midland-forge-and-fittings-pvt-ltd-logo

Spectacle Blind Flange

Figure 8 Blank Flange : Specifications | Materials | Types | Dimensions | Weight Chart | Tolerances | FAQ

Manufacturer & Exporter of ASME B16.48 Spectacle Blind Flanges (Figure 8 Blanks) in Carbon Steel, Stainless Steel, Alloy Steel & Nickel Alloys – Sizes ½” to 24”, Pressure Classes 150# to 2500#.

ASME B16.48 Spectacle Blind Flanges (Figure 8 Blanks)

Best Export Prices: sales@midlandforgefittings.com

Midland Forge and Fittings Pvt. Ltd. is a forward-looking manufacturer and exporter specializing in high-performance ASME B16.5 Spectacle Blind Flanges. With decades of engineering experience, we have built our reputation on precision, consistency, and the ability to meet the toughest project requirements across global markets.

Every Spectacle Blind Flange we produce is backed by a deep understanding of international standards such as ASME, ANSI, DIN, and EN, as well as project-specific requirements from our clients. From standard sizes to complex, custom-engineered flanges, our team ensures absolute dimensional accuracy, metallurgical integrity, and long service reliability.

Spectacle Blind Flange (Figure 8 Blank Flange) is a specialized piping component used to isolate a section of a pipeline or equipment for maintenance, inspection, or testing purposes without disrupting the flow in the rest of the system. It is called a “Figure 8” flange because of its unique shape—one side is solid (the blind) and the other is an open ring, connected by a narrow section, resembling the number 8. When installed, the solid side blocks the flow completely, while the open side allows the fluid or gas to pass. Spectacle Blind Flanges are widely used in high-pressure, high-temperature, and critical service pipelines where safe and controlled isolation is required.

We operate with a diverse materials portfolio, including Carbon Steel, Stainless Steel, Alloy Steel, Duplex & Super Duplex, and High Nickel Alloys. Each raw material undergoes rigorous testing before entering our production lines, and every finished Spectacle Blind Flange is subjected to advanced non-destructive and destructive testing methods to guarantee compliance with international quality benchmarks.

We are proudly supplied Figure 8 Flanges and other critical piping components to industries such as oil & gas, petrochemicals, power generation, offshore drilling, and marine engineering. Our customer base spans across North America, Europe, the Middle East, and Asia, where reliability, timely delivery, and technical expertise make us a trusted partner for high-pressure and high-temperature applications.

ASME B16.48 Figure 8 Flange

Spectacle Blind Flange Specifications

Size Range

15mm ( 1/2" NPS ) up to 600mm ( 24" NPS ), For 2500# in sizes from NPS 1/2 to NPS 12

Pressure Rating - Class

150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS

Marking

Grade / Material, Size (NPS or DN), Pressure Class (PN), Heat No, Standard, Manufacturer’s Name or Trademark

Face Type / Flange Connection Type

Flat Face (FF), Raise Face (RF), Ring Joint (RJT), Tongue and Groove (T&G), Male and Female (M&F)

Flange Form

Spectacle Blind / Figure 8 Blank Flange

Manufacturing Standards

ASTM (A105, A182, A350, A694, B564), ASME/ANSI, MSS-SP-44, API 6A.

Materials

Stainless Steel, Carbon Steel, Alloy Steel, Duplex Steel, Super Duplex, Nickel, Inconel, Incoloy, Hastelloy, Monel, Alloy 20, 254 SMO, Copper Nickel, Titanium.

Test Certificates

EN 10204/3.1B, Raw Materials Certificate, 100% Radiography Test Report, Third Party Inspection Report, etc

Dimensional Standards

ANSI B16.5, ANSI B16.47, ANSI B16.36, ANSI B16.48, BS 4504, EN1092, UNI 2277/2278, DIN, JIS, SABS1123, GOST-12820

Testing

Direct-reading Spectrograph, Hydrostatic testing machine, X-ray detector, UI trasonic flaw detector, Magnetic particle detector

Flange Coating/Surface Treatment

Anti-rust Paint, Oil Black Paint, Yellow Transparent, Zinc Plated, Cold and Hot Dip Galvanized

Production technique

Forged, Heat treated and machined
ASME B16.48, MSS SP - 44

Figure 8 Blank Flange – Materials, Grades & Standards

Material Category Standards / Grades (ASTM / ASME) Pressure Class / Size Range Typical Use / Application
Stainless Steel ASTM A182 F304 / F304L / F304H Class 150 – 2500, Size ½”–48” General purpose, corrosion-resistant piping
ASTM A182 F316 / F316L / F316H Class 150 – 2500, Size ½”–48” Chemical, marine, food & pharma industries
ASTM A182 F321 / F321H Class 150 – 1500, Size ½”–24” High temperature, stabilized service
Carbon Steel ASTM A105 (Forged CS) Class 150 – 2500, Size ½”–48” Pressure piping, oil & gas, general industries
ASTM A350 LF2 (Low Temp CS) Class 150 – 1500, Size ½”–24” Cryogenic & low temperature applications
Alloy Steel ASTM A182 F11 / F22 (Cr-Mo) Class 150 – 2500, Size ½”–24” Power plants, refineries, steam pipelines
ASTM A182 F91 Class 150 – 2500, Size ½”–24” High-temperature, power generation
Duplex / Super Duplex ASTM A182 F51 / F53 / F55 / F60 (UNS S31803 / S32205 / S32750 / S32760) Class 150 – 2500, Size ½”–24” Offshore, seawater, high corrosion service
Nickel Alloys ASTM B564 Inconel 600 / 625 / 718 Class 150 – 2500, Size ½”–24” Heat exchangers, chemical, aerospace
ASTM B564 Monel 400 / K500 Class 150 – 2500, Size ½”–24” Marine, seawater handling, pumps
Copper Nickel ASTM B151 / B467 (Cu-Ni 90/10, 70/30) Class 150 – 600, Size ½”–24” Shipbuilding, desalination, seawater systems
Titanium ASTM B381 Gr. 2 / Gr. 5 Class 150 – 600, Size ½”–12” Aerospace, seawater, lightweight piping
Aluminium ASTM B247 6061 / 5083 Class 150 – 300, Size ½”–12” Lightweight, non-corrosive, low-pressure piping
Get a Quote

Explore Industrial Flanges

Request for an Immediate Offer?

We will reply you in 2 hours during support time!

Conctact Now!

Explore All Products

Explore All Materials

ANSI/ASME B16.48 Class 150 Spectacle Blind Flange – Dimensions

Dimensions of ANSI/ASME B16.48 Spectacle Blind Flanges
NPS Outside Ø
A		 Inside Ø
B		 Center Line
C		 THK
t		 Web Width
W
1/2 45 16 60 3 38
3/4 54 21 70 3 38
1 64 27 80 3 38
1.1/4 73 42 90 6.4 38
1.1/2 83 48 100 6.4 38
2 102 61 120 6.4 51
2.1/2 107 73 140 6.4 51
3 133 89 150 6.4 64
3.1/2 159 102 175 9.7 64
4 172 114 190 9.7 64
5 194 141 215 9.7 76
6 219 168 240 12.7 76
8 276 219 300 12.7 76
10 337 273 360 15.7 102
12 406 324 430 19.1 102
14 448 356 475 19.1 108
16 511 406 460 22.4 108
18 546 457 580 25.4 114
20 603 508 635 28.4 121
24 714 610 750 31.8 140

ANSI/ASME B16.48 Class 300 Spectacle Blind Flange – Dimensions

NPSOutside Ø
A		Inside Ø
B		Center Line
C		THK
t		Web Width
W
1/25116656.438
3/46421806.438
17027906.438
1.1/479421006.438
1.1/292481156.438
2108611259.751
2.1/2127731509.751
3146891709.764
3.1/216210218512.764
417811420012.764
521314123515.776
624816827015.776
830521933022.476
1035927338525.4102
1241932445028.4102
1448335651531.8108
1653640657038.1108
1859445763041.1114
2065150868544.5121
2477261081050.8140

ANSI/ASME B16.48 Class 600 Spectacle Blind Flange – Dimensions

NPS Outside Ø
A		 Inside Ø
B		 Center Line
C		 THK
t		 Web Width
W
1/2 51 16 65 6.4 38
3/4 64 21 80 6.4 38
1 70 27 90 6.4 57
1.1/4 79 37 100 9.7 57
1.1/2 92 43 115 9.7 67
2 108 55 125 9.7 57
2.1/2 127 67 150 12.7 67
3 146 83 170 12.7 67
3.1/2 159 96 185 15.7 76
4 191 108 215 15.7 76
5 238 135 265 19.1 86
6 264 162 290 22.4 86
8 318 212 350 28.4 95
10 397 265 430 35.1 105
12 454 315 490 41.1 105
14 489 346 525 44.5 114
16 562 397 605 50.8 124
18 610 448 655 53.8 133
20 679 497 725 63.5 133
24 787 597 840 73.2 152

ANSI/ASME B16.48 Class 900 Spectacle Blind Flange – Dimensions

NPS Outside Ø
A		 Inside Ø
B		 Center Line
C		 THK
t		 Web Width
W
1/2 60 16 80 6.4 38
3/4 67 21 90 6.4 41
1 76 27 100 6.4 57
1.1/4 86 37 110 9.7 57
1.1/2 95 43 125 9.7 67
2 140 55 165 12.7 57
2.1/2 162 67 190 12.7 67
3 165 83 190 15.7 67
4 203 108 235 19.1 76
5 244 135 280 22.4 86
6 286 162 320 25.4 86
8 356 212 395 35.1 95
10 432 265 470 41.1 105
12 495 315 535 47.8 105
14 518 346 560 53.8 114
16 572 397 615 60.5 124
18 635 448 685 66.5 133
20 696 497 750 73.2 133
24 835 597 900 88.9 152

ANSI/ASME B16.48 Class 1500 Spectacle Blind Flange – Dimensions

NPS Outside Ø
A		 Inside Ø
B		 Center Line
C		 THK
t		 Web Width
W
1/2 61 16 80 6.4 38
3/4 67 21 90 9.7 41
1 76 27 100 9.7 64
1.1/4 86 35 110 9.7 64
1.1/2 95 41 125 12.7 70
2 140 53 165 12.7 70
2.1/2 162 63 190 15.7 76
3 172 78 205 19.1 76
4 206 102 240 22.4 89
5 251 128 290 28.4 89
6 279 154 320 35.1 89
8 349 203 395 41.1 102
10 432 255 480 50.8 114
12 518 303 570 60.5 114
14 575 333 635 66.5 127
16 638 381 705 76.2 133
18 702 429 775 85.9 146
20 752 478 830 95.3 152
24 899 575 990 111.3 178

ANSI/ASME B16.48 Class 2500 Spectacle Blind Flange – Dimensions

NPS Outside Ø
A		 Inside Ø
B		 Center Line
C		 THK
t		 Web Width
W
1/2 67 16 90 9.7 38
3/4 73 21 95 9.7 41
1 83 27 110 9.7 64
1.1/4 102 35 130 12.7 64
1.1/2 114 41 145 15.7 70
2 143 53 170 15.7 70
2.1/2 165 63 195 19.1 76
3 194 78 230 22.4 76
4 232 102 275 28.4 89
5 276 128 325 35.1 89
6 314 154 370 41.1 89
8 384 198 440 53.8 102
10 473 248 540 66.5 114
12 546 289 620 79.2 114

Figure 8 Piping Flange Weight Chart (lbs) – Pressure Class 150 to 2500

Nominal Pipe Size (in) Class 150 Class 300 Class 600 Class 900 Class 1500 Class 2500
½ 3 5 9 12 20 35
1 7 12 22 30 50 90
2 15 25 50 70 115 210
4 45 70 130 180 290 540
6 85 140 260 350 560 1040
8 145 230 420 560 900 1700
10 210 340 620 820 1320 2500
12 300 480 880 1160 1880 3600
16 600 950 1800 2350 3800 7300
24 1200 1900 3600 4700 7600 14600

Figure 8 Blank Flange Tolerances as per ANSI / ASME B16.48

Parameter Tolerance (Small NPS ½″–24″) Tolerance (Large NPS 26″–60″)
Overall Flange Thickness (T) ±0.50 mm ±0.80 mm
Male Face Height (h1) +0.00 / –0.25 mm +0.00 / –0.40 mm
Female Recess Depth (h2) +0.25 / –0.00 mm +0.40 / –0.00 mm
Flange Outside Diameter (OD) ±0.50 mm ±0.80 mm
Bolt Circle Diameter (BCD / K) ±0.50 mm ±0.80 mm
Bolt Hole Diameter (d) ±0.25 mm ±0.50 mm
Alignment / Runout 0.30 mm max 0.50 mm max
Gasket Contact Surface Finish (Ra) 3.2–6.3 µm (125–250 AARH) 3.2–6.3 µm (125–250 AARH)
How does the thickness of the blind and ring portion affect flange performance under high pressure?
  • Stress Distribution: The blind portion thickness must be sufficient to withstand internal pipeline pressure without yielding. Thicker blind portions reduce localized stress at the hub-to-body junction.
  • Bolt Loading: Uneven thickness can create non-uniform gasket compression, leading to leakage at high pressures.
  • Ring Portion: Must maintain adequate rigidity; too thin can deform under bolt torque or thermal expansion.
  • Engineering Guidance: ASME B16.48 specifies thickness proportional to nominal pipe size (NPS) and pressure class to balance strength, weight, and cost.
  • Cyclic loading: Repeated pressure cycles can induce fatigue at the hub-blind junction.
  • Thermal cycling: Differential expansion between flange material and gasket can reduce sealing efficiency.
  • Engineering Control: Use of alloy or duplex materials and controlled hub radius mitigates fatigue and thermal stress effects.
  • Routine inspection recommended in power, chemical, and offshore systems for high-cycle operations.
  • Weight Calculation: Depends on NPS, pressure class, material density, blind thickness, and ring thickness.
  • Torque Estimation: Based on bolt size, gasket type, and pressure class; ensures uniform seating without over-stressing flange.
  • Engineering Note: For flanges ≥24″ NPS or Class 1500–2500, mechanical lifting devices and torque wrenches are mandatory to avoid flange damage or improper sealing.
United Arab Emirates (UAE), Saudi Arabia, Oman, Qatar, Kuwait, Bahrain, Iraq, Jordan, Lebanon, Yemen, Iran, Israel, Germany, United Kingdom (UK), Italy, France, Spain, Netherlands, Myanmar, Singapore, Malaysia, Indonesia, Vietnam, South Korea, Philippines, Thailand, Bangladesh, Sri Lanka, Papua New Guinea, United States (USA), Canada, Brazil, Chile, Argentina, Colombia, Russia, Ukraine, Kazakhstan, Poland, Egypt, Algeria, Morocco, Tunisia, Libya, Nigeria, Ghana, Ivory Coast, Senegal, Cameroon, Gabon, Democratic Republic of Congo, Kenya, Tanzania, Uganda, Ethiopia, Rwanda, Zambia, South Africa, Mozambique, Namibia, Botswana