8-139 BLACK BUNA 90D BACK-UP RING

Part number HB90139 is an AS568-139 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 2.175 in (55.25 mm), a cross section of 0.103 in (2.62 mm), and an outside diameter of 2.381 in (60.48 mm). A back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

Expect good resistance to greases and lubricants, petroleum-based oils, and many alcohols. That behavior comes from the compound itself: Buna-N (Nitrile) offers low compression set under sustained load and the most widely specified general-purpose sealing elastomer. Continuous operating temperature is published at -40°F (-40°C) to 250°F (121.1°C). Applications involving ozone and direct sunlight or polar solvents call for a different compound.

Common environments for this compound include hydraulic and pneumatic systems, agricultural equipment, and automotive.

Order part number HB90139, sold individually. Unit weight is approximately 0.645 g. Application requirements vary, so validate compatibility with your process conditions prior to installation. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.