Schedule (Sch 40 / Sch 80)
/glossary/scheduleASME B36.10 wall-thickness designation that must be paired with NPS, material, and the design code.
Schedule is the ASME B36.10 wall column for a named NPS. Kanpur process shops at Panki order Sch 40 or Sch 80 on ASTM A106 line pipe; JJM and PWD water BOQs use IS 1239 Light, Medium, or Heavy instead. On the site chart, 2 inch NPS Sch 40 is 3.91 mm wall. Size, wall, allowable stress, and the design code set the rating. Yard process-pipe offers are GST 18% extra as the budgeting basis; the tax invoice applies the rate in force.
In detail
Schedule is a standardised wall-thickness designation for welded and seamless wrought steel pipe under ASME B36.10-2022. The 2022 edition revises B36.10M-2018 and standardises dimensions for high or low temperatures and pressures; it does not assign a working-pressure rating by itself. Size, actual minimum wall, material allowable stress at design temperature, corrosion allowance, joint efficiency, fittings, and the governing code set the rating. On the site schedule chart, 2 inch NPS is 60.3 mm OD with Sch 40 wall 3.91 mm and Sch 80 wall 5.54 mm. State NPS or DN, the schedule or exact millimetre wall, the material specification, and the code edition on the PO.
What a schedule number is, and what it is not
A schedule number picks a listed wall for a given NPS on ASME B36.10. The 2022 edition, issued 30 June 2022, revises B36.10M-2018. Its public scope covers the standardisation of dimensions of welded and seamless wrought steel pipe for high or low temperatures and pressures. Table 2-1 lists those dimensions and masses.
The word pipe in that standard means tubular products of dimensions used for pipeline and piping systems, as distinct from tube. Boiler tubes under SA192 or SA213 are ordered by OD and minimum wall, not by NPS and schedule.
Schedule is not a pressure class. It is not IS 1239 Light, Medium, or Heavy. It is not a material grade. Sch 40 on A106 Grade B and Sch 40 on A53 Type E share a wall table and still remain two product specifications.
The site pipe schedule chart follows B36.10M walls in millimetres. Read the millimetre wall onto the PO so the mill cannot ship another column under the same NPS stamp.
Who should order by schedule, and who should order by class
Order NPS and schedule when the approved piping class, isometric, or material line uses ASME B36.10 walls. Panki fabricators write Sch 40 or Sch 80 on A106 and A53 process spools. Sugar-mill steam headers follow the IBR drawing: schedule pipe when the line is SA-106, OD times wall when the line is a boiler tube.
Order NB and Light, Medium, or Heavy when the BOQ cites IS 1239. Kanpur JJM house connections, PWD water risers, and most fire hydrant GI stay on class, not on Sch 40.
Do not convert Medium class into Sch 40 by matching OD. At 80 NB the class chart wall is 4.0 mm Medium; 3 inch Sch 40 on the schedule chart is 5.49 mm. Those two walls are different products.
Do not order schedule on DIN 2391 hydraulic barrel tube. Dada Nagar cylinder shops buy OD times wall, then hone or skive the bore.
Schedule walls used on Kanpur process RFQs
The table repeats the site schedule chart for the sizes Panki and Fazalganj fabricators ask for most. Mass uses the site formula in the worked example below. The last column is the buying use, not a bar rating.
| NPS (DN) | OD (mm) | Sch 40 wall (mm) | Sch 80 wall (mm) | Kanpur buying use |
|---|---|---|---|---|
| 2 inch (DN 50) | 60.3 | 3.91 | 5.54 | Small-bore process and utility spools |
| 3 inch (DN 80) | 88.9 | 5.49 | 7.62 | Panki header and branch pipe |
| 4 inch (DN 100) | 114.3 | 6.02 | 8.56 | Process and fire-main welded lines |
| 6 inch (DN 150) | 168.3 | 7.11 | 10.97 | Larger process and water transmission |
Sch 160 and XXS sit on the same chart for heavier walls. Stainless work uses B36.19 40S and 80S, a different table. Copy the chart that the piping class names.
How to specify schedule on an RFQ
A line that says only Sch 40 pipe leaves NPS, material, and ends open. Write one product. Attach the isometric or the piping-class extract.
- Product: ASTM A106, ASTM A53 Type E or S, or the exact specification on the drawing, plus revision.
- Size: NPS or DN, then schedule or the millimetre wall from the site chart.
- Grade: A106 A, B, or C; A53 A or B. Class language belongs on IS 1239 lines only.
- Length: SRL, DRL, or cut-to-length with a stated tolerance.
- End: plain, bevel to the joint detail, or threaded and coupled on small NPS.
- Finish: black, or galvanized only when the product standard and the PO allow zinc.
- Documents: EN 10204 3.1 MTC. Steam pipe takes Form III-A, a tube takes Form III-B, and a mounting or fitting takes Form III-C.
- Inspection: mill, or TPI by SGS, Bureau Veritas, Lloyds, or TUV when the ITP names the agency.
- Quantity in metres or MT. Handover at the Kanpur yard or FOR the named city. Add GST 18% extra on the steel line.
Worked mass on six-inch Sch 40 versus Sch 80
The site schedule chart gives 6 inch NPS as OD 168.3 mm, Sch 40 wall 7.11 mm, and Sch 80 wall 10.97 mm. Theoretical plain-end mass is W = (OD − t) × t × 0.02466 kg/m.
Sch 40: (168.3 − 7.11) × 7.11 × 0.02466 = 161.19 × 7.11 × 0.02466 = 28.26 kg/m. Twelve 6 m lengths are 12 × 6 × 28.26 = 2,034.72 kg, about 2.03 MT.
Sch 80: (168.3 − 10.97) × 10.97 × 0.02466 = 157.33 × 10.97 × 0.02466 = 42.56 kg/m. The same twelve lengths are 12 × 6 × 42.56 = 3,064.32 kg, about 3.06 MT.
The seamless price list band for 6 inch Sch 40 is ₹75-92 per kg and for Sch 80 is ₹90-110 per kg, ex-warehouse Kanpur, as of 24 May 2026. The Sch 40 steel line is 2,034.72 × 75 = ₹1,52,604 to 2,034.72 × 92 = ₹1,87,194. The Sch 80 steel line is 3,064.32 × 90 = ₹2,75,789 to 3,064.32 × 110 = ₹3,37,075, before GST and freight. Compare those two offers only when both use the same NPS, wall, and count.
Common schedule mistakes on Kanpur POs
In practice, the first failure is NPS without a wall. A 4 inch stamp on the rack can be 6.02 mm Sch 40 or 8.56 mm Sch 80. Gauge the wall before the bundle is cut.
The second failure is treating Sch 40 as a working-pressure stamp. NPS, millimetre wall, material stress at temperature, and the adopted code set the working pressure. The 6 inch example above is a mass and rupee check, not a bar figure.
The third failure is filling an IS 1239 Medium water line with Sch 40 ERW because both sounds like standard wall. Class and schedule use different tables. See IS 1239 versus IS 3589 when the OD also crosses 168.3 mm.
The fourth failure is ordering boiler tube as 2 inch Sch 80. Superheater and generating-bank tubes take OD and minimum wall. Schedule language belongs on the steam pipe, not on the bank.
Standards that govern schedule walls
ASME B36.10-2022 is the dimensional standard. Section 9 covers wall-thickness designations and Section 10 covers wall-thickness selection. The catalogue page retrieved 2026-09-05 states that the standard covers dimensions of welded and seamless wrought steel pipe for high or low temperatures and pressures.
ASTM A106/A106M-26 scope 1.1 points to nominal (average) wall per ASME B36.10M for NPS 1/8 to NPS 48. ASTM A53 uses the same NPS tables on this site. Neither material specification turns a schedule number into a design pressure.
IS 1239 Part 1:2004 is the Indian class-wall document. The standard covers 6 mm to 150 mm NB water and gas tube; RP Sales stocks 15 to 150 mm NB. IS 3589:2001 starts at 168.3 mm OD for water and sewage and uses Fe grades and project walls, not Sch 40 as a default.
IBR steam pipe uses Form III-A. Tubes use Form III-B. Mountings and fittings use Form III-C. A schedule stamp on the pipe does not pick the form.
Buying schedule pipe in Kanpur
Process fabricators around Panki, about 12 km from the Bartan Bazar stockyard, collect A106 Sch 40 and Sch 80 from the yard and weld the same week. Jajmau, about 10 km east, buys more IS 1239 class GI than schedule pipe. Keep those two RFQs on separate lines.
See seamless pipes in Kanpur, steel pipes in Kanpur, the Sch 40 versus Sch 80 comparison, and the Kanpur steel market. Outstation drops to Lucknow, Agra, and Jhansi still need NPS, schedule, and grade on the packing list.
Stocked carbon schedule sizes on the glossary lead-time entry leave in 3-7 days. A Sch 160 or XXS indent follows the mill-direct 14-21 day band.
Schedule versus IS 1239 class at the same OD
Buyers mix the two languages because 2 inch NPS and 50 NB share 60.3 mm OD. The walls do not match. The pipe-weight table lists 50 NB Medium at 3.6 mm and 5.03 kg/m. The schedule chart lists 2 inch Sch 40 at 3.91 mm and 5.44 kg/m.
At 6 inch the mismatch grows. The class-weight rows and the price lists put 150 NB at 165.1 mm OD, while the schedule chart and the IS 3589 lower bound sit at 168.3 mm. A 150 NB Heavy water tube is not a 6 inch Sch 40 process pipe.
Write the standard first, then the size language that standard uses. Class on an IS 1239 line. Schedule on an A106 or A53 line. Project wall on an IS 3589 trunk main.
STD, XS, XXS, and stainless 40S
The site chart labels the Sch 40 column as Sch 40/STD and the Sch 80 column as Sch 80/XS for the sizes it prints. STD equals Sch 40 only up to NPS 10; XS equals Sch 80 only up to NPS 8. Above those sizes the two columns diverge. XXS is a separate heavier column. Those labels are wall names. They are not a licence to raise design pressure.
Stainless piping classes that adopt ASME B36.19 use 5S, 10S, and 40S on the site standards page. 40S is not automatically the same millimetre wall as carbon Sch 40 at every NPS. Copy the stainless table when the material is TP304 or TP316.
If the drawing shows a non-standard wall, write the millimetre thickness and skip the schedule nickname. B36.10 permits other dimensions when the product specification accepts them.
Packing schedule pipe for UP and Bihar
Tag each bundle with NPS, schedule, grade, and heat. A mixed truck to Patna or Varanasi that only says 4 inch is how Sch 40 and Sch 80 arrive in one stack.
Cap bevelled ends. Keep Sch 80 heavier lifts on the deck plan so the crane chart is honest. Trucks leave the Bartan Bazar / Basanti Nagar (208014) yard for destinations across Uttar Pradesh, Bihar, Madhya Pradesh, Delhi NCR, and Uttarakhand.
Send the RFQ with NPS, schedule or wall, material, and ends. A store that writes standard pipe on every line is how a 4.0 mm Medium water lot is compared with a 5.49 mm Sch 40 process lot.
Where you'll meet this in procurement
You will meet Schedule (Sch 40 / Sch 80) on size charts, mill quotes, and fitment checks. Cross-check Schedule (Sch 40 / Sch 80) against OD, wall thickness or schedule, length, and end finish so the delivered pipe matches flanges, fittings, and pressure duty—not just a familiar nominal label.
Related terms
Related resources
Key points
- Schedule is a B36.10 wall column for a named NPS, not a working-pressure rating.
- 2 inch Sch 40 is 60.3 × 3.91 mm; 2 inch Sch 80 is 60.3 × 5.54 mm on the site chart.
- 6 inch Sch 40 is 28.26 kg/m and Sch 80 is 42.56 kg/m from (OD − t) × t × 0.02466.
- IS 1239 water tube uses Light, Medium, or Heavy class, not Sch 40 as a synonym.
- Kanpur yard bands are GST 18% extra. Write NPS and the millimetre wall on the PO.
Frequently asked questions
Sources
- ASME B36.10-2022. Welded and Seamless Wrought Steel Pipe: scope covering dimensional standardisation for high or low temperatures and pressures; Table 2-1; issued 30 June 2022 as revision of B36.10M-2018 (American Society of Mechanical Engineers)
- ASME B36.10-2022 table of contents. Sections 9 Wall-Thickness Designations and 10 Wall-Thickness Selection; Table 2-1 Dimensions and Weights (Masses) (American Society of Mechanical Engineers)
- ASTM A106/A106M-26. Seamless Carbon Steel Pipe for High-Temperature Service, scope 1.1 nominal wall per ASME B36.10M (ASTM International)
- IS 1239 (Part 1):2004. Steel Tubes, Tubulars and Other Wrought Steel Fittings, Part 1 Steel Tubes: Light/Medium/Heavy class contrast (Bureau of Indian Standards)
- Indian Boiler Regulations, 1950. Forms index: III-A steam pipes, III-B tubes, III-C boiler mountings and fittings (Central Boilers Board, Government of India)