Gusting Wind and a Sail-Area Load
You are signaling a 150-ton crane setting an empty fiberglass tank that weighs 1,500 pounds but is 12 feet in diameter, so it has a large sail area. The forecast is 15 mph with gusts to 25 mph. The tank is 20 feet above the ground and has no tag lines attached. The operator is looking at the load indicator and says the lift is well within the chart. A gust hits, and the tank begins to rotate slowly. The operator cannot see the rotation because the tank is on the far side of the boom. You are in a clear line of sight. Your radio is in your truck, but your hand signals are visible to the operator.
1. What hand signal do you give first, and what should happen to the load?
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Give the stop signal first: arm extended horizontally, palm down, moving back and forth. The operator must stop hoisting and swinging. Because the tank is already rotating, do not use a rapid emergency stop that could make the load swing harder; stop controlled movement, then give the lower signal-arm extended downward, forefinger pointing down, moving the hand in a small horizontal circle-and lower the tank slowly to the ground. Dog it once landed. Do not continue the set. Get tag lines on the load and clear the area under the tank.
2. What conditions would make you stop the lift before the tank is set, and when may it resume?
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I would stop for any gust that starts the tank rotating, any loss of tag-line control, any condition where the operator cannot see the load or me, or any wind above the manufacturer's or site's limit for that sail area. A 1,500-pound load is not automatically safe in wind; the 12-foot diameter gives the wind a large area to push. Resume only when the wind is below the applicable limit, tag lines are attached and tended, the operator and I have re-established communication, and the lift plan addresses the sail area. If conditions repeat, the lift director should reschedule.
3. The operator says the load is only 1,500 pounds, so wind does not matter. How do you respond?
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I would explain that the load chart is about structural and stability capacity, not load control. A light, large tank can be pushed by wind even when the crane is not near its chart limit. The rotation shows the load is no longer under control. My stop is based on observed motion and sail area, not on the weight alone. I would not resume until tag lines and wind limits are addressed.