pump npsh tutorial

Pumps — NPSH (Teaching Mode)
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Step-by-step NPSH Understanding

Why NPSHa is an absolute head and stays positive even with suction lift.

Step 1 — NPSHr from pump curve (ABSOLUTE)

Enter NPSHr (ABSOLUTE, m) as read from the manufacturer chart

Step 2 — Altitude → Atmospheric effect

Altitude above sea level (m)

Step 3 — Temperature (hidden vapor-pressure effect)

Water temperature (°C)

Step 4 — Suction geometry & losses

Static suction level zs (m)
Positive = flooded (liquid surface above pump); Negative = lift.
Estimated suction losses hf (m)

Step 5 — Compute NPSHa & compare margin

NPSHa is expressed in meters of liquid head (absolute).

Step 6 — Smax (Raw) and optional factor

Smax Raw is the theoretical maximum suction lift at zero losses. Optionally apply a factor (e.g., 0.90) — leave blank if you don’t want to apply one.
Factor (optional, 0–1)

What students should take away

  • NPSHa is absolute head. Atmospheric pressure contributes a large positive head term.
  • Temperature matters, but only its effect is shown here (vapor pressure hidden).
  • Suction lift and losses subtract from available head.
  • Compare NPSHa to NPSHr from the pump chart to discuss margin.
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