Aerial-work platforms (AWPs) perform a simple task: They enable workers to reach their job safely when it's not at ground level. Beyond that, though, knowing which AWP to use requires answers to a wide range of questions about the application and terrain. More so than with most other construction equipment, AWP acquisition depends entirely on the specific task at hand.
The first differentiator is application. How high does it need to lift and how far does it need to reach, if at all? The answer to this question immediately guides the user to one of three types of work platforms: scissor; telescopic, also known as boom lifts; or articulated, also known as knuckleboom lifts.
Scissor lifts work well in straight up-and-down applications with heavy loads. Scissors generally have platforms large enough for a number of workers, plus tools and materials. They have large lift capacities, too, and are used extensively indoors so they're usually battery-powered.
For greater height or for horizontal reach, a telescopic-boom work platform works best. Telescopic work platforms can be extended and retracted quickly.
Don Ahern, president of Ahern Rentals, Las Vegas, boils selection down to horizontal reach. "If you're looking for something without [horizontal reach], then scissor lifts are generally more economical. If you need a lot of horizontal reach, you need the straight [telescopic] boom."
Many telescopic lifts have an articulated jib that allows them to reach into obstructed or confined areas. The forward reach is limited, but it does allow the worker to access restricted areas and to move up and over obstacles.
More and more, the AWP of choice around construction sites is the rough-terrain version of the boom lifts. These units typically feature four-wheel drive and oscillating axles. Rough-terrain AWPs still need to operate from level ground, and many have sensors that will alert the operator when the AWP is out of level beyond a certain safety range.
Larry Workman, owner of Illini High Reach, a Lemont, Ill.-based rental dealer, says he tends to buy diesel-powered, four-wheel-drive boom lifts because they handle most jobs well. "Diesel is better than gasoline on the jobsite," he says. "It provides more horsepower and better fuel economy. You could use two-wheel drive on hard-packed surfaces with little rain, but here [in the Midwest] you could rent it six months, not nine. Four-wheel drive also allows us to turn the machine over in resale."
Workman recommends straight telescopic booms for most outdoor construction work because there is little need to move around obstructions. "The telescopic [lift] doesn't wobble and it doesn't have the extra stick" needed to control an articulated jib. "[The user] wants to go up and down fast, so he doesn't feel like he's falling asleep."
Ahern says platform controls have been improved of late. He looks for controls that are ergonomic and allow for simple operation out of the basket. Additionally, says Jesse Spencer, site superintendent for contractor A. Zahner Corp., today's AWPs provide more generator power for the platform, allowing users to operate tools while in the air.
"They've added larger generators on some of the machines," he says. "That's huge when you don't have to run power up to the lift, especially at higher heights."
Most manufacturers now offer foam-filled tires so rough-terrain usage doesn't result in flats. From a safety standpoint, this provides additional security that the platform will remain stable, says Workman. "It gives the guy in the basket peace of mind," he says. It also reduces downtime.