8-137 BLACK BUNA 90D BACK-UP RING

HB90137 is an AS568-137 black Buna-N (Nitrile) 90 Shore A Back-Up Ring measuring an inside diameter of 2.05 in (52.07 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 2.256 in (57.3 mm). In service, this back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

Expect good resistance to petroleum-based oils, greases and lubricants, and water. That behavior comes from the compound itself: Buna-N (Nitrile) is widely chosen for low compression set under sustained load, strong abrasion and tear resistance. Service temperature is rated from -40°F (-40°C) through 250°F (121.1°C). Applications involving ketones or strong acids call for a different compound.

Maintenance and OEM teams specify it across construction equipment, agricultural equipment, and hydraulic and pneumatic systems.

Reference part number HB90137 when ordering; the item is sold individually. Unit weight is approximately 0.618 g and nominal inside diameter is listed as 2 1/16 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.