Crane-assisted rigging is a complex layering of skills, equipment and knowledge. Like many involved tasks, it looks relatively simple when done well. However, the truth is that when poorly planned, cranes and trees can be a difficult combination. Add in the likelihood of heavy loads, and incidents can become catastrophic quickly. An additional complexity is that cranes are not exclusive to arboriculture.

Sling plan: Sling plans decide what type and orientation the slings are placed in to accomplish the hoist plan. All photos courtesy of the author.

As such, their use comes with a well-established set of protocols, practices and regulations developed by other industries. Blending these existing regulations and best practices with the unique requirements of arborist crane-assisted technical rigging is the focus of our discussion here.

The goal is to develop a good plan to support best practices and protocols for crane use on the tree care job site.

Critical lifts

It is important to understand that, by crane-industry standards, almost every lift an arborist makes during crane-

assisted rigging operations is considered a critical lift. Meaning that special precautions and planning are necessary. Critical lifts can come in many shapes and forms, and the standards differ by crane type, industry and local regulations.

1. Here are just a few factors present during a critical lift:
2. Lifting of personnel.
3. Imprecisely calculated or unknown loads.
4. Lifts over structures or other sensitive objects.
5. Lifts around electrical conductors.
6. Cranes set up on unstable soils or untested platforms.

With just a casual glance, one can see that tree work with cranes coincides with the criteria for a critical lift nearly every time. The very nature of our work, work sites and tree biology and structure adds hazards to crane use in arboriculture. While each locality will have slightly different variations of specific legislation, one constant is the need to plan and document a critical lift. To do that, we will discuss a five-step lift plan.

The lift plan

The lift plan encompasses all major aspects of the climber’s, lift operator’s or sawyer’s needs to safely, efficiently and productively sling, cut, lift, land and process tree parts and pieces, or even whole trees. The lift plan will help us organize our work for maximum effectiveness. It has five main parts, which will be discussed in depth. Again, we can only deal in generalizations, as the ways cranes are used safely in arboriculture are as varied as the crews using them. The idea is to build a framework that can be adopted by companies or crews to suit individual needs.

1. The five-step lift plan consists of a:
2. Hoist plan.
3. Sling plan.
4. Communication plan.
5. Cut plan.
6. Landing plan.

Hoist plan: Determining the final orientation of the piece after it is cut.

Hoist plan

The hoist plan is how the arborist would like the piece lifted and in what orientation the piece will be when fully suspended by the crane. We will look at five general types of hoists:

1. Tip.
2. Balance.
3. Lift.
4. Swing.
5. Static.

Tip: This hoist ends with the piece being oriented tip near the hook and the butt end hanging straight below the tip. In rope rigging, we would call this a butt-heavy rig or tip tie. Tip hoists can be used on vertical pieces as well as horizontal ones. Horizontal or any piece less than 90-degrees vertical will involve the piece moving as the crane cables and/or booms are moved.

Balance: Balance hoists end with the piece balanced in a generally horizontal plane. They may move or swing to avoid obstacles or to clear the sawyer or facilitate landing. Strictly speaking, a tip hoist that starts vertically is balanced. The difference is that balanced hoists may move in multiple directions when fully supported by the crane before coming to rest.

Lift: This type of hoist is the most basic and involves lifting a piece from a fixed position. An example is loading logs that have already been landed into a truck or other processing means. These types of lifts often have very accurate weight estimates due to the pieces already having been handled or the ability to make more precise measurements and calculations. These are the types of hoists most often used outside the arboricultural industry.

Swing: These hoists allow the piece to move before release. The movement may be in any plane and may involve multiple movements. The movement must be controlled to avoid shock loading the crane. Generally, swing hoists are used to avoid the sawyer, equipment or other site obstacles. They should be used carefully and selectively, as any movement of the load will introduce increased forces into the system.

Static: Static lifts keep the piece in the same orientation as before cutting. There should be little to no movement, so these require precise sling placement and weight estimation, as well as precise cutting. These are often the most desirable for tree work, as they help manage compression and tension forces in the wood during the cut. They also avoid shock loading the crane when proper tension is applied pre- and post-cut.

Use any terms you prefer, but understand that the first step is to decide how you want and/or need the piece selected for removal to maneuver and/or hang after the cut is made. We can now move on to the next step.

Sling configurations: Depending on the configuration, stability and capacity can be greatly affected. Use appropriate slings in appropriate configurations.

Sling plan

Sling plan is how the piece will be attached to the crane hook. The sling plan must complement the hoist plan or desired final orientation and/or movement of the piece. Several factors must be considered, such as:

1. Sling materials.
2. Sling configurations.
3. Types of slings.
4. Sling attachment.
5. Sling angles.

There are a number of materials available for slings. All slings should be load rated and labeled for overhead lifting. The load-rating labels must be intact and legible. Furthermore, the sling material should be resilient and suitable for the demands of tree work. Slings should be inspected before every use and retired as necessary if there is any doubt as to their strength.

There are three sling configurations: straight, basket and choker. The weakest is the choker configuration, but it is also the most common. The arborist must be aware that reduction in sling strength in the choker configuration takes two forms. First, strength is lost at the bend in the sling where it physically cinches tight. Second, strength is lost depending on the angle the sling exits from the cinch point and goes to the crane hook. Both factors must be considered.

How the slings load the crane hook must be considered as well. The hook is at its maximum capacity when loaded straight on the center section of the hook. As the slings load other parts of the hook off the centerline, capacity is reduced, as those sections of the hook have lower breaking strengths.

Depending on the hoist plan, the type of sling attachments must be considered. Generally, there are three basic types:

• Single: Single denotes a single sling attached to the piece. Usually, a shackle or other attachment hardware is employed to increase efficiency.
• Multi-sling: Multi-sling attachments have two or more slings attached to the piece. Essentially, having more than one single sling attached to the same load is considered multi-sling rigging.
• Spider-leg: Spider-leg sling plans consist of one main sling with various small slings attached via Prusik hitches to the main sling, then tied to the piece with appropriate hitches.

Determining the best sling types and their configuration is an art and a skill! Understanding the technical aspects of sling materials, capacities and loading is as vital as infield practice and training in baseball.

Communication plan: Communication is key. Determine the best method for the cutter, the crane operator and the ground crew to communicate.

Communication plan

Good communication between the sawyer, crane operator and ground crew is vital for safe, efficient crane-assisted rigging. While there are many ways to communicate, what is most important is that an appropriate and effective communications plan be established before work begins. As with any plan, it should be adjusted or modified as necessary.

The three most-used methods of crew communication are:

1. Voice.
2. Hand signals.
3. Headsets.

They should each be evaluated for their effectiveness and usefulness for the job at hand. In certain circumstances, such as when the cutter and the crane operator are not within line of sight, certain communication protocols might not only be desirable but mandatory. The advent of Bluetooth communications on tree crews makes the choice often simple, but there are many ways to effectively communicate. Choose what best fits the site, crew and task.

The cut plan complements the hoist and sling plans and keeps the sawyer in a safe position before and after the cut.

Cut plan

The cut plan is how the arborist is going to physically detach the piece from the tree. The cut must work in conjunction with the sling plan to accomplish the hoist plan.

There are many types of cuts and variations on themes for cutting trees or tree parts attached to a crane. An independent discussion of the many methods available is beyond the scope of this article. Suffice it to say that the cut you use should accomplish the end goal of the hoist-plan step, keep the sawyer in a safe position before and after the lift and have as much predictability as is reasonably possible under the circumstances.

Landing plan

Lastly, we come to the landing plan. Here, the arborist considers how the piece will be processed after it is removed from the tree. The load radius to the landing area must be considered if it is greater than the distance to the cut. If the landing zone is further from the crane than the cut, the load should be sized for the lowest rating or the greatest distance it will travel. Crane stability and capacity must not be exceeded when cutting or landing the piece

Many times, the crane is capable of lifting a piece much larger than can easily be processed by the ground crew and equipment. However, if the landing zone is not adequate for the size of the piece, safety and efficiency can be compromised. By sizing lifts appropriately, a smooth job flow can be accomplished. Safety also can be increased by a less-crowded, less-hectic job site

Proper landing plans also can help minimize severely loaded branches trapped under the freshly landed piece. This is an often-hidden hazard, difficult for the ground crew to detect, but very dangerous.

Excellent landing plans also help reduce rigging cycle time. This is the amount of time it takes for one piece to be processed so the next piece can be cut and placed in the landing zone. Good landing plans get the crane back to the sawyer effectively and facilitate smooth operations.

Landing plan: The lift is not over until it is safely off the hook and ready to be processed. Excellent landing plans enhance safety and efficiency.

Conclusion

Crane work on the tree site is an involved process. The nature of the work and the loads lend a unique, inherent set of hazards. To meet the varied requirements – but mostly to have safe job sites – it is important to have a good plan.

Our discussion here laid out the framework of a basic five-step lifting plan that incorporates the various aspects cutters and crews need to consider for safe, effective work. Use it as is or as a guide to develop your own plan.

Anthony Tresselt, CTSP, is a consultant serving as director of safety and training for Arborist Enterprises Inc., an accredited, 34-year TCIA member company based in Manheim, Pennsylvania. He is also an independent trainer based in Manheim.