Ordered as TST248SO, this is an AS568-248 white PTFE (Teflon) 55 Shore D Back-Up Ring built to an inside diameter of 4.734 in (120.24 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 5.012 in (127.3 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.
As a material, PTFE (Teflon) delivers a very wide continuous service temperature range and one of the lowest coefficients of friction of any solid. Expect good resistance to solvents, steam, and nearly all industrial chemicals. Rated temperature range runs from -65°F (-53.9°C) to 500°F (260°C) in continuous service. It should not be specified for service in elemental fluorine at temperature or molten alkali metals.
It sees regular use in aggressive-media pipelines, semiconductor fabrication, and pharmaceutical and biotech.
TST248SO ships individually. Review your operating media and conditions against this specification before installation. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.
Description 248 PTFE SOLID BACKUP RING FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 4.734 inch (120.24 mm)
Actual Outside Diameter 5.012 inch (127.3 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings