Unveiling The Impact Of Synthetic EALs On Marine Bearings


The marine industry faces a growing concern as evidence suggests a surge in stern tube seal failures, attributed to the adoption of synthetic Environmentally Acceptable Lubricants (EALs).

Thordon Bearings, renowned for seawater-lubricated bearings, applauds Gard’s latest research shedding light on the hidden costs of these synthetic lubricants, says an article published on thordon bearing website.

VGP Rules And Increased Seal Damage

The 2013 introduction of the US EPA’s Vessel General Permit (VGP) rules acted as a catalyst, leading to a “significant increase” in propeller shaft aft seal damage, according to Gard. This upswing aligns with the escalated use of approved synthetic lubricants in compliance with EPA regulations.

Gard’s Research Insights

Gard’s in-depth analysis of shaftline damage claims over the past decade reveals a noteworthy correlation – up to 80% of investigated incidents involved stern tube seal failures where synthetic EALs were in use. The research scrutinizes the chemical composition of these lubricants, suggesting potential performance drawbacks.

Chemical Composition Challenges

Gard underscores the 2019 DNV study, highlighting key differences between EALs and traditional mineral oils. Notably, the viscosity and pressure coefficient disparities in EALs may contribute to a lower safety margin during high-load operations, increasing the risk of seal failures.

Environmental Impact And Discarded Fishing Gear

International trade press reports, as acknowledged by Gard, suggest discarded fishing nets and rope contribute to aft seal damage in oil-lubricated shaftlines. This adds a layer of complexity to the environmental consequences, emphasizing the need for a comprehensive approach.

Thordon Bearings’ Perspective

Thordon Bearings’ VP of Business Development, Craig Carter, expresses concern over the unforeseen consequences of introducing synthetic EALs. Carter asserts that seawater remains the only 100% pollution-free lubricant, aligning with the US EPA’s VGP recommendations.

Thordon COMPAC System

Highlighting a solution, Thordon’s COMPAC bearings are central to an award-winning open seawater-lubricated propeller shaft bearing system. This system not only eliminates the need for an aft seal but also reduces friction, fuel burn, and emissions, while ensuring improved reliability and lower maintenance costs.


As the maritime industry grapples with the environmental and financial repercussions of stern tube seal failures, the debate over synthetic EALs intensifies. Thordon Bearings advocates for a seawater-centric approach, emphasizing the imperative to balance environmental sustainability with operational performance in marine lubricant choices.

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Source: thordon bearing