Alley Pick Beside a Vault and Power Line
A contractor plans to set a 3,200 lb rooftop HVAC unit on a three-story building using a 28-ton boom truck. The only parking area is an 18 ft wide alley. With outriggers fully extended, the truck needs 22 ft across, so one outrigger will sit on a sidewalk over a basement vault and the other near a curb. The planned pick radius is 38 ft; the chart shows 5,100 lb at 40 ft with outriggers fully extended and the planned boom length. A 13.8 kV distribution line runs along the building at 24 ft above the alley. The delivery truck will block the alley during the lift, and pedestrians use the sidewalk. The unit must land 20 ft back from the roof edge, and the operator cannot see the landing point from the cab. The general contractor asks whether the lift can proceed with a spotter and warning tape.
1. Identify the site and planning issues that must be resolved before this lift, and state whether the information given is enough to approve it.
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The information is not enough to approve the lift. The 22 ft outrigger spread does not fit the 18 ft alley with full extension, so the truck cannot simply be parked as proposed; the contractor needs a road closure, a different position, or a different crane. The outrigger over the basement vault is a ground-bearing problem, not a sidewalk problem: the vault must be evaluated by someone competent to confirm it can carry the outrigger reaction, or the outrigger must be moved. The power line requires the utility's required clearance for the boom, load, and rigging, plus controls to prevent encroachment; a spotter and tape are not a substitute for de-energizing or maintaining the required distance. The blind landing requires a designated signalperson with a clear view or a relay. Capacity at 40 ft is 5,100 lb before deductions, and the 3,200 lb load appears to fit only if the actual radius stays at or below the charted radius, hook block and rigging are deducted, and the outrigger configuration matches the chart. Verify those before approving.
2. If the utility locate shows the vault is directly under the right rear outrigger, what are acceptable options, and what should not be done?
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Acceptable options are to relocate the crane so no outrigger loads the vault, use an engineered load-spreading bridge approved by the vault owner or a structural engineer, or change to a crane and position that keeps all outriggers on competent ground. Any new position changes the radius and swing, so the chart must be rechecked. Do not place a pad directly on the vault cover and assume it will hold, do not 'test' the vault by extending the outrigger onto it, and do not crib only the visible edge while the float still bears on the cover. Because the alley is narrow, relocating may require a traffic-control plan and may put the boom closer to the power line, so clearance must be re-evaluated. If the vault cannot be verified or bridged, the lift should not proceed at that position.
3. The operator says he can boom down until the load is visible and use a radio. What must be in place for that blind lift?
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A designated signalperson must be positioned so they can see the load, the landing point, and the operator, or a relay signalperson must be used with clear, tested communication. The radio must be on a dedicated channel or a controlled protocol, tested before the lift, and backed up by agreed hand signals. The operator must stop immediately if communication is unclear or lost. The signalperson needs authority to stop the lift, and the roof landing area needs an exclusion zone because the operator cannot see it. The spotter on the ground can help keep pedestrians out, but a spotter is not automatically a qualified signalperson. The boom and load still must maintain the required clearance from the 13.8 kV line throughout the boom-down and swing, and the load must not be moved over pedestrians. A blind lift without those controls should not start.