Pump 101

The Key to Picking the Perfect Pump for the Job

With the right information, our sales representatives can quote a pump to more precisely fit your needs.  

Just let us know the following:

  • Fluid name, concentration, specific gravity, viscosity, solids data, temperature, flammability
  • Total dynamic head (TDH) and flow required
  • NPSHa (Net Positive Suction Head available)
  • Description of application
  • Customer experience with suitable materials of construction

and we'll suggest the best pump model for you.

 

Please hover over the tiles below for a brief Pump 101 tutorial and those factors that influence pump selection.

Fluid Name & 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

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). 

Flammable Fluids

  • Extreme care must be taken when applying a pump for flammable fluids

  • Use only pumps with stainless steel construction, DB Series with PVDF construction or UC Series
  • Use only explosion proof motors
  • Use with bronze bump ring centrifugal pump option where available
  • Make sure all components are grounded & bonded
 
Flow
  • Flow rate is the volume of liquid that needs to be pumped

  • It can be expressed as GPM (gallons per minute) or metric units like m3/hr (cubic meters per hour) or lpm (liters per minute)

  • Flow rate is required to calculate friction loss in the users piping system

Head

  • Frequently called TDH (Total Dynamic Head)

  • It is the discharge head minus the suction head or plus the suction lift. 

  • Based on the piping system

  • Along with flow rate, needed to choose a pump from published curves

  • Expressed as feet or meters

Suction Head

  • Suction head exists when the liquid supply to the pump is ABOVE the pump

  • Equal to the static height in feet or meters that the liquid supply level is above the pump centerline less suction line losses

  • Commonly referred to as a “flooded suction” application

Suction Lift

  • Suction lift exists 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

  • Generally, this type of application requires a self-priming pump like our SP Series

Discharge Head

  • Discharge head is comprised of:

    • Static discharge head

    • Frictional loss in pipe and fittings in discharge piping

    • Pressure in discharge container (if any)

    • Any loss at sudden enlargements

    • Exit loss

System Head
  • System curve is a plot of the head required to make liquid flow through piping system
  • A centrifugal pump always operates at intersection of head-capacity curve and system curve

  • System curve consists of:

    • Static head
    • Pressure head
    • Friction loss in pipe & fitting
Net Positive Suction Head (NPSH)

  • Net Positive Suction Head (NPSH) is the suction head required by the pump and provided by the piping system to avoid cavitation

  • Called ‘net’ because the vapor pressure is always subtracted out, therefore it is over and above or ‘net of’ the vapor pressure

  • Called ‘positive’ because the units are always in absolute pressure terms – either feet-absolute or meters-absolute

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
Temperature

  • Maximum ambient temperature: usually based on motor maximum temperature

  • Minimum ambient temperature: usually based on pump materials of construction

Altitude

  • Higher altitudes: 

    • Reduce lift capability

    • Reduce NPSHa

    • Affect motor by reducing cooling from the motor’s fan
Atmosphere
 

  • Hazardous atmospheres:  follow guidelines for pumping flammables

  • Corrosive vapor filled atmospheres:  consider chemical duty motor

  • Washdown areas:  consider wash down duty motor

  • High humidity:  consider tropical duty motor