Bonding mats can be used to help prevent electric shocks when working near charged utility lines.
Badger Daylighting crews know the dangers of working near utility lines firsthand, and thankfully they use bonding mats.
“We’ve had tires that were damaged because they took current and the employees were safe because they were on the mat,” says Dave LaFleur, corporate HSE director for Badger Daylighting, a North American provider of hydroexcavation services. “When hooked up properly, the employees are safe from voltage.”
Bonding, or grounding, mats provide an insulated electrical safety mat that, when laid on the ground, protects workers. The National Institute for Occupational Safety and Health in Washington, D.C., also says the nonconductive safety mats prevent individuals from being a path for electrical current to the ground.
“Bonding mats create an equipotential or equal potential area to protect the operator in the event that water cuts through an energized power cable,” says Dean Krossa, president of Kri-Tech Products Ltd., a manufacturer of bonding mats. “If the water stream cuts through energized cable, the wand would become energized.”
HOW THE MATS WORK
Bonding mats helped prevent underground land strike injuries and deaths according to the results of a six-month review of hydroexcavation electrical occurrences by Kri-Tech Products. Incidents involving gas line or power pole digs without the use of bonding mats resulted in hospitalization or death, the 2012 review found.
Krossa calls bonding mats an effective way to reduce exposure to electrical burns and fatal electrocution. Workers who excavate near underground cables or waterlines do risk electrocution, he says.
Bonding mats come in standard configurations, usually 58 inches square. There are common mats at 120 inches and custom configurations are also available. “Mats are bonded to the lance and dig tubes, keeping the operator at equal potential and safe,” says Wes Scott, director of consulting for the National Safety Council.
CARING FOR THE MATS
Mats should be pressure-washed, dried and rolled for storage, states Kri-Tech’s care and maintenance guide. It also states the ferrules and clamps should be wire-brushed before and after use “to keep connections clean and corrosion free.”
Rolled-up mats may put stress on wire grid if folded repeatedly in the same pattern.
The mats, and all associated conductive material, should be visually inspected before each use for damage, adds the guide, which calls “normal signs of wear acceptable,” but “punctured, severed or missing braid elements unacceptable.” Those that don’t pass muster should be “tagged out and removed from service immediately.”
The guide adds that bonding mats should undergo digital low-resistance ohmmeter testing every three months, or at prescribed intervals based on frequency of use. Those with measured resistance values outside acceptable ranges should be tagged out and removed from service.
GOING BEYOND THE MATS
To protect themselves, Scott suggests hydroexcavation workers check out NSC’s best practices.
He says cables should be de-energized if possible, and breakers should be hot-line tagged so they trip faster at lower fault currents. Scott also says operators need to have a heightened operator awareness, skill, and training and knowledge of the limits on water pressure and temperature. Another suggestion from Scott is protective urethane covers on the water lance and dig tubes.
Personal protective equipment, such as omega-rated boots and footwear, can protect workers. “Footwear outsole can provide a secondary source of electrical hazard protection,” Krossa says.
LaFleur advises workers “to follow company job procedures as they relate to grounding and bonding” to protect themselves from hydroelectrical shock or electrocution. He points out that “digging at appropriate water pressure eliminates damage to underground infrastructure.”