Ordered as TST259SO, this is an AS568-259 white PTFE (Teflon) 55 Shore D Back-Up Ring with an inside diameter of 6.234 in (158.34 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.512 in (165.4 mm). The back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.
PTFE (Teflon) is specified here for excellent dielectric properties and very wide continuous service temperature range. This material stands up to nearly all industrial chemicals, strong acids and bases, and solvents. Continuous operating temperature is published at -65°F (-53.9°C) to 500°F (260°C). Exposure to molten alkali metals or elemental fluorine at temperature will shorten service life.
It sees regular use in chemical processing, aggressive-media pipelines, and laboratory equipment.
Order part number TST259SO, sold individually. Nominal inside diameter is listed as 6 1/4 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. APG supports cross-referencing from drawings, samples and competitor numbers when a listed size is not an exact fit.
Description 259 PTFE SOLID BACKUP RING FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 6.234 inch (158.34 mm)
Actual Outside Diameter 6.512 inch (165.4 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings