According to the Bureau of Labor Statistics (2003–2010), the leading cause of workplace death for crane operators is electrocution. This is the same in every industry, and it affects not only crane operators, but also employees working in close proximity to the crane itself. Oftentimes, electrocution occurs when a boom or tower crane makes contact with electric lines. However, sometimes these accidents occur due to the most common electrical violation of all: improper grounding.
Many employers are unaware of the electrical and wiring requirements documented by OSHA, and as a result, workers suffer. Electrical methods are the sixth most common violation documented by OSHA, and the most common of those six violations is grounding.
All cranes must comply with OSHA 1910.304(a)(1)(i), which requires that all equipment use and identify grounded and grounding conductors. In other words, a 3-phase electrical conductor is not sufficient to meet the electrical requirements for overhead cranes outlined by OSHA. With respect to electrically operated overhead cranes and hoists, OSHA requires the equipment to have a fourth ground bar on any overhead crane system in use.
Many facilities have been using the same overhead cranes for so long that they don’t consider the conductor bar(s) that motorize their system. For many years, overhead crane electricity consisted of three wires: one for positive (high) connections, one for negative (low) connections, and one for neutral connections. However, OSHA now requires a fourth connection to the ground.
Not only does OSHA require electrical conductors to consist of four wires, they also require color-coding. The first three wires in the conductor (positive, negative, and neutral) can be any color, generally the same color, such as orange. But, the ground connector must be a different color—preferably green—to offset the other wires in the conductor. Ensuring that your ground connector is color-coded makes it really easy to identify electrical conductors that are up to code and operating safely.
So, which types of cranes need to be grounded anyway?
Basically, if a hoist is supported by an overhead structure such as a bridge crane, jib crane, monorail, or gantry crane, it is a crane. It doesn’t matter if the crane is permanently installed or completely portable—if it uses electricity for motorization, it needs a separate conductor for the ground. Today, many cranes are equipped with extra electronics: remote controls, variable frequency, electronic monitoring devices, etc. This type of equipment also needs to be grounded—not only for your protection, but also for the protection of the equipment.
Electrical current follows the path of least resistance, so if a short to ground exists, the last thing you want is for your crane operator to become the ground. Operators are electrocuted everyday; just one touch and the electrical circuit is complete.
It may cost extra money to ensure that your overhead cranes are up-to-date with a separate ground conductor, but the cost is well worth the peace of mind and the safety of workers who have to operate and/or work around the cranes in your facility.