A tolerance ring’s unique wave properties provide a secure grip for holding bushings (i.e., bronze, Igus®) and sleeves both firmly and gently in place. Torque and axial retention requirements are met while cushioning them from thermally induced stresses from adjacent components.
Typically tolerance rings are made of 301 stainless steel (SST) for basic corrosion resistance. SST tolerance rings can handle a large range of operating temperatures from -100 °F/-73 °C to 450 °F/232 °C. With higher temperatures (˃ 450 °F/232 °C) or more corrosive applications, the rings are made from Hastelloy C276 or Monel K-500.
Chemical pumps such as magnetic drive seal-less pumps often employ silicon carbide [SiC] bushings and journals. The SiC components have a very low coefficient of thermal expansion compared to the typical steel or alloy based mating housings or shafts. SiC materials are also brittle and can fracture if exposed to the high forces of press fits or excessive stresses due to differential thermal expansion/contraction.
Mounting these fragile ceramic sliding bearings can be a challenge. Using O-rings often results in premature pump failure due to the softening or brittlizing of the O-ring materials from the extreme operational temperatures.
A variety of tolerance ring configurations can be made for accommodating design constraints. Providing a spring rate strong enough to hold over the extremes of tolerance and temperature, yet soft enough to prevent damage to relatively brittle or delicate materials is done by balancing a ring’s parameters.