Several governing specifications exist for a wide variety of industrial steel flanges, and each have their own suitability for our customers’ applications. Here at Texas Flange, our most popular product lines include ASME/ANSI flanges, API flanges, AWWA flanges, and DIN flanges. Lets dive a bit deeper below.
ANSI/ASME flanges – B16.5 and B16.47
The current ANSI/ASME flange specifications of B16.5 and B16.47 trace their roots to the old B16.1 specification from decades past, which consisted primarily of cast iron. This specification in turn was developed from the original AESC/ASA committee B16 in the 1920s. These modern specifications are the result of countless hours of engineering and design to form a standard which could be utilized worldwide. Our most commonly requested flange specification, ANSI/ASME flanges continue to be the most widely used type of steel flange across various industries. The pressure vessel and fabrication sectors use these in abundance in their pressurized applications to retain and transport air, water, and a variety of other chemicals. Often found in refineries, ANSI/ASME flanges are a critical component in their infrastructure, and are primarily used to connect piping, valves, and other fittings which compose the bulk of a piping assembly. The 150# class of steel flanges is the most popular for low pressure and vacuum applications, as the design has proven to be effective in applications which require an occasional fluctuation in the temperature and pressure of the environment.
API flanges – 6B and 6BX
A standard developed for the American Petroleum Institute, the API 6A specification shares many characteristics with ANSI/ASME flanges. They are dimensionally similar, however their minimal design requirements for operating pressure begin in the 2000# class, which is derived from the ASME/ANSI 600# class. Certain jobs require the use of pressure classes as high as the 6BX 25000#, though this is much less common than the typical 6B range of 5000# and below. All API flanges require ring type joint facings with the proper gaskets for optimal integrity of their application. This higher-pressure base requirement is due to their overwhelmingly popular use in petrochemical / oilfield applications of a volatile nature. Upstream assemblies with API flanges consist of wellheads, drilling equipment, and much more. The downstream sectors of refinery and processing also require these flanges for the development of crude oil into products for the everyday consumer.
AWWA flanges – C207
A specification designed for generally lower pressure applications (300 psi or less), American Water Works Association flanges are the exact opposite of the API flanges and can be found in a variety of assemblies in which temperature is ambient and media is not corrosive. In most cases, this is simply for the transportation of well water and waste water. AWWA C207 steel flanges are usually of a mild carbon steel or stainless variant and are most often either of the ring slip on or blind disc style. Due to their intended design, they do not have ring joint or raised faces, and are typically sealed with rubber gaskets. Due to their cost and weight compared to other flange types, they are also becoming more popular with project work for structural steel types which require mating or filling a gap between existing flanges.
Across the pond, you will find the Deutsches Institute fur Normung (DIN) flange specification, consisting of a variety of European styles which have been unified into one code for the purpose of commonality. Although much less common than ANSI/ASME steel flanges in the United States, many of our international customers request flanges to these specifications for a variety of applications such as imported steel vessels, cargo ships, and other infrastructure which may consist of metric pipes/valves and European designed equipment. The subset flanges under the DIN standard consist of the same style of flanges in the United States, including the most commonly used slip on flanges, weld neck, flanges, and blind flanges. Adapter flanges can be custom made to end user requirements for the mating of American flanges to international ones, however we find it is a much more common and easy solution to provide DIN flanges to mate to existing equipment.
Boltex and Weldbend Corporation Applaud ITC Preliminary Injury Decision on Unfairly Traded Imports
Houston, TX and Argo, IL, August 12, 2016 – Today Boltex Manufacturing Co., L.P. (“Boltex”) and Weldbend Corporation (“Weldbend”) announced that the U.S. International Trade Commission (“ITC”) preliminarily determined that imports of finished carbon steel flanges from India, Italy and Spain are causing injury to the domestic industry. The Commission vote was 6-0, resulting in an affirmative decision. The ruling by the ITC demonstrates that there is a reasonable indication that imports are injuring the domestic flange industry and American workers. As a result of this decision, these cases against foreign producers in the above-named countries will proceed.“We applaud the affirmative decision found by the ITC, ruling that imports of finished carbon steel flanges from India,Italy and Spain have caused injury to U.S. producers,” says Frank Bernobich, President of Boltex. “Today’s vote marks a step in the right direction to restore fair trade practices and allow the market to operate on a level playing field.”“As family owned and operated businesses, the decision to file petitions against these unfair trade practices was a significant undertaking, but one that was necessary for our survival,” says James Coulas, Jr., President and CEO of Weldbend. “For generations Weldbend and its employees have manufactured great products and we only ask for the ability to operate in a fair market. We are extremely pleased with the ITC’s preliminary decision and that our cases can proceed.”
Boltex and Weldbend filed petitions concurrently with the ITC and the U.S. Department of Commerce (“Commerce”) on June 30, 2016. The ITC initiated their investigation on June 30, 2016 and Commerce initiated their investigations on July 20, 2016.Commerce will calculate antidumping margins and subsidy rates, which are designed to offset the amount by which the product is sold at less than fair value and the amount by which the product benefits from unfair government subsidies. In the Department’s initiation notice the Department estimated the dumping margins for steel flanges as “(1) India ranges from 17.80 to 37.84 percent; (2) Italy ranges from 15.76 percent to 204.53percent; and (3) Spain ranges from 13.19 percent to 24.43 percent” The subsidy rate from India was estimated to be above de minimis. Commerce is currently scheduled to make its preliminary subsidy determination on September 23, 2016, and its preliminary dumping determinations on . If an affirmative decision is found, Commerce will instruct U.S. Customs to collect antidumping duty cash deposits to offset the subsidies.
The 2003 Edition of ASME B16.5, Pipe Flanges and Flanged Fittings NPS ½ through NPS 24 Metric/Inch Standard, contains millimeter dimensions and pressure-temperature ratings expressed in bar, with US Customary units in either parenthetical or separate forms. The purpose of this paper is to offer an explanation about why some of the conversions were made the way they were.
The cognizant committee had two primary goals during the development of the metric values shown in the 2003 Edition:
• The dimensions in mm should reflect the needed precision as much as possible.
• Flanges manufactured using existing forging dyes and machinery settings based on the inch dimensions should be able to meet the requirements for the metric dimensions.
Conversion from the Original Fraction
ASME B16.5 dimensions before 1977 were expressed mostly in fractional inches instead of decimal inches. For example, 1/8 in. was shown as 0.12 in. or 0.125 in., depending on the intended precision of the dimension, starting in the 1977 edition.
Millimeter dimensions were converted from the original fractional inch dimensions rather than the decimal inch dimensions. For example, 1/16 in., when converted from the fraction, converts to 1.6 mm. The decimal “equivalent” (0.06 in.) converts to 1.5 mm. Some of the conversions shown in the tables will appear to be incorrect when converted from the decimal inch dimensions.
1/16 in. was sometimes converted to nearest 0.1 mm, sometimes converted to the nearest 0.5 mm, and at other times converted to the nearest 1 mm. The conversion depended on the needed precision of the measurement. So the millimeter equivalent for 0.06 in. is sometimes 1.6 mm, sometimes 1.5 mm and at other times 2 mm.
Dimensions that have tolerances are those that are considered to be needed for adequate fit-up and those important for integrity of the pressurized flanged joint. These dimensions were converted such that the metric dimensions are essentially the same as the US Customary dimensions, and the tolerances were selected such that the permitted deviations from the tabulated dimensions were nearly identical to those permitted by the US Customary dimensions.
Bolt circle diameter converted to nearest 0.1 mm. The committee believes this level of precision is needed to minimize problems with fit-up to other flanges, even though the tolerance on the dimension is 1.5 mm. Converting with less precision was expected to cause additional problems with centering metal gaskets as well.
Rev. June 10, 2004 1
Length through hub converted to nearest 1 mm. This dimension needs to be consistent in order to maintain overall dimensions for fabricated spools. The committee believes that maintaining this dimension to the nearest whole millimeter provides the needed precision.
Dimensions that have no tolerances are those that need not have precision for fit-up and don’t contribute significantly to the integrity of the pressurized flanged joint. Examples of those dimensions and the philosophy used to create the millimeter dimensions are:
1/16” raised face converted to 2 mm instead of 1.6 mm. Raised faces measuring something different than 2 mm meet the requirements of the standard. Conversion to the nearest mm reflects the intended precision of the dimension.
Outside diameter of flanges converted to nearest 5 mm. For example, NPS ¾ Class 600 Flange outside diameter. The 4-5/8” was converted to the nearest 5 mm (115) instead of the nearest whole mm (117) or tenth mm (117.5). Outside diameters measuring other than 115 mm meet the requirements of the standard. Conversion to the nearest 5 mm reflects the intended precision of the dimension.
Bolt hole diameters expressed in fractional inches. Inch dimension bolt holes were retained for flanges manufactured to metric dimensions. Inch bolts are recommended for use with these flanges. Extensive dimensional compatibility studies exploring the possibility of using metric as well as inch dimensioned bolting with ASME B16.5 flanges were conducted. The studies revealed that providing dimensions that allowed for the use of metric as well as inch dimensioned bolts, especially when combined with metal gaskets, was impossible. This conclusion was supported by experience with some flanges manufactured to ISO 7005-1, Metallic flanges – Part 1: Steel flanges.
The cognizant subcommittee did not intentionally change any of the requirements for dimensions in the 2003 Edition of ASME B16.5. The dimensions in mm reflect the needed precision as much as possible.
Flanges manufactured using existing forging dyes and machinery settings based on the inch dimensions should be able to meet the requirements for the metric dimensions. While acceptable dimension ranges are not precisely the same for the two units of measure, there is a significant amount of overlap. Still it is possible for a flange to meet the requirements in one system of units and not in the other.
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