Harbour tug with AQUAMASTER azimuth thruster moored at port, illustrating marine thruster oil dehydration and restored operation.

Avoided emergency drydock by restoring contaminated thruster oil

Mineral gear oil dehydration on an AQUAMASTER azimuth thruster enabled a harbor tug to remain fully operational until its next scheduled drydock.

Case study written by: Hervé Solle, C.C.JENSEN France

In cooperation with: C.C.JENSEN A/S, Denmark

Application Snapshot

Factory icon representing industrial application or sector.

Industry:

Marine

Country:

France

Oil type:

EPONA Z 100 (marine mineral gear oil)

Executive summary

A harbor tug operating in France experienced seawater ingress in its starboard azimuth thruster, contaminating the mineral gear oil with critically high water content and elevated sodium levels. With the next scheduled drydock still six months away, continued operation was at risk.

To restore oil condition without interrupting vessel operation, a CJC® Desorber / Filter Combi Unit D5 was installed. Weekly oil sampling was initiated to monitor oil condition and filtration performance.

Within one week, water content was reduced from 3,904 ppm to 136 ppm. Wear metals and sodium levels were also significantly reduced, extending oil and component lifetime and allowing the vessel to remain operational until its planned technical shutdown.

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H₂O droplet icon representing rapid reduction of water content in thruster oil.

Rapid water removal

Water reduced from 3,904 ppm to 136 ppm

Gear with checkmark icon representing lower wear metal levels and reduced stress on components.

Reduced wear and component stress

Wear metals (Fe & Cu) significantly reduced

Dollar symbol icon representing avoided emergency drydock and reduced oil replacement costs.

Avoided unplanned costs

Emergency drydock and oil replacement avoided, extending oil and component lifetime by factor 5–6.

CO₂ cloud icon representing reduced oil consumption and lower associated emissions.

Lower environmental footprint

No oil change required, reducing oil consumption and associated CO₂ emissions.

Harbour tug moored at port, representing marine thruster operation in demanding service conditions.

Client brief

VB PORNIC is a harbor tug operating under demanding marine conditions, where thruster reliability is critical to daily operations and unplanned downtime results in high operational costs.

Oil samples showing clean oil and contaminated thruster oil affected by seawater ingress.

Challenge

Seawater ingress into the starboard azimuth thruster caused severe oil contamination, increasing the risk of corrosion, accelerated wear, and gearbox failure before the next scheduled drydock.

CJC® Desorber/Filter Combi Unit installed for continuous removal of water and contaminants from thruster oil.

Solution

A CJC® Desorber / Filter Combi Unit D5 was installed to continuously remove water, particles, and salt contamination, restoring oil condition without interrupting vessel operation.

Bar chart showing rapid reduction in water content in thruster oil after installation of a CJC® Desorber D5.

Restoring oil condition without interrupting vessel operation

Oil analysis revealed a water content of 0.39% (3,904 ppm) and sodium contamination of 22 ppm, posing a significant risk to the gearbox and bearings. With drydock still six months away, immediate oil replacement or mechanical intervention was not an option.

The CJC® Desorber D5 was installed and operated continuously. Weekly oil sampling confirmed rapid and stable improvement in oil condition. Within one week, water content was reduced to 136 ppm, well below the recommended maximum of 300 ppm.

In parallel, wear debris levels were reduced. Iron (Fe) decreased from 29 ppm to 17 ppm, copper (Cu) from 4 ppm to 1 ppm, and sodium (Na) from 22 ppm to 13 ppm. The oil was restored to a clean and dry condition, allowing safe continued operation.

Measurable results and operational impact

The filtration solution enabled the vessel to remain fully operational until its next planned technical shutdown, avoiding costly emergency docking and oil replacement.

According to industry reference data, the achieved oil condition corresponds to a lifetime extension factor of 5–6 for both oil and components. The restored oil cleanliness reduced wear, improved reliability, and stabilized maintenance planning.

“The installation of the CJC® Desorber D5 allowed the vessel to remain operational for six months before its next technical shutdown. The results of the analyses clearly demonstrate the effectiveness of the solution.”

– Olivier Gloaguen, Regional Technical Manager

Two service technicians posing beside a CJC® Desorber unit in a vessel engine room.

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