8-250 BLACK BUNA 90D BACK-UP RING

APG stocks the HB90250, an AS568-250 black Buna-N (Nitrile) 90 Shore A Back-Up Ring measuring an inside diameter of 4.984 in (126.59 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 5.262 in (133.65 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.

Buna-N (Nitrile) is specified here for economical choice for high-volume maintenance programs and most widely specified general-purpose sealing elastomer. Expect good resistance to many alcohols, hydraulic fluids, and greases and lubricants. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). Applications involving ketones or automotive brake fluid call for a different compound.

Typical settings include construction equipment, agricultural equipment, and automotive.

Reference part number HB90250 when ordering; the item is sold individually. Unit weight is approximately 1.8267 g and nominal inside diameter is listed as 5 inch. Check the compound against your process media, pressure and temperature before committing to a design. Not finding the exact configuration you need? APG cross-references from prints, samples and competitor part numbers.