Shipowners - Waving Goodbye to Oil Pollution



















Based on a paper written by Dr. Dagmar Schmidt Etkin, the damage caused by operational discharges from the stern tube is estimated to cost US$322 million annually. (Ekins, 2010, Worldwide Analysis of In-Port Vessel Operational Lubricant Discharges and Leakages)

Stern tube oil leakage has been considered a common operating practice, however times are changing.

Changes to Environmental Regulations

According to the new US Environmental Protection Agency’s Vessel General Permit (VGP) that came into effect December 19, 2013.

  • All vessels must use an environmentally acceptable lubricant (EAL) in all oil to sea interfaces, unless technically infeasible.
  • EPA recommends that all new build vessel operators endeavor to use seawater-based systems for their stern tube lubrication to eliminate the discharge of oil from these interfaces to the aquatic environment (Environmental Protection Agency, 2013).

The IMO Polar Code, effective in 2017, states that Polar waters will be “zero discharge” areas under MARPOL Annexes 1 and 2 (oil and noxious liquids). The Code states: “Any discharge into the sea of oil or oily mixtures from any ship shall be prohibited” (International Maritime Organization, 2014).

Recently, Lloyds Register (LR), DNV-GL, Bureau Veritas (BV) and China Classification Society (CCS) have modified rules for open seawater lubricated propeller shaft systems, allowing the shaft to remain in place if certain monitoring conditions are met. With these new Class Society rule changes, it removes a major obstacle that ship owners had with water-based propeller shaft bearing systems. A Thordon COMPAC open seawater lubricated propeller shaft bearing system can meet the new rules and eliminate any risk of oil pollution. Its’ simplicity is shown in this video. For information about these changes and their impact to water-based propeller shaft bearing systems, click here.

Cost Associated to Environmental Changes

Based on the changes to the U.S. EPA Vessel General Permit (VGP) and the IMO Polar Code, ship owners that trade in U.S. waters need to decide whether to convert to EALs or seawater lubrication.  Both options have costs associated with them, however a seawater-based system has much lower operational costs.

The most obvious difference between the lubricants is the purchase cost, which is illustrated in the image below:


The cost of EALs is seven to ten times higher than mineral oils used for lubrication. Oil lubricated propeller shaft systems must be equipped with a sealed system requiring a FWD and AFT seal where seals must leak to operate properly. And stern oil leakage can also occur if the aft seal is damaged. If a leak should occur the vessel may face fines and clean-up costs.

A ship equipped with a COMPAC seawater lubricated propeller shaft bearing system may lead to a higher up front cost due to open system corrosion protection, however the installation cost is recouped within 3-4 years due to the decrease in operational costs. The following costs are eliminated with seawater lubrication:

  • no aft seal to maintain as there is no aft seal (only a water lubricated fwd seal)
  • elimination of oil or EALs from the stern tube
  • no purchase of oils or EALs
  • no storage of oil
  • no sampling of oil
  • no disposal of oil
  • no labour required to top up header tanks
  • no emergency seal repairs - no risk of rope/line damage to aft seal
  • maintenance of seawater lubricated bearing systems is very low

EALs – Hidden Truth

Since EALs are a fairly new form of lubrication in marine operations there are still a number of unknowns. EALs - Environmentally Acceptable Lubricants were designed to be less impactful to the environment however they were designed to degrade in soil not water. In order to be classified as an EAL, the lubricant must biodegrade by 60% within 28 days.

Polyalkylene Glycol (PAG) is considered one of the safest EALs on the market, however it is important to remember that no matter the oil type, whether mineral or EAL, they can still have a harmful impact to marine life. A perfect example of the damage done by an EAL spill would be the 1999 canola spill in Vancouver Harbor, Canada which killed 1000s of seabirds.

(Source: Burton, May 2013, Oil and Water – Don’t Mix, LUBES’N’GREASES)

Why not be future compliant?

In our opinion the only acceptable stern tube oil leakage should be ZERO! Thanks to those vessels that have converted to our Thordon seawater lubricated stern tube bearings, we are pleased to announce that with your help we have saved over 58 million litres or 15 million US gallons of stern tube oil from entering our oceans, seas, lakes and rivers. Our oil saving calculator is updated daily and will continue to track our progress of removing stern tube oil from our waters until this problem no longer exists.

[The calculator below demonstrates the number of oil in litres and US gallons that have been eliminated from entering into our water ways. Calculation is based on the following assumptions: number of vessels converted to seawater lubrication; 300 day operational year; and average oil leakages = 6 litres/day (1.6 US gallons/day) per vessel.]

Why not be proactive and get ahead of future changes to environmental regulations and rules by joining the growing list of ship owners that have already converted to seawater lubricated propeller shaftlines.


Volume of oil discharges prevented (Litres)


Volume of oil discharges prevented (US Gallons)