Hydraulic Fluid Analysis

Condition Monitoring India

Hydraulic fluids are expected to perform better and provide greater protection under tougher working conditions. The range of equipment that might use hydraulic fluids includes industry machinery, excavators and backhoes, hydraulic brakes, power steering systems, transmissions, garbage trucks, aircraft flight control systems, and lifts.

Unlike other lubricants, hydraulic fluid can have dual purposes, as lubricant and power transfer device. Hydraulic systems are crucial components working under tight tolerances and high pressure, so accurate fluid monitoring is an essential component to maintaining equipment health.

Important Fluid Qualities

Like other lubricants, hydraulic fluid must have following properties:

  • Foaming resistance
  • Air release
  • Thermal, oxidation, and hydrolytic stability
  • Anti-wear performance
  • Filterability
  • Demulsibility
  • Rust and corrosion inhibition
  • Viscosity at appropriate lubricating film thickness

To be most efficient, hydraulic fluid must have high bulk modulus (inherent in base oil and can’t be improved with additives) and high viscosity index (low rate of change in viscosity with temperature).

Major Sources of Problems

Of oil-lubricated assets, hydraulic systems are among the most sensitive to contamination and need to be closely monitored. In fact, 80-90% of all hydraulic failures are caused by poor fluid condition.

Water is the top contamination threat to hydraulic system health. It can cause chemical and physical changes in hydraulic fluid. Water is the leading cause of vaporous cavitation. Water breaks down additive packages, which can lead to acidification and corrosion or oxidation. In idle systems, the water supports microbial growth, which produces sludge and slime. Water can decrease hydrodynamic film thickness, increasing surface contact and component wear.

  • Contaminants: Water, air, foam, and particulate contamination can drastically change the hydraulic fluid’s properties both physically and chemically, resulting in accelerated wear and damage to the fine tolerances of valves, motors and actuators.
  • Wear Metals: Wear metals from pumps and other components can damage and affect the operation of your precision hydraulic operated machine or press.
  • Heat: Excessive heat can lower viscosity too much and potentially shorten the life of your hydraulic oil and alter its performance. Higher temperatures and greater temperature differentials can produce condensation, leading to water contamination. Higher temperatures also increase TAN and oxidation.

Our hydraulic fluid analysis programs will monitor oxidation (via metal wear, particle count, and viscosity) and contamination.

Hydraulic Oil Standard Advanced
Wear Metals
Viscosity (100˚ C)
Viscosity (40˚ C)
FTIR (Fuel Dilution, Soot, Glycol,
Oxidation, Nitration, Sulfation)
Water %
TAN (Total Acid Number)
TBN (Total Base Number)
Particle Count