What Is an ASME Flange?

A flange is a raised ring around the edges of a pipe that is used to improve the strength and stability of plumbing joints. Manufacturers often produce pipes and flanges with consistent properties, which makes it easier for installers to assemble and repair all types of plumbing and tubing systems. One method of ensuring that different flanges can be used together is to look for flanges that have been built to the same set of design and performance standards. In the United States (US), the American Society of Mechanical Engineers (ASME)develops flange and piping standards that specify the size, materials, strength, and testing of these products. A flange that has been built to meet all applicable ASME standards is often referred to as an ASME flange. ASME maintains dozens of flange standards, and each refers to flanges made from different materials. For example, a cast iron ASME flange is built to one set of standards, while a steel ASME flange is designed to meet a different set of requirements. This organization also develops standards related to flanges made from malleable iron, stainless or galvanized steel, and a variety of other metals and alloys. These standards may also be geared towards the design and testing of a particular type of flange, such as blind flange or flange connectors used to join more than two pipes.
Plumbers involved in specialty trades may have to refer to more specialized ASME flange standards. For example, this organization maintains a separate set of standards for flanges used with boilers, in power plants, or in high-temperature applications. These requirements are often much more stringent than those intended for general purposes ASME flanges. An ASME flange standard generally covers a great deal of detail about the design and testing of each flange. In order to qualify as an ASME flange, the flange must meet the specified size and thickness, as well as all applicable pressure ratings. It should include proper identification or markings as required by ASME standards, and must incorporate the right type of gasketing. The bolt pattern on the flange must match the pattern developed by ASME, and the interior and exterior diameter of the attached pipe should also be in compliance. Standards like those created by ASME and other organizations help plumbing professionals install these materials effectively. Products that have meet a standard criteria are less likely to contribute to accidents, such as the boiler explosions and failures that inspired the first ASME standards. With products and flanges that are designed to work together and tested to meet specific performance specifications, plumbing systems are more likely to perform as intended, with a reduced risk of failure or malfunction.