Where to get high quality Spectacle Blind Flanges?
What is a Spectacle Blind Flange?
A spectacle blind flange – also known as a figure-8 blind – is generally a piece of metal that is cut to fit between two pipe flanges and usually sandwiched between two gaskets. A spectacle blind is often made from two metal discs that are attached to each other by a small section of steel.
Spectacle blind flange spacers
The shape is similar to a pair of glasses or “spectacles” – hence the name spectacle blind. One end of the blind will have an opening to allow flow through the pipe during operation and the other end is solid to block flow during maintenance. They are generally installed as a permanent device to separate process piping systems.
The whole idea of a spectacle blind is so that one can be absolutely sure that an item of equipment is properly and securely blanked off with no possibility of any flow or leakage through a valve during maintenance. The flow can be diverted to other items of equipment but not just bypassed around the blank as this would compromise the safety function of the spectacle blind. The flow has to valved off and pressure relieved prior to loosening flange bolts and swinging the blind.
Spectacle Blind Flange is generally a piece of metal that is cut to fit between two pipe flanges and usually sandwiched between two gaskets. A spectacle blind is often made from two metal discs that are attached to each other by a small section of steel. The shape is similar to a pair of glasses or “spectacles” – hence the name spectacle blind. One end of the blind will have an opening to allow flow through the pipe during operation and the other end is solid to block flow during maintenance. They are generally installed as a permanent device to separate process piping systems.
The whole idea of a spectacle blind is so that one can be absolutely sure that an item of equipment is properly and securely blanked off with no possibility of any flow or leakage through a valve during maintenance. The flow can be diverted to other items of equipment but not just bypassed around the blank as this would compromise the safety function of the spectacle blind. The flow has to valved off and pressure relieved prior to loosening flange bolts and swinging the blind.
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Spectacle blinds
Spectacle Blinds are generally applied to permanently separating pipesystems, or just to connect with each other. A Spectacle Blind is a steel plate cut into two discs of a certain thickness.
The two discs are attached to each other by section of steel similar to the nose piece of a pair of glasses. One of the discs is a solid plate, and the other is a ring, whose inside diameter is equal to that of a flange.
Spectacle Blinds be applied in systems, which regularly need to be separated from other installations. Normally, a Spectacle Blind is mounted in the “open” position so that flow through the pipe is possible. If the Spectacle Blind in the “close” position is rotated, the pipe is blanked off and no flow is possible.
Maintenance on a pipesystem can be a reason to rotate the spectacle in the “close” position. This run will take place through the hole, that is drilled in the connection piece. By loosening of all bolts, and partial removal of their, the Spectacle Blind can be rotated. After replacing the gaskets (new gaskets are to recommend), the bolts can be re-assembled and tightened.
Types of spectacle flanges
A spectacle blind flange is generally a piece of metal that is cut to fit between two pipe flanges and usually sandwiched between two gaskets.There are three types of spectacle flange:
First one is spectacle blind flange (also called figure 8 flange),it’s the most regular spectacle flange.The shape of spectacle flange is like glasses.One part is a blind plate,the other part is a ring which has a same outer diameter with the first part.The two parts are connected with a handle plate.The spectacle blind flange could be produced from one plate,or joint together by welding from three parts:blind plate,ring and handle plate.
The second type of spectacle flange is called spade,or paddle flange.It’s a blind plate with a handle plate.It has a same usage with the blind part of a spectacle blind flange.
The third type of spectacle flange is called spacer,it looks like a steel ring with a handle plate.The spacer has a same usage with the ring part of a spectacle flange.The spacer has a same outer diameter with the paddle flange.
These Flanges are available in the following range.
Stainless Steel: ASTM a182 F304, F304L, F304H, F316, F316L, F316Ti, F310, F310S, F321, F321H, F317, F347, F347H, F904L.
Duplex Stainless Steel: UNS S31803, UNS S32750
Carbon Steel: ASTM a105,
Alloy Steel: ASTM a182 F1, F11, F22, F5, F9, F91
Nickel Alloys: Monel 400 & 500, Inconel 600 & 625, Incoloy 800, 825, Hastelloy C22, C276
Copper Alloys: Copper, Brass & Gunmetal
Size: 1/8″ NB TO 48″NB.
Class: 150#, 300#, 400#, 600#, 900#, 1500#, 2500#
Dimensional Standard
ANSI: ANSI B16.5, ANSI B16.47, MSS SP44, ANSI B16.36, ANSI B16.48
DIN: DIN 2527, DIN 2566, DIN 2573, DIN 2576, DIN 2641, DIN 2642, DIN 2655, DIN 2656, DIN 2627, DIN 2628, DIN 2629, DIN 2631, DIN 2632, DIN 2633, DIN 2634, DIN 2635, DIN 2636, DIN 2637, DIN 2638, DIN 2673
B.S: BS 4504, BS4504, BS1560, BS10
Dimensions of spectacle blinds according to ASME B16.48
Dimensions of spectacle blinds according to ASME B16.48 for installation between ASME B16.5 flanges.
Dimensions Spectacle Blinds – ASME B16.48
Pressure Class 150
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 |
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 |
NPS |
Outside Ø A |
Inside Ø B |
Center Line C |
THK t |
Web Width W |
Pressure Class 300
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 | 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 |
NPS |
Outside Ø A |
Inside Ø B |
Center Line C |
THK t |
Web Width W |
Pressure Class 600
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 |
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 |
NPS |
Outside Ø A |
Inside Ø B |
Center Line C |
THK t |
Web Width W |
Pressure Class 900
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 |
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 |
NPS |
Outside Ø A |
Inside Ø B |
Center Line C |
THK t |
Web Width W |
Pressure Class 1500
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 |
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 |
NPS |
Outside Ø A |
Inside Ø B |
Center Line C |
THK t |
Web Width W |
Pressure Class 2500
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 |
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 |
NPS |
Outside Ø A |
Inside Ø B |
Center Line C |
THK t |
Web Width W |
- Dimensions are in millimeters unless otherwise indicated.
- D = Hole size (where required) should be the same as the flange bolt hole. In practice, these dimensions have been rounded round off upwards.
- Wt = Thickness of the web (or tie bar) should be 6 mm minimum, or equal to Thickness (t) if less than 6 mm.
- Spectacle Blinds should be made from a plate or forging specification, approved for use by ASME B31.3, of essentially the same chemical composition as the mating flanges and piping involved.
- Spectacle Blinds according to ASME B16.48 may be used for installation between ASME B16.5 flanges
- Depending on a customer specification, some dimensions can be different from what on this page is defined.
REMARK(S) OF THE AUTHOR…
RAISED FACE JOINT BLANKS
- ASME B16.48 says: The gasket seating surface finish and dimensions for raised face line blanks shall be in accordance with ASME B16.5. A raised face may be specified at the option of the purchaser.
- A Raised Face would add machining time and complexity so the price would be higher. Call this the Bugatti or Rolls Royce of the line blind world.
- Personally, I have seen that version once or twice somewhere. The version without Raised Face is the default and is used everywhere.
Material Symbol | C | Mn | P | S | Si | Ni | Cr | Mo | Cu | N | V | Co |
ASTM A105 | 0.35 | 0.60-1.05 | 0.035 | 0.04 | 0.10-0.35 | 0.4 | 0.3 | 0.12 | 0.4 | _ | 0.08 | _ |
ASTM A350 LF2 | 0.3 | 0.60-1.35 | 0.035 | 0.04 | 0.15-0.30 | 0.4 | 0.3 | 0.12 | 0.4 | _ | 0.08 | 0.02 |
ASTM A182 F304 | 0.08 | 2 | 0.045 | 0.03 | 1 | 8.0-11.0 | 18.0-20.0 | _ | _ | _ | _ | _ |
ASTM A182 F304L | 0.03 | 2 | 0.045 | 0.03 | 1 | 8.0-13.0 | 18.0-20.0 | _ | _ | _ | _ | _ |
ASTM A182 F316 | 0.08 | 2 | 0.045 | 0.03 | 1 | 10.0-14.0 | 16.0-18.0 | 2.00-3.00 | _ | _ | _ | _ |
ASTM A182 F316L | 0.03 | 2 | 0.045 | 0.03 | 1 | 10.0-15.0 | 16.0-18.0 | 2.00-3.00 | _ | _ | _ | _ |
ASTM A182 F321 | 0.08 | 2 | 0.045 | 0.03 | 1 | 9.0-12.0 | 17.0-19.0 | _ | _ | _ | _ | _ |
EN 10025 S235JR | 0.2 | 1.4 | 0.045 | 0.045 | _ | _ | _ | _ | _ | 0.01 | _ | _ |
20Mn | 0.17-0.23 | 0.70-1.00 | 0.035 | 0.035 | 0.17-0.37 | 0.3 | 0.25 | 0.25 | ||||
20 | 0.17-0.23 | 0.60-1.00 | 0.03 | 0.02 | 0.17-0.37 | 0.25 | 0.25 | 0.25 | ||||
16Mn | 0.13-0.19 | 1.20-1.60 | 0.03 | 0.02 | 0.20-0.60 | 0.3 | 0.3 | 0.25 |
Material Symbol | Tensile Strength, min, MPa | Yield point, min, Mpa | Elongation, min, % | Reduction of area, min, % | Hardness, max, HB | Min. Impact | Test Temperature, °C |
ASTM A105 | 485 | 250 | 22 | 30 | 187 | ||
ASTM A350 LF2 | 485-655 | 250 | 22 | 30 | 20 | -46 | |
ASTM A182 F304 | 515 | 205 | 30 | 50 | |||
ASTM A182 F304L | 485 | 170 | 30 | 50 | |||
ASTM A182 F316 | 515 | 205 | 30 | 50 | |||
ASTM A182 F316L | 485 | 170 | 30 | 50 | |||
ASTM A182 F321 | 515 | 205 | 30 | 50 | |||
20Mn | 450 | 275 | 24 | 50 | 197 | ||
20 | 410 | 245 | 25 | 55 | 156 |
How to use a spectacle blind flange?
The spectacle blind flanges have three types: spacer, spade (paddle flange), spectacle blind flange. A spectacle blind flange is a combination of a spade and a spacer.
All these three types of spectacle blind flanges are used in piping systems or pressure vessels where the flow needs to be interrupted from time to time.They are installed between one pair of pipe flanges and able to rotate or ‘swing’ into and out of position to interrupt or allow the flow,they are used in the piping system as “Open” and “Closed” function.
Maintenance on a pipe system can be a reason to temporarily replace a ring spacer for a spade.By loosening of all bolts,and half of the bolts temporarily remove,the spade or spacer can be placed.After replacing the gaskets,the bolts can be re-assembled and tightened.It is necessary that the pipeline should be valved off and pressure relieved before loosening the flange bolts.
To prevent unnecessary weight to a flange connections,designer usually will choose the seperated two parts(spacer and spade) instead of the spectacle blind flange.
When to use a spectacle blind flange?
Spectacle blind flange be applied in systems, which regularly need to be separated from other installations. Normally, a Spectacle blind flange is mounted in the “open” position so that flow through the pipe is possible. If the Spectacle Blind in the “close” position is rotated, the pipe is blanked off and no flow is possible.
Maintenance on a pipe system can be a reason to temporarily replace a Ring Spacer flange for a Spade flange. By loosening of all bolts, and half of the bolts temporarily remove, the Spade or Spacer can be placed. After replacing the gaskets,the bolts can be re-assembled and tightened. It is necessary that the pipeline should be valved off and pressure relieved before loosening the flange bolts.
To prevent unnecessary weight to a flange connections,designer usually will choose the seperated two parts (spacer flange and spade flange) instead of the spectacle blind flange.
Source: Network Arrangement – China Spectacle Blind Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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References:
- http://www.wermac.org/flanges/dimensions_spectacle-blind-flanges.html
- https://www.yaang.com
- https://www.steeljrv.com