Schedule 40 Carbon Steel Pipe

What is a Pipe Schedule?

A pipe schedule (SCH) is a measure of a steel pipe’s nominal wall thickness.

In the past, metal fabricators used three pipe dimensions — standard, extra strong, and double extra strong. Just having these three undetermined dimensions wasn’t helpful, though. So today, steel pipes come in 14 different schedules.
The most commonly used one is schedule 40.

Schedule 40 Carbon Steel Pipe Meaning:

Schedule 40 Carbon Steel Pipe is a medium-walled carbon steel pipe manufactured according to the ASME B36.10 standard. It is one of the internationally accepted pipe wall thickness grades. The "40" in its name represents the wall thickness series number. The larger the number, the thicker the wall thickness (e.g., Sch 80 is thicker than Sch 40). All pipes have different specifications, which indicate the size and pressure capacity of the pipe. Husteel Industry Group is a leading supplier and manufacturer of Sch 40 carbon steel pipe products.

Carbon steel comes in various grades and chemical compositions. But the pressure capacity is measured and classified. Sch 40 carbon steel pipe is a medium-pressure capacity pipe with a diameter of up to 24 inches and a wall thickness of up to 46 mm.

Implementation standards:
ASTM A106: Seamless, high temperature and high pressure.
ASTM A53: Welded/seamless, general purpose.
API 5L: Oil and gas transmission pipeline.

Manufacturing process:
It can be divided into seamless pipes (hot rolled/cold drawn) or welded pipes (ERW/SAW).

In addition to material strength, the ratio of diameter to wall thickness determines whether it is a Sch 40 pipe or other specifications. The specification depends on the outer diameter, wall thickness and pressure bearing capacity of the material. The weight of Sch 40 carbon steel pipe depends on its manufacturing material. The more carbon added to the steel, the lighter the weight of the pipe. But wall thickness and diameter also play a role. Since Sch 40 pipe belongs to the medium pressure grade, the pipe wall thickness and weight are also in the medium range. Please refer to the table below for details.

Pipe Sch 40 Chart, Dimensions, Weight And Pipe Wall Thickness

Chemical Composition of Schedule 40 Carbon Steel Pipe:

Schedule 40 pipe refers to the nominal wall thickness, not the grade. Therefore, the chemical composition of a pipe schedule is not necessarily uniform.

However, schedule 40 pipe is made from low-carbon steel, usually grade A53 steel pipe. Its chemical composition also varies across types and welds, but as a point of reference, type S seamless weld A53 steel looks something like this:

Carbon – 0.25% (max)
Manganese – 0.95% (max)
Phosphorous – 0.05% (max)
Sulfur – 0.045% (max)
Copper – 0.4% (max)
Nickel – 0.4% (max)
Chromium – 0.4% (max)
Molybdenum – 0.15% (max)
Vanadium – 0.08% (max)

Common materials of Schedule 40 (Sch 40) steel pipe:

Schedule 40 steel pipe is a general-purpose pipe, and its material selection directly affects pressure resistance, corrosion resistance and applicable scenarios.

1. Carbon steel (such as ASTM A106/A53): A106 seamless is used in high temperature and high pressure environments, with a tensile strength of ≥415 MPa and a yield strength of ≥240 MPa. A53 GR.B seamless/welded pipe is used in medium and low pressure environments.
2. Stainless steel (such as ASTM A312 304/316): Strong corrosion resistance, 316L stainless steel has a molybdenum content of 2%-3%, suitable for chemical and marine environments.
3. Alloy steel (such as ASTM A335 P11/P22): Contains elements such as chromium and molybdenum, is resistant to high temperature and high pressure, and is often used in power station boiler pipes.
4. Galvanized steel (ASTM A53 galvanized pipe): The surface of Sch 40 steel pipe is galvanized, which is corrosion-resistant and can extend the service life.

Application areas of Schedule 40 carbon steel pipe:

(1) Fluid transportation
Water system: tap water, fire sprinkler (low pressure), heating, ventilation and air conditioning (HVAC).
Gas: compressed air, low-pressure natural gas.
Chemical industry: non-corrosive liquids (such as cooling water, oil). Corrosive media need to be lined or made of stainless steel.

(2) Building and structure
Drainage/ventilation: building drainage pipe (DWV), ventilation duct.
Supporting structure: SCH 40 carbon steel pipe is used as supporting structure, such as scaffolding, shelves, guardrails.

(3) Industrial and municipal engineering
Oil/gas: low-pressure pipelines, wellhead auxiliary pipelines.

(4) Agricultural field
Agricultural irrigation: main pipelines, sprinkler systems (galvanized pipes or PVC).

(5) Other uses
DIY projects: furniture, lamps, garden facilities (creative transformation).

Sch 40 steel pipe selection considerations:

Pressure requirements: The design pressure needs to be calculated according to ASME B31.3 and other specifications to avoid overpressure.

Corrosive environment:
Carbon steel needs to be galvanized or epoxy coated in humid or acidic environments.
Stainless steel is suitable for high corrosion occasions, but the cost is higher.

Temperature limit:
Carbon steel long-term use temperature ≤400°C, high temperature requires alloy steel.
PVC/CPVC SCH 40 pipe is only suitable for low temperature (usually ≤60°C).

Frequently Asked Questions:

Q: What is the difference between SCH 40 and SCH 80 steel pipe?

A: SCH 80 pipe has thicker wall thickness than SCH 40 and stronger pressure bearing capacity.

Pressure level:
SCH 40 is suitable for medium and low pressure (usually ≤200 psi).
SCH 80 is suitable for high pressure (300~1000 psi, depending on the material). SCH 80 is 30%~50% more expensive than SCH 40 (due to increased wall thickness and more material consumption).

Cost: SCH 80 is more expensive, but safer.

Q: Can Sch 40 steel pipes be used for natural gas transmission?
A: Galvanized Sch 40 pipes can be used for low-pressure courtyard pipe networks, and the main line needs to have a wall thickness of Sch 80 or above.

Q: What is the difference between Sch 40 seamless and welded steel pipes?
A: Sch 40 includes two processes: seamless/welded. The weld seams of welded pipes require 100% radiographic inspection.

Q: What is the difference between Schedule 40 and Sch 40S?
A: Sch 40: General wall thickness, including carbon steel/stainless steel.
Sch 40S: Specifically refers to stainless steel thin-walled pipes (such as ASTM A312), with a wall thickness 5-10% thinner than ordinary Sch 40, used in light-load scenarios to save costs.

Q: Can Schedule 40 steel pipes be buried underground?
A: Yes, but they need to be anti-corrosive.

Carbon steel: 3PE coating + cathodic protection (lifespan ≥ 30 years).
Stainless steel: Direct burial (316 is resistant to soil corrosion).
PVC: virgin resin + UV stabilizer (anti-ultraviolet degradation).

Direct burial is prohibited: unprotected galvanized pipes (risk of perforation within 5 years).

Q: What is the maximum operating temperature of Schedule 40 steel pipes?

A: Carbon steel: long-term temperature resistance of 400°C, short-term limit: 450°C.
304 stainless steel: long-term temperature resistance of 800°C, short-term limit: 900°C.
Note: Carbon steel will creep at high temperatures and needs to be used at a reduced rating.

Q: How to distinguish true and false Schedule 40 steel pipes?

A: Check the label: the pipe body should be marked with "SCH 40", material (such as A53), and manufacturer code.
Measuring wall thickness: Use a caliper to measure and compare with the ASME B36.10 standard value (e.g. 2" pipe wall thickness is 3.91mm).
Verification: Require suppliers to provide MTR (material report) and third-party inspection report.

Read more : Schedule 40 Pipe VS Schedule 80 Pipe