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Using EALs on sterntube seals

3 technical solutions to facilitate VGP compliance

A non-OEM sealing ring supplier recently changed the recommended operating life of its products. This could have a serious impact on vessel reliability and lead to increased costs. We explore the options available to shipping companies to resolve these issues and maintain VGP compliance.

For many vessels that sail in US waters, the Vessel General Permit (VGP) is one of the most important regulations. The current version, issued by the United States Environmental Protection Agency (EPA) in 2013, requires the use of environmentally acceptable lubricants (EALs). These biodegradable lubricants are minimally toxic and must be applied to all oil-to-sea interfaces, such as sterntubes, stabilizers, and thrusters.

The challenge of switching to EALs

However, EALs are only compatible with certain sealing materials. Due to hydrolysis, some EALs can weaken the material of the sealing rings, considerably shortening their lifespan. For this reason, suppliers of seal components often issue a list of EALs that have been tested and approved for use with their seals.

For older vessels in particular, VGP compliance can be demanding. The majority of ships built prior to current environmental regulations are equipped with non-flushable sealing systems at the sterntube. This means that the lubricating oils cannot be replaced with fresh oil while the vessel is in operation. As a result, the seals will have a reduced operating life. Consequently, the vessel will have to enter a dry dock more frequently, leading to increased costs and downtime.

What ship operators can do now

  1. The EPA makes an exception for vessels that can only maintain the regular five-year docking interval by undergoing a major conversion. If a vessel is fitted with a non-flushable sealing system, the EPA considers the use of EALs as “technically infeasible”. In this case, the OEM of the sealing system can issue a Statement of Technical Infeasibility, allowing the vessel to continue using mineral oil. However, it is important to note that the VGP will be reissued at the end of 2018, and it is uncertain whether this option will remain a possibility.
  2. Ship operators also have the option to upgrade the vessel’s aft seals. With state-of-the-art seal technology to reduce friction and surface pressure, innovative materials can be used for the sealing rings. Although this procedure is more expensive, it is an effective way to achieve full VGP compliance with no operational limitations, making it the safer choice in the long run.
  3. Alternatively, ship operators with non-flushable sealing systems can simply switch to EALs while keeping their existing configuration. The drawback, however, is the reduced operational lifetime, meaning a shorter dry docking interval for the vessel and higher costs.

OEMs: Suppliers you can rely on

A valid Statement of Technical Infeasibility can only be issued by the OEM, which in the case of Simplex sterntube seals is SKF Marine. This means customers of non-OEM suppliers could now require additional dry docking or major conversions.

For example, a non-OEM sealing ring provider recently released a disclaimer to inform customers that its sealing rings only have a two-year lifespan when used with EALs. As the supplier had previously stated a five-year operational life, its customers now face a number of issues. The reduced lifetime means that the affected vessels have a considerably higher risk of reduced performance, failure, and even emergency docking. This could lead to major disruption to operations and high costs.

To stay on the safe side, ship operators should turn to experienced OEMs. Thanks to advanced facilities for testing and research and development, such companies are better able to provide a reliable service and accurate information. This can help prevent costly operational and compliance issues in the future.

If you require more information on the VGP 2013, this FAQ provides a useful overview.


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