The specification for orifice flange sets is not particularly clear about ring groove connections for these flange assemblies. Our proprietary CAD flange drawings can give the impression that ring grooves are cut into the face of a flange that may be considered “flat face,” however this is not the case if you review the dimensions. For RTJ orifice flanges, the flange thickness *exclusive* of the depth of the groove must meet the same minimum thickness as that of a standard raised face orifice flange assembly, exclusive of the height of the raised face. Visually speaking, though it may *appear* that the flange groove is cut into a flat face, you can confirm with the dimensions outlined in the B16.36 flange specification that it is more accurately what some would refer to as a “full face” with extra thickness (how much thickness depends on the depth of the groove, just as it would be defined in ASME/ANSI B16.5). Some manufacturers still machine down the should of the face to make it appear similar to the raised portion of a proper RTJ groove flange, in order to avoid initial confusion. Also, note that larger RTJ orifice flanges will require angular taps to ensure proper clearance with the bottom of the groove, which cannot be altered or modified in any way.
In other words: NO, you cannot take a raised face orifice flange, machine down the face, add a groove, and just call it an RTJ orifice flange. Minimum dimensional requirements for flanges must meet the tolerances outlined in ASME / ANSI B16.36 and B16.5 No shortcuts, or else you are out of compliance!
Just a friendly reminder…here at Texas Flange we try to make the flange requisition and purchase experience as seamless as possible for our customers. This includes providing commodity stock pieces by the bulk load, as well as creating custom flange pieces for unique applications. Regardless of the scope of your flange inquiry, our sales and technical support staff is trained to provide you with whatever you need, even if your assigned sales member is out of the office.
All emails are monitored and answered when any individual is out of the office, so that you don’t need to hunt down a different email address in order to get your questions answered and your orders processed. Just send in your inquiry for flanges as you normally would, and we will answer back from the email address of the same representative you are familiar with. This allows your flange sales rep to review the correspondence from their own email archives when they return and gives them the ability to ensure all requirements are communicated clearly to every member of the production team.
All flange orders are digitally archived in a manner that allows for sales and support staff to make the necessary notations up through and beyond the shipping and invoicing process and as a result, all sales staff should be able to address any concerns you may have regarding your flange order.
Always remember that we at Texas Flange are working hard with our production team to review your request and provide accurate pricing and lead time as necessary.
We have received several inquiries over the years for nozzle type flanges, commonly referred to as “long weld necks.” These types of flanges and the different varieties in which they are offered are meant to replace pipe, not weld up to it, and as such we would like to clarify for everyone in the industry that these items do not have schedule bores. A typical weld neck flange has a weld prep at the tip of the neck to weld up to matching pipe, whereas long weld neck flanges, or “nozzles,” are square cut at the ends for the purpose of utilization with your tank or alternate assembly. As such, many inquiries which we receive include schedule bores that we eliminate in our quote reply to our customers, as these schedules are not applicable.
Our nozzle flanges are available in the more common lengths of 9”, 12”, and 16”, as well as any larger or smaller overall lengths to suit your needs. Typically, the larger the nominal size and pressure class flange, the larger the overall length requested. However, this is entirely subjective and at the discretion of the customer. Contrary to popular suggestion, there is no universal “standard” length because these parts are made in accordance with the application necessary. We offer a variety of barrel sizes, from the more familiar long weld necks, heavy barrels, and equal barrels. We also provide intermediate barrel products depending on your needs. As most regular weld neck flanges, these nozzles are typically made from forged carbon steel and stainless steel grades, though we do get the occasional request for chrome alloy and nickel alloy nozzle flanges. Feel free to submit your own technical drawing for quotation to our sales department and we would be happy to help get you the flanges you need.
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.
It's time to update your copy of the industry leading dimensions and weights flange catalog. Version 5.0 is out. http://www.texasflange.com/images/Catalog/catalog-c.pdf
Free to download, save, and use. If you would like a hard copy please let us know and we will send you one, also free of charge.
Over the years we have spent well over $1 million dollars educating the industry. The industry has rewarded us by making us the #1 visited website for flanges in the world.