In pipe sizing, what does 'schedule' refer to?

• A. Wall thickness
• B. Temperature rating
• C. Wall thickness/pressure rating (e.g., Schedule 40, Schedule 80)
• D. Outside diameter

Answer: (C)

Schedule in pipe sizing refers to the standardized wall thickness of the pipe and the corresponding pressure rating, shown by numbers like Schedule 40 or Schedule 80. These schedules indicate how thick the pipe wall is and how much internal pressure the pipe is designed to withstand. A higher schedule means a thicker wall and a higher allowable pressure, but it also reduces the internal flow area a bit, which can affect how much fluid can pass through. So choosing a schedule is about balancing strength (pressure capability) with flow requirements for a given application.

Temperature rating and outside diameter are separate considerations. Temperature rating relates to the material’s ability to handle heat, while outside diameter is tied to the nominal size of the pipe. The schedule specifically ties wall thickness to pressure rating, not these other factors.