What is a Pipe flange?

A pipe flange is a method of connecting pipes, valves, pumps and other equipment to form a piping system.

It also provides easy access for cleaning, inspection or modification. Flanges are usually welded or screwed. Pipe flanged joints are made by bolting together two flanges with a gasket between them to provide a seal.

Materials for Flanges

Pipe flanges are manufactured in all the different materials like stainless steel, cast iron, aluminium, brass, bronze, plastic etc. but the most used material is forged carbon steel and have machined surfaces.

In addition, flanges, like fittings and pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the flanges themselves, which are "lined flanges".

The material of a flange, is basically set during the choice of the pipe, in most cases, a flange is of the same material as the pipe.

All flanges, discussed on this website fall under the ASME en ASTM standards, unless otherwise indicated. ASME B16.5 describes dimensions, dimensional tolerances etc. and ASTM the different material qualities.

Dimensions of Flanges

Each flange according to ASME B16.5 has a number of standard dimensions. If a draftsman in Japan or a work preparer in Canada or a pipefitter in Australia is speaking about a Welding Neck flange NPS 6, Class 150, Schedule 40 ASME B16.5, then it goes over the flange which in the image here below is shown.

If the flange is ordered, the supplier want to know the material quality. For example ASTM A105 is a forged carbon steel flange, while A182 is a forged stainless steel flange.

Standard we supply

Outside of normal piping, it is possible to find a flanged pipe in several other areas as well. Most household and industrial water-based devices contain a specialized type of flanged pipe that connects them to the main water system. This pipe creates a seal that is specifically designed for that particular device. Common examples of these types of pipes may be found on toilets, water heaters and boilers.

Industrial piping systems have a different type of flange. These flanged pipes have a wide lip that stands several inches or meters away from the edge of the pipe. These pipes will match up with another pipe of the same design. These two pipes will end up bolted together through holes in the flange. Sometimes a gasket is placed between the two pipes to assure a watertight design, but often the bolting process makes the two pipes fit together so closely that they are physically watertight.

There are several different standards that determine the size and fitting styles of piping. In the United States, the American Natural Standards Institute (ANSI) sets the size for piping and flanges, and it is one of the larger standards used worldwide. In nearly every case, a pipe made to one national standard will not fit a pipe made to another. Since local designs will use local piping, this is usually only a problem in locations where machinery is brought in from elsewhere, like military bases or oil platforms.