Does a gasket leak always mean the plates are damaged? During on-site troubleshooting, many maintenance personnel directly replace the plates, but overlook two more common causes: preload force and gasket selection.
First confirm whether the bolt preload is uniform. A plate-and-frame heat exchanger relies on bolts to compress the plates and gaskets together. If the elongation of each bolt is inconsistent, the pressure on the local sealing surface will be insufficient, and the medium will seep out from the gasket edge. It is recommended to retighten in a diagonal sequence in multiple passes and verify with a torque wrench. Second, check whether the gasket is compatible with the medium. If the autoignition temperature of the medium is 200°C, a group of T3 or above should be selected, and T2 or below must not be selected; otherwise, after long-term operation, the gasket will easily harden and lose elasticity.
When local rust spots or a thin layer of scale appear on the plate surface, heat transfer efficiency will gradually decrease. Cleaning should use a chemical cleaning agent compatible with the plate material, and tools such as wire brushes should be avoided to prevent mechanical scratching of the plate surface. If pitting has already penetrated the plate, replacement is required. During routine inspections, the inlet and outlet pressure difference can be recorded; a continuous increase in pressure difference usually indicates fouling.
Herringbone corrugation is suitable for most conventional working conditions, and a combination of deep and shallow corrugations can be used in situations where pressure drop is limited. During selection, if the medium flow rate is relatively large and the allowable pressure drop is relatively small, the deep-shallow combination pattern may be given priority.
Before long-term shutdown, the medium should be drained completely, and the bolts should be loosened until the plates are no longer under pressure, so as to avoid the gasket being kept in a compressed state for a long time. When putting it back into operation, tighten in a diagonal sequence in multiple passes to the specified dimension.
