Blind Roof Set with Intermittent Radio and No Visible Signal Person
An articulating crane is setting a 2,400 lb air-handling unit onto a roof. The operator is at ground level on the west side of an 8 ft concrete wall and cannot see the pick point or the roof landing area. A rigger at the truck uses a two-way radio to direct the boom. A second worker on the roof gives hand signals to the rigger, who repeats them by radio. The radio intermittently cuts out, and the rigger sometimes says 'a little more left' without a distance. The operator has a camera on the boom tip, but the view is obstructed by the wall. The roof worker is not visible to the operator. During the lift, the rigger steps behind the truck to check a sling and stops transmitting. The load is suspended 12 ft above the roof. The operator wants to continue the swing slowly to the landing point because the load is close.
1. Who is the signal person, and what communication requirements apply?
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A qualified signal person must direct the operator, and the operator must know who that person is. Here the roof worker is acting as the primary signal person, but the rigger is relaying, which adds delay and can distort the signal. The radio must provide clear, distinguishable signals; 'a little more left' is not a usable signal because it gives no direction reference or distance. Voice signals should follow a standard format, or hand signals should be used when the signal person is in view. If multiple signal persons are used, each must be qualified and the operator must be able to identify which one is directing. Because the roof worker is not visible and the radio is intermittent, the communication method is not adequate for a blind lift.
2. What should the operator do when the rigger stops transmitting with the load suspended?
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Stop and hold the load. A suspended load 12 ft above the roof is a hazard, and the operator must not continue a blind swing without a signal. The operator should try to re-establish communication with the rigger or roof worker and keep the area below the load clear. If the radio has failed, use a pre-arranged backup such as a qualified signal person who is visible to the operator or a direct radio link from the roof worker. If no communication can be restored, hold the load and secure the area rather than guess. Silence is not a signal to continue. Lowering may be appropriate only if it can be done safely and was planned.
3. What is wrong with the operator's plan to continue the swing slowly?
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The operator cannot see the load, the landing area, or a qualified signal person, and the camera view is obstructed. Moving slowly does not make a blind lift safe. Without a signal, the operator cannot know whether the load is clear of the wall, roof edge, or workers, and a slow swing can still contact an obstruction or swing the load when it is freed. The correct action is to stop, restore clear communication, and reposition the crane or use a signal person who is in view. If the lift cannot be controlled with direct signals, the lift plan must be changed.