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NiCuZn · Black Owl — Engineering calculation sheet

Pump power and head.

Estimate differential head, hydraulic and shaft power, a standard motor size and NPSH available for a centrifugal pump.

Duty
m³/h
kg/m³
bar(g)
bar(g)

Destination pressure plus static height, line, equipment and control valve losses.

%
%
Suction (NPSH available)
bar(a)
m

Negative if the liquid is below the pump.

m
bar(a)

Results

Shaft power3.7 kW
Standard motor5.5 kW
Differential pressure4 bar
Differential head40.8 m
Hydraulic power2.22 kW
Motor power needed (with allowance)4.26 kW
NPSH available11.5 m

Preliminary estimate for early engineering. Check against your design basis, standards and vendor data.

Method

How it is calculated

H = ΔP / (ρ g)  ·  Phyd = Q ΔP  ·  Pshaft = Phyd / η

The motor is the next standard IEC rating above the shaft power plus the motor allowance. NPSH available is the pressure at the source liquid surface above the vapour pressure, expressed as head, plus the static head, minus suction line losses:

NPSHa = (Psource − Pvap) / (ρ g) + z − hf

It must exceed the pump’s NPSH required, from the vendor curve, with a margin. Efficiency for an early estimate is an assumption: small centrifugal pumps are often 50–70 % efficient.

Read: equipment sizing basics →All engineering tools →Size equipment from your own balance in Black Owl ↗

Calculated with the free engineering tools at nicuzn.com/tools. Preliminary estimate for early engineering; check against your design basis, applicable standards and vendor data before use.