This back-up ring is supplied in AS568-239 white PTFE (Teflon) 55 Shore D measuring an inside diameter of 3.609 in (91.67 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 3.887 in (98.73 mm), catalogued under part number TST239. It bridges the extrusion gap so the primary seal holds its shape under load.
PTFE (Teflon) is valued for one of the lowest coefficients of friction of any solid and excellent dielectric properties. The compound resists strong acids and bases, solvents, and steam. Service temperature is rated from -65°F (-53.9°C) through 500°F (260°C).
It sees regular use in chemical processing, semiconductor fabrication, and pharmaceutical and biotech.
Stocked as TST239 and sold individually. Nominal inside diameter is listed as 3 5/8 inch. Check the compound against your process media, pressure and temperature before committing to a design.
Description 2103-239 PTFE S/T BUP FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 3.609 inch (91.67 mm)
Actual Outside Diameter 3.887 inch (98.73 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings