Cargo containers are an easy solution for providing both job trailers and lockboxes on construction sites. Containers come in various sizes and with rigging, or picking points, already identified on the unit. When it is time to offload a 20-foot container, a crane or forktruck can do the job easily. As long as the lifting machine is rated to handle the total weight of the container and its contents, and the operator is well-trained, offloading a 20-foot container will take little time.
- Skill level:
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Things you need
- Lifting machine (crane or forktruck)
- 4-way rigging gear with hooks (if needed)
Attach the 4-way rigging to the picking ball off the boom of the crane and hoist the rigging so the end hooks are above the top of the container. Let any sway to the rigging settle before continuing.
Move the boom so it is centred on the container, remembering to watch the position of the tip of the boom arm and not the picking ball. Note the degree and position of the boom from the guide gauges in the crane cab.
Raise the boom while lowering the rigging until the hooks hit the ground. Connect the four hooks to the four labelled picking points at each corner of the bottom of the container.
Lower the boom back to the centre point on the container. Take up the slack in the rigging by raising the load line but do not pick the load up. Check that the hooks are still secure in the picking points.
Offload the container by raising the load line to pick the container off the platform and swinging the boom to bring it over where it is to be landed. Lower the container and disconnect the 4-ways from the picking points.
Drive the forklift as close as possible to the container position so the forks are centred on the container.
Adjust the forks to their maximum spread. Lower the fork frame straight down or, tilt the head to dangle the forks from the frame and bring them into reach. Lift the tip of each fork up slightly and push on the fork body to slide it to the outermost position on the frame pole. Raise the boom and level the fork frame when done.
Slide the forks under the container, making sure to keep the line of the boom centred on the container. Place the forks into the gap between the container and the support surface created by the container frame or, tilt the forks down and pick the edge of the container up slightly with the tips. Push the forks under the container while lowering the forks back to a level position to prevent the container from tipping.
Lift the boom to take the weight of the container while tilting the forks back to slide the container against the fork frame.
Offload the container by retracting the boom and/or reversing the fork truck. Lower the boom to bring the container close to the ground as soon as possible for driving it to its landing position, to prevent the container from falling off the forks or the forktruck from tipping forward.
Tips and warnings
- Swing the boom (or drive the forktruck) along the path to be followed when unloading before the container is picked to make sure there are no obstacles to be cleared.
- Never move a load over a person. If the load should fall, serious injury could occur.
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- Shipping-container-housing.com: Shipping Container Specification -The Story of Standardization
- Army Logistician: Containerizing the Joint Force
- Associated Builders and Contractors: Crane Rigging - The Hoisting Triangle
- Texas A&M University: Guideline for Cranes, Hoists & Rigging Safety
- Concretees.com: Moving Material by Forklift