Lift assist ‘shortens’ long ladders

Climbing 80 m to go to work may be routine for maintenance crews but three times in a day is a lot of climbing. By one account, only about 25% of turbine towers have service lifts. That leaves long ladders in the rest of them. Lugging up 20 lbs or more of equipment makes a climb more demanding. What’s worse, say maintenance people, is lugging it down. “Technicians frequently accelerate and stop their weight with each step on the way down so the ergonomics involves more shock to the ankles and knees,” says Greg Crew, Global Wind Product Manager for safety equipment manufacturer SafeWorks LLC, Seattle. Despite the relative good pay, many stay on the job only three to four years.

The solution may be in a service lift or climb assist. When a tower is too small or simply not designed to accomodate a service lift, a climb-assist may be useful because it can be retrofit to ladders. Early climb-assist devices were simple counter weights on ropes that pulled workers up. But if the work in a nacelle needed two technicians, the counter weight had to be winched back up for the second person.

More recent designs are motor driven continuous lines that loop from deck to deck. A worker would don a standard climbing, front D-ring harness, hook onto the lift line, and signal the motor to start. This was done by pulling on the rope in the direction of the required motion, and then resisting the motor’s pull to stop. When the motor did start, which might take a second or two, the lift was often too fast or too slow. The motor ran at its own speed and torque, so climbers accommodated motors and not the other way around.

Some turbines have a straight run ladder from bottom to top, but an 80-m tower has about three sections about 25 m each. When climbing to the top, a technician may have to pass through multiple safety hatches at each deck. Going through a hatch requires a climber to stop, open the hatch, start through the hatch, stop to close the hatch door, and continue climbing. The two or three-second delay introduced a hassle factor. Although better than no assist at all, the early designs were awkward to use and not quite right.

Power Climber Wind, a division of SafeWorks, believes its recent IBEX 1000 climb assist solves the problems users experience with other systems. “The device puts the control over the climbing effort in the hands of the climber,” add Crew. “The climber selects a load which ranges from 50 to 125 lb in 25 lb increments. Using a feedback loop and wireless signaling of climber activity, the controller provides more personalized performance than previously possible with increased safety and comfort in any tower.”

The wireless controller, actually a radio transmitter and load sensor, connects the body harness to the assist rope. “It’s worn between the climber’s harness and the belt, so you have a rope grab that attaches to the belt and a carabineer or lanyard attachment to the harness. The controller transmits signals to the motor to maintain the selected level of assistance and respond quickly to changes in climbing speed or direction,” says Crew.

The controller and load sensor for the lift assist fits between the climbers harness and tow rope. Climbers select one of four speeds for going up or down ladders.

The devise measures the pull between climber and belt, sending signals of these measurements 10 times each second to the motor controller. So when the climber tells the controller to set 100 lb of pull, when going up, that means via signals 10 times per second, the controller is telling the motor how much to pull on the climber. “This allows continuous motor power adjustments to maintain the assist load. So if climbing fast, the motor speeds to maintain the requested amount of pull. Likewise, the controller reduces motor power when necessary. So it makes the motor respond to the climber and not the climber to the motor,” he says. Users can set different assistance values depending on the climb direction.
“Big companies have hundreds of technicians serving a fleet of different sized and shaped turbines. This climb assist works for big guys and small guys, old guys, young guys, fast guys, and slow guys,” adds Crew.