ASME B16.1 Pipe Flanges | McMaster-Carr

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About Pipe and Fittings

Measure your pipe and fittings to identify their pipe size, thread size, schedule, and thread type. Then, find compatible components.

FM-Approved Low-Pressure Cast Iron Threaded Pipe Flanges

Suitable for use in fire-protection applications, these flanges are brittle and can be quickly opened with the strike of a sledge hammer. Bolt two flanges of the same size together with a gasket (sold separately) to create an access point within a line. Use in noncorrosive environments.

Reducing flanges transition your system to a smaller pipe size. Attach them to a flange with a larger pipe size but with the same flange dimensions.

Flanges

Front

Flat Surface on Back

For Use With: Air, Natural Gas, Oil, Steam, Water
Specifications Met:
3/4 Pipe Size: ASME B1.20.1, ASME B16.1, ASTM A126, FM Approved
All other sizes: ASME B1.20.1, ASME B16.1, ASTM A126, FM Approved, UL Listed
Pipe Nipples and Pipe: Use Schedule 40 steel
Fittings: Use Class 125 iron and steel

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each
NPT
3/4	3 7/8"	1/2"	5/8"	4	2 3/4"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K111	000000
1	4 1/4"	1/2"	5/8"	4	3 1/8"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K112	00000
1 1/4	4 5/8"	1/2"	5/8"	4	3 1/2"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K113	00000
1 1/2	5"	1/2"	5/8"	4	3 7/8"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K114	00000
2	6"	5/8"	3/4"	4	4 3/4"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K115	00000
2 1/2	7"	5/8"	3/4"	4	5 1/2"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K116	00000
3	7 1/2"	5/8"	3/4"	4	6"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K117	00000
4	9"	5/8"	3/4"	8	7 1/2"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K118	000000
5	10"	3/4"	7/8"	8	8 1/2"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K131	000000
6	11"	3/4"	7/8"	8	9 1/2"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K132	000000
8	13 1/2"	3/4"	7/8"	8	11 3/4"	125 psi @ 72° F	125 psi @ 350° F	Iron	68185K133	000000

Reducing Flanges

Front

Flat Surface on Back

For Use With: Air, Natural Gas, Oil, Steam, Water
Specifications Met: ASME B1.20.1, ASME B16.1, ASTM A126, ASTM A153, FM Approved
Pipe Nipples and Pipe: Use Schedule 40 iron and steel
Fittings: Use Class 125 iron and steel

				Bolt Hole
Pipe Size	For Flange Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each
NPT
2	2 1/2	7"	5/8"	3/4"	4	5 1/2"	175 psi @ 72° F	125 psi @ 350° F	Iron	68185K101	0000000
2	3	7 1/2"	5/8"	3/4"	4	6"	175 psi @ 72° F	125 psi @ 350° F	Iron	68185K102	000000
2	4	9"	5/8"	3/4"	8	7 1/2"	175 psi @ 72° F	125 psi @ 350° F	Iron	68185K103	000000
3	4	9"	5/8"	3/4"	8	7 1/2"	175 psi @ 72° F	125 psi @ 350° F	Iron	68185K104	000000
4	6	11"	3/4"	7/8"	8	9 1/2"	175 psi @ 72° F	125 psi @ 350° F	Iron	68185K105	000000

FM-Approved Low-Pressure Cast Iron Unthreaded Pipe Flanges

Front

Flat Surface on Back

For Use With: Air, Diesel Fuel, Gasoline, Natural Gas, Oil, Steam, Water
Pressure Class: 125
Specifications Met: ASME B1.20.1, ASME B16.1, ASTM A126, FM Approved
Pipe Nipples and Pipe: Use Schedule 40 steel
Fittings: Use Class 125 or 150 iron and steel

FM-approved for fire protection applications, these flanges are cast iron, so they're brittle and can be quickly opened by hitting them with a sledge hammer. Bolt them together with a gasket (not included) to create an access point within a low-pressure pipe line. All are cap flanges, which are also known as blind flanges. Use them in noncorrosive environments.

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure		Each
1	4 1/4"	1/2"	5/8"	4	3 1/8"	200 psi @ 72° F	165 psi @ 300° F	4824N11	000000
1 1/2	5"	1/2"	5/8"	4	3 7/8"	200 psi @ 72° F	165 psi @ 300° F	4824N12	00000
2	6"	5/8"	3/4"	4	4 3/4"	200 psi @ 72° F	165 psi @ 300° F	4824N13	00000
2 1/2	7"	5/8"	3/4"	4	5 1/2"	200 psi @ 72° F	165 psi @ 300° F	4824N14	00000
3	7 1/2"	5/8"	3/4"	4	6"	200 psi @ 72° F	165 psi @ 300° F	4824N15	00000
3 1/2	8 1/2"	5/8"	3/4"	8	7"	200 psi @ 72° F	165 psi @ 300° F	4824N16	000000
4	9"	5/8"	3/4"	8	7 1/2"	200 psi @ 72° F	165 psi @ 300° F	4824N17	000000
6	11"	3/4"	7/8"	8	9 1/2"	200 psi @ 72° F	165 psi @ 300° F	4824N18	000000

FM-Approved Iron Pipe Fittings with Flanged Ends

FM approved, these fittings are suitable for use in fire-protection systems. All have flat-surface flanged ends that only mate to another same-size flat-surface flange, pump, or valve with a gasket (sold separately) to create an access point in a pipeline. Use them in noncorrosive areas.

Straight Reducers

For Use With: Air, Natural Gas, Oil, Steam, Water
Specifications Met: FM Approved, UL Listed, ASTM A126, ASTM B307, Fed. Spec. WW-F-406, ASME B16.1, ASME B1.20.1
Pipe Nipples and Pipe: Use Schedule 40 steel
Flanges: Use Class 150 steel

Pipe Size		Flange OD			Bolt Hole		Bolt Circle Dia.
(A)	(B)	(A)	(B)	For Bolt Dia.	Dia.	No. of	(A)	(B)	Max. Pressure	Max. Steam Pressure	Material		Each
2 1/2	2	7"	6"	5/8"	3/4"	4	5 1/2"	4 3/4"	150 psi @ 72° F	125 psi @ 350° F	Iron	1117T19	0000000
3	2	7 1/2"	6"	5/8"	3/4"	4	6"	4 3/4"	150 psi @ 72° F	125 psi @ 350° F	Iron	1117T22	000000
3	2 1/2	7 1/2"	7"	5/8"	3/4"	4	6"	5 1/2"	150 psi @ 72° F	125 psi @ 350° F	Iron	1117T21	000000
4	3	9"	7 1/2"	5/8"	3/4"	8	7 1/2"	6"	150 psi @ 72° F	125 psi @ 350° F	Iron	1117T23	000000

Aluminum Unthreaded Pipe Flanges

Also known as Pressure Class 125 flanges, these are for use in low-pressure applications. Bolt two same-size flanges together with a gasket (sold separately) to create an access point within a line. Flanges are aluminum, which is lightweight with good corrosion resistance.

Butt-weld flanges are also known as weld-neck flanges; the flange neck has a beveled end that, when flush to pipe, creates a trough for a strong weld. Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides. Reducing flanges let you transition your system to a smaller pipe size; attach to a flange with a larger pipe size but with the same flange dimensions. Cap flanges are also known as blind flanges.

Butt-Weld Flanges

Front

Flat Surface on Back

For Use With: Air, Oil, Water
Pressure Class: 125
Specifications Met: ASME B16.1
Fittings: Use Schedule 40 aluminum
Pipe: Use Schedule 40 aluminum

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure		Each
1/2	3 1/2"	1/2"	5/8"	4	2 3/8"	150 psi @ 72° F	44705K543	000000
3/4	3 7/8"	1/2"	5/8"	4	2 3/4"	150 psi @ 72° F	44705K544	00000
1	4 1/4"	1/2"	5/8"	4	3 1/8"	150 psi @ 72° F	44705K545	00000
1 1/2	5"	1/2"	5/8"	4	3 7/8"	150 psi @ 72° F	44705K547	000000
2	6"	5/8"	3/4"	4	4 3/4"	150 psi @ 72° F	44705K548	000000
2 1/2	7"	5/8"	3/4"	4	5 1/2"	150 psi @ 72° F	44705K549	000000
3	7 1/2"	5/8"	3/4"	4	6"	150 psi @ 72° F	44705K551	000000
4	9"	5/8"	3/4"	8	7 1/2"	150 psi @ 72° F	44705K552	000000
6	11"	3/4"	7/8"	8	9 1/2"	150 psi @ 72° F	44705K553	000000

Slip-On Weld Flanges

Front

Flat Surface on Back

For Use With: Air, Oil, Water
Pressure Class: 125
Specifications Met: ASME B16.1
Fittings: Use Schedule 40 aluminum
Pipe: Use Schedule 40 aluminum

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure		Each
1/2	3 1/2"	1/2"	5/8"	4	2 3/8"	150 psi @ 72° F	44705K37	000000
3/4	3 7/8"	1/2"	5/8"	4	2 3/4"	150 psi @ 72° F	44705K38	00000
1	4 1/4"	1/2"	5/8"	4	3 1/8"	150 psi @ 72° F	44705K361	00000
1 1/4	4 5/8"	1/2"	5/8"	4	3 1/2"	150 psi @ 72° F	44705K362	00000
1 1/2	5"	1/2"	5/8"	4	3 7/8"	150 psi @ 72° F	44705K363	00000
2	6"	5/8"	3/4"	4	4 3/4"	150 psi @ 72° F	44705K364	00000
2 1/2	7"	5/8"	3/4"	4	5 1/2"	150 psi @ 72° F	44705K365	00000
3	7 1/2"	5/8"	3/4"	4	6"	150 psi @ 72° F	44705K366	00000
4	9"	5/8"	3/4"	8	7 1/2"	150 psi @ 72° F	44705K367	000000
6	11"	3/4"	7/8"	8	9 1/2"	150 psi @ 72° F	44705K542	000000
8	13 1/2"	3/4"	7/8"	8	11 3/4"	150 psi @ 72° F	44705K772	000000

Slip-On Weld Reducing Flanges

Front

Flat Surface on Back

For Use With: Air, Oil, Water
Pressure Class: 125
Specifications Met: ASME B16.1
Fittings: Use Schedule 40 aluminum
Pipe: Use Schedule 40 aluminum

				Bolt Hole
Pipe Size	For Flange Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure		Each
3	4	9"	5/8"	3/4"	8	7 1/2"	150 psi @ 72° F	44705K768	0000000
6	8	13 1/2"	3/4"	7/8"	8	11 3/4"	150 psi @ 72° F	44705K771	000000

Caps

Front

Flat Surface on Back

For Use With: Air, Oil, Water
Pressure Class: 125
Specifications Met: ASME B16.1
Fittings: Use Schedule 40 aluminum
Pipe: Use Schedule 40 aluminum

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure		Each
1/2	3 1/2"	1/2"	5/8"	4	2 3/8"	150 psi @ 72° F	44705K531	000000
3/4	3 7/8"	1/2"	5/8"	4	2 3/4"	150 psi @ 72° F	44705K532	00000
1	4 1/4"	1/2"	5/8"	4	3 1/8"	150 psi @ 72° F	44705K533	00000
1 1/4	4 5/8"	1/2"	5/8"	4	3 1/2"	150 psi @ 72° F	44705K534	00000
1 1/2	5"	1/2"	5/8"	4	3 7/8"	150 psi @ 72° F	44705K535	00000
2	6"	5/8"	3/4"	4	4 3/4"	150 psi @ 72° F	44705K536	00000
2 1/2	7"	5/8"	3/4"	4	5 1/2"	150 psi @ 72° F	44705K537	00000
3	7 1/2"	5/8"	3/4"	4	6"	150 psi @ 72° F	44705K538	000000
4	9"	5/8"	3/4"	8	7 1/2"	150 psi @ 72° F	44705K539	000000
6	11"	3/4"	7/8"	8	9 1/2"	150 psi @ 72° F	44705K541	000000
8	13 1/2"	3/4"	7/8"	8	11 3/4"	150 psi @ 72° F	44705K399	000000

Low-Pressure Aluminum Threaded Pipe Flanges

Reducing flanges allow you to transition your system to a smaller pipe size; attach to a flange with a larger pipe size but with the same flange dimensions.

Flanges

Front

Flat Surface on Back

For Use With: Air, Oil, Water
Pressure Class: 125
Specifications Met:
Pipe Size 1-6: ASME B16.1
Fittings: Use Class 150 aluminum
Pipe Nipples and Pipe: Use Schedule 40 aluminum

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure		Each
NPT
1	4 1/4"	1/2"	5/8"	4	3 1/8"	150 psi @ 72° F	44705K231	000000
1 1/4	4 5/8"	1/2"	5/8"	4	3 1/2"	150 psi @ 72° F	44705K232	00000
1 1/2	5"	1/2"	5/8"	4	3 7/8"	150 psi @ 72° F	44705K233	00000
2	6"	5/8"	3/4"	4	4 3/4"	150 psi @ 72° F	44705K234	00000
2 1/2	7"	5/8"	3/4"	4	5 1/2"	150 psi @ 72° F	44705K235	00000
3	7 1/2"	5/8"	3/4"	4	6"	150 psi @ 72° F	44705K236	00000
4	9"	5/8"	3/4"	8	7 1/2"	150 psi @ 72° F	44705K238	000000
6	11"	3/4"	7/8"	8	9 1/2"	150 psi @ 72° F	44705K437	000000
8	13 1/2"	3/4"	7/8"	8	11 3/4"	150 psi @ 72° F	44705K745	000000

Reducing Flanges

Front

Flat Surface on Back

For Use With: Air, Oil, Water
Pressure Class: 125
Specifications Met: ASME B16.1
Fittings: Use Class 150 aluminum
Pipe Nipples and Pipe: Use Schedule 40 aluminum

				Bolt Hole
Pipe Size	For Flange Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure		Each
NPT
1/2	3/4	3 7/8"	1/2"	5/8"	4	2 3/4"	150 psi @ 72° F	44705K712	000000
3/4	1	4 1/4"	1/2"	5/8"	4	3 1/8"	150 psi @ 72° F	44705K715	00000
1	1 1/4	4 5/8"	1/2"	5/8"	4	3 1/2"	150 psi @ 72° F	44705K718	00000
1 1/4	1 1/2	5"	1/2"	5/8"	4	3 7/8"	150 psi @ 72° F	44705K721	00000
1 1/2	2	6"	5/8"	3/4"	4	4 3/4"	150 psi @ 72° F	44705K724	00000
2	2 1/2	7"	5/8"	3/4"	4	5 1/2"	150 psi @ 72° F	44705K727	00000
2	3	7 1/2"	5/8"	3/4"	4	6"	150 psi @ 72° F	44705K733	000000
3	4	9"	5/8"	3/4"	8	7 1/2"	150 psi @ 72° F	44705K736	000000
4	6	11"	3/4"	7/8"	8	9 1/2"	150 psi @ 72° F	44705K739	000000
6	8	13 1/2"	3/4"	7/8"	8	11 3/4"	150 psi @ 72° F	44705K742	000000