Overlooked Warriors

In maritime’s expanding focus on efficiency and environmental protection, the role of seals and bearings tends to be underestimated, if not forgotten

File image courtesy Thordon

Published Jul 26, 2023 8:59 PM by Chad Fuhrmann

(Article originally published in May/June 2023 edition.)

In the vast and dynamic maritime industry, marine seals and bearings play a vital role in both ensuring mechanical efficiency and safeguarding the environment – not only in individual equipment applications and the systems in which they’re installed but also at much larger scale in ships and the wider marine industry.

For any application utilizing rotating or rolling components, the choice of bearings and seals is critical. Bearings support both rotation and linear movement within a variety of mechanical and non-mechanical devices, mitigating the impacts of friction and radial and axial stress in critical applications such as stern tubes and large generator bearings.

These elements are, of course, not limited to engineering spaces. Applications topside include everything from windlasses and non-motorized rollers to simple sleeve bearings in searchlights.

Regardless of their application, seals often exist in transitional locations between environments, serving the dual purpose of retaining any necessary lubricant inside the bearing or housing while preventing ingress of contaminating fluid or material.

Whether separating a motor housing from the machinery space or the machinery space from the surrounding water, seals in particular serve as a protective barrier for the internal components of a machine as well its external operating environment.


From the earliest days of wooden ships through the development of turbines and reciprocating engines, seals and bearings have a long history in the maritime industry. The function and intent of these components have never altered.

However, as equipment and propulsion plants have introduced ever-increasing complexity, the introduction of self-lubricating materials, non-metallic bearings and advanced seal designs has likewise revolutionized seals and bearings.

Advancements and technology have at times led companies to look more closely at older, simpler designs that have proven to be even more advantageous in today’s industry. One fascinating example of this is water-lubricated journal bearings. Scott Groves, Vice President of Sales at Canada’s Thordon Bearings, notes that water-lubricated shaft lines are a century-old technology, “but today’s systems are a world away from their ancestors.”

Thanks to modern technology, water lubrication is the focus of renewed interest from end users and class societies, generating applications across commercial and military maritime markets and in deepwater as well as inland waterways.

Thordon couples modern materials and monitoring technology to create its advanced COMPAC water-lubricated shaft lines, offering a viable alternative to oil-lubricated systems. With today’s focus on the environment, Groves notes that oil-lubricated systems pose an inherent risk: “Loss of lubricant to the environment will always be prevalent. With water, there is zero risk of this.”

Unlike traditional water-lubricated rubber bearing systems, the seawater-lubricated COMPAC propeller shaft bearing system uses elastomeric polymer bearings designed uniquely to offer desirable performance and operational benefits. The low friction of Thordon bearings and the early hydrodynamic film development create an acoustically quieter bearing.  

Since the introduction of mechanically propelled vessels, the design and application of seals and bearings have likewise evolved significantly. Companies like Thordon have played pivotal roles in this history, driving innovation and pushing the boundaries of what is possible in maritime applications. These industry leaders leverage experience and technology with concern for not only for ships and equipment but for the environment as well.

Loose Lips

The maritime industry has no shortage of positive developments and unfortunate accidents related to seals and bearings.

The introduction of self-lubricating materials and advanced seal designs have vastly improved efficiency and reliability. Not only do such systems satisfy manufacturer requirements and class standards, they reduce maintenance requirements and increase lifespan, lower operating costs and enhance performance in the demanding environments of the maritime industry.

Incidents such as oil spills, however, have highlighted the continued need for robust seals and bearings to prevent environmental disasters and reinforced the importance of stringent regulations, regular inspections and the adoption of best practices to prevent leaks and ensure the safety of both machinery and the environment.

In the face of increasing environmental concerns and regulation, the role of seals has expanded beyond just machinery protection. Seals in maritime applications now play a vital role in preventing lubricating oil from leaking into the surrounding water. This shift in perspective has led to the development of environmentally conscious industry efforts such as the use of eco-friendly lubricants and the adoption of sustainable manufacturing practices.

The maritime sector has increasingly recognized the importance of minimizing its ecological footprint, and seals and bearings have become integral in this pursuit. Moreover, the improved focus on safety paired with growing public awareness of environmental issues means that inadequate seals not only risk the physical integrity of vessels but also the viability of companies who fail to ensure the environment is protected.

Noteworthy Trends

The seals and bearings market in the maritime industry continues to witness several noteworthy trends. Technological advancements have led to the development of condition-based maintenance systems, enabling predictive maintenance and reducing downtime. The emergence of autonomous vessel technology and remote equipment monitoring has also created new opportunities for efficiency and safety improvements.

These developments are key to providing a more holistic approach to the market. With its own water lubrication and monitoring and conditioning equipment package, Thordon has been able to obtain “technical equivalence to oil” class notations with several IACS members. As a result, newer vessels can be designed with a “sterntube-less” water-lubricated design concept that allows for the elimination of the forward bearing.

“This offers the ability to inspect/change the bearing without having to withdraw the shaft every five years,” says Groves, and can save big dollars on maintenance costs and potentially increase cargo capacity.

AEGIR Marine is making its own strides in the industry. The Netherlands-based, global provider of stern seal and propulsion products and services invests heavily in research and development with recent studies focused on the wider impact of stern tube seal performance. Its extensive research into the properties and chemical behavior of stern tube seals, bio-lubricants and other materials – in collaboration with leading technical universities – allows it to improve existing products while also developing new ones.

With shipowners are consistently looking for ways to prevent the intrusion of seawater into any element of the propulsion train, AEGIR’s R&D Manager Dennis Nahuijsen points out that improving the effectiveness of stern tube seals has undeniable environmental implications “as the water/oil interface is a potential source of pollution.”

Whether its Thordon, AEGIR or any of their competitors, dedication to environmental protection aligns with the greater maritime industry's growing demand for sustainable solutions.

Market Dynamics

The maritime industry continues to embrace these trends, recognizing the potential for increased operational efficiency and a reduced environmental footprint.

Advanced polymers and composites and other material advancements have enhanced the performance and lifespan of seals and bearings. These materials offer superior resistance to corrosion, higher load-carrying capacities and reduced environmental impact.

These benefits extend across the maritime market, encompassing the private, commercial and military sectors. Combined with stricter environmental regulations and increased demand for environmentally friendly solutions, these new materials are seeing expanded use across applications and environments.

After all, says Thordon’s Groves, “There’s no single product for all operating environments. Specialized materials suit different market conditions and are tailored to meet a vessel’s operating environment.”

Going forward, the maritime industry is expected to place increasing emphasis on sustainability and eco-conscious practices, creating new opportunities for companies that align with these principles, and the market for seals and bearings is poised for further growth.

Advances in technology – beyond materials – include the integration of IoT (Internet of Things) devices, artificial intelligence and automation, revolutionizing not just monitoring and maintenance but the way components are designed, manufactured and applied. These innovations will continue to have a significant impact on efficiency and overall system optimization.

Keep Rollin’

Seals and bearings are indispensable elements of the maritime industry and “overlooked warriors” in the battle against environmental pollution. They serve critical roles in the protection of equipment and systems and, through their evolution, are garnering additional recognition as essential for improving efficiency and environmental protection.

While the maritime sector is making progress in sustainability and environmental protection, there are aspects that require renewed attention. Companies like Thordon Bearings and AEGIR Marine champion efforts to promote eco-friendly practices and raise awareness of the importance of seals and bearings in protecting the environment. These companies actively engage in research and development to create solutions that minimize ecological impact and improve sustainability.

New advancements in these ubiquitous components promise to support the industry’s cleaner, more-efficient future, driven forward by leaders who champion innovation and sustainability. As technology continues to advance, the maritime sector will continue to rely on seals and bearings, not only in their traditional capacities but also as an increasingly important means to navigate the challenges of efficiency, environmental protection and the changing demands of an evolving industry.  

Marine engineering and operations consultant Chad Fuhrmann is a frequent contributor to The Maritime Executive.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.