How you minimize repair costs and off-hire times

Filtration and maintenance of gear oil: CJC® Thruster Filters

Filtration and maintenance of gear oil from thrusters is enormously important if …

  • you are annoyed by frequent repairs and off-hire times because thruster components wear out quickly.

  • you are dissatisfied because you have to change the oil regularly and especially bio oils (EAL) are very cost-intensive.

  • you want to optimize the manoeuvrability of the thrusters to ensure reliable operation at all times.

Your solution: a CJC® Thruster Filter in the offline circuit. Achieve the highest oil cleanliness for maximum protection of gear oil and thruster — quickly, efficiently and cost-effectively.

Contact your maritime technical salesperson now

The challenge: water in gear oil

Water in the gear oil of thrusters causes high costs for vessel operators as a result of unplanned lay days due to oil changes and repairs to the thruster. Water in the gear oil is the leading cause of malfunctions of a thruster due to damage to the propeller control, shaft, bearing and gearbox. Unfortunately, despite technical developments, water ingress is not entirely avoidable: water ingress through damaged, worn shaft seals or by overcoming the static pressure The shaft seals usually wear out from particles in the oil. In particular, particles < 1 μm have an abrasive effect due to the low dynamic tolerance. Additionally, when biodegradable lubricants are used, they decompose on contact with water or form stable oil-water emulsions. Premature oil changes are costly in these cases, because these special oils are 3, 5 and even up to 8 times more expensive than mineral oils. Watery, contaminated and rapidly ageing oil has severe consequences because if the thruster drive does not work, you have to accept docking and costly repairs while losing orders:

Damage and consequences of contaminated gear oil in thrusters

Water in the gear oil accelerates oil ageing and oxidation processes and leads to rapid degradation of certain additives through hydrolysis, leaching and the change in dielectric conductivity. As a result of oil ageing and oxidation, the acidity increases, viscosity changes, and resin- (varnish) and sludge-like deposits are formed. We have already observed acid numbers (TAN) of 19.4 mg KOH with biodegradable lubricants. Microbial growth is also possible. Bacteria, algae, and other microbes from the ingressing seawater multiply and lead to bio-corrosion and sludge.

Compared to mineral oils, most biodegradable lubricants decompose very quickly upon contact with water due to their low hydrolytic stability and low oxidation resistance, or they form stable emulsions (water droplets are finely distributed as a suspension throughout the oil system). This makes using a system that continuously reduces the water content even more important.

Click on the picture to read more about the oil samples:

getriebeöl filtrieren und pflegen, ölproben vor und nach filtration

In the case of emulsified water in the gear oil, the viscosity increases, and the oil becomes more viscous, which leads to a lack of lubrication. Water interferes with the formation of an elastohydrodynamic lubricating film. With ester-based lubricants, on the other hand, the viscosity decreases, and the oil becomes thinner, which in turn influences the lubricating effect. In both cases, there may be contact between the metallic surfaces and thus increased wear.

Water in the gear oil causes corrosion and rust on the metal surfaces. Water combined with acids produced by oil ageing and oxidation processes has a highly corrosive effect. Abrasive particles break out of the corroded surfaces, damaging surfaces, seals, moving components and blocking narrow passages.
Although e. g. polyglycol-based lubricants such as PAG have a high saturation limit of over 10,000 ppm in terms of water, i.e. they can keep a lot of water in the dissolved state, but that can be disadvantageous. Pressure and temperature fluctuations such as those occurring in gears and bearings can release the dissolved water as free and emulsified water so that it can develop its harmful effects resulting in cavitation with erosion-like material removal, micro-pitting, and hydrogen embrittlement. As free and emulsified water, it can develop its harmful effect, e. g., cavitation with erosion-like material removal, micro-pitting, and hydrogen embrittlement.

Next to salt crystals which enter the gear oil with salty seawater, but also wear and rust particles cause damage to gears, bearings and sealings (abrasion, fatigue). The circulation in the oil continues to cause particles, resulting in a chain reaction of wear.
Oil ageing produces various reaction products precipitating and depositing when the gear oil cools. Either as sludge-like deposits that sediment, or resin- and varnish-like deposits that form a solid, sticky layer on the metal surfaces to which particles stick. A sanding effect is created, and wear increases rapidly, e.g. by changing the lubrication gap geometry of bearing shells.

Impurities, oxidation residues and an increase in viscosity worsen the air separation capacity. Air bubbles in the transmission oil rise worse, and the foam risk increases, resulting in a lack of lubrication.

The conventional method

To ensure the reliable operation of the thruster, the inspectors regularly check the gear oil. When the oil draws near a critical limit value, the oil sump is partly replaced (bleed-and-feed) or completely changed. However, this does not reduce the load on the gear oil. On the one hand, the newly filled-in oil contaminates within the shortest time due to deposits and dilution with dirty residual oil. On the other hand, impurities, oxidative processes and acids unhindered strain the gear oil’s lubricating properties and the additives’ long-term effect, which shortens the service life of the oil filling. That finally results only in high oil consumption. With us, however, this is more ecological and economical.

Contact your maritime technical salesperson now

Your solution: Efficient care of the gear oil

Efficient gear oil care means continuously removing water, particles, oxidation residues and acids from the gear oil (24/7). Because only with permanently clean and dry lubricant …

  • you achieve a longer lifetime for your oil filling, protecting your budget and simultaneously resources.

  • you ensure maximum wear protection and save time and money in terms of maintenance and repair.

  • you minimize unplanned downtimes and lay days, for more excellent reliability and availability of your vessel.

  • you ensure the highest possible oil cleanliness and thus provide guaranteed manoeuvrability at all times.

Filtration and maintenance of gear oil, avoid oil change thruster

Less oil consumption

Filtration and maintenance of gear oil, less maintenance required at thruster

Less maintenance

Filtration and maintenance of gear oil, higher reliability with thruster

Higher reliability

Filtration and maintenance of gear oil, higher resource protection at thruster

Higher resource protection

Contact your maritime technical salesperson now

CJC® Thruster Filter for filtration and maintenance of gear oil

CJC® Thruster Filters for the filtration, dewatering and care of gear oil ensure consistently dry and clean lubricant. Achieve the highest level of protection for your oil filling and thruster quickly, long-lasting and cost-effectively.

The own pump unit allows installation in a separate circuit (offline) and thus the continuous depth filtration and care of the gear oil (24/7).

In the ideal case,the pump sucks in the contaminated oil from the lowest point of the gearbox. But that is only possible with larger thrusters from certain manufacturers, as they have appropriate connections for installing an offline filter (see example 1). With this special connections the suction from the lowest point is also possible for thrusters with a rotation radius of 360 °C (azimuth etc.)
In all other cases, the pump sucks in the oil from the void space at the top, with the discharge either back to the same or to the header tank (see example 2). After oil filtration the oil is discharged either back to the void space or to the header tank (see example 2).

thruster filter, installation
thruster filter, installation

The CJC® Thruster Filter removes all impurities:

Water – free, emulsified and dissolved

for water content well below the saturation limit of the oil
(typisch < 500 ppm bzw. 0,05% — (typically < 500 ppm or 0.05% — in many cases, the CJC® Thruster Filter can reduce the water content even down to 0,1 %, but the rate of water ingress and the demulsibility of the oil play an important role)

Oxidation residues and acids

for persistent stable oxidation rate, TAN and TBN

Wear particles and suspended solids

Achieve cleanliness classes up to ISO 12 (ISO 4406).


Prevent the spread of microorganisms with dry gear oil and efficiently remove existing microorganisms thanks to the high filtration degree and depth filter effect.

Due to their variety of combinations and modular design, the CJC® Thruster Filter and the integrated CJC® Depth Filter Insert can be optimally adapted to the specific conditions of the different thrusters and gear oils.

CJC® Fine Filter Inserts are depth filters with a filtration degree of 3 µm absolute and a retention rate of < 1 µm. The whole volume of the insert is made of numerous finely ramified fibres and offers an outer surface and, in addition, an inner surface – from 120 up to 150 m² per gram. That enables the extremely high dirt holding capacity – the higher, the longer the lifetime of the filter inserts.

The fact is that our dirt holding capacities are market leaders.

depth filters, cellulose filters, cjc fine filter cartridges

CJC® Thruster Filters can optionally be equipped with sensors for automatic online monitoring of the filter and oil condition. Depending on the selected system, you can select up to nine sensors – whether for oil moisture, oil temperature, particles (4-250 μm), wear particles (40-1,000 μm), oxidation rate, filter pressure and/or thruster utilization. You can configure alert limits and warnings to prematurely detect deviations from normal conditions and counteract them.
Our oil condition sensors provide detailed real-time data and allow conclusions about the thruster condition due to the high data density.
Our intuitive operable cloud applications have a clearly-arranged dashboard to visualise the sensor data. The highly developed algorithms integrated into the premium monitoring package automatically evaluate and interpret the data – ideal for critical thrusters where failure quickly has costly consequences. Optionally, the sensor data can be transferred to your own system via various interfaces.

CJC® Thruster Filter: Filtration and maintenance of gear oil

thruster filter, filtration and maintenance of gear oil
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Contact your maritime technical salesperson now

Let’s talk about your thruster, your gear oil and the specific challenges. We filter every gear oil. It does not matter whether you use mineral oil or biodegradable lubricant. Together with you, we maximize the service life of oil filling and thruster.

Receive a personal consultation and a non-binding offer about a CJC® thruster filter for the efficient care and filtration of gear oil.

Write or call me.

Andreas Mann
Andreas MannKey Account Manager - Marine Segment
Mobile: +49 (0)151 12 88 38 05
Fax: +49 (0)40 855 04 79 – 20
oil samples, water in gear oil, before after
oil samples, water in gear oil, before after
oil samples, water in gear oil, before after

That say our customers

Gear oil filtration, thrusters, harbour tug

“Only with the CJC® Thruster Filter could the gear oil finally be dried satisfactorily. Without CJC®, we would have had to change the 1,500 liters of gear oil soon. By avoiding the oil change, we were able to save 4,890 EUR (3.26 EUR/litre) – an important contribution not only in terms of budget, but also in terms of resource conservation. The excellent results convinced us, so that we decided to purchase two identical CJC® Systems for our tugs “Bugsier-5” and “Bugsier-6”.

Read application study

gear oil maintenance, thruster, harbour tug

The CJC® Thruster Filter allows us to remain the tug in operation for 6 months before its next technical shutdown. The results of the oil analyses are clear and clearly demonstrate the effectiveness of the CJC® Thruster Filter.”

Read application study

gear oil maintenance, thruster, harbour tug

„After having tested nearly every piece of water removing equipment on the market in order to solve our water and contamination problem, we went for the CJC® Thruster Filters, because it was simply the best. The filters did the job to our greatest satisfaction, removing particles, water and other waste products. CJC® Thruster Filters for oil maintenance are a very good investment. The return of investment is very short.“

Technical inspector, Gulf Offshore Norway AS, Supply Vessel

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