Trucking Hydraulic Fluid Analysis

Particulate contamination is the leading cause of machinery failure.   Uncontaminated hydraulic fluid will ensure continuous operation and help to avoid schedule interruptions.  Hydraulic system failure will often require the removal equipment from a truck fleet causing unscheduled downtime.

The cleanliness level of hydraulic fluids is determined by particle count.  The particle count test measures solid particle contaminants in the fluid sample.  Particle counts can be measured in accordance with various industry standards.   There are two rating systems that define fluid cleanliness: National Aerospace Standard (NAS 1638) and International Standards Organization (ISO 4406).

The NAS 1638 standard classifies the particle size into five distinct groups that include:

• 5 to 15 microns
• 15 to 25 microns
• 25 to 50 microns
• 50 to 100 microns
• >100 microns

NAS 1638 categorizes contamination levels ranging on a scale from 0 to 12 (dirtiest) based on the number of particles per 100mL of fluid for each of the categories above. 

ISO 4406, rates particles in three size classes instead of size ranges:

• >4 microns
• >6 microns
• >14 microns

The ISO code classifies contamination levels using three numbers, each of which represents a contaminant level based on the number of particles per 1mL of fluid for the corresponding size class (respectively larger than 4 microns, larger than 6 microns and larger than 14 microns).

Clark provides particle size testing in accordance with ASTM D6595. Particle count analysis includes the following test package. In addition to particle count, other typical test packages for hydraulic fluid include physical properties, wear properties oxidation/corrosion and moisture. The minimal cost of hydraulic fluid testing compared to the expense of equipment failure is a simple business case. 

Recommended Test Package Includes:

ASTM D445 - Viscosity

ASTM D974, D664 - Acid Number

ASTM D4377 - Karl Fischer

ISO 4406 - Particle Count

ASTM  E2412 - FTIR

Wear Elements & Containments (Spec, XRF, ICP)

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