How are galvanized round pipes connected?

Galvanized steel pipes used for domestic water supply shall be connected with threads, also known as threaded connections.

Generally, water supply pipelines with a nominal diameter not exceeding 100 millimeters and a nominal pressure not exceeding 1 megapascal can be connected using threaded connections. The thread connecting the pipeline is also similar to the pipe joint, divided into two types: conical and cylindrical.

If a general pipeline is manually fitted, it usually has a conical pipe thread as shown in Figure 16. The working length of the thread. It is the length from the pipe end to the base surface, and L3 is the length of the thread tail. The base surface is a specified cross-section in which the diameter (outer diameter, middle diameter, inner diameter) of a conical pipe thread is equal to the diameter of a cylindrical pipe thread of the same specification. The inclination angle of the conical pipe thread is 4=1 ° 47 ′ 24 ″, the conicity is 1:16, and the tooth profile angle is 55 °. The pitch and other technical requirements for cylindrical pipe threads are the same as those for conical pipe threads. 

The pipe thread can be made by threading the pipe hinge plate, or it can be machined by lathe. 

There are several different ways to connect pipe threads. Insert cylindrical internal thread into cylindrical external thread; Cylindrical internal thread is threaded into conical external thread, and conical internal thread is threaded into conical external thread. The latter two methods can achieve tighter connections, so they are also the most commonly used connection methods. 

When connecting pipes with threads, appropriate packing should be added between the external threads of the pipes and the internal threads of the fittings. The commonly used fillers are oil hemp root and white thick paint. The specific method is to wrap a thin and uniform layer of oil hemp root along the direction of the thread on the (external) thread of the sweat tube, then apply a thick white paint on the surface of the hemp root, and then screw on the connecting piece. It must be noted that when using hemp root white thick paint, it should be avoided from entering the tube to prevent blockage. 

After fastening the connectors, in order to make the interface clean and beautiful, excess oil hemp roots and white paint should be eliminated and wiped clean. 

The use of oil hemp roots and white thick paint does not only serve to seal the medium. It also plays a role in rust prevention for the processed pipe threads.