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Stern tube oil filtration and water removal equipment installed inside a vessel machinery space.

Avoided emergency docking by restoring stern tube oil condition

Efficient removal of emulsified water restored oil quality in a stern tube system, reducing failure risk and keeping the vessel in operation.

Case study written by Christopher Alnor & Sean Pedersen, C.C.JENSEN A/S, Denmark

Application Snapshot

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Industry:

Marine

Globe icon representing geographic location or country.
Country:

Denmark

Oil droplet icon representing oil type or lubrication fluid.
Oil type:

Stern tube lube oil (Total Disola M 4015)

Executive summary

An anchor handling tug supply vessel experienced increasing water contamination in its stern tube lubrication system following a change to a new oil type. Due to the oil’s poor demulsibility, the existing filtration solution was unable to control water levels, increasing the risk of mechanical failure and unplanned downtime.


By installing a CJC® Desorber/Filter Combi Unit, emulsified water was efficiently removed from the oil. Within one month, water content was reduced from a critical level to a nominal level, restoring oil condition, prolonging vessel operation and avoiding emergency docking.

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Cylinder icon representing rapid reduction of water content in stern tube oil.

Rapid water removal

Water content reduced from 7,186 ppm to 144 ppm within four weeks.

Gear with checkmark icon representing lower wear and reduced mechanical failure risk in stern tube components.

Reduced wear and component risk

Dry oil significantly lowered the risk of mechanical failure in the stern tube.

Dollar symbol icon representing avoided emergency docking and reduced maintenance costs.

Avoided unplanned costs

Emergency docking avoided and maintenance costs reduced through restored oil condition.

CO₂ cloud icon representing continued vessel operation and extended uptime through stable oil condition.

Extended operational uptime

Stable oil condition enabled continued vessel operation without interruption.

Anchor handling tug supply vessel operating at sea during sunset.

Client brief

An AHTS (Anchor Handling Tug Supply Vessel) operating in Danish waters experienced oil condition challenges in its starboard stern tube after switching to a new lubricating oil.

Oil sample bottles showing dark contaminated stern tube oil with water and emulsified contamination.

Challenge

The new oil type had poorer demulsibility than the previous oil, leading to steadily increasing water content. Existing filtration equipment was unable to remove the emulsified water, pushing the system towards a critical condition and increasing the risk of failure and emergency docking.

Stern tube lubrication piping connected to a CJC® Desorber/Filter Combi Unit for water removal.

Solution

A CJC® Desorber/Filter Combi Unit D5 was installed on the stern tube lubrication system to remove emulsified water from the oil and restore acceptable operating conditions.

Chart showing reduction in water content and improvement in water saturation in stern tube oil over a four-week period.

Restoring oil condition without interrupting vessel operation

To verify performance, six oil samples were taken over a four-week period, including one sample prior to installation and five samples following commissioning of the CJC® Desorber/Filter Combi Unit.


The unit operated continuously, efficiently separating emulsified water from the oil without disrupting vessel operation. Oil condition improved steadily throughout the test period.

Measurable results and operational impact

The installation of the CJC® Desorber/Filter Combi Unit D5 restored control of oil condition in the stern tube system after a change in oil type led to critically high water content. Within just four weeks, water levels were reduced from 7,186 ppm to 144 ppm, bringing the oil from a critical state back to a nominal level in line with general stern tube guidelines.


By efficiently removing emulsified water, the solution significantly reduced the risk of mechanical failure, lowered maintenance costs and spare-part consumption, and enabled continued vessel operation. As a result, emergency docking was avoided and overall operational reliability was improved through consistently dry oil.


Engineers inspecting a CJC® oil filtration system used to restore stern tube oil condition.

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