Spectacle blind, flange spade, and ring spacer are forged products used to blind pipelines (temporarily or permanently). These devices are cost-effective alternatives to isolation valves. A spectacle blind combines, in one single product, a flange spade and a ring spacer. Flange spades and ring spacers, as separate products, are used when the rotation of a spectacle blind would be difficult due to space constraints. ASME B16.48 covers the dimensions and specifications of these isolation devices.
SPECTACLE BLIND OPERATION
Spectacle blinds, spades, and ring spacers are installed between flanges to sections of a pipeline permanently or temporarily as shown in this Youtube video:
Spectacle blinds are available in standard sizes up to 24 inches and in forged material grades like ASTM A105 (high-temperature carbon), A350 low-temperature carbon), and various ASTM A182 grades (alloy, stainless steel, duplex). Click on the link to learn about the chemical and mechanical properties, and the selection criteria, of these common spectacle blind grades (which are the same as flanges).
Where to buy spectacle blinds? Generally, flange factories are also spectacle blind manufacturers.
The reference specification for pipeline isolation devices (including spectacle blind, ring spacers, and line blanks) is ASME B16.48.
Spectacle blinds (also defined “spectacle flanges”) are manufactured from steel plates and are basically two interconnected discs: one is actually a ring (i.e. a disc with a hole of the same bore size of the pipeline), the other is a solid disc.
It is easy to understand if a spectacle blind is in an open or closed position, as one of the two discs is always outside the pipe (so when the ring is visible, the pipeline is closed; when the solid disc is visible outside, the pipeline is open). For spades and ring spacers, holes on the hangers inform the staff.

Carbon steel spectacle blinds are manufactured out of a single piece of steel, whereas alloy / stainless steel blinds can be manufactured by welding more pieces together (generally up to three).
SPECTACLE BLIND TYPES
There are three types of spectacle blinds:
- Flat face spectacle blind (FF): similar to a flat face flange, the surface of the disc is flat (suited for flat face gaskets, for low-pressure applications).
- Raised face spectacle blind (RF): likewise raised face flanges, there is an additional thickness on the surface of the disc. This type fits semi-metallic gaskets, as the spiral wound type.
- Ring joint face spectacle blind (RTJ): a groove is inscribed on the surface of the disc. This type is used in conjunction with ring joint gaskets.
SPECTACLE BLIND DIMENSIONS in MM ASME B16.48
CLASS 150
Class 150 Spectacle blind dimensions in mm
Spectacle Blind NPS Dimensions Class 150 | A | B | C | t | W |
1/2 | 45 | 16 | 60 | 3 | 38 |
3/4 | 54 | 21 | 70 | 3 | 38 |
1 | 64 | 27 | 80 | 3 | 38 |
1¼ | 73 | 42 | 90 | 6.4 | 38 |
1½ | 83 | 48 | 100 | 6.4 | 38 |
2 | 102 | 61 | 120 | 6.4 | 51 |
2½ | 107 | 73 | 140 | 6.4 | 51 |
3 | 133 | 89 | 150 | 6.4 | 64 |
3½ | 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 |
CLASS 300
Class 300 Spectacle blind dimensions in mm
Spectacle Blind NPS Dimensions Class 300 | A | B | C | t | W |
1/2 | 51 | 16 | 65 | 6.4 | 38 |
3/4 | 64 | 21 | 80 | 6.4 | 38 |
1 | 70 | 27 | 90 | 6.4 | 38 |
1¼ | 79 | 42 | 100 | 6.4 | 38 |
1½ | 92 | 48 | 115 | 6.4 | 38 |
2 | 108 | 61 | 125 | 9.7 | 51 |
2½ | 127 | 73 | 150 | 9.7 | 51 |
3 | 146 | 89 | 170 | 9.7 | 64 |
3½ | 162 | 102 | 185 | 12.7 | 64 |
4 | 178 | 114 | 200 | 12.7 | 64 |
5 | 213 | 141 | 235 | 15.7 | 76 |
6 | 248 | 168 | 270 | 15.7 | 76 |
8 | 305 | 219 | 330 | 22.4 | 76 |
10 | 359 | 273 | 385 | 25.4 | 102 |
12 | 419 | 324 | 450 | 28.4 | 102 |
14 | 483 | 356 | 515 | 31.8 | 108 |
16 | 536 | 406 | 570 | 38.1 | 108 |
18 | 594 | 457 | 630 | 41.1 | 114 |
20 | 651 | 508 | 685 | 44.5 | 121 |
24 | 772 | 610 | 810 | 50.8 | 140 |
CLASS 600
Class 300 Spectacle blind dimensions in mm
Spectacle Blind NPS Dimensions Class 600 | A | B | C | t | W |
1/2 | 51 | 16 | 65 | 6.4 | 38 |
3/4 | 64 | 21 | 80 | 6.4 | 38 |
1 | 70 | 27 | 90 | 6.4 | 57 |
1¼ | 79 | 37 | 100 | 9.7 | 57 |
1½ | 92 | 43 | 115 | 9.7 | 67 |
2 | 108 | 55 | 125 | 9.7 | 57 |
2½ | 127 | 67 | 150 | 12.7 | 67 |
3 | 146 | 83 | 170 | 12.7 | 67 |
3½ | 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 |
CLASS 900
Class 900 Spectacle blind dimensions in mm
Spectacle Blind NPS Dimensions Class 900 | A | B | C | t | W |
1/2 | 60 | 16 | 80 | 6.4 | 38 |
3/4 | 67 | 21 | 90 | 6.4 | 41 |
1 | 76 | 27 | 100 | 6.4 | 57 |
1¼ | 86 | 37 | 110 | 9.7 | 57 |
1½ | 95 | 43 | 125 | 9.7 | 67 |
2 | 140 | 55 | 165 | 12.7 | 57 |
2½ | 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 |
CLASS 1500
Class 1500 Spectacle blind dimensions in mm
Spectacle Blind NPS Dimensions Class 1500 | A | B | C | t | W |
1/2 | 61 | 16 | 80 | 6.4 | 38 |
3/4 | 67 | 21 | 90 | 9.7 | 41 |
1 | 76 | 27 | 100 | 9.7 | 64 |
1¼ | 86 | 35 | 110 | 9.7 | 64 |
1½ | 95 | 41 | 125 | 12.7 | 70 |
2 | 140 | 53 | 165 | 12.7 | 70 |
2½ | 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 |
CLASS 2500
Class 2500 Spectacle blind dimensions in mm
Spectacle Blind NPS Dimensions Class 2500 | A | B | C | t | W |
1/2 | 67 | 16 | 90 | 9.7 | 38 |
3/4 | 73 | 21 | 95 | 9.7 | 41 |
1 | 83 | 27 | 110 | 9.7 | 64 |
1¼ | 102 | 35 | 130 | 12.7 | 64 |
1½ | 114 | 41 | 145 | 15.7 | 70 |
2 | 143 | 53 | 170 | 15.7 | 70 |
2½ | 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 |
ASME B 16.48 spectacle blinds dimension and weight.pdf
This norm covers the dimensions, marking, pressure-temperature ratings, materials, dimensional tolerances and testing for line blanks in sizes between NPS 1/2 and NPS 24 for installation between ASME B16.5 flanges in the classes from 150 to 2500.
FLANGE SPADE AND RING SPACER
A flange spade, otherwise called steel “blanking spade”, or “single-blind”, “blank” or “paddle blind”, is a metallic ring used to isolate a pipe (it has the same scope as a spectacle blind). To close the pipe, the blanking spade is inserted between the flanges; to open the pipe, the spade is removed, and the ring spacer takes its place.
Field staff understands if a pipe is open or closed, as blanking spades have one single signaling hole on the device holder, and ring spacers have instead two holes (look at the image).
Flange spades and ring spacers are manufactured according to the ASME B16.48 specification and belong to the family of pipeline isolation devices.

FLANGE SPADE VS SPECTABLE BLINDS
A spectacle blind combines a flange spade and a ring spacer in a single device (this is the reason why flange spades are called “single-blinds” or “blanks”). The difference is that spectacle blinds may need some space to be rotated, and this space is not always available due to the routing of the piping system. This is when two separate devices are used, as they do not require rotation to be installed.
Spades, ring spacers, and spectacle blinds are available in multiple sizes (from 1/2 inch to 24 inches, and pressure rating from 150 to 2500#) and material grades (the same available for standard flanges) depending on the fluid conveyed by the pipeline.
The difference between spades/ring spacers and spectacle blinds is shown in the image:
FLANGE SPADE AND RING SPACER DIMENSIONS ASME B16.48
CLASS 150
(Dimensions in mm)

NPS | A | B | C | t | W |
1/2 | 45 | 16 | 126 | 3 | 32 |
3/4 | 54 | 21 | 131 | 3 | 32 |
1 | 64 | 27 | 136 | 3 | 32 |
1¼ | 73 | 42 | 145 | 6.4 | 32 |
1½ | 83 | 48 | 145 | 6.4 | 32 |
2 | 102 | 61 | 155 | 6.4 | 32 |
2½ | 107 | 73 | 170 | 6.4 | 32 |
3 | 133 | 89 | 170 | 6.4 | 32 |
3½ | 159 | 102 | 202 | 9.7 | 38 |
4 | 172 | 114 | 202 | 9.7 | 38 |
5 | 194 | 141 | 225 | 9.7 | 38 |
6 | 219 | 168 | 225 | 12.7 | 38 |
8 | 276 | 219 | 267 | 12.7 | 38 |
10 | 337 | 273 | 322 | 15.7 | 44 |
12 | 406 | 324 | 357 | 19.1 | 44 |
14 | 448 | 356 | 378 | 19.1 | 44 |
16 | 511 | 406 | 410 | 22.4 | 44 |
18 | 546 | 457 | 427 | 25.4 | 51 |
20 | 603 | 508 | 455 | 28.4 | 51 |
24 | 714 | 610 | 512 | 31.8 | 51 |
CLASS 300
NPS | A | B | C | t | W |
1/2 | 51 | 16 | 129 | 6.4 | 32 |
3/4 | 64 | 21 | 136 | 6.4 | 32 |
1 | 70 | 27 | 139 | 6.4 | 32 |
1¼ | 79 | 42 | 150 | 6.4 | 32 |
1½ | 92 | 48 | 150 | 6.4 | 32 |
2 | 108 | 61 | 158 | 9.7 | 32 |
2½ | 127 | 73 | 177 | 9.7 | 32 |
3 | 146 | 89 | 177 | 9.7 | 32 |
3½ | 162 | 102 | 205 | 12.7 | 38 |
4 | 178 | 114 | 205 | 12.7 | 38 |
5 | 213 | 141 | 240 | 15.7 | 38 |
6 | 248 | 168 | 240 | 15.7 | 38 |
8 | 305 | 219 | 281 | 22.4 | 38 |
10 | 359 | 273 | 333 | 25.4 | 44 |
12 | 419 | 324 | 363 | 28.4 | 44 |
14 | 483 | 356 | 395 | 31.8 | 44 |
16 | 536 | 406 | 422 | 38.1 | 44 |
18 | 594 | 457 | 450 | 41.1 | 51 |
20 | 651 | 508 | 480 | 44.5 | 51 |
24 | 772 | 610 | 540 | 50.8 | 51 |
CLASS 600
NPS | A | B | C | t | W |
1/2 | 51 | 16 | 129 | 6.4 | 32 |
3/4 | 64 | 21 | 136 | 6.4 | 32 |
1 | 70 | 27 | 139 | 6.4 | 32 |
1¼ | 79 | 37 | 150 | 9.7 | 32 |
1½ | 92 | 43 | 150 | 9.7 | 32 |
2 | 108 | 55 | 158 | 9.7 | 32 |
2½ | 127 | 67 | 177 | 12.7 | 32 |
3 | 146 | 83 | 177 | 12.7 | 32 |
3½ | 159 | 96 | 211 | 15.7 | 38 |
4 | 191 | 108 | 211 | 15.7 | 38 |
5 | 238 | 135 | 248 | 19.1 | 38 |
6 | 264 | 162 | 248 | 22.4 | 38 |
8 | 318 | 212 | 288 | 28.4 | 38 |
10 | 397 | 265 | 352 | 35.1 | 44 |
12 | 454 | 315 | 381 | 41.1 | 44 |
14 | 489 | 346 | 398 | 44.5 | 44 |
16 | 562 | 397 | 435 | 50.8 | 44 |
18 | 610 | 448 | 459 | 53.8 | 51 |
20 | 679 | 497 | 493 | 63.5 | 51 |
24 | 787 | 597 | 547 | 73.2 | 51 |
CLASS 900
NPS | A | B | C | t | W |
1/2 | 60 | 16 | 134 | 6.4 | 32 |
3/4 | 67 | 21 | 137 | 6.4 | 32 |
1 | 76 | 27 | 142 | 6.4 | 32 |
1¼ | 86 | 37 | 151 | 9.7 | 32 |
1½ | 95 | 43 | 151 | 9.7 | 32 |
2 | 140 | 55 | 174 | 12.7 | 32 |
2½ | 162 | 67 | 186 | 12.7 | 32 |
3 | 165 | 83 | 186 | 15.7 | 32 |
4 | 203 | 108 | 217 | 19.1 | 38 |
5 | 244 | 135 | 259 | 22.4 | 38 |
6 | 286 | 162 | 259 | 25.4 | 38 |
8 | 356 | 212 | 307 | 35.1 | 38 |
10 | 432 | 265 | 370 | 41.1 | 44 |
12 | 495 | 315 | 401 | 47.8 | 44 |
14 | 518 | 346 | 412 | 53.8 | 44 |
16 | 572 | 397 | 440 | 60.5 | 44 |
18 | 635 | 448 | 471 | 66.5 | 51 |
20 | 696 | 497 | 501 | 73.2 | 51 |
24 | 835 | 597 | 571 | 88.9 | 51 |
CLASS 1500
NPS | A | B | C | t | W |
1/2 | 61 | 16 | 135 | 6.4 | 32 |
3/4 | 67 | 21 | 137 | 9.7 | 32 |
1 | 76 | 27 | 142 | 9.7 | 32 |
1¼ | 86 | 35 | 151 | 9.7 | 32 |
1½ | 95 | 41 | 151 | 12.7 | 32 |
2 | 140 | 53 | 174 | 12.7 | 32 |
2½ | 162 | 63 | 190 | 15.7 | 32 |
3 | 172 | 78 | 190 | 19.1 | 32 |
4 | 206 | 102 | 219 | 22.4 | 38 |
5 | 251 | 128 | 256 | 28.4 | 38 |
6 | 279 | 154 | 256 | 35.1 | 38 |
8 | 349 | 203 | 303 | 41.1 | 38 |
10 | 432 | 255 | 370 | 50.8 | 44 |
12 | 518 | 303 | 412 | 60.5 | 44 |
14 | 575 | 333 | 442 | 66.5 | 44 |
16 | 638 | 381 | 472 | 76.2 | 44 |
18 | 702 | 429 | 504 | 85.9 | 51 |
20 | 752 | 478 | 530 | 95.3 | 51 |
24 | 899 | 575 | 603 | 111.3 | 51 |
CLASS 2500
NPS | A | B | C | t | W |
1/2 | 67 | 16 | 137 | 9.7 | 32 |
3/4 | 73 | 21 | 140 | 9.7 | 32 |
1 | 83 | 27 | 145 | 9.7 | 32 |
1¼ | 102 | 35 | 161 | 12.7 | 32 |
1½ | 114 | 41 | 161 | 15.7 | 32 |
2 | 143 | 53 | 175 | 15.7 | 32 |
2½ | 165 | 63 | 201 | 19.1 | 32 |
3 | 194 | 78 | 201 | 22.4 | 32 |
4 | 232 | 102 | 232 | 28.4 | 38 |
5 | 276 | 128 | 273 | 35.1 | 38 |
6 | 314 | 154 | 273 | 41.1 | 38 |
8 | 384 | 198 | 321 | 53.8 | 38 |
10 | 473 | 248 | 390 | 66.5 | 44 |
12 | 546 | 289 | 427 | 79.2 | 44 |
6 Responses
Thanks for sharing this amazing content.
how to download in PDF?
D = Hole size (where required) should be the same as the flange bolt hole. In practice, these dimensions have been rounded round off upwards.
Hi, The content is very useful.
May I know for the spectacle blind more than 24″ what standard normally you referring to?
Thanks for this amazing knowledge but ‘D’ dimension not mention here but overall excellent
Very nice information on spectacle blind flange