How you can maximize the lifetime of gearbox, main bearing and pitch hydraulic

Oil Care in Wind Turbines: CJC® Offline Filters

How you can maximize the lifetime of gearbox, main bearing and pitch hydraulic

Oil Care in Wind Turbines: CJC® Offline Filters

Oil care in wind turbines is a MUST if you want to

  • be annoyed by damages to the gearbox, main bearing and pitch hydraulic, despite filters already installed.

  • have to put up with long delivery times for crane technologies and components.

  • want to avoid failures and downtimes through optimum wear protection.

  • want to maximize the wind yield of your wind turbines and accelerate ROI.

The solution for your wind turbines: CJC® Offline Filters. Achieve highest oil cleanliness for maximum protection of lubricant, gearbox, main bearing and pitch hydraulics — fast, efficient and cost-optimized.


Due to the ever more compact design with simultaneously ever higher power density, the load and, thus, the purity requirement for lubricants is increasing. To ensure high performance and longevity of components, you should use high-quality lubricants with high oxidation resistance and saturation limit for water. However, the quality of the lubricant alone is not sufficient. You can ensure optimum protection for oil and components only by continuously removing the contaminants in the lubricant.

Did you know that

  • 70—80% of all damage occurs due to the impurities in the lubricant?

  • 25 % of all turbine failures occur due to gearbox damage?

  • 67 % of all turbine failures occur due to bearing damage?

  • the bearing service life is 20 % shorter due to abrasion particles caused by micro pitting alone?

Damage and consequences caused by contaminated and rapidly ageing lubricant

Wear in gearbox, oil maintenance in wind turbines
Wear on rolling bearing, oil maintenance in wind turbines

Water and wear particles (Fe, Cu, Al, Zn, etc.) accelerate oil ageing / oil oxidation and thus premature additive consumption — even with synthetic high-performance oils. Additives such as antioxidants, anti-wear and anti-corrosion additives, detergents and dispersants, and acid-neutralizing additives are consumed more quickly the more contaminated the oil. Another accelerating factor for oxidative oil ageing is air bubbles in the gear oil.

During oil ageing, the lubricant’s viscosity and acid content increase. Reaction products are formed, which, depending on the temperature, precipitate out of the oil and are deposited — preferably in load zones, narrow passages and standing areas. This leads to sludge and varnish-like residues on valves as well as in the bearing, inline filter and oil sump. Components in start-stop operation are particularly at risk, as temperatures < 40 °C over several hours cause further failure of the dissolved connections.

Therefore, when caring for oil, you should rely on a solution that removes all impurities: particles, water, oxidation products and acids.

Water enters the oil circuit during fluctuating ambient temperatures (condensation) through defective seals, vents or via the fresh oil due to transfer, storage and handling errors.

Even if your gear oil has a high degree of saturation with respect to water — e.g. polyglycol-based lubricants * — it should be noted that water dissolved in the oil can also be released during temperature and pressure fluctuations and then throughout the entire lubrication and hydraulic system.

As the temperature rises, the risk of vapour bubble formation increases exponentially, which can cause the lubricant film to break off. Pressure fluctuations in narrow contact and friction areas can also cause the vapour bubbles to implode, which in turn causes the lubricant film to break off. This causes metal to meet metal directly, resulting in erosive material removal and micro to macro pitting.

Hydrogen corrosion causes damage to surfaces in the form of rust. At the same time, water intensifies the severity of acid corrosion. Rusty, sharp-edged surfaces are created, resulting in abrasive particles in the oil circuit.

At high-pressure loads, as prevail in the gearbox, hydrogen atoms diffuse into the metal lattice (hydrogen embrittlement). Cracking and material erosion are, therefore, further possible consequences.

When maintaining oil in wind turbines, ensure that your filter system removes dissolved water from the oil.

The entry of particles can generally not be completely avoided. This is because particles enter the oil circuit via the fresh oil, during maintenance work, from the environment (defective seals, ventilation systems) and through wear processes. In particular, hard ultra-fine particles < 5 µm have the potential to cause severe damage through abrasion and fatigue wear.

Wind power gearbox and main bearing:

In the elastohydrodynamic lubrication range, the lubricant film thickness narrows to 0.1 to 1 µm in the load zone. If particles get into this narrow lubrication gap, they are rolled over and lead to micro pitting. The pittings expand further under load, leading to material removal, splinter fracture, and surface chipping. If the main bearing is supplied from the same oil circuit as the wind turbine gearbox, efficient fine filtration of the lubricant is highly advisable. Rolling bearings achieve a significantly longer operating life if all particles that could get into the narrow lubrication gap are removed (source: SKF). Recommended oil cleanliness: 17/15/12 according to ISO 4406 *.

Pitch hydraulics:

In highly sensitive and highly stressed hydraulic systems, pumps, valves and pistons wear out due to even the smallest particles due to tight tolerances. This means that even the smallest particles can cause the entire wind turbine to fail. Recommended oil cleanliness: 16/14/11 according to ISO 4406 *.

When maintaining oil in wind turbines, you should, therefore, pay attention to an appropriate filter fineness so that they can realize these oil cleanliness.

* Source: AGMA, Noria Corporation, Vickers and SKF

Particles, water, and oil ageing cause viscosity to increase and degrade air separation efficiency. Air bubbles in the oil rise more poorly, and the risk of foam increases with insufficient lubrication as a result.

The cleaner the lubricant, the better the air separation capacity.

Existing oil filters in the inline oil flow clog quickly due to low filter capacity and require frequent replacement.

For oil care in wind turbines, it is advisable to use offline filters, as their filter elements are less expensive, have higher dirt-holding capacities, and thus spare the expensive inline filters.

Your solution: efficient oil care

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

  • achieve up to 10 times longer service life for gearbox, main bearing and pitch hydraulics.

  • maximize lubricant life and conserve resources.

  • reduce the maintenance effort and increase the availability of your wind turbines.

  • improve the precision of the pitch setting, and optimize the wind harvest.

  • protect the existing inline filter, which clogs less frequently and requires fewer filter changes.

lower oil consumption, gearbox, main bearing, pitch hydraulics

Less oil consumption

less maintenance required for gearbox, main bearing, pitch hydraulics

Less maintenance

higher availability for gearbox, main bearing, pitch hydraulics

Higher availability

more resource protection, gearbox, main bearing, pitch hydraulics

More resource protection

CJC® Offline Filters for Efficient Oil Care

CJC® Offline Filters meet the specific requirements of onshore and offshore wind turbines. Since the maintenance required for hard-to-reach equipment is enormous and results in more extended downtimes, there is a need for more robust components and filter systems that offer maximum component protection and enable remote monitoring of oil and filter condition. Compact and virtually maintenance-free, CJC® Offline Filters maintain oil in continuous operation (24/7). They achieve the highest oil cleanliness levels in the shortest possible time and offer optimum wear protection.

Installation of an offline filter at a gearbox
cjc depth filter, fine filter, cellulose filter

The dedicated pump unit allows installation in a separate circuit (bypass) and thus continuous depth filtration and maintenance of the lubricant (24/7). The gear pump sucks the lubricant from the lowest point of the gear. The lubricant flows radially through the CJC® Depth Filter Insert from the outside to the inside. The clean lubricant’s return flow occurs without pressure above the oil filling.

The CJC® Offline Filter removes all contaminants:

Wear particles and suspended solids

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

Water – free, emulsified and dissolved

Reduce water content to well below the saturation limit.

Oxidation residues and acids

For long-lasting stable oxidation rate and residual oil life.

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.

CJC® Offline Filters can be optionally equipped with sensors for automatic online filter and oil condition monitoring. Depending on the system selected, up to nine sensors can be selected — whether for oil moisture, oil temperature, particles (4—250 µm), wear particles (0—1,000 µm), oxidation rate, filter pressure and/or equipment utilisation. 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 hydraulic condition due to the high data density.
Our intuitive operable cloud applications have a clearly arranged dashboard to visualise the sensor data. In the Premium version, sophisticated algorithms help you with automated data evaluation and interpretation. Ideal for critical wind turbines where failure quickly has costly consequences. Optionally, the sensor data can be transferred to your own system via various interfaces.

CJC® Offline Filters for Gearboxes, Main Bearings and Pitch Hydraulics

HDU 15/25 for oil care in wind turbines for gearboxes, main bearings, pitch hydraulics

CJC® Offline Filter HDU 15/25

Filtration degree:
3 to 1 < micron

Filter capacity:
Dirt approx. 1.1 kg
Water approx. 400 ml

HDU 15/25 for oil care in wind turbines for gearboxes, main bearings, pitch hydraulics

CJC® Offline Filter HDU 27/-

Filtration degree:
3 to 1 < micron

Filter capacity:
Dirt up to 12 | 24 | 36 or 48 kg
Water approx. 0.9 | 1.8 | 2.7 or 3.6 l

Key Filter for oil care in wind turbines for gearboxes, main bearings, pitch hydraulics

CJC® Key Filter – extra light

Filtration degree:
3 to 1 < micron

Filter capacity:
Dirt up to 12 kg
Water approx. 1 liter

Condition monitoring systems for oil and plant condition monitoring

CJC® Condition Monitoring

Particle counter,
Oil sensors
Cloud applications
for data evaluation

Oil care in wind turbines is essential and so easy — see for yourself

Contact your regional contact now

Let’s start talking: about your wind turbines, your lubricants and the specific challenges. We filter every oil. It does not matter whether you use mineral oil, synthetic or biodegradable oil. We work with you to maximize lubricant, gearbox, main bearing and pitch hydraulic life and provide more wind harvesting.

Get a personal consultation and a no-obligation quote on a CJC® Offline Filter for efficient oil care in wind turbines.

Write or call us.

oil sampling, oil care in wind turbines, gearboxes, main bearings, pitch hydraulics
oil sampling, oil care in wind turbines, gearboxes, main bearings, pitch hydraulics
oil sampling, oil care in wind turbines, gearboxes, main bearings, pitch hydraulics

That say our customers

“After installation of the CJC® Offline Filter in the wind turbines, the gear oil is optimally maintained. In several test setups where we have examined and tested the different filtration options of 3-stage elements, bypass and offline filtration, constant offline filtration provides the best oil care. Via the accompanying oil analyses and also visually, we can see that the oil is significantly cleaner than before. We are very happy with the result and will be installing more CJC® Offline Filters on wind turbines where a significant improvement in oil quality is required.

Download Case Study — Gearbox, GE® 1.5 s

Manager Mechanical Engineer, Vestas (ex Availon GmbH)

“Due to the high efficiency of the CJC® GFU gearbox flushing systems, we not only achieved the required oil cleanliness in the shortest possible time during gearbox flushing but also saved 147 EUR USD per gearbox due to the lower energy consumption.

Download Practice Report — Flushing, Gearbox

Chongqing Gearbox

“Since installing the bypass filters, the trend in our oil analyses has been consistently positive. So far we have not had a single bearing failure on our gearbox, nor have we received any error messages during condition monitoring (vibration and temperature analysis). Operators of wind turbines of the same brand and type from other wind farms in our vicinity have already experienced several bearing failures due to wear caused by particles and had to replace two gearboxes within 2 years. Damage of this type can easily cost over $900,000.

Download Case Study — Gearbox, GE® 1.5 ESS

Manager Wind Energy Technology, North American Wind Research and Training Center