331 PTFE SOLID BACKUP RING FDA

TST331SO is an AS568-331 white PTFE (Teflon) 55 Shore D Back-Up Ring supplied with an inside diameter of 2.225 in (56.52 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 2.645 in (67.18 mm). In service, this back-up ring bridges the extrusion gap so the primary seal holds its shape under load.

The compound resists strong acids and bases, steam, and solvents. That behavior comes from the compound itself: PTFE (Teflon) is specified for near-universal chemical inertness and non-stick, non-contaminating surface characteristics. The material carries a published service range of -65°F (-53.9°C) to 500°F (260°C). It is not the right choice where molten alkali metals or elemental fluorine at temperature are present.

It sees regular use in semiconductor fabrication, food and beverage, and aggressive-media pipelines.

Stocked as TST331SO and sold individually. Nominal inside diameter is listed as 2 1/4 inch. Check the compound against your process media, pressure and temperature before committing to a design. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.