8-321 BLACK FKM 90D BACK-UP RING

Ordered as VBU90321, this is an AS568-321 black Viton® (FKM) 90 Shore A Back-Up Ring supplied with an inside diameter of 1.162 in (29.51 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 1.582 in (40.18 mm). The back-up ring extends o-ring service life by supporting the seal against extrusion under high pressure.

Viton® (FKM) is specified here for industry benchmark where nitrile reaches its thermal limit, excellent resistance to compression set and permeation. Expect good resistance to engine and transmission fluids, petroleum oils and fuels, and many acids. Rated temperature range runs from -15°F (-26.1°C) to 400°F (204.4°C) in continuous service. Exposure to ketones and esters or amines will shorten service life.

Typical settings include aerospace, chemical processing, and semiconductor equipment.

Reference part number VBU90321 when ordering; the item is sold individually. Nominal inside diameter is listed as 1 3/16 inch. Check the compound against your process media, pressure and temperature before committing to a design. For a size or compound outside the standard catalog, APG can quote from a print or sample.