Blind flanges

INTRO

A blind flange is a solid, circular component used to close off the end of a pipeline, valve, or nozzle, effectively halting the flow of fluids or gases. Blind flanges are widely employed across various industries, including oil and gas, chemical processing, and water treatment.

Standard：
GB/T9119-2010 HG/T20592-2009 HG/T20615-2009 DIN ASME BS JIS

Material：
304：F304 S30408 S30408II S30408III S30400
304L：S30403 S30403II 30403 30403II
316L：31603 31603II 31603III
2507（F53） 2205（F51） TP310S（06Cr5Ni20） TP321（06Cr18Ni11） S22053III=2205III T321-32168=321

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DESCRIPTION DOWNLOAD

Manufacturer Intro

Longan Flange is a stainless steel blind flange manufacturer with over 15 years of production experience. We supply blind flanges from DN15 to DN600, covering Class 150 through Class 2500 per ASME B16.5, DIN, and GOST standards. Available in SS304, 304L, 316L, duplex 2205 (F51), and super duplex 2507 (F53). All blind flanges are forged and machined in-house at our Wenzhou facility. Complete blind flange dimensions, including outer diameter, bolt circle, and flange thickness, are listed by pressure class in the tables below. ISO 9001 & PED certified. Quote within 24 hours.

FAQ

What sizes of stainless steel blind flanges do you manufacture?

We manufacture stainless steel blind flanges from DN15 (NPS ½”) to DN300 (NPS 12″) in Class 2500, and up to DN600 (NPS 24″) in lower pressure classes. Custom large-diameter blind flanges up to DN4000 are available on request.

What pressure classes are available for your blind flanges?

Our blind flanges cover Class 150, 300, 600, 900, 1500, and 2500 per ASME B16.5. Complete blind flange dimensions including outer diameter, bolt circle, bolt hole size, and flange thickness are listed in the specification tables above.

Can you supply blind flanges in duplex stainless steel?

Yes. We manufacture blind flanges in duplex 2205 (F51) and super duplex 2507 (F53), as well as SS304, 304L, 316L, TP310S, and TP321. All materials include mill test certificates.

What is the MOQ for blind flanges?

Our minimum order starts from 1 piece for standard sizes. For custom specifications or large-diameter blind flanges, please contact us with your requirements for a quotation within 24 hours.

What certifications do your blind flanges carry?

Our flanges are manufactured in an ISO 9001 and PED certified facility. We provide material test reports per EN 10204 3.1 and can supply additional third-party inspection certificates upon request.

###Class 150###

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	90	60.3	16	4	M14	9.6
20	3/4	100	69.9	16	4	M14	11.2
25	1	110	79.4	16	4	M14	12.7
32	1 1/4	115	88.9	16	4	M14	14.3
40	1 1/2	125	98.4	16	4	M14	15.9
50	2	150	120.7	18	4	M16	17.5
65	2 1/2	180	139.7	18	4	M16	20.7
80	3	190	152.4	18	4	M16	22.3
100	4	230	190.5	18	8	M16	22.3
125	5	255	215.9	22	8	M20	22.3
150	6	280	241.3	22	8	M20	23.9
200	8	345	298.58	22	8	M20	27.0
250	10	405	362.0	26	12	M24	28.6
300	12	485	431.8	26	12	M24	30.2
350	14	535	476.3	30	12	M27	33.4
400	16	595	539.8	30	16	M27	35.0
450	18	635	577.9	33	16	M30	38.1
500	20	700	635.0	33	20	M30	41.3
600	24	815	749.3	36	20	M33	46.1

###CLASS 300###

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	95	66.7	16	4	M14	12.7
20	3/4	115	82.6	18	4	M16	14.3
25	1	125	88.9	18	4	M16	15.9
32	1 1/4	135	98.4	18	4	M16	17.5
40	1 1/2	155	114.3	22	4	M20	19.1
50	2	165	127.0	18	8	M16	20.7
65	2 1/2	190	149.2	22	8	M20	23.9
80	3	210	168.3	22	8	M20	27.0
100	4	255	200.0	22	8	M20	30.2
125	5	280	235.0	22	8	M20	33.4
150	6	320	269.9	22	12	M20	35.0
200	8	380	330.2	26	12	M24	39.7
250	10	445	387.4	30	16	M27	46.1
300	12	520	450.8	33	16	M30	49.3
350	14	585	514.4	33	20	M30	52.4
400	16	650	571.5	36	20	M33	55.6
450	18	710	628.6	36	24	M33	58.8
500	20	775	685.8	36	24	M33	62.0
600	24	915	812.8	42	24	M39X3	68.3

###CLASS 600###

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	95	66.7	16	4	M14	14.3
20	3/4	115	82.6	18	4	M16	15.9
25	1	125	88.9	18	4	M16	17.5
32	1 1/4	135	98.4	18	4	M16	20.7
40	1 1/2	155	114.3	22	4	M20	22.3
50	2	165	127.0	18	8	M16	25.4
65	2 1/2	190	149.2	22	8	M20	28.6
80	3	210	168.3	22	8	M20	31.8
100	4	275	215.9	26	8	M24	38.1
125	5	330	266.7	30	8	M27	44.5
150	6	355	292.1	30	12	M27	47.7
200	8	420	349.2	33	12	M30	55.6
250	10	510	431.8	36	16	M33	63.5
300	12	560	489.0	36	20	M33	66.7
350	14	605	527.0	39	20	M36X3	69.9
400	16	685	603.2	42	20	M39X3	76.2
450	18	745	654.0	45	20	M42X3	82.6
500	20	815	723.9	45	24	M42X3	88.9
600	24	940	838.2	51	24	M48X3	101.6

###CLASS 900###

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	120	82.6	22	4	M20	22.3
20	3/4	130	88.9	22	4	M20	25.4
25	1	150	101.6	26	4	M24	28.6
32	1 1/4	160	111.1	26	4	M24	28.6
40	1 1/2	180	123.8	30	4	M27	31.8
50	2	215	165.1	26	8	M24	38.1
65	2 1/2	245	190.5	30	8	M27	41.3
80	3	240	190.5	26	8	M24	38.1
100	4	290	235.0	33	8	M30	44.5
125	5	350	279.4	36	8	M33	50.8
150	6	380	317.5	33	12	M30	55.6
200	8	470	393.7	39	12	M36X3	63.5
250	10	545	469.9	39	16	M36X3	69.9
300	12	610	533.4	39	20	M36X3	79.4
350	14	640	558.8	42	20	M39X3	85.8
400	16	705	616.0	45	20	M42X3	88.9
450	18	785	685.8	51	20	M48X3	101.6
500	20	855	749.3	55	20	M52X3	108.0
600	24	1040	901.7	68	20	M64X3	139.7

###CLASS 1500###

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	120	82.6	22	4	M20	22.3
20	3/4	130	88.9	22	4	M20	25.4
25	1	150	101.6	26	4	M24	28.6
32	1 1/4	160	111.1	26	4	M24	28.6
40	1 1/2	180	123.8	30	4	M27	31.8
50	2	215	165.1	26	8	M24	38.1
65	2 1/2	245	190.5	30	8	M27	41.3
80	3	265	203.2	33	8	M30	47.7
100	4	310	241.3	36	8	M33	54.0
125	5	375	292.1	42	8	M39X3	73.1
150	6	395	317.5	39	12	M36X3	82.6
200	8	485	393.7	45	12	M42X3	92.1
250	10	585	482.6	51	12	M48X3	108.0
300	12	675	571.5	55	16	M52X3	123.9
350	14	750	635.0	60	16	M56X3	133.4
400	16	825	704.8	68	16	M64X3	146.1
450	18	915	774.7	74	16	M70X3	162.0
500	20	985	831.8	80	16	M76X3	177.8
600	24	1170	990.6	94	16	M90X3	203.2

###CLASS 2500###

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	135	88.9	22	4	M20	30.2
20	3/4	140	95.2	22	4	M20	31.8
25	1	160	108.0	26	4	M24	35.0
32	1 1/4	185	130.2	30	4	M27	38.1
40	1 1/2	205	146.0	33	4	M30	44.5
50	2	235	171.4	30	8	M27	50.9
65	2 1/2	265	196.8	33	8	M30	57.2
80	3	305	228.6	36	8	M33	66.7
100	4	355	273.0	42	8	M39X3	76.2
125	5	420	323.8	48	8	M45X3	92.1
150	6	485	368.3	55	8	M52X3	108.0
200	8	550	438.2	55	12	M52X3	127.0
250	10	675	539.8	68	12	M64X3	165.1
300	12	760	619.1	74	12	M70X3	184.2

Frequently Asked Questions (FAQs)

What is the purpose of a blind flange?

A blind flange is used to seal the end of a pipeline, valve, or pressure vessel, effectively blocking fluid flow and preventing leaks.

Can blind flanges be used for maintenance purposes?

Yes, blind flanges can be easily unbolted to provide access for maintenance, inspection, or cleaning inside the terminal end of the pipe or pressure vessel.

Why are blind flanges sold at a premium cost compared to other flanges?

Although easier to manufacture, blind flanges are sold at a premium due to their high mechanical strength and the specific requirements for bolting forces and pressure resistance.