Use of boom lifts has become a common practice in the tower industry for providing quick and, seemingly, safe access to monopoles and low level work on free standing towers. Kathy Gill of Tower Safety and Rescue cautions that not understanding what the rigging capacity is for a given truck, and not having a rigging plan to go with it, can prove fatal. “We do not want another 2020, where several fatal accidents occurred caused by overloading or operating in unsafe conditions,” she said.
Gill broke down the seven different types of lifts for Inside Towers. “Some have a vertical reach of 65 feet and can safely put workers in position to service almost any electrical distribution,” she said. “Depending on the type of lift, some can be equipped with a manufacturer jib and winch, which allows for material handling. Material may range from working heights of a capacity of 1,000-2,000 lbs. Always refer to manufacturer guidelines.”
Boom lifts are designed and manufactured to the standards covered by ANSI 92.2 A Category C lift, Gill said, refers to the design of the boom, not the use. Category C is a boom with a lower test electrode, and the boom and basket are designed as secondary protection, whereas insulated tools are primary protection for the worker. Category C is limited to work on electrical systems below 46 kV.
The different types of lifts are:
- ARTICULATING TELESCOPIC BUCKET TRUCKS: Articulated/Telescopic Bucket trucks can unfold like traditional knuckle booms with an added telescopic feature. Allowing for increased side reach at higher elevations, while reducing tail swing on the opposite side of where the work is being performed.
- TELESCOPIC BUCKET TRUCKS: Different from the articulated version, the straight booms on these trucks have no knuckles and therefore can only extend telescopically.
- OVERCENTER BUCKET TRUCKS: Overcenter booms will allow the bucket to move beyond the center of the truck, extending the side reach, which can be especially useful for forestry, utility, and construction jobs.
- NON-OVERCENTER BUCKET TRUCKS: Non-Overcenter bucket trucks cannot move the bucket beyond the center of the truck and therefore are more restricted in their reach.
- INSULATED BUCKET TRUCKS: Insulated bucket trucks are mainly used by utility crews and those working around electrical cabling, because they help safeguard against accidental electrocution. Two components of these trucks are constructed of dielectric materials, to prevent conduction of electricity: the boom and the bucket.
- MATERIAL HANDLER BUCKET TRUCKS: Along with lifting workers, these trucks are designed to also lift a manufacturer approved load of material.
- TRACK BUCKET TRUCKS: Traction, ground pressure, suspension, and steering, make track bucket trucks an alternative in situations with rough, uneven, or swampy terrains.
Gill said OSHA has standards for safe use workers and training to operate boom lifts and aerial lifts. Boom lift training must cover how to avoid multitude of hazards, such as:
- Falling objects
- Traffic Control
- Structural failures
- Sling Angles
- Rated capacity of the hoisting equipment, ie. boom angles, working radius, line pull capacity
- How the load weight and load chart were determined, i.e., were the rigging plan, manufacturer data, calculation on slings, shackles, wire/synthetic rope/angles per ft. all taken into account?
- ANSI 10.48 Rigging rated capacity, based on material type and hitch configuration, ie. choke, angle of choke when taking load from horizontal to vertical
- Ground conditions – What is the bearing pressure while working over one corner?
- What is the supporting surface capability, ie. compacted ground, concrete, hot asphalt in summertime, sand?
- Responsibilities of all crew members – Foreman, Operator, Rigger, Signal person, etc.
- Extension of Boom & Bucket
A rigging plan is required with every lift, according to Gill, as is knowing the gross load, lifting angles, sling angles, wind speeds, load charts and unforeseen forces. Key factors in assessing your rigging plan are:
Rigging Plan Physics:
- The further the load in the bucket is extended horizontally from the base, the closer the center combined gravity moves toward the fulcrum point, causing capacity and stability to decrease.
- If a crowded jobsite (like a busy roadway) where an unexpectedly large tail swing arc can pose a danger to people or things.
- A combined weight of occupants, tools, equipment, and other material that the manufacturer has indicated can be safely carried in the bucket.
- The higher the bucket is elevated off the ground, the more the stability is decreased.
- Do not operate the bucket truck fully extended beyond the manufacturer’s wind restrictions.
- The highest point in the platform is your head.
- Side Reach: Horizontal distance the bucket with the manufacturer approved WLL Jib will extend.