Why spend £1M on a new shaft line when you can spend 10% of that while preserving the installed system and extending its running hours?
There are simple and relatively inexpensive preventative measures that ship operators can take to reduce the risk of shaft line breakdowns, unplanned maintenance, and the significant associated costs.
Discussing the topic during a recent webinar Reducing maintenance and operational costs through integrated shaft line solutions, Wärtsilä Shaft Line Solutions sales director, Panu Sorvisto, noted its Shaft Line Solutions service encompasses all the components of the shaft line and it was for this reason that Wärtsilä changed the name from ‘Seals and Bearings’ to ‘Shaft Line Solutions’, which better reflects the holistic nature of the service. This is a service with 900 professionals in 75 countries worldwide. Approximately 35% of newbuildings have elements of Wärtsilä Shaft Line Solutions’ equipment onboard and over 30,000 vessels have been supplied.
“We have our factories, we have our own field service teams, our own sales teams and cover old and new parts,” said Mr Sorvisto.
Wärtsilä Shaft Line Solutions area sales manager Europe & Africa – Shaft Line Repair Services, Marco Gordon said the service focuses on speed and availability of parts and service. “Wherever you are, we have a rapid response, cross-collaboration team of experts committed to getting your vessel back in the water,” said Mr Gordon.
“Around two-thirds of the repairs we undertake are the result of a chain-reaction damage”
“Our project managers act as a one-stop shop representative of Wärtsilä, coordinating the work scope, arrival of experts and manufacturing and delivery of the right parts and monitoring work progress,” said Mr Gordon. “The project manager liaises with the superintendent on the vessel and provides a daily one-call update on everything from the flywheel to the propeller,” he added.
Practical case studies
After the discovery of water in the stern tube, the vessel decided to continue to the next dock, where a stern tube kit was sent to greet the vessel. Unfortunately, further inspection revealed more problems. New parts were manufactured and flown out but due to Covid-19 restrictions, Wärtsilä Shaft Line Solutions’ staff were unable to reach the vessel and the work was undertaken by local engineers under remote supervision. All the different streams of work were coordinated by the Wärtsilä Shaft Line Solutions’ project manager.
The total cost of repair was US$650,000. A post-repair examination of the damaged parts revealed the root cause was wear on the face seals, leading to a loss of pressure and water ingress. Steaming to the next dock increased the level of damage. One solution would have been to have fitted an air barrier seal at a cost of around US$40-60,000 which would have pressurised the void space, preventing the entry of water from the worn face seal.
In a Riviera survey which asked Would you consider an upgrade to an air barrier seal to gain more safety on leakage concerns? 87% of respondents said that an upgrade to an air seal would be considered and only 13% said they would not consider the option. The air barrier seal can also be used with mineral oils in the bearing when operating in US waters. Mr Gordon noted that it is a solution to continue to run stern tube bearing on mineral oil and still have permission to sail in US waters without changing to the much more expensive EALs.
Air barrier seals have been approved by classification societies and a vessel that was updated to an air barrier seal would be a modification and require class society sign off.
2. A twin-shafted cruise ship hit rocks and damages a propeller
The impact shifted the shaft. Extensive repairs were needed but the cruise ship was due to sail within 23 days with a full complement of passengers. Cancelling the voyage would have resulted in a loss of US$4M to the operator. The job was completed in 21 days at a cost of US$400,00 (including equipment and transport costs) versus a potential loss to the client of US$4M.
Wärtsilä Underwater Services managing director, William Winters is the managing director of the group of services that was previously known as Trident, which is now a fully integrated company with Wärtsilä. He presented the example of a 6,500 teu container ship which had a leaky aft seal that was damaged by a foreign object and repaired at sea by Wärtsilä Underwater Services.
Considering the costs of offloading around 4,000 containers and the off-hire dry dock time, Wärtsilä Underwater Services was able to offer a cheaper and quicker solution. The next port was Rotterdam, a home port for Wärtsilä Underwater Services operations, and an air transportable hyperbaric chamber was taken to the vessel and fitted around the stern tube. The hyperbaric chamber is sealed and pressurised, and while cargo operations took place, the diver was able to overhaul the shaft assembly.
A wide range of underwater repairs can be undertaken by Wärtsilä Underwater Services, including thrusters, rudders, and propellers, including cold-straightening and wet welding. In a Riviera poll: what would be your biggest concerns related to underwater services? 31% of respondents were concerned with high quality workmanship, 25% with costs and 25% with availability. The remainder, 19%, were concerned with safety.
Underwater operations are inherently dangerous and have operational limitations, such as the speed of the current in the port. Some shipping services have started to replace divers with drones. Mr Winters noted that underwater drones or UAVs have already been used for underwater shaft line inspection. “It comes down to what they can do,” he said. “As their capabilities grow, so will our usage. Is there the capability today to perform the majority of the repairs that we do, like in situ seal repairs or welding? The technology is not there yet,” he said.
Mr Gordon noted that preventative maintenance could have caught and mitigated many of the failures. “Today, many vessels run equipment until it breaks and this nearly always leads to a list of new parts as the breakage causes a chain-reaction down the shaft line,” said Mr Gordon. “Around two-thirds of the repairs we undertake are the result of a chain-reaction damage,” he said.
In a similar vein, operating vessels at the extreme end of the performance envelope will impact the health of the shaft line. This is more likely in naval vessels where unbalanced loadings on the propeller can occur when such vessels undertaking extreme manoeuvres. The key is to understand those forces and mitigate the impact with careful design. The data analysis required to understand the forces involved was explained by Wärtsilä Shaft Line Repair Services’ Alignment and Measurement services manager, Jens Hyrup. He said the first step is to analyse the set-up and check against the real-life measurements on the vessel. “This allows a reverse calculation of loadings on different operational patterns,” said Mr Hyrup.
“Newbuilds are more sensitive compared to vessels of old-fashioned design”
Mr Gordon added that in these cases, it is a huge benefit to have real-time data for the behaviour of the shaft line. “We can get an impression of what is the problem, when does it occur and where does it come from,” said Mr Gordon.
“We strongly recommend to implement 3D (shaft line) analysis into every vessel’s docking plan,” he said. “[This] should include static loads, dynamic run out and vibration levels are different RPMs.”
It would seem the majority would agree; in a Riviera survey, participants were asked: Do you see a value in installing a propulsion shaft line monitoring system permanently? 84% agreed with the statement and only 16% disagreed.
One possible reason for the higher number of repairs seen today is that modern design techniques and better instrumentation at the building stage allow modern ships to be built closer to tolerance limits than older vessels. “Newbuilds are more sensitive compared to vessels of old-fashioned design, but it also depends on how the vessel is operated.” said My Hyrup. He also noted that hull structures today are weaker compared to the traditional way of building.
“It is not necessarily a negative aspect,” said Mr Gordon. “Design criteria become tighter, more efficient and the ship is more sophisticated. Therefore, a more sophisticated tool is required,” he said. This provides preventative maintenance by providing data on the behaviour of the shaft line. He added that education is also important: “Creating an awareness with the crew is also part of preventative maintenance.”
He continued: “The 3D laser measuring of the shaft line in operation provides a far higher degree of accuracy than the older static measurement process.”
Follow the link to watch the webinar in full: www.rivieramm.com/webinar-library/webinar-powertrain/reducing-maintenance-and-operational-costs-through-integrated-shaft-line-solutions---why-spend-1m-when-you-can-spend-100k-on-repairs