Specifications of Steel Pipe Fittings

The specifications of the pipe fittings mainly involve the diameters and the thicknesses of the tubes’ walls.

The nominal dimension or the nominal diameter (the symbol of the metric unit is DN, which is followed by the value in millimeters) is mainly used to indicate the diameter of the pipe fitting. The nominal dimension is a common mark for the pipe’ diameter. In addition, we can also use the outer diameter and the inner diameter in the millimeter to show the nominal dimension.

There are many ways can be used to indicate thicknesses of tubes’ walls, such as SCH schedule (SCH, followed by values), standard wall thickness (STD), thickened wall thickness (XS), super thickened wall thickness (XXS), nominal pressure (PN), etc., or the wall thickness can be indicated in the millimeter.
   
At present, in the standard of the common nominal dimension, the range of the nominal dimension is between DN6 and DN2000.

Manufacturing technologies of steel pipe fittings

Introduction to manufacturing technology
Manufacturing technologies of steel pipe fittings are mainly pressure processing technologies, coupled with, welding, heat treatment, cutting, nondestructive testing, surface treatment, etc. The pressure processing process is also the forming process of the pipe fitting, which is completed mainly based on the plastic deformation feature of the metal material. The pressure processing process can be roughly divided into the hot working process and the cold working process; these two processes can be also divided into different pressure processing technologies. The common techniques and application examples of pressure processing are are as the following. 
 

Pressure processing modes  Pressure processing technology Application examples 
Hot working processes Expanding  hot pushing It is mainly used to manufacture the carbon steel elbow and the alloy steel elbow.
Heat pressing  It is mainly used to manufacture pipe tees, elbows with thick walls and pipe caps which are greater than DN300.
Reducing or expanding hot pressing It is mainly used to manufacture the reducer.
Hot rolling It is mainly used to manufacture reducers with thick walls.
Hot bending  It is mainly used to make pipe bends.
Hot forging/hot stamping  It is mainly used to manufacture forged socket welded steel pipe fittings fittings and threaded pipe fittings.
Cold working  processes Cold pushing It is mainly used to manufacture the stainless steel elbow. 

The pressure processing of the pipe fitting made of a certain material depends on its material’s characteristic, equipment and manufacturing cost. The carbon steel elbow with the common specification usually adopts the expanding hot pushing technology. The low carbon steel material still has rigidity and good toughness after being heated to a certain temperature; low carbon steel elbows have fewer defects during expending processes, resulting in high rates of finished elbow products. The carbon steel elbow can be manufactured in a continuous manner with hot pushing technology, which is not only suitable for mass-producing the carbon steel elbow, but also can avoid having the subsequent heat treatment process and reduce energy consumption and cost. If we adopt hot pushing technologies for stainless steel elbows with thick walls, requirements of core rods’ materials will be very high due to high hot strength of stainless steel materials; the operation temperature of the common sensor device is generally lower than the forming temperature, and therefore, we often adopt the hot expressing process.

Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry (www.steeljrv.com)

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