Aerial lifts are designed and built to be operated on flat, solid surfaces. However, many job sites, especially those outdoors, don’t have flat, even surfaces. This increases the risk to the operator and workers on the ground. It also increases the risk to others working or passing nearby.
There are two basic types of aerial lifts – boom lifts and scissors lifts. Boom lifts are more versatile than scissor lifts. They use a hydraulic arm to raise the working platform or bucket. This allows the platform to move on a horizontal as well as vertical plane. This, in turn, makes it easier to access job sites that are hard to reach. As a result, boom lifts are usually the preferred choice for outdoor jobs.
Scissor lifts can only go straight up and down. The work platform is raised by a scissor-like mechanical device that gives it more stability than boom lifts. However, scissor lifts can’t go as high as boom lifts. Boom lifts can achieve heights of 150 feet and more. Scissor lifts have a vertical ceiling of about 50 feet. They tend to be used more at indoor work sites. But some scissor lifts are designed for outdoor terrain.
Operating on Uneven Terrain
Even on flat, smooth terrain, working on an aerial lift involves risk. Working on sloped or uneven ground makes it even more risky for inexperienced operators. That’s why OSHA requires all workers be trained and certified before operating an aerial lift. This ensures that workers know how to avoid work site hazards that can result in serious injury or death.
Boom lifts are commonly used on outdoor work sites. Articulating boom lifts use hinged sections to extend the platform over and around barriers. They are sometimes called “knuckle booms,” and are best for working in areas where access is tight.
Telescopic boom lifts have booms that can extend upward and outward. Also called “stick” lifts, they look a lot like very large forklifts. They offer more horizontal reach than any other type of aerial lift. This makes them a good choice when working from a distance or on rugged, uneven ground.
Know Your Aerial Lift’s Slope Rating
Telescoping lifts are usually the preferred type of lift when working on sloped ground. No matter which type you use, the platform should be raised only when set up on firm ground. Most important, only trained and certified operators should use boom lifts on sloping ground. This means training on the specific type of lift being used and safety guidelines for working on uneven terrain.
Every aerial lift has a slope rating that lists the highest angle of slope that is safe to work or drive on. Knowing the degree of slope on a job site is vital to machine stability and worker safety. If the angle of the lift chassis exceeds this rating, the operator may not work at height. This can occur when the ground slope is too steep. It can also occur when the lift is set up on sidewalks, ramps, or uneven gravel. In some cases, plywood cribbing can be used to bring the surface within safe limits. If not, a lift with longer outreach may be needed to position it on safe ground.
Before driving a lift on a slope, use a digital inclinometer to find the exact degree of slope. If you don’t have one on hand, lay a board or other straight edge on the slope. The straight edge should be at least three feet long. Set a carpenter’s level on the board. Then do these steps to figure out the percent of slant:
- Raise the lower end of the level until it is horizontal
- Measure the distance to the ground
- Divide that number by the length of the board
- Multiply that number by 100
If the number you end up with exceeds the max slope rating, the lift will need to be winched or hoisted across the sloped area.
Max slope ratings can be affected by ground conditions and weather. For example, the normally solid ground can often get soft after a heavy rain. Mud or loose gravel can reduce traction and extend stopping distances. Always reduce driving speed when crossing sloped or rough terrain. Take extra care when driving or working near drop-offs or cliffs.
Boom lifts used on slopes have a higher risk of tipping over in high winds. Never use them in winds above 28 miles per hour. Also, be sure to check the overhead area for obstacles or live power lines. Stay at least 50 feet away from electrical wires on steel towers, and 30 feet from wires on wooden or concrete poles. Allow a safety zone for wires swinging in high winds.
Some aerial lifts have built-in slope sensors. Operating these lifts on an angle that exceeds the max slope rating will trigger visual and/or audible alarms. When that occurs, the lift should be lowered and move to a surface within the slope rating limits.
- Know the slope rating for the lift; do not exceed it under any conditions
- Thoroughly inspect the lift before starting the job
- Make sure the tires have the right amount of air pressure
- Check the job site for uncompacted fill, ditches or large holes
- Check the weather report before starting work
- Make sure workers wear proper personal protection equipment
- Do not raise, extend or operate the platform or bucket unless the lift is on a firm, level surface
- Adjust stowed travel speed according to the surface traction of the slope.
Most of all, make sure all workers on the aerial lift are trained and certified to work on slope. This can be easily achieved with companies like AerialLiftCertification.com, which offer fast, affordable online training.
Tom Wilkerson is CEO of AerialLiftCertification.com (CMO), a national leader in online, OSHA-compliant aerial lift training and certification. CMO has helped thousands of companies throughout the U.S. discover the easy way to self-certify their aerial lift operators in-house.