Pipe fittings include elbow, tee, cross, reducer, expansion joint, valve, flange, gasket, bolt, nut, instrument element, etc. Everything in a pipe run is called a pipe fitting (pipe component), with the exception of pipes. It should be said that the components on the pipeline other than the pipeline can be called fittings, which is a reasonable statement. So for the pipe specialty, the common pipe fittings are mainly tee, cross, elbow, big and small head, official cap, pipe joint, movable joint, pipe platform, etc. It can be seen as a conventional understanding of our industry. Flange, flange, gasket and bolt can be classified as pipe fittings, but the pressure gauge nozzle is an instrument component, which is counted by the instrument discipline and installed by the process pipeline.
2. In a broad sense, if the pipe component is considered to be a pipe fitting, the flange is a pipe fitting. However, the pipe fittings mentioned in each link of project management usually do not include flange. The complete pipeline (excluding anti-corrosion and heat preservation) consists of pipeline (pipe), pipe fitting, flange, fastener, valve and instrument element. The pipeline only refers to the pipeline installed on site (if the pipeline with the finished parts is not within the scope of the pipeline, such as the straight pipe section with the flow orifice plate); the pipe fittings refer to the tee, elbow, boss, nozzle, filter, special parts, etc.; the instrument elements only refer to the instrument, such as the pressure gauge, thermometer, etc. There are also clear classifications in the budget quota.
III. according to the flange standard, the flange does not belong to pipe fittings. It is called flange joint together with gasket and fastener. From the definition of the specification, the flange is not a pipe fitting, but a pipe component or a pipe component. Explanation of terms in gb20801-2006 code for pressure pipes: industrial pipes: pipe fittings include elbows, tees, reducers, flanged short joints, pipe caps and unions. Tsg2009 pressure pipeline safety supervision regulation specifies that pressure pipeline components include pipeline components and pipeline supports. Both gb50235 and gb20801 have notes on the explanation of terms: pipeline components include the flange and valve connecting the pipeline.