SPECTABLE BLINDS

DEFINITION

Spectable blinds, spades and ring spacers are steel products installed between flanges used to isolate sections of a pipeline permanently or for maintenance purposes (example: to replace old gaskets). They are available in a multitude of material grades, from carbon steel to alloy and stainless steel (in specific situations, these devices can also be coated to withstand high corrosion). The reference manufacturing norm is ASME B16.48.

Spectable blind shape  Spectable blinds (also defined "spectable flanges") are manufactured from steel plates of various thicknesses and consists of two interconnected discs: one disc is actually a ring (i.e. a disc with an hole of the same diameter of the pipeline / flange), the other is a solid disc. In normal conditions, spectable blinds are installed in the open position and allow the flow of the fluid normally conveyed by the pipeline. To interrupt the flow and blind the pipeline, spectable blinds have to be rotated to the closed position (this is done by loosening the bolts that keep the two flanges together).  The open and close operation can be generally execute by a single operator. When the spectable blind is in open position, the solid disc appears out of the line; when it is in closed position, the perforated ring appears instead (spectable blinds provide visible shut off).

Spectable blinds are manufactured in three main types: flat, raised and RTJ face.

These products are a very economical solution when compared to the alternative of installing isolation valves. They are rather cheap and have a very long service life. 

 

Spectable blind in open positionSpectable blind

Spectable blind in a open position: the fluid can flow through the pipeline.

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 spectable 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).
 

 Sizes of spectable blinds ASME B16.48.pdf

 

DIMENSIONS OF SPECTABLE BLINDS ASME B16.48

CLASS 150

Spectable blinds dimensions ASME B16.48

NPS 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 

         
           
NPS 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

         
           
NPS 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

         
           
NPS 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

         
           
NPS 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

         
NPS 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

 

 

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