568-309 BUNA 70 SQUARE CUT RINGS

This square-cut ring is supplied in AS568-309 black Buna-N (Nitrile) 70 Shore A supplied with an inside diameter of 0.412 in (10.46 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 0.832 in (21.13 mm), catalogued under part number SH70309. It resists the spiral failure that affects round rings on long reciprocating strokes.

The compound resists many alcohols, water, and propane and butane. That behavior comes from the compound itself: Buna-N (Nitrile) is widely chosen for an economical choice for high-volume maintenance programs 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). It should not be specified for service in ketones or automotive brake fluid. The profile itself contributes simple lathe-cut manufacture at low tooling cost and a flat contact band that spreads sealing load across a wider area. Note that a square section is less suited to high-speed rotary service, where the larger contact area raises friction and heat.

You will find this material specified across agricultural equipment, construction equipment, and general industrial maintenance.

This item is sold individually under part number SH70309. Nominal inside diameter is listed as 7/16 inch. Check the compound against your process media, pressure and temperature before committing to a design.