The pipe schedule (SCH) is a designation used to indicate the thickness of the walls of a steel pipe. It is represented by a number, and this number is not a direct measurement of the actual wall thickness but rather a reference to a set of standardized thicknesses established by the American National Standards Institute (ANSI). These standards are determined based on the nominal size and pressure rating of the pipe.
Schedule 40 (SCH 40):
Schedule 40 Pipe is a specific pipeline specification that conveys information about the wall thickness and pressure-bearing capacity of the pipe. In this context, "SCH" stands for Schedule, indicating the pressure-bearing capacity level, and "40" represents the wall thickness of the pipe in 1/1000 of an inch.
According to the American pipeline standard ANSI/ASME B36.10M, the specific specifications for SCH 40 steel pipe include:
Outside Diameter:Ranging from 1/8 inch to 30 inches, covering various pipeline applications.
Wall Thickness: 0.040 inches, approximately 1.016 mm.
Nominal Diameter Ratio (D/t): 0.85.
Minimum Yield Strength: Specified by the standard as 35000 PSI or 240 MPa.
Standard Working Pressure: Up to 700 PSI, approximately 48.3 Bar.
Schedule 40 (SCH 40) Pipe Summary:
The wall thickness is 0.040 inches, providing a balance of strength without excessive weight.
High pressure-bearing capacity, with a maximum working pressure of up to 700 PSI, suitable for general industrial pipelines.
Minimum yield strength of 35,000 PSI ensures pipeline firmness.
Wide outer diameter range from 1/8 inch to 30 inches, meeting diverse diameter needs.
A commonly used and versatile pipe specification suitable for most industrial piping systems.
Schedule 80 (SCH 80) Pipe Summary:
The wall thickness is 0.080 inches, offering high strength but resulting in a heavier pipe.
Very high pressure-bearing capacity, with a maximum working pressure of up to 3000 PSI, suitable for high-pressure pipeline systems.
Minimum yield strength of 35,000 PSI, ensuring a high safety factor.
Wide outer diameter range from 1/8 inch to 30 inches, similar to SCH 40.
Selected for applications requiring thicker walls and higher pressure-bearing capacity, where weight is not a primary concern.
Cost Considerations:
Schedule 40 parts are generally more affordable than Schedule 80 due to the latter's thicker sidewall requiring more material and potential colorant additives, increasing production costs.
In summary, the choice between SCH 40 and SCH 80 depends on the specific requirements of the pipeline system. SCH 40 is commonly used for general applications, offering a balance of strength and weight, while SCH 80 is chosen for high-pressure systems where thicker walls and greater strength are essential, even though it comes with the trade-off of increased weight and cost.
