Blind Flange Carbon Steel — Factory Direct Supplier | Huaxia-Steel
A carbon steel blind flange is a solid, disk-shaped flange with no central bore, used to close the end of a piping system, valve, or pressure vessel opening. Blind flanges are essential components in oil & gas, petrochemical, power, and water treatment industries where systems require permanent or temporary sealing at termination points. Huaxia-Steel manufactures and supplies carbon steel blind flanges in all standard sizes (1/2″ to 48″), pressure ratings (Class 150 to 2500), and international standards (ASME B16.5, EN 1092-1, JIS B2220) with full Mill Test Certificates and third-party inspection support.
Unlike other flange types, the blind flange must withstand the full internal pressure of the system across its entire face—making it the highest-stressed flange type in any piping system. This is why blind flanges are typically thicker and heavier than companion welding flanges of the same rating. Our carbon steel blind flanges are forged from certified billets and precision-machined to ensure leak-tight sealing and long service life under demanding conditions.
Product Overview
Carbon steel blind flanges from Huaxia-Steel are produced through open-die forging followed by precision machining. The solid disk design allows them to seal piping ends, provide access for inspection and cleaning, and serve as a reliable isolation point during maintenance. They are bolted to a matching flange using a gasket between faces, creating a pressure-tight seal.
Specifications & Dimensions
The following table shows typical dimensions for ASME B16.5 carbon steel blind flanges (raised face):
| Nominal Size | Class 150 OD (mm) | Class 150 Thk (mm) | Class 300 OD (mm) | Class 300 Thk (mm) | Bolt Holes |
|---|---|---|---|---|---|
| 1/2″ (DN15) | 89 | 9.5 | 95 | 11.2 | 4 |
| 1″ (DN25) | 108 | 11.2 | 117 | 14.2 | 4 |
| 2″ (DN50) | 152 | 14.2 | 165 | 19.0 | 8 |
| 4″ (DN100) | 229 | 19.0 | 254 | 28.9 | 8 |
| 6″ (DN150) | 279 | 22.2 | 318 | 36.5 | 12 |
| 8″ (DN200) | 343 | 25.4 | 381 | 44.4 | 12 |
| 12″ (DN300) | 483 | 33.3 | 559 | 61.9 | 20 |
Dimensions are nominal and may vary by standard. Contact us for complete dimensional tables including bolt circle diameter, bore, and stud size for all classes.
Weight Reference (Approximate)
| Size | Class 150 (kg) | Class 300 (kg) | Class 600 (kg) |
|---|---|---|---|
| 2″ (DN50) | 1.9 | 3.2 | 4.8 |
| 4″ (DN100) | 5.0 | 9.3 | 15.5 |
| 6″ (DN150) | 9.3 | 19.0 | 32.0 |
| 8″ (DN200) | 14.5 | 31.0 | 52.0 |
Available Carbon Steel Grades
| Grade | Standard | Carbon (max) | Yield (min MPa) | Tensile (min MPa) | Application |
|---|---|---|---|---|---|
| A105 | ASTM A105 | 0.35 | 250 | 485 | Standard temp, general service |
| A350 LF2 | ASTM A350 | 0.30 | 250 | 485 | Low-temperature service |
| A516 Gr.70 | ASTM A516 | 0.27 | 260 | 485 | Pressure vessel, low-temp |
| Q235B | GB/T 700 | 0.20 | 235 | 370 | General structural |
| S235JR | EN 10025 | 0.17 | 235 | 360 | European structural |
For low-temperature applications (below -29°C), we recommend A350 LF2 with Charpy V-notch impact testing. For high-temperature or pressure vessel service, A516 Gr.70 is preferred.
Manufacturing Standards
Our carbon steel blind flanges are manufactured and inspected to the following standards:
- ASME B16.5 — Pipe flanges and flanged fittings (NPS 1/2 to 24, Class 150–2500)
- ASME B16.47 — Large diameter flanges (NPS 26 to 60, Series A & B)
- EN 1092-1 — European flange standard (PN 6 to PN 100)
- JIS B2220 — Japanese industrial flange standard (5K to 20K)
- ASTM A105 / A350 — Material specifications for forged carbon steel flanges
- MSS SP-44 — Steel pipeline flanges
- API 605 — Large diameter carbon steel flanges (occasionally referenced)
All flanges are marked with size, rating, material grade, heat number, and manufacturer identification for full traceability.
Applications
Carbon steel blind flanges serve critical functions across industries:
- Oil & Gas: Wellhead isolation, pipeline end closures, test headers
- Petrochemical: Vessel manway blanking, line termination, pressure testing
- Power Generation: Boiler and turbine piping isolation, maintenance blanks
- Water Treatment: Reservoir and pipeline end caps, temporary closures
- Marine: Hull penetrations sealing, ballast system termination
- HVAC & Utilities: Chilled water and steam line end seals
- Pressure Testing: Temporary blanking during hydrostatic and pneumatic tests
Quality Assurance
Every blind flange undergoes rigorous quality control:
- Material verification — Spectrometer analysis of heat chemistry against order spec
- Forging inspection — Ultrasonic testing (UT) for internal defects per ASTM A105
- Dimensional check — Full dimensional inspection per ASME B16.5 tolerances
- Surface inspection — Visual examination for cracks, laps, and inclusions
- Hardness test — Brinell hardness verification (max 187 HB for A105)
- MTC documentation — EN 10204 3.1 Mill Test Certificate with every order
- Third-party inspection — SGS, BV, TÜV witnessing available on request
Packaging & Shipping
Blind flanges are packaged to prevent damage and corrosion during transit:
Standard lead time: 15–30 days depending on size and quantity. Expedited production available for urgent orders. We ship worldwide via FOB, CIF, CFR, or DAP Incoterms.
Why Choose Huaxia-Steel
Huaxia-Steel combines mill-direct pricing with stringent quality control. Our blind flanges are used by EPC contractors and distributors across 40+ countries. We offer:
- Competitive factory-direct pricing with no middleman markup
- Full range of sizes, classes, and facing types in stock or quick production
- Certified materials with EN 10204 3.1/3.2 documentation
- Flexible MOQ starting from 1 ton
- Third-party inspection support (SGS/BV/TÜV)
- Reliable global shipping with proper export documentation
Request a quote for carbon steel blind flanges. Contact Huaxia-Steel today with your required size, class, grade, and quantity. Our team will respond within 24 hours with a competitive offer and technical support.
