Ordered as TSP138, this is an AS568-138 white PTFE (Teflon) 55 Shore D Back-Up Ring measuring an inside diameter of 2.112 in (53.64 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 2.318 in (58.88 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.
It resists solvents, steam, and strong acids and bases. That behavior comes from the compound itself: PTFE (Teflon) is specified for a very wide continuous service temperature range and near-universal chemical inertness. Published continuous service range is -65°F (-53.9°C) to 500°F (260°C). Verify compatibility before use with elemental fluorine at temperature or service requiring elastic recovery.
Common environments for this compound include food and beverage, chemical processing, and semiconductor fabrication.
This item is sold individually under part number TSP138. Confirm chemical compatibility, pressure and temperature against your own application requirements before installing. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.
Description **2107-138 PTFE SPIRAL B/U FDA
Actual Cross Section 0.103 inch (2.62 mm)
Actual Inside Diameter 2.112 inch (53.64 mm)
Actual Outside Diameter 2.318 inch (58.88 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings