APG stocks the TSP249, an AS568-249 white PTFE (Teflon) 55 Shore D Back-Up Ring built to an inside diameter of 4.859 in (123.42 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 5.137 in (130.48 mm). A 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 near-universal chemical inertness. It resists strong acids and bases, nearly all industrial chemicals, and steam. Rated temperature range runs from -65°F (-53.9°C) to 500°F (260°C) in continuous service. Verify compatibility before use with molten alkali metals or elemental fluorine at temperature.
Common environments for this compound include aggressive-media pipelines, laboratory equipment, and semiconductor fabrication.
Order part number TSP249, sold individually. Nominal inside diameter is listed as 4 7/8 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation.
Description **2107-249 PTFE SPIRAL B/U FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 4.859 inch (123.42 mm)
Actual Outside Diameter 5.137 inch (130.48 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings