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Weathering Heights- Tower Cranes and Wind

Weathering Heights- Tower Cranes and Wind

Crane Safe Wind Speed

Weather can be a dangerous factor in construction. Conditions such as high winds pose a significant threat to cranes and other large machines and equipment. Tower cranes, especially, face a serious risk when heavy winds come. There have been several cases in which tower cranes have collapsed, or been damaged in some other way because of high winds.

Recently, more than three tower cranes collapsed in London alone. In one of these accidents, the jib of a crane collapsed onto a roof, putting the residents in danger and causing the building to be evacuated. Situations like these are common, raising the question: How do manufacturers design these tower cranes to minimize risk, and how can users prepare for high winds?

Following the collapse of these three tower cranes in the UK, the Health and Safety Executive (HSE) issued a safety alert to tower crane users. After looking into the situation further, HSE discovered that some tower crane users were not releasing the slew brake, or were not placing the jib at the correct out-of-service radius when leaving cranes unattended. These two mistakes may prevent the cranes from being able to “weathervane” freely in high winds. This could potentially result in the collapse of the jib or the whole crane.

HSE used this information to remind tower crane operators that when they are left unattended, luffing jib tower cranes must be in free slew, with the jib at a safe out-of-service radius. When this is done and cranes are prepared correctly, unattended or out-of-service cranes are designed to withstand a maximum ‘out of service’ wind speed of up to 100 mph.

While any machine can be affected by weather and high winds, tower cranes need to be tended and prepared properly in order to withstand these conditions. Learn about your equipment, and become properly trained in safety procedures.

OSHA Requirements for Crane and Aerial Lift Wind Speeds

Project managers and site supervisors must decide whether a crane or lift can be used safely when the weather changes or if the work should stop. Manufacturers should provide maximum wind speed ratings to operators and provide additional guidelines for how and when to use a crane.

Guidelines and regulations for windy situations are provided by the Occupational Safety and Health Administration (OSHA). OSHA wind speed regulations must be adhered to safeguard property and maintain workplace safety. Managers and supervisors must also consult general safety guidelines provided by trade groups and the direction of the wind. Winds coming from the side or front of the cane will affect the vehicle’s stability differently than winds coming from behind.

One of The most significant wind restrictions to be aware of is this one, according to the OSHA aerial lift wind speed section: “When wind speed (sustained or gusts) exceeds 20 mph at the personnel platform, a qualified person must determine if, in light of the wind conditions, it is not safe to lift personnel. If it is not, the lifting operation must not begin (or, if already in progress, must be terminated).”

Safe Wind Speed to Operate Cranes

Wind doesn’t discriminate based on size. Operators must be mindful of how the wind may impact their hoists, whether they drive small carry decks or the big all-terrain and crawler cranes. The impact of the wind on the lifted load, booms, and jibs can still have disastrous effects on the machinery if it is not properly taken into account.

Wind speed indicators on more recent crane operator cabs alert the operators to the present wind conditions. Without these safety operator aids, crane operators must rely on outside sources to provide crucial information. Operators, safety managers, and project managers can plan the day by looking at weather information in advance.

Mobile Crane Operations

All cranes use load charts that are set up without consideration for wind. Due to this, manufacturers also include wind limits when the crane is in use, such as the maximum wind gusts before the crane has to stop operating.

Generally speaking, cranes should proceed with caution when winds are between 0-20 mph. Depending on the crane model and boom length, the capacity of the crane is reduced when wind speeds range from 20 to 39 mph. When wind speeds surpass 40 mph, all crane operations must stop, and the boom retracted and lowered to horizontal. Windy weather can particularly impact cranes when:

  • A wide surface on the object being lifted could catch the wind.
  • With higher lifts, wind gusts increase with elevation.
  • If the wind is coming from behind the crane, it will affect the lift’s radius.
  • The boom’s verticality will be affected by the wind from the side.
  • Be mindful of “wind tunnel” effects, such as swirling and increased wind speeds, when working between tall structures.
  • Wind-blown dust may make it difficult for a crane operator to see the lift or signal person on the ground.
  • Snow, heavy rain, or fog can also cause hazardous circumstances.

Handling High Winds

If winds are less than 20 mph, normal lifting operations should proceed as scheduled. It’s always important to consider reducing the lift’s angle, load weight, or height if that’s a possibility. Lifts should be delayed if high winds are likely. Timelines will be affected, of course, but a day missed is far preferable to lost supplies, broken equipment, or worker injuries and deaths. Safety managers should have a plan in place in case of high winds, such as putting the load in a secure location, folding down the boom or jib, and stopping the lift until the weather clears.

Safety Hazards

In the United States, there are about 44 crane-related deaths yearly. One of the top four leading causes of crane operator fatalities is crane collapse. Given the size of most cranes and the large loads they transport, the effects of a crane collapse can be devastating. Frequently, crane collapses result in deaths or severe injuries, including:

  • Traumatic brain injuries
  • Spinal cord damage
  • Amputations

Risk Management in Crane Safety

Harsh weather increases the risk of lifting operations, and safety managers need to take action to avoid accidents. The first step in risk management is to always be aware of the exact wind conditions. Operators and project managers determine whether a lift can be completed safely based on crane specifications.

  • Crane manufacturers need to provide loading tables, derating factors, and maximum wind speeds. These specifications vary depending on the type of load.
  • When this information is unavailable, contractors can rely on general safety protocols established by construction associations.
  • Wind direction is also important because it influences how the crane is loaded. Side winds, for example, have different effects than the wind blowing from behind the crane.
  • Consider turbulence intensity because it adds loads even when the average wind speed remains constant.

Manufacturers should give accurate loading information that is updated with wind speed data when safety operators check the weather onsite to make crane operations safer. Weather forecasts and historical data can be used to plan activities while monitoring the weather and wind speed during a lift enabling quick judgments. Crane derating data from the manufacturer is useful for avoiding overloading, and accurate instruments can alert construction managers when dangerous winds are approaching.

Preparing for Bad Weather

While the wind may seem strong on the ground, conditions 100 feet in the air can be very different. The Severe Weather Guidelines for cranes and riggers were created by the Specialized Carriers & Riggers Association (SC&RA) to provide instructions for what to do in the worst weather conditions, such as ice, snow, severe winds, thunderstorms, and tornadoes. These guidelines address pre-inspections before, during, and after a lift, and should be viewed as an addition to what is already in place rather than a replacement for the customary pre-work preparations.

How Wind Speed Affects Cranes

Cranes, like any structure, have a loading limit. As the wind’s speed rises, the force it produces grows, and the crane must use some of its carrying capacity to withstand it. It is important to have precise information for each crane type when working on a project, and wind conditions should be assessed for each crane involved.

A site with many cranes and only one weather station does not provide enough certainty. If the loading information is missing, the crane manufacturers should be contacted. Everyone using the hoist, particularly the operator, should have access to this information. Contractors can adhere to the following general safety precautions if the lift operations cannot be delayed and particular crane load information is not available:

The most important details in this text are that if the wind speed exceeds 20 mph, the crane should be stopped. Management and designated personnel should reevaluate operations if the wind speed increases dangerously. The crane operator may opt to stop using the crane at lower wind speeds due to the type of cargo being lifted or the difficulty of controlling the crane under wind pressure.

Wind speed should be gauged at each crane’s highest point because it tends to rise with height. A measurement taken at ground level is of limited use since it does not account for the wind exposure that the crane is subject to.

Safe Crane and Lifters Operations

Even a slight change in the weather can be hazardous when working at extreme heights. To cope with these safety issues, OSHA set wind speed restrictions for aerial lifts. Operators may put their lives in danger if the rules are disregarded. It’s crucial to take quick action while the weather is changing because it’s impossible to predict how the wind might affect an operator’s shift. Companies must place a high priority on thorough safety training so that lift operators are aware of what to do in case of heavy winds.

Inclement weather can take many different shapes. In general, crane and lift operators are aware that using a lift in rain, sleet, or snow is not advised. Despite severe winds rendering the crane or lift unstable and causing tipovers, people may still use the equipment in windy weather.

At all workplaces with cranes or lifts, OSHA wind speed requirements must be known and observed. Crane and lift operators will then be aware to refrain from using a lift if the wind becomes too strong to handle. Also, they will be able to monitor wind speed and identify when and if a jobsite becomes risky.

It is essential that every member of the team and crew has received safety training and is aware of their employer’s safety policy. There should be a safety plan in place for emergencies and accidents at every workplace, including policies for dealing with risks, injuries, and equipment or machine failure. PPE and fall protection are two excellent components of any safety plan.

Check out our safety training classes if you’d like to learn more about wind monitoring and other safety procedures for construction sites. We offer a variety of crane trainings, including: