All welded plate heat exchanger

Heat exchangers developed up to the present time may generally be classified into two categories, namely tubular exchangers and plate exchangers. The conventional plate heat exchangers are manufactured by stacking a plurality of plates, configured in a way so that two fluids, one relatively hot and the other relatively cold, may be passed between alternating channels formed by the plates. Plate heat exchangers may be further broken down into two categories, namely gasket-containing heat exchangers and all-welded heat exchangers. Gasketed exchangers have many advantages over all welded exchangers, three of which being the accessibility of plates for cleaning, lower thermal stresses, and cost per area; however, distinct limitations are present. Gasket limitations occur with temperature, pressure, and compatibility with fluids used. To overcome these limitations, plate heat exchanger manufacturers have developed all welded plate heat exchangers. The major problem encountered with existing all welded units is the excessive thermal stresses present which leads to shorter equipment life. High manufacturing cost of separating the relatively hot and relatively cold fluid via common welding procedures and excessively thick heat transfer plates are other disadvantages. The invention relates to an all-welded plate heat exchanger comprised of a plurality of plates welded together to form cassettes that are stacked one upon the other so as to provide primary and secondary alternating channels through which fluids are adapted to flow for exchanging heat. The primary channels provided within the cassettes connect at opposite ends with inlet and outlet openings. The cassettes are welded along two opposing sides via resistance seam welding. Baffle clips are fastened between the cassettes to partially close off the sides of the secondary channels provided between the cassettes. Two inlet headers, two outlet headers, a top cover member and a bottom cover member enclose the stacked cassettes.