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In the first part of this series, What’s Dirt got to do with it? – Part 1: What is Contamination?, we got into the specifics of contamination and how it can be classified. For this part of the series, we will focus on being able to identify and prevent contamination. Ideally, lubricants can become contaminated easily, however, we need to be able to determine the tolerance levels that our systems can endure. For instance, the solid contamination tolerance in a diesel engine will vary greatly from that of a hydraulic system (with tighter clearances).

Ways to identify contamination

There are a couple of lab tests which can identify contamination but sometimes, you don’t need to wait until you get to a lab to confirm whether contamination has occurred or not. It may be visible in the oil (via a change in color or appearance) or even in the smell of the oil (strong odor where none previously existed).

The lab tests associated with contamination include:

• ISO 4406 – count of particles in the oil which fall within ranges of >4, >6, >14 μm per milliliter of fluid
• PQ (Particle Quantification) counting – the measure of iron in the oil
• NAS 1638 Rating – measures the particle count but is considered obsolete. This used to measure the particles within the ranges of 5-15, 15-25, 25-50, 50-100 and >100μm
• FTIR – identifies the presence of molecules and their concentrations

The ISO 4406 standard uses the following table to classify the ranges in which the volume of particles falls.

For an ISO code of 20/15/13 this represents:

• 20 – between 5,000 – 10,000 particles larger than 4μm in one milliliter or fluid
• 15 – between 160 – 320 particles larger than 6μm in one milliliter or fluid
• 13 – between 40 – 80 particles larger than 14μm in one milliliter or fluid

One can imagine how quickly those numbers can escalate! However, while this provides a good indication of the particles present, when trending over a period of time, it can be a bit misleading especially if the number of particles remain within the larger ranges.

For instance, if the raw results look like the table below, there will not be a change in the ISO 4406 code although there has clearly been a decrease in the number of particles.

Preventing contamination

With all the various types of contamination which exist, there are also quite a few methods to minimize their ingression to the oil. These include storage and handling for the oils coming into the equipment and methods of filtration for the oils already in the equipment.

When oils are received into the facility, they are not super clean. It is worthwhile verifying with your oil supplier about the cleanliness of your oil. Typically, oil suppliers should have a cleanliness level test completed before the packaging of the oils which is available per batch of oil. Since this is typically done before packaging, it would be a good idea to test the cleanliness of the oil after it is received at your facility to determine its true rating.

If oils are to be decanted from their original packaging into the sump of the equipment, then there are lots of opportunities in which these can become easily contaminated. Some strategies to consider:

• Utilize sealed, dedicated containers for the oil transfers. These can prevent the oils from being contaminated by gases, liquids (other oils) and solids. The containers should be dedicated to each oil type to avoid mixing of the oils. For instance, the oil container used to decant engine oil should never be re-used to decant hydraulic oil!
• When topping up sumps, be careful with opening hatches as these may have accumulated solid particles on them and these can easily fall into the sump leading to contamination.
• Store oils in a cool, dry place, not outside in the elements. Oil Drums can breathe and pull in accumulated water through their bungs essentially contaminating the oil before it reaches the equipment.
• If hoses are used to transfer oils, ensure that these are capped after use to minimize ingression of solid particles. Also ensure that these are properly labelled so the correct lubricant is placed in the associated sump.

For those oils already in the system, many times there are system filters which can catch some internally generated particles. It is a good idea to monitor these and trend the rate at which the filters are changed (if they are only changed when the differential pressures accumulate to a certain level). This can give an idea of the estimated rate of contamination in the system oil.

Additionally, if one of the oil analysis tests shows the presence of water, then there are a few filtration techniques which can be employed depending on the concentration of the water in the system.  Some methods include; Gravity Separation, Centrifuge separation, Polymer Absorption, Vacuum Dehydration and Air stripping Dehydration. Fitting equipment with desiccant breathers is a preventive measure which can be taken as well.

Now that we can identify contamination and have found some methods to prevent it, we need to look at how much it is actually costing us by having contaminants in our system. Look out for the last part of the series where we discuss this.

Thank you Sanya Mathura with Strategic Reliability Solutions Ltd for sharing this informative and educational series article with us!

Download our Oil & Grease Storage Best Practices Infographic for some tips to help outline the best practices for proper lubrication storage!

Contamination Impacts Equipment Reliability