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Processing Method and Manufacturing Process of Flat Welded Flange

Processing Method and Manufacturing Process of Flat Welded Flange

Flat welded flange is a kind of flange connected with fillet weld of container or pipeline. It belongs to arbitrary flange. According to the integrality degree of the connection between the flange ring and the straight cylinder section, the integral flange or the loose flange are checked separately in the design. There are two kinds of flange rings with neck and without neck. Compared with the butt-welded flange with neck, the flat-welded flange has simple structure and less material consumption, but its rigidity and sealing are not as good as the butt-welded flange with neck. Flat welded flanges are widely used in connection of medium and low pressure vessels and pipes.

Flat welded flange

Flat welded flange is often used in the case of medium temperature and pressure are not high and medium corrosion is strong. When the corrosive medium is strong. Rare integral flanges are flat welded flanges and butt welded flanges. Flanged fittings refer to fittings with flanges (flanges or joints). It can be cast. Flat welded flanges are mainly parts that connect pipes to pipes. According to the structure type. It can also be made up of threaded connection or welding. Flange connection refers to a pair of flanges, a gasket and a number of bolts and nuts.

The main design disadvantage of flat welded flange is that it can not guarantee no leakage. This is the shortcoming of its design: the connection is dynamic, and the movement between flange surfaces will be caused by thermal expansion and fluctuating periodic loads, which will affect the function of flange, thus impairing the integrity of flange and eventually leading to leakage. Any product can not be without defects, but try to control the insufficiency of the product to the minimum, so the company in the production of flat welding flange as far as possible to improve the performance of the product, so that it can play a maximum role.

Flat-welded flange features:

Flat-welded flange not only saves space and reduces weight, but also ensures that the joint does not leak, and has good sealing performance. The reason why the size of compact flange decreases is that the diameter of the seal is reduced, which will reduce the cross section of the sealing surface. Secondly, the flange gasket has been replaced by the sealing ring to ensure that the sealing face matches the sealing face. In this way, only a small amount of pressure is needed to press the cover tightly. As the required pressure decreases, the size and quantity of bolts can be reduced accordingly, so a new product with small size and light weight (70%-80% less than the weight of traditional flange) is finally designed. Therefore, flat welding flange is a relatively high quality flange product, which reduces the quality and space, and plays an important role in industrial applications.

Sealing Principle of Flat Welded Flange:

The two sealing faces of bolts extrude each other flange gasket and form a seal, but at the same time, it also leads to the destruction of the seal. In order to keep the seal, it is necessary to maintain a huge bolt force, for this reason, the bolt has to be made bigger. Larger bolts match larger nuts, which means larger diameter bolts are needed to create conditions for tightening nuts. However, the larger the diameter of the bolt, the more flexible the flange will be. The only way is to increase the wall thickness of the flange. The whole device will require a great deal of size and weight, which becomes a special problem in the offshore environment, because in this case, weight is always the main problem that people must pay attention to. Moreover, in essence, flat welded flange is an ineffective seal, which requires 50% of the bolt load to be used to extrude gaskets, while only 50% of the load to maintain pressure is left.

Flat Welded Flange Processing Technology

Cutting Flange with Steel Plate

Generally, the steel plate produced by the regular enterprise, the raw material is more regular, the small aperture is more easily processed, the tread is relatively flat, the cost is lower, and the quality is also able to.

Large caliber flange

Generally, it is made by cutting and heating the steel plate, and the raw material is not good. Only the center will have an interface to be welded. Although no weld can be seen in the future, it is still not advocated to be used in high-pressure pipelines.

Forging flange

Good raw materials, high density, high price and good quality.

Flat welded flange has certain technical requirements and parameters in production and use.

  • 1. The butt weld of the ring should be heat treated after welding and 100% X-ray or ultrasonic flaw detection. The X-ray flaw detection meets the grade II requirements of JB4730 and the ultrasonic flaw detection meets the grade I requirements of JB4730. The welding flange is manufactured and processed by certain welding standards and technologies, which meets the corresponding national production standards and requirements.
  • 2. The steel plate for flat-welded flange shall be inspected by ultrasonic wave without delamination defect to ensure good quality and performance. It shall be produced and inspected in accordance with certain quality requirements to ensure that the steel plate for production and use has no quality problems.
  • 3. The steel should be cut into strips along the rolling direction and welded into circular rings by bending and butt welding, and the surface of the steel should be made into a circular cylinder. In the production of Harbin flange, the steel plate can not be directly machined into necked flange, and a certain process is used to make and process it.

Source: China Stainless Steel Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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