257 PTFE SOLID BACKUP RING FDA

The TST257SO is an AS568-257 white PTFE (Teflon) 55 Shore D Back-Up Ring with an inside diameter of 5.859 in (148.82 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.137 in (155.88 mm). This back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

As a material, PTFE (Teflon) is widely chosen for near-universal chemical inertness and excellent dielectric properties. The compound resists steam, strong acids and bases, and nearly all industrial chemicals. Published continuous service range is -65°F (-53.9°C) to 500°F (260°C). It is not the right choice where elemental fluorine at temperature or molten alkali metals are present.

Typical settings include aggressive-media pipelines, laboratory equipment, and semiconductor fabrication.

TST257SO ships individually. Nominal inside diameter is listed as 5 7/8 inch. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing.