The elbow is a tube that changes the direction of the pipe. Bend pipes can be seen in crossing, turning, and passing beams.

The bending pipe has the advantages of good flexibility, high pressure resistance and small resistance. Therefore, it is often used in construction.

The main forms of pipe bending are: various angles of elbow, U-shaped pipe, back and forth bending (or called B-shaped bending) and arc bending.

The elbow is a tube with an arbitrary bending angle, which is used at the turning point of the pipe. The bending radius of the elbow is expressed in R. When R is larger, the bending part of the pipe is larger and the bending part is smoother; when R is smaller, the bending part of the pipe is smaller and the bending is more rapid.

The roundabout is a pipe with two bending angles (usually 135 degrees). The distance between the ends of the bent ends of the bent pipes is called the height of the round-trip, which is indicated by the letter H. The vertical branch pipe of indoor heating is connected with the main pipe and the radiator. When the pipe is connected with the junction on the different plane, it is generally necessary to bend back and forth.

The U tube is a semi circular tube. The distance between the ends of the tube is D, which is equal to two times the bending radius R. The U tube can replace two 90 degree elbows, and is often used to connect two round fin radiator with upper and lower configurations.