How Are Ship Fenders Used for Berthing?
A ship’s fender system is one of the primary factors affecting a ship’s berthing position. It affects not only the ship’s mechanical and electrical systems but also its berthing position. An effective ship fender system protects the ship from external damage caused by contact between the hull, dock, or dock plate and the ship’s steel plate.
In theory, the speed at which a ship reaches a berth is negligible. Any slight increase in speed results in a significant jump in momentum essentially, the product of mass and speed. For example, a displacement of 10,000 tons multiplied by a speed of 1 knot will have only half the momentum of a ship at a 2-knot berth. With each knot increase in speed, the impact energy doubles, triples, quadruples, and so on.
Ship Fenders
During training exercises, the ship’s speed cannot always be maintained at the minimum due to factors such as tides, wind, irregular drag from tugboats, and engine failure. A good ship fender system can save lives in such emergencies.
Ideally, a ship fender system should be cost-effective, low-maintenance, and highly durable. If replacement is necessary, the material should be locally available.
While a ship is at berth, mariners must consider the energy required for berthing. This energy is determined by a variety of factors, including the ship’s mass or displacement, the ship’s approach speed, the added mass factor (the mass of water moving with the ship and coming to a sudden stop at the point of contact), the yaw factor (the rotational motion generated by the reaction forces when the ship’s bow or stern contacts the berth bulkhead), the berth structure factor (the energy absorbed by the water cushion between the berth wall and the incoming ship), and the ductility factor (the energy absorbed by the ship’s structure and coastal bulkhead deformation).
Boiler
Abnormal energy refers to energy that exceeds the normal berthing energy when berthing under abnormal conditions, such as bad weather, human or technical error, or a combination of all three.
To offset the dynamic forces exerted by the ship on the pier or berth, the quay wall and quay structure must perform work on the ship’s hull.
When the ship’s hull collides with the quay structure, the reaction forces increase dramatically. As a result, both the hull and the berth structure will deflect according to their stiffness.
This is where seawalls installed on the surface come into play. They deflect and significantly reduce berth energy without causing permanent damage to the hull or berth concrete. Of course, these barriers must have a high force absorption capacity and not impact the berth.
Fender Types
The question now becomes: which type of fender should be used for a particular berth?
The choice of a seawall is crucial, as it determines the safety of personnel, cargo, the vessel’s hull, and its equipment. The installation time required for a vessel may depend on the quality of the barrier. Before selecting and installing a seawall system, it is important to consider the statistics of the heaviest and largest vessels that visit the berth.
Old-fashioned hollow wooden fenders have become popular, with various rubber, foam, and inflatable fenders being used as alternatives. Fixed rubber fender systems are available in a variety of styles, including:
- Conical fenders
- Cellular fenders
- Curved fenders
- Cylindrical fenders
- D-shaped fenders
- Leg fenders
- Quarter rubber fenders
- Pancake rubber fenders
Foam fenders contain chemicals such as ethylene vinyl acetate (EVA), which provide buoyancy and low maintenance. Polyurethane or a flexible polymer spray-on coating is applied to these fenders, creating a nearly completely abrasion-resistant outer layer.
Pneumatic fenders are inflatable, floating fenders that can be installed on dock walls or vessel hulls as needed. There are four types of air fenders:
- Rope fenders
- Ribbed fenders
- Rope net fenders
- Type fenders and frame net fenders.
Fenders are an integral part of a vessel’s safety system, reducing impacts on the berth or hull. A wide variety of marine fenders is available on the market, suitable for a variety of applications. They are used not only on commercial vessels but also on ships, yachts, and other floating vessels.
Correctly selecting an offshore tunnel boring machine to optimize cost and efficiency requires experience and skills, not to mention a thorough understanding of existing varieties, requirements, and relevant theory.
In ancient times, the “Captain” was an indispensable member of the bridge team. The title “Captain” was given to outstanding sailors whose primary responsibility was to steer the ship in accordance with the instructions of the captain and officers. Captains would take turns steering the ship throughout the day while underway. This practice continued into the era of automated primary navigation. With the invention of revolutionary autopilot systems, the importance of the “Captain” role virtually disappeared. Automatic steering and rudder control systems were introduced on commercial ships in the early 1920s.
Autopilot systems are considered one of the most advanced and technologically sophisticated navigation tools on board. Autopilot systems synchronize with the gyrocompass and guide the manually entered course based on the gyro’s direction. The autopilot system guides the manually entered course by controlling the steering gear to rotate the rudder in the desired direction.
Furthermore, modern autopilot systems can synchronize with the Electronic Chart Dispatching Information System (ECDIS), enabling them to follow the course specified in the voyage plan. This feature eliminates the need for manual course changes, as the system automatically follows the path and makes adjustments based on the flight plan.
Autopilot systems are undoubtedly an advantage in modern sailing. However, overreliance on these systems and a lack of understanding of their effectiveness and limitations have led to many maritime accidents. This is often due to operators failing to thoroughly understand the equipment’s basic specifications.
The following briefly outlines ten key points to consider when operating an autopilot system on board a vessel to ensure safe and smooth sailing.
1. Roll Rate and Rudder Limits
The roll mode is the most important control method in the autopilot system. The system uses the selected roll mode to change heading. Users can enter limits for these modes, as follows:
a. Roll Rate
This is the most common roll mode. In this method, the user can set a roll rate value between 1 and 300 degrees (depending on the model). When turning, the rudder will move as needed to achieve the desired roll rate, but must not exceed the specified value. The operator must consider the vessel’s maneuvering characteristics and determine a safe value that is appropriate for the vessel.
B. Rudder Limit
The rudder limit method allows the user to specify a value from 1 degree to the maximum rudder angle. In this method, the rudder does not exceed specified limits during course changes. Again, the vessel’s maneuvering characteristics must be considered when selecting rudder limits.
Modern systems also allow for radius turns. In this method, the user enters the turn radius in nautical miles.
2. Steering Gear Pump
The steering gear pump pumps hydraulic fluid to operate the steering gear unit (RAM), thereby moving the rudder in the desired direction. This means that the more pumps used, the faster the rudder can be moved. The number of pumps available depends on the steering gear arrangement.
The officer of the watch must be vigilant and use the pumps appropriately.
If the autopilot system is operating in an area with heavy traffic and requiring sudden and rapid changes, the maximum number of steering gear pumps must be enabled.
When operating in open ocean and high seas with less traffic, pump operation should be minimized.
3. Course Deviation Alarm
The course deviation alarm notifies the operator of any deviation between the specified course and the vessel’s actual course. The user can manually set the desired course in degrees; if the specified deviation is exceeded, the system will sound an audible alarm.
However, the user must continuously monitor course changes. In some cases, when the gyrocompass deviates from the course, the autopilot will follow the compass without sounding an alarm.
4. Manual Mode
The system’s steering control can be divided into two modes: automatic and manual. The system allows the vessel to be steered manually or automatically by switching the control.
In manual mode, the vessel can be steered manually using either a following rudder or a non-following emergency rudder.
Manual steering is used for maneuvering and navigating the vessel in restricted waters, waterways, and heavy traffic areas.
When using a non-following emergency rudder, the rudder moves in the desired direction, but not at a specific angle. This is suitable for emergencies.
The user must be familiar with the procedure for switching between automatic and manual modes.
5. Traffic Congestion
The autopilot system is not recommended for use in high-traffic areas, narrow waterways, areas with traffic separation systems, and other confined waters. The autopilot system may not be able to effectively steer the vessel automatically when operating in areas requiring rapid course changes and maneuvers to avoid collisions or near-collision situations. If the autopilot system is used in these situations, all steering gear pumps must be engaged to increase rudder response.
6. Speed
The system operates at low speeds. It is not recommended to use the autopilot system when maneuvering or sailing at very low speeds.
The system allows the user to synchronize with the speedometer to receive information about the vessel’s speed. It is recommended that the user check the speedometer regularly, as any errors will be reflected in the autopilot system.
The system also allows the user to manually enter the speed. Therefore, it is important to set the speed as close as possible to the vessel’s actual speed.
7. Weather Conditions
Bad weather and adverse sea conditions can negatively affect the performance of the autopilot system. Uncontrolled yaw can cause excessive rudder movement. Modern autopilot systems are equipped with a weather control option that automatically adjusts settings based on changing weather and sea conditions. Users can also manually select specific values.
8. Gyrocompass
The autopilot system’s functionality relies on the gyrocompass. Any error or fluctuation in the gyrocompass’s heading will result in a corresponding change in the intended heading. In the worst-case scenario, if the gyrocompass fails, the system will lose heading and be unable to maintain the intended heading.
In the event of an emergency, power outage, or gyrocompass failure, the system must immediately switch to manual mode and use the rudder to determine heading using the magnetic compass.
9. Important Alarms and Signals
In addition to the deviation alarm, the autopilot system must include the following features:
a. Failure or low-battery alarm: This alarm sounds when the autopilot or its monitoring system fails or loses power.
b. Sensor Status Monitoring: If any sensor in the autopilot system becomes unresponsive, the monitoring system must sound an audible alarm.
c. Bearing Monitor: If the vessel is required to be equipped with two independent compasses, a bearing monitor must be provided to track the current bearing information using an independent source. If the bearing information deviates from the second bearing source by more than the specified limits, an audible and visual alarm must sound. The device must also clearly indicate the current bearing source.
10. Important Limitation:
The autopilot system must ensure that the intended course cannot be altered by intentional intervention by shipboard personnel, and the course control system must be capable of altering the course to the intended course and not beyond its intended position.
As previously stated, autopilot systems are an undeniable advantage of modern navigation. Crew members are responsible for ensuring they fully understand the equipment, its functions, and its controls to use it correctly and effectively.
While autopilot systems vary by vessel model, their operating principles and features are the same. Deck crew members using the equipment are strongly advised to read the manufacturer’s instruction manual for a full understanding.
