Where to get high quality Spectacle Blind Flanges?

2018-03-22

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.

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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.

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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 - Where 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

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
1¼	73	42	90	6.4	38
1½	83	48	100	6.4	38
2	102	61	120	6.4	51
2½	107	73	140	6.4	51
3	133	89	150	6.4	64
3½	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

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
1¼	79	42	100	6.4	38
1½	92	48	115	6.4	38
2	108	61	125	9.7	51
2½	127	73	150	9.7	51
3	146	89	170	9.7	64
3½	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

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
1¼	79	37	100	9.7	57
1½	92	43	115	9.7	67
2	108	55	125	9.7	57
2½	127	67	150	12.7	67
3	146	83	170	12.7	67
3½	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

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
1¼	86	37	110	9.7	57
1½	95	43	125	9.7	67
2	140	55	165	12.7	57
2½	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

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
1¼	86	35	110	9.7	64
1½	95	41	125	12.7	70
2	140	53	165	12.7	70
2½	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

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
1¼	102	35	130	12.7	64
1½	114	41	145	15.7	70
2	143	53	170	15.7	70
2½	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 - Where 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: Network Arrangement – China Spectacle Blind Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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