During on-site operation and maintenance, issues such as large fluctuations in heat exchanger outlet temperature, abnormally increased pressure drop, or cross-contamination between tube-side and shell-side media are commonly encountered. The following summarizes common questions and handling points for the QHL-88 shell-and-tube heat exchanger from an O&M perspective.
First, verify whether the four basic parameters—heat load, flow rate, inlet and outlet temperatures, and allowable pressure drop—are consistent with the design conditions. If the medium temperature reaches the process setpoint, the control system adjusts the output power of the electric heater through PID calculation based on the temperature sensor signal, thereby achieving temperature control for resistive loads. At this point, check whether the temperature sensor installation location is affected by dead zones, whether the PID parameters match the current load, and whether the control valve has internal leakage. The applicable temperature difference range of the QHL-88 is -20°C to 150°C; when exceeding this range, the thermal compensation method and material adaptability need to be re-verified.
An increase in pressure drop is usually related to fouling between baffles, deposition on the outer wall of the tube bundle, or failure of the shell-side inlet filtration. During O&M, first compare recent pressure drop records with the design allowable value, then arrange a shutdown inspection to check whether the baffle notches are blocked and whether dirt adheres to the tube bundle surface. During cleaning, take care to avoid damaging the tube walls, and reinstall the baffles to maintain the original flow direction arrangement.
Cross-contamination is mostly related to seal failure at the tubesheet connection or corrosion perforation of the heat exchange tubes. After discovering the abnormality, isolate the equipment and conduct pressure tests on the shell side and tube side separately to locate the leak point. If it is a tube-end sealing problem, re-expanding or welding can be performed according to the manufacturer's requirements; if it is tube bundle damage, the feasibility of plugging tubes or replacing the tube bundle needs to be evaluated.
For daily inspections, it is recommended to record inlet and outlet temperatures, flow rates, and pressure drop trends, and to schedule cleaning cycles based on medium characteristics to reduce unplanned downtime.
