Tagged: oxidation

Conditions that affect lubricants

How are your lubricants currently stored? Are you storing lubricants under the correct conditions? What conditions affect lubricants?

These questions have come up a dozen times during audits and countless warehouse meetings. To answer these questions, there are five main conditions that can affect lubricants. We have detailed them below along with the effects of these conditions on the lubricant.

  • Temperature – if incorrect can lead to oxidation. For every 10C rise in temperature above 40C the life of the lubricant is halved.
  • Light – too much can lead to oxidation especially for light sensitive lubricants such as transformer oils. Hence the reason that most packaging is opaque.
  • Water – this usually works with additives to cause their depletion or contamination of the product. Water in any lubricant is bad (especially for transformer oils as they are involved in the conduction of electricity.
  • Particulate contamination – contamination can occur by air borne particles if packaging is left open or if dirty containers/vessels are used to transfer the lubricant from its packaging to the component.
  • Atmospheric contamination – this affects viscosity and promotes oxidation and can occur if packaging is left open. For instance, if a drum is not properly resealed or capped after usage or the most common practice of leaving the drum open with the drum pump on the inside.

Different types of lubricant degradation

Why is it important to know the types of lubricant degradation? It’s important since it helps us to figure out why or in some instance how, the lubricant degraded! Usually degradation is the change that occurs when the lubricant can no longer execute its five main functions:

  • the reduction of friction
  • minimization of wear
  • distribution of heat
  • removal of contaminants and 
  • improvement of efficiency.

There are 6 main types of Lubricant Degradation as detailed below. Each type produces various by products which can enable us to understand the reason for the degradation and eliminate that / those reasons.

Here are the 6 main types of Lubricant Degradation:

1. Oxidation
2. Thermal Breakdown
3. Microdieseling
4. Additive Depletion
5. Electrostatic Spark Discharge
6. Contamination

As discussed above, each mechanism produces distinct results which help us in their identification! Check out our article on why lubricants fail for more info!

Oxidation

One of the major types of oil degradation is Oxidation. But what is it exactly, as applied to a lubricant?

Oxidation is the addition of oxygen to the base oil of the lubricant to form either of the following:

  • Aldehydes
  • Ketones
  • Hydroperoxides
  • Carboxylic Acids

Wow… too many chemical names right?! These help to pinpoint the conditions responsible and then we can address them accordingly. Each of these by products are produced by different types of reactions or in some cases different stages of the oxidation process. It is key to note the type of by product as it gives us a clue to the root of the issue through which oxidation occurs.

For instance, the presence of Carboxylic acids can result in the formation of Primary Amides which can lead to heavy deposits. Early detection of the Carboxylic acids can help us prevent this. Once we determine the source of oxidation to produce the carboxylic acids, we can in turn remove this from the system.

Oxidation Stages

Oxidation does not happen in an instant. Usually, it follows a series of events which eventually lead to oxidation. Like any process in life, there are different stages for Oxidation:

  • Initiation – Production of the free radical via the lubricant and catalyst.
  • Propagation – Production of more free radicals via additional reactions
  • Termination – Continuation of oxidation process after the antioxidants have been depleted or the antioxidant stops the oxidation process.

Results of Oxidation

Why is Oxidation bad for the lubricant? What can it ultimately result in?

Well, oxidation can result in the formation or lead up to the following:

  • Varnish
  • Loss of antifoaming properties
  • Additive depletion
  • Base oil breakdown
  • Increase in viscosity
  • Sludge

None of these are good for the lubricant!!!!!!!!! If you see any of these signs be sure to test for oxidation and identify the root cause for the introduction of oxygen in your system.

Oxidation Tests

Now that we know more about oxidation… what tests can be performed to prevent it?

There are 6 main tests that can be performed:

  • RPVOT (Rotating Pressure Vessel Oxidation Test)
  • RULER (Remaining Useful Life Evaluation Routine)
  • MPC (Membrane Patch Calorimetry)
  • FTIR (Fourier Transform Infrared)
  • Colour (ASTM D1500)
  • Acid Number (ASTM D974)

One must be careful in selecting which test to apply, this is heavily dependent on the type of lubricant and its application.

For instance, if we perform the RULER test and the antioxidant levels have depleted significantly, we can suspect that oxidation is occurring or has stopped. Charting the rate of antioxidant depletion, can determine the rate of oxidation. This can assist us to forecast the time remaining before antioxidants have been depleted and can no longer protect the base oil.

Thermal Degradation vs Oxidation

What’s the difference between Thermal Degradation as compared to Oxidation of a lubricant?

The two major differences are the contributory factors and the by products that are produced.

For oxidation, both oxygen and temperature are critical to the degradation of the lubricant however, in thermal degradation, the temperature of the lubricant exceeds its thermal stability (usually in excess of 200°C).

Oxidation usually occurs through the release of free radicals which deplete the antioxidants however, Thermal Degradation consists of polymerization of the lubricant.

Oxidation produces aldehydes, ketones, hydroperoxides, carboxylic acids varnish and sludge. On the other hand, Thermal Degradation produces coke as the final deposit.