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Classification, Standards and Assembly of Flanges

Jan. 14, 2021

Flange is the abbreviation of flange. This name is a transliteration of flange. It was first proposed by an Englishman named Elchart in 1809, and also proposed the method of casting flange at the same time, but later It has not been widely used for quite a while. It was not until the beginning of the 20th century that flanges were widely used in various mechanical equipment and pipeline connections.

Classification of flanges?

1. According to chemical industry standards:

Integral flange, threaded flange, plate flat welding flange, neck butt welding flange, neck flat welding flange, socket welding flange, butt welding ring loose flange, flat welding ring loose flange, Lining flange cover, flange cover.

2. According to petrochemical industry standards:

Threaded flanges, butt welding flanges, flat welding flanges, socket welding flanges, loose flanges, flange covers.

3. According to machinery industry standards:

Integral flanges, butt welding flanges, plate flat welding flanges, butt welding ring plate loose flanges, flat welding ring plate loose flanges, flanged ring plate loose flanges, flange covers.

4. According to national standards:

Integral flanges, threaded flanges, butt welding flanges, neck flat welding flanges, neck socket welding flanges, butt welding ring neck loose flanges, plate flat welding flanges, butt welding ring plate loose sleeves Flange, flat welded ring plate loose flange, flanged ring plate loose flange, flange cover.



Flange assembly

1. Before assembling the Stainless Steel Flanges, the flange surface must be cleaned, especially the sealing surface.

2. When assembling the flat welding flange, insert the pipe end into the flange inner diameter thickness 2≤3, and then spot weld the flange to the pipe. If it is a horizontal pipe, the flange should be spot welded from above, and then use a 90° angle ruler to check and correct the flange position from different directions so that the sealing surface is perpendicular to the center line of the pipe, and then the second spot welding This point is correct.

3. Use a 90° angle ruler to check and correct the flange position from left to right. After passing the third and fourth spot welding, complete the spot welding and fixing of the flange.

4. For the assembly of flange pairs, the bolt holes of the mounting flange should be aligned with the corresponding bolt holes of the fixed flange and parallel to the fixed flange, and the deviation shall not be less than 1.5% of the outer diameter of each thousand flanges., And not more than 2mm.

5. When selecting the matching flange of the equipment or valve parts, pay attention to whether the flange of the original equipment or valve parts is consistent with the flange connection size used in the pipeline.

Flange connection

1. The flange connection should be kept on the same axis, the center deviation of the bolt hole should not exceed 5% of the hole diameter, and the bolt should be freely perforated. The flange connecting bolts should have the same specifications, the installation direction should be the same, and the bolts should be tightened symmetrically and evenly.

2. Oblique washers of different thickness should not be used to compensate for flange non-parallelism. Do not use double washers. When large-diameter gaskets need to be spliced, they should not be butted with flat ports, but should be in the form of oblique loops or labyrinths.

3. In order to facilitate the installation and disassembly of the flange, the fastening bolt and flange surface shall not be less than 200 mm.

4. When tightening the bolts, they should be symmetrical and intersecting to ensure the uniform force of the washers.

5. Bolts and nuts should be coated with molybdenum disulfide, graphite oil or graphite powder for subsequent removal: stainless steel, alloy steel bolts and nuts; pipeline design temperature is below 100℃ or 0℃; outdoor facilities; atmospheric corrosion or corrosive media .

6. Metal washers such as copper, aluminum and mild steel should be annealed before installation.

7. It is not allowed to bury flange connection directly. The flange connection of the buried pipeline should have an inspection well. If it must be buried, anti-corrosion measures should be taken.

The company also provides Forged Steel Flange, please feel free to contact us if necessary

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