1.1 operating Pressures and Temperatures 2The exchanger in operation must withstand the stresses produced by the operating pressure and the temperature differences between two fluids. These stresses depend on the inlet pressures and temperatures of the two fluids. The most versatile exchan- gers for a broad range of operating pressures and temperatures are shell-and-tube exchangers for medium- to high-heat duties and double-pipe exchangers for lower heat duties. They can handle from high vacuum to ultrahigh fluid pressures lgener ally limited to 30 MPa (4350 psi) on the shell or annulus side and 140 MPa (20.000 psi) on the tube side Coupled with high pressures, shell-and-tube exchangers can withstand high tenmperatures, limited only by the materials used: however, the inlet temperature difference is limited to 50 C (120 F) from the thermal expansion point of view when the exchanger design allows only limited thermal expansion, such as in the E-shell design. These exchangers are used for gas, liquid, and phase-change applications.