Various Flange Dimensions

Flange dimensions are issued by the American Society of Mechanical Engineers (ASME) and articulated by the American National Standards Institute (ANSI). Flanges are plate-like devices that are installed in a piping system so as to facilitate the easy assembly and disassembly of the same. Flanges are usually round and can be found at the end of fittings, pipes and valves. Threaded pipe endings reinforced with couplings presented the only practical solution to joining steel fittings and pipes for several decades.

Improved technology in carbon steel welding has significantly reduced associated labor costs with the end result being a much stronger and better-sealed joint. However, in modern piping systems, threading is limited to smaller pipes— size 2 or smaller. Larger pipes, 3 inches and above are joined together using butt-welding of continuous fittings and pipes in instances that do not require dismantling or through the use of a pipe flange where dismantling may be needed from time to time. Three inch pipe flanges form the default standard for connections to most valves and equipment.

Other Flange Uses

Apart from piping systems, flanges are also used in nozzles. The correct flange dimensions are especially important during the bolting phase of the piping assembly. The gasket and flanges are bolted together to eliminated leakages. The fact that flange dimensions are standardized by the ANSI eases the assembly of smaller equipment flanges as well as the larger flanges found in major piping systems. Pressure vessels are equipped with body flanges which are specifically made for the equipment’s diameter. They are calculated and designed individually. According to ASME, the vast majority of piping and equipment flanges are made from forged carbon steel. However, there are some that are made from cast iron. It is important to note that flanges are primarily made in the material of the fitting and pipe to which they will ultimately be fitted.

Types Of Flange Dimensions

Among the numerous flange dimensions, the length is most critical of them all. The length varies from one type of flange to another. Other common flange dimensions include:

  • Flange thickness
  • Outside diameter of the flange
  • Bolt number
  • Bolt size
  • Bolt circle

Wide Flange Beams

The above flange dimensions are roughly the same although some will vary from one flange rating to another. Wide flange beams are also known as H-beams, I-beams, universal beams and rolled steel joists. Their cross-sections are H or I-shaped. The horizontal component of the wide flange beam is actually the flange while the vertical component is known as the web. The flange is capable of withstanding extreme shear and bending forces. Wide flange beam dimensions range from 8mm to 64mm depending on the intended use.

Blind Flanges

Blind flanges on the other hand are round plates which come with all the necessary bolt holes but no single center hole. This feature makes the blind flange ideal for closing off the openings of a pressure vessel as well as the ends of a piping system. Just like any other flange, it eases the re-opening of a vessel or pipeline once it has been sealed. Blind flange dimensions range from outer diameter, height, inner diameter, diameter between the bolt holes and the bolt-hole diameter. These blind equipment and pipe flange dimensions are further divided along pressure classes which form the primary flange ratings.