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Spectacle Blind, Flange Spade, Ring Spacer (ASME B16.48)

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.

spectable blind

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.

In normal conditions, spectacle blinds are installed in the open position and do not interrupt the flow of the fluid conveyed by the pipeline.
To blind the pipeline, and interrupt the flow, the site staff has simply to unscrew the flange bolts and rotate the spectacle blind to its closed position.

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.

Spectable blinds for pipelines opening and closing
Spectacle blind in an open position: the conveyed fluid can flow through the pipeline. As the disc is rotated, the flow is interrupted.
These products are available in most diameters, from 1/2 to 36 inch generally, and in pressure classes from 150 to 600 pounds (for RTJ flanges, the common pressure ranges are between 300 and 2500 pounds).

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.

types of spectable blinds

SPECTACLE BLIND DIMENSIONS in MM ASME B16.48

Spectable blind sizes

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
73 42 90 6.4 38
83 48 100 6.4 38
2 102 61 120 6.4 51
107 73 140 6.4 51
3 133 89 150 6.4 64
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

Spectable blind sizes

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
79 42 100 6.4 38
92 48 115 6.4 38
2 108 61 125 9.7 51
127 73 150 9.7 51
3 146 89 170 9.7 64
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

Spectable blind sizes

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
79 37 100 9.7 57
92 43 115 9.7 67
2 108 55 125 9.7 57
127 67 150 12.7 67
3 146 83 170 12.7 67
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

Spectable blind sizes

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
86 37 110 9.7 57
95 43 125 9.7 67
2 140 55 165 12.7 57
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

Spectable blind sizes

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
86 35 110 9.7 64
95 41 125 12.7 70
2 140 53 165 12.7 70
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

Spectable blind sizes

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
102 35 130 12.7 64
114 41 145 15.7 70
2 143 53 170 15.7 70
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

Spectable blind dimensions and weights ASME B16.48
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 and ring spacer
Ring spacer (left) and blanking spade (right)

 

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:

difference spade and spectable blind

 

FLANGE SPADE AND RING SPACER DIMENSIONS ASME B16.48

CLASS 150

(Dimensions in mm)

Flange spade and ring spacer
Flange spade and ring spacer

 

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
73 42 145 6.4 32
83 48 145 6.4 32
2 102 61 155 6.4 32
107 73 170 6.4 32
3 133 89 170 6.4 32
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

Flange spade and ring spacer

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
79 42 150 6.4 32
92 48 150 6.4 32
2 108 61 158 9.7 32
127 73 177 9.7 32
3 146 89 177 9.7 32
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

Flange spade and ring spacer

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
79 37 150 9.7 32
92 43 150 9.7 32
2 108 55 158 9.7 32
127 67 177 12.7 32
3 146 83 177 12.7 32
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

Flange spade and ring spacer

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
86 37 151 9.7 32
95 43 151 9.7 32
2 140 55 174 12.7 32
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

Flange spade and ring spacer

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
86 35 151 9.7 32
95 41 151 12.7 32
2 140 53 174 12.7 32
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

Flange spade and ring spacer

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
102 35 161 12.7 32
114 41 161 15.7 32
2 143 53 175 15.7 32
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

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