APG stocks the TST251SO, an AS568-251 white PTFE (Teflon) 55 Shore D Back-Up Ring 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). A back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.
PTFE (Teflon) is widely chosen for a very wide continuous service temperature range and non-stick, non-contaminating surface characteristics. The compound resists strong acids and bases, oxidizing media, and solvents. Service temperature is rated from -65°F (-53.9°C) through 500°F (260°C). Exposure to elemental fluorine at temperature or molten alkali metals will shorten service life.
You will find this material specified across aggressive-media pipelines, laboratory equipment, and pharmaceutical and biotech.
Stocked as TST251SO and sold individually. Check the compound against your process media, pressure and temperature before committing to a design.
Description 251 PTFE SOLID BACKUP RING FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 5.109 inch (129.77 mm)
Actual Outside Diameter 5.387 inch (136.83 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings