Pump Selection Guide

• Fluid name and concentration
• Specific Gravity
• Viscosity
• Flammability

• Temperature
• Flow rate
• Head (suction, system and discharge)

• NPSH Available (NPSH_A)
• Description of application
• Experience (if any) with suitable materials of construction

FLUID CONCENTRATION

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

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 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).
• 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
  • Use our Friction Loss Calculator to calculate your total head loss.

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 (NPSH_A): the absolute pressure at the suction port of the pump.
  • NPSH Required (NPSH_R): The minimum pressure required at the suction port of the pump to prevent it from cavitating.
  • Use our Friction Loss Calculator to calculate your total head loss.

CAVITATION

• Caused when the NPSH_A is lower than the NPSH_R 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 vapour filled atmospheres: consider chemical duty motor
• Washdown areas: consider wash down duty motor
• High humidity: consider tropical duty motor