ISO 11171 Standard
Hydraulic Power Systems and Liquid Particle Counter Calibration
Fluid cleanliness is a key reliability factor when it comes to hydraulic and precision bearing systems. Dirt accumulation and oil degradation increases with equipment use resulting in silting, gumming and abrasion of parts. Considering the relationship between oil cleanliness and component life, the cleaner the system, the longer the life of the oil and wetted parts. An increase in particle count (above baseline) indicates an increase in contamination. ISO standards were developed as standards for fluid cleanliness monitoring.
ISO 11171 was introduced in 1999 to simplify the reporting of particle count data by converting particle count results into classes or codes. This change occurred as a result of the introduction of ISO MTD (Medium Test Dust) as a replacement for ACFTD (Air Cleaner Fine Test Dust) in fluid suspensions used to calibrate optical particle counters. This international standard and subsequent modifications define the requirements for particle counter calibration and data reproducibility covering flow rates, resolution coincidence error and sensor/volume accuracy, while ensuring all instruments are calibrated to the same NIST traceable standards.