The American National Standard Institute, ANSI, has been overseeing guidelines and standards for products manufactured through several sectors.
WHAT IS ANSI?
ANSI-approved flanges are used for the industrial market which handles gas, air and steam process systems. Originally formed in 1918, the American National Standards Institute is headquartered in Washington, DC, and is widely recognized as the American organization responsible for overseeing the national standards and conformity assessment system for products, services, processes, systems, and personnel.
ANSI works domestically with American government agencies and organizations, as well as with international entities, to make ANSI standards useful around the world.
Prior to the creation of ANSI, standards for engineering and equipment such as flanges were developed by the American Institute of Electrical Engineers (AIEE or IEEE), the American Society of Mechanical Engineers (ASME), the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME), the American Society of Civil Engineers (ASCE), and the American Society for Testing and Materials (ASTM International) as members of the United Engineering Society, or UES.
Types of ANSI Flanges
The American National Standards Institute (ANSI) calls for the use of an ANSI flange to be used on specific applications. The ANSI flange is a three-part flange consisting of one flat flange, one flange machined to take a rubber O-ring and the rubber O-ring. The rubber O-ring is placed into the machined groove in one side of the flange and the assembly is tightened against the flat-faced side of the ANSI flange and secured with bolts which are torqued to a specific amount of pressure or tightness. This flange is welded to the ends of pipe to create an easy-to-separate connection. Other variations use a larger flat gasket that fits inside of the bolt circle of the flange.
While not rated for excessive pressure, the ANSI flange is commonly used on pipelines transporting air, water and steam under low to moderate pressure. While some flange types use a gasket that not only covers the flange face, the ANSI flange covers the bolt circle as well. These flange bolts run through the gasket and aid in the aligning of the gasket.
The ANSI flange does not use this type of gasket, thus the gasket must be slipped into position after some of the bottom bolts have been put into place. The bolts aid in supporting the gasket that floats in the center of the flange, sealing only the flange opening and creating a leak-proof passage for the pipeline products to pass through when the flange is tightened.
The lower pressure rating of the ANSI flange allows the gasket to remain floating in the middle of the two flanges instead of being held in place by the flange bolts. Unfortunately, this also creates a seal that, while sufficient for its intended purpose, is prone to leaking or blowing out completely much easier than the larger gaskets that are trapped in place by the flange bolts. The smaller gaskets also require more skill to install as they are not a simple drop-into-position type of gasket.
The majority of problems with an ANSI flange originate at the time of assembly. Some installers use a screwdriver to push the gasket into position while tightening the flange bolts. This can create a small nick that ultimately develops into a crack over time. Other problems that contribute to defects in sealing are getting grease on the gasket, trapping debris between the flanges and improperly lining up gaskets at the time of installation.
Price and mechanical properties are higher than ordinary casting flange a grade. The flange is a part that connects the pipe with the pipe and the valve, is connected to the pipe end. It is also used for the flange on the equipment inlet and outlet.
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.
Standards of ANSI Flanges:
The classes for flat face flanges are Class 125 and Class 250. The classes for ring joint flanges, tongue and groove flanges and raised flanges are: Class 150, Class 300 (Class 400 - rarely), Class 600, Class 900, Class 1500 and Class 2500. ANSI flanges are divided into classes, depending on pressure, temperature and the type of material used.
Welding Neck Flanges
- ASME/ANSI B16.5 Class 150 WN
- ASME/ANSI B16.5 Class 300 WN
- ASME/ANSI B16.5 Class 600 WN
- ASME/ANSI B16.5 Class 900 WN
- ASME/ANSI B16.5 Class 1500 WN
- ASME/ANSI B16.5 Class 2500 WN
- ASME B16.47 Series A/MSS SP-44 Class 150 WN
- ASME B16.47 Series A/MSS SP-44 Class 300 WN
- ASME B16.47 Series A/MSS SP-44 Class 600 WN
- ASME B16.47 Series A/MSS SP-44 Class 900 WN
RTJ Flanges, Ring Type Joint Flange
- Dimensions of Ring Joint Facings
- Ring Joint Facings ASME/ANSI B16.5 & B16.47-1
- Ring Joint Facings ASME/ANSI B16.5 & B16.47-2
- Ring Joint Facings ASME/ANSI B16.5 & B16.47-3
- Ring Joint Facings ASME/ANSI B16.5 & B16.47-4
Threaded Flanges, TH Flanges
Slip-on flange
- ASME/ANSI B16.5 Class 150 SO
- ASME/ANSI B16.5 Class 300 SO
- ASME/ANSI B16.5 Class 600 SO
- ASME/ANSI B16.5 Class 900 SO
Lap Joint Flanges
- ASME/ANSI B16.5 Class 150 LJ
- ASME/ANSI B16.5 Class 300 LJ
- ASME/ANSI B16.5 Class 600 LJ
- ASME/ANSI B16.5 Class 900 LJ
- ASME/ANSI B16.5 Class 1500 LJ
- ASME/ANSI B16.5 Class 2500 LJ
Blind Flanges, BL Flange, BLRF
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