How many kinds of flanges
There are six types of flanges commonly used, plate flat welding flanges, slip on flanges, neck welding flanges, integral flanges, socket welding flanges and threaded flanges.
1. plate flat welding flanges
It can be represented by the letter "PL". Flange and piping are connected by a single-sided fillet weld. The steel plate is allowed to be manufactured, so the flange is convenient to draw, simple to manufacture, and low in cost, but the rigidity is poor, and it is only used in occasions where a medium with a low pressure is generally conveyed.
2. slip on flanges
It can be represented by the letter "SO". It is also a kind of flat welded flanges. It has a short neck, which increases the strength of the flange and improves the bearing capacity of the flange. So it can be used on higher pressure pipelines.
3. neck welding flanges
It can be represented by the letter "WN". Pipes and flanges are butt-welded. Butt welding joints are not easy to deform, high strength, and good sealing. Suitable for pressure or temperature fluctuations in the pipeline or high temperature, high pressure and low temperature pipelines, suitable for the delivery of expensive and non-generic medium occasions. Flanges are usually forgings.
4. integral flanges
It can be represented by the letter "IF". It is similar to flanges with neck butt welded steel tubes, and often incorporates flanges with equipment, tubes, fittings, valves, etc. This type is commonly used on equipment and valves. Integral flanges are mostly castings.
5. socket welding flanges
It can be represented by the letter "SW". The flange hole of the socket welding flange has a finite position table, which facilitates the insertion and positioning of the connecting pipe. The welding is a single-sided fillet weld, which is used when the pipe diameter is not more than DN50 and there is no clearance corrosion. The flange is usually made of forgings.
6. threaded flanges
It can be represented by the letter "TH". The connection between the flange and the steel pipe is a threaded connection and it is a non-welding flange. Compared with the flat-welded or welded flanges, the threaded flanges are easy to install and maintain, and can be used on pipelines that are not allowed to be welded on site. Threaded flanges are only used with inch series tubes. It is suitable for the occasions of conveying general media and working conditions.
In addition to the above six types of flanges, there are also loose collars for the welded ring and loose flanges for the flat ring. The sealing surface and the flange of the loose flange are composed of two separate parts. The seal and the pipe are welded. The flange is threaded on the pipe and can move freely on the pipe. The flange only plays the fastening role. Not in contact with media. The material of the seal is usually corrosion resistant and is mainly used for corrosive media. In some special occasions, loose flanges are used. If the bolts are loosened, the pipes need to be adjusted to facilitate the disassembly and assembly of the pipes.
The selection of flanges is subject to more regulations. The selection of flanges in pressure vessels and pressure pipelines should be designed by qualified professional designers. The flanges used in pressure vessels and pressure pipelines should follow the original design plan. Maintenance and inspection are not allowed to be changed without authorization. It is also not allowed to replace flanges with high pressure ratings with flanges with low pressure rating to ensure safe and reliable production.