What is oil degradation?

Oil Degradation


oil-degradationThe function of lubricants is to remove contaminants, reduce friction, improve efficiency, minimize wear, and distribute the engine’s heat. Lubricant degradation occurs throughout the service life of the lubricants, depending on the oil type, the temperature, the operational conditions, and the environment. The baseline for change occurs when further deterioration leads to a level whereby the lubricant can no longer protect the system. When oil degrades, it changes composition and functional properties, and unwanted products are formed: acid compounds, soft contaminants (also called sludge/resins (dissolves in warm oil)), and varnish (deposit formation).

Oil conditions are to be monitored regularly to make sure the oil is used within its performance specification. Oil degradation products (or soft contaminants) are widespread problems in most industries. They are precursors of deposits, often referred to as varnish. Varnish is known to cause issues in hydraulic and lube oil systems. Varnish products form a sticky layer on metal surfaces and will easily block fine tolerances. Hard particles of all sizes get caught in the sticky layer, creating a sandpaper-like grinding surface, which radically speeds up machine wear.

Varnish can be dissolved, insoluble, or cured, and its state is very dependent on the temperature and contact with air:
–  Varnish is dissolved in its base fluid (for example, mineral base oil).
–  Varnish will precipitate out immediately when it becomes insoluble (the portion above the saturation point at a given temperature).
–  Varnish is cured and no longer solvable with its base fluid when in contact with air/oxygen or “baked” on hot surfaces (for example, lacquer on cylinder liners in diesel engines).

The fluid temperature has a huge impact on almost any given solubility. The “varnish generating spots” are usually the “hot spots,” while the “varnish deposit spots” are usually the “cold spots.” 

Varnish has many consequences within your hydraulic or lube oil system. Valve sticking causes loss of control. Varnish causes filter plugging and restricts oil flow. The “sandpaper surface” increases component wear. Varnish causes ineffective cooling (poor heat transfer), increasing the oil temperature. The lacquer baked onto bearings causes poor flow, increasing temperature, and vibrations. All of these lead to a loss in equipment availability, loss in revenue, frequent oil changes, and increased maintenance costs.


How can you identify oil degradation?


Top Six (6) Lubrication Degradation Modes

–  Loss of antioxidants
–  Producing varnish, sludge, and sediment
Thermal Degradation (Thermal Breakdown):
–  Increase in temperature over 200°C
–  Producing coke (carbon deposits)
–  Entrained air – antifoaming property
–  Producing varnish, carbon insoluble, soot, sludge, tars, coke, and resins
Electrostatic Spark Discharge:
–  Increase in conductivity of the oil
–  Producing varnish, sludge, or insoluble materials
Additive Depletion:
–  Loss of additives
–  Producing deposits
–  Foreign particles present
–  Producing various deposits

Many causes can accelerate the oil degradation process. The key is to remove oil degradation products before they have the time to react further and form insoluble sludge and varnish deposits. An oil system free of varnish deposits has a longer oil life, increased oil performance, lower energy consumption, increased productivity and uptime, less maintenance and breakdown, maintained additive performance, maintained oil viscosity and acidity, and is environmentally friendly.


What are the varnish removal methods?

1. Physical Filtration (including absorption and adsorption)
      – Depth cellulose filters
      – Electrostatic filters
      – Balanced Charged Agglomeration (BCA)
2. Chemical Filtration – Cartridges with chemical bead compositions of different mixtures that are adjusted for increased efficiency on different oil brands and machine types.
3. Depth Filter Absorption/Adsorption with advanced varnish agglomeration – Systems that effectively precondition the oil so that all soft contaminants fall out of solution, agglomerate, and are removed by depth filter inserts with high dirt holding capacity.  


Which of the three (3) different methods should you choose to remove varnish?

This entirely depends on the efficiency of the system in different applications. Systems with oil operating temperatures around 40°C (100°F) and below can be treated with any of the above removal methods. Systems with oil operating temperatures of 40°C (104°F) and above can also be treated but are more difficult as the solubility and varnish ‘production’ increases. Another factor is runtime vs. downtime, which affects varnish removal. As the oil cools down and you continue running the filter, it will collect anything coming out of the solution. 

Oil Degradation Solutions: Oil Degradation Treatment

–  The CJC Fine Filter and Filter Separator retain varnish if the oil temperature gets below 40°C (104°F).
–  The CJC Varnish Removal Unit (CJC VRU) is designed for the removal of varnish and soft contaminations – dissolved and in suspension (oil temperatures always +60°C (140°F)). 

The right solution for your application!

Oil degradation can negatively affect your lubricating oil and hydraulic oil systems. Keeping the oil as cool as possible may increase lube oil life and reduce thermal breakdown. Need to slow down the degradation process in your oil reservoirs? We can help significantly increase equipment uptime. Contact us today for oil degradation and varnish removal case studies! 

To learn more about clean lubricating oil, visit our Clean Lubricating Oil will Maximize Equipment Lifespan blog.
To learn more about hydraulic oil cleaning, visit our Comprehensive Guide to Hydraulic Oil Cleaning blog.


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