what is a backing flange
SK-39-SO and SK-39-PSO Backing Flanges. â  An economical light-weight backing ï¬ ange for use with slip-on type stub ends. â  Tapered face on the ï¬ ange improves visibility during gasket alignment. â  Cast in commercial quality steel or machined from ASTM A 36 plate. â  Cast or drilled hole patterns per ANSI B16.1, Class 125 (identical to ANSI B16.5, Class 150). â  Coated with red oxide primer. Galvanized, epoxy and other coatings are also available.