NPSH Margin Calculator — Vertical Inline Pump

Check whether your suction-side conditions give the vertical inline pump enough head to run without cavitation. BBP applies NPSHa ≥ 1.5 × NPSHr as the standard selection rule.

Source Pressure (PSIA, absolute)

Open atmospheric tank = 14.7; pressurized or vacuum systems enter actual

Static Head Hs (ft)

Positive if source is above pump; negative if below (suction lift)

Fluid Vapor Pressure (PSIA)

Water @ 60°F = 0.26; @ 140°F = 2.89; @ 190°F = 9.34

Suction Piping Friction Loss Hf (ft)

Sum of pipe, fittings, strainer, and isolation valve losses at design flow

Specific Gravity (SG)

Water = 1.00; brine 5% = 1.04; glycol 40% = 1.05

Pump NPSHr at Duty Point (ft)

From BBP-ISG/ISGD/ISWB curve at your flow rate; typical 6 – 14 ft

Your vertical inline selection should run without cavitation at the design duty point.
Send the full duty point for a firm pump selection

Options: (1) raise the source tank or shorten suction piping to add NPSHa; (2) switch to BBP-ISWB multistage to split head across stages and drop per-stage NPSHr; (3) specify a larger suction nozzle variant.
WhatsApp our chief engineer for a selection review

Do not specify a standard vertical inline pump at this duty point. Either redesign the suction-side (raise source, cool fluid, change piping), or switch to a horizontal end-suction or multistage configuration.
Request an NPSH redesign consultation

Formula: NPSHa (ft) = ((P_source − P_vapor) × 2.31 / SG) + H_s − H_f. Margin ratio = NPSHa ÷ NPSHr. BBP selection rule: ratio ≥ 1.5 (PASS), 1.2 – 1.5 (marginal — recommend multistage or tank re-elevation), < 1.2 (FAIL — redesign required).