Introduction to explosion proof pumps

When pumping substances that produce flammable vapors, such as high-proof alcohol,  sparks and high temperatures are an explosion hazard. While this isn’t a problem for brewers or wine-makers, distillers and hard beverage producers using high-proof ethanol must not only transfer highly flammable chemicals but also deal with potentially flammable vapors. Avoiding explosions in these contexts  is a matter of making sure the entire apparatus that provides power to your pump - from plug to switch/VFD to motor - is spark free.

What do we mean when we call a  pump explosion proof?

Explosion proof pumps are systems specially designed to enclose parts of the pump that could ignite vapors, resulting in explosion of the transfer media or surrounding atmosphere. As pump heads themselves aren’t usually explosion risks, the components that must be explosion proof are the motor, switch, and plug.

Do I need to worry about my motor?

Our explosion proof pumps use a CSA Standard Division 1 class 1 groups C, D & class 2 E, F, G motor. This standard is explained as such:

Division 1: In which ignitable concentrations of hazards exists under normal operation conditions and/or where hazard is caused by frequent maintenance or repair work or frequent equipment failure.

Class I: locations in which flammable vapors and gases may be present.

Class II: locations are those in which combustible dust may be found.

Group C: Ethylene, Cyclopropane, Ethyl Ether

Group D: Propane, Acetone, Ammonia, Bezene, Butane, Ethanol, Gasoline, Methanol, Natural Gas.

Group E: Comprising atmospheres containing metal dust including aluminum, magnesium, and their commercial alloys, and other metals of similarly hazardous characteristics.

Group F: Comprising atmospheres containing carbon black, coal or coke dust.

Group G: Comprising atmospheres containing flour, starch or grain dust, and other dusts of similarly hazardous characteristics.

Now, this doesn’t mean combustion won't happen. Instead, explosion proof motors are designed to control and contain combustion without rupturing or igniting surrounding vapors. It does this by controlling the pathways along which combustion occurs, allowing gasses to escape but assuring that they are cool enough not to be an explosion risk. It does this through narrow openings known as flame paths, which quench the flames and cool the expanding gasses.

Such motors also have limitations on how hot they can get. Class I, Division I motors must not develop a surface temperature hot enough to cause spontaneous ignition of gasses, which means no warmer than 230°C/446°F.

What about my VFD?

VFDs can cause additional heating of the motor through harmonic currents as well as being a spark risk. Essentially, the VFD distorts the sinusoidal voltage and current waveform of the input, producing higher frequency harmonics (RW), and increasing current draw without increasing torque, resulting in an increase to overall heat generation. The VFD can also increase heat when slowing the motor, as the lower speeds reduce air flow, reducing cooling. Because of this variability, the certification of a motor applies only when its run at a constant speed.  Inverter-duty motors with VFDs require approvals of their own. Due to this, explosion proof VFDs small enough for portable pumps are rare - perhaps even non-existent. As such, most of our explosion proof pumps are constant speed, using switches instead of VFDs.

However, our high-proof alcohol pump is variable speed!

What about my plugs?

Plugs can spark when connecting under load. So within a high-risk environments (especially when working with substances like gasoline) explosion proof plugs and sockets, such as those by meltronics, are used. These are large fiberglass plugs that keep fluids or gasses away from any closed circuit electricity.

Explosion proof plugs come standard on most of our explosion proof lines.

A pump is only classified as explosion proof if each component within your pumping apparatus is free of risk, including motors, VFDs/switches, and plugs. Ignoring even one component in this line can have catastrophic effects.