By Craig Ries, product safety engineer, Terex Utilities
As we enter the full grip of winter, setting up aerial devices and digger derricks in snowy or icy conditions brings additional concerns for equipment operators. Normal traction is greatly reduced, which could put the truck into an unstable position.
Variable site locations—on gravel or grass, sloped or level—and the urgency to minimize electrical disruptions, means utility crews must often make the most of imperfect conditions and adjust accordingly to accomplish the work safely.
Upon arrival at the site, whenever possible, clear away snow and ice under outriggers and tires so that they are in contact with bare ground and avoid setting outriggers on drains or manholes.
All outriggers must be lowered to provide proper support, apply downward pressure on outriggers, and always use outrigger pads on a level surface.
Traction aids under tires and outriggers, such as sand or gravel, can also be used help to prevent tires or outrigger pads from sliding in slick conditions.
“When working on frozen ground, adding a layer of rubber or neoprene under the outrigger pad will help increase friction and create better contact between the pad and the ground. Frozen ground acts like concrete or a paved surface. Adding a neoprene layer allows the pad to deflect slightly which encourages better ground contact resulting in lower ground bearing pressures,” says Kris Koberg, CEO of DICA, manufacturer of engineered outrigger pads.
Koberg continued, “Generally, we have found that ¾ in. thick neoprene sheets increase friction, and improve load distribution in these hard ground situations.”
Jim Olson, senior product engineer, Terex Utilities added, “Keep in mind that snow and ice can build up on the truck during transportation and accumulate during operation. Brush off the snow dust from the contact surfaces, including the bottoms of outrigger feet as well as both top and bottom surfaces of the outrigger pads.”
Finding a Location
Next, choose a location that provides the best stability for the work to be done.
“Position the truck as far onto the street or road as possible, so that if your truck does move during operation, the tires and outriggers will not slide down a slope into a ditch, manhole, or other hazard,” said Olson.
Caution is required even on pavement because “gravel on concrete can act like ball bearings under outriggers and outrigger pads,” he explains.
Always refer to the manufacturer’s operator’s manual for information on proper setup and use of outriggers.
Operating within level tolerances is extremely important. If a slope is unavoidable, the bank of the slope may need to be cut away or cribbing should be used to level the truck.
When operating the unit on a slope there is always a potential for the truck to move, even when working on dry pavement. This is due to gravity wanting to “pull” the truck down the slope.
When operating on a sloped surface that is ice or snow covered, this effect is amplified, making it more likely that the truck will slide down the slope unless the proper precautions are taken during setup.
Leveling the truck will better distribute the load between the uphill and downhill outriggers and tires, helping to reduce the risk of sliding on the sloped surface.
One option for leveling aerial devices or digger derricks is engineered cribbing blocks from DICA.
“ProStack Slot Lock and Pyramid Lock Cribbing Blocks interlock and allow operators to achieve the height needed to level the equipment and reduce risk when stacking loose materials,” said Koberg.
Once in position, chock the wheels to prevent movement downhill, and evaluate the chock location to make sure the truck won’t pivot around one chock.
For example, if a truck is parked with the cab pointing slightly downhill, it should be chocked on the front and backside of the tires. If it were chocked only on the front side of the back tires, and the boom abruptly stopped, it could sway, causing the truck to pivot. This may even be evident on flat ground if there is not sufficient traction.
Setting up Correctly
Proper setup requires that outriggers do not slide on the outrigger pads during use, and the outrigger pads do not slide on the ground. “This is a concern that comes up every winter,” says Koberg. “Over the years, we have worked with users to develop a variety of solutions to address different sliding issues, as there is no one-size-fits-all answer,” he says.
In one situation, DICA worked with an electric cooperative to create a base of expanded metal in a frame.
The metal frame was larger than the outrigger pad and was positioned under it to help to cut through snow and ice, giving the pads something to grip to.
Three off-the shelf products that work in different scenarios are the company’s cleated pads, with serrated cleat grips for improved traction, DICA’s standard Cavity Pad with raised sidewalls, or their newest Cavity Pad Plus, with an inverted beveled footbrake that prevents the outrigger foot from escaping.
Once proper setup is achieved, and operation begins, it’s good practice to reduce sudden boom movements.
“Operate the truck by feathering the controls so that all initial and final boom movements are performed at the lowest practical speed,” says Olson.
Removal of the snow and ice, leveling the truck, the use of outrigger pads and traction aids, and slow steady boom movements are some of the techniques and tools at the operator’s disposal to reduce the risk of the truck sliding down the slope in snowy or icy conditions.
If a unit begins to slide during operation, the operator should stop the boom functions. “Attempting any other operations when the machine is sliding out of control may compound the issue,” says Olson.
Recovery during operation is extremely difficult, that’s why it is so very important to prevent loss of traction before it happens.
Finally, if the roads and work site are not sufficiently clear to enable proper setup, postpone the work until later or clear the area.