Every lift on a telescoping-boom crane is a chain: the load, the rigging, the hook, and the machine. That chain is only as strong as its weakest link. Before you ever touch the controls, you need to know exactly what you are lifting, how you are securing it, and who will be directing you. This session covers the rigging fundamentals and communication practices that keep that chain from breaking.
Know your load before you rig it
The first question in any lift determines everything else: how much does this load weigh? Check the shipping documents, look for weight markings stenciled on the load, or estimate by calculating volume and multiplying by the material's known density. Guessing is not an option. The load chart in your cab is only useful if the number you bring to it is accurate.
Once you have the weight, find the load's center of gravity. The hook must be directly above that point before the load leaves the ground. If you are off-center, the load will swing or tilt the moment it comes free — and correcting a swinging load with the boom is exactly the kind of uncontrolled motion that injures people.
Slings, hitches, and the sling-angle effect
Wire rope, chain, and synthetic web or round slings each have their place depending on load surface, weight, and environment. Inspect every sling before it goes on the hook. A cut in a synthetic sling, a kinked wire rope, or a stretched chain link is a failure waiting to happen under load.
How you attach the sling matters as much as the sling type. A basket hitch wraps under the load and back to the hook, giving the highest rated capacity. A choker hitch cinches around the load for irregular shapes but carries a reduced rating. A vertical hitch is only appropriate when the attachment point is directly above the load's center.
Sling angle is where many operators get into trouble. When two-leg bridle legs spread at a shallow angle to the horizontal, each leg carries far more than half the load weight. Tension increases dramatically below 45 degrees. Keep legs as vertical as practical — nearly horizontal legs can impose forces that far exceed what the rigging or attachment points were rated to handle.
Hardware, signals, and controlling the load
Every piece of rigging hardware must show a visible Working Load Limit. Never use a shackle, hook, or eyebolt with no WLL marking — there is no safe way to know what it can hold. Match the hardware to the actual hitch configuration and angle, not just the straight-pull rating on the tag.
Signal communication takes two forms on a crane site: hand signals and voice or radio. Hand signals are the traditional standard and every operator and rigger must know the full set — hoist, lower, raise and lower boom, telescope in and out, swing, stop, dog everything, and emergency stop. Voice or radio communication is an accepted alternative when the operator and signal person have a clear, reliable channel and both parties agree on the protocol before the lift begins. Regardless of method, a designated signal person is required any time the operator cannot see the load or the landing zone. That person is the only one authorized to direct crane movements — with one exception: an emergency stop can come from anyone on site and takes absolute priority. If you receive a signal you cannot clearly understand, stop. Do not try to interpret an ambiguous gesture. Stop also if you lose sight of your signal person mid-motion and hold until you reestablish contact.
Once the load is in the air, move smoothly. Tag lines give ground workers control over load rotation and keep the load from drifting into structures or people. Sudden starts, abrupt stops, and fast swings create dynamic loading that multiplies forces well beyond the static weight. Never drag or pull a load sideways with the boom. Side-loading acts on a telescoping boom in a direction it was never designed for, and that structural overload can collapse the boom before any safety device reacts.
Key Takeaways
- •Verify load weight before rigging using shipping documents, markings, or volume calculations — never guess.
- •Position the hook directly over the load's center of gravity to prevent swing and tip when the load leaves the ground.
- •Sling angle is critical: as legs spread toward horizontal, tension in each leg increases sharply. Keep legs as vertical as practical.
- •All rigging hardware must show a visible Working Load Limit matched to the actual hitch and angle in use.
- •Only the designated signal person directs crane movements. Stop on any unclear signal or lost visual contact. Never side-load or shock-load the boom.