The American National Standard Institute, ANSI, has been overseeing guidelines and standards for products manufactured through several sectors. ANSI-approved flanges are used for the industrial market which handles gas, air and steam process systems.
 Series A 150 & 300 Blind Flange |  Series A 400, 600 & 900 Blind Flange |
 ANSI Series A Weld Neck Flange |  Series A 400, 600 & 900 Weld Neck Flange |
Purpose
Flanges are used to attach a series of pipes or other flanges together. Some flanges, such as in the oil and gas sector, are required to sustain under high amounts of pressure. ASNI provides standards to flange manufactures to test flanges before they can be marketed to a particular sector.
Significance
ANSI provides standards on flanges depending upon pressure in pounds per second per inch (PSI), according to size in inches of the flange. Pressure and size are dependent upon whether the flange is welded to the pipe, threaded or bolted.
Considerations
Depending on the material the flange is made from, such as cast iron or steel, and the type of threaded material used for fittings, every flange is designated to a particular class. From these class ratings, several requirements, such as pressure-temperature rating, bolt and nut dimensions, coating material and several other factors, make up the standards according to the flange characteristics.