SF&DS developed the spiral heat exchanger for a number of reasons. In the first place a continuous tube without blind angles has a very low probability of fouling; such a system can also be quickly and efficiently cleaned. The fact that the tubes are coiled helically also has a favourable effect on the longevity of the heat exchanger as coiled tubes are more resistant to thermal stress. The most important consideration  for the choice of a spiral coiled heat exchanger was, however, the improved heat transfer which occurs when the pipe bundle is coiled.