Flange Markings: Flange Identification For Quality Assurance (You will know at a glance)

Most of the flanges you see have some capital letters on each outer ring. These obvious steel stamp marks are to allow us to distinguish flanges. Different letters represent different meanings, such as different pressure values ​​and diameters. In this blog, YANHAO will take you to understand the common flange marks and learn how to distinguish different flanges through flange marks.

Flange marking is like the ID card of the flange

Flange marking
Flange marking

Flange marking (usually steel stamp) refers to the identification content printed on the flange. This is like the ID card of the flange.

Every flange shipped from the factory should have a printed mark. You can identify the flange by the identification content and judge its model, specification, material, and other information.

Through the flange identification, the flange can be classified and categorized for better management. Secondly, during the delivery, acceptance, inspection, assembly, and maintenance of the flange, the flange must be identified, and the identification content provides such a basis.

Moreover, the steel stamp identification content can also provide quality information about the flange, which is convenient for quality control.

Detailed explanation of flange marking (You will know at a glance)

The image below is a YANHAO-made flange. We can see that the flange marking says: YH SO DN65 PN16 RF 304 HG/T20592 2009.

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YH SO DN65 PN16 RF 304 HG/T20592 2009
  • YH: YH is the abbreviation of YANHAO. Usually the manufacturer will write its abbreviation in the first position.
  • SO: SO refers to slip-on flange. The flange type is usually placed second here. Other common ones are WN (weld neck flange), SW ( socket welding flange), TH (threaded flange), and BL (blind flange), etc.
  • DN: DN represents the standard pipe diameter of the interface flange. DN65 refers to a pipe with a nominal diameter of 65 mm. The nominal diameter is a standard set for the convenience of design, manufacturing, and maintenance. It does not represent the actual inner or outer diameter of the pipe, but a nominal size.
  • You’ll usually see the words NPS here too. DN (Nominal Diameter) and NPS (Standard Pipe Size) are both units used to express pipe diameters, but they have different definitions and conversion methods. DN refers to the outside diameter or average outside diameter of the pipe, while NPS is a sizing system based on inches. They can be converted to each other; for example, DN65 corresponds to NPS 2.5.
  • RF: RF stands for raised face. It represents the sealing surface form, “raised face.” Other common ones are FM (flat face), MFM (male and female), TG (tongue and groove), FF (full face), and RJ (ring joint), etc.
  • 304: 304 means 304 stainless steel, the material of the flange. Common types include stainless steel (such as 304, 316, etc.), carbon steel (such as Q235A, Q235B, etc.), alloy steel, etc.
  • Additionally, 06Cr19Ni10 and 022Cr19Ni10 can stand in for 304 and 304L, respectively, where “06” and “022” stand for carbon contents of 0.06% and 0.022%, “Cr19” stands for chromium content of about 19%, and “Ni10” stands for nickel content of about 10%. Other material grades also have similar corresponding representations.
  • HG/T20592 2009: HG/T20592 2009 is a Chinese flange standard. It represents a standard for chemical flanges formulated in 2009. There are also standards from other countries, such as ANSI: American Standard, DIN: German Standard, EN: European Standard, JIS: Japanese Standard, etc.

Through the above example, you should be able to understand the meaning of different letters in flange markings. Below I will also put some pictures of flange markings produced by YANHAO and explain the meanings of these markings, respectively. If you are interested, you can continue to check it out.

Other flange marking examples

Flange Marking: HG20592-2009 DN 65 PN16 304
Flange Marking: HG20592-2009 DN 65 PN16 304

The meaning of the mark “HG20592-2009 DN 65 PN16 304” on the flange is as follows:

  • HG20592-2009: This is the Chinese chemical industry standard, which refers to the manufacturing and design standards for steel pipe flanges.
  • DN 65: Indicates that the nominal diameter of the flange is 65 mm, which is the diameter of the pipe.
  • PN16: Indicates that the nominal pressure of the flange is 16 bar, that is, 1.6 MPa, which is the pressure level that the flange can withstand.
  • 304: Refers to the material of the flange; 304 is a common austenitic stainless steel material with good corrosion resistance and processing performance.

In summary, this mark indicates a steel pipe flange manufactured in accordance with the HG20592-2009 standard, with a nominal diameter of 65 mm, a nominal pressure of 16 bar, and a material of 304 stainless steel.

Flange Marking: WN RF 150LB ASTM B564 B16.5 N10276
Flange Marking: WN RF 150LB ASTM B564 B16.5 N10276

WN RF 150LB ASTM B564 B16.5 N10276. The meanings of these markings are as follows:

  • WN: Indicates that this is a welding neck flange, which is a common flange type with a neck extending into the pipe for butt welding with the pipe
  • RF: Indicates that the sealing surface of the flange is a raised face, which is a common sealing surface form that helps to form a good seal at the connection
  • 150LB: Refers to the pressure rating of the flange. 150LB is a pressure rating in the ASME standard, corresponding to a pressure of about 1034 kPa (about 10.5 bar)
  • ASTM B564: This is an American Society for Testing and Materials (ASTM) standard that specifies the production requirements for forged bars, forgings and flanges of Hastelloy C-276 (N10276)
  • B16.5: This is part of the ASME standard, namely ASME B16.5, which specifies the dimensions and specifications of pipeline flanges and flanged pipe fittings
  • N10276: This is the UNS (Unified Numbering System) number of Hastelloy C-276, also known as 2.4819 or alloy C-276, which is a corrosion-resistant nickel-based alloy widely used in chemical, petrochemical, flue gas desulfurization, and other industries.

Overall, WN RF 150LB ASTM B564 B16.5 N10276 refers to a necked butt welding flange manufactured in accordance with the ASME B16.5 standard, with a pressure rating of 150LB and a raised face sealing surface. The material is Hastelloy C-276 and follows the ASTM B564 standard.

Final

This article details the importance of flange markings and key information on how to identify flanges through these markings. By explaining different marking codes, such as manufacturer abbreviations, flange types, nominal diameters, sealing surface forms, and material standards, the article helps readers quickly understand flange identification.

This information is essential for flange quality assurance, classification management, and identification during delivery, acceptance, inspection, assembly, and maintenance. The purpose of the article is to enable readers to quickly and accurately grasp the specifications and characteristics of flanges through the markings on the flanges to ensure the smooth, safe, and reliable operation of the piping system.

Author: Lewis Liu

Hello, my name is Lewis Liu, and I’m a professional sales engineer with over a decade of expertise in the flange fittings sector.

I am quite informed about flange selection, installation, and maintenance. I am passionate about providing customers with the greatest solutions for keeping their pipeline systems running smoothly, safely, and dependably.

If you have any queries or concerns concerning flange fittings for your pipelines, whether they are about selection, material choice, specification requirements, or anything else, please contact me at any time. I am dedicated to providing expert advice and assistance to help you make educated decisions and reach your objectives.

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