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Dimension of ASME B16.5 Blind Flange

Views: 11 Author: Site Editor Publish Time: 2026-04-09 Origin: Site

In industrial piping systems, there is a seemingly simple yet critical pressure piping component—ASME B16.5 blind flange. It is not only an important part of the piping system but also key to ensuring maintenance safety and system sealing. Today, we will dive into the blind flange as defined by the ASME B16.5 standard, exploring its technical details and wide range of applications.

Appearance Features and Main Uses

blind-flanges asme b16.5

The ASME B16.5 blind flange is manufactured using a forging process, resulting in a solid, disc-like structure. Visually, the most significant difference between a blind flange and other flange types (such as Weld Neck or Slip-On flanges) is the absence of a hole in the center. Unlike weld neck flanges, the blind flange has a relatively simple structure, consisting mainly of a circular metal plate with bolt holes around its periphery for pipeline connections.

Its primary purpose is clear: to seal the end of a pipeline or an unused opening on a vessel. Whether it's a port reserved for future expansion or maintenance, or an unused connection on equipment, the blind flange provides a reliable, removable sealing solution.

Introduction to ASME B16.5 Flange Standard

ASME B16.5 is a core standard developed by the American Society of Mechanical Engineers (ASME) for pipe flanges and flange fittings. This standard covers nominal pipe sizes (NPS) from 1/2 inch to 24 inches and pressure classes from Class 150 to Class 2500. It specifies pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing methods. It is one of the most widely used flange standards in the process industries, including oil & gas, chemical, and power generation.

Specification of Blind Flange

Sealing Faces	Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ)
Size Range	1/2" – 24" / DN15 – DN600
Pressure	Class 150, 300, 400, 600, 900, 1500, 2500 lb
Standards	ASME B16.5, ASME B16.47 Series A/B
Carbon Steel	ASTM A105, 20#
Low-Temp Steel	ASTM A350 LF2, 16Mn
Pipeline Steel	ASTM A694 F42 / 46 / 56 / 60 / 65
Alloy Steel	ASTM A182 F11 / 12 / 5 / 9 / 91 / 92
Stainless Steel	ASTM A182 F304/304L/304H, 316/316L, 310S, 317, 347, 904L
Duplex Steel	ASTM A182 F51, F53, F44

ASME B16.5 Blind Flange: Size Pressure and Sealing Faces

Blind flanges conforming to ASME B16.5 have clearly defined size and pressure specifications.

Size Range

The standard covers sizes from NPS 1/2" to NPS 24". Whether for small-bore instrument lines or large-bore main process pipes, standard dimensions are available. Their thickness and bolt hole patterns strictly follow the standard, ensuring interchangeability and compatibility with other flange types (like Weld Neck or Socket Weld flanges) under the same standard.

Pressure Classes

ASME B16.5 blind flanges are available in seven pressure classes: Class 150, 300, 400, 600, 900, 1500, and 2500. A higher class number indicates a greater pressure-containing capacity. For example, a Class 150 flange has a maximum allowable working pressure of approximately 285 psi at ambient temperature (100°F), while a Class 2500 flange can withstand pressures up to 6175 psi.

Sealing Face Types

SS Blind Flange

To suit different sealing requirements and service conditions, blind flanges can be manufactured with various sealing faces, the most common being Raised Face (RF), Flat Face (FF), and Ring Type Joint (RTJ).

ASME B16.5 Blind Flange Dimensions and Weights

Dimension and Weight of Class 150 Blind Flange

Norminal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	88.9	11.2	35. 10	4	15.7	60.45	0.42
3/4	26.7	98.6	12.7	42.9	4	15.7	69.85	0.61
1	33.4	108	14.2	50.8	4	15.7	79.25	0.86
11/4	42.2	117.3	15.7	63.5	4	15.7	88.9	1.17
11/2	48.3	127	17.5	73. 15	4	15.7	98.6	1.53
2	60.3	152.4	19. 10	91.9	4	19.1	120.7	2.42
21/2	73.0	177.8	22.4	104.6	4	19.1	139.7	3.94
3	88.9	190.5	23.9	127	4	19.1	152.4	4.93
31/2	101.6	215.9	23.9	139.7	8	19.1	177.8	6.17
4	114.3	228.6	23.9	157.2	8	19.1	190.5	7.00
5	141.3	254	23.9	185.7	8	22.4	215.9	8.63
6	168.3	279.4	25.4	215.9	8	22.4	241.3	11.3
8	219.1	342.9	28.4	269.7	8	22.4	298.5	19.6
10	273.0	406.4	30.2	323.9	12	25.4	362	28.8
12	323.8	482.6	31.75	381	12	25.4	431.8	43.2
14	355.6	533.4	35. 10	412.8	12	28.4	476.3	58.1
16	406.4	596.9	36.6	469.9	16	28.4	539.8	76.0
18	457.2	635	39.6	533.4	16	31.75	577.9	93.7
20	508.0	698.5	42.9	584.2	20	31.75	635	122
24	609.6	812.8	47.8	692.2	20	35.1	749.3	185

Class 300 ASME B16.5 Blind Flange

Nominal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	95.2	14.2	35.1	4	15.7	66.55	0.64
3/4	26.7	117.3	15.7	42.9	4	19	82.5	1.11
1	33.4	123.9	17.5	50.8	4	19	88.9	1.39
11/4	42.2	133.3	19	63.5	4	19	98.5	1.79
11/2	48.3	155.4	20.6	73.15	4	22.3	114.3	2.66
2	60.3	165. 1	22.3	91.9	8	19. 10	127	3.18
21/2	73.0	190.5	25.4	104.6	8	22.3	1.493	4.85
3	88.9	209.5	28.4	127	8	22.3	168.1	6.81
31/2	101.6	228.6	30.2	139.7	8	22.3	184.1	8.71
4	114.3	254	31.7	157.2	8	22.3	200.1	11.5
5	141.3	279.4	35	185.7	8	22.3	234.9	15.6
6	168.3	317.5	36.5	215.9	12	22.3	269.7	20.9
8	219. 1	381	41.10	269.7	12	25.4	330.2	34.3
10	273.0	444.5	47.7	323.9	16	28.4	387.3	53.3
12	323.8	520.7	50.8	381	16	31.7	450.8	78.8
14	355.6	584.2	53.8	412.8	20	31.7	514.3	105
16	406.4	647.7	57.15	469.9	20	35	571.5	137
18	457.2	711.2	60.45	533.4	24	35	628.6	175
20	508.0	774.7	63.5	584.2	24	35	685.8	221
24	609.6	914.4	69.85	692.2	24	41. 10	812.8	339

Class 400 BL Flange

Nominal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	95.2	14.2	35. 10	4	15.7	66.55	0.76
3/4	26.7	117.3	15.7	42.9	4	19.1	82.6	1.28
1	33.4	123.9	17.5	50.8	4	19.1	88.9	1.60
11/4	42.2	133.3	20.6	63.5	4	19.1	98.6	2.23
11/2	48.3	155.4	22.3	73. 15	4	22.4	114.3	3.25
2	60.3	165.1	25.4	91.9	8	19.1	127	4.15
21/2	73	190.5	28.4	104.6	8	22.4	149.4	6.13
3	88.9	209.5	31.7	127	8	22.4	168.1	8.44
31/2	101.6	228.6	35	139.7	8	25.4	184.2	11.0
4	114.3	254	35. 10	157.2	8	25.4	200.2	13.7
5	141.3	279.4	38. 10	185.7	8	25.4	235	18.5
6	168.3	317.5	41. 10	215.9	12	25.4	269.7	25.5
8	219.1	381	47.8	269.7	12	28.4	330.2	42.6
10	273	444.5	53.8	323.9	16	31.75	387.4	64.5
12	323.8	520.7	57. 15	381	16	35.1	450.9	94.30
14	355.6	584.2	60.45	412.8	20	35.1	514.4	124
16	406.4	647.7	63.5	469.9	20	38.1	571.5	162
18	457.2	711.2	66.55	533.4	24	38.1	628.7	205
20	508	774.7	69.85	584.2	24	41.1	685.8	254
24	609.6	914.4	76.2	692.2	24	47.8	812.8	386

Class 600 Blind Flange Dimension and Weight

Nominal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	95.2	14.2	35.1	4	15.7	66.55	0.76
3/4	26.7	117.3	15.7	42.9	4	19. 10	82.6	1.28
1	33.4	123.9	17.5	50.8	4	19. 10	88.9	1.60
11/4	42.2	133.3	20.6	63.5	4	19. 10	98.6	2.23
11/2	48.3	155.4	22.3	73.15	4	22.4	114.3	3.25
2	60.3	165. 1	25.4	91.9	8	19. 10	127	4.15
21/2	73	190.5	28.4	104.6	8	22.4	149.4	6.13
3	88.9	209.5	31.7	127	8	22.4	168.1	8.44
31/2	101.6	228.6	35	139.7	8	25.4	184.2	11.0
4	114.3	273. 1	38.1	157.2	8	25.4	215.9	17.3
5	141.3	330.2	44.5	185.7	8	28.4	266.7	29.4
6	168.3	355.6	47.8	215.9	12	28.4	292.1	36.1
8	219. 1	419. 1	55.6	269.7	12	31.75	349.3	58.9
10	273	508	63.5	323.9	16	35. 10	431.8	97.5
12	323.8	558.8	66.55	381	20	35. 10	489	124
14	355.6	603.3	69.85	412.8	20	38. 10	527.1	151
16	406.4	685.8	76.2	469.9	20	41. 10	603.3	214
18	457.2	743	82.6	533.4	20	44.5	654.1	272
20	508.0	812.8	88.9	584.2	24	44.5	723.9	349
24	609.6	939.8	101.6	692.2	24	50.8	838.2	533

Class 900 BL Flange

Nominal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	120.6	22.3	35. 10	4	22.3	82.5	1.77
3/4	26.7	130	25.4	42.9	4	22.3	88.9	2.42
1	33.4	149.3	28.4	50.8	4	25.4	101.6	3.57
11/4	42.2	158.7	28.4	63.5	4	25.4	111.2	4.15
11/2	48.3	177.8	31.7	73. 15	4	28.4	123.9	5.75
2	60.3	215.9	38. 10	91.9	8	25.4	165.1	10.1
21/2	73	244.3	41. 10	104.6	8	28.4	190.5	14.0
3	88.9	241.3	38. 10	127	8	25.4	190.5	13.1
4	114.3	292.1	44.5	157.2	8	31.7	234.9	26.9
5	141.3	349.2	50.8	185.7	8	35	279.4	36.5
6	168.3	381	55.6	215.9	12	31.7	317	47.40
8	219.1	469.9	63.5	269.7	12	38.1	393.7	82.5
10	273	546.1	69.85	323.9	16	38.1	469.9	122
12	323.8	609.6	79.25	381	20	38.1	533.4	173
14	355.6	641.3	85.8	412.8	20	41.1	558.8	206
16	406.4	704.8	88.9	469.9	20	44.4	615.9	259
18	457.2	787.4	101.6	533.4	20	50.8	685.8	367
20	508	857.2	107.9	584.2	20	53.8	749.3	463
24	609.6	1041.4	139.7	692.2	20	66.55	901.7	876

Blind Flange of Class 1500

Nominal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	120.6	22.3	35.1	4	22.3	82.5	1.77
3/4	26.7	130	25.4	42.9	4	22.3	88.9	2.42
1	33.4	149.3	28.4	50.8	4	25.4	101.6	3.57
11/4	42.2	158.7	28.4	63.5	4	25.4	111.2	4.15
11/2	48.3	177.8	31.7	73.15	4	28.4	123.9	5.75
2	60.3	215.9	38.1	91.9	8	25.4	165.1	10.1
21/2	73	244.3	41.1	104.6	8	28.4	190.5	14.0
3	88.9	266.7	47.7	127	8	31.7	203.2	19.1
4	114.3	311.1	53.8	157.2	8	35	241.3	29.9
5	141.3	374.6	73.15	185.7	8	41.1	292.1	58.4
6	168.3	393.7	82.5	215.9	12	38.1	317.5	71.8
8	219. 1	482.6	91.9	269.7	12	44.4	393.7	122
10	273	584.2	107.9	323.9	12	50.8	482.6	210
12	323.8	673. 1	123.9	381	16	53.8	571.5	316
14	355.6	749.3	133.3	412.8	16	60.45	635	420
16	406.4	825.5	146	469.9	16	66.55	704.8	558
18	457.2	914.4	162	533.4	16	73. 15	774.7	760
20	508	984.2	177.8	584.2	16	79.25	831.8	965
24	609.6	1168.4	203.2	692.2	16	91.9	990.6	1558

Class 2500 ASME B16.5 BL Flange

Nominal Pipe Size		A	C	G	H	I	J	Weight
inch	mm	mm	mm	mm	Holes	mm	mm	kg / piece
1/2	21.3	133.4	30.2	35. 10	4	22.4	88.9	2.99
3/4	26.7	139.7	31.7	42.9	4	22.4	95.3	3.50
1	33.4	158.8	35. 10	50.8	4	25.4	108	4.96
11/4	42.2	184.2	38. 10	63.5	4	28.4	130	7.35
11/2	48.3	203.2	44.5	73. 15	4	31.75	146.1	10.4
2	60.3	235	50.8	91.9	8	28.4	171.5	15.6
21/2	73	266.7	57. 15	104.6	8	31.75	196.9	22.6
3	88.9	304.8	66.55	127	8	35.1	228.6	34.8
4	114.3	355.6	76.2	157.2	8	41.1	273.1	53.9
5	141.3	419.1	91.9	185.7	8	47.88	323.9	90.8
6	168.3	482.6	108	215.9	8	53.8	368.3	141
8	219.1	552.5	127	269.7	12	53.8	438.2	214
10	273	673.1	165.1	323.9	12	66.55	539.8	411
12	323.8	762	184.2	381	12	73.15	619.3	592

Applications

Due to their reliable sealing performance and standardized design, ASME B16.5 blind flanges are used across virtually every industrial sector.

Equipment Manufacturing & Vessel Openings

Used on pressure vessels like reactors, storage tanks, and heat exchangers to seal process openings or manholes that are not permanently connected.

Permanent Pipeline End Sealing

Used to temporarily or permanently cap the end of a pipe branch reserved for future expansion.

Pressure Testing & System Checks

Installed to seal off a piping system after construction or repair, allowing hydrostatic or pneumatic tests to verify system strength and tightness.

Maintenance & Safety Isolation

During equipment maintenance, a blind flange is installed downstream of a shut-off valve. This creates a positive, absolute physical isolation, preventing media from leaking past the valve and entering the work area. It serves as the "final line of defense" for the safety of maintenance personnel.

With its simple structure, robust pressure resistance, and standardized dimensions, the ASME B16.5 blind flange plays a critical role in industrial piping systems. Understanding its dimensional specifications and pressure classes is essential for ensuring the safe and reliable operation of your piping system.