An '8 blind' or a 'spectacle blind' is a piping fitting that is used for providing positive isolation.
A spectacle blind is basically made up of two metal discs attached to each other by a metal strip as shown in the figure. One is solid disc and the other is hollowed. The hollowed disc allows fluid flow and solid disc is used for positive isolation. You can simply rotate a spectacle blind by 180 degrees to close or open a pipe to allow fluid to pass.
Standard dimensions of spectacle blinds or 8 blinds
These standard dimensions of spectacle blinds are in specified in inches. They are as per as per ASME B16.48.
PIPE
SIZE |
150#
FLANGES |
|||||
A
|
B
|
C
|
D
|
E
|
F
|
|
1/2"
|
5/8
|
1-3/4
|
2-3/8
|
5/8
|
1-1/2
|
1/4
|
3/4"
|
13/16
|
2-1/8
|
2-3/4
|
5/8
|
1-1/2
|
1/4
|
1"
|
1-1/8
|
2-1/2
|
3-1/8
|
9/16
|
1-1/2
|
1/4
|
1-1/4"
|
1-5/8
|
2-7/8
|
3-1/2
|
9/16
|
1-1/2
|
1/4
|
1-1/2"
|
1-7/8
|
3-1/4
|
3-7/8
|
9/16
|
1-1/2
|
1/4
|
2"
|
2-3/8
|
4
|
4-3/4
|
11/16
|
2
|
1/4
|
2-1/2"
|
2-7/8
|
4-3/4
|
5-1/2
|
11/16
|
2
|
1/4
|
3"
|
3-1/2
|
5-1/4
|
6
|
11/16
|
2-1/2
|
1/4
|
3-1/2"
|
4
|
6-1/4
|
7
|
3/4
|
2-1/2
|
3/8
|
4"
|
4-1/2
|
6-3/4
|
7-1/2
|
3/4
|
2-1/2
|
3/8
|
5"
|
5-9/16
|
7-5/8
|
8-1/2
|
7/8
|
3
|
3/8
|
6"
|
6-5/8
|
8-5/8
|
9-1/2
|
7/8
|
3
|
1/2
|
8"
|
8-5/8
|
10-7/8
|
11-3/4
|
7/8
|
3
|
1/2
|
10"
|
10-3/4
|
13-1/4
|
14-1/4
|
1
|
4
|
5/8
|
12"
|
12-3/4
|
16
|
17
|
1
|
4
|
3/4
|
14"
|
14
|
17-5/8
|
18-3/4
|
1-1/8
|
4-1/4
|
3/4
|
16"
|
16
|
20-1/8
|
21-1/4
|
1-1/8
|
4-1/4
|
7/8
|
18"
|
18
|
21-1/2
|
22-3/4
|
1-1/4
|
4-1/2
|
1
|
20"
|
20
|
23-3/4
|
25
|
1-1/4
|
4-3/4
|
1-1/8
|
24"
|
24
|
28-1/8
|
29-1/2
|
1-3/8
|
5-1/2
|
1-1/4
|
Â
PIPE
SIZE |
300#
FLANGES |
|||||
A
|
B
|
C
|
D
|
E
|
F
|
|
1/2"
|
5/8
|
2
|
2-5/8
|
5/8
|
1-1/2
|
1/4
|
3/4"
|
13/16
|
2-1/2
|
3-1/4
|
3/4
|
1-1/2
|
1/4
|
1"
|
1-1/8
|
2-3/4
|
3-1/2
|
11/16
|
1-1/2
|
1/4
|
1-1/4"
|
1-5/8
|
3-1/8
|
3-7/8
|
11/16
|
1-1/2
|
1/4
|
1-1/2"
|
1-7/8
|
3-5/8
|
4-1/2
|
7/8
|
2
|
1/4
|
2"
|
2-3/8
|
4-1/4
|
5
|
3/4
|
2
|
3/8
|
2-1/2"
|
2-7/8
|
5
|
5-7/8
|
7/8
|
2-1/2
|
3/8
|
3"
|
3-1/2
|
5-3/4
|
6-5/8
|
7/8
|
2-1/2
|
3/8
|
3-1/2"
|
4
|
6-3/8
|
7-1/4
|
7/8
|
2-1/2
|
1/2
|
4"
|
4-1/2
|
7
|
7-7/8
|
7/8
|
2-1/2
|
1/2
|
5"
|
5-5/8
|
8-3/8
|
9-1/4
|
7/8
|
3
|
5/8
|
6"
|
6-5/8
|
9-3/4
|
10-5/8
|
7/8
|
3
|
5/8
|
8"
|
8-5/8
|
12
|
13
|
1
|
3-1/2
|
7/8
|
10"
|
10-3/4
|
14-1/8
|
15-1/4
|
1-1/8
|
4
|
1
|
12"
|
12-3/4
|
16-1/2
|
17-3/4
|
1-1/4
|
4
|
1-1/8
|
14"
|
14
|
19
|
20-1/4
|
1-1/4
|
4-3/4
|
1-1/4
|
16"
|
16
|
21-1/8
|
22-1/2
|
1-3/8
|
4-7/8
|
1-1/2
|
18"
|
18
|
23-3/8
|
24-3/4
|
1-3/8
|
4-1/2
|
1-5/8
|
20"
|
20
|
25-5/8
|
27
|
1-3/8
|
4-3/4
|
1-3/4
|
24"
|
24
|
30-3/8
|
32
|
1-5/8
|
5-1/2
|
2
|
Â
PIPE
SIZE |
600#
FLANGES |
|||||
A
|
B
|
C
|
D
|
E
|
F
|
|
1/2"
|
5/8
|
2
|
2-5/8
|
5/8
|
1-1/2
|
1/4
|
3/4"
|
13/16
|
2-1/2
|
3-1/4
|
3/4
|
1-1/2
|
1/4
|
1"
|
1-1/8
|
2-3/4
|
3-1/2
|
3/4
|
2-1/4
|
1/4
|
1-1/4"
|
1-7/16
|
3-1/8
|
3-7/8
|
3/4
|
2-1/4
|
3/8
|
1-1/2"
|
1-11/16
|
3-5/8
|
4-1/2
|
7/8
|
2-5/8
|
3/8
|
2"
|
2-1/8
|
4-1/4
|
5
|
3/4
|
2-1/4
|
3/8
|
2-1/2"
|
2-5/8
|
5
|
5-7/8
|
7/8
|
2-5/8
|
1/2
|
3"
|
3-1/4
|
5-3/4
|
6-5/8
|
7/8
|
2-5/8
|
1/2
|
3-1/2"
|
3-3/4
|
6-1/4
|
7-1/4
|
1
|
3
|
5/8
|
4"
|
4-1/4
|
7-1/2
|
8-1/2
|
1
|
3
|
5/8
|
5"
|
5-1/4
|
9-3/8
|
10-1/2
|
1-1/8
|
3-3/8
|
3/4
|
6"
|
6-3/8
|
10-3/8
|
11-1/2
|
1-1/8
|
3-3/8
|
7/8
|
8"
|
8-3/8
|
12-1/2
|
13-3/4
|
1-1/4
|
3-3/4
|
1-1/8
|
10"
|
10-7/16
|
15-5/8
|
17
|
1-3/8
|
4-1/8
|
1-3/8
|
12"
|
12-3/8
|
17-7/8
|
19-1/4
|
1-3/8
|
4-1/8
|
1-5/8
|
14"
|
13-5/8
|
19-1/4
|
20-3/4
|
1-1/2
|
4-1/2
|
1-3/4
|
16"
|
15-5/8
|
22-1/8
|
23-3/4
|
1-5/8
|
4-7/8
|
2
|
18"
|
17-5/8
|
24
|
25-3/4
|
1-3/4
|
5-1/4
|
2-1/8
|
20"
|
19-5/16
|
26-3/4
|
28-1/2
|
1-3/4
|
5-1/4
|
2-1/2
|
24"
|
23-1/2
|
31
|
33
|
2
|
6
|
2-7/8
|
Â
PIPE
SIZE |
900#
FLANGES |
|||||
A
|
B
|
C
|
D
|
E
|
F
|
|
1/2"
|
0.625
|
2.375
|
3.25
|
-
|
1.50
|
1/4
|
3/4"
|
0.0825
|
2.625
|
3.50
|
0.875
|
1.625
|
1/4
|
1"
|
1.05
|
3.0
|
4.0
|
1.0
|
2.25
|
1/4
|
1-1/4"
|
1.44
|
3.375
|
4.375
|
1.0
|
2.25
|
3/8
|
1-1/2"
|
1.68
|
3.5
|
4.875
|
1.125
|
2.625
|
3/8
|
2"
|
2.16
|
5.5
|
6.5
|
1.0
|
2.25
|
1/2
|
2-1/2"
|
2.64
|
6.375
|
7.5
|
1.125
|
2.625
|
1/2
|
3"
|
3.25
|
6.5
|
7.5
|
1.0
|
2.625
|
5/8
|
4"
|
4.25
|
8.0
|
9.25
|
1.25
|
3.0
|
3/4
|
5"
|
5.3
|
9.625
|
11.0
|
1.375
|
3.375
|
7/8
|
6"
|
6.36
|
11.25
|
12.5
|
1.25
|
3.375
|
1
|
8"
|
8.33
|
14.0
|
15.5
|
1.5
|
3.75
|
1-3/8
|
10"
|
10.42
|
17.0
|
18.5
|
1.5
|
4.125
|
1-5/8
|
12"
|
12.39
|
19.5
|
21.0
|
1.5
|
4.125
|
1-7/8
|
14"
|
13.62
|
20.375
|
22.0
|
1.625
|
4.5
|
2-1/8
|
16"
|
15.62
|
22.5
|
24.25
|
1.75
|
4.875
|
2-3/8
|
18"
|
17.62
|
25.0
|
27.0
|
2.0
|
5.25
|
2-5/8
|
20"
|
19.56
|
27.375
|
29.5
|
2.125
|
5.25
|
2-7/8
|
24"
|
23.5
|
32.875
|
35.5
|
2.625
|
6.0
|
3-1/2
|
Â
PIPE
SIZE |
1500#
FLANGES |
|||||
A
|
B
|
C
|
D
|
E
|
F
|
|
1/2"
|
0.625
|
2.375
|
3.25
|
-
|
1.50
|
1/4
|
3/4"
|
0.82
|
2.625
|
3.50
|
0.875
|
1.625
|
3/8
|
1"
|
1.05
|
3.0
|
4.0
|
1.0
|
2.5
|
3/8
|
1-1/4"
|
1.375
|
3.375
|
4.375
|
1.0
|
2.5
|
3/8
|
1-1/2"
|
1.61
|
3.75
|
4.875
|
1.125
|
2.75
|
1/2
|
2"
|
2.07
|
5.5
|
6.5
|
1.0
|
2.75
|
1/2
|
2-1/2"
|
2.47
|
6.375
|
7.5
|
1.125
|
3.0
|
5/8
|
3"
|
3.07
|
6.75
|
8.0
|
1.25
|
3.0
|
3/4
|
4"
|
4.03
|
8.125
|
9.5
|
1.375
|
3.5
|
7/8
|
5"
|
5.05
|
9.875
|
11.5
|
1.625
|
3.5
|
1-1/8
|
6"
|
6.06
|
11.0
|
12.5
|
1.5
|
3.5
|
1-3/8
|
8"
|
7.98
|
13.75
|
15.5
|
1.75
|
4.0
|
1-5/8
|
10"
|
10.02
|
17.0
|
19.0
|
2.0
|
4.5
|
2
|
12"
|
11.94
|
20.375
|
22.5
|
2.125
|
4.5
|
2-3/8
|
14"
|
13.12
|
22.625
|
25.0
|
2.375
|
5.0
|
2-5/8
|
16"
|
15.0
|
25.125
|
27.75
|
2.625
|
5.25
|
3
|
18"
|
16.88
|
27.625
|
30.5
|
2.875
|
5.75
|
3-3/8
|
20"
|
18.81
|
29.625
|
32.75
|
3.125
|
6.0
|
3-3/4
|
24"
|
22.62
|
35.375
|
39.0
|
3.625
|
7.0
|
4-3/8
|
Â
PIPE
SIZE |
2500#
FLANGES |
|||||
A
|
B
|
C
|
D
|
E
|
F
|
|
1/2"
|
0.625
|
2.625
|
3.5
|
-
|
1.50
|
3/8
|
3/4"
|
0.82
|
2.875
|
3.75
|
0.875
|
1.625
|
3/8
|
1"
|
1.05
|
3.25
|
4.25
|
1.0
|
2.5
|
3/8
|
1-1/4"
|
1.38
|
4.0
|
5.125
|
1.125
|
2.5
|
1/2
|
1-1/2"
|
1.61
|
4.5
|
5.75
|
1.25
|
2.75
|
5/8
|
2"
|
2.07
|
5.625
|
6.75
|
1.125
|
2.75
|
5/8
|
2-1/2"
|
2.47
|
6.5
|
7.75
|
1.25
|
3.0
|
3/4
|
3"
|
3.07
|
7.625
|
9.0
|
1.375
|
3.0
|
7/8
|
4"
|
4.03
|
9.125
|
10.75
|
1.625
|
3.5
|
1-1/8
|
5"
|
5.05
|
10.875
|
12.75
|
1.875
|
3.5
|
1-3/8
|
6"
|
6.06
|
12.375
|
14.5
|
2.125
|
3.5
|
2
|
8"
|
7.81
|
15.125
|
17.25
|
2.125
|
4.0
|
2-1/8
|
10"
|
9.75
|
18.625
|
21.25
|
2.625
|
4.5
|
2-5/8
|
12"
|
11.37
|
21.5
|
24.375
|
2.875
|
4.5
|
3-1/8
|