What can house 1,000 passengers, a boatload of cargo, and 850 vehicles? You guessed it. A ferry.
The UK Government’s Department of Transport in their 2016 Provisional Sea Transport Report stated that the number of international short sea passengers was estimated at 20.0 million people in that year. Norway also utilizes ferries in a big way. Until the completion of the first underwater tube-shaped floating tunnel, the only way to navigate Norway’s fjords is via ferries.
With that many people utilizing the form of transport, it is in the best interest of the engineering companies that run them to regularly perform maintenance on the ships. Extending the lifetime of a ferry is a three week slog, that guarantees the ferry another ten years of operation.
A little South of Norway, a battalion of ferries operate in the North Sea, enabling transport between a number of countries including the United Kingdom, France, Germany and Belgium. One of the ferries that should be up for its next maintenance operation in 2022 is the Pride of Bruges. The ferry consists of 32,000 tonnes of steel, 7 football field sized decks, with 4 engines which burn two and a half thousand litres of fuel an hour. It was renovated in 2012.
The operation involving exterior and interior maintenance takes an army to complete. The Newcastle engineering team consists of 120 engineers who work on the boat, examining over 1,000 separate parts.
The most critical parts of the ferries which require attention are underwater; if it is not docked, the boat cannot be repaired, maintained or renovated.
Thus, the first challenge is getting a mammoth ferry into the ferry lock. The lock is flooded with 133 million litres of water that allows the ferry to be pushed into the lock. After that, the water is emptied out so that the ferry can be accessed and assessed on dry land. Most of the engineering works are below the water line.
Once the hull of the ferry is accessible to the engineers, one of the first things investigated are the ballast tanks. Ballast tanks are compartments within a floating structure which take water in, in order to ensure stable buoyancy. The tanks are emptied and cleaned so that the overhauling of them can begin. Corrosion proofing ensues within the inner steelworks.
When the ferry is functional, water is pumped in and out of the ballast tanks, based on the buoyancy required. Engineers explain that saltwater and freshwater have different buoyancies. There is a measurement ruler on the side of the boat that suggests water levels for the different buoyancies.
Another crucial element of the ferry that must be checked, over and above everything else, are the retractable fins, known as stabilizers. They keep the boat from rocking back and forth and giving the crew sea sickness. Actuators ensure that they are perfectly synchronized on either side of the ship.
The most common of all ferry maintenance is performed on the steel boat itself. Seawater corrodes the steel, thus it needs to be constantly weather proofed to avoid rust and wear. To avoid seawater from eroding to the point of catastrophic failure sacrificial anodes are fitted to the hull - they take the brunt of the seawater damage so that the steel beneath it doesn’t corrode as quickly.
The ship’s two propellers are also polished. They are closely studied to detect cracks and other surface imperfections; fractures must be fixed. Propellers suffer from what is known as cavitation erosion. This occurs because of the implosion of water bubbles around the propellers during the ship’s operation. It has the ability to render propellers useless. Thus, polishing them ensures a longer lifetime.
Finally, rudders are checked to ensure that the boat can be maneuverered back into the sea. Controlled by hydraulic actuators, the rudders are controlled by the captain housed inside the bridge.
Aside from maintenance to the exterior, the complex technological systems responsible for, among other critical jobs, steering the ship, require trouble shooting and checking. These computers are vital to the smooth running of a ferry.
Global positioning systems are also being installed in ferries to make sure that captains are aware of exactly where they are going and to monitor other boats that are filling up shipping lanes.
Further inside the ship, the replacing of steel floors occur where the car deck is positioned. Wear and tear of the steel flooring occurs due to the tonnes of cars that weigh the steel down during its lifetime. A new layer of steel is placed atop the old one.
Image of the boat traffic between the English Channel.
In the engine room, refurbished barrel-sized pistons are positioned to fire away once the ferry is ready for action again. The pistons cost £15,000 per piston. 30 pistons are required for a ferry the size of the Pride of Bruges.
These are just some of the engineering challenges involved when maintaining ferries. On completion they are carefully moved from their locks back into the ocean. After their three weeks in dry dock they should remain in good shape for another decade. These maintenance visits keeps the teams of repairers on their toes; delays are extraordinarily costly.
"Engineering Giants - 3. Ferry Strip-Down." BBC IPlayer. BBC. Web. 10 July 2017