Large Diameter Blind Flange
Large diameter blind flanges are engineered to isolate and seal the ends of high-pressure pipelines, pressure vessels, and equipment nozzles, providing fully removable access for critical inspection and maintenance.
- Product Introduction
Large Diameter Blind Flange Manufacturer for Industrial Piping Systems
Large diameter blind flanges are engineered to isolate and seal the ends of high-pressure pipelines, pressure vessels, and equipment nozzles, providing fully removable access for critical inspection and maintenance. Compared to permanent welded end caps, bolted blind flanges enable non-destructive, rapid system access, significantly reducing maintenance downtime in oil & gas, chemical processing, offshore engineering, power generation, and water treatment infrastructure.
As an experienced heavy forging and machining facility, we manufacture large diameter blind flanges (26" to 120" / DN650 to DN3000) using premium open-die forged steel, seamless rolled rings, or heavy plate machining in strict compliance with international standards including ASME, EN, DIN, JIS, and GOST.
Technical Specifications & Business Terms
|
Item |
Technical Specification & Commercial Capability |
|
Size Range |
26" to 120" (DN650–DN3000) or custom oversized dimensions |
|
Pressure Ratings |
Class 150, 300, 400, 600, 900, 1500, 2500 |
|
Design Standards |
ASME B16.47 Series A & Series B, ASME B16.5, EN 1092-1, DIN, JIS, GOST |
|
Carbon Steel |
ASTM A105, A350 LF2 (Low Temp), A694 F42/F52/F60/F65/F70, CT20 |
|
Stainless Steel |
ASTM A182 F304/304L, F316/316L, F321, F347 |
|
Duplex & Exotic Alloy |
F51 (UNS S31803), F53 (UNS S32750), Inconel 625/825, Monel 400, Hastelloy C276 |
|
Facing Types |
Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), T&G, M&F |
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Max Piece Weight |
Up to 25 Metric Tons per single forging |
|
Annual Capacity |
15,000 Tons of large-diameter heavy flanges annually |
|
Typical Lead Time |
4 to 6 weeks for standard materials; flexible expedited scheduling for project emergencies |
|
Certification |
EN 10204 3.1 / 3.2 (ABS, DNV, BV, LR, TÜV, SGS available) |
Engineering & Manufacturing Capabilities
Flatness Control & Face Machining via Heavy-Duty CNC
Oversized blind flanges are highly susceptible to thermal distortion during heat treatment and subsequent machining. To prevent localized stress concentrations and micro-leakage at the gasket seating area, our facility utilizes dual-face parallel machining on heavy-duty 5-meter CNC vertical lathes. We control the sealing face flatness within tolerances tighter than ASME B16.47 mandates, ensuring uniform gasket compression during final field bolt-up.
- Surface Finish: Standard stock finish machined to 125–250 AARH (roughness), with custom smooth or concentric serrated profiles precisely executed per client specifications.
Multi-Spindle CNC Precise Bolt Hole Alignment
On large-diameter pipe spools, minor deviations in the Bolt Circle Diameter (BCD) or hole spacing will cause catastrophic alignment failures during field installation. We eliminate manual layout errors entirely by using automated multi-spindle CNC drilling machines. This digital indexing ensures that the hole quantity, diameter, and straddle-center orientation perfectly match mating valves, pumps, or equipment flanges.
Complete Material Traceability & Independent TPI
Every single flange is assigned a unique heat number directly linked to its raw material melt batch. We provide comprehensive documentation for engineering quality verification:
- EN 10204 3.1 Mill Test Certificates (MTC) detailing exact chemical composition and destructive mechanical properties (Charpy V-notch impact, tensile strength, hardness).
- Permanent low-stress stampings for unambiguous field verification and lifecycle tracking.
- Full coordination and welcoming of Independent Third-Party Inspection (TPI) agencies including SGS, TÜV, BV, DNV, and ABS.
Custom Engineering & Anti-Corrosion Weld Overlay (CRA)
- Tailored Fabrication: We machine custom thicknesses, non-standard drilling patterns, and engineered blind plates based on client drawings, including specialized corrosion-resistant alloy (CRA) weld overlay cladding (e.g., SS316L or Inconel 625 cladding on carbon steel base).
Global Logistics & Heavy-Duty Packing
Large-diameter flanges demand robust engineering protection against mechanical impact and marine environments during long-distance transit. We execute a strict, 4-stage heavy-duty packaging process to guarantee zero-rust and zero-damage delivery:
Surface Treatment: Flanges are thoroughly degreased, cleaned, and coated with a heavy-duty, high-viscosity rust-preventative oil to form a primary barrier against oxidation.
VCI Vacuum Sealing: The entire flange is wrapped and vacuum-sealed within VCI (Volatile Corrosion Inhibitor) plastic bags, continuously neutralizing moisture and salt air during extended sea freight transit.
Facing Protection: To prevent scratches or dents on the precision-machined sealing surface, heavy-duty flange face-protection covers (custom plywood or high-density plastic discs) are securely bolted or strapped to the facing.
Reinforced Crating: Flanges are secured horizontally within reinforced steel-framed crates or heavy-duty ISPM-15 export plywood boxes. Internal heavy timber bracing is fitted to prevent shifted loads under rough handling.
FAQ
Q: What is the difference between ASME B16.47 Series A and Series B blind flanges?
A: Series A (MSS SP-44): Thicker, heavier, and uses fewer but larger-diameter bolts. It is designed to withstand higher external piping loads, bending moments, and structural stresses, making it the preferred choice for standard pipeline infrastructure.
Series B (API 605): Thinner and lighter, utilizing a larger quantity of smaller bolts. It is primarily selected for compact spaces, light-duty process piping, or equipment nozzles where optimizing weight and component/bolting cost is critical.
Q: What is the maximum thickness and weight you can handle for a Class 900 or Class 1500 flange?
A: We can forge and machine blind flanges up to 120 inches (DN3000). The maximum thickness is governed by the pressure rating (e.g., a 60" Class 900 blind flange requires massive thickness and can weigh several tons). Our heavy-duty open-die hammers, rolled ring rolling mills, and 5m vertical CNC machines can comfortably handle single forgings up to 25 Metric Tons.
Q: Can you supply blind flanges with process taps or instrument connections?
A: Yes. We regularly supply custom-drilled and tapped holes (e.g., NPT threaded connections or Socket Weld bosses) on the blind body for pressure gauges, sampling valves, or drain lines. All taps are engineered and machined fully compliant with ASME Section VIII design code limits and standard reinforced branch dimensions.
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