Manifestation of Differential Thermal Expansion in Teflon Guide Bushes/Pads

The design of guide bushes or pads is generally straightforward and can be done using basic mechanical engineering principles. However, the two case studies presented in this paper emphasize the need for the detailed stress analysis to supplement the basic design methodology for the design of Teflon guide bushes / pads located in steel housing, operating at high temperatures (> 100 °C). The two case studies highlight the two diverse manifestations of differential thermal expansion between the Teflon and steel housing; in one case the Teflon guide bush jammed to the central shaft while Teflon pads got loosened from their housing in the other case. The seemingly counter-intuitive observations were understood by numerical analysis, supported by carefully planned experiments. Design solutions to preclude the abnormalities were proposed and numerically analyzed. The main significance of the current work is that it provides certain guidance for designing guide bush/pad made of dissimilar materials.