In the cooling circuit of a chemical reactor, periodic fluctuations in the outlet temperature of a welded plate heat exchanger, or a gradual increase in the pressure drop across the plate channels, are phenomena commonly encountered by field operation and maintenance personnel. These problems are mostly related to medium flow velocity, degree of fouling, and thermal stress, and need to be investigated item by item according to the specific operating conditions.
A: In the reactor cooling circuit, periodic temperature changes subject the plates to alternating thermal stress. If the channel flow velocity is too low, the medium residence time is prolonged, making local fouling likely and aggravating thermal stress fatigue; if the flow velocity is too high, the risk of erosion corrosion may increase. It is recommended to check the flow velocity once a quarter to ensure it is within the design range, and to record the trend of inlet and outlet pressure difference changes.
A: This heat exchanger is suitable for heat exchange between liquids and gases that are clean or only lightly fouling, such as hydraulic oil cooling, domestic hot water preparation, and process fluid heat recovery. If the medium contains particulate matter or is prone to crystallization, a filter should be installed at the inlet and backflushed regularly. For corrosive media, the compatibility of the plate material and sealing material should be verified to avoid leakage caused by improper selection.
A: Taking the YBJ-35 model as an example, welding is used instead of gaskets between plates, the design pressure can reach 3.0 MPa, the design temperature is -40°C to 200°C, and the heat transfer area of a single unit is 0.5–35 m². During actual operation, overpressure and overtemperature should be avoided, and attention should be paid to the effect of temperature alternating frequency on welded joints.
A: Record the inlet and outlet temperatures, pressures, and pressure drop every shift, check for signs of external leakage every week, and compare historical data every month to judge the fouling trend. If the pressure drop continues to rise or the temperature difference efficiency decreases, cleaning should be arranged or channel blockage should be checked.
A: For long-term shutdown, the internal medium should be drained completely, and if necessary, flushed with clean water and blown dry to prevent residual matter from corroding the plates. Before restarting, a pressure test is required to confirm that there is no leakage at the welded parts.
