Using overhead powerline proximity warning device for heavy equipment is a work practice that can warn and immobilize heavy equipment when it reaches a certain height or unsafe distance from overhead power lines. This can reduce safety risks that might occur if the operator or spotter is distracted and the equipment is tracking into live lines.

Construction workers suffer from electrocution more than any other industries, primarily due to workers and materials accidentally contacting power lines.  Warning devices are designed to be installed on any mobile construction equipment – e.g., cranes, trucks, etc. – at risk of coming in contact with high-voltage power lines. These devices have sensors that detect the presence of live current close by and use audio and/or visual warning signals to alert the operator before getting dangerously close to the live lines.

A proposed solution for these risks is to use proximity warning devices to alert operators when they approach too close to live lines. These warning devices include an electric field sensor, which is mounted on the heavy equipment. The sensor is designed to sense the electric fields around the overhead power line and to warn when the operator when the equipment passes the preset safe distance from the power line. Further, these detection devices are flexible and can also be placed anywhere safety is concern such as the load itself and on boom arms or any other heavy equipment extension.

Although these devices are reported to be effective in many applications, the manufacturers caution against over-reliance on them, encouraging users to consider supplementary and comprehensive safety strategies (www.osha.gov). Moreover, insulating links must be attached to the crane’s hook and/or boom to prevent the flow of electricity if the equipment accidentally makes contact with energized power lines.

In addition, some of these warning devices are used to accurately monitor the equipment’s vertical movement.

Even making contact with less dangerous utilities can cause various risks and damages, which could result in huge costs and reduced productivity. Using warning devices on mobile construction equipment – e.g., trucks, cranes, booms, etc. – can increase productivity by minimizing the risk of accidental contact with overhead powerlines during construction activities.

Other prevention techniques include de-energizing power lines in order to work nearby, using spotters to warn operators of imminent contact, and providing barriers to impede physical contact with live lines [29 CFR 1910.333(c)(3) and 29 CFR 1926.550(a)(15)]. However, these techniques require more field personnel and the expenses associated.

In most cases, the minimum distance will be dictated by occupational safety regulations. For example, the OSHA standards require a clearance of at least 10 ft (3.0 m) for powerlines at voltages up to 50 kV (29 CFR 1926.550). The warning devices should not alarm outside the desired minimum clearance distance since these false alarms may cause the operator to question the effectiveness of the sensor and thereby ignore it completely.  The study that has been conducted by Centers for Disease Control and Prevention (CDC) in 2008 on the performance of warning devices suggested to test the performance of warning devices, before initiating crane operation, using small changes in boom length (less than ± 5 ft (1.5 m) and boom elevation angle (less than ± 8°).

It must be noted that warning devices cannot completely prevent accidents. However, if they are properly installed, they would decrease the risk of accidents. The operator needs to set up the minimum distance and check the performance of sensors before operating the heavy equipment on the jobsite.

Sogand Hasanzadeh - University of Nebraska- Lincoln
Behzad Esmaeili, Ph.D. - University of Nebraska- Lincoln