How to Select Explosion Proof Pumps

Image Credit: Price Pump Company | Flygt, a Xylem brand | KSB AG

Explosion proof pumps are pumps specially designed to enclose parts of the pump that could be subject to internal damage or could cause explosion of the transfer media or surrounding atmosphere. They are used in applications which involve flammable media or combustible environments that require protection or isolation from ignition sources.

Operation

Explosion proof 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 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. 

Specifications

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

• Flowrate describes the rate of volume discharge through the pump, usually given in gallons per minute (gpm) or gallons per hour (gph) 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).
• 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.

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