How to Select DC Powered Pumps

Image Credit: Gorman-Rupp Industries | Xylem Flow Control | Johnson Pump, An SPX Brand

DC powered pumps use direct current from motor, battery, or solar power to move fluid in a variety of ways. Motorized pumps typically operate on 6, 12, 24, or 32 volts of DC power. Solar-powered DC pumps use photovoltaic (PV) panels with solar cells that produce direct current when exposed to sunlight.

DC vs. AC

The main advantage of DC (direct current) pumps over AC (alternating current) pumps is that they can operate directly from a battery, making them more convenient and portable. They are easier to operate and control, since AC systems typically require a controller to manage speed. DC pumps also tend to be more efficient. However, AC pumps usually are designed for higher speeds and larger bursts of power. They also have a longer working lifespan than DC pumps.

For information on DC motors, visit the How to Select DC Motors page on GlobalSpec.

Operation

DC pumps can be designed to operate based on a dynamic or positive displacement principle. Dynamic pumps, and their subtype centrifugal pumps, utilize fluid momentum and velocity to generate pump pressure while positive displacement pumps use expanding and contracting cavities to move fluids. Dynamic pumps produce a variable flow suited for generating high flow rates with low viscosity fluids, while positive displacement pumps produce a constant flow suited for producing high pressures (and low flow rates) with high viscosity fluids. 

Pump Types

Selecting a suitable DC powered pump requires an analysis of different pump types.

Dynamic Pumps

Among dynamic pumps, types include centrifugal and special effect pumps.

• Centrifugal pumps are typically characterized by high flow rates and low to medium head. They are best at handling low viscosity fluids. Subtypes of centrifugal pumps are axial, mixed, and radial flow pumps.
  • Axial flow pumps provide the highest flow rates and lowest head of centrifugal pumps
  • Mixed flow pumps are designed to incorporate characteristics of axial and radial flow, providing medium flow rates and head.
  • Radial flow pumps provide the highest flow head and lowest flow rates of centrifugal pumps
• Special effect pumps include specially propelled or powered pumps such as hydraulic, gas lift, and electromagnetic pumps. They provide specific advantages for specialized applications. For example, electromagnetic pumps do not have a mechanical seal, making the pump leak free and low-maintenance which is important for toxic or corrosive media.

Positive Displacement Pumps

Among positive displacement pumps, types include rotary and reciprocating pumps.

• Rotary pumps are typically characterized by medium flow rates and low to medium head. They provide a smooth flow and are best suited for clean, non-abrasive, viscous fluids. Subtypes of rotary pumps include screw, peristaltic, gear, and rotary vane pumps.
  • Gear pumps contain few moving parts and are the ideal choice for clean oils and other clean, high viscosity fluids.
  Peristaltic pumps require no seal and have no leakage, making them a good choice for handling disinfectants, corrosives, and media containing solids.
  • Rotary vane pumps are able to handle thick and thin liquids well, making them ideal for applications handling multiple clean fluids of varying viscosities.
  • Screw pumps provide the highest flow rates of positive displacement pumps. They can handle oils, fuels, and other high viscosity liquids.
• Reciprocating pumps are typically characterized by low flow rates and high head. They provide a pulsed flow able to handle dirty, tacky, and viscous liquids. Subtypes include diaphragm, piston, and plunger pumps.
  • Diaphragm pumps are seal-less pumps which can run dry and can handle a wide range of liquids, including fluids containing solids and corrosives.
  • Piston pumps can provide very high pressure and are best suited for high head applications involving abrasive liquids.
  • Plunger pumps provide the best means to achieve very high pressures. They are best suited for water and other thin liquids.

For more information on the operating and performance characteristics of these pump types, visit the Industrial Liquid Handling Pumps page on GlobalSpec.

Specifications

The primary specifications to consider when selecting DC pumps are flowrate, pump head, pressure, horsepower, power rating, outlet diameter, and operating temperature.

• Flowrate describes the rate of volume discharge through the pump, given in gallons per minute (gpm) or gallons per day (gpd) for low-flow metering applications.
• Head defines the energy supplied to liquid (per unit weight) by the pump. It is expressed as a column height of liquid (either vertical lift or suction), given in feet of head (ft).
• Pressure describes the operational pressure of the pump. It is usually given in pounds per square inch (psi) or bar.
• Horsepower indicates the output power of the pump, measured in units of horsepower (hp).
• Power rating indicates the power required to operate the pump, measured in Watts (W) or horsepower (hp). For DC pumps, some manufacturers will instead specify the required voltage (in volts or V) and current (in amps or A). The power rating is the product of the voltage and current ratings (power = voltage x current).
• Outlet diameter is the size of the discharge or outlet connection of the pump. Inner diameter (I.D.) describes the size of the inner opening while outer diameter (O.D.) specifies the entire opening size including the pipe thickness.
• Operating temperature defines the range of temperatures or temperature limit of the media handled by the pump.

For a more in depth understanding of pump specifications, performance curves, and operation, visit the Industrial Liquid Handling Pumps information page on GlobalSpec.

Features

DC powered pumps vary based on a number of features.

Pumps with adjustable speed can operate at speeds selected by an operator while continuous duty pumps maintain performance specifications at 100% duty cycle. Pumps featured to run dry pumps can operate without pumped fluid or external lubrication for an extended period of time without damage to the pump. Some DC powered pumps are corrosion-resistant, explosion-proof, or meet strict guidelines established for sanitary process applications. Others are configured to include an integral grinding mechanism or have centerline suction or discharge.

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