Neilson Hydraulics


The Difference is Clear

How do I know the level of Contamination?

Easy, contact us and we will arrange for an oil test to be performed on site to show you instantly to what level and what type of contaminants are present in your oil. The oil checker kit used is also available for sale should you wish to perform this test within your own maintenance schedule.


Contaminant checker

  • Checks dirt by a membrane filter
  • Checks water by electric heater
  • Compare dirt and cleanliness with colour photo sample


Example of differing oil cleanliness standards:

  Sample 1 Sample 2 
ISO 4406 15/12   15/12
NAS 1638  6  6
Gravimetric test ASTM F
313-78 0.8µ membrane
 h  h
Contaminant level

By looking at the ISO and NAS grades for each sample you would believe that both are clean. If this is the case, then why does a servo valve fail in one of the systems.

The answer is not in the ISO or NAS grade, but in the gravimetric test, which shows sample 1 to be heavily contaminated with high levels of oxidation, also evident by the build up of deposits on the valve itself.

Oil in sample 2 is very clean and has been acheived by the use of an ELC unit.