The radius of curvature can be divided into long radius elbows and short radius elbows.

The long radius elbow refers to its radius of curvature equal to 1.5 times the outer diameter of the tube, ie r = 1.5d. A short-radius elbow means that its radius of curvature is equal to the outer diameter of the tube, ie r=d. Where d is the elbow diameter and r is the radius of curvature.

According to the pressure rating, there are about seventeen types, which are the same as the American pipe standard. There are: sch5s, sch10s, sch10, sch20, sch30, sch40s, std, sch40, sch60, sch80s, xs; sch80, sch100, Sch120, sch140, sch160, xxs, the two most commonly used are std and xs. Divided by elbows, there are 45o elbows, 90o elbows and 180o elbows. As a result, there are many types of elbows. When ordering, orders often take the following expressions: for example, lr std 90o 8, indicating the long radius, pressure rating of std, and 90o of 8 elbow; another example, sr xs 45o 4 means short Radius, pressure level xs, 45o 4 elbow. The above is the approximate classification of the elbow.

Three links, there are generally two. The diameter of the three ports is equal to the diameter of the three links, the two ends of the same diameter, but the diameter of the confluent end and the other two diameters are called different diameter three links. The indication method is as follows: For equal-diameter three-way, for example t3 three-way, it means that the outer diameter is 3-inch equal-diameter three-way. For reducing tee, for example, t4 × 4 × 3.5 represents a three-diameter tee with a diameter of 3.5 inches and a diameter of four inches. Both the pressure rating and the elbow pressure rating are the same, and the specification range is the same.

The size of the head is also this division. The size of the head is represented by the diameter of the head multiplied by the diameter of the head, for example, 8×6 means that the diameter of the head is 8 inches, and the diameter of the head is 6 inches.