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Learn about Flanges for Piping

In piping applications, a flange is used to join a pipe with other equipment (another pipe, a valve or a pump). Pipe flanges may be classified by shape (weld neck, blind, socket weld, threaded, etc), by facing type (RF, FF, RTJ), by material grade (cast and forged), and by specification (the ANSI/ASME B16.5 and B16.47 specifications cover US standard flanges for piping, the EN 1092-1 specification covers European pipe flanges).

WHAT IS A FLANGE?

A flange is a cast or forged steel product used to connect a pipe with another mechanical device. In the oil and gas industry, forged steel flanges are preferred due to their intrinsic strength and durability.

FLANGE SIZES

The key sizes for a pipe flange are:

  • the nominal size (i.e. the bore size of the flange, to match the bore size of the connecting pipe)
  • the flange rating (which designates the pressure/temperature performance of the flange, i.e. 150#, 300#, 400#, up to 2500#)
  • the schedule for welding neck flanges (that should match the pipe schedule)

FLANGES IN PIPING

Pipe flanges are available in multiple types, the standard ones are the welding neck, blind, socket weld, lap joint, threaded, etc.). There are also some special types of flanges, like the swivel flanges, the expander/reducer flanges, the Nipoflange/Weldoflange, and the orifice flanges.

As a general rule, welding neck, slip-on, and socket weld flanges are used for high-pressure applications that require long-lasting flanged joints. Threaded flanges can be used with a lower pressure piping system, and if vibrations are not present.

Lap joint flanges are used in connection with stub ends either to facilitate the alignment of the bolts of the two mating flanges, or to reduce the cost of noble materials in high-grade flanged joints (example, in an Inconel piping system, the stub end connected to the pipe may be in Inconel, whereas the lap joint flange can be of a lower grade, thus saving the overall weight of the expensive Inconel material).

MATERIAL GRADES

The key material grades for pipe flanges, examined in a separate article, are:

  • ASTM A105 (carbon steel flanges for high-temperature service)
  • ASTM A350 (CS flange for low temperature)
  • ASTM A694 (high yield carbon steel flange for line pipes)
  • ASTM A182 F1 to F91 (alloy steel flange)
  • ASTM A182 F304, F316, F321 (stainless steel flange)
  • ASTM A182 F51, ASTM A182 F53/55 (duplex and super duplex flange), and higher grades (Inconel, Hastelloy, Monel flange).

Non-ferrous pipe flanges (copper, cupronickel, and aluminum) are used in marine and aeronautical applications.

The pipe and the flange material shall, of course, match (according to the ASTM piping materials selection chart).

For specific applications, flanges may be coated, painted or internally lined (with Teflon, for example) to enhance the resistance of the metal to the aggression of corrosive or erosive fluids.

ASME/EN SPECIFICATIONS

The ASME B16.5 specification covers flanges for piping applications up to 24 inches in diameter, whereas the ASME B16.47 specification covers pipe flanges above 24 inches (series A and B are available).

Pipe flanges for European piping systems are covered by the EN 1092-1 specification  (weld neck flange type 11, plate flange type 01, blind flange type 05, threaded flange type 13).

WHAT IS A FLANGED JOINT?

A flanged joint is a connection between a pipe and another piping equipment (example, another length of pipe, a valve, or a pressure vessel). Hundreds, even thousands, of flanged joints are necessary for a piping system to function.

The three main components of a flanged joint are:

  • two mating flanges (the “main” and the “companion” flange).
  • a number of stud bolts for flanges (flanges of different diameter, class, and face finish require different numbers and sizes of stud bolts and nuts for proper sealing);
  • two gaskets, which can be either metallic (spiral wound, ring joint, jacketed and Kammprofile), or non-metallic (non-asbestos gaskets).

A steel pipe can be welded on the flange (this is the case of weld neck, socket weld, slip-on, and lap joint flange) or screwed onto it (threaded flange). Welded connections between pipes and flanges are used for high pressures and temperatures applications, and diameters above 2 inches. Threaded connections are used for small diameter piping systems that are not subject to mechanical forces as expansion, vibration, contraction, oscillation.

A Flange insulation kits can also be used for a flanged connection, to protect the corrosion on flanges, bolts, and gaskets generated by the static currents running through the pipeline (this is called “cathodic protection”).

To prevent dangerous leakages in the pipeline, flanged joints shall be executed by trained personnel only (the standard TSE – TS EN 1591 Part 1-4, “Flanges and their joints” is the reference norm).

flanged joint connection

 

FLANGE BOLT CHART

Flanges for piping should be mated using proper stud bolts and nuts. It is absolutely critical to use the right number, diameter, length, and material to bolt flanges properly and ensure leak-free connections. Further, stud bolts shall be tightened with a proper sequence and by applying a proper torque.

The flange bolt chart shows the exact number, the diameter and the length of the stud bolts required by ASME flanges with different size, class and face finish.

Nominal Pipe Size (NPS) Class 150 Class 300 Class 400 Class 600
# of Bolts Bolt Diameter Bolt Length # of Bolts Bolt Diameter Bolt Length # of Bolts Bolt Diameter Bolt Length # of Bolts Bolt Diameter Bolt Length
1/2 4 1/2 2 1/4 4 1/2 2 1/2 4 1/2 3 4 1/2 3
3/4 4 1/2 2 1/2 4 5/8 3 4 5/8 3 1/2 4 5/8 3 1/2
1 4 1/2 2 1/2 4 5/8 3 4 5/8 3 1/2 4 5/8 3 1/2
1 1/4 4 1/2 2 3/4 4 5/8 3 1/4 4 5/8 3 3/4 4 5/8 3 3/4
1 1/2 4 1/2 2 3/4 4 3/4 3 1/2 4 3/4 4 1/4 4 3/4 4 1/4
2 4 5/8 3 1/4 8 5/8 3 1/2 8 5/8 4 1/4 8 5/8 4 1/4
2 1/2 4 5/8 3 1/2 8 3/4 4 8 3/4 4 3/4 8 3/4 4 3/4
3 4 5/8 3 1/2 8 3/4 4 1/4 8 3/4 5 8 3/4 5
3 1/2 8 5/8 3 1/2 8 3/4 4 1/4 8 7/8 5 1/2 8 7/8 5 1/2
4 8 5/8 3 1/2 8 3/4 4 1/2 8 7/8 5 1/2 8 7/8 5 3/4
5 8 3/4 3 3/4 8 3/4 4 3/4 8 7/8 5 3/4 8 1 6 1/2
6 8 3/4 4 12 3/4 4 3/4 12 7/8 6 12 1 6 3/4
8 8 3/4 4 1/4 12 7/8 5 1/2 12 1 6 3/4 12 1 1/8 7 1/2
10 12 7/8 4 1/2 16 1 6 1/4 16 1 1/8 7 1/2 16 1 1/4 8 1/2
12 12 7/8 4 3/4 16 1 1/8 6 3/4 16 1 1/4 8 20 1 1/4 8 3/4
14 12 1 5 1/4 20 1 1/8 7 20 1 1/4 8 1/4 20 1 3/8 9 1/4
16 16 1 5 1/4 20 1 1/4 7 1/2 20 1 3/8 8 3/4 20 1 1/2 10
18 16 1 1/8 5 3/4 24 1 1/4 7 3/4 24 1 3/8 9 20 1 5/8 10 3/4
20 20 1 1/8 6 1/4 24 1 1/4 8 24 1 1/2 9 1/2 24 1 5/8 11 1/4
22 20 1 1/4 6 1/2 24 1 1/2 8 3/4 24 1 5/8 10 24 1 5/8 12
24 20 1 1/4 6 3/4 24 1 1/2 9 24 1 3/4 10 1/2 24 1 7/8 13

 

Nominal Pipe Size (NPS) Class 900 Class 1500 Class 2500
# of Bolts Bolt Diameter Bolt Length # of Bolts Bolt Diameter Bolt Length # of Bolts Bolt Diameter Bolt Length
1/2 4 3/4 4 1/4 4 3/4 4 1/4 4 3/4 4 3/4
3/4 4 3/4 4 1/2 4 3/4 4 1/2 4 3/4 5
1 4 7/8 5 4 7/8 5 4 7/8 5 1/2
1 1/4 4 7/8 5 4 7/8 5 4 1 6
1 1/2 4 1 5 1/2 4 1 5 1/2 4 1 1/8 6 3/4
2 8 7/8 5 3/4 8 7/8 5 3/4 8 1 7
2 1/2 8 1 6 1/4 8 1 6 1/4 8 1 1/8 7 3/4
3 8 7/8 5 3/4 8 1 1/8 7 8 1 1/4 8 3/4
3 1/2
4 8 1 1/8 6 3/4 8 1 1/4 7 3/4 8 1 1/2 10
5 8 1 1/4 7 1/2 8 1 1/2 9 3/4 8 1 3/4 11 3/4
6 12 1 1/8 7 1/2 12 1 3/8 10 1/4 8 2 13 1/2
8 12 1 3/8 8 3/4 12 1 5/8 11 1/2 12 2 15
10 16 1 3/8 9 1/4 12 1 7/8 13 1/4 12 2 1/2 19 1/4
12 20 1 3/8 10 16 2 14 3/4 12 2 3/4 21 1/4
14 20 1 1/2 10 3/4 16 2 1/4 16
16 20 1 5/8 11 1/4 16 2 1/2 17 1/2
18 20 1 7/8 12 3/4 16 2 3/4 19 1/4
20 20 2 13 3/4 16 3 21 1/4
22
24 20 2 1/2 17 1/4 16 3 1/2 24 1/4

PIPE FLANGE WEIGHT

CLASS 150 FLANGES WEIGHT

NPS

(Inches)

DN
(mm)
FLANGE OD
(mm)
THICKNESS
(mm)
SLIP ON
(KGS)
WELD NECK (KGS) BLIND FLANGE (KGS)
1/ 2 15 88.9 11.2 0.4 0.5 0.4
3/ 4 20 98.6 12.7 0.6 0.7 0.6
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
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
4 100 228.6 23.9 5.3 6.8 7.0
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
14 350 533.4 35.1 34.6 48.4 58.1
16 400 596.9 36.6 44.8 60.6 76.1
18 450 635 39.6 48.9 68.3 93.7
20 500 698.5 42.9 61.9 84.5 122.0
24 600 812.8 47.8 86.9 115 185.0

CLASS 300 FLANGES WEIGHT

NPS

(Inches)

DN
(mm)
FLANGE OD
(mm)
THICKNESS
(mm)
SLIP ON
(KGS)
WELD NECK (KGS) BLIND
(KGS)
1/ 2 15 95.3 14.2 0.6 0.8 0.6
3/ 4 20 117.3 15.7 1.1 1.3 1.1
1 25 124 17.5 1.4 1.5 1.4
1 1/ 4 32 133.4 19.1 1.7 2.0 1.8
1 1/ 2 40 155.5 20.6 2.5 2.9 2.7
2 50 165.1 22.4 2.9 3.4 3.2
2 1/ 2 65 190.5 25.4 4.3 5.2 4.9
3 80 215.9 28.4 5.9 6.9 6.8
3 1/ 2 90 228.6 30.2 7.3 8.7 8.7
4 100 254 31.8 9.6 11.2 11.5
5 125 279.4 35.1 12.3 15.1 15.6
6 150 317.5 36.6 15.6 19.1 20.9
8 200 381 41.1 24.2 29.9 34.3
10 250 444.5 47.6 34.1 42.7 53.3
12 300 520.7 50.8 49.8 61.8 78.8
14 350 584.2 53.8 69.9 85.8 105.0
16 400 647.7 57.2 88.1 106.0 137.0
18 450 711.2 60.5 109.0 131.0 175.0
20 500 774.7 63.5 134.0 158.0 221.0
24 600 914.4 70.0 201.0 230.0 339.0

CLASS 600 FLANGE WEIGHT

NPS

(Inches)

DN
(mm)
FLANGE OD
(mm)
THICKNESS
(mm)
SLIP ON
(KGS)
WELD NECK (KGS) BLIND
(KGS)
1/ 2 15 95.3 14.2 0.7 0.9 0.8
3/ 4 20 117.3 15.7 1.3 1.5 1.3
1 25 124.0 17.5 1.5 1.8 1.6
1 1/ 4 32 133.4 20.6 2 2.5 2.2
1 1/ 2 40 155.4 22.4 3 3.5 3.3
2 50 165.1 25.4 3.6 4.4 4.2
2 1/ 2 65 190.5 28.4 5.3 6.4 6.1
3 80 209.6 31.8 7 8.5 8.4
3 1/ 2 90 228.6 35.1 8.8 10.7 11
4 100 273.1 38.1 14.5 17.4 17.3
5 125 330.2 44.5 24.4 29.2 29.4
6 150 355.6 47.8 28.7 34.9 36.1
8 200 419.1 55.6 43.4 53.9 58.9
10 250 508 63.5 70.3 86.5 97.5
12 300 558.8 66.5 84.2 103.0 124
14 350 603.3 69.9 98.7 122.0 151
16 400 685.8 76.2 142.0 170.0 214
18 450 743 82.6 173.0 204.0 272
20 500 812.8 88.9 220.0 254.0 349.0
24 600 939.8 101.6 312.0 358.0 533.0

CLASS 900 FLANGE WEIGHT

NPS

(Inches)

DN
(mm)
FLANGE OD
(mm)
THICKNESS
(mm)
SLIP ON
(KGS)
WELD NECK (KGS) BLIND
(KGS)
1/ 2 15 120.7 22.4 1.8 1.9 1.8
3/ 4 20 130 25.4 2.4 2.6 2.4
1 25 149.4 28.4 3.6 3.7 3.6
1 1/ 4 32 158.8 28.4 4 4.3 4.1
1 1/ 2 40 177.8 31.8 5.5 5.9 5.8
2 50 215.9 38.1 10.2 10.8 10
2 1/ 2 65 244.3 41.1 13.9 15 14
3 80 241.3 38.1 11.6 13.7 13.1
4 100 292.1 44.5 19.7 22.5 26.9
5 125 349.3 50.8 31.9 37.4 36.5
6 150 381 55.6 41.1 47.7 47.4
8 200 469.9 63.5 70.7 81.3 82.5
10 250 546.1 69.9 101.0 119 122.0
12 300 609.6 79.2 133.0 157.0 173.0
14 350 641.4 85.6 153.0 180.0 206.0
16 400 704.9 88.9 185.0 217.0 259.0
18 450 787.4 101.6 258.0 292.0 367.0
20 500 857.3 108.0 317.0 362.0 463.0
24 600 1041.4 139.7 606.0 665.0 876.0

CLASS 1500 FLANGE WEIGHT

NPS

(Inches)

DN
(mm)
FLANGE OD
(mm)
THICKNESS
(mm)
SLIP ON
(KGS)
WELD NECK (KGS) BLIND
(KGS)
1/ 2 15 120.7 22.4 1.8 1.9 1.8
3/ 4 20 130 25.4 2.4 2.6 2.4
1 25 149.4 28.4 3.6 3.7 3.6
1 1/ 4 32 158.8 28.4 4 4.3 4.1
1 1/ 2 40 177.8 31.8 5.5 5.9 5.8
2 50 215.9 38.1 10.2 10.8 10.1
2 1/ 2 65 244.3 41.1 13.9 15 14
3 80 266.7 47.8 19.9 19.1
4 100 311.2 53.8 29.9 29.9
5 125 374.7 73.2 55.4 58.4
6 150 393.7 82.6 68.4 71.8
8 200 482.6 91.9 117 122
10 250 584.2 108 194.0 210.0
12 300 673.1 124 288.0 316.0
14 350 749.3 133.4 380.0 420
16 400 825.5 146.1 485.0 558.0
18 450 914.4 162.1 644.0 760.0
20 500 984.3 177.8 775.0 965.0
24 600 1168.4 203.2 1232.0 1558.0

CLASS 2500 FLANGE WEIGHT

NPS

(Inches)

DN
(mm)
FLANGE OD
(mm)
THICKNESS
(mm)
SLIP ON
(KGS)
WELD NECK (KGS)
1/ 2 15 133.4 30.2 3.1 3.0
3/ 4 20 139.7 31.8 3.7 3.5
1 25 158.8 35.1 5.2 5.0
1 1/ 4 32 184.2 38.1 7.7 7.4
1 1/ 2 40 203.2 44.5 10.9 10.4
2 50 235 50.8 16.2 15.6
2 1/ 2 65 266.7 57.2 23.7 22.6
3 80 304.8 66.5 36.2 34.8
4 100 355.6 76.2 55.3 53.9
5 125 419.1 91.9 92.5 90.8
6 150 482.6 108 143.0 141
8 200 552.5 127 215.0 214
10 250 673.1 165.1 406.0 411.0
12 300 762 184.2 572.0 592.0

HOW TO ORDER A FLANGE

The following data shall be communicated to the manufacturer when ordering flanges:

  • Flange type (welding neck, slip-on, threaded, lap joint flange)
  • Flange specification (example ASME B16.5, ASME B16.47 type A, EN 1092-1, JIS, UNI, DIN, etc.)
  • Nominal pipe size (NPS)
  • Flange rating (or class): flanges’ rating can range from 150 to 2500 for ASME flanges, from 5k to 30k for JIS B2220 flanges and KS1503 flanges; from PN 6 to PN 100 for European and Russian-standard flanges (DIN, UNI, EN 1092-1, GOST 12820 / 12821-80); Class 600/3, 1000/3, 1600/3, 2500/3, 4000/3 for SANS/SABS flanges (South African standard for flanges)
  • Pipe schedule (for welding neck and socket weld flanges)
  • Flange facing type (FF; RF, RTJ): according to ASME B16.5, the raised face is the standard facing for flanges (different facings, like RTJ or flat face FF, have to be ordered specifically)
  • Flange surface finish (smooth, stock, concentric serrated, etc)
  • Material grade (forged carbon, stainless, duplex, nickel-alloy steels or, non-ferrous materials as cupronickel, copper, aluminum, and bronze)

Comments

This post currently has 3 responses

  • It’s good to know that flanges can help me join two of my boat’s pipes together. I think I’ll buy a watertight stainless square flange from a good supplier and see if they have other special types of flanges that I can buy. Since I need a flange for high-pressure applications, I’ll have to make sure that they’re compatible with the pipes that I want to bind.

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