PIPE DIMENSIONS · TECHNICAL ANSWER

What is the difference between NB/NPS and pipe outside diameter?

NB or NPS is a nominal pipe-size designation, not the measured outside diameter for most pipe sizes. The actual OD is fixed by the dimensional standard, while the wall thickness changes with schedule.

DETAILED EXPLANATION

For a given NPS, different schedules generally share the same OD but have different inside diameters and weights.

Tube is often ordered directly by actual OD and wall thickness rather than pipe schedule.

Key points

  • NB/NPS: nominal size
  • OD: actual outside diameter
  • Schedule changes wall and ID
  • Use dimensional tables for calculations
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