Butt-weld fittings: elbows, tees, reducers

ASME B16.9 fittings are ordered by NPS, wall schedule and material, for example: "Elbow 90° LR, 6" Sch 40, ASTM A234 WPB, ASME B16.9".

Long radius (LR) elbows have a centre-line radius of 1.5 × NPS and are the default. Short radius (SR) elbows (1.0 × NPS) save space but increase pressure drop.

Reducers are concentric (same centre line) or eccentric (one flat side). Eccentric reducers are used on pump suctions with the flat side on top to avoid air pockets.

Tees are equal or reducing; a reducing tee is specified run × run × branch, e.g. 8" × 8" × 4".