When it comes to lifting transformers, aerial devices equipped with jibs are one of the handiest tools available to line workers.
Compared to old methods for transformer replacement, which required workers to climb the pole and use a pulley to manually lift the transformer, using a jib is safer, easier, and more productive.
Four key areas inform good practice for using jibs:
- Knowing your equipment.
- Inspecting your equipment.
- Knowing the load.
- Understanding proper setup – including the rigging and PPE required.
Most aerial devices sold to the utility industry are equipped with jibs. However, not all jibs are the same and the user should evaluate the type of work when choosing the equipment for the job.
Consider whether the tasks are construction or maintenance work on distribution or transmission lines. Before beginning the job, workers should know how the lines are situated relative to the vehicle's location.
In addition, the weight of the load will determine the required capacity of the aerial device and the jib needed.
Styles, Configurations, and Safety Considerations: Know Your Equipment
There are many different styles of jibs with varying capacities available on different boom and platform configurations, including side mount, underslung, end mount, and jibs that rotate with the platform.
There are also fixed length jibs, jibs that can be manually re-pinned to provide various extensions, or jibs with one or more sections that are hydraulically extendable.
Some units are designed with the load line above the jib boom and others below. Some jibs have sheaves that allow only non-overcenter lifting, while others can do either overcenter or non-overcenter lifting.
Jibs may or may not be insulated – ones used to lift loads other than conductors are not insulating. Terex Utilities does not supply insulated jibs for lifting loads, only added adapters for conductor lifting. Still, if you have one that is, the jib must be tested in accordance with OSHA 1926 and ASTM F-711 requirements for hot line tools.
Even so, Terex Utilities does not consider jibs as insulated, because the jib travels on the unit in a position that collects road debris that is not cleaned before use.
Although most jibs are made from non-conductive material, lifting loads can subject them to shock loads, which can cause cracks in the resin surface.
These cracks can absorb contaminants. In addition, as the jib travels in and out on wear pads or rollers, dirt gets embedded in the surface, increasing the chances of the jib becoming conductive. Finally, the jib is typically not treated as a hotline tool which is cleaned or inspected before use.
Likewise, the winch line must be considered conductive.
Some jibs or jib and winch assemblies can be removed. If the jib is not in use it can be removed, it is a good practice to remove and protect it.
Removing the jib has the added benefit of allowing crews to get the equipment into tighter spaces. However, if the entire jib/winch is removed, any exposed metal must be covered with non-conductive material to reduce the chance of inadvertent electrical contact.
A Closer Look at Jib, Winch Line, Hook, and Sling Inspections in Aerial Devices
The user must perform all inspections and maintenance of the jib, winch line, hook, and slings at intervals stated in manuals.
Daily inspections of the entire aerial device are required before use. As it relates to the jib, visual inspections include the jib, its support structure, the hook and safety latch, and the load line.
On the jib, look for damaged components, damage to the gel coat, cracks or corrosion, excessive wear, and any loose, deformed, or missing bolts, pins, fasteners, locking devices, and covers.
The synthetic rope winch line must be inspected daily for deterioration that could result in loss of strength.
Always follow the criteria provided in the aerial device manuals, from the rope manufacturer or the Cordage Institute. Among the conditions that should be reported to a qualified person to determine if the rope should remain in service are: excessive roughness, glossy areas indicating heat damage, flat areas or bumps/lumps indicating internal core damage, frayed strands, discoloration associated with chemical contamination, and stiffness due to embedded dirt or shock load damage.
Any hooks showing defects must be discarded. It is not permitted to make field repairs of hooks by welding or reshaping them. Among the defects to look for in a daily inspection are damaged or missing safety latch, cracks or distortions, and corrosion on the hook nut if equipped.
Navigating Maximum Capacities for Aerial Device Stability
Knowing how to read the load chart is critical for safe use and long life of the aerial device. Load charts provide the maximum capacity of the aerial device depending on the boom and jib or load line positions.
These values are not suggestions; they are absolutes. If exceeded, the stability, strength, and useful life of the unit is compromised.
Likewise, the winch capacity cannot be used as an indicator of allowable lifting capacity, the winch must lift the maximum capacity, which may significantly exceed the capacity at your working position.
The operator must know the load weight and the boom configurations required throughout the load travel path. The load chart provides capacities at various boom angles, load radii, or jib extensions. As the load is positioned farther from the boom tip the capacity, in most cases, is reduced.
Most aerials have the same capacity over the side and back. If there are restrictions, the information will be provided on the operator station's load chart or other labels. Terex Utilities designed its Load Alert system to help operators know if the boom condition is near capacity.
It monitors and analyzes the truck’s jib and basket capacity and provides visible and audible alarms to aid users when an overload has been detected.
A monitor display will read ‘overload’ when one occurs, and the background will turn red. The display also shows the actual load amount and will warn when the operator approaches maximum capacity.
There are a lot of differences in the size, weight, and shape of transformers. A 3kVA transformer weighs just 50 pounds, while higher capacity transformers weigh over 1,000 pounds.
New transformers will include the weight on the unit ID tag, but when removing old transformers, the weight of the load may be unknown. It is a good idea to refer to the brand name, model, and type of core to identify the weight. This information is usually available from the transformer manufacturer.
Optimizing Aerial Device Setup
Set the truck up in a way that positions the jib next to the load and pole. For example, units with side-mounted jibs can be positioned to the side of the pole, but you'll likely position the jib alongside you for a unit with a jib at the back of the bucket. The further extended the jib is, the less capacity you will have.
When lifting with a jib, following the manufacturer's guidance for setting up if on a slope is important. Working in an unlevel condition may cause the unit to tip, roll over, and sideload the jib if the capacity is exceeded.
This is especially true if the truck is set up on a slope and is lifting from the side. If the truck is outfitted with outriggers or stabilizers, they should always be deployed.
When deploying outriggers or stabilizers, outrigger pads should always be used to reduce ground bearing pressures and improve stability.
If you must set up on a slope or unlevel ground, the truck should be leveled by using cribbing to fill the gap between the outrigger pad on the ground and the outrigger or stabilizer in its level position.
Outrigger pads can be stacked to gain height as needed. Consider using interlocking cribbing blocks vs. loose wood timbers to reduce the risk of materials sliding or tipping. DICA offers two types of ProStack interlocking cribbing blocks, Slot Lock and Pyramid Lock.
“These plastic cribbing blocks interlock to provide height in environments where grade changes require cribbing to assist in leveling the equipment. ProStack is designed for equipment with outrigger loads that do not exceed 110,000 pounds, such as boom trucks, digger derricks, and aerial devices,” explains Kris Koberg, CEO of DICA.
Finally, Terex Utilities recommends always using an insulating section or link when lifting lines with a jib. The conductor lifter or insulating link must be treated as a hot stick.
The clear span distance of the insulating tool depends on the voltage. Users should follow OSHA 1926.950 to maintain the minimum clear insulation distances required.
Lifting transformers and lines is part of the everyday tasks conducted by utility crews. Aerial devices equipped with jibs have made this work easier and productive.
In some cases, aerial devices with material handling capability can also reduce the equipment needed on the job site. Most importantly, they can also improve safety only when used correctly. The next time your crew changes out a transformer, consider best practices for equipment selection, inspection, setup, and load capacity.