2103-251 PTFE S/T BUP FDA

This back-up ring is supplied in AS568-251 white PTFE (Teflon) 55 Shore D with an inside diameter of 5.109 in (129.77 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 5.387 in (136.83 mm), catalogued under part number TST251. It allows a standard o-ring to operate at higher pressures than it could unsupported.

The compound resists strong acids and bases, solvents, and nearly all industrial chemicals. That behavior comes from the compound itself: PTFE (Teflon) is valued for a very wide continuous service temperature range and one of the lowest coefficients of friction of any solid. Service temperature is rated from -65°F (-53.9°C) through 500°F (260°C). It is not the right choice where molten alkali metals or elemental fluorine at temperature are present.

You will find this material specified across food and beverage, pharmaceutical and biotech, and semiconductor fabrication.

Stocked as TST251 and sold individually. Nominal inside diameter is listed as 5 1/8 inch. Check the compound against your process media, pressure and temperature before committing to a design. For a size or compound outside the standard catalog, APG can quote from a print or sample.