How to Inspect Weld Neck Flange

As a key connecting component in pipeline engineering systems, weld neck flange bear the important responsibility of ensuring sealing and pressure performance. The quality of forged steel flange is directly related to the safe and stable operation of the entire industrial production system, so the inspect weld neck flange is of great significance. This article will start with the production standards of weld neck flange, elaborating on their material types, dimensional tolerance ranges, and deeply analyzing the core elements in the inspection process.

Introduction to Weld Neck Flange

Weld neck flange is a type of pipe flange characterized by its long, tapered hub that's designed to be butt-welded to a pipe. It's also called a tapered hub flange or high-hub flange, is a kind of flange that can relocate stress to the pipes, ensuring a decrease in high-stress concentration at the bottom of the flange. There are two welding neck flanges designs – the first type is used with wipes while the second, longer type cannot be used with pipes but with a process plant. These flanges, typically manufactured from forging, are actually welded to pipes.

It is widely used in high-pressure, high-temperature, and important industrial pipeline systems such as petroleum, chemical, power, metallurgy, etc. Due to its widespread use in important industrial pipeline processes, the inspect weld neck flange is a crucial step in ensuring their quality meets standards.

Standard of Forged Steel Flange

The manufacturing standards for forged steel flange involve multiple aspects, including material and chemical composition, size and accuracy, manufacturing process, surface quality, mechanical properties, identification and packaging, inspection and testing, and execution standards. These standards together constitute a complete system for the manufacturing and inspection of forged flanges, ensuring that the quality and performance of the flanges meet the requirements for use. Common production standards for forged flanges include American Standard (ASME/ANSI), European Standard (EN), German Standard (DIN), and Japanese Standard (JIS).

ASME B16.5 Flange

ASME B16.5 is an important specification developed by the American Society of Mechanical Engineers for the design, manufacture, and inspection of steel pipe flanges and flange fittings. Detailed regulations have been established for the design, dimensions, material selection, manufacturing process, inspection methods, and marking requirements of various types of flanges such as steel pipe flanges, bolted connection flanges, blind flanges, and ring connection surface flanges.

Size: 1/2 "-24"

Pressure: Class150, 300, 400, 600, 900, 1500, 2500

ASME B16.47A/B Large Size Weld Neck and Blind Flange

The full name of ASME B16.47 standard is "Large Diameter Steel Flanges", which is mainly applicable to large flanges with nominal diameters of NPS26 to NPS60 (DN650 to DN1500). This standard specifies in detail the requirements for the size, pressure rating, material, testing, etc. of large pipe flanges, providing a reliable technical basis for the connection of large pipelines in industries such as petroleum, chemical, power, and natural gas.

Size: 26 "-60"

Pressure: Class 75, 150, 300, 400, 600, 900

JIS B2220 Flange

JIS B2220 is an important part of the Japanese Industrial Standards (JIS), specifically a technical specification for steel pipe flanges. The JIS B2220 standard specifies the dimensions, materials, pressure ratings, and other parameters of steel pipe flanges to ensure the safety and reliability of connections.

Size: DN10-DN1500

Pressure: 5K, 10K, 16K, 20K, 30K, 40K, 63K

DIN 2527 Blind Flange

DIN 2527 is a type of German standard flange that specifies the dimensions, materials, pressure ratings, and other parameters of the flange. It is applicable to flange connections with pressure ratings ranging from PN6 to PN40 (some materials mention pressure ratings up to PN100, but the specific scope of application may vary depending on the version or specific requirements). This type of flange is mainly used in pipeline systems to connect two pipelines or pipeline fittings and achieve sealing through bolt fastening.

Size: DN10-500

Pressure: PN6-PN100

EN1092-1 Type01/05/11 Flange

EN1092-1 is an important standard for flanges and their connections developed by the European Committee for Standardization (CEN). The standard specifies key dimensions such as the outer diameter, inner diameter, thickness, bolt hole diameter, and center distance of the flange in detail, and sets strict tolerance ranges. These dimensions and tolerances ensure a good fit and sealing effect between the flange and the piping system.

Size: DN10-4000

Pressure: PN2.5-PN400

Material Standards and Grades

Carbon steel: This is the most widely used type of material in forged flanges, with good mechanical and welding properties, and a relatively low price. Common carbon steel materials include ASTM A105, A350LF2, A694, etc.

Chemical Composition

Mechanical properties

Stainless steel: When the medium transported by the pipeline system is corrosive, stainless steel flanges are usually used. Stainless steel material has excellent corrosion resistance and can effectively resist the erosion of corrosive media such as acid, alkali, and salt. The commonly used stainless steel materials include ASTM A182 F304, F316, F321H, etc. Stainless steel flanges have superior corrosion resistance due to the presence of elements such as chromium, nickel, and molybdenum, making them particularly suitable for corrosive environments such as marine and chemical industries.

Chemical Composition

Mechanical properties

Alloy steel: For pipeline systems with high temperature, high pressure, and special requirements, alloy steel material is an ideal choice. By adding different alloying elements such as chromium, molybdenum, vanadium, etc., alloy steel can significantly improve the high temperature resistance, corrosion resistance, and strength of flanges. Common alloy steel materials include ASTM A182 F5, F9, F11, F12, etc., which are widely used in high-temperature and high-pressure pipeline connections in fields such as power and petrochemicals.

Chemical Composition

Mechanical properties

Dimension and Tolerance

The dimensional accuracy of butt welding flange inspection directly affects its connection quality and sealing performance with the pipeline. Therefore, the dimensional tolerance range is one of the important indicators of inspection, mainly involving the following key dimensions:

Outer diameter: The tolerance range of flange outer diameter is usually controlled within ± 1.5mm. Excessive or insufficient outer diameter size can affect the installation of flanges and their compatibility with other components. Excessive size may result in difficulty in installation, while insufficient size may affect the stability of the connection.

Diameter of bolt hole center circle: The tolerance range for this dimension is generally ± 0.6mm. The accuracy of the diameter of the bolt hole center circle is crucial. If the deviation is too large, it will cause the bolt to fail to penetrate accurately, affecting the tightening effect of the flange and ultimately damaging the sealing performance.

Flange thickness: The tolerance range for flange thickness is usually ± 1.0mm. Insufficient thickness can reduce the load-bearing capacity of the flange and may cause deformation or rupture under high pressure conditions; Excessive thickness will increase costs and may also affect installation space.

The height and thickness of the neck: The height tolerance of the neck is generally ± 1.0mm, and the thickness tolerance of the neck is ± 0.8mm. As an important transition part between the flange and the pipeline, the dimensional accuracy of the neck directly affects the welding quality and the overall strength of the flange.

Specification of Class 150 Weld Neck Flange

Dimension of Class150 Weld Neck Flange

The above are the detailed parameters of Class 150lbs butt welded flanges. According to ASME B16.5 standard, the flange pressure rating can be divided into class 150lb，class 300lb，class 400lb，class 600lb，class 900lb，class 1500lb，class2500lb, To view other product parameters, please click on the following link:

• ASME/ANSI B16.5 300lbs

• ASME/ANSI B16.5 400lbs
  

• ASME/ANSI B16.5 600lbs

• ASME/ANSI B16.5 900lbs

• ASME/ANSI B16.5 1500lbs

• ASME/ANSI B16.5 2500lbs

How to Inspect Weld Neck Flange

Weld neck flange inspection is an important step that must be carried out before the product leaves the factory. It requires comprehensive testing from multiple aspects, including appearance, chemical composition, mechanical properties, dimensional accuracy, non-destructive testing, etc.

Inspection of Appearance

Inspect the surface of the flange with the naked eye or magnifying glass, and ensure that there are no defects such as cracks, shrinkage cavities, pores, folds, inclusions, etc. that affect quality. The sealing surface of the flange should be flat and smooth, without scratches, dents or other damages, to ensure good sealing performance. At the same time, the edges of the flange should be free of burrs, and the welding groove should meet the design requirements. The groove surface should not have impurities such as oxide skin and oil stains to ensure welding quality.

Material Chemical Composition analysis

Using spectral analysis and other methods to conduct chemical composition testing on the material of the flange, ensuring that its chemical composition meets the corresponding standards and design requirements. Flanges made of different materials have different properties, and deviations in chemical composition may cause changes in material properties, affecting the performance and safety of the flange. For example, insufficient content of elements such as chromium and nickel in stainless steel materials can reduce their corrosion resistance.

Inspection of Dimension

Using precision measuring tools such as calipers, micrometers, and dial indicators, according to the requirements of the design drawings and relevant standards, measure the key dimensions of the flange's outer diameter, bolt hole center circle diameter, thickness, neck height, and thickness one by one to ensure that they are within the specified tolerance range.

NDT

If there are special requirements, the flange needs to undergo non-destructive testing before leaving the factory, such as ultrasonic testing, radiographic testing, dye penetrant testing, magnetic particle testing, etc. Non destructive testing can effectively detect defects inside flanges, such as internal cracks, lack of fusion, slag inclusions, etc. These defects may not be detected during visual inspection and hydrostatic testing, but they can seriously affect the safety of flange use. Through non-destructive testing, potential quality hazards can be identified in a timely manner to ensure the internal quality of the flange.

Mechanical Performance Inspection: Sampling inspection of the mechanical properties of flanges, mainly including tensile strength, yield strength, elongation and other indicators. Mechanical performance is an important guarantee for flanges to withstand pressure and load. Its mechanical performance is determined through methods such as tensile testing to ensure that it can meet the working requirements of pipeline systems. For flanges used under high pressure and high temperature conditions, impact toughness tests are also required to verify their toughness under low temperature or impact loads.

Hydrostatic Test: Hydrostatic test is an important means of testing the sealing performance and overall strength of flanges. Connect the flange to the test blind plate, then inject water into the interior and apply the specified pressure. After holding the pressure for a period of time, check whether the flange has any leakage, and observe whether the flange is deformed, cracked, or other conditions. The pressure and holding time of the hydrostatic test should be determined based on the nominal pressure and standard requirements of the flange to ensure reliable sealing under actual working pressure.

The inspect weld neck flange is an important step in ensuring the safe and stable operation of pipeline systems. From the production standards and material types of forged steel flange, to the clear range of dimensional tolerances, to the strict control of various inspection elements, every step is crucial. Only through comprehensive and meticulous inspection can the quality of flanges be ensured to meet the requirements, providing a solid guarantee for the safe and reliable operation of pipeline engineering.