Extensive legislation is making the case for water lubricated stern tubes

Extensive legislation is making the case for water lubricated stern tubes

Malcolm Latarche

Malcolm Latarche · 01 June 2018


The world’s oceans are undisputedly threatened by ever greater levels of pollution, a fact that the International Maritime Organization (IMO) and the United States Environmental Protection Agency (EPA) are keenly aware of. Consequently, in order to protect the oceans, the amount of legislation being written to prevent ships from adding to sea pollution through discharge or leakage is rapidly increasing. Here we look at Water lubricated stern tubes.

In 1972 came the EPA’s Clean Water Act. This established the basic structure for regulating pollutant discharges into United States’ waters, giving the EPA the authority to implement pollution control programmes. This was further amended in 1987 with the passing of the Water Quality Act, which granted new powers and responsibilities to the EPA regarding discharges into marine waters.


More recently, in 2008 the EPA introduced the Vessel General Permit (VGP) and subsequently re-issued it in 2013. The VGP provides for National Pollutant Discharge Elimination System (NPDES) permit coverage for incidental discharges into U.S. waters from commercial vessels greater than 79 feet (24 metres). This has a direct impact on ships with oil lubricated shaft lines, since even when fitted with bio or air type seals, there is the risk of leakage should they be in any way damaged. The alternative for guaranteeing compliance is to switch to a water lubricated stern tube solution, and this is increasingly happening across all sectors of the marine industry.

The latest in this legislative series came in 2017 with the IMO’s adoption of a mandatory Polar Code applicable to ships sailing in Arctic or Antarctic waters. This provides an operational framework, the main requirements of which are related to safety, environmental protection and crew competence. The environmental section focuses on the prevention of pollutants, including oil, being discharged into these pristine waters.

It is unlikely that the rules and regulations covering discharges from ships will end here. Almost certainly there will be further legislation to tighten still further environmental protection measures. But even with the legislation already in place, owners and operators of ships with oil lubricated stern tubes face the risk that any leakage will allow a discharge of oil into the sea, thereby contravening these regulations.

The reliable, cost-effective and environmentally sustainable water lubricated solutions developed by Wärtsilä Seals & Bearings ensure compliance with the regulations, and represent a completely viable alternative to oil lubricated solutions. Not only do the Wärtsilä water lubricated stern tubes operate as efficiently and as economically as those using oil, they provide the added value known as ‘peace of mind’ since there is no risk of causing oil pollution.

The current legislation, and future possible rules and regulations aimed at protecting the maritime environment, are intentionally tough. They have to be in order to be effective. However, as regards stern tubes, the answer is simple – switch to water lubricated solutions and ensure full compliance with the most stringent of current, and future, legislation.

Contributed by Wärtsilä Seals & Bearings

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