What’s the Best Way to Stop a Spark?

As the old song says, it only takes a spark to get a fire going…and if that spark is in your dust collector, the resulting fire can do a lot of damage.

Your dust collector provides the perfect environment for a fire to start: plenty of fuel in the form of filter media and combustible particulates and continual airflow to feed a fire with oxygen. That’s why it’s critical to prevent sparks from entering the dust collector. While there are several options for spark control, they are not all equally effective. Let’s take a closer look.

How Many Sparks are Too Many?

Welding, plasma cutting, grinding and other applications can produce millions of sparks over the course of a shift. Dust collector manufacturers have developed different spark control systems in an attempt to prevent these sparks from making it through the ductwork and into the interior of the collector. These systems vary widely in effectiveness. For example, a demonstration of one spark control technology stopped all but 23 out of an estimated 3,000 sparks produced in the demo. But remember—it only takes ONE spark to start a fire!

When looked at this way, that ratio doesn’t sound very good. After all, we would never accept a medicine that kills 23 out of 3,000 patients, and we would not be happy if our bank misrecorded 23 out of every 3,000 transactions. Some tasks just don’t leave room for error. Spark control is one of those tasks.

Different Approaches to Dust Collector Spark Control

If you are engaging in spark-producing processes, it is essential to make sure that your dust collector is equipped with a spark control device. Some dust collectors come with these built in, while others will provide them as an option. Most of these will fall into one several categories.

• Spark Cooling:
  Spark cooling systems consist of an enlarged portion of ductwork divided by fixed-blade mixing vanes. This creates turbulence as air moves through this portion of the ductwork, which in turn disturbs the thermal bubble around the spark. While this is enough to cool down smaller sparks, larger sparks have too much thermal energy to be disrupted by such gentle turbulence. Many of these devices also have visible gaps between the mixing vanes, leaving a clear path for a spark to penetrate through unimpeded. Because many sparks still make it through the vanes, these systems rely on longer lengths of ductwork (sometimes with lots of bends and elbows) to allow sparks to continue to cool on their way to the collector. At best, this approach can be considered spark mitigation rather than true spark arrestance.
• Screens and Baffles:
  Screens and baffles use mechanical methods to strip the spark of its thermal envelope. These may consist of a mesh screen or a series of baffles that air moves through. As sparks hit against the wires in the mesh or the metal in the baffles, they lose their thermal bubble. These systems are very effective, but require regular maintenance to prevent buildup of dust in screen or baffles.
• Dropout Boxes:
  A dropout box is an enlarged enclosure designed to allow heavy particles to drop out of the air stream before air hits the filters. As dirty air and sparks come in, they enter the dropout box, where air velocity slows. The lower velocity allows sparks and larger particulates fall to the bottom of the dropout box. The velocity of the airstream is then increased again as it exists the dropout box. These systems take up a lot of room—the enclosure must be large in order for the airflow velocity to slow down sufficiently to allow the particulates to fall out of the air. In addition, they are not very efficient. They also require regular cleaning, and may themselves present a fire hazard if combustible dusts are allowed to accumulate in the bottom of the box.
• Copper Plates:
  These simple systems are just what they sound like: a copper plate placed as a physical barrier at the entrance of the ductwork. As sparks hit the plate, it absorbs thermal energy and extinguishes the spark. Copper is often used as a heat sink, so it may sound sensible to use it to cool down sparks. In reality, most sparks are traveling much too fast to have enough contact time with the copper to take advantage of its heat absorbing properties. These systems actually work more by brute mechanical means, much like screens and baffles. However, they will do nothing for the sparks that flow around the plate and directly into the ductwork.

RoboVent has spent years studying spark control technologies in order to understand how they work and the relative effectiveness of each approach. The result of our research is the RoboVent Delta3: a novel spark arrestance system that uses centrifugal force. In a series of tests, the new technology consistently outperformed all of the methods described above.

Don’t Mitigate – Eliminate!

In designing Delta3 Inline, we wanted to go beyond spark mitigation to eliminate as many sparks as possible. While no spark control device can claim 100% effectiveness across all situations, Delta3 Inline comes pretty close–in fact, in several rounds of scientific testing, Delta3 Inline allowed zero sparks through at all tested airflows. In addition, it demonstrated the lowest pressure drop of all tested centrifugal technologies. 

Delta3 Inline uses centrifugal force to extinguish sparks. Circular airflow patterns repeatedly drive sparks and embers against the outer wall of the device, extinguishing them before they reach the filter media.  Particles are then either collected in the trap for disposal or carried through the ductwork to the collection unit. Compared to mesh screen systems, Delta3 Inline stops sparks more reliably and requires less maintenance. 

If your processes generate sparks, don’t let ineffective spark control raise your risk of a dust collector fire. When sparks are eliminated, fires can be prevented.