Steel pipe sizes "Nominal" refers to pipe in non-specific terms and identifies the diameter of the hole with a nondimensional number (for example – 2-inch nominal steel pipe" consists of many varieties of steel pipe with the only criterion being a 2.375-inch (60.3 mm) outside diameter). Specific pipe is identified by pipe diameter and another non-dimensional number for wall thickness referred to as the Schedule (Sched. or Sch., for example – "2-inch diameter pipe, Schedule 40"). Pipe size is quoted as a “Nominal Pipe Size” or NPS. The origin of the NPS numbers for smaller pipes (< NPS 12) is different to the origin for larger diameter pipes. However, all pipes of a specific NPS number have the same external or outer diameter (OD). The internal diameter will vary depending on the wall thickness of the metal. The reason for this is so that the same structural supports can be used for all piping of a specific NPS number regardless of the wall thickness.
Schedules Steel pipe schedules are a way to describe the wall thickness of the pipe. This is a critical parameter as it is directly related to the strength of the pipe and the suitability for specific applications. A pipe schedule is a dimensionless number and is calculated based on the design formula for wall thickness, given the design pressure and allowable stress. Examples of schedule numbers are as follows: 5, 5S, 10, 20, 30, 40, 50, 60, 80, 100, 120, 140, 160, STD, XS, and XXS—with the most common being schedules 40 and 80. As the schedule number increases, the wall thickness of the pipe increases. The schedule number of a pipe therefore defines the internal diameter, as the OD is fixed by the NPS number. The schedule number is roughly calculated as: Schedule = 1000 x (P/S) where P is the internal service pressure of the pipe (psig) and S is the ultimate tensile strength of the pipe material (psi). SCHEDULE = 1000(P/S) P = internal service pressure of pipe (psig) S = ultimate stress of pipe material (psi)
FREQUENTLY USED ASTM GRADES Material
Pipes A106 Gr A Carbon Steel A106 Gr B A106 Gr C
Fttg A234 Gr WPA A234 Gr WPB A234 Gr WPC
Flg A105 A105 A105
Valves Bolts and Nuts A216 Gr WCB A193 Gr B7 A216 Gr WCB A194 Gr 2H A216 Gr WCB
Carbon Steel A335 Gr P1
A234 Gr WP1
A182 Gr F1
A217 Gr WC1 A193 Gr B7
Alloy High-Temp
A335 Gr P11 A335 Gr P12 A335 Gr P22 A335 Gr P5 A335 Gr P9
Carbon Steel A333 Gr 6 Alloy Low-Temp A333 Gr 3
Austenitic Stainless Steel Material
A312 Gr TP304 A312 Gr TP316 A312 Gr TP321 A312 Gr TP347 Pipes
A234 Gr WP11 A234 Gr WP12 A234 Gr WP22 A234 Gr WP5 A234 Gr WP9
A182 Gr F11 A182 Gr F12 A182 Gr F22 A182 Gr F5 A182 Gr F9
A217 Gr WC6 A217 Gr WC6 A217 Gr WC9 A194 Gr 2H A217 Gr C5 A217 Gr C12
A420 Gr WPL6 A350 Gr LF2 A352 Gr LCB
A320 Gr L7 A420 Gr WPL3 A350 Gr LF3 A352 Gr LC3 A194 Gr 7 A403 Gr WP304 A403 Gr WP316 A403 Gr WP321 A403 Gr WP347 Fttg
A182 Gr F304 A182 Gr F316 A182 Gr F321 A182 Gr F347 Flg
A182 Gr F304 A182 Gr F316 A193 Gr B8 A182 Gr F321 A194 Gr 8 A182 Gr F347 Valves Bolts and Nuts
ASTM Materials Pipes • A106 = This specification covers carbon steel pipe for high-temperature service. • A335 = This specification covers seamless ferritic alloy-steel pipe for high-temperature service. • A333 = This specification covers wall seamless and welded carbon and alloy steel pipe intended for use at low temperatures. • A312 = Standard specification for seamless, straight-seam welded, and cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service.
Fittings • A234 = This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction. • A420 = Standard specification for piping fittings of wrought carbon steel and alloy steel for low-temperature service. • A403 = Standard specification for wrought austenitic stainless steel piping fittings.
Flanges • A105 = This specification covers standards for forged carbon steel piping components, that is, flanges, fittings, Valves, and similar parts, for use in pressure systems at ambient and highertemperature service conditions.
• A182 = This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and Valves and parts for high-temperature service. • A350 = This specification covers several grades of carbon and low alloy steel forged or ringrolled flanges, forged fittings and Valves for low-temperature service.
Valves • A216 = This specification covers carbon steel castings for Valves, flanges, fittings, or other pressure-containing parts for high-temperature service and of quality suitable for assembly with other castings or wrought-steel parts by fusion welding. • A217 = This specification covers steel castings, martensitic stainless steel and alloys steel castings for Valves, flanges, fittings, and other pressure-containing parts intended primarily for high-temperature and corrosive service. • A352 = This specification covers steel castings for Valves, flanges, fittings, and other pressurecontaining parts intended primarily for low-temperature service. • A182 = This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and Valves and parts for high-temperature service.
Bolts and Nuts • A193 = This specification covers alloy and stainless steel bolting material for pressure vessels, Valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications. • A320 = Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for LowTemperature Service. • A194 = Standard specification for nuts in many different material types.
What is Pipe NB (Nominal Bore)? NPS is frequently referred as an NB (Nominal Bore). As such, there is no difference between NB and NPS. NB is also an American way to refer pipe dimensions.
What is DN (Diameter Nominal) Pipe Sizes? DN or Diameter Nominal is International designation (SI or Matric Designator) and also a European equivalent of NPS to show pipe sizes. Here, you have to note that DN shows pipe sizes differently than NPS. For example, 2” pipe is simply mentioned as DN 50. You can get any NPS to DN by multiplying it with 25.
Standard Pipe Sizes and Dimensions A Table of the Most Common Standard Pipe Sizes Nominal Bore 1/2 inch (DN 15 mm), Outside Diameter 21.34 mm
Schedule
Sch. Sch. STD XS 5 10
Sch.16 XXS 0
Wall Thickness 1.65 2.11 2.77 3.73 4.78 7.47 (mm) Internal Diameter 18.04 17.12 15.8 13.9 11.78 6.4 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 3/4 inch (DN 20 mm), Outside Diameter 26.67 mm Sch. Sch. Sch.16 Schedule STD XS XXS 5 10 0 Wall Thickness 1.65 2.11 2.87 3.91 5.56 7.82 (mm) Internal Diameter 23.37 22.45 20.93 18.85 15.55 11.03 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 1 inch (DN 25 mm), Outside Diameter 33.40 mm Sch. Sch. Sch.16 Schedule STD XS XXS 5 10 0 Wall Thickness 1.65 2.77 3.38 4.55 6.35 9.09 (mm) Internal Diameter 30.1 27.86 26.64 24.3 20.7 15.22 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 1.5 inch (DN 40 mm), Outside Diameter 48.3 mm Sch. Sch. Sch.16 Schedule STD XS XXS 5 10 0 Wall Thickness 1.7 2.8 3.7 5.1 7.1 10.2 (mm) Internal Diameter 45 42.7 40.9 38.1 34 27.9 (mm)
Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 2 inch (DN 50 mm), Outside Diameter 60.3 mm Sch. Sch. Sch.16 Schedule STD XS XXS 5 10 0 Wall Thickness 1.7 2.8 3.9 5.5 8.7 11.1 (mm) Internal Diameter 56.9 54.7 52.5 49.3 42.9 38.1 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 3 inch (DN 80 mm), Outside Diameter 88.9 mm Sch. Sch. Sch.16 Schedule STD XS XXS 5 10 0 Wall Thickness 2.1 3 5.5 7.6 11.1 15.2 (mm) Internal Diameter 84.7 82.9 77.9 73.7 66.7 58.5 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 4 inch (DN 100 mm), Outside Diameter 114.3 mm Sch. Sch. Sch.12 Sch.16 Schedule STD XS XXS 5 10 0 0 Wall Thickness 2.1 3 6 8.6 11.1 13.4 17.1 (mm) Internal Diameter 110.1 108.3 102.3 97.1 92.1 87.5 80.1 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 5 inch (DN 125 mm), Outside Diameter 141.3 mm Sch. Sch. Sch.12 Sch.16 Schedule STD XS XXS 5 10 0 0 Wall Thickness 2.8 3.4 6.6 9.5 12.7 15.9 19 (mm)
Internal Diameter 135.7 134.5 128.1 122.3 115.9 (mm) Schedule 40 has same dimension s as STD. Schedule 80 has same dimension s as XS.
109.5
103.2
Nominal Bore 6 inch (DN 150 mm), Outside Diameter 168.3 mm Sch. Sch. Sch.12 Sch.16 Schedule STD XS XXS 5 10 0 0 Wall Thickness 2.8 3.4 7.1 11 14.3 18.3 22 (mm) Internal Diameter 162.7 161.5 154.1 146.3 139.7 131.7 124.3 (mm) Schedule 40 has same dimensions as STD. Schedule 80 has same dimensions as XS. Nominal Bore 8 inch (DN 200 mm), Outside Diameter 219.1 mm Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Schedule Sch. 40 Sch. 60 XXS 5 10 20 30 80 100 120 140 160 Wall Thickness 2.8 3.8 6.4 7 8.2 10.3 12.7 15.1 18.2 20.6 23 22.2 (mm) Internal Diameter 213.5 211.5 206.3 205.1 202.7 198.5 193.7 188.9 182.7 177.9 173.1 174.7 (mm) Nominal Bore 10 inch (DN 250 mm), Outside Diameter 273.0 mm Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Schedule Sch. 40 Sch. 60 XXS 5 10 20 30 80 100 120 140 160 Wall Thickness 3.4 4.2 6.4 7.8 9.3 12.7 15.1 18.2 21.4 25.4 28.6 25.4 (mm) Internal 266.2 264.6 260.2 257.4 254.4 247.6 242.8 236.6 230.2 222.2 215.8 222.3
Diameter (mm) Nominal Bore 12 inch (DN 300 mm), Outside Diameter 323.9 mm Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Schedule Sch. 30 Sch. 40 5 5 10 20 40 60 80 100 120 140 160 Wall Thickness 4 4.2 4.6 6.4 8.4 9.5 10.3 14.3 17.5 21.4 25.4 28.6 33.3 (mm) Internal Diameter 315.9 315.5 314.7 311.1 307.1 304.9 303.3 295.3 228.9 281.1 273.1 266.7 257.3 (mm) Nominal Bore 14 inch (DN 350 mm), Outside Diameter 355.6 mm Sch. Sch. Sch. Sch. Sch. Sch. Sch. Schedule Sch. 30 Sch. 40 XS 5 10 10 20 60 80 100 Wall Thickness 4 4.8 6.4 7.9 9.5 11.1 12.7 15.1 19.1 23.8 (mm) Internal Diameter 347.7 346 342.9 339.8 336.6 333.3 330.2 325.4 317.5 308 (mm) STD has same dimensions as Schedule 30.
Sch. Sch. Sch. 120 140 160 27.8 31.8 35.7
300 292.1 284.2
Nominal Bore 16 inch (DN 400 mm), Outside Diameter 406.4 mm Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Sch. Schedule Sch. 30 Sch. 40 5 10 10 20 60 80 100 120 140 160 Wall Thickness 4.2 4.8 6.4 7.9 9.5 12.7 16.6 21.4 26.2 31 36.5 40.5 (mm) Internal Diameter 398 396.8 393.7 390.6 387.4 381 373.1 363.5 354 344.5 333.4 325.4 (mm) STD has same dimensions as Schedule 30. XS has the same dimensions as Schedule 40. Note: You can easily convert inch dimension to mm by multiplying it with 25.4 and rounding as follows:1. Outside diameter above 16 inches rounded to nearest 1 mm 2. Outside diameter 16 inches and below rounded to nearest 0.1 mm
3. Pipe wall thickness are rounded to nearest 0.01 mm
Dimension Tolerance for Carbon Steel and Stainless Steel Pipe Sizes and Schedule As per ASTM A530/A530M-12 and ASTM A999/A999M-15 Common dimension tolerances are listed in ASTM A530. However, each product has its own requirements and when given in that specification that will govern over the A530. Description Size Weight NPS 12 (DN 300) and under Weight NPS 14 (DN 350) and above (Note-1) Wall Thickness 1⁄8 to 2 ½, incl., all t/D ratios (Note-2) 3 to 18 incl., t/D up to 5 % incl. 3 to 18 incl., t/D > 5 % Seamless and 20 and larger, welded, all t/D ratios Welded Pipe (Note-3) 20 and larger, seamless, t/D up to 5 % incl. 20 and larger, seamless, t/D > 5 % Forged and Bored Pipe Cast Pipe Inside Diameter for Cast Pipe Outside Diameter (Note-4) 1⁄8 to 11⁄2, incl Over 1 ½ to 4, incl Over 4 to 8, inc Diameter Over 8 to 18, incl Outside Over 18 to 26, incl Over 26 to 34, incl Over 34
Over 10% 10%
Under 3.50% 5%
20.00% 22.50% 15.00%
12.50% 12.50% 12.50%
17.50%
12.50%
22.50%
12.50%
15.00%
12.50%
1/8 in.(3.2mm)
Nil
1/6 in.(1.6mm)
Nil
Nil
1⁄16 in. (1.6 mm)
1⁄64 in. (0.4mm) 1/32 in. (0.8mm) 1/16 in. (1.6mm) 3/32 in. (2.4mm) 1/8 in. (3.2mm) 5/32 in. (4.0mm) 3/8 in. (4.8mm)
1/32 in. (0.8mm) 1/32 in. (0.8mm) 1/32 in. (0.8mm) 1/32 in. (0.8mm) 1/32 in. (0.8mm) 1/32 in. (0.8mm) 1/32 in. (0.8mm)
Note-1: Pipe of NPS 4 (DN 100) and smaller may be weighed in lots; pipe in sizes larger than NPS 4 (DN 100) shall be weighed separately.
Note-2: t = Nominal wall thickness. D = Outside diameter.
ď&#x201A;ˇ
Note-3: For welded pipe, the weld area shall not be limited by the over tolerance.
ď&#x201A;ˇ
Note-4: For thin-wall pipe, the ovality in any one cross-section shall not exceed 1.5 % of the specified outside diameter.
______________________________________________________________________________ The Steel Pipes Factory, Metallica, established in 1975, is a professional hot rolled seamless steel pipe stockholder and manufacturer in India. Now, we mainly supply seamless steel pipes according to American ASTM, API 5L, API 5CT, Japanese JIS G3441, G3458, G3462 standard, German DIN standard, etc. Till now, our products have been exported to Southeast Asia, Middle East Area, Europe, Australia, South America, Africa, etc. With advanced quality, competitive price and sincere service, we have obtained wide trust and support from domestic and abroad customers. Your Inquiry is Highly Appreciated.