The threat of corrosion
Part 1 of this series referred to “icing”, where ocean spray freezes onto a ship’s superstructure and external components, potentially causing the vessel to tip. In especially cold temperatures, a film of ice can even form on internal machinery, gradually corroding the affected part. Depending on the severity of the corrosion, the equipment could require extensive repairs—or it could fail entirely, proving both costly and dangerous.
One component particularly prone to corrosion is wire rope. A previous article on Engineering at Sea reported an incident in which a rope had snapped, leaving an engine to fall 11 meters into the deep. The owner had to pay $1.3 million in damages. Although no one was hurt, it is easy to imagine how a cord supporting heavy items and weakened by corrosion could pose a threat to health and safety.
Lubrication: It keeps us safe, but is it ecological?
In Arctic seas, where ports are few and far between, the devastating potential of an accident is heightened. To prevent a corrosive layer of ice forming on an expedition ship’s components, lubrication is essential. A common way of keeping rope lubricated is to apply oil manually. However, this is slow, inefficient, and can cause injury. An automated lubrication system is therefore the preferred option.
With the SKF Wire Rope Lubricator, for example, shipowners can apply oil up to 90 percent faster than by hand. Aside from being quicker, the method is also safer; by eliminating the need for manual application, it reduces the risk of injury. Furthermore, the technology cuts the consumption of lubricant by up to a quarter, making it more cost-effective and ecologically friendly.
While an automated system can help mitigate environmental impact, choosing the right lubricant is equally important. Indeed, conventional mineral oils are damaging to the environment—an issue that is exacerbated in the fragile Arctic ecosystem.
Making the right choice
The Polar Code stipulates that shipping companies deploy non-toxic, biodegradable lubricants—otherwise known as “environmentally acceptable lubricants” (EALs)—when operating in Arctic seas.
Examples of EALs include triglycerides (vegetable oil-based lubricants) and polyalkylene glycols. The former have the highest VI, and their water solubility means they are able to maintain viscosity even in the event of water influx.
Synthetic esters are the most expensive class of EAL and tend to take longer to break down than vegetable oil lubricants. On the other hand, they compare favorably in terms of performance, boasting a strong resistance to fluctuating temperatures and a high viscosity index (VI—ability to retain viscosity as temperature changes).
The perfect combination
It is the responsibility of shipping companies to make sure their vessels are safe in Arctic waters while respecting the fragile ecosystem around them. Deploying the right lubricant in conjunction with an ecological automated lubrication system can keep a ship’s components—including wire rope—strong and healthy. In this way, shipowners ensure the safety of their investment, crew, and passengers while minimizing their environmental impact.