The Load Chart That Doesn't Match the Attachment
You are assigned to handle an empty 20 ft container that has been modified with a permanently welded steel frame and lifting lugs on one end, used for storing site equipment. It is not a standard container and has no CSC plate or weight marking. The site engineer estimates its mass at 2.8 t but has not weighed it. Your machine's load chart has two columns: one for the standard spreader and one for a hook/sling attachment. The container cannot be picked up with the spreader because the corner castings on the modified end are obstructed by the welded frame. The only available attachment is a four-leg chain sling with hooks, rated 5 t per leg, and the machine's chart for the sling configuration at the required radius shows 4.5 t. The centre of gravity of the modified container is not marked and the welded frame is on one end only.
1. Identify the technical problems with this lift and explain how each affects the decision to proceed.
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1. Unknown mass. An estimate of 2.8 t is not a weight. With a 4.5 t chart limit, the margin is 1.7 t - but if the estimate is wrong by 60% the lift is already over capacity. The load must be weighed, not estimated.
2. Unknown centre of gravity. The welded frame is on one end only, so the CoG is offset from the geometric centre. A sling lift assumes the CoG is under the hook; an offset CoG causes the container to hang at an angle and shifts load onto individual sling legs. With four legs, the load is not shared equally - the legs nearest the CoG take more, and one leg could exceed its share even if the total is within the 5 t per-leg rating.
3. Attachment mismatch with the chart. The 4.5 t figure applies only to the sling configuration as defined by the manufacturer. If the sling is rigged with a different leg angle or a different number of legs than the chart assumes, the rating changes. The chart is not transferable.
4. No CSC plate or marking. The container's structural condition and lifting points are unverified. A welded frame of unknown design and weld quality is not a certified lifting point.
5. Spreader cannot be used. The machine is being operated outside its normal configuration, which increases the need for a documented lift plan.
2. What would a safe plan look like, and what would you refuse to do?
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Refuse: I would not lift it on an estimated mass with an unmarked CoG using an improvised sling arrangement on an uncertified welded frame. The combination of unknown weight, unknown CoG, and non-standard lifting points removes every margin the load chart depends on.
Safe plan:
- Weigh it - a weighbridge or load cell reading, recorded.
- Establish the CoG - have the container assessed, or rig a lift that is tolerant of offset (e.g. a spreader beam with adjustable slinging) under a documented lift plan.
- Certify the lifting points - the welded frame and lugs must be designed and inspected by a competent person, with a rated capacity.
- Match the attachment to the chart - confirm the sling configuration, leg angles and number of legs correspond to the manufacturer's sling column, and that the chart capacity at the actual radius exceeds the weighed mass with margin.
- Lift plan and supervision - a documented plan, a trial lift just clear of the ground to check hang and stability, exclusion zone, and a spotter.
- If any of these cannot be met, the lift does not happen - the container can be emptied and moved in a certified configuration, or handled by a crane with a proper lift study.