Notes for Pipe Fittings Used in Threaded Pipes

The threaded connection is also called as screwed connection. It is a method that connects two pipelines or a pipeline and a valve through internal and external threads. Galvanized steel pipes that used in building water supply system can only be connected with threaded means. 

 

In general, there are totally three methods for connections of galvanized steel pipes: welded connection, threaded connection and free connection (telescopic connection). In spite of fastness, welded connection is not advocated. It is inconvenient for maintenance and disassembly later. As to the free connection, it can only bear small pressures. Nevertheless, pipelines may fall off under high pressures if the ends were not fixed well. In winter, water in pipelines may turn into ice. Therefore, the inflated volume will make pipelines expand to both ends. Hence, only threaded method can be when connecting galvanized steel pipes in building water supply system. What’s more, threaded facilities, threaded fittings (for example, threaded elbows) and places that regular demolitions happen or hot work forbidden are mostly connected in this way. 

 

When employing threaded connection, workers should fill suitable matters between external threads and orifices of pipes or internal threads of valves. The padding here are used for sealing pipelines and protecting orifices. The application of padding can also make disassembly work later easier. 

 

The main installation steps for threaded connection are cut pipes, screw up, install fittings and straightening pipelines. Here we will give a detail explanation on the third process, that is, installing fittings. 

 

According to on-site sketch, threaded pipelines will be equipped with fittings in this process. 

 

When fixing pipe fittings, they should be threaded to the pipes for testing degree of tightness. In general, three screw pitches is suggested. And then, painting lead oils and winding ramie on fittings and fastening fittings with pipe tongs. Two or three screw threads should be exposed. Finally, numbering the parts and putting them at appropriate places after cleaning lead oils and ramie. It should be noticed that, the selection of pipe tongs should be based on the diameters of pipelines.