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Spectacle Blind Flange

Spectacle Blind Flange

spectacle-blind-flange

It 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.

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

p_l_10_1-150x150

DIMENSIONS OF CLASS 150 FLANGES AS PER ANSI B 16.48

NB

a

B

C

D

E

T1

T2

½”

15

48

14

60

 

26

5

4

¾”

20

57

21

70

 

32

5

4

1”

25

67

27

79

 

38

5

4

1 ½”

40

86

41

98

 

52

5

4

2”

50

105

52

120

20

64

6

4

3”

80

137

78

152

20

86

8

6

4”

100

175

103

190

20

114

9

7

6”

150

222

154

241

22

148

12

10

8”

200

279

203

298

22

188

15

12

10”

250

340

254

362

26

154

18

15

12”

300

410

303

432

26

190

21

18

14”

350

451

343

476

30

208

23

20

16”

400

515

394

540

30

176

25

23

18”

450

550

445

578

33

188

28

26

20”

500

605

495

635

33

162

31

29

24”

600

720

597

749

36

194

37

34

DIMENSIONS OF CLASS 300 FLANGES AS PER ANSI B 16.48

NB

a

B

C

D

E

T1

T2

½”

15

54

14

66

 

30

5

4

¾”

20

67

21

83

 

36

5

4

1”

25

73

27

89

 

42

5

4

1 ½”

40

95

41

114

 

58

7

5

2”

50

111

52

127

20

68

8

6

3”

80

149

78

168

22

96

11

8

4”

100

181

103

200

22

118

13

10

6”

150

251

154

270

22

112

18

15

8”

200

308

203

330

26

138

23

19

10”

250

362

254

387

30

118

27

24

12”

300

422

303

451

33

138

32

28

14”

350

486

343

514

33

124

35

33

16”

400

540

394

571

36

140

39

37

18”

450

595

445

628

36

126

44

42

20”

500

655

495

686

36

140

49

47

24”

600

775

597

813

42

168

58

56

DIMENSIONS OF CLASS 600 FLANGES AS PER ANSI B 16.48

NB

a

B

C

D

E

T1

T2

½”

15

54

14

66

 

30

5

4

¾”

20

67

21

82

 

36

6

4

1”

25

73

27

89

 

42

7

4

1 ½”

40

95

41

114

 

58

9

6

2”

50

111

52

127

20

68

11

8

3”

80

149

78

168

22

96

15

12

4”

100

194

103

216

26

126

18

15

6”

150

267

154

292

30

116

24

21

8”

200

321

203

349

33

140

31

27

10”

250

400

254

432

36

128

38

33

12”

300

457

303

489

36

114

44

39

14”

350

492

343

527

39

122

48

44

16”

400

565

394

603

42

144

55

53

18”

450

613

445

654

45

155

62

60

20”

500

682

495

724

45

140

68

67

24”

600

790

597

838

52

164

81

80

All dimensions are in millimeters unless otherwise indicated.

General notes:
• D = Hole size (where required) should be the same as the flange bolt hole. In
practice, these dimensions have been rounded round off upwards.
• T1 = Thickness Carbon Steel.
• T2 = Thickness Stainless Steel.
• W = Thickness of the web (or tie bar) should be 0.25 inch (6 mm) minimum, or
equal to T1 and T2 if less than 0.25 inch (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.
• Depending on a customer specification, the dimensions can be different from
what on this page is defined.

About NCTV

www.yaang.com provide a wide range of steel products as Steel pipe, Steel pipes and seamless pipes, Alloy pipes, Pipe fittings, Composite steel pipe used in the industry, construction etc.

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