The above figure gives the general situation of flange classification. Let’s take a detailed look at various types of flanges.
According to the degree of overall properties:
(1) Integral flange
1． Flat welding flange The flange is welded to the equipment cylinder or pipe. It is easy to manufacture and widely used, but has poor rigidity. After the flange is stressed, the rectangular section of the flange plate rotates slightly, as shown in the figure below, and the cylinder wall or pipe wall connected to the flange bends and deforms. As a result, additional cnc bending stress will occur on the section of the cylinder wall near the flange. Therefore, the applicable pressure range of flat welding flange is lower (PN<4.0MPa). 2． Butt welding flange Butt welding flange is also called high neck flange or long neck flange. The existence of the neck increases the rigidity of the flange, and at the same time, because the root thickness of the neck is thicker than the barrel, the bending stress at the root is reduced. In addition, the connection between the flange and the cylinder (or pipe wall) is a butt weld, which is stronger than the fillet weld of the flat welding flange. Therefore, the butt welding flange is suitable for occasions with higher pressure and temperature or larger equipment diameter. .
(2) Loose flange
The characteristic of loose flange is that the flange cannot be effectively connected to the container or pipe as a whole, and does not have the same strength as the integral connection, as shown in the figure above. Since the flange can be made of different materials than the equipment or pipes, this flange is suitable for equipment or pipes made of copper, aluminum, ceramics, graphite and other non-metallic materials. In addition, this kind of flange will not produce additional bending stress on the cylinder or pipe after being stressed, which is also one of its advantages, but it is generally only suitable for situations with low pressure.
(3) Arbitrary flange
The integrity of arbitrary flanges is between integral flanges and loose flanges, including welded flanges that are not penetrated.
Circular flanges are the most common, square flanges are conducive to compact arrangement of pipes, and oval flanges are usually used on valves and small-diameter high-pressure pipes.