Why is Oil Analysis important?

  • Oil Analysis

Why is analysis so important?

Contamination can either come from external sources (ingestion) or are generated from within (ingression). New systems often have contaminants left behind from manufacturing and assembly. Unless they are filtered as they enter the circuit, both the original fluid and the make-up fluid are likely to contain more contaminants than the system can tolerate. Systems can ingest contaminants through components such as worn cylinder rod seals. Furthermore, airborne contaminants can be a problem during routine maintenance, as well as friction and heat producing contamination internally.

The size of the contamination can vary from the size of a grain of salt, down to those undetectable by the human eye.

 Whether by the direct mechanical action between the contaminants and the system components or by the contamination acting as a catalyst to accelerate oxidation of the fluid, prompting chemical breakdown, contamination can cause serious equipment failure.

Even if no immediate failure occurs, contamination can dramatically decrease operating efficiency.

Contamination can accelerate component wear, which in turn leads to inefficient operation, seizure of parts, higher fluid temperatures, leakage and loss of control.

Analysing the oil will indicate how the system is performing, prompting proactive maintenance to ensure performance and reliability. Samples taken initially will provide a benchmark and further routine samples will ensure the oil is in top condition and provide early warning of abnormalities so preventative action can be taken.

How often should I take samples?

When to sample and what results to look out for will be entirely dependent on the application and the Target Cleanliness Level (TCL) of a system.

The below table gives an indication of how often you should aim to analyse your oil, depending on the TCL.


The hydraulic system that you are taking the sample from will determine how clean the oil should be. For example, a critical hydraulic application should return a sample of X/17/14 to be deemed as suitably clean for the application. Each system will have its own TCL but for an indication on cleanliness levels, please see below table.




What is the correct way to take a sample?

According to machinery lubrication, it is best to take a sample from the return line before passing through a return filter. For the powerful hydraulic applications that are running regularly at high pressures, secondary sampling points around the hydraulic components are recommended. This will allow the service engineer to diagnose accurately where the build of debris/particulate contamination is.

What should I look out for when looking at the cleanliness of oil?

As we know, particulate contamination is one of the main reasons for system failure, monitoring the level of hard contaminants is vital. ISO 4406/1999 is a method for classifying the level of contamination of solid particles which converts a particle count into an ISO class. Checking the ISO code is in line with your systems’ required cleanliness is the first step.

It is also important to remember to check for water contamination in the oil. Water contamination can cause a whole host of issues from oxidization and component rusting to depleting additive packages. The majority of oils have a maximum allowable water content level and problems start to occur over this level. More information on moisture sensors can be found here


What does the ISO code mean?

The ISO cleanliness code measures the purity of your oil in three particulate sizes measured in microns:  4-micron, 6-micron and 14-micron. Each number displays the contaminant level for the specific particle size. So for instance, a sample of 18/17/15 would indicate that there is 18 samples of 4-micron particle sizes, 17 samples of 6-micron sizes and 15 samples of 14-micron sizes. Every time this number increases the particulate contamination is gradually degrading the oil and if not treated could lead to costly downtime, wear and tear of hydraulic components and even a complete shutdown of the hydraulic system.

It is important to remember that the more regularly you take samples and analyse your oil the more likely you are to identify contamination issues and take action to prevent unnecessary machine wear and save costs.

Filtertechnik offer a range of analysis options, from laboratory sample analysis to particle counters, both inline and portable. Please click here for more details http://www.filtertechnik.co.uk/catalog/products/quality-control-instrumentation or simply call our technical sales team today on: 0115 9003600