8-225 BLACK FKM 90D BACK-UP RING

APG stocks the VBU90225, an AS568-225 black Viton® (FKM) 90 Shore A Back-Up Ring with an inside diameter of 1.859 in (47.22 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 2.137 in (54.28 mm). A back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

Expect good resistance to many acids, aggressive chemicals, and aromatic hydrocarbons. That behavior comes from the compound itself: Viton® (FKM) offers the industry benchmark where nitrile reaches its thermal limit, excellent resistance to compression set and permeation. Rated temperature range runs from -15°F (-26.1°C) to 400°F (204.4°C) in continuous service. It is not the right choice where low-molecular-weight organic acids or ketones and esters are present.

Typical settings include chemical processing, automotive fuel systems, and semiconductor equipment.

Reference part number VBU90225 when ordering; the item is sold individually. Unit weight is approximately 0.9426 g. Check the compound against your process media, pressure and temperature before committing to a design. APG can cross-reference from an existing part number, a drawing or a physical sample if this size is not an exact match.