As a leading stainless steel flange manufacturer with over 15 years of forging excellence, Longan Flange provides heavy-duty blind flanges (DN15 – DN4000) engineered for total pressure isolation. Our forged blind flanges are essential for sealing pipelines, valves, and pressure vessels in critical oil, gas, and chemical projects.
Full size range for standard & custom EPC projects.
Forging, CNC machining, and inspection under one roof.
Fully compliant with ASME B16.5 & EN 1092-1.
Critical Quality Alert: Many suppliers lower prices by “thinning” the center of the blind flange, compromising structural integrity. At Longan Flange, we strictly adhere to ASME B16.5 minimum thickness standards, ensuring zero deformation even during extreme high-pressure hydrostatic testing.
100% Spectral detection
Grain flow optimization
0.1mm tolerance audit
UT for high-pressure sizes
As a professional stainless steel flange manufacturer, we ensure your blind flanges arrive job-site ready. All Raised Faces (RF) are protected with plastic caps, and flanges are packed in heavy-duty, ISPM15-compliant plywood cases to prevent transit damage and iron ion contamination.
📥 Download Weight Chart (PDF)A: We manufacture blind flanges from DN15 (1/2″) to DN600 (24″) in Class 150-2500 as standard. Custom large-diameter blind flanges up to DN4000 are available on request.
A: MOQ starts from 1 piece for standard sizes, making it easy to place a small trial order or one-off replacement purchase.
A: Lead time depends on size, quantity, and material — larger diameters and duplex alloys generally require more production time than standard sizes in stock alloys. We confirm the exact delivery schedule in your quotation. Technical quotations and drawing reviews are provided within 24 hours of your inquiry.
A: Yes. We specialize in SS304/L, SS316/L, and Duplex alloys. All materials include Mill Test Certificates per EN 10204 3.1 and full spectral (PMI) detection reports. Third-party inspection can be arranged prior to shipment upon request.
A: Our flanges are manufactured in an ISO 9001, ISO 14001, and ISO 45001 certified facility, and hold CE and PED certification. Production is fully compliant with ASME B16.5 and EN 1092-1. Each order is supplied with Mill Test Certificates per EN 10204 3.1, and additional third-party inspection certificates are available upon request.
A: Yes. Beyond standard ASME B16.5/EN 1092-1 dimensions, we produce non-standard sizes and special materials to customer specification. Please share your drawing or requirements at the RFQ stage so our engineers can review feasibility before production.
A: Blind flanges are simpler to manufacture than other flange types, but they must withstand significantly higher mechanical stress at the center, since they have no bore to distribute pressure. This requires solid forged steel, strict thickness control per ASME B16.5, and specific bolting-force and pressure-resistance requirements to ensure a safe, permanent seal — the added material and process control is reflected in the price.
| Nominal size | Connection size | flange thickness | |||||
|---|---|---|---|---|---|---|---|
| DN | NPS | Flange outer diameter D | Central circle diameter K | Bolt hole diameter L | Number of bolt holes n | Bolt Th | C |
| 15 | 1/2 | 90 | 60.3 | 16 | 4 | M14 | 9.6 |
| 20 | 3/4 | 100 | 69.9 | 16 | 4 | M14 | 11.2 |
| 25 | 1 | 110 | 79.4 | 16 | 4 | M14 | 12.7 |
| 32 | 1 1/4 | 115 | 88.9 | 16 | 4 | M14 | 14.3 |
| 40 | 1 1/2 | 125 | 98.4 | 16 | 4 | M14 | 15.9 |
| 50 | 2 | 150 | 120.7 | 18 | 4 | M16 | 17.5 |
| 65 | 2 1/2 | 180 | 139.7 | 18 | 4 | M16 | 20.7 |
| 80 | 3 | 190 | 152.4 | 18 | 4 | M16 | 22.3 |
| 100 | 4 | 230 | 190.5 | 18 | 8 | M16 | 22.3 |
| 125 | 5 | 255 | 215.9 | 22 | 8 | M20 | 22.3 |
| 150 | 6 | 280 | 241.3 | 22 | 8 | M20 | 23.9 |
| 200 | 8 | 345 | 298.58 | 22 | 8 | M20 | 27.0 |
| 250 | 10 | 405 | 362.0 | 26 | 12 | M24 | 28.6 |
| 300 | 12 | 485 | 431.8 | 26 | 12 | M24 | 30.2 |
| 350 | 14 | 535 | 476.3 | 30 | 12 | M27 | 33.4 |
| 400 | 16 | 595 | 539.8 | 30 | 16 | M27 | 35.0 |
| 450 | 18 | 635 | 577.9 | 33 | 16 | M30 | 38.1 |
| 500 | 20 | 700 | 635.0 | 33 | 20 | M30 | 41.3 |
| 600 | 24 | 815 | 749.3 | 36 | 20 | M33 | 46.1 |
| Nominal size | Connection size | flange thickness | |||||
|---|---|---|---|---|---|---|---|
| DN | NPS | Flange outer diameter D | Central circle diameter K | Bolt hole diameter L | Number of bolt holes n | Bolt Th | C |
| 15 | 1/2 | 95 | 66.7 | 16 | 4 | M14 | 12.7 |
| 20 | 3/4 | 115 | 82.6 | 18 | 4 | M16 | 14.3 |
| 25 | 1 | 125 | 88.9 | 18 | 4 | M16 | 15.9 |
| 32 | 1 1/4 | 135 | 98.4 | 18 | 4 | M16 | 17.5 |
| 40 | 1 1/2 | 155 | 114.3 | 22 | 4 | M20 | 19.1 |
| 50 | 2 | 165 | 127.0 | 18 | 8 | M16 | 20.7 |
| 65 | 2 1/2 | 190 | 149.2 | 22 | 8 | M20 | 23.9 |
| 80 | 3 | 210 | 168.3 | 22 | 8 | M20 | 27.0 |
| 100 | 4 | 255 | 200.0 | 22 | 8 | M20 | 30.2 |
| 125 | 5 | 280 | 235.0 | 22 | 8 | M20 | 33.4 |
| 150 | 6 | 320 | 269.9 | 22 | 12 | M20 | 35.0 |
| 200 | 8 | 380 | 330.2 | 26 | 12 | M24 | 39.7 |
| 250 | 10 | 445 | 387.4 | 30 | 16 | M27 | 46.1 |
| 300 | 12 | 520 | 450.8 | 33 | 16 | M30 | 49.3 |
| 350 | 14 | 585 | 514.4 | 33 | 20 | M30 | 52.4 |
| 400 | 16 | 650 | 571.5 | 36 | 20 | M33 | 55.6 |
| 450 | 18 | 710 | 628.6 | 36 | 24 | M33 | 58.8 |
| 500 | 20 | 775 | 685.8 | 36 | 24 | M33 | 62.0 |
| 600 | 24 | 915 | 812.8 | 42 | 24 | M39X3 | 68.3 |
| Nominal size | Connection size | flange thickness | |||||
|---|---|---|---|---|---|---|---|
| DN | NPS | Flange outer diameter D | Central circle diameter K | Bolt hole diameter L | Number of bolt holes n | Bolt Th | C |
| 15 | 1/2 | 95 | 66.7 | 16 | 4 | M14 | 14.3 |
| 20 | 3/4 | 115 | 82.6 | 18 | 4 | M16 | 15.9 |
| 25 | 1 | 125 | 88.9 | 18 | 4 | M16 | 17.5 |
| 32 | 1 1/4 | 135 | 98.4 | 18 | 4 | M16 | 20.7 |
| 40 | 1 1/2 | 155 | 114.3 | 22 | 4 | M20 | 22.3 |
| 50 | 2 | 165 | 127.0 | 18 | 8 | M16 | 25.4 |
| 65 | 2 1/2 | 190 | 149.2 | 22 | 8 | M20 | 28.6 |
| 80 | 3 | 210 | 168.3 | 22 | 8 | M20 | 31.8 |
| 100 | 4 | 275 | 215.9 | 26 | 8 | M24 | 38.1 |
| 125 | 5 | 330 | 266.7 | 30 | 8 | M27 | 44.5 |
| 150 | 6 | 355 | 292.1 | 30 | 12 | M27 | 47.7 |
| 200 | 8 | 420 | 349.2 | 33 | 12 | M30 | 55.6 |
| 250 | 10 | 510 | 431.8 | 36 | 16 | M33 | 63.5 |
| 300 | 12 | 560 | 489.0 | 36 | 20 | M33 | 66.7 |
| 350 | 14 | 605 | 527.0 | 39 | 20 | M36X3 | 69.9 |
| 400 | 16 | 685 | 603.2 | 42 | 20 | M39X3 | 76.2 |
| 450 | 18 | 745 | 654.0 | 45 | 20 | M42X3 | 82.6 |
| 500 | 20 | 815 | 723.9 | 45 | 24 | M42X3 | 88.9 |
| 600 | 24 | 940 | 838.2 | 51 | 24 | M48X3 | 101.6 |
| Nominal size | Connection size | flange thickness | |||||
|---|---|---|---|---|---|---|---|
| DN | NPS | Flange outer diameter D | Central circle diameter K | Bolt hole diameter L | Number of bolt holes n | Bolt Th | C |
| 15 | 1/2 | 120 | 82.6 | 22 | 4 | M20 | 22.3 |
| 20 | 3/4 | 130 | 88.9 | 22 | 4 | M20 | 25.4 |
| 25 | 1 | 150 | 101.6 | 26 | 4 | M24 | 28.6 |
| 32 | 1 1/4 | 160 | 111.1 | 26 | 4 | M24 | 28.6 |
| 40 | 1 1/2 | 180 | 123.8 | 30 | 4 | M27 | 31.8 |
| 50 | 2 | 215 | 165.1 | 26 | 8 | M24 | 38.1 |
| 65 | 2 1/2 | 245 | 190.5 | 30 | 8 | M27 | 41.3 |
| 80 | 3 | 240 | 190.5 | 26 | 8 | M24 | 38.1 |
| 100 | 4 | 290 | 235.0 | 33 | 8 | M30 | 44.5 |
| 125 | 5 | 350 | 279.4 | 36 | 8 | M33 | 50.8 |
| 150 | 6 | 380 | 317.5 | 33 | 12 | M30 | 55.6 |
| 200 | 8 | 470 | 393.7 | 39 | 12 | M36X3 | 63.5 |
| 250 | 10 | 545 | 469.9 | 39 | 16 | M36X3 | 69.9 |
| 300 | 12 | 610 | 533.4 | 39 | 20 | M36X3 | 79.4 |
| 350 | 14 | 640 | 558.8 | 42 | 20 | M39X3 | 85.8 |
| 400 | 16 | 705 | 616.0 | 45 | 20 | M42X3 | 88.9 |
| 450 | 18 | 785 | 685.8 | 51 | 20 | M48X3 | 101.6 |
| 500 | 20 | 855 | 749.3 | 55 | 20 | M52X3 | 108.0 |
| 600 | 24 | 1040 | 901.7 | 68 | 20 | M64X3 | 139.7 |
| Nominal size | Connection size | flange thickness | |||||
|---|---|---|---|---|---|---|---|
| DN | NPS | Flange outer diameter D | Central circle diameter K | Bolt hole diameter L | Number of bolt holes n | Bolt Th | C |
| 15 | 1/2 | 120 | 82.6 | 22 | 4 | M20 | 22.3 |
| 20 | 3/4 | 130 | 88.9 | 22 | 4 | M20 | 25.4 |
| 25 | 1 | 150 | 101.6 | 26 | 4 | M24 | 28.6 |
| 32 | 1 1/4 | 160 | 111.1 | 26 | 4 | M24 | 28.6 |
| 40 | 1 1/2 | 180 | 123.8 | 30 | 4 | M27 | 31.8 |
| 50 | 2 | 215 | 165.1 | 26 | 8 | M24 | 38.1 |
| 65 | 2 1/2 | 245 | 190.5 | 30 | 8 | M27 | 41.3 |
| 80 | 3 | 265 | 203.2 | 33 | 8 | M30 | 47.7 |
| 100 | 4 | 310 | 241.3 | 36 | 8 | M33 | 54.0 |
| 125 | 5 | 375 | 292.1 | 42 | 8 | M39X3 | 73.1 |
| 150 | 6 | 395 | 317.5 | 39 | 12 | M36X3 | 82.6 |
| 200 | 8 | 485 | 393.7 | 45 | 12 | M42X3 | 92.1 |
| 250 | 10 | 585 | 482.6 | 51 | 12 | M48X3 | 108.0 |
| 300 | 12 | 675 | 571.5 | 55 | 16 | M52X3 | 123.9 |
| 350 | 14 | 750 | 635.0 | 60 | 16 | M56X3 | 133.4 |
| 400 | 16 | 825 | 704.8 | 68 | 16 | M64X3 | 146.1 |
| 450 | 18 | 915 | 774.7 | 74 | 16 | M70X3 | 162.0 |
| 500 | 20 | 985 | 831.8 | 80 | 16 | M76X3 | 177.8 |
| 600 | 24 | 1170 | 990.6 | 94 | 16 | M90X3 | 203.2 |
| Nominal size | Connection size | flange thickness | |||||
|---|---|---|---|---|---|---|---|
| DN | NPS | Flange outer diameter D | Central circle diameter K | Bolt hole diameter L | Number of bolt holes n | Bolt Th | C |
| 15 | 1/2 | 135 | 88.9 | 22 | 4 | M20 | 30.2 |
| 20 | 3/4 | 140 | 95.2 | 22 | 4 | M20 | 31.8 |
| 25 | 1 | 160 | 108.0 | 26 | 4 | M24 | 35.0 |
| 32 | 1 1/4 | 185 | 130.2 | 30 | 4 | M27 | 38.1 |
| 40 | 1 1/2 | 205 | 146.0 | 33 | 4 | M30 | 44.5 |
| 50 | 2 | 235 | 171.4 | 30 | 8 | M27 | 50.9 |
| 65 | 2 1/2 | 265 | 196.8 | 33 | 8 | M30 | 57.2 |
| 80 | 3 | 305 | 228.6 | 36 | 8 | M33 | 66.7 |
| 100 | 4 | 355 | 273.0 | 42 | 8 | M39X3 | 76.2 |
| 125 | 5 | 420 | 323.8 | 48 | 8 | M45X3 | 92.1 |
| 150 | 6 | 485 | 368.3 | 55 | 8 | M52X3 | 108.0 |
| 200 | 8 | 550 | 438.2 | 55 | 12 | M52X3 | 127.0 |
| 250 | 10 | 675 | 539.8 | 68 | 12 | M64X3 | 165.1 |
| 300 | 12 | 760 | 619.1 | 74 | 12 | M70X3 | 184.2 |
+86-15727821389 +86-15355931307
Tel: +86-15727821389
E-mail: mft@longanflange.com
mft001@longanflange.com
Address: 620 Kongo Mingzhu Road, Yongxing Street, Longwan District, Wenzhou City, Zhejiang Province, China.
