Interventions that are often handled on an emergency basis, to the stress and disappointment of the captain, shipowner, and guests, can be easily avoided through periodic and careful maintenance of all on-board equipment
“Fin che la barca va, lasciala andare” (that is, if it ain’t broke, don’t fix it). It was 1971, when a young Orietta Berti hummed this tune that has now become an evergreen of Italian song. We borrow it today, turning the lighthearted exhortation into a rather serious question. Let’s talk about an important topic, a combination that is, in some ways, underestimated: yachts and maintenance.
Every year, at the end of the season, hundreds of yachts return to yards around the world and, depending on their needs, undergo various refit or retrofit activities. In addition to routine maintenance of technical equipment and the more demanding class renovations, there is major work involving sometimes the aesthetics of the hull, interiors, and furnishings, and sometimes technological equipment. Then there are retrofits that change the ship’s propulsion system; conversion of commercial vessels to pleasure vessels is also a popular trend, especially in Northern Europe.
Let us stop, for the moment, at just the concept of maintenance. The list of routine maintenance work that the shipyard carries out during the winter, using one or more project managers and specialized technicians, is a set of activities to which, often, is added the need for solutions to problems that have arisen during the season: premature wear and tear, breakage of mechanical components, unwanted noise and vibrations in areas of the ship where there really shouldn’t be any. And it is often the heart of the ship, the engine room, where all this originates.
Chief Engineers, Captains, Superintendents, technicians having a clear understanding of the overall condition of the yacht and technical apparatus, evidently prioritize the maintenance activities required by regulations: engine, inverter, generator, batteries, air conditioning. A yacht is made up of hundreds of systems, each composed of subsystems that are minor in size and complexity, but not secondary in function.
If it is true that the main propulsion line equipment ensures performance and performance in terms of seaworthiness and speed, what operates so quietly that the owner does not notice that he has an entire engine room right under his feet? It is an entire system that ensures such a level of comfort-in terms of perceived noise or vibration on board-that a yacht can be compared to a luxury villa, with only one small difference: views of breathtaking panoramas, sunrises and sunsets in the middle of an ocean.
Knowledge of these components is the prerogative almost exclusively of construction site technicians and subject matter experts, ‘the vibro-acoustics,’ engineers, who in the design phase select them as the interface between the propulsion line components and the ship’s structures: they are to act as a filter and barrier against sources that would irreparably disrupt our wonderful cruise on board.
Of these components, those who experience the boat and care for it during its lifetime rarely know its existence, function, and life cycle. Ignored, left to age in neglect, their presence is only noticed when something goes wrong. We are talking about the on-board elastic support and transmission system: elastic joints, anti-vibration mounts and shaftline joints have a rubber heart, therefore, a life. We told you the secrets of these in an installment column some time ago: we explained their function and how they are designed to work together, in synergy so that, acting as a system, they operate according to the comfort goals established by design. This time we tell you what happens when they are ignored, and, more importantly, what to do to not forget them.
The anti-vibration mounts
Bahamas, March 2020, full COVID emergency – MY 73M
The captain of a 73-meter charter vessel contacts Vulkan’s After Sales department. The problem is on a line upstream of the propeller where a shaftline coupling, Propflex T, is installed, which contains a thrust bearing module designed to discharge the reaction force from the propeller onto the ship’s structure. The captain is very concerned: he complains of temperatures reaching over 200 °C inside the bearing. Intervention on board by a Vulkan technician is hampered by the sanitary situation, and the captain has no access to any shipyard in the area. After days of uncertainty, he is forced to take the ship for disassembly of the module, supported by a single line in operation, all the way to the Mediterranean, to the only shipyard that has become available for the operation.
Propflex T bearing detail
The unit is disassembled, landed and sent to the plant so that Vulkan technicians can check its condition and condition. The thrust bearing module consists of roller bearings, lubricated with a specific grease that wears out in normal operation. Therefore, over the years, it needs to be restored on a regular basis. During Propflex T overhaul, heavy wear becomes evident on the bearing washers and cylindrical rollers due to the very high temperatures reached, caused by the near absence of the lubricant.
Propflex T installed onboard
Simple maintenance of the Propflex T performed at the appropriate time would have cost only a few tens of euros. Instead, delaying it until the emergency cost tens of thousands of euros to service, including site costs, disassembly, complete overhaul, and new installation of the module, very little, however, when compared to the lost revenue caused by the unexpected ship grounding.
A very risky Atlantic crossing with only one line, costs for hauling in the shipyard and unplanned overhaul of the entire module, and forgoing the many charters already scheduled were among the most negative aspects of this misadventure.
Greece, summer 2021 – MY 27M
The 27-meter MY has undergone a very long retrofit that has radically transformed her. The owner, after a long time and much anticipation, is finally enjoying a vacation aboard his completely renovated yacht. A few days into the cruise, the captain contacts Vulkan’s After Sales team complaining of a broken elastic joint, a Vulkardan E specifically, on the starboard line. An emergency intervention is arranged to check the condition of the joint and the causes that led to the rupture.
Joints with cracked elastic parts
The causes of a broken coupling can be any number of things, the first check that is conducted is related to the alignment of the two main components of the shaft line: motor and inverter. The reason for the rupture, downstream of the surveys, is soon discovered, misalignment, due to improper installation of the anti-vibration mounts. The result was ruined sailing with the shipowner furious, incalculable ’emotional’ damage, waiting time for procurement of spare parts, service intervention in full emergency, high costs for express shipments of parts and equipment for replacement.
Italy, May 2021 – MY 45M
The Vulkan After Sales manager’s phone rings: it is the captain of a 45-meter MY, sailing along the coast of the Mediterranean Sea, who complains of vibrations in almost every room on board, but especially in the owner’s cabin. The same day, Vulkan technicians board the boat: from an initial, purely visual inspection, it is evident that the elastic coupling between the engine and the inverter and the anti-vibration mounts are the original ones, dating back to the first installation in 1997! To the untrained eye, the elastic rubber parts of the coupling might appear to be in good condition due to the yacht’s few hours of operation, about 5,000 hours. The problem is the “old age” of the joint, which is a good 24 years old, almost three times its average life.
Old, stiffened rubber results in an alteration of the dynamic and functional characteristics of the component and, therefore, a substantial change in the vibro-acoustic response of the entire powertrain. In addition, the anti-vibration mounts installed under the engine also appear “exhausted,” characterized by excessive crushing due to age, resulting in a pronounced misalignment between the engine and the gearbox. It was precisely the perceived abnormal vibrations that were the wake-up call that allowed action to be taken, averting even worse damage: having replaced the elastic parts of the coupling and the anti-vibration mounts during winter maintenance at the shipyard, the captain was able to breathe a sigh of relief.
Joint with aged elastic parts
The incidents recounted are just a few examples of the major inconveniences that, during the summer or operating season, are handled at the last moment, leading to stress for the captain and disappointment, to put it mildly, for the owner and his guests. Fully functioning joints and mounts ensure full comfort on board: their regular maintenance is the easiest way to undertake peaceful navigation while keeping clear of emergencies.
(Vulkan Italy: the importance of periodic maintenance on board – Barchemagazine.com – March 2023)
