Plate flange is also named plain flange, flat flange and slip on flange etc. A plate flange is a flat, circular disk that is welded onto the end of a pipe and allows it to be bolted to another pipe.
When building a pipeline, the length of the pipes used are not always known. By manufacturing the pipe separate from the plate flange, the welders can cut the pipe to length and weld a plate flange in place to join the pipes at any needed length. The plates can also be welded to the pipe on a slight bias, allowing two pipes to be joined that may not be precisely lined up.
Plate flange designs are uniform in any given size regardless of materials used to create them. This allows a 6-inch (15 cm) black pipe flange to mate perfectly with a 6-inch stainless steel flange. The plate flanges will have a serrated finish on the inside mating surface, which allows the plate to seat into the gasket material. This ensures a perfect seal between two joining pipes.
Plate flanges are most often used to connect parts of pipelines and in highways. This is due primarily to the fact that the flat flange is easy to use, and has such properties as cheapness and the ability to manufacture from different steel grades.