medium corrosion conditions and the compatibility of materials with operating conditions is a fundamental action for maintaining the design life of the HDX-340 hot and cold heat exchanger. If the medium composition changes during operation, promptly assess whether the originally selected material is still suitable, rather than waiting until leakage occurs. Incorporating corrosion inspection intervals and thickness measurement points into the daily inspection checklist makes material degradation trends traceable.
