Flat Flanges | EN 1092-1 Type 01 | DIN 2573

PM Industries manufactures, supplies, and stocks Flat Flanges in a range of materials, pressure ratings, and pipe sizes. A flat flange, also called a flat face flange, has a sealing face that is machined flush with the front face of the flange across its full diameter. That full-face contact area distributes gasket load evenly across the entire flange surface, which is what makes flat face flanges the standard connection type when mating to cast iron, ductile iron, and non-metallic flanged equipment where the flange material is brittle and concentrated bolt load would cause cracking.

The design is intentionally simple. No raised ring, no groove, no specialized gasket profile required. A full-face gasket spanning the entire flange face with bolt holes cut in completes the assembly. That simplicity keeps both the component cost and the assembly complexity low, which is why flat flanges remain the standard in water treatment, HVAC, and general utility piping where service conditions don't demand the more complex geometry of raised face or ring type joint connections.

Cast iron equipment compatibility is the primary engineering reason flat face flanges are specified rather than raised face flanges in certain applications. When a raised face stainless or carbon steel flange is bolted to a flat face cast iron pump or valve body, the raised ring concentrates bolt load on the inner portion of the cast iron face. That concentrated load can crack the brittle cast iron body over time, particularly as bolts are re-torqued during maintenance. Flat face flanges eliminate that risk by spreading the load across the full mating surface.

Flat flanges are also specified in fiberglass-reinforced plastic (FRP) and other composite piping systems, where the same concern about concentrated load on brittle facing material applies. Water treatment plants, chemical plants using FRP piping, and utilities systems with cast iron valve bodies are consistent users of flat face flanges for that reason.

Alignment during installation is straightforward. The flat face provides a clear visual reference for gasket positioning, and there's no raised ring to fit a gasket around or seat into a groove. For installation crews working on large-diameter connections or awkward field locations, that simplicity reduces fitting errors and speeds assembly.

Flat flanges are available in carbon steel (A105), stainless steel (304L, 316L, 321), duplex stainless (2205), and nickel alloy grades across a range of pressure classes and pipe sizes with full material certification to applicable ASME, ASTM, and relevant standards. Contact PM Industries for material selection, dimensions, and pricing.

Specification Flat Flange

Standards	ANSI/ASME B16.5, B16.48, GOST, DIN, EN-1092, B16.47 Series A & B, AWWA, BS Flanges
JIS Standard	5K, 10K, 16K, 20K, 30K, 40K, 63K
DIN Flanges	DIN 2527, 2627, 2631, 2656, 2576, 2673, 2629, 2628, 2566

Flanges are Available in Following Materials

Stainless Steel	SS 201, SS 202, SS 301, SS 304, SS 304L, SS 310, SS 310S, SS 316L, SS 316TI, SS 317, SS 317L, SS 321, SS 347, SS 409, SS 409M, SS 409L, SS 410, SS 410S, SS 420, SS 430, SS 431, SS 441, SS 444, SS 446, SS 17-4PH, SS 904L.
Duplex Steel	UNS S32205, UNS S31803 Flange
Super Duplex Steel	UNS S32750, UNS S32760 Flanges
Carbon Steel	Carbon steel A105 Flanges, A36 Flanges, IS 2062 Flanges, A350 LF2 Flanges, F42 Flanges, F52 Flanges, F56 Flanges, F60 Flanges, F65 Flanges, F70 Flanges, F80 Flanges, IBR flanges, A694 Flanges, SS400, SF440, ST37-2 Flanges, S235JrG2 Flanges, P250GH Flanges, C22.8 Flanges, etc.
Alloys Steel	Alloy 20, F1, F5, F9, F11, F22, F91 Flanges
Copper Alloys	Cu-Ni 70/30, Cu-Ni 90/10, C 24000, C 75700, C 51100, C 22000, C 27200, C 21000, C 26800, C 52100, C 77000, C 52000, C 11000, C 74500, C 23000, C 28000, C 12200, C 76400, C 51900, C 75400, C 26000, C 51000, C 10200, C 27000
Nickel Alloys	Nickel 200, 201
Inconel	Inconel 600, 601, 625, 718, 800, 825, X-750
Monel	Monel 400, k500
Hastelloy	Hastelloy C-22, C-276, C-4, X
Titanium	Grade 1, 4, 5(Ti 6Al-4V), 6(Ti 5Al-2.5Sn), 7, 11, 6Al-2Sn-4Zr-2Mo, Grade 12, 6Al-6V-25n, Grade 23(Ti 6AL-4V ELI), 8Ai-1Mo-1V, Grade 5 ELI, Grade 9(3Al-2.5V), 6Al-7Nb.
Aluminium	6063, 1100, 6082 A96082, 1050, 2017, 2024 A92024, 7050 A97050, 5083 A95083, 2014A A92014, 2011 A92011, 6061 A96061 A86061, 5754, 7085, 2050, 7071 7020, 7178, 5052 A95052, 7150, 7075 A97075 A87075, 7575, 2219, 7175
Pressure Rating	Class 150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS
Types	Threaded, Plate, Screwed, Forged.
Supporting material	Gasket, Ring Joint, Flange Bolts
Size range	1/2" (15 NB) to 48" (1200NB) DN10~DN5000
High Temperature	Above 200°C (400°F) For Class 150 Or Above 400°C (750°F)
Low Temperature	Above -29 Degree C (−20°F)
Production technique	Forged, machined and Heat treated
Custom design	As per your drawing
Origin	Indian / USA / Korean / West Europe / Japan
Pressure Class	PN 6 TO PN 100
Coating/Surface Treatment:	Zinc Plated, Anti-rust Paint, Oil Black Paint, Yellow Transparent, Cold and Hot Dip Galvanized.
European/African/Russian Standard Flanges	Available
Test	Direct-reading Spectrograph, X-ray detector, UItrasonic flaw detector, Magnetic particle detector, Hydrostatic testing machine.
Marking Standard	Name of Manufacturer
	Schedule
	Type of Flange Facing
	Pressure Class
	Nominal Pipe Size, etc
Test Certificates	EN 10204/3.1B, NACE MR0103, NACE MR0175
	Raw Materials Certificate
	100% Radiography Test Report
	Third Party Inspection Report, etc

ASME B16.5 Flat Face Flange Dimensions

NPS	Pipe Diameter		Flange Inside Daimeter	Number of holes	Flange Daimeter	Thickness of Flange	Daimeter of Bolt Circle	Daimeter of Bolt Holes	Approx.Weight in kg
DN	ISO	DIN	D5	BN	D	b	K	d2	KG/PCS
10	–	14	14.5	4	90	16	60	14	0.7
	17.2	–	17.7	4	90	16	60	14	0.69
15	–	20	21	4	95	16	65	14	0.77
	21.3	–	22	4	95	16	65	14	0.77
20	–	25	26	4	105	18	75	14	1.06
	26.9	–	27.6	4	105	18	75	14	1.05
25	–	30	31	4	115	18	85	14	1.27
	33.7	–	34.4	4	115	18	85	14	1.25
32	–	38	39	4	140	18	100	18	1.86
	42.4	–	43.1	4	140	18	100	18	1.83
40	–	44.5	45.5	4	150	18	110	18	2.12
	48.3	–	49	4	150	18	110	18	2.09
50	–	57	58.1	4	165	20	125	18	2.78
	60.3	–	61.1	4	165	20	125	18	2.74
65	76.1	–	77.1	8	185	22	145	18	3.48
80	88.9	–	90.3	8	200	24	160	18	4.33
100	–	108	109.6	8	235	24	190	22	5.82
	114.3	–	115.9	8	235	24	190	22	5.61
125	–	133	134.8	8	270	26	220	26	7.91
	139.7	–	141.6	8	270	26	220	26	7.6
150	–	159	161.1	8	300	28	250	26	10.12
	168.3	–	170.5	8	300	28	250	26	9.58
175	193.7	–	196.1	12	350	32	295	30	14.45
200	219.1	–	221.8	12	375	34	320	30	16.9
250	–	267	270.2	12	450	38	385	33	27.28
	273	–	276.2	12	450	38	385	33	26.51
300	323.9	–	327.6	16	515	42	450	33	36.38
350	355.6	–	359.7	16	580	46	510	36	52.83
	–	368	372.2	16	580	46	510	36	50.24
400	406.4	–	411	16	660	50	585	39	74.71
	–	419	423.7	16	660	50	585	39	71.44
500	508	–	513.6	20	755	52	670	42	86.87
600	610	–	616.5	20	890	54	795	48	121.84
700	711	–	716	24	995	58	900	48	150.93
800	813	–	818	24	1140	64	1030	56	219.08
900	914	–	920	28	1250	70	1140	56	271.16
1000	1016	–	1022	28	1360	78	1250	56	344.95

Flat Flange DIN 2576 Dimensions

NPS		Dimensions Of Flange				Bolts Size				Weight of one flange 7.85 kilogram/ dm3) kilogram
NW	d1	ds	D	b1	k	Number	Thread		d2
10	14 17.2)	14.5 17.7	90	14	60	4	M12	(1/2")	14	0.613 0.605
15	20 21.3)	20.5 21.8	95	14	65	4	M12	(1/2")	14	0675 0.669
20	25 26.9)	25.5 27.4	105	16	75	4	M12	(1/2")	14	0.947 0.936
25	30 33.7)	30.5 34.2	115	16	85	4	M12	(1/2")	14	1.14 1.11
32	38 42.4)	38.5 42.9	140	16	100	4	M16	(5/8")	18	1.66 1.62
40	44.5 48.3)	45 48.8	150	16	110	4	M16	(5/8")	18	1.89 1.86
50	57 60.3)	57.5 60.8	165	18	125	4	M16	(5/8")	18	2.51 2.47
65	76.1)	76.6	185	18	145	4	M16	(5/8")	18	3.00
80	88.9)	89.4	200	20	160	4	M16	(5/8")	18	3.79
100	108 114.3)	108.5 114.8	220	20	180	8	M16	(5/8")	18	4.20 4.03
125	133 139.7)	133.5 140.2	250	22	210	8	M16	(5/8")	18	5.71 5.46
150	159 168.3)	159.5 168.8	285	22	210	8	M16	(3/4")	23	6.72 6.57
175	191 193.7)	192 194.7	315	24	270	8	M20	(3/4")	23	8.60 8.45
200	216 219.1)	216 220.1	340	24	295	8	M20	(3/4")	23	9.50 9.31
250	267 273)	268 274	395	26	350	12	M20	(3/4")	23	12.5 11.9
400	406.4 419	407.4 420	565	32	515	16	M24	(7/8")	27	27.9 25.9
500	508) 521	509 522	670	38	620	20	M24	(7/8")	27	37.9 41.1

Flat Face Flange Pressure Rating

Asme B16 5 Ff Flange Pressure Pressure
Temperature (°C)	Class
	Class 150	Class 300	Class 400	Class 600	Class 900	Class 1500	Class 2500
-29 - 38	19.8	51.7	68.9	103.4	155	259	431
50	19.5	51.7	68.9	103.4	155	259	431
100	17.7	51.5	68.7	103.0	155	258	429
150	15.8	50.2	66.8	100.3	151	251	418
200	13.8	48.6	64.8	97.2	146	243	405
250	12.1	46.3	61.7	92.7	139	232	386
300	10.2	42.9	57.0	85.7	129	214	357
325	9.3	41.4	55.0	82.6	124	207	344
350	8.4	40.0	53.4	80.0	120	200	334
375	7.4	37.8	50.4	75.7	114	189	315
400	6.5	34.7	46.3	69.4	104	174	290
425	5.5	28.8	38.4	57.5	86.3	144	240
450	4.6	23.0	30.7	46.0	69.0	115	192
475	3.7	17.1	22.8	34.2	51.3	85.4	142
500	2.8	11.6	15.4	23.2	34.7	57.9	96.5
538	1.4	5.9	7.9	11.8	17.7	29.5	49.2

Flat Face Flange Thickness

ANSI B16.5 Flat Face Flange Wall Thickness
NPS (Normal Pipe Sizes)	Outside Daimeter (O.D.)	Schedule 10	Schedule 20	Schedule 30	STD Wall	Schedule 40	Schedule 60	EXT Hvy	Schedule 80	Schedule 100	Schedule 120	Schedule 140	Schedule 160	XX Hvy
½	0.84	0.083	...	...	0.109	0.109	...	0.147	0.147	...	...	...	0.188	0.294
¾	1.05	0.083	...	...	0.113	0.113	...	0.154	0.154	...	...	...	0.219	0.308
1	1.315	0.109	...	...	0.133	0.133	...	0.179	0.179	...	...	...	0.25	0.358
1 ¼	1.66	0.109	...	...	0.14	0.14	...	0.191	0.191	...	...	...	0.25	0.382
1 ½	1.9	0.109	...	...	0.145	0.145	...	0.2	0.2	...	...	...	0.281	0.4
2	2.375	0.109	...	...	0.154	0.154	...	0.218	0.218	...	...	...	0.344	0.436
2 ½	2.875	0.12	...	...	0.203	0.203	...	0.276	0.276	...	...	...	0.375	0.552
3	3.5	0.12	...	...	0.216	0.216	...	0.3	0.3	...	...	...	0.438	0.6
3 ½	4	0.12	...	...	0.226	0.226	...	0.318	0.318	...	...	...	...	0.636
4	4.5	0.12	...	...	0.237	0.237	...	0.337	0.337	...	0.438	...	0.531	0.674
5	5.563	0.134	...	...	0.258	0.258	...	0.375	0.375	...	0.5	...	0.625	0.75
6	6.625	0.134	...	...	0.28	0.28	...	0.432	0.432	...	0.562	...	0.719	0.864
8	8.625	0.148	0.25	0.277	0.322	0.322	0.406	0.5	0.5	0.594	0.719	0.812	0.906	0.875
10	10.75	0.165	0.25	0.307	0.365	0.365	0.5	0.5	0.594	0.719	0.844	1	1.125	1
12	12.75	0.18	0.25	0.33	0.375	0.406	0.562	0.5	0.688	0.844	1	1.125	1.312	1
14	14	0.25	0.312	0.375	0.375	0.438	0.594	0.5	0.75	0.938	1.094	1.25	1.406	...
16	16	0.25	0.312	0.375	0.375	0.5	0.656	0.5	0.844	1.031	1.219	1.438	1.594	...
18	18	0.25	0.312	0.438	0.375	0.562	0.75	0.5	0.938	1.156	1.375	1.562	1.781	...
20	20	0.25	0.375	0.5	0.375	0.594	0.812	0.5	1.031	1.281	1.5	1.75	1.969	...
22	22	0.25	...	...	0.375	...	...	0.5	...	...	....	....	....	....
24	24	0.25	0.375	0.562	0.375	0.688	0.969	0.5	1.219	1.531	1.812	2.062	2.344	....
26	26	....	....	....	0.375	....	....	0.5	....	....	....	....	....	....
30	30	0.312	0.5	0.625	0.375	....	....	0.5	....	....	....	....	....	....
36	36	0.312	0.5	0.625	0.375	0.75	....	0.5	....	....	....	....	....	....
40	40	....	....	....	0.375	....	....	0.5	....	....	....	....	....	....
42	42	……..	……..	……..	0.375	……..	……..	0.5	……..	……..	……..	……..	……..	……..
48	48	……..	……..	……..	0.375	……..	……..	0.5	……..	……..	……..	……..	……..	……..

Flat Face Flange Bolt Length

	Class 150 Flanges				Class 300 Flanges				Class 600 Flanges
NPS	# Bolts And Studs	Diameter of Bolts And Studs	Stud Length		# Bolts And Studs	Diameter of Bolts And Studs	Stud Length		# Bolts And Studs	Diameter of Bolts And Studs	Stud Length
			1/16 RF	RTJ			1/16 RF	RTJ			1/4 RF	RTJ
1/2	4	0.50	2-1/4	–	4	0.50	2-1/2	3	4	0.50	3	3
3/4	4	0.50	2-1/2	–	4	0.63	3	3-1/2	4	0.63	3-1/2	3-1/2
1	4	0.50	2-1/2	3	4	0.63	3	3-1/2	4	0.63	3-1/2	3-1/2
1-1/4	4	0.50	2-3/4	3-1/4	4	0.63	3-1/4	3-3/4	4	0.63	3-3/4	3-3/4
1-1/2	4	0.50	2-3/4	3-1/4	4	0.75	3-1/2	4	4	0.75	4-1/4	4-1/4
2	4	0.63	3-1/4	3-3/4	8	0.63	3-1/2	4	8	0.63	4-1/4	4-1/4
2-1/2	4	0.63	3-1/2	4	8	0.75	4	4-1/2	8	0.75	4-3/4	4-3/4
3	4	0.63	3-1/2	4	8	0.75	4-1/4	4-3/4	8	0.75	5	5
3-1/2	8	0.63	3-1/2	4	8	0.75	4-1/4	5	8	0.88	5-1/2	5-1/2
4	8	0.63	3-1/2	4	8	0.75	4-1/2	5	8	0.88	5-3/4	5-3/4
5	8	0.75	3-3/4	4-1/4	8	0.75	4-3/4	5-1/4	8	1.00	6-1/2	6-1/2
6	8	0.75	4	4-1/2	12	0.75	4-3/4	5-1/2	12	1.00	6-3/4	6-3/4
8	8	0.75	4-1/4	4-3/4	12	0.88	5-1/2	6	12	1.13	7-1/2	7-3/4
10	12	0.88	4-1/2	5	16	1.00	6-1/4	6-3/4	16	1.25	8-1/2	8-1/2
12	12	0.88	4-3/4	5-1/4	16	1.13	6-3/4	7-1/4	20	1.25	8-3/4	8-3/4
14	12	1.00	5-1/4	5-3/4	20	1.13	7	7-1/2	20	1.38	9-1/4	9-1/4
16	16	1.00	5-1/4	5-3/4	20	1.25	7-1/2	8	20	1.50	10	10
18	16	1.13	5-3/4	6-1/4	24	1.25	7-3/4	8-1/4	20	1.63	10-3/4	10-3/4
20	20	1.13	6-1/4	6-3/4	24	1.25	8	8-3/4	24	1.63	11-1/4	11-1/2
24	20	1.25	6-3/4	7-1/4	24	1.50	9	10	24	1.88	13	13-1/4

Flat Face Flange Gasket Dimensions

NPS In Inches	Gasket Inside Daimeter In Inches	Gasket Outside Daimeter In Inches	Bolt Holes Number	Bolt Holes Diameter In Inches	Circle Of Bolt In Inches
1/2	13/16	3 1/2	4	5/8	2 3/8
3/4	1 1/16	3 7/8	4	5/8	2 3/4
1	1 5/16	4 1/4	4	5/8	3 1/8
1 1/4	1 5/8	4 5/8	4	5/8	3 1/2
1 1/2	1 7/8	5	4	5/8	3 7/8
2	2 3/8	6	4	3/4	4 3/4
2 1/2	2 7/8	7	4	3/4	5 1/2
3	3 1/2	7 1/2	4	3/4	6
3 1/2	4	8 1/2	8	3/4	7
4	4 1/2	9	8	3/4	7 1/2
5	5 9/16	10	8	7/8	8 1/2
6	6 5/8	11	8	7/8	9 1/2
8	8 5/8	13 1/2	8	7/8	11 3/4
10	10 3/4	16	12	1	14 1/4
12	12 3/4	19	12	1	17
14	14	21	12	1 1/8	18 3/4
16	16	23 1/2	16	1 1/8	21 1/4
18	18	25	16	1 1/4	22 3/4
20	20	27 1/2	20	1 1/4	25
22	22	29 1/2	20	1 3/8	27 1/4
24	24	32	20	1 3/8	29 1/2
26	26	34 1/4	24	1 3/8	31 3/4
28	28	36 1/2	28	1 3/8	34
30	30	38 3/4	28	1 3/8	36
32	32	41 3/4	28	1 5/8	38 1/2
34	34	43 3/4	32	1 5/8	40 1/2
36	36	46	32	1 5/8	42 3/4
38	38	48 3/4	32	1 5/8	45 1/4
40	40	50 3/4	36	1 5/8	47 1/4
42	42	53	36	1 5/8	49 1/2
44	44	55 1/4	40	1 5/8	51 3/4
46	46	57 1/4	40	1 5/8	53 3/4
48	48	59 1/2	44	1 5/8	56
50	50	61 3/4	44	1 7/8	58 1/4
52	52	64	44	1 7/8	60 1/2
54	54	66 1/4	44	1 7/8	62 3/4
60	60	73	52	1 7/8	69 1/4
66	66	80	52	1 7/8	76
72	72	86 1/2	60	1 7/8	82 1/2
84	84	99 3/4	64	2 1/8	95 1/2
96	96	113 1/4	68	2 3/8	108 1/2