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.

+ A figure-8 blank

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.

Specifications:

• Size: 1/2” to 60”, DN 12mm to DN 1500mm
• Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250
• Facing: RF / RTJ

Material: 

• Cabon steel: A105, A350 LF2
• Stainless steel: A182 F304/F304L/F316/F316L/F321
• Alloy steel: F11, F12

Packing: plywood case and plywood pallet

Keywrods: Spectacle Blind Flanges, Spectacle Blind Flange, Spectacle Flanges, Spectacle Blind Flanges manufactory




Standards, Dimensions & Weight ASME B16.48 Class 150 ASME B16.48 Class 300 ASME B16.48 Class 600 ASME B16.48 Class 900 ASME B16.48 Class 1500 ASME B16.48 Class 2500

Key Features:
Can be attached to the pipe without welding (sometimes an additional seal weld is used as well)
Ideal for higher pressure and temperature applications for small pipe sizes
Not recommended for larger loads, especially when subjected to higher torque

Uses of threaded flanges:
Threaded flanges can be fitted to pipes of various sizes without welding and this is one chief benefit for which these flanges are highly demanded. They can be used in extremely high pressure applications, particularly at or near atmospheric temperature, where the necessary post weld heat treatment is not possible.

They are ideal for small diameter piping applications.
They are economical and time saving devices.
These threaded flanges are normally designed for non-cyclic applications.
The flanges are suitable to be used in applications where welding is hazardous.
They can be used in highly explosive areas.
These types of flanges are made from plate, and come in 3 different types.

The first and most widely used type are spec blinds – short for spectacle: these are flanges with two equal outside diameter (OD) parts welded together by way of a ‘bridge’. One of the parts also contains an inside diameter (ID), while the other is a blank, or blind. A whole is put at the halfway mark of the bridge. These are also called spectacles, figure 8’s, and figure 8 blanks, because of their resemblance to reading glasses (spectacles) and figure 8’s. These are referred to as ‘Line Blanks’ in the ASME/ANSI standards.

The second and third types are quite similar: both have longer bridges, referred to as ‘paddles’, which resemble longer handles. One type has only an OD, and so is a blind plate – similar in appearance to a large pizza oven peel. These are referred to as paddle blinds. The other type is exactly the same but comes with an ID as well, enabling flow-through when installed in a piping system. These pieces have holes in the paddle which enables field personnel to determine by sight which piece is installed in a system. These are referred to as paddle spacers, and are often supplied in sets together with the paddle blinds.

All 3 types of these flanges are used in piping systems or pressure vessels where the flow needs to be interrupted from time to time. They are installed between two pipe flanges (as specified above), and by way of a screw inserted into the hole in the bridge or paddle, they are able to rotate or ‘swing’ into and out of position to interrupt or allow the flow, as the user sees fit. Our spec blind flanges are available with raised, flat, or RTJ faces.

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 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.