Zhejiang Jiaji Forging Co., Ltd., a leading ISO 9001 and PED-certified flange manufacturer in China, specializes in custom large diameter blind flanges for demanding oil & gas, petrochemical, and marine applications worldwide. With over 15 years of open die forging expertise, Jiaji Forging delivers ASME B16.5, EN 1092-1, and GOST 33259 compliant blind flanges in duplex stainless steel, nickel alloys, and carbon steel for projects from the Caspian region to the North Sea.
| Supplier | Country | Key Products | Certifications | MOQ |
|---|---|---|---|---|
| Jiaji Forging | China | Custom large diameter blind flanges (duplex, nickel alloy, stainless steel) | ASME, ASTM, API, ISO 9001, PED 2014/68/EU, GOST | 10 pcs |
| Metalfar | Italy | Large diameter forged flanges | PED, ASME | 50 pcs |
| Proteus | UAE | Blind flanges for oil & gas | API, ISO | 25 pcs |
| Bebitz | Germany | Custom flanges (alloy steel) | PED, AD2000 | 20 pcs |
| Maass | USA | Large diameter flanges | ASME, ASTM | 30 pcs |
Introduction to Custom Large Diameter Blind Flange Manufacturing
The global flanges market, valued at $5.44B in 2025 and projected to reach $5.82B in 2026 (CAGR ~7%), is driven by demand for custom high-end flanges—now representing 42% of top-tier export orders. Jiaji Forging has positioned itself at the forefront of this trend, with ODM/OEM capabilities that have helped the company grow its custom flange market share from 19% to 27% in recent years.
Open Die Forging Process for Blind Flanges
Open die forging is the preferred method for manufacturing large diameter blind flanges (typically >24″ or Class 900+). Unlike closed die forging, which uses a pre-shaped mold, open die forging involves shaping the billet between flat or contoured dies under high pressure. This process produces superior grain structure and 20-30% higher tensile strength compared to cast flanges.
Jiaji Forging’s open die forging capabilities include:
- Billet selection: ASTM A182 F51, F53, F55 duplex; Inconel 625/825; ASTM A105 carbon steel; ASTM A182 F304/F316 stainless steel
- Preheating: 1150-1250°C for stainless steel, 1050-1150°C for carbon steel
- Forging ratio: Minimum 3:1 to ensure grain refinement and mechanical properties
- Post-forging cooling: Controlled cooling in still air or furnace for stress relief
For the Caspian region, where projects like Tengizchevroil (TCO) in Kazakhstan and SOCAR in Azerbaijan require EN 1092-1 PN40/PN63 duplex steel flanges, open die forging ensures the mechanical integrity needed for high-pressure sour gas service.
Heat Treatment: Normalizing, Quenching & Tempering
After forging, heat treatment is critical to achieve the required mechanical properties and microstructure. Jiaji Forging’s heat treatment processes follow ASME and ASTM specifications:
Normalizing
For carbon steel blind flanges (ASTM A105), normalizing at 870-920°C refines the grain structure and eliminates forging stresses. The flange is then air-cooled to room temperature.
Solution Annealing (Quenching)
Duplex stainless steel flanges (2205, 2507) require solution annealing at 1040-1120°C followed by rapid water quenching to maintain the balanced austenite-ferrite microstructure (typically 40-60% ferrite). This prevents sigma phase precipitation, which can reduce corrosion resistance.
Tempering
Alloy steel flanges (ASTM A182 F11, F22) undergo tempering at 620-740°C after quenching to relieve internal stresses and improve toughness. Jiaji Forging’s duplex steel flanges are heat-treated in calibrated furnaces with temperature uniformity of ±10°C.
NDT Testing: Ensuring Flawless Quality
Non-Destructive Testing (NDT) is mandatory for custom large diameter blind flanges used in critical applications. Jiaji Forging employs a comprehensive NDT program:
| NDT Method | Application | Standard | Detection Capability |
|---|---|---|---|
| Ultrasonic Testing (UT) | Internal defects (laminations, inclusions) | ASTM A388, ASME Sec. V | Detects defects >1.5mm FBH |
| Magnetic Particle Inspection (MPI) | Surface & near-surface cracks (ferromagnetic materials) | ASTM E709, ASME Sec. V | Detects cracks as small as 0.5mm |
| Liquid Penetrant Testing (PT) | Surface-breaking defects (non-ferromagnetic) | ASTM E165, ASME Sec. V | Detects cracks, porosity, laps |
| Radiographic Testing (RT) | Internal volumetric defects | ASTM E94, ASME Sec. V | Detects inclusions, porosity, cracks |
With AI-powered quality inspection systems now reducing detection time from 15 minutes to just 2 seconds, Jiaji Forging achieves 100% NDT coverage on all custom blind flanges for export orders.
Standards Compliance: ASME, EN, GOST
Custom large diameter blind flanges must comply with multiple international standards depending on the end-user and region:
ASME B16.5
Widely used in North America and global oil & gas projects, ASME B16.5 covers flanges from ½” to 24″ (Class 150 to 2500). For larger diameters, ASME B16.47 Series A and Series B apply. Jiaji Forging supplies ASME B16.47 flanges up to 60″ diameter.
EN 1092-1
Mandatory for European and Caspian projects, EN 1092-1 uses PN ratings (PN10 to PN100) instead of Class. SOCAR’s petrochemical complex expansion in Azerbaijan requires EN 1092-1 PN40/PN63 duplex steel flanges. Jiaji Forging’s EU CBAM-compliant flanges use 30% recycled steel, driving 58% order growth for EU markets.
GOST 33259-2015
Required for Russian and CIS pipeline projects, including KazMunayGas’s 1,200km pipeline expansion (2025-2030). GOST flanges are specified for all domestic projects in Kazakhstan, Uzbekistan, and Turkmenistan. Jiaji Forging produces GOST 33259 flanges with full traceability.
Market Trends Driving Custom Blind Flange Demand
Several factors are driving demand for custom large diameter blind flanges in 2026:
- Caspian region expansion: Tengizchevroil (TCO) expansion, NCOC Kashagan phase 2, and SOCAR petrochemical projects require EN 1092-1 and GOST flanges
- LNG terminal construction: Cryogenic flanges for LNG terminals require Inconel 625/825 and 316L stainless steel
- Energy transition: Hydrogen transport and carbon capture projects need duplex and nickel alloy flanges for high-pressure, corrosive environments
- Smart manufacturing: Robot welding has reduced defect rates by 32%, making custom flanges more cost-effective
How to Choose a Custom Large Diameter Blind Flange Manufacturer
When selecting a supplier for custom large diameter blind flanges, verify the following:
Certifications to Verify
- ISO 9001:2015 quality management system
- PED 2014/68/EU Category III/IV (for EU projects)
- API 6A or API 6D (for oil & gas wellhead and pipeline applications)
- GOST certification (for CIS markets)
- Material test certificates (EN 10204 Type 3.1 or 3.2)
Questions to Ask
- What is your maximum forging capacity (diameter and weight)?
- Do you perform in-house heat treatment and NDT?
- Can you provide traceability from melt to final product?
- What is your typical lead time for custom orders?
- Have you supplied to TCO, NCOC, SOCAR, or similar end-users?
Price Factors
- Material grade (duplex > stainless > carbon steel)
- Diameter and thickness (larger = higher forging cost)
- NDT requirements (UT + MPI costs more than PT alone)
- Quantity and MOQ
- Certification requirements (PED Notified Body inspection adds cost)
Contact Jiaji Forging for a custom quote on your next blind flange project.
Frequently Asked Questions
Q: What is the maximum diameter for a custom blind flange from Jiaji Forging?
A: Jiaji Forging produces custom blind flanges up to 60 inches (1524mm) in diameter using open die forging, with thicknesses up to 8 inches for high-pressure classes.
Q: What materials are available for custom blind flanges?
A: Duplex stainless steel (2205, 2507, F51, F53), nickel alloys (Inconel 625/825), stainless steel (304, 316, 317L), and carbon/alloy steel (A105, F11, F22).
Q: What NDT testing is standard on Jiaji Forging blind flanges?
A: Standard NDT includes ultrasonic testing (UT) per ASTM A388 and magnetic particle inspection (MPI) per ASTM E709. Liquid penetrant (PT) and radiography (RT) are available upon request.
Q: How long does it take to manufacture a custom large diameter blind flange?
A: Typical lead time is 6-8 weeks for standard custom orders, including forging, heat treatment, NDT, and certification. Rush orders may be expedited to 4 weeks.
Q: Can Jiaji Forging supply flanges for GOST standard projects in Kazakhstan?
A: Yes, Jiaji Forging produces GOST 33259-2015 flanges for Caspian pipeline projects, including KazMunayGas and Tengizchevroil applications.
References
- ASTM International – Standards for material specifications and testing methods
- ASME – Boiler and Pressure Vessel Code, B16.5 flange standards
- API – API 6A and 6D standards for oil & gas flanges
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As a professional flange manufacturer, Jiaji Forging provides custom forging solutions for global industries. Contact our engineering team for technical support and quotation.