Truthfully, operating a tower crane can be challenging in the best of weather conditions. Anyone who has worked in the construction industry can tell you that the weather doesn’t always cooperate. This makes it important to know about operating tower cranes in extreme weather.
Weather delays can easily double the amount of time it takes to complete a job. Considering the importance of timelines and scheduling on construction projects, it it almost inevitable that some work will be undertaken in some tough conditions. However, by taking a number of precautionary measures, the risk involved with working in these conditions can be minimized.
Wind
Wind is dangerous, making it the first consideration of safely operating a tower crane in extreme weather. All cranes have a designated maximum wind speed under which they can be safely operated. If winds exceed this speed, the operation of the crane is no longer safe. Wind ratings vary between different cranes, models, and configurations, so it is important to know how windy conditions affect your particular crane or its setup.
If a lift needs to be done in windy conditions, several factors should be considered. Generally, manufacturers will provide guidelines for the maximum wind speed a lift can be done in. If these recommendations are not available, wind speeds of 20 miles per hour are the absolute maximum a lift should be conducted in. You may want to consider delaying the lift if the wind is blowing in the range of 15-20 miles per hour.
Windy conditions change the characteristics of the load, which increases the risk of hoisting the load. If there is a chance the load catches a large gust of wind or the wind speed is too high and makes the load difficult to control, consider delaying the lift.
Another aspect to consider is knowing the direction of the wind. If the building is positioned where the load might encounter side or rear wind, it makes it risky to hoist the load. The load could catch the wind gusts and put an unknown strain on the crane, which could make the lift unsafe based on average conditions laid out in the crane’s chart.
It is also important to remember that wind speed tends to increase with height. As you hoist your lift higher above the ground, it may encounter higher winds. If the lift is being done between two structures, it could be subject to a wind tunnel effect, since wind gusts are funnelled between structures, increasing wind speed.
Cold
According to the Occupational Safety and Health Administration, extremely cold temperatures can also have a negative effect on the performance of tower cranes. Cold can affect many elements of a tower crane, including its hydraulics, rigging devices, and hoists. Cold weather can also reduce the tensile strength of the crane and in extreme cases, cause a catastrophic failure during operation.
At zero degrees Celsius, the cold begins to influence hoists and rigging devices. In sub-zero temperatures, the weather can affect the crane’s hydraulics and maximum load capacity. If a lift is being conducted in the extreme cold, the potential failure of hydraulic systems should be considered, and the maximum load should be reduced by 25 percent.
If the temperature dips to between minus 30 to 40 degrees Celsius, the crane’s maximum load should be reduced by 40 percent and delaying the lift should be considered. If temperatures on site are below minus 40, all lifts should be halted unless they must be used for emergency reasons.
Cold Weather Precautions and Adjustments
If a crane is being operated in a cold climate, you can make several changes for safer operation. Cold weather paint finishes, such as two-part epoxies or hold-dipped galvanized steel are available and can withstand temperatures as low as minus 57. Enclosed track systems, which can be constructed from these materials and made to surround moving parts, can protect the crane’s trolley from the ice buildup that is common at extreme cold temperatures.
The operation of motors can be problematic in sub-zero conditions, but can potentially be solved by using electrified systems, such as conductor bars. Conductor bar sections serve as a cold weather alternative to box track festooning. They are made from galvanized steel and are designed to carry a specific current without overheating. Conductor bar sections can prevent the buildup of ice and other debris on the crane’s joints.
Several crane parts are also available for cold weather-specific operations. Heated control enclosures and gearboxes, arctic duty motors, and special lubricants for low temperatures are just a few examples of equipment that can be utilized in these less-than-ideal conditions.
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