"ANSI Class" Ratings of Pipe Flanges
"ANSI class" is the designation for pressure-temperature ratings of pipe flanges. In its denotation, the word Class is followed a by dimensionless number. This includes Class 150, 300, 400, 600, 900, 1500, and 2500. Unsurprisingly, the phrase ANSI class, does, in fact, derive from the American National Standards Institute.