The "C" type begins with the same basic core as an "A" type, the unit is all welded and has no removable heads. Both fluids need to be relatively clean. There are two separate reasons for a "C" type construction. One, it is the least costly SHE, it has all the advantages of a spiral heat exchanger, true counter flow, can handle solids, small, compact, etc, and it less costly than one with removable heads. The second reason is Elanco has developed a super strength all welded version that can handle cycling and huge temperature shock. The all welded unit is very useful for high and low temperatures where gaskets become a problem. These are applications that SHE explicitly avoided before. The "C" has been used for high temperature gas to gas, for cooling heat transfer oils with liquid nitrogen, and for heating freezing xylene with steam. So advantageous is the "C" type to temperature shock, it has replaced U-Tube S&T units that failed due to the tube bundle rotating in the shell from the thermal stress.