How Do Ships Survive Storms?
Ships face a variety of challenges arising from varying ocean conditions. These challenges include weather changes, impacts from seawater, navigational issues, and geographical constraints. However, the biggest question surrounding their survival in storms is how they survive.
Due to their strategic location, the tropics are the most storm-prone region. An average of 75 to 85 storms occurs there each year. However, 60% of these storms do not cause any disturbance to land.
These storms vary in size, intensity, and nature. Small storms dissipate within 24 to 48 hours, while larger ones can persist for over a week! Therefore, heavy traffic in storm zones requires ships to be agile.
This includes the ability to maneuver safely, practice good seamanship, and employ modern communication technology. Fewer than 200 ships of all sizes are involved in marine accidents and capsizes each year. This is a significant achievement for a fleet of over 80,000 ships of standard size and above.
This article provides an in-depth look at how ships withstand storms while navigating the oceans. It also examines the structural and propulsion factors that enable ships to meet these challenges.
Storm Behavior Patterns
Sea storms form for many reasons, but the primary factor is pressure differences. The ocean has different surface and overall temperatures from land. This behavior creates air currents that lead to two different types of storms:
- Hurricanes
- Typhoons
- Cyclones
As sea surface temperatures slowly rise, the air also warms. This creates air currents, causing lighter air to move upward, resulting in lower air pressure around the sea surface.
As a result, air near the sea surface flows inward, forming a ring-shaped area. This low-pressure area creates a violent circular movement of air and water, ultimately forming a cyclone. Cyclones are often more severe in coastal areas. For example, Port Hedland is closed for four months each year due to cyclones.
The average speed of the circulation ranges from 20 to 150 miles per hour. This means that storm classification helps meteorologists warn ships of impending dangers.
Tropical Cyclones
After a tropical cyclone passes, winds in the area rapidly weaken due to sinking clouds. This causes air currents to flow downward from a relatively high altitude. As a result, ships can encounter offshore cyclones with winds as high as 150 miles per hour.
Furthermore, the average speed of these destructive forces exceeds 80 miles per hour. This makes the entire surrounding area vulnerable to strong winds and heavy rain. Such winds can bring large waves and severe turbulence to ships.
Ship Survival in Storms: Navigational Factors
With advances in marine technology, marine accidents caused by severe weather have decreased year by year. In 2019, approximately 16 ships reported severe weather resulting in irreparable damage.
Thus, recent technological developments have significantly contributed to the survival of ships at sea during storms.
The Evolution of Electronic Chart Display and Information Systems (ECDIS)
The introduction of the Electronic Chart Display and Information System (ECDIS) in the early 21st century was the most significant advancement in ship survival. Despite the numerous shortcomings of paper charts, ECDIS remains popular.
Although this display system lacks dynamic functionality, it allows for the flexible use of other tools. Accurate charts and patterns of nearby vessel behavior greatly benefit navigation teams, giving them a significant advantage when changing navigational patterns are necessary.
Weather Guidance
Although the Electronic Chart Display and Information System (ECDIS) is electronic and offers many advantages, it is still just a map. It provides mariners with the necessary information to determine a safe navigation route.
This crucial information is provided by both private and public weather routing services. These services primarily connect via three systems:
- Communications satellites
- Navigation satellites
- Remote sensing satellites
Every shipping company connects its ships to high-quality weather routing services. When a ship sets sail, it receives information about its next destination. The second-in-command then plans a suitable route to reach the destination within safety regulations.
As the weather changes, weather routing services provide the latest information on storms along the route. This allows the ship to completely change course or adjust its speed accordingly.
Local Weather Alerts
These alerts, typically in the form of coastal warnings or marine warnings, are issued for ships navigating their coastal areas. Areas such as the Cape of Good Hope and the waters off the coast of Gujarat, India, have experienced concerning weather fluctuations. This requires local monitoring to keep ships informed hourly.
Dynamic response plays a significant role in how ships react to storms. Therefore, ships rely heavily on these local alerts to inform crews of potential dangers.
Most of these alerts are issued via local communication channels. Any vessel intending to enter their waters notifies them in advance. Local authorities then monitor their positions and, if necessary, issue simultaneous warnings.
In severe weather conditions, these alerts can also delay ship berthing or cargo operations. For example, the Bombay High is unsuitable for container operations in strong winds (75 mph or higher).
Satellite Communications and GPS
Of all navigational factors, satellite tracking systems and GPS are the largest and most common. These systems ensure that ships are not sailing blindly and that reporting systems are not informed of the vessel’s status.
A robust satellite communications network also ensures that modern ships have constant access to information. This provides the captain with an additional advantage, enabling free communication and ensuring safe navigation.
Satellite imagery is also a crucial factor for both passenger and cargo ships. Combined with sailing experience, it helps the crew identify dangerous areas. This allows the ship to determine a sufficiently safe route even when a storm is unavoidable.
Preparing for Storms: Ship Design Factors
In addition to navigation safety standards, changes in ship design also influence a ship’s survivability in storms. Both the development of double-hull vessels in the 1990s and the evolving SOLAS guidelines play a unique role.
At the same time, some design factors outperform others in enhancing ship survivability. This is particularly useful when encountering heavy weather or storms.
Keeping the Bow Ahead in a Storm
The bow is the most heavily reinforced member in a ship. Thanks to an additional web structure that maintains structural integrity, the spacing between each frame is closer. Furthermore, the forward collision bulkhead provides an additional safety net against direct contact.
Conversely, withstanding collisions from the ship’s side (port or starboard) is crucial. With variations in center height, these collisions can push the ship beyond its stable trim angle. Therefore, if high waves and headwinds occur, the ship’s roll will be irreversible.
Transverse beams
The use of transverse beams reinforces critical ship components, increasing the strength of cargo hatches, fuel tanks, and other hollow components. Transverse beams also reduce plate bending and moments.
Thus, the ship maintains its flexibility and strength during storms. Furthermore, this design is far superior to conventional rigid, dent-prone designs.
Watertight Safety
The safety of a ship is paramount in the most severe flooding situations. Accidents such as the sinking of the Derbyshire in the early 1980s provide a stark example.
Extending watertight bulkheads to the upper decks divides the ship into compartments. This means that even if water enters the hull due to damage, the ship maintains stability. Furthermore, the forward hold, hatches, and head compartments are all designed to be non-reversible.
This design provides additional protection, preventing water from entering the ship even in the event of a severe collision. This robust watertight safety explains how ships can survive storms even after sustaining significant damage.
Steering Gear Design
A ship’s steering capability ensures safe and reliable operation in all sailing conditions. During severe storms, a ship requires good maneuverability to minimize impact forces. Steering also helps ensure the ship safely navigates rough seas.
Every ocean-going vessel, whether passenger or cargo, is equipped with a steering safety system. This system utilizes one or more of the following configurations:
- Single Failure Standard
- Emergency Backup Steering System
- 100% Redundancy
Safe Steering
This system ensures that the steering system always has a backup option for maximum steering capability. This system allows for safe maneuvering under various load and weather conditions while maintaining the ship’s maneuverability. Under no circumstances will the system cause the ship to lose its steering capability during a storm, thus preventing disaster.
Good Sailing Practices for Storm Survival
Despite the superior structural and technical performance of ships, sinking in adverse sea conditions remains a common occurrence. The primary cause of these accidents is poor sailing practices or navigation management. Despite various systems and preventative measures, the human factor remains crucial.
Therefore, one of the keys to a ship’s storm survival is the crew’s skills. This includes seamanship, maintenance, cleanliness, and more.
Cleanliness Standards
Over 1,200 major and minor incidents occur each year due to poor navigation management. This includes negligence on deck and in the engine room while the ship is at anchor.
Even if a ship avoids a storm at a considerable distance, a storm always portends severe weather. Some tropical cyclones have a radius of 160 kilometers or more. With ships constantly rolling and listing, safety standards are more important than ever.
Secure vents, goosenecks, hatch covers, and any other openings that could compromise their seals. Containers should be regularly lashed to prevent their relative position from shifting. This also prevents the ship from listing unduly, which could exacerbate weather problems.
Securing spare parts or heavy machinery can prevent accidents within the vessel. This prevents falls or dents that could cause personal injury or structural damage. For example, improperly securing heavy passenger vessels could lead to accidents or damage to the engine room structure.
Maritime Awareness
Shipowners typically adopt a counterclockwise navigation strategy when navigating storms. This also involves maintaining a course away from the eye of the storm as much as possible. Surfing, or sailing directly into the wind, is a critical aspect of watchkeeping.
Shipkeeping standards play a vital role in all aspects of shipboard watchkeeping. This includes the ability of the captain and chief mate to demonstrate their professional skills.
Propulsion and Machinery Maintenance
Loss of propulsion under test conditions is the single greatest contributing factor to a vessel capsizing. Furthermore, accidents caused by loss of power or propulsion offer no second chance to recover.
Predictive maintenance standards for machinery ensure that such incidents are extremely rare. These standards cover regular cleaning of filters and regular maintenance of generators for emergency situations. Emergency power supplies also require regular inspections to ensure they are functioning properly under test conditions.
Reserving critical components, such as backwash filters, may seem simple, but their impact is profound.
Good engineering practices include avoiding fuel tank changes before severe weather occurs. This also prevents the accumulation of empty tanks or low-level suction.
Shipboard Storms
A ship’s ability to withstand storms depends on many factors. However, with 726 serious incidents occurring in 2020, there is still significant room for improvement. Human error caused by global environmental change also contributes to losses.
Climate change, including global warming, is making storms more unpredictable. This makes dynamic response capabilities more important than ever.
As ship size and capacity grow, so too does maneuvering technology. Consequently, modern maritime intervention, more effective than ever before, provides a safe haven for future maritime safety.
