How It Works – and Why Clean Oil Is Critical
In aircraft turbine engines, the lubrication system does more than reduce friction. Oil forms an ultra-thin, load-bearing film that enables bearings and gears to operate under extreme speed, temperature, and stress. The survival of these components depends on the integrity of this oil film.
Oil viscosity increases dramatically under rolling pressure, creating a continuous oil film that fully separates metal surfaces. Because the oil film is only a fraction of a micron, even microscopic foreign object debris (FOD) can disrupt it. A disrupted oil film means metal to metal contac,t causing immediate surface damage.
Understanding how the oil film works—and the limits of oil filtration—is essential to appreciating why oil cleanliness is one of the most critical factors in turbine engine reliability.
Typical turbine engine bearing oil film is ultra-thin at a mere 0.05 to 0.5 μm (Micron). With normal oil filtration capability of approximately 15 μm (Micron) and up to as much as 40 μm (Micron) during oil filter bypass events, the risk of bearing damage is extremely high if you keep adding dirty FOD laden oil at top up or oil change.
For comparison a human hair is around 70 μm, so damaging particles will be hard for anyone to see. This is why you need to absolutely sure oil fillers and oil can openers are clean, and no handling process is adding FOD to the oil. It will most likely go unnoticed.
The Oil Film Performs Several Functions:
- Prevents metal-to-metal contact
- Carries mechanical load
- Reduces friction and heat
- Removes heat from bearings and gears
- Flushes wear debris away
- Protects surfaces from corrosion
When the Oil Film Collapses:
- Surface distress
- Micro pitting
- Smearing and scuffing
- Rapid fatigue initiation
In turbine engines, bearing damage often begins with localized oil film breakdown due to FOD.
Oil FOD is the fundamental threat to oil film. Any particle larger than the oil film’s thickness will penetrate the film and cause an over roll of the particle, resulting in dented or damaged bearing surfaces.
Once a dent forms, the oil film collapses repeatedly at that same location with metal-to-metal contact increasing stress concentration and eventually initiating fatigue and corrosion. Damage will propagate long after the original particle is gone. Even very small debris can cause very large areas of failure due to spalling.
This is why oil cleanliness matters so much. Oil film thickness is smaller than the oil filter capture size, so filters cannot be solely relied on to prevent bearing damage. You simply have to stop introducing FOD to your oil system by taking oil handling very seriously.
Put oil handling cleanliness in focus in your organization – from pilots to maintenance personnel. FOD prevention in oil systems is a proven money saver. Clean oil extends bearing and engine life.
TheCanKey FOD-Free Oil Can Opener
TheCanKey is the only FOD free oil can opener on the market. It is tested and certified by Saybolt Laboratories not to leave any debris whatsoever in the oil can during the opening process.
Use TheCanKey turbine oil can opener to ensure not to introduce FOD to your oil system when servicing or filling oil. It is an easy, proper and effective way to prevent FOD. Using TheCanKey FOD free oil servicing tools will ultimately save costs and improve overall safety and performance of the gearbox.
