According to the relevant requirements of GB/T 151 and TSG 21, when a welded plate heat exchanger operates within a design pressure of 3.0 MPa and a design temperature range of -40°C to 200°C, the flow velocity in the plate channels shall be rechecked periodically. Maintenance work should establish records starting from the first month of commissioning. The following points are provided for reference by design selection and operation and maintenance personnel.
In the cooling circuit of a chemical reactor, the temperature changes periodically, and excessively low flow velocity in the plate channels will aggravate thermal stress fatigue. It is recommended to calculate the minimum flow velocity during the selection stage, and after operation, recheck the deviation between the actual flow rate and the design value once every quarter. When the deviation exceeds 15%, the valve opening of the circuit should be adjusted or a bypass should be added.
Welded plate heat exchangers use welding instead of gaskets, and their pressure and temperature resistance are limited by the plate material and welding process. During operation and maintenance, the readings of on-site pressure gauges and thermometers should be checked to ensure they do not exceed the range specified on the nameplate; under over-limit conditions, forced operation is not allowed, and whether to continue use should be decided only after shutdown and troubleshooting.
The cleaning cycle is determined according to the scaling tendency of the medium, and for conditions prone to scaling, it may be shortened to 3 to 6 months. After evaluating the impact of cleaning shutdown on production, decide whether to add standby equipment. Standby equipment should preferably be of the same model and parameters as the online equipment to facilitate interchangeability.
Inspection contents include leakage at connections, changes in pressure drop, and the integrity of the insulation layer. After each cleaning and maintenance, update the operation log, recording pressure drop, temperature difference, and cleaning method, so as to provide data support for the next cycle's maintenance plan.
