Types of Elbow according to fitting method:
The easiest way to connect the elbow and pipe is to do welding directly to the elbow ends with pipe ends, where we called butt to butt weld (BW Elbow, as showed in above
picture). Butt weld elbow mainly used in a higher pressure and temperature than the other connection types of elbow. (Than socket weld elbow or the threaded piping elbow)
Socket weld elbow also connected with ends welding, different with BW elbow is: Socket weld elbow ends has a ladder shaped area, which we can insert the pipe ends to this
area (SW elbow ladder diameter fit with pipe outer diameter), after inserting do the welding work to joint them together.
Similar shape with SW elbow, different is ladder area inner surface has been machined to threads, it makes more easy to install and un-install. Which is good for the pipeline repair and maintenance.
Also known as decreasing elbow, is a kind of pipe which applied when both the elbow and closures are different in size. It’s often used so that different sizes of the pipes could be easily distinguished in order to make noteworthy turns.
Material for Elbow:
Stainless steel elbow : Material in stainless (Added Cr and Ni chemicals in carbon steel), standards and grades commonly in ASTM A403 WP 304/304L, 316/316L, ASTM A270 etc. It has higher strength and higher corrosion-resistances than carbon steel elbow.
Material in carbon steel, referred standards as
ASTM 234 WPB and WPC
ASTM A420 WPL6
MSS-SP-75 WPHY 42, 46, 52, 56, 60, 65 and 70