Crane Lift Study Calculator

The safest option is to have the power line isolated, de-energised, visibly grounded and confirmed safe by the electricity utility or authorised electrical person before crane operations begin. Treat every overhead line as energised unless this confirmation has been obtained.

The minimum clearance applies to every part of the operation: boom, boom head, jib, counterweight, hoist rope, hook block, rigging, tag lines, suspended load, possible load swing, crane movement and the maximum working radius in the defined work zone.

Minimum clearance distances while operating near energised power lines

Unknown voltage and encroachment controls

Do not guess. Contact the utility or line owner, confirm nominal voltage and establish the exclusion zone before work. Until confirmed, use the larger conservative clearance required by the applicable site procedure. OSHA permits a 20 ft (6.1 m) option for lines up to 350 kV when its voltage-specific Table A option is not used. For lines over 350 kV to 1,000 kV, the relevant high-voltage provisions use 50 ft (15.2 m) unless the approved voltage-specific process is followed.

If any part could enter the required clearance zone, stop planning, contact the utility, de-energise and visibly ground where practicable, hold a dedicated planning meeting, establish visible barricades or warning lines, use a dedicated spotter where required, use non-conductive tag lines, apply specified range-limiting or warning devices and follow the most restrictive mine, utility, lift-plan or site requirement. A proximity alarm, insulated link or spotter does not permit ignoring minimum clearance.

Minimum clearance while travelling with no load and the boom lowered

This travelling table applies only with no load, the boom lowered sufficiently, a safe route identified, speed controlled and a dedicated spotter used where required. Apply any greater distance required by the mine, utility or site.

Source: OSHA 29 CFR 1926.1407–1926.1411, including Table A and Table T. The electricity supplier, national legislation, mine or site procedure may require greater clearances.

There is no single wind-speed limit suitable for every crane, configuration and suspended load. The maximum permitted speed is the lowest limit specified by the manufacturer, operating manual, load chart, boom or jib configuration, approved lift plan, risk assessment, mine or site procedure, appointed person or lifting supervisor, and the load's wind area and shape.

For general site planning, 9.8 m/s may be used as a conservative stop-work reference only when no lower limit applies. This is approximately 35 km/h, 22 mph or 19 knots; it is not a universal manufacturer limit.

Stop earlier when the manufacturer specifies a lower limit, a jib or personnel lift has stricter limits, a large-area load swings or rotates, gusts exceed sustained wind, boom-head wind exceeds ground readings, visibility deteriorates, or the operator or lift supervisor considers control unsafe. Never transfer a higher limit from another crane or configuration.

Wind acts on the boom, jib, ropes, hook block, rigging and suspended load. Wind pressure rises approximately with the square of wind speed, so doubling wind speed can produce roughly four times the pressure.

Wind and gusts can push a load sideways, increase effective radius, side-load the boom, cause swing or rotation, shock-load rigging, reduce stability, overload components and cause collision, overturning or structural failure. Large sheets, panels, tanks and fabricated structures may be unsafe at lower speeds than compact heavier loads.

Assess both load mass and effective wind-catching area. Use a suitable anemometer at the most representative location, preferably near boom-head height, rather than relying only on a ground-level weather app. Stop whenever positive load control cannot be maintained.

Stop immediately when lightning enters the site's shutdown radius, an alarm activates, thunder is heard, lightning is seen, a storm approaches or the responsible authority issues a stop-work instruction. A raised boom, ropes, load and surrounding ground can conduct dangerous electrical energy.

Follow the mine or site lightning procedure. Land the load safely only if this does not increase exposure, place the crane in its manufacturer-approved safe configuration, keep people away from the crane and move them to a substantial building or enclosed hard-topped vehicle. Do not shelter beneath the crane or nearby isolated structures.

Resume only after the site all-clear. Without a formal system, use a conservative minimum wait of 30 minutes after the last thunder or observed lightning, restarting the period if either recurs.

Include the load or equipment, hook block, headache ball where applicable, slings, shackles, spreader or lifting beam, equaliser beams, lifting frame, suspended chain blocks or lever hoists, rigging hardware, load cells, special attachments and every other item suspended from the hook.

Use verified weights wherever available. Compare the complete total with the manufacturer's rated capacity for the exact radius, boom length and angle, outrigger and counterweight configuration, reeving, operating sector, jib, ground and wind conditions.

A mobile crane has no single fixed lifting capacity. Capacity varies with operating radius, boom length and angle, outrigger extension, counterweight, boom or jib configuration, reeving, operating sector, ground support and wind.

Available capacity normally decreases as radius increases. Use the manufacturer load chart for the exact crane configuration and actual measured radius; never estimate capacity from the crane's maximum advertised tonnage.

Confirm ground capacity and outrigger reactions; identify underground services, voids, trenches, culverts and disturbed ground; level the crane within manufacturer tolerance; extend outriggers to match the selected chart; and use suitable mats, pads or engineered support fully seated on the supporting surface.

Maintain required setbacks from excavations and slopes, monitor for settlement and stop immediately if an outrigger, mat or surface moves. A competent person must verify ground conditions; critical or high-load lifts may require engineering verification.