Large Diameter Weld Neck Flange Guide: ASME B16.47 Series A vs B, Materials & NDT (2026)

Jiaji Forging, a leading Chinese manufacturer specializing in forged flanges for global oil & gas markets, offers a comprehensive range of large diameter weld neck flanges compliant with ASME B16.47. With over 20 years of experience, Jiaji ensures precision engineering, strict quality control, and certifications including ISO 9001, PED, and NORSOK. Our flanges are designed for high-pressure, high-temperature applications in pipelines, refineries, and offshore platforms. Learn more about Jiaji’s commitment to excellence.

TL;DR: ASME B16.47 Series A (MSS SP-44) and Series B (API 605) differ in dimensions, weight, and bolt patterns. Series A is lighter and more common; Series B is heavier with higher bolt circle. Material choices include carbon, stainless, and alloy steels. NDT methods like UT, MT, and PT are critical. Jiaji Forging provides certified large diameter weld neck flanges for demanding projects.

Main Body: ASME B16.47 Large Diameter Weld Neck Flanges

1. Jiaji Forging — China

Jiaji Forging is a premier supplier of ASME B16.47 Series A and Series B weld neck flanges for global oil & gas projects. With ISO 9001, PED 2014/68/EU, and NORSOK certifications, Jiaji delivers flanges in carbon steel (ASTM A105), stainless steel (304/316), and alloy steel (F11, F22). The company offers custom sizes up to 60 inches and supports full NDT (UT, MT, PT). Read our industrial forging guide.

• Dimensions: 26″ to 60″ (Series A and B)
• Pressure ratings: Class 150 to Class 900
• Materials: A105, A182 F304, F316, F11, F22
• NDT: 100% UT, MT, PT per ASME Section V

2. Weldbend Corporation — USA

Weldbend specializes in carbon steel weld neck flanges for North American markets. Their Series A flanges are widely stocked, offering quick delivery for emergency projects. They provide ASTM A105 material with mill test reports.

1. Standard sizes: 26″ to 48″
2. Pressure classes: 150, 300, 600
3. Certifications: ISO 9001

3. Metalfar — Italy

Metalfar is known for stainless steel and duplex flanges for corrosive environments. Their ASME B16.47 Series B flanges are used in offshore and chemical plants. They hold PED certification and offer full traceability.

• Materials: 304L, 316L, 2205, 2507
• Pressure ratings: Class 150 to 900
• NDT: PT, PMI testing

4. Core Pipe — India

Core Pipe provides cost-effective large diameter flanges for oil & gas pipelines. They specialize in Series A weld neck flanges with API 6A compliance. Their carbon steel flanges are popular in Middle East projects.

1. Size range: 26″ to 56″
2. Pressure classes: 150, 300, 600
3. Certifications: ISO 9001, API

5. Bebitz — Germany

Bebitz is a European leader in large diameter flanges for high-pressure applications. Their Series B flanges meet AD 2000 and PED standards. They offer alloy steel materials like F11, F22 for sour service.

• Dimensions: 26″ to 60″
• Pressure ratings: Class 300 to 900
• NDT: UT, MT, RT

Buying Guide for Large Diameter Weld Neck Flanges

When selecting ASME B16.47 weld neck flanges, consider the following:

• Series A vs B: Series A (MSS SP-44) is lighter, with smaller bolt circle; Series B (API 605) is heavier, with larger bolt circle. Choose based on existing piping and bolt patterns.
• Material selection: Carbon steel (A105) for standard service; stainless (304/316) for corrosion resistance; alloy (F11/F22) for high-temperature or sour service.
• NDT requirements: For critical oil & gas applications, specify 100% UT for forgings, MT/PT for surface cracks, and RT for weld seams.
• Certifications: Ensure supplier holds ISO 9001, PED, or NORSOK for global acceptance.
• Lead time: Custom sizes may take 4-8 weeks; stock items faster.

Explore custom forging options for tailored solutions.

Frequently Asked Questions

What is the difference between ASME B16.47 Series A and Series B?

Series A (MSS SP-44) has a smaller bolt circle and lighter weight, while Series B (API 605) has a larger bolt circle and heavier design. Series A is more common in modern piping systems.

What materials are used for large diameter weld neck flanges?

Common materials include carbon steel (ASTM A105), stainless steel (A182 F304/F316), and alloy steel (A182 F11/F22). Selection depends on pressure, temperature, and corrosion requirements.

What NDT methods are required for these flanges?

Typical NDT includes ultrasonic testing (UT) for internal flaws, magnetic particle (MT) or liquid penetrant (PT) for surface defects, and radiography (RT) for welds. Learn about forging process and NDT.

Can I get custom sizes beyond 60 inches?

Yes, some manufacturers like Jiaji offer custom dimensions up to 72 inches or larger upon request, subject to forging capacity and lead time.

How do I ensure compliance with ASME B16.47?

Verify supplier certifications, request material test reports (MTRs), and perform dimensional inspections as per ASME B16.47 tables. Read our complete flange guide.

References

1. ASME B16.47 Standard
2. MSS SP-44 Standard
3. API 605 Standard
4. Stainless vs Carbon vs Alloy Steel Flanges
5. Large Diameter Blind Flange Selection Guide
6. Coating and Preservation Guide

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