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General Knowledge of Pipe Fittings

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In general, apart from straight pipes, all accessories applied to a pipeline system are collectively known as pipe fittings. Nevertheless, we often refer to elbows, tees, reducers, caps and other varied joints as pipe fittings. At the same time, products like flanges, valves, expansion joints, piping supports are not listed in the same category. 
This paper will mainly discuss the common issues of those fittings that we usually mentioned. 


According to different welding methods, fittings can be sorted into two broad types: 
Socket Welded and Threaded Type; 
Butt Welded Type, including elbows, tees, reducers, caps and various joints. (Joints here range over unions, couplings, busing, plugs and so on. )

According to the existence of seam on surface of fittings, tube fittings fall into two classes: seamed fittings and seamless fittings. 

2. Identifications. 

Pipe Identifications are parameters that people use to grasp the special features of pipe fittings. Generally Speaking, five aspects should be noticed. 
1.Categories (Degrees and radius are needed for elbows, while reducers should be marked with concentric or eccentric type). 
3.Sizes and measuring systems (Metric System or British System). 
4.Wall thicknesses. 

5.Standard numbers (Standard numbers ended with A or B mean that the pipe system is recorded on base of British System or Metric System respectively). 

3. Standards. 

In China, there are generally four standards that used in pipe fittings manufacture. 
A.Chinese national standard GB12459-90 for seamless butt-welded fittings. 
B.Chinese national standard GB/T13401-92 for seamed welding fittings. 
C.ANSI B16.9 for welded fittings (seamless or seamed). 
D.ANSI B16.11 for socket welded or threaded fittings. 

In some cases, Chinese manufacturers also use HG514-87 (a standard enacted by Ministry of Chemical Industry) and SHJ408-90 (a standard formulated by Sinopec). Of course, Japaneses Industrial Standards (JIS) and Deutsches Institut für Normung (DIN) are also frequently used. 

4. Code Names. 

The following are code names for some pipe fitting terms. 
CategoryCode NameFull Name
GeneralCS Carbon  Steel
SS Stainless Steel
BW Butt Welding
SWSocket Welding
NPTNormal Pipe Thread
NPTF NPT  Female 
SQ Square 
HEXHexagon / Hex
Pipe FittingE (S)Elbow (s)
E (L)Elbow (l)
RCConcentric Reducer / Conc. Reducer
REEccentric Reducer / Ecc. Reducer 
TRTee (R)
TC Tee (C)
Union Union 
Half Coupling Half Coupling 




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