Pumping Formulae
At Malcolm Thompson Pumps, we want to give our customers all the tools they need to properly select, operate and maintain their pumps, and that includes providing them with all the necessary Pumping Formulas.
Selecting the right pumps for your operations is key to achieving maximum efficiency and cost-effectiveness in your operations. There are various ways through which pump input power may be calculated. Below we’ve listed down a pump power formula for every given measurement.
To best ensure your pump choice meets your requirements, or for any questions regarding the formulas below, please do not hesitate to get in touch with one of our experienced customer service team members on 1800 439 607. Our friendly team will be happy to assist you with pump selection, specifications and getting a competitive quote.
Useful Terms
| Term | Notation | Unit |
| Kilowatt | kW | |
| Volumetric flow rate | Q | L/m or L/s or m³/h |
| Head | H | m |
| Velocity | v | m/s |
| Pressure | p | kPa |
| Density | ɛ | kg/m³ |
| Rotational speed | N | r/min |
| Specific gravity | S.G. | SG |
| Gravitational acceleration | g | m/s² (9.8m/s) |
| Electrical current | A | ampere |
| Temperature | °C | |
| Pump efficiency | Ƞ | Pump efficiency, decimal |
Pumping Formulae for any liquid
Volumetric flow from mass flow & density |
||
|---|---|---|
| For any liquid | ||
| Vol flow (l/s) | = | 1000 * Mass Flow (kg/s)
Density (kg/m3) |
Head of liquid from pressure & density |
||
| For any liquid | ||
| Head (m) | = | 1000 * Pressure (kPa)
Density (kg/m3) x g |
Pump input power from pump performance |
||
| For any liquid | ||
| Power (kW) | = | Density (kg/m3) * Volumetric Flow (L/s) * Head (m)
1000 * 102.0 * Efficiency (decimal) |
Pump input power from kilowatt – hour meter |
||
| Power (kW) | = | 36 * Disc.Revs. * Meter Ratio Constant * Motor Efficiency (dec)
Time (s) * Meter Disc. Constant (rev/kW-h) |
Pump input power from current and voltage |
||
| Power (kW) | = | Current (A) * Voltage (V) * Motor Efficiency (dec) * Pump Efficiency (dec)
57 735 |
Motor input energy per volume of liquid pumped |
||
| For any liquid | ||
| Energy/ Volume (kW-h/kl) | = | Density (kg/m3) * Head (m)
367 347 * Motor Efficiency (dec) * Pump Efficiency (dec) |
Pump input power from engine |
||
| Power (kW) | = | Pi * Torque (N.m) * Speed (rpm)
30 000 |
| = | Torque (N.m) * speed (rpm)
9 549 |
|
Pumping Formulae for water at 20°C
Volumetric flow from mass flow |
||
|---|---|---|
| Vol flow (L/s) | = | 1.002 * Mass Flow (kg/s) |
Head of liquid from pressure |
||
| Head (m) | = | 0.1022 * Pressue (kPa) |
| Head (ft) | = | 0.3354 * Pressure (kPa) |
Pump input power from pump performance |
||
| Power (kW) | = | volumetric flow (L/s) * Head (m)
102.2 * Efficiency (decimal) |
Motor input energy per volume of liquid pumped |
||
| energy/volume (kW-h/kl) | = | Head (m)
368.0 * Motor efficiency (dec) * pump efficiency (dec) |
Velocity of flow |
||
| Through a circular section | ||
| Velocity of flow (m/s) | = | 1273 * Volumetric Flow (L/s)
( Diameter (mm) )² |
Velocity head |
||
| Velocity head (m) | = | 1000 * Volumetric Flow (L/s)
Area (mm2) |
