Hydraulic Oil Contamination



particle size chart


The cleanliness of your hydraulic fluid is critical to the trouble free and cost effective operation of your system. Hydraulic components are very expensive and need special consideration when selecting and filtering this fluid.

ISO 4406 (International Standards Organization) code is a standard that is recognized in the industry. Certain recommended fluid cleanliness quantities are necessary to realize the best performance and cost saving operation of your hydraulic system.

The ISO 4406 cleanliness level standard is used to reference the number of particles greater than 5 and greater than 15 microns in a known volume. For our usage, this volume will be 1 ml. The number of 5+ micron particles is used as a reference point for "silt" particles. The 15+ size range indicates the quantity of larger particles present, which contribute greatly to potential catastrophic component failure.

Now, the way the ISO chart lists the "ISO Code" is with a two number system. For example, the approximate rating of new oil off the store shelf would be rated at 20/17. In this two number system, the first number indicates the number of particles that are greater than 5 micron in size. The second set of numbers after the / indicates the number of particles that are greater than 15 micron in size.

Ideally, the lower you can get the two numbers in the ISO chart, the less will be the internal damage inside your engine or hydraulic system.

To ensure that you achieve the most efficient and relative results, it is important to establish and maintain an oil analysis program.