Plate heat exchangers provided with heat transfer plates are utilized for exchange of heat between two or more heat exchange fluids. The heat transfer plates may be welded together. The heat transfer plates form plate interspaces adapted to be flowed through by the heat exchange fluids. In some types of plate heat exchangers the plates are provided with port holes which form port channels extending at least partially through the plate heat exchanger. The heat exchange fluids may be e.g. gases, liquids, liquids containing solid matter, etc.
At least one of the heat exchange fluids flows through one of the port channels into selected plate interspaces, over heat exchange surfaces of the plates, to a second port channel. The heat transfer plates are commonly mounted between two thick plates, such as two frame plates. The frame plates ensure that the heat exchanger withstands the pressure of the heat exchange fluids and at least one of the frame plates comprises connections for leading at least one of the heat exchange fluids into and/or out from the port channels.
A fluid-tight seal must be provided between a frame plate and an outer heat transfer plate around its port hole/s. One factor in achieving such a seal is to provide a firm connection with the port hole/s of the outer heat transfer plate, which connection will withstand the pressure required to achieve the fluid tight seal. Otherwise, the outer heat transfer plate may fail in an area of the port hole/s.
GB 2275996 discloses a heat exchanger comprising modules of plates being welded together in pairs. The modules are clamped together between two covers. Sealing and/or spacing rings are arranged between the modules and form part of feed pipes for heat exchange fluid. By forming part of the feed pipes and thus, being arranged in line with holes in plates, the sealing and/or spacing rings support the plates around the holes. The plates may thus be made from relatively thin sheet material, approximately <0.5 mm.