Overlooked Forklift Safety Issues - Static Electricity

Most of us wouldn't point to static electricity as a major safety concern - if you think about it at all. If and when we think about it, it's as a mild annoyance when we feel the shock that happens as we drag our feet across the floor in the morning and get zapped as we open the bathroom door. Since these small static discharges are rarely painful and relatively infrequent, we pay them scant attention and continue on without giving it a second thought. However, for some indoor forklift applications, the build-up and discharge of static electric is a serious safety concern. Unlike small static shocks built up by your socks, an indoor forklift can build up to 50,000 volts of static electric before it is discharged, which is more than enough to pose a serious safety hazard for anyone in close proximity to the unit.

Building up a charge

Fortunately, not all forklifts pose an inherent risk as far as static electricity is concerned. While all forklifts generate static electricity, the capacity to produce and store it varies from one forklift to the next, and it's all because of the tires. You see, static electricity is generated whenever two dissimilar materials come into close, repeated contact with one another. Insulating materials, such as the rubber in a forklift tire, for example, are far more susceptible to storing a static charge. As an insulator, the rubber does not conduct electricity very well, which prevent it from discharging the built up static unless it comes into contact with a more conductive material.

The buildup of this electrical potential can lead to electrostatic discharge when contact with a conductive material completes an electrical circuit allowing the static electricity to flow and become an electrical current. The consequences of an electrical discharge can range from discomfort to disaster like something as mild as the jolt we experience by touching a doorknob after walking across a rug in dry weather to something as catastrophic as an igniting an explosion or being electrocuted.

Marking vs non-marking tires

For forklifts employing black (aka marking) tires, building up dangerous levels of static electricity isn't as much of an issue as the carbon black within the tires is a conductive material that continuously discharges the electricity as it's built up. Unfortunately, not all forklifts can use black tires. Certain indoor applications, such as those in the warehousing, pharmaceutical or food and beverage industries, must use what are known as non-marking white tires. In these applications, black tires are not practical as they leave tire marks across the floor and generate a fine particulate of black carbon that can damage or taint consumable products such as food, beverages or pharmaceuticals. Instead, these applications prefer to use what are known as non-marking tires.

To remove the issues caused by carbon black, manufacturers utilize a different binder in the manufacturing process to create what are known as non-marking white tires. Non-marking forklift tires are manufactured from a combination of synthetic rubber and white silica (chalk) gel or resin. As their name suggests, these tires do not leave black marks and/or residue due to rapid starts, stops or turns by replacing black carbon with silica. Instead, these tires deposit a chalk-like dust as they wear, which is preferred as it does not stick to the floors making it easier to clean up.

For more information on the differences between marking and non-marking tires, click here

The problem with non-marking tires

By replacing black carbon in the manufacturing process non-marking tires offer a simple yet effective solution to the issues caused by traditional forklift tires. As we pointed out above, however, substituting silica for black carbon also removes its conductive properties – the main reason black marking tires don't accumulate high levels of static electricity. In fact, silica has the opposite effect as it server as an insulator, allowing far more static to accumulate instead of dissipating as it builds up. Without a means of discharge, the static electricity builds up to the point where it becomes a potentially serious safety hazard with enough charge to start a fire, damage electrical components and devices or injure someone that makes contact with the unit while touching the ground. That a forklift can amass enough static electricity to cause bodily harm to someone is the reason why some operators have adopted unique habits to deal with the potential risk. For example, when they get off their forklift at the end of a shift, some operators leap from their seats or take other steps to ensure they do not touch the ground and the forklift at the same time to avoid a severe shock from the built-up electricity.

Beyond direct injury to operators via electric shock, the other main safety hazard associated with static electricity is the potential for explosions and fire. Take a moment to consider the combustible materials in some of these applications, beginning with some of the trucks themselves. With electric forklifts, there's the potential for highly combustible hydrogen gas to escape while a battery charges while LPG forklifts are susceptible to fuel leaks. At the same time, the facility itself may provide more potentially explosive materials such as fine dust and particulate.

How to Ground a Forklift

To avoid the potential safety hazards associated with static electricity, there are a few effective solutions available on the market. Perhaps the most popular is what's known as an anti-static strap or chain. Here, a conductive strap, cord or chain is hung from the undercarriage of the forklift to ground the unit and prevent the accumulation of static charge. To be effective, we recommend that you do the following:

  • Have two anti-static devices installed on every unit, with one behind each axle, as this will serve as an inexpensive insurance policy in case the first one falls off;
  • Conduct regular inspections of the anti-static strap or chain – remember, it's only effective if it's touching the ground;
  • Frequently clean your chain or strap to remove any buildup of dust or debris as an accumulation such as this reduce its ability to ground the unit.

In Closing

So, what did we learn? The rubber in a forklift tire allows it to generate static electricity, which, without the assistance of a conductive material, can accumulate to dangerous levels. This is presents a significant safety hazard for indoor forklifts that utilize non-marking tires as they lack the conductive black carbon used in traditional forklift tires, meaning they're quite efficient at accumulating a static charge. To solve this issue, we recommended installing not one but two anti-static strips and ensuring they are properly maintained at all times. If you have questions about where to get an anti-static strip, need one installed, or have other forklift service, visit our forklift repair services page or contact us today!

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