Pipe Line DZ
NPS – Nominal Pipe Size
An American standard (in inches, without unit symbols) used to define pipe size.
For example: NPS 2 has an outside diameter (OD) of 2.375 inches
For NPS 14, the OD is exactly 14 inches
The inside diameter varies depending on the wall thickness, specified by the Schedule (SCH)
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SCH – Schedule (Wall Thickness)
Defines the pipe wall thickness numerically:
📐 Schedules: 5, 10, 20, 40, 80, 160, XS, XXS
🧮 Formula: Schedule ≈ 1000 × (P / S)
P = Design Pressure (psi)
S = Allowable Stress (psi)
📚 Standard References:
ASME B36.10M (2024) for carbon/alloy steel pipes
ASME B36.19M (2024) for stainless steel pipes (symbolized as “S” in SCH numbers like 10S, 40S)
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DN – Diameter Nominal
A metric-based international pipe size standard by ISO (in mm, without “mm” symbol).
Equivalent to NPS as per ISO 1127:2024
🧾 Examples:
DN 15 = NPS ½
DN 50 = NPS 2
DN 300 = NPS 12
🧱 Wall Thickness Series:
Series 1, Series 2, Series 3
Used primarily for classifying stainless steel pipes (B36.19M)
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📊 Pipe Size Equivalents Table:
NPS DN OD (inches) Schedule
½ 15 0.840 SCH 80
2 50 2.375 SCH 40
14 350 14.000 SCH 60
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📎 References:
ASME B36.10M:2024
ASME B36.19M:2024
ISO 1127:2024
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