Process Pump Calculation - For Junior Engineer

Case Study : Estimate the pump size required to deliver of 8.22 dm³/s (rated capacity) diesel from storage tank, T5/6-1902 to diesel day tank, T5-1901. Total suction pipework pressure loss from pressure drop simulation is 0.044 bar and discharge losses is 6.214 bar. Assume pump efficiency at 60%.

Process input data ;

Liquid = Diesel

Pumping Temp, = 22 ⁰C (Amb)

Flowrate = 8.22 dm³/s

Pumping Density = 836 kg/m³

Kinematic viscosity = 4.4 cSt

Vapour Pressur at

Pumping Temperature = 1.07 X 10E-3 bar (Abs)

Absolute pressure in

Suction tank = 1.016 bar

Suction elevation to

Centre of pump = 0 m

Absolute pressure in

Discharge tank = 1.016 bar

Discharge elevation to

Centre of pump = 4.5 m

1 bar = 10200/Density (kg/m³) = ____m

Pump Sizing Calculation;

A. Total minimu suction head

1. Suction tank pressure è 1.016 bar (abs) 12.39 m liq.

2. Elevation + 0 bar + 0 m liq.

3. Total Pressure loss in pipework - 0.044 bar - 0.538 m liq

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0.972 bar (abs) 11.85 m liq.

B. Total minimum discharge head

1. Discharge tank pressure è 1.016 bar (abs) 12.39 m liq.

2. Elevation + 0.369 bar + 4.5 m liq.

3. Total Pressure loss in pipework + 6.214 bar + 75.75 m liq

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7.6 bar (abs) 92.66 m liq.

C. Differential head

1. Total maximum discharge head 7.6 bar (abs) 92.66 m liq.

2. Total minimum suction head - 0.972 bar (abs) - 11.85 m liq.

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6.627 bar (abs) 80.81 m liq.

NPSH_A = Abs. Pressure in suction tank – Vapour pressure (abs) ! Elevation – line loss

= 1.016 bar – 1.07 X10E-3 bar + 0 – 0.044 bar

= 0.971 bar

= 11.84 m liq.

Hydraulic power calculation,

Hyd kW = (Rated capacity (m³/hr) x Diff.head x Relative density)/367

= ( (8.22 x3600/1000)x 80.81mx0.836)/367

= 5.45 kW

At 60% pump efficiency, Actual power required;

bkW = 5.45 kW/0.6

= 9.1 bkW