The plate heat exchanger is made up of a plurality of corrugated metal sheets, which are sealed by gaskets, and thin rectangular passages are formed between the plates to exchange heat through the plates.The main cause of corrosion of plate heat exchanger
(1) The stainless steel heat transfer plate is mechanically stamped, inevitably retaining a certain amount of surface residual stress. For stainless steel sheets without molybdenum, the elimination of surface residual stress is very difficult or impossible.
(2) After the plates are assembled, a multi-slit structure is formed, such as a contact between the plates, a bottom of the sealing groove. The gap is easy to cause the enrichment of Cl-, and the degree of local enrichment often far exceeds the ability of stainless steel itself to resist stress corrosion.
(3) When the dirt on the surface of the sheet is severe, the corrosive elements (Cl, S) in the medium may adhere to the dirt in a large amount and be enriched in the gap at the bottom of the scale.
(4) The harmful elements in the bottom of the sealing groove are often precipitated by the temperature rise of Cl in the binder.For example, the neoprene series of adhesives and compressed asbestos (containing CaCl2) form Cl- and H under the conditions of water and steam to form HCl+, causing severe stress corrosion cracking at the bottom of the groove.