It’s a sobering fact that many of the support structures holding up the world’s electrical grid are nearing the end of their serviceable life. After 50 or so years, wooden electric poles and corresponding cross supports inevitably rot and need replacement. When they do, power company linemen get in an insolated bucket and are hoisted by a crane as much as 50 feet in the air to repair those structures. However, many times the equipment used to hold the energized electrical lines in place while the work is done is less than ideal, creating a potentially hazardous environment.
LinePro Equipment is a manufacturer of insulated crane and digger derrick attachments for energized transmission and distribution line maintenance. Among their products, the company’s Insulated Conductor Supports Jibs (ICSJ) temporary support energized ultra-high voltage power lines to allow faster and safer insulator and tower replacement/relocation.
“With electricity, you only get one mistake. There have been fatalities using equipment that was inadequate. Our products help to keep linemen out of harm's way.”
Larry Ewert, product designer, LinePro Equipment
In addition, the company’s LinePro HA aerial devices are configurable as a Live Line bucket truck/aerial platform device, an energized conductor support, pole setting vehicle, and a material-handling crane. “In the past, we’ve used a multi-pin hole for the buckets and the supporting conductors,” Ewart says. “Linemen used to set the position on the ground, lift it up and hope they had the right angle. If they guessed wrong, they’d have to bring it all down and set it, so it was time consuming.”
A former vehicle technician with BC Hydro, Ewart recognized the safety and productivity issues involved in the traditional multi-pin method and designed an improved aerial device that includes hydraulic actuation, so the company’s bucket truck/aerial platform devices could be repositioned in the air, by radio control. According to Ewert, precise platform positioning without drift increases safety and allows for various degrees of articulation.
Rotary actuator solutionFor hydraulic actuation, LinePro Equipment relies on Parker’s Helac actuators, specifically the L30-215 helical rotary actuators, which is responsible for the articulation and boom positioning. Ewart says Helac actuators provide jib storage and quick deployment not previously available. “
We can’t accomplish the same thing with cylinders because they’re too cumbersome,” he says. “Because we get the same articulation out of a compact package, Helac actuators are more efficient for what we do.” The actuator functions as a rotating device, mounting bracket, and bearing support. The large circular shaft flange with drilled and tapped bolt circle is used to attach the actuator to the jib boom.
The characteristics of the helical rotary actuator make it ideal for this platform. Parker’s L30 helical actuator series offers high load carrying, high torque output, compact configurations, and corrosion resistance in a cost-effective package with 180-degree rotation. Its sliding-spline operating concept produces output torque to 215,000 pounds per inch at 3,000 psi. At the same time, the actuator measures 23.6 inches with a 10-inch housing diameter and weighs 790 pounds.
Because the spline teeth remain engaged at all times, loads are equally distributed over the teeth, resulting in increased shock load resilience. Large integral nylon composition bearings support heavy radial, moment, and thrust loads without additional external bearings. Sealing occurs against smooth cylindrical surfaces, effectively eliminating leakage and enabling selected positions to be held without drift.
Parker’s Helac helical rotary actuator assists LinePro’s aerial devices to be safer and much more efficient. The load holding capability allows for safety with either the aerial work platform or the insulated conductor support application.
This article was contributed by Jessica Howisey, marketing communications manager and Daniel Morgado, applications engineer, Helac Business Unit, Cylinder Division and was originally published by Design Engineering.
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