8-391 BLACK FKM 90D BACK-UP RING

VBU90391 is an AS568-391 black Viton® (FKM) 90 Shore A Back-Up Ring measuring an inside diameter of 21.953 in (557.61 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 22.373 in (568.27 mm). In service, this back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.

As a material, Viton® (FKM) delivers excellent resistance to compression set and permeation, the industry benchmark where nitrile reaches its thermal limit. This material stands up to aromatic hydrocarbons, many acids, and engine and transmission fluids. Service temperature is rated from -15°F (-26.1°C) through 400°F (204.4°C).

It sees regular use in oil and gas, automotive fuel systems, and high-temperature process equipment.

Order part number VBU90391, sold individually. Nominal inside diameter is listed as 22 inch. Application requirements vary, so validate compatibility with your process conditions prior to installation. APG can cross-reference from an existing part number, a drawing or a physical sample if this size is not an exact match.