Tagged: iso4406

Stop production?


I can’t shut down the equipment but I know the oil has degraded significantly. What can I do?

Tough decisions!!!

There are times when production cannot be stopped such as when an order has to be fulfilled in a manufacturing facility. Before a decision is made, we need to understand the risks of not stopping production.

Can prolonged production cause a reduction in the overall quality of the final product or will it damage the equipment from working outside of its stipulated hours?

If we absolutely cannot shut down the equipment but the quality of oil has degraded, we need to firstly understand why the oil is degrading (especially if this is outside of its regular working hours).

Next, we need to identify which property of the oil has degraded, is it that the viscosity has increased / decreased, or the antioxidant levels have depleted significantly? By identifying the property that has degraded, we can choose the best way of replenishing this property.



There are a few methods that can be employed when trying to get the lubricant back to a healthy state however, as indicated above it is dependent on the property that has been degraded.

Cleanliness – if the ISO 4406 value has been increasing significantly this can hamper the performance of the lubricant. The clearances that the lubricant has to pass through can become blocked or the surfaces can experience an increased rate of wear.

One simple method of improving the cleanliness is through a kidney loop filtration system. This is an external system where the oil can be filtered through a filter cart and returned to the system.

Usually, this is a very effective method but one should investigate why the cleanliness values have become so high. Is it that the lubricant is being contaminated by the system, a process within the system or external factors?


Antioxidant levels – usually in turbines, this value decreases quickly especially if there is the presence of oxidation. Some users try to add antioxidants to their lubricant to increase the values. This is NOT recommended!!!

The composition of most turbine oils is 1% additive, 99% base oil. By adding any additive directly to the lubricant, we will be throwing the lubricant off balance and may induce other issues such as coagulation (clogged clearances) if the additive did not react well to the initial additives in the lubricant.

One of the easier ways of increasing the antioxidant levels without shutting down the machine is referred to as sweetening.

This process involves removing a percentage of the used oil (lubricant in the system) and then refilling the sump with new lubricant. The ratios can vary depending on the desired change in the antioxidant levels. It is important to note that the same lubricant should be used to ensure compatibility of the lubricants during the sweetening process.

Additionally, lab tests should be done frequently to monitor the changes in the antioxidant levels. The frequency of lab tests is highly dependent on the result turnaround time and budget available.


ISO 4406

A lot of people get confused when reading the ISO 4406 rating. The rating specifies a range of the number of particles of certain sizes that can pass through 3 particular sized filters namely; 4micron, 6 micron and 14 micron filters respectively.

For instance; a rating of 13/11/8 indicates:

  • 13 represents 4000-6000 particles over the size of 4um
  • 11 represents a range of 1000-2000 particles over the size of 6um and
  • 8 represents a range of 130-250 particles over the size of 14um.

These values are actually the number of particles per milliliter. It does not mean that you have 13, 11 or 18 particles only in your oil, it's much more than that!

There are different ratings for different levels of cleanliness.

If your numbers are really high (25/22/19) then there’s definitely a high level of contamination!

Different components have different ISO cleanliness ratings. For instance, a roller bearing has a higher cleanliness target than a Variable Vane pump.

Understanding the ISO 4406 codes are crucial for determining the steps needed in “cleaning up” your system lubricants.


However, when we test for the cleanliness of an oil, there are a couple things that we need to consider:

  1. When testing, we have exposed the oil to the elements (highly dependent on the method of sampling)
  2. Results are not instantaneous (even with an onsite lab, there will be a timeframe between collecting the sample and processing it)


Since there are lag times involved, the value that is reported for the ISO4406 rating is never really truly representative of the oil. As such, when analysing the results of this test, it is important to consider that the actual value may potentially be higher than reported.


Matt Spurlock CLS, CMRP, MLE explains further about redefining the ISO code in his article entitled; "A Twist on Particle Evaluation: Redefining the ISO Cleanliness Code".