Tagged: lubrication

Used Oil Analysis Tips

“When should an oil sample really be taken?”

In used oil analysis, oil samples can be taken at any time, but one should always consider the insight that they are trying to gain before testing the sample. This is crucial in deciding the type of tests and the intervals at which they should be performed.

For instance, if we are testing the quality of the oil or we want to compare a fresh batch to a used one, then we can take a sample directly from the drum. 

If we are trying to decide the rate at which the additives are being depleted or wear being accumulated then we can take a sample at different operating hours to trend the data. This method can work if we are trying to determine the most appropriate run time for a lubricant in particular conditions.

However, if we are trying to track the health of the components on a regular basis as part of our PM program then taking a sample at the end of the scheduled maintenance interval is desired.

Taking an oil sample from a component is like performing a blood test by the doctor. It helps us to understand what’s really happening. It can show us if there is excessive wear, contamination or lubricant degradation which allows us to identify its “health”. However, the correct tests need to be carried out to determine these conditions.

There must be a reason behind taking the oil sample, not just a random act. When trying to establish a trend regarding a particular aspect of the oil, this should guide your choice of tests otherwise we can end up paying for tests that do not add value.

Always ensure sound reasoning behind testing rather than just checking the box!

While taking an oil sample at the end of the scheduled operating hours is very convenient, is it truly efficient?

When a piece of equipment is scheduled for maintenance, it is usually taken out of service for a couple of hours to perform the assigned maintenance tasks.

However, if an oil sample is taken a couple days in advance of the scheduled maintenance, then when the results return the maintenance team can be on the lookout for issues highlighted by the results.

For instance, if the value for iron was significant or rising then they can perform inspections for areas which may cause this type of wear and address this challenge while the equipment is offline.

Lubricant Deterioration Identifications

There’s a major difference between Shelf life and Service life especially when it concerns lubricants!

No one wants to put expired lubricants into their equipment! This can cause unexpected failures which can lead to unplanned downtime which can continue to spiral down the costly path of unproductivity!

The Shelf life is usually what is stamped by the Manufacturer indicating the length of time the product can remain in its current packaging before being deemed unsuitable for use. These can typically be found on the packaging.

The Service life however is determined by the application and conditions under which the lubricant is being used. Usually, estimated running hours / mileage are given by the equipment manufacturer in the maintenance section of the manual. (Condition monitoring can also be used to determine appropriate service intervals.)

However, how will someone know if the product has deteriorated while still in its original packaging?  What should someone typically look for?

Above are some tips for identification of deterioration in lubricants. Take a note of these for the next time you are unsure of the integrity of your lubricants.

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.

Grease compatibility

We recently touched on greases being available in a wide variety based on application but the real question is, “Are all greases compatible?” The short answer is, “No”.

All greases contain a thickener (which helps with its physical state). Thickeners vary depending on application (such as temperature, water resistance etc). As such, to verify whether two greases are compatible or not, Machinery Lubrication developed a Compatibility Chart based on thickener type.

You can determine the thickener type by looking at your Data Sheet or talking to your OEM. Not all greases are compatible, so be careful when mixing greases!

Grease Thickener Types

We keep speaking about each grease being different based on their thickener type. However, what are the properties that these thickeners give to the grease? For instance, if I wanted to use a grease for a roller bearing in a very high temperature environment which should I choose? Can a multipurpose grease work for that application?

Each area of application may be different and while multipurpose greases are widely used there are some areas where it doesn’t add much value. For example, if a heavy equipment operator uses a backhoe to dig into a river, the multipurpose grease can be easily washed off.

When the grease washes off quickly, the pins holding the bucket can become damaged. (The costs to repair or replace one of these pins are ridiculously high!) However, if he used a Calcium based grease, then there wouldn’t be an issue of water washout and the pins could have a longer life.

Above is a table indicating the various uses of greases based on the thickener types. Know your applications and their environments when choosing the right grease!

Understanding NLGI

Does the NLGI grade matter? Of course it does! That’s why it was invented and classed into different categories for various applications! NLGI stands for National Lubricating Grease Institute, they are composed of companies that manufacture and market all types of lubricating grease.

An NLGI grade can start at 000 (very fluid) to 6 (block like). However, there are different grades for different applications.

For instance, most trucks have a centralized lubrication system. As such, the grease needs to be almost fluid like to get to all the areas. In these cases, a “00” or even “000” grease may be used. However, the most common grade is a “2” grade which is seen frequently in cartridges, pails etc.  Some electric motors require a “3” grade grease instead of a “2”.

Here is a table that describes each of the grades, their applications and consistency.

Always check with your OEM to ensure that the correct NLGI grade is being used! Here is another graphic that likens these grades to more easily identifiable consistencies.

Grease colours

I’ve almost always heard my customers refer to the grease that they are using by its colour. They would say, “I’m using the blue grease.” However, greases are not defined by their colour. Colour is often added to grease to allow it to be easily identifiable within the field. For instance, if a grease is coloured blue, it is easy to identify if it’s leaking or not (one way not to confuse the leak with an oil leak).

Some greases are coloured to ensure that the applicant uses it in the correct application. For example, if a blue grease is a multipurpose grease then this ideally shouldn’t be used in the very high temperature area. Most of the times, red greases are used for high temperature applications. Thus making it easy to identify if the correct grease is used in the right application. However, one should note the colours of the greases being used in their facility and their applications before comparing them to that of another facility (which may be using a different grease manufacturer.)

Don’t define greases by their colours, define them by their applications!

Colour Coding

Quite often when we are correcting or helping companies set up their lubrication storage areas, we get asked a lot of questions regarding colour coding. Ideally, the concept of colour coding is to allow field personnel to easily identify and associate particular lubricants with their applications.

However, like most things in reliability, this can be customized to suit your organization. There are no hard and fast rules of using only yellow to represent hydraulic oils. But, what if we had someone that was colour blind?

Usually, when we start colour coding lubricant storage containers, we include symbols and actual names of the lubricant. This helps to assist personnel in having a 3 point verification system.

First they can verify the colour, then the symbol and of course the name of the lubricant.

Names are crucial! Especially for varying viscosities (such as gear or hydraulic oils). For instance all gear oil would have the same colour and symbol but you wouldn’t want to put an ISO 100 gear oil in a gearbox suited for ISO 680.

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!