TST256 is an AS568-256 white PTFE (Teflon) 55 Shore D Back-Up Ring with an inside diameter of 5.734 in (145.64 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 6.012 in (152.7 mm). In service, this back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.
The compound resists oxidizing media, solvents, and steam. That behavior comes from the compound itself: PTFE (Teflon) is valued for one of the lowest coefficients of friction of any solid and near-universal chemical inertness. The material carries a published service range of -65°F (-53.9°C) to 500°F (260°C). It is not the right choice where molten alkali metals or service requiring elastic recovery are present.
It sees regular use in food and beverage, laboratory equipment, and semiconductor fabrication.
Stocked as TST256 and sold individually. Nominal inside diameter is listed as 5 3/4 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation.
Description 2103-256 PTFE S/T BUP FDA
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 5.734 inch (145.64 mm)
Actual Outside Diameter 6.012 inch (152.7 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings