Materials used to manufacture mechanical seals have linear coefficients of expansion from approximately 2.2 · 10^-6K^-1 (1.3912) to approximately 500 · 10^-6K^-1 (PTFE). For individual values materials for ... . When designing narrow gaps (e.g. between the metal shaft and ceramic seal face or stationary seat) and shrink connections, it is necessary to know not only the coefficients of expansion of the materials used but also the minimum and maximum temperatures arising in operation and at standstill.