For an ISO Code of n/X/X, what does the second number represent?

The ISO Code in the format of n/X/X provides a standardized way to express the cleanliness of hydraulic fluids and lubricants by detailing the contamination levels represented by particles of various sizes. In this code, the second number specifically denotes the particle count per milliliter for particles in a particular size range, typically between 5 and 15 micrometers, which is referred to as the second middle size particle count/ml. This distinction is crucial for assessing the cleanliness of the fluid and understanding its potential impact on equipment performance and reliability.

In the context of fluid management, recognizing the levels of different sizes of particles is essential, as they can affect machine operation and longevity in diverse ways depending on their size. The second number in the ISO Code allows professionals to evaluate whether the fluid meets industry cleanliness standards and helps determine appropriate maintenance strategies or filtration requirements.