How 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 1 - How to get high quality Spectacle Blind Flanges?

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.

Spectacle Flange consist of a connected ring (spacer) and a plate (spade).

spectacle flange banner 1 - How to get high quality Spectacle Blind Flanges?

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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.

flg spec blind 1 - How to get high quality Spectacle Blind Flanges?

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

20180128205209 76504 - How to get high quality Spectacle Blind Flanges?

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
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
NPS Outside Ø
A
Inside Ø
B
Center Line
C
THK
t
Web Width
W
20180128205209 76504 - How to get high quality Spectacle Blind Flanges?

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
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
NPS Outside Ø
A
Inside Ø
B
Center Line
C
THK
t
Web Width
W
20180128205209 76504 - How to get high quality Spectacle Blind Flanges?

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
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
NPS Outside Ø
A
Inside Ø
B
Center Line
C
THK
t
Web Width
W
20180128205209 76504 - How to get high quality Spectacle Blind Flanges?

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
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
NPS Outside Ø
A
Inside Ø
B
Center Line
C
THK
t
Web Width
W
20180128205209 76504 - How to get high quality Spectacle Blind Flanges?

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
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
NPS Outside Ø
A
Inside Ø
B
Center Line
C
THK
t
Web Width
W
20180128205209 76504 - How to get high quality Spectacle Blind Flanges?

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
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
NPS Outside Ø
A
Inside Ø
B
Center Line
C
THK
t
Web Width
W
General notes:
  • 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

20180128205404 31262 - How to get high quality Spectacle Blind Flanges?
  • 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: China Spectacle Blind Flanges Manufacturer – Yaang Pipe Industry (www.steeljrv.com)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

Please notice that you might be interested in the other technical articles we’ve published:

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  • What are Spectacle Flanges
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  • Development trend of high pressure pipe fittings
  • How to get high quality flanges
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  • HOW TO GET HIGH QUALITY STEEL PIPES
  • What are socket weld flanges
  • When to use slip on flanges
  • What are slip on flanges
  • WHEN TO USE A SPECTACLE BLIND FLANGE
  • HOW TO GET HIGH QUALITY BOILER TUBES
  • When to use lap joint flange
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  • HOW TO GET HIGH QUALITY ORIFICE FLANGES

  • HOW TO GET HIGH QUALITY SOCKET WELDING FLANGES

References:

  • http://www.wermac.org/flanges/dimensions_spectacle-blind-flanges.html
  • https://www.yaang.com

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