Glossary: Pipe Schedule
A standardized designation system that represents the nominal wall thickness and pressure capability rating of piping systems.
Nominal Pipe Sizing (NPS) and Schedule Mappings
Pipe schedule codes determine pipe inside diameters and pressure ratings under standards like ASME B36.10M. While the outside diameter (OD) remains constant for a given nominal size, the inside diameter (ID) shrinks as schedule wall thicknesses increase:
- Schedule 40: The standard utility wall thickness for residential plumbing and low-pressure fluid transport.
- Schedule 80: Heavy-wall pipe designed for industrial plumbing, chemicals, and high-pressure service.
- Dimensional Variance: A 2-inch Nominal Schedule 40 pipe has an ID of 2.067 inches, whereas a 2-inch Schedule 80 pipe has an ID of 1.939 inches due to its thicker steel walls.