How thick is schedule 40 steel pipe

Schedule 40 is frequently used in engineering construction, industrial piping, and fluid transportation projects. A common question is: how thick is Schedule 40 steel pipe? Understanding this specification is crucial, as it determines the balance between pipe strength, pressure resistance, and cost.

What is schedule 40 steel pipe?

"Schedule" (SCH for short) indicates the wall thickness grade of steel pipe, defined by ASME B36.10 (carbon steel) and ASME B36.19 (stainless steel) standards. The number "40" represents the wall thickness level for a specific pressure rating; the higher the number, the thicker the pipe wall and the stronger its pressure resistance.

Its core significance lies in:

Standardized design: Unified wall thickness specifications ensure piping system compatibility and pressure resistance safety.

Thickness and size relationship: Wall thickness (unit: inches or millimeters) varies with nominal diameter (NPS, unit: inches), rather than being a fixed value.

Schedule 40 steel pipe Wall Thickness Table:

Factors affecting the wall thickness of SCH 40 pipes

1. Material type: Different materials have different pressure resistance and strength for the same specifications, therefore the wall thickness may vary slightly within the standard range.

Carbon steel pipes: Commonly used for low-pressure fluid transportation (such as water and gas), Sch 40 meets general pressure requirements.

Stainless steel pipes (e.g., 316 SS): The "S" suffix in Sch 40S indicates the stainless steel standard. The wall thickness is the same as carbon steel Sch 40, but the corrosion resistance is better.

2. Manufacturing process: The manufacturing method of the steel pipe also affects the actual wall thickness uniformity.

Seamless pipes: Formed by piercing and rolling or cold drawing, resulting in more uniform wall thickness and smaller tolerances.
Welded pipes (ERW, LSAW, SSAW): Due to the presence of welds, the standard allows a wall thickness deviation range of ±12.5%.

3. Anti-corrosion coating: If the pipe has an anti-corrosion layer, galvanized layer, plastic lining, or other processes applied internally or externally, the actual total wall thickness will increase.

Wall thickness variations due to different manufacturing processes are normal and permissible within the standard.

Common applications of SCH 40 pipes:

Oil and gas transmission pipelines
Water treatment and drainage systems
Structural supports and mechanical equipment frames
Industrial process piping
HVAC and fire protection systems

Read more：ASTM A106 schedule 40 dimensions