A spiral heat exchanger is composed of two long, flat plates wrapped around a mandrel or center tube, creating two concentric spiral channels (figure 1). The channels are seal-welded on alternate sides to provide a sturdy barrier between the fluids. A cover is fitted on each side, and a full-faced gasket is positioned between each cover and spiral element to prevent fluid bypassing and leakage to the atmosphere. Access to the hot and cold heat transfer surfaces is gained by removing the respective covers. Connections are installed in the center of each cover and on the peripheral pockets.