Tagged: oil

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.

Base oil viscosity of greases

While we’ve focused on the variances in greases due to thickener types, we haven’t touched much on the differences in base oil viscosity.

With gear oils, we need the correct viscosity to allow the gears to turn at the required rate while still being lubricated. If the oil is too thick and the gears are high speed, then the gears will not be lubricated quickly enough and they can become damaged. Similarly, greases are made up of base oil with different viscosities.

Most greases use a viscosity of 220cSt (these are the multipurpose greases). However, greases for electric motors use a base oil viscosity of 100cSt. What’s the difference?

Well, if a multipurpose grease was used for an electric motor the energy used for that motor can be 100W however, if a grease with a base oil viscosity of 100cSt was used, the energy used could be reduced to 70W. Is this significant? Definitely YES!!!

On any manufacturing plant, there are at least 5 – 10 electric motors, in some cases there are 70 or more! If at least 25W were saved per motor per month then the company can a significantly reduced power bill at the end of the year!

Understand your applications before applying “any” grease!

Lubrication Audit?

Audits usually get people nervous! They are worried about what the auditor may or may not find. When we perform lubrication audits, we’re trying to ensure that your equipment is using exactly what it should to perform efficiently.

Why is that necessary? We’ve found that in most organizations, there may have been a time when the OEM recommended lubricant was not readily available and a substitute was used instead. Once the substitute has been used, it magically becomes the recommended lubricant for the rest of the life of the component.

However, if proper checks were not done initially, then the component could be using the wrong lubricant for most of its life. This can contribute to downtime and replacement of parts before their actual useful life has been reached.

Once, we found a gearbox using an ISO 680 gear oil when it should have used an ISO 320 oil. This gearbox used the wrong oil for 30 years! It greatly impacted the efficiency of the gearbox and they experienced numerous breakdowns throughout its life but they never understood or dared to look at the lubricant.

Always ensure that you have the OEM recommended lubricants for your components!