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Alloy steel spectacle blind flanges, also called figure 8 blinds, are a pair of discs joined by a web. One disc is a solid paddle blank that closes the line, while the other is a paddle spacer ring that leaves it open. They sit between two flanges and are turned to isolate a pipe section for maintenance. These fittings are manufactured from ASTM A182 F5, F9, F11, F22 and F91 alloy steel grades for high-temperature and high-pressure piping. They are made to ASME B16.48. Mating flanges and pressure ratings follow ASME B16.5. Solitaire Overseas ships alloy steel spectacle blind flanges with EN 10204 3.1 certificates and heat number marking for domestic and export orders.
| Parameter | Detail |
|---|---|
|
Product |
Alloy steel spectacle blind (figure 8 blind), paddle blank, paddle spacer |
|
Standard |
ASME B16.48 for line blanks. Mating flanges and pressure ratings per ASME B16.5 |
|
Material |
ASTM A182 F1, F5, F9, F11, F12, F22, F91. Plate grades such as A387 on request |
|
Size range |
Per ASME B16.48 (NPS 1/2 to NPS 24). Larger sizes to drawing |
|
Pressure class |
Class 150, 300, 600, 900, 1500 and 2500 where B16.48 covers the size |
|
Face type |
Raised face (RF), ring type joint (RTJ) where required |
|
Heat treatment |
As required by the grade and the ASTM specification |
|
Testing |
Chemical and mechanical tests, hardness, PMI, UT and MPI on request |
|
Documents |
EN 10204 3.1 MTC, 3.2 with third party inspection on request |
|
Marking |
Class, size, grade and heat number on the web or paddle edge |
| Grade | Carbon (C) | Manganese (Mn) | Phosphorus (P) max | Sulfur (S) max | Silicon (Si) | Chromium (Cr) | Molybdenum (Mo) | Other Elements |
|---|---|---|---|---|---|---|---|---|
|
ASTM A182 F1 |
0.28 max |
0.60 to 0.90 |
0.045 |
0.045 |
0.15 to 0.35 |
Not specified |
0.44 to 0.65 |
Not specified |
|
ASTM A182 F5 |
0.15 max |
0.30 to 0.60 |
0.030 |
0.030 |
0.50 max |
4.00 to 6.00 |
0.44 to 0.65 |
Not specified |
|
ASTM A182 F9 |
0.15 max |
0.30 to 0.60 |
0.030 |
0.030 |
0.50 to 1.00 |
8.00 to 10.00 |
0.90 to 1.10 |
Not specified |
|
ASTM A182 F11 Cl.2 |
0.10 to 0.20 |
0.30 to 0.80 |
0.040 |
0.040 |
0.50 to 1.00 |
1.00 to 1.50 |
0.44 to 0.65 |
Not specified |
|
ASTM A182 F12 Cl.2 |
0.10 to 0.20 |
0.30 to 0.80 |
0.040 |
0.040 |
0.10 to 0.60 |
0.80 to 1.25 |
0.44 to 0.65 |
Not specified |
|
ASTM A182 F22 Cl.3 |
0.05 to 0.15 |
0.30 to 0.60 |
0.040 |
0.040 |
0.50 max |
2.00 to 2.50 |
0.87 to 1.13 |
Not specified |
|
ASTM A182 F91 |
0.08 to 0.12 |
0.30 to 0.60 |
0.020 |
0.010 |
0.20 to 0.50 |
8.00 to 9.50 |
0.85 to 1.05 |
V: 0.18 to 0.25, Nb: 0.06 to 0.10, N: 0.03 to 0.07 |
| Grade | Tensile Strength min MPa (ksi) | Yield Strength min MPa (ksi) | Elongation min % | Hardness HBW |
|---|---|---|---|---|
|
F5 |
485 (70) |
275 (40) |
20 |
217 max |
|
F11 Cl.2 |
485 (70) |
275 (40) |
20 |
143 to 207 |
|
F22 Cl.3 |
515 (75) |
310 (45) |
20 |
156 to 207 |
|
F91 |
585 (85) |
415 (60) |
20 |
190 to 248 |
| Nominal Size (NPS) | Inside Dia / Bore (mm) | Outside Dia (mm) | Center-to-Center (mm) | Thickness (mm) | Web Width (mm) | Approx Weight (kg) |
|---|---|---|---|---|---|---|
|
1/2" |
15.7 |
44.5 |
60.3 |
6.4 |
38.1 |
0.2 |
|
3/4" |
20.8 |
54.0 |
69.9 |
6.4 |
38.1 |
0.3 |
|
1" |
26.7 |
63.5 |
79.4 |
6.4 |
38.1 |
0.4 |
|
1-1/2" |
40.9 |
82.6 |
98.4 |
6.4 |
38.1 |
0.8 |
|
2" |
52.6 |
101.6 |
120.7 |
9.5 |
50.8 |
1.8 |
|
3" |
77.9 |
133.4 |
152.4 |
9.5 |
63.5 |
3.2 |
|
4" |
102.4 |
171.5 |
190.5 |
12.7 |
63.5 |
6.4 |
|
6" |
154.1 |
219.1 |
241.3 |
15.9 |
76.2 |
13.5 |
|
8" |
202.7 |
276.2 |
298.5 |
19.1 |
76.2 |
24.8 |
|
10" |
254.5 |
336.6 |
362.0 |
22.2 |
101.6 |
41.5 |
|
12" |
304.8 |
406.4 |
431.8 |
25.4 |
101.6 |
66.2 |
| Nominal Size (NPS) | Outside Diameter (in / mm) | Center-to-Center (in / mm) | Thickness (in / mm) | Web Width (in / mm) | Approx Weight (kg) |
|---|---|---|---|---|---|
|
1/2" |
2.00 (50.8) |
2.38 (60.3) |
0.25 (6.4) |
1.50 (38.1) |
0.3 |
|
3/4" |
2.50 (63.5) |
2.75 (69.9) |
0.38 (9.5) |
1.50 (38.1) |
0.6 |
|
1" |
2.75 (69.9) |
3.12 (79.4) |
0.38 (9.5) |
1.50 (38.1) |
0.8 |
|
1-1/2" |
3.62 (91.9) |
3.88 (98.4) |
0.50 (12.7) |
1.50 (38.1) |
1.8 |
|
2" |
4.25 (108.0) |
5.00 (127.0) |
0.50 (12.7) |
2.00 (50.8) |
2.6 |
|
3" |
5.75 (146.1) |
6.62 (168.3) |
0.62 (15.7) |
2.50 (63.5) |
5.6 |
|
4" |
7.00 (177.8) |
7.88 (200.2) |
0.75 (19.1) |
2.50 (63.5) |
9.8 |
|
6" |
9.75 (247.7) |
10.62 (269.9) |
0.88 (22.4) |
3.00 (76.2) |
21.0 |
|
8" |
12.00 (304.8) |
13.00 (330.2) |
1.12 (28.4) |
3.50 (88.9) |
40.5 |
A figure-eight plate with a solid paddle blank and an open paddle spacer joined by a web, made from alloy steel to isolate a hot pipe section.
Their two connected discs, the blank and the spacer, look like the number 8.
ASME B16.48 covers line blanks, including spectacle blinds. ASME B16.5 covers the mating flanges and the pressure-temperature ratings.
Use alloy when the pipe and flanges are alloy and run hot, so the blind matches the piping material. For ambient service, carbon steel is usually enough.
Yes. Fit new gaskets whenever the joint is opened, so both faces seal properly. Follow the project procedure for bolt tightening.