This is a number system setup by ANSI and ASME for the purpose of standardization to designate the size of a pipe. Pipe sizes are normally referred to as "nominal pipe size" (NPS). For pipe sizes from 1/8" thru 12" (nominal inside diameter), 14" and larger (actual outside diameter). The larger the schedule number the larger the pipe size. The 1/8" thru 12" diameters differ from the actual inside diameter.
The pipe schedule number is a designation used to specify the wall thickness of pipes. It provides a standardized way of categorizing pipes based on their wall thickness relative to their nominal pipe size (NPS). The schedule number helps ensure consistency and compatibility in pipe systems across various industries and applications. Pipe schedules are commonly used for steel pipes, both carbon steel and stainless steel. The schedule number is often combined with the nominal pipe size to create a complete pipe specification. For example, you might see designations like "Schedule 40," "Schedule 80," and so on.
How the pipe schedule number works
- Schedule Number Meaning:
- The higher the schedule number, the thicker the wall of the pipe is relative to its nominal size.
- A higher schedule number indicates a stronger and more robust pipe that can handle higher pressures and stresses.
- Relationship with Wall Thickness:
- As the schedule number increases, the wall thickness of the pipe also increases.
- The outside diameter (OD) of the pipe remains constant for a given nominal size, regardless of the schedule.
- Pressure Ratings:
- Each schedule has associated pressure ratings, indicating the maximum pressure the pipe can handle safely.
- These ratings are determined by industry standards and codes.
- Schedule 40 - A common schedule used for a range of applications where moderate pressures are involved.
- Schedule 80 - A thicker-walled pipe with higher pressure ratings, suitable for more demanding applications.
It's important to note that the pipe schedule system doesn't have a direct mathematical calculation to determine the schedule based on pressure or other factors. Instead, it's based on historical designations and standardization efforts to ensure uniformity in pipe dimensions and wall thicknesses.
When selecting a pipe schedule, consider factors like the operating pressure, temperature, type of fluid being transported, and any industry standards or regulations that apply to your specific application. Consulting relevant standards such as ASME B36.10 (carbon steel pipes) or ASME B36.19 (stainless steel pipes) is important for accurate specification of pipes with the appropriate schedule number for your needs.