Engineering-grade carbon steel blind flanges designed for zero-leak performance in oil & gas, chemical, and water treatment pipelines — backed by fast global shipping and OEM/ODM customization.
Engineering-grade carbon steel blind flanges designed for zero-leak performance in oil & gas, chemical, and water treatment pipelines — backed by fast global shipping and OEM/ODM customization.
⚡ Direct factory pricing | Quality checks on every batch | Ships to USA, EU & Middle East
If you are purchasing 36 blind flange or a105 blind flange components purely on price, you may be inheriting catastrophic risk. Industry data on piping failures shows that flange joint leakage accounts for roughly 15–20% of unplanned downtime in process plants. Here is what procurement and operations teams typically face:
A substandard a105 blind flange might be 30% cheaper upfront, but when you factor in bolt-hole misalignment, out-of-spec thickness, and replacement labor, total cost of ownership climbs by 25–40% within 6 months.
Non-conforming heat treatment creates micro-cracks in the flange face. As Luan et al. demonstrated in their classic study on bolted flange joints, nonlinear contact behavior at flange interfaces can cause unpredictable bolt preload loss, leading to leak-before-containment events.
Dealing with a mid-tier trader means consolidating freight, missed sailings, and extreme freight quotes for oversized 36-inch blind flange. A direct factory relationship cuts lead times from 9 weeks to 3–4 weeks on average.
According to a 2025 engineering paper on rigid flange coupling material selection, "improper material and process choices are the leading contributor to both over-specification waste and in-service failure risks" (Cureus Journal of Engineering, 2025). This is exactly why engineers are moving toward factories that control the entire production chain from raw forging to final CNC machining.
At Cangzhou Weihuan Pipeline Equipment Co., Ltd., we manufacture and supply ASME B16.47 Series A (MSS SP-44) and Series B (API 605) 36-inch blind flanges as well as ASTM A105 forged steel blind flanges in sizes 1/2" through 24" (and up to 48" with custom machining). We are not a trading house — we are a supply-chain platform backed by a serious production capability.
A blind flange is a solid disc used to seal off a pipeline end, nozzle, or valve opening. Unlike weld-neck or slip-on flanges, a blind flange has no bore, making it ideal for pressure testing, future line expansion, and permanent isolation of dead-leg systems.
The 36-inch blind flange is a large-format component that follows ASME B16.47 (covering both Series A and Series B). Because of its massive surface area, it handles very high end loads and requires precise bolt-hole alignment for proper gasket seating.
ASTM A105 is the most widely used forged carbon steel specification for flanges and piping components. It offers an excellent combination of strength, weldability, and impact toughness at temperatures from -20°F to 1000°F.
An a105 blind flange is forged, not cast, meaning the grain flow is elongated along the final shape — resulting in superior mechanical properties compared to cast equivalents.
Each heat number is tracked from ingot to finished flange, with MTC certs included.
36 blind flange orders shipped 3-5 weeks. Standard A105 sizes ship in 2 weeks.
Each flange is hydrostatically pressure-tested and UV-examined for micro-cracks.
Meets ASME B16.47 Series A & B, plus ASME B16.5 for smaller A105 blinds.
Need a custom 36 blind flange for a subsea test setup? Our engineering team can design to your load-case and bolt-torque requirements. Talk to an engineer now →
The following parameters are critical when selecting a 36'' blind flange or ANSI A105 blind flange. All values align with ASME B16.47, ASME B16.5, and ASTM A105 standards.
| Pressure Class | Outside Diameter (mm) | Thickness (mm) | Bolt Circle Dia. (mm) | No. of Bolts / Size | Max Allowable Pressure (bar) |
|---|---|---|---|---|---|
| Class 150 | 660.4 | 66.7 | 622.3 | 20 × Ø35 mm | 15.9 |
| Class 300 | 749.3 | 79.4 | 701.7 | 20 × Ø41.3 mm | 41.4 |
| Class 600 | 838.2 | 104.8 | 787.4 | 20 × Ø50.8 mm | 82.7 |
| Class 900 | 990.6 | 139.7 | 927.1 | 20 × Ø66.7 mm | 124.1 |
| Property / Element | Specification |
|---|---|
| Carbon (C) | 0.35 max % |
| Manganese (Mn) | 0.60 – 1.05 % |
| Phosphorus (P) & Sulfur (S) | 0.035 / 0.040 max % |
| Tensile Strength | 485 MPa (70 ksi) min |
| Yield Strength | 250 MPa (36 ksi) min |
| Elongation in 2" | 22% min |
| Hardness | 167 HBW max |
Raised Face (RF) — 125–250 µin RMS standard
Ring Type Joint (RTJ) — for high-pressure/HPHT services
Flat Face (FF) — for cast iron or low-pressure mating
Male-Female (M&F) — custom OEM profiles
Tongue & Groove (T&G) — for specialty gaskets
Serrated finish per ASME B16.5
💡 Engineering note: When selecting a 36 inch blind flange, always check the gasket seating stress. For large-diameter Class 300+ flanges, RTJ facing is preferred to minimize leak risk at elevated temperatures. Our team can run bolt-load calculations for your specific gasket type.
A Gulf Coast refinery needed to isolate a 36-inch crude oil transfer line during a scheduled turnaround. They required six 36 blind flange Class 300 units with RTJ facing, supplied within 4 weeks.
📊 Results: Delivered in 26 days (22% ahead of schedule) • Zero leak on nitrogen heel test • Cost saving of 18% vs. the previous supplier.
An EU chemical producer replaced cast-iron blind flanges with forged a105 blind flange units in sizes 2" through 12" (Class 150) for a dead-leg elimination project.
📊 Results: 37% reduction in flange-related leaks • 100% compliance with PED 2014/68/EU • No process downtime caused by flange failure in 18 months.
These scenarios demonstrate how proper material selection and manufacturing traceability directly impact plant uptime. The reference stress approach used in fracture assessments (R6 FAD), as documented in structural integrity literature, reminds us that even a flanged connection can be the critical fracture path when base material quality is compromised. This is why our factory stage-gates every batch of a105 blind flange products with 100% ultrasonic inspection.
Open-die / closed-die forging at 2200°F normalized for grain uniformity.
Annealing or normalizing per ASTM A105 to relieve internal stress.
Precision CNC lathes achieve ±0.5mm dimensional tolerance on bolt circles and face flatness.
Hydrostatic test, ultrasonic inspection, PMI (positive material identification), and dye-penetrant checks on every batch.
The structural integrity of large pipe bends and flanged connections is a well-studied subject in finite element analysis literature. Our engineers understand that a 36 blind flange, with its enormous projected area, can exhibit significant shell-type deformation under external bending loads — a phenomenon documented in elbow and pipe stress index research. That is why we machine our flange faces on CNC equipment with 10-micron flatness accuracy, ensuring the entire gasket contact surface carries load evenly.
ISO 9001:2015
CE / PED
ASME / ANSI B16.5
UL / ETL
GS / TÜV
For compression/coupling applications, our partners also reference the tee fitting branch flow and reducer coupling engineering principles described in the 2025 Ultimate Guide to Malleable Pipe Fittings, ensuring their entire fitting inventory is optimized for flow efficiency and minimal pressure drop.
"We ordered 36 blind flange units for a water treatment plant upgrade. The machined faces were flawless."
"We've used two other suppliers for a105 blind flange in the past. The machining quality from Weihuan is noticeably better — bolt holes lined up perfectly with our existing pipe spools on the first try. We're now placing our 4th PO."
"I was skeptical about buying a large 36 blind flange from a factory in China. But their QC video call and third-party inspection report convinced us. The flange face flatness was within spec — verified by our own ultrasonic test."
"Lead time was the big differentiator. We got 14 pieces of 2-inch a105 blind flange Class 300 in 12 days door-to-door to Houston. Other suppliers told us 6-8 weeks. Real factory power."
"We needed custom RTJ facing on 18-inch a105 blind flanges for a high-pressure gas test rig. The Weihuan team worked with us on facing dimensions and delivered exactly what our mechanical engineer designed. Sealing was perfect at 800 bar."
For standard 36'' blind flange in Class 150–300 (ASME B16.47 Series A), lead time is 3–5 weeks from PO confirmation. For non-standard sizes, add 1–2 weeks for custom forging and machining. Air freight is available for urgent orders.
Yes. We offer hot-dipped galvanized, epoxy, FBE, or zinc-rich coating for a105 blind flange. For offshore use, we recommend inorganic zinc silicate or 3-layer PE coating per NORSOK M-501.
Absolutely. We have in-house CNC machining and a technical design team. We can produce custom facing, drilling patterns, oversized flanges, and special materials to your drawings. Sample lead time: 7–10 days.
Our MOQ is 1 piece for stock sizes (Class 150–300), and 2–5 pieces for custom sizes. Since we are a factory, we are flexible with mixed-container orders combining flanges and pipe fittings.
Every batch goes through 3-step QC: (1) incoming raw material chemical verification, (2) in-process dimensional inspection, and (3) final hydrostatic testing and independent inspection (SGS/BV/TÜV) if required. We provide full MTC per EN 10204 3.2.
We accept T/T (30% prepaid, 70% before shipment), L/C (at sight), and D/P. For long-term supply agreements, we can discuss open account terms based on your company's credit status.
Large flanges ship flat on steel pallets or loose in 20ft/40ft containers depending on volume. We use project cargo logistics for oversize items, with break-bulk or flat-rack containers as needed. We provide CIF/DAP/DDP quotes based on your destination port.
Yes, we provide free samples for standard a105 blind flange sizes up to 4 inches. You cover the shipping cost. Sample production takes 5–7 days.
🔒 Privacy policy: Your contact information and order details are treated as confidential and never shared with third parties.
Get a factory-direct quotation within 24 hours. Include your flange size, pressure class, quantity, and destination port.
Phone / WhatsApp
+86-18531701777
whxs@weihuantube.com
🛡️ 30-day quality guarantee • Pre-shipment inspection report • Free sample for qualified projects
David Wang — Senior Product Engineer & Global Supply Chain Specialist at Cangzhou Weihuan Pipeline Equipment Co., Ltd.
With over 15 years of experience in the design, manufacturing, and export of industrial pipe fittings, flanges, and prefabricated systems, David has personally led technical audits for more than 60 energy projects across North America, Europe, the Middle East, and Southeast Asia. He holds a B.S. in Mechanical Engineering and is an active member of the ASME B31 piping code user group.
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