Factors to consider when choosing the right pump for your application

Think pump selection is a complex exercise?

As the pump experts, we are here to make the process as pain-free as possible.

Having the following information at hand will make things easier.

Pump Selection
  • Fluid Name and Concentration
  • Specific Gravity
  • Viscosity
  • Flammability
  • Temperature
  • Flow Rate
  • Head ( Suction, System, and Discharge )
  • NPSH Available (NPSHA)
  • Description of Application
  • Experience ( if any ) with Suitable Materials of Construction

Pump Selection Factors

FLUID CONCENTRATION

  • Critical to deciding materials of construction for the pump
  • If the fluid is a trade name refer to MSDS (Material Safety Data Sheet)
  • Chemical resistance can vary with concentration and temperature

SPECIFIC GRAVITY

  • Specific Gravity is the weight of a given liquid compared to the weight of the equivalent volume of water.
  • By definition, water has a specific gravity of 1.0, but many chemicals have specific gravities greater than 1.0.
  • Many solvents and petroleum distillates have a specific gravity less than 1.0.

VISCOSITY

  • Viscosity is a measure of the resistance of a liquid to flowing.
  • It is needed to:
    • Calculate friction loss in the piping system
    • Correct the pump curve
  • Common units are cP ( centiPoise ) & cSt ( centiStoke ).

FLAMMABILITY

  • Extreme care must be taken when pumping flammable fluids
  • Pumps with stainless steel construction are highly recommended

FLOW RATE

  • Flow rate is the volume of liquid that needs to be pumped.
  • It can be expressed as metric units like m3/hr (cubic meters per hour) or lpm (liters per minute) or GPM (gallons per minute).
  • The flow rate is required to calculate friction loss in the users piping system.

TEMPERATURE

  • Maximum ambient temperature is based on motor maximum temperature.
  • Minimum ambient temperature is based on pump materials of construction.

HEAD

  • Also known as Total Dynamic Head (TDH), there are different types of head.
    • Suction Head: when the liquid supply to the pump is above the pump
    • System Head: pressure required to make the fluid flow through the piping system
    • Discharge Head: the maximum height reached by the pipe from the discharge port of the pump.

SUCTION LIFT

  • Suction lift happens when the liquid supply to the pump is below the pump.
  • Equal to the static height in feet or meters that the liquid supply is below the pump centerline, less suction line losses.

NET POSITIVE SUCTION HEAD

  • Net Positive Suction Head (NPSH) has two definitions:
    • NPSH Available (NPSHA): the absolute pressure at the suction port of the pump.
    • NPSH Required (NPSHR): The minimum pressure required at the suction port of the pump to prevent it from cavitating.

CAVITATION

  • Caused when the NPSHA is lower than the NPSHR required by the pump
  • Cavitation bubbles are formed in the low-pressure region and rapidly collapse when entering higher pressure regions in the pump, causing erosion damage
  • More likely with hot fluids, fluids with high vapor pressures, suction sources that are under reduced pressure (vacuum) or larger impellers operating near full flow

ALTITUDE

  • Higher Altitudes
    • Reduce lift capability
    • Reduce NPSHa
    • Affect motor by reducing cooling from the motor’s fan

ATMOSPHERE

  • Hazardous Atmospheres: need to follow strict guidelines for flammable fluids
  • Corrosive vapor filled atmospheres: consider chemical duty motor.
  • Washdown Areas: consider washdown duty motor
  • High Humidity: consider tropical duty motor