Flat welding flange is a pipe flange commonly used for pipeline connection, also called ordinary flat welding flange or flat flange for short. It usually consists of two flanges, some bolts and gaskets. By connecting the two flanges tightly with bolts and gaskets, the connection and sealing of pipelines, pumps,
valves, instruments and other equipment can be achieved.
Flat welding flange refers to a flange connected to a container or pipeline with a fillet weld. It is an arbitrary type of flange. When designed, it is divided into an integral flange or a loose flange according to the completeness of the connection between the flange ring and the straight section. Flange rings are available in two types: with neck and without neck. Compared with the necked butt welding flange, the flat welding flange has a simple structure, saves materials, has low cost and is easy to install, but its rigidity and sealing are not as good as the necked butt welding flange. Flat welding flanges are widely used in the connection and equipment manufacturing of medium and low pressure containers and pipelines.
Sealing principle of flat welding flange
The two sealing surfaces of the bolt squeeze the flange gasket to form a seal, but this will also damage the seal. In order to maintain the seal, it is necessary to maintain a huge bolt force, so the bolts should be made larger. Larger bolts need to be matched with larger nuts, that is, bolts with larger diameters need to tighten the nuts. But it is not the case that the larger the bolt diameter, the better, because the larger the bolt diameter, the more suitable the flange will bend, which will only increase the wall thickness of the flange part. The entire equipment requires a large size and weight, which has become a special problem in construction, because in this case, weight has always been the main concern. In addition, the flat welding flange is a failure seal, requiring 50% of the bolt load to squeeze the gasket and 50% of the load to maintain pressure.
Specifications of flat welding flange:
Product specifications: DN10-DN2000
Use pressure: PN0.25MPa, PN0.6MPa, PN1.0MPa, PN1.6MPa, PN2.5MPa, PN4.0MPa
The following is a table of common specifications for flat welding flanges:
Flange Specification
|
Flange Diameter (mm)
|
Flange Thickness (mm)
|
Number of Bolt Holes
|
Bolt Hole Diameter (mm)
|
Applicable Scenario
|
DN15
|
15
|
15
|
4
|
14
|
Small flow, low-pressure systems
|
DN40
|
40
|
20
|
4
|
18
|
Medium flow, medium-pressure systems
|
DN80
|
80
|
24
|
8
|
18
|
Large flow, high-pressure systems
|
Production process:
It is divided into pure material forging, rough material forging (secondary) suitable for flat welding and butt welding flanges, steel plates suitable for flat welding flanges, centrifugal casting and casting flanges.
Main features of flat welding flanges:
1. Flat welding flanges are usually suitable for low-pressure, low-temperature, small-diameter pipes.
2. It is simple to connect and easy to operate, does not require complicated operations such as adding gaskets and flange insertion, and is easy to maintain.
3. The manufacturing and assembly costs of flat welding flanges are low and the scope of application is wide.
4. The sealing effect of flat welding flanges is generally good, and it is suitable for some occasions where the sealing performance requirements are not too high.
Flat welding flanges are not allowed to be directly welded with pipe
fittings such as tees and pipe elbows, and straight pipe sections are required.
What is the difference between flat welding flanges and butt welding flanges?
1. The scope of application of butt welding flanges and welding flanges is different. Flat welding flanges are widely used to connect carbon steel pipelines with a pressure of less than 2.5 MPa. Lubricated flat welding flanges are widely used, mostly under mild medium conditions, such as low-pressure circulating water pipes. Butt welding flanges are suitable for high-pressure and high-temperature pipelines or high-pressure and low-temperature
pipelines, and can also be used to transport some expensive flammable and explosive media. Because the sealing performance of butt welding flanges is particularly good, it is not easy to deform, can withstand greater pressure, and the pressure range can be accepted within 16MPa.
2. The welding methods of flat welding flanges and butt welding flanges are different. Flat welding flanges only need to weld one side between them, and do not need to weld the internal joint between the pipe and the flange, while butt welding flanges need to be welded on both sides, so welding flanges reduce the occurrence of stress concentration.
3. The quotation of flat welding flange is different from that of butt welding flange, because the manufacturing process of flat welding flange is relatively simple and the quotation is relatively cheap.