Elbows are used to change the direction of the pipe. The bending angles of commonly used elbows are 90 °, 45 ° and 180 °. The 180 ° elbow is also called a U-shaped elbow. There are also elbows with special angles, but the number is very few.
1. Cast iron elbow
Malleable cast iron elbow is the most common thread elbow. This kind of pipe is mainly used for heating, water and gas pipes. In the process, except for low-pressure pipelines that need to be dismantled frequently, other material pipelines are rarely used. The specifications of Marshall elbow are relatively small, and the commonly used specifications range from 1/2 to 4 inches. According to their different surface treatments, they are divided into galvanized and non-galvanized.
2. Elbow
Pressed elbow, also called stamped elbow or seamless elbow, is made of high-quality carbon steel, stainless acid-resistant steel and low-alloy steel seamless pipe in a special mold. The bending radius is one and a half times the nominal diameter (R = 1.5DN). In special occasions, an elbow with a bending radius equal to the nominal diameter (R = 1DN) can also be used. Its specification range is within DN20 ~ 600mm. Its wall thickness range is consistent with the table number of seamless steel pipe. Pressed elbows are generally stamped from standard seamless steel pipes in professional manufacturers or processing plants. When leaving the factory, the ends of the elbows should be grooved.
3. Stamping elbow
The stamping welding elbow is made by pressing a plate into a half-ring elbow through a die, and then two half-ring elbows are formed by butt welding. The bending radius is the same as the seamless pipe elbow, and the specification range is more than 200mm in nominal diameter.
4. Welding elbow
There are two kinds of production methods. One is to cut out the steel plate in the processing plant, roll and weld after cutting, and most of them are used for the matching of steel plate coils. The other is the use of pipe blanking, butt welding by group, its specifications are generally above 200mm. The use temperature cannot be greater than 200 ° C, and can generally be produced at the construction site.
5. High pressure elbow
High pressure elbow is forged from high quality carbon steel or low alloy steel. According to the pipe connection type, both ends of the elbow are processed into threads or grooves, and the processing precision is very high. It is required that the pipe thread and the flange thread can be tightly matched and freely screwed in and must not be loose. For petrochemical pipelines, commonly used specifications range from DN6 to 200mm.