Square Flanges | SAE J518 | Custom Drilled

PM Industries manufactures, supplies, and stocks Square Flanges in a range of materials, thicknesses, and custom dimensions. A square flange is a flat plate component with a square outer profile, machined or cut with a center bore and fixing holes arranged to match the specific mounting or connection requirement. Unlike round flanges with standardized bolt circles and dimensions governed by ASME B16.5 or B16.47, square flanges are typically produced to custom dimensions defined by the equipment, structure, or system they connect to.

The square profile provides specific practical advantages in certain applications. Flat sides align naturally against square tube, rectangular structural sections, and equipment frames. Corners can be clamped or referenced during assembly without the rotation ambiguity that round flanges present when precise angular positioning matters. For custom fabricated equipment, machine bases, and structural assemblies where the connection geometry is defined by the design rather than a piping standard, square flanges fit the requirement directly.

Custom fabrication compatibility is where square flanges add the most value. In a standard round piping system, ASME flanges provide ready-made standardized connections. In custom-engineered equipment, machine frames, ductwork, structural assemblies, and process skids where connection geometry is defined by the design, a square flange produced to the equipment drawing provides a clean, accurate connection point that a standard round flange can't replicate without modification.

Ductwork and HVAC applications are a consistent use area. Rectangular and square ductwork sections use square or rectangular flanges at connections, transitions, and equipment interfaces. The square profile matches the duct geometry, and fixing holes spaced around the perimeter of the square flange face provide the bolted connection between duct sections. Sheet metal duct flanges cover the lightweight end of this application, while thicker machined or cut square flanges cover connections to fans, air handling units, and industrial ventilation equipment where more substantial hardware is required.

Structural and machine building applications use square flanges as mounting pads, end plates, and connection points on square and rectangular hollow section steelwork. Welding a square flange to the end of a square tube provides a flat, drilled face for bolting the tube to a baseplate, another structural section, or equipment. That's a common detail in machine frames, support structures, and equipment skids where structural connections must be strong, flat, and accurately positioned.

Square flanges are manufactured to customer drawings and dimensional specifications in a range of materials with standard or certified mill test reports. Contact PM Industries for material selection, dimensions, bore size, fixing hole pattern, and pricing.

Specification Square 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

Grade Designations of Square Exhaust Flange

ASTM	BS	DIN	EURONORM
304	304S15	X5 Cr Ni 18 10	1.4301
304L	304S11	X2 Cr Ni 18 9	1.4307
316	316S31	X5 Cr Ni Mo 17 12 2	1.4401
316L	316S11	X2 Cr Ni Mo 17 13 2	1.4404
321	321S31	X6 Cr Ni 18 10	1.4541
316Ti	320S31	X6 Cr Ni Mo Ti 17 12 2	1.4571
SMO	254SMO	X1 Cr Ni Mo Cu N 20 18 7	1.4547

Stainless Steel Square Flange Weight Chart

NPS Inches	DN mm	Flange Outer Diameter A MM	Flange Thickness D MM	Slip On Flange Weight in KGS	Weld Neck Flange Weight in KGS	Blind Flange Weight in KGS
1/ 2	15	88.9	11.2	0.4	0.5	0.4
24	600	812.8	47.8	86.9	115	185.0
1	25	108	14.2	0.8	1	0.9
1 1/ 4	32	117.3	15.7	1	1.3	1.2
1 1/ 2	40	127	17.5	1.3	1.7	1.5
2	50	152.4	19.1	2.1	2.6	2.4
3/ 4	20	98.6	12.7	0.6	0.7	0.6
2 1/ 2	65	177.8	22.4	3.3	4.1	3.9
3	80	190.5	23.9	3.9	4.9	4.9
3 1/ 2	90	215.9	23.9	4.8	6.1	6.2
18	450	635	39.6	48.9	68.3	93.7
5	125	254	23.9	6.1	8.6	8.6
6	150	279.4	25.4	7.5	10.6	11.3
8	200	342.9	28.4	12.1	17.6	19.6
10	250	406.4	30.2	16.5	24	28.6
12	300	482.6	31.8	26.2	36.5	43.2
4	100	228.6	23.9	5.3	6.8	7.0
14	350	533.4	35.1	34.6	48.4	58.1
16	400	596.9	36.6	44.8	60.6	76.1
20	500	698.5	42.9	61.9	84.5	122.0

Square Flange Size Chart

Square Flange Size (mm)	No. of Holes	Hole Diameter (mm)
150	8	Ø 10
200	12	Ø 12
250	12	Ø 12
300	12	Ø 14
400	12	Ø 14
500	16	Ø 14
600	16	Ø 18
700	20	Ø 18
800	20	Ø 18