The challenges and risks of wind gusts for dockside operations
Ports that handle large amounts of cargo face a unique challenge. A port becomes more competitive by being able to load and unload more tonnes of cargo per day and this can be accomplished in two ways: having more container cranes and having a higher loading capacity per crane.
However, these cranes must operate close to the sea, and wind behaviour is different from what can be expected in a city or field.
The competitivity of a port is strongly dependent on its safety record – a severe accident can damage reputation, leading to the loss of important clients.
Ports operation managers must constantly assess the weather and take informed decisions. Ideally, equipment should operate under any conditions considered safe in order to minimise weather-related downtime. Suspending operations can be very disruptive for harbour activity.
Main Challenges of Marine Weather Monitoring
- Ports and other marine locations are exposed to unpredictable weather hazards.
- Ship maneuvering becomes more difficult if the sea is agitated. Heavy rainfall and fog limit visibility and sudden gusts of wind can destabilise cargo while lifted by a crane.
- Since there are less obstacles in marine locations, wind speed increases more sharply with respect to altitude.
- A crane in a marine location can expect higher wind speeds than a crane of similar height operating far from the sea.
The weather is a risk factor for any outdoor operation but docks are a special case due to their proximity with the sea.
It is important to note that wind loads do not increase in direct proportion to wind speed – each time wind speed is doubled, loads become 4 times higher. For example, the wind load at 20 mph is 4 times higher than the load at 10 mph, and the load at 40 mph is 16 times higher.
Atmospheric pressure is a weather metric that receives little attention in land-based applications but it becomes critical in marine environments. Unlike the land, the sea responds to atmospheric pressure, and tide levels can increase or decrease accordingly.
Although the weather is impossible to predict with full accuracy, ports must schedule their operations effectively due to their high workload. Modern meteorology can predict harsh weather to a degree, but safe operation is only possible when scheduling is complemented with live weather data.
- Live data is useful for day-to-day decisions during harbour operations.
- As more data is gathered for a specific site, predictions can become more reliable.
- Historical data is useful for dock infrastructure design, local weather modelling, and risk assessment.
- Geographic, marine and weather conditions are unique for each port.
The Risks of Harbour Crane Operation
Harbour crane manufacturers consider the increased wind speed near the sea when designing their machinery, but this does not mean dock operators can be careless. Strong winds can cause severe accidents, even if the crane itself is capable of withstanding them. The following are some examples:
- A strong wind can destabilise a container being lifted and the crane operator may be unable to control it. These loads weight many tonnes and can cause severe damage if they hit equipment or structures.
- The risk of dropping heavy cargo a ship is also present. If this happens, the ship will likely suffer significant damage or it may even sink.
- Consider that wind also cause drag forces on ships. Accident risks are higher when a container and a ship are moving drastically with respect to each other.
- Seaports also tend to have plenty of equipment and cargo in close proximity to maximise the usefulness of the space available, and collateral damage is likely.
Just like with land-based cranes, wind monitoring plays a fundamental role in harbour crane safety. Weather forecasts only provide general wind data and they cannot predict short-term events such as gusts and turbulence. Human perception is also unreliable when dealing with the wind especially under a constant marine breeze. Harbour cranes should be equipped with accurate wind monitoring equipment to obtain a clear snapshot of wind conditions in real time. The device must also offer connectivity, ensuring that port personnel are informed when the wind is unsuitable for lifting operations.
WINDCRANE is a product and data service designed and built by Logic Energy Ltd, Scotland, United Kingdom. www.windcrane.com