The function of an elbow is to change direction of flow in a piping system. Elbows are split into three groups, which define the distance over which they change direction, which is expressed as a function of the distance from the centre line of one end to the opposite face. This is known as the centre to face distance and is equivalent to the radius through which is the elbow is bent.
90 degree elbow, also called "90 bends or 90 elbows", are manufactured as SR (Short Radius) elbows and LR (Long Radius) elbows. SR (Short Radius) elbows have a Center-to-Face dimension of 1.0 X diameter and are typically used in tight areas where clearances are an issue. LR (Long Radius) elbows have a Center-to-Face dimension of 1.5 X diameter and are the more common type and used when space is available and flow is more critical.
| Stainless steel elbow | : | ASTM A403 WP Gr. 304, 304H, 309, 310, 316, 316L, 317L, 321, 347, 904L |
| Alloy steel elbow | : | ASTM / ASME A/SA 234 Gr. WP 1, WP 5, WP 9, WP 11, WP 12, WP 22, WP 91 |
| Low temperature carbon steel elbow | : | ASTM A420 WPL3 / A420WPL6 |
| Carbon steel elbow | : | ASTM A 234 WPB, WPBW, WPHY 42, WPHY 46, WPHY 52, WPH 60, WPHY 65 & WPHY 70 |
| Duplex steel elbow | : | ASTM A 815 UNS NO S 31803, S 32205 |
