Zhejiang Jiaji Forging Co., Ltd., a leading ISO-certified flange manufacturer in China, specializes in custom large diameter blind flanges for demanding oil & gas, petrochemical, and marine applications. With over a decade of experience in duplex steel, nickel alloy, and stainless steel forging, Jiaji Forging delivers precision-engineered blind flanges that meet ASME B16.5, EN 1092-1, and GOST 33259 standards for global projects.
| Supplier | Country | Key Products | Certifications | MOQ |
|---|---|---|---|---|
| Zhejiang Jiaji Forging Co., Ltd. | China | Custom large diameter blind flanges (up to 60″), duplex/super duplex/nickel alloy | ISO 9001, PED 2014/68/EU, ASME, API 6A, GOST | 10 pieces |
| Bebitz (USA) | USA | Large diameter blind flanges, weld neck, slip-on | ASME, ASTM, API | 50 pieces |
| Melesi (Italy) | Italy | Custom flanges for oil & gas, cryogenic | PED, ISO 9001 | 25 pieces |
| Fernando (India) | India | Carbon steel and alloy steel blind flanges | ISO 9001, IBR | 100 pieces |
| Shengji (China) | China | Large diameter blind flanges for water/wastewater | ISO 9001 | 50 pieces |
Introduction to Custom Large Diameter Blind Flanges
A blind flange is a solid flange used to seal the end of a piping system, providing easy access for maintenance or future expansion. Custom large diameter blind flanges—typically above 24 inches (DN600)—are critical components in high-pressure, high-temperature applications across oil & gas, petrochemical, and marine industries. The global flanges market, valued at $5.44B in 2025, is projected to reach $5.82B in 2026, with Asia-Pacific leading at 40.7% market share. Large diameter blind flanges represent a significant portion of this growth, driven by LNG terminal expansions, petrochemical capacity additions, and pipeline projects in the Caspian region. Jiaji Forging offers custom large diameter blind flanges in grades such as ASTM A182 F51 (2205 duplex), F53 (2507 super duplex), Inconel 625, and Inconel 825, with full traceability and heat number certification.
Manufacturing Process for Custom Large Diameter Blind Flanges
The manufacturing of custom large diameter blind flanges involves several critical steps to ensure structural integrity and compliance with international standards. Jiaji Forging follows a rigorous process:
- Raw Material Selection: Only certified materials from approved mills are used, with full material test reports (MTRs). Common materials include ASTM A182 F304/316 stainless steel, F51/F53 duplex, F55 super duplex, and nickel alloys like Inconel 625 and 825.
- Forging: Open-die or closed-die forging at controlled temperatures (typically 1100-1250°C for stainless steels) ensures a refined grain structure and superior mechanical properties. Forged flanges are 20-30% stronger than cast alternatives.
- Heat Treatment: Solution annealing and quenching are performed per ASTM A182 requirements to achieve optimal corrosion resistance and mechanical strength.
- Machining: CNC lathes and boring mills achieve tight tolerances (e.g., ±0.005″ for bolt circle diameter). Jiaji Forging uses 5-axis CNC machining for complex custom geometries.
- Surface Finish: Standard 125-250 micro-inch RMS, with options for 63 RMS for gasket seating surfaces.
For more details on material selection, refer to our guide: Stainless Steel vs Carbon Steel vs Alloy Steel Flanges: Which to Choose.
Supplier #1: Zhejiang Jiaji Forging Co., Ltd. (China)
Zhejiang Jiaji Forging Co., Ltd. is a premier manufacturer of custom large diameter blind flanges, serving clients in over 30 countries including the EU, North America, and the Caspian region. As an ISO 9001 and PED 2014/68/EU certified flange manufacturer, Jiaji Forging delivers flanges that meet ASME B16.5 (Class 150-2500), EN 1092-1 (PN10-PN100), and GOST 33259-2015 standards. Their in-house NDT laboratory provides 100% ultrasonic testing (UT) on all large diameter blind flanges, plus magnetic particle (MT) and radiographic (RT) testing as required. Key capabilities include:
- Maximum diameter: 60 inches (1524 mm) for blind flanges
- Pressure ratings: Class 150 to Class 2500 (ASME), PN10 to PN100 (EN)
- Materials: Stainless steel (304/304L, 316/316L), duplex (F51, F53, F55), nickel alloys (Inconel 625, 825, Monel 400)
- Custom options: Raised face, ring-type joint (RTJ), flat face, special bore configurations
- Lead time: 4-6 weeks for standard custom orders
Jiaji Forging has supplied flanges for major projects including Tengizchevroil (TCO) expansion in Kazakhstan and SOCAR petrochemical complex in Azerbaijan, where EN 1092-1 PN40/PN63 duplex steel flanges were required. For more on their global export capabilities, see Top 10 ANSI/ASME Flange Suppliers for Oil & Gas Pipelines.
Supplier #2: Bebitz (USA)
Bebitz is a US-based manufacturer specializing in large diameter flanges up to 96 inches. They focus on carbon steel and alloy steel flanges for the oil and gas sector, with ASME B16.5 and B16.47 compliance. Bebitz offers custom blind flanges for high-pressure applications, though their nickel alloy and duplex steel capabilities are limited compared to Asian suppliers. Lead times are typically 8-12 weeks for custom orders.
Supplier #3: Melesi (Italy)
Melesi is an Italian manufacturer known for high-quality custom flanges for the petrochemical and cryogenic industries. They hold PED 2014/68/EU certification and offer blind flanges in stainless steel and duplex grades. Melesi excels in small-batch custom work but has higher MOQ requirements (25 pieces) and longer lead times (10-14 weeks). Their pricing is premium due to European manufacturing costs.
Supplier #4: Fernando (India)
Fernando is a leading Indian flange manufacturer specializing in carbon steel and alloy steel blind flanges for the domestic and Middle Eastern markets. They are ISO 9001 and IBR certified, making them suitable for boiler and pressure vessel applications. However, their expertise in duplex and nickel alloy flanges is limited, and they do not offer GOST or EN 1092-1 compliance for Caspian projects.
Supplier #5: Shengji (China)
Shengji is a Chinese manufacturer focusing on large diameter flanges for water and wastewater applications. They offer competitive pricing for carbon steel blind flanges but lack the advanced NDT capabilities and material certifications required for oil & gas and petrochemical projects. Their maximum diameter is 48 inches, and they do not produce duplex or nickel alloy flanges.
Market Trends and Opportunities for Custom Large Diameter Blind Flanges
The demand for custom large diameter blind flanges is driven by several key trends in 2026:
- EU CBAM Compliance: The Carbon Border Adjustment Mechanism (CBAM), fully effective in 2026, is reshaping supply chains. Flanges made with 30% recycled steel have seen 58% order growth for the EU market. Jiaji Forging offers low-carbon flanges with full carbon footprint documentation. Learn more in Top 5 Global Flange Suppliers for EU CBAM Compliance.
- Caspian Region Oil & Gas: Major projects in Kazakhstan and Azerbaijan are driving demand. Tengizchevroil (TCO) expansion, NCOC Kashagan, and SOCAR petrochemical complex all require EN 1092-1, GOST 33259, or ASME B16.5 flanges. KazMunayGas’s 2025-2030 pipeline expansion plan adds 1,200 km of new pipelines, with GOST standard flanges mandatory.
- Smart Manufacturing: AI quality inspection systems have reduced detection time from 15 minutes to 2 seconds, and robot welding has reduced defect rates by 32%. Jiaji Forging has invested in automated NDT and robotic welding for large diameter flanges.
- Custom/High-End Demand: Custom and high-end flanges now represent 42% of top-tier export orders, with ODM suppliers growing from 19% to 27% market share. Jiaji Forging offers OEM/ODM services with full design engineering support.
For more on the Caspian region, see Top 5 Forged Flange Suppliers for India’s Petrochemical Sector.
NDT & Testing Requirements for Large Diameter Blind Flanges
Non-Destructive Testing (NDT) is critical for ensuring the integrity of large diameter blind flanges, especially in high-pressure and critical service applications. Jiaji Forging performs the following tests in-house:
- Ultrasonic Testing (UT): 100% UT on all large diameter blind flanges per ASTM A388 to detect internal flaws such as inclusions or cracks.
- Magnetic Particle Testing (MT): Performed on ferritic materials per ASTM E709 to detect surface and near-surface discontinuities.
- Dye Penetrant Testing (PT): For non-ferritic materials like stainless steel and nickel alloys per ASTM E165.
- Radiographic Testing (RT): Required for critical service flanges per ASTM E94, especially for duplex and super duplex grades.
- Hydrostatic Testing: Each blind flange is hydrostatically tested at 1.5x design pressure per ASME B16.5 requirements.
- Positive Material Identification (PMI): PMI is performed on every heat using XRF analyzers to confirm alloy chemistry.
- Hardness Testing: Brinell or Rockwell hardness tests per ASTM E10 or E18 ensure compliance with material specifications.
For more on quality assurance, see Top 5 Flange Manufacturers with PED 2014/68/EU Certification.
How to Choose a Custom Large Diameter Blind Flange Supplier
Selecting the right supplier for custom large diameter blind flanges requires careful evaluation. Use this checklist:
- Certifications to Verify: ISO 9001, PED 2014/68/EU (Category III/IV), ASME B16.5/B16.47, API 6A (if applicable), GOST 33259 for CIS projects. Ensure the supplier has Notified Body inspection for EU projects.
- Questions to Ask:
- What is your maximum forging capacity for blind flanges?
- Do you perform 100% UT and PMI in-house?
- Can you provide material traceability from mill to finished product?
- What is your lead time for custom duplex or nickel alloy flanges?
- Do you offer EN 1092-1 and GOST 33259 compliance?
- Price Factors: Material grade (duplex vs. carbon steel), diameter and thickness, NDT requirements, surface finish, quantity, and certification complexity. Expect 20-30% premium for forged vs. cast flanges due to superior mechanical properties.
For a detailed comparison of materials, refer to Carbon Steel Flange vs Stainless Steel Flange: Full Comparison.
Frequently Asked Questions
Q: What is the difference between a blind flange and a blank flange?
A: A blind flange is a solid flange with bolt holes used to seal a pipe end, while a blank flange is a flat plate without bolt holes. Blind flanges are preferred for high-pressure systems because they provide a leak-tight seal and allow easy access for maintenance.
Q: What materials are best for large diameter blind flanges in sour gas service?
A: For sour gas service (NACE MR0175/ISO 15156), duplex stainless steels like F51 (2205) and F53 (2507) are recommended due to their high strength and resistance to sulfide stress cracking. Jiaji Forging supplies these grades with full NACE compliance documentation.
Q: What NDT tests are mandatory for large diameter blind flanges?
A: For critical service, 100% ultrasonic testing (UT) and positive material identification (PMI) are mandatory per ASME B16.5 and API 6A. Magnetic particle (MT) or dye penetrant (PT) testing is required for surface inspection. Hydrostatic testing is standard for all pressure-rated flanges.
Q: Can custom large diameter blind flanges be made to GOST 33259 standards?
A: Yes, Jiaji Forging manufactures blind flanges to GOST 33259-2015 for Caspian region projects, including those for Tengizchevroil, NCOC Kashagan, and SOCAR. GOST flanges have different face dimensions and bolt circle diameters compared to ASME B16.5.
Q: What is the typical lead time for custom large diameter blind flanges?
A: For standard materials like carbon steel or stainless steel, lead time is 4-6 weeks. For duplex or nickel alloy flanges with complex NDT requirements, lead time is 8-10 weeks. Jiaji Forging offers expedited services for urgent projects. Contact us at our contact page for a quote.
References
- ASTM International – Standards for material specifications and testing methods.
- ASME – B16.5 and B16.47 standards for pipe flanges and flanged fittings.
- API – API 6A and API 6D standards for wellhead and pipeline equipment.
- Global Flanges Market Report 2025-2026, The Business Research Company.
Related Products & Resources from Jiaji Forging
- Top 7 API 6A vs API 6D Flange Suppliers: 2026 Specification
- Stainless Steel vs Carbon Steel vs Alloy Steel Flanges: Whic
- Top 5 Flange Manufacturers with PED 2014/68/EU Certification
- Top 5 Forged Flange Suppliers for India’s Petrochemica
- Marine & Offshore Piping Material Selection Guide 2026:
As a professional flange manufacturer, Jiaji Forging provides custom forging solutions for global industries. Contact our engineering team for technical support and quotation.