Dewatering Hydraulic Fluid Causes Consequences and Restoration Methods

[MikePhua]

Why Water Contamination Happens in Hydraulic Systems
Hydraulic fluid is engineered to transmit power, lubricate components, and dissipate heat. Its performance depends on maintaining chemical stability and physical purity. Water intrusion—whether through condensation, seal failure, or improper storage—compromises all three. In open-loop systems or equipment exposed to weather, water can enter via breather caps, reservoir vents, or even during fluid top-offs with contaminated containers.
The most common sources of water contamination include:

• Condensation from temperature cycling
  
• Rainwater ingress through damaged seals or caps
  
• Pressure washing near hydraulic components
  
• Leaky coolers or heat exchangers
  
• Improper fluid handling and storage practices
  

A contractor in Alberta left his excavator parked for two weeks during a freeze-thaw cycle. When restarted, the boom moved sluggishly and the fluid appeared milky. Lab analysis revealed 1.2% water content—well above the acceptable threshold.
Effects of Water on Hydraulic Fluid and System Components
Water contamination leads to a cascade of problems:

• Reduced lubricity causing accelerated wear
  
• Corrosion of internal surfaces and valves
  
• Formation of sludge and varnish from additive breakdown
  
• Cavitation and pump damage due to vapor bubbles
  
• Filter clogging and reduced flow rates
  
• Emulsification leading to cloudy or milky fluid appearance
  

Even small amounts of water—less than 0.1%—can degrade fluid performance. Emulsified water is especially dangerous because it’s harder to detect and remove. Free water settles at the bottom of reservoirs, while dissolved water remains invisible but still harmful.
A technician in Chile replaced three hydraulic cylinders after discovering pitting and rust inside the barrel. The root cause was long-term exposure to emulsified water in fluid that had never been sampled or filtered.
Detection and Monitoring Techniques
To assess water contamination:

• Visual inspection for cloudiness or milky appearance
  
• Crackle test using a hot plate to detect vapor release
  
• Karl Fischer titration for precise water content measurement
  
• Dielectric sensors for real-time monitoring
  
• Fluid sampling and lab analysis every 500 hours or quarterly
  

Acceptable water content varies by fluid type:

• Mineral-based hydraulic oil: <0.05%
  
• Synthetic fluids: <0.02%
  
• Fire-resistant fluids (water glycol): up to 40% by design
  

A fleet manager in Texas added inline moisture sensors to his loader fleet. When readings exceeded 0.08%, he scheduled fluid replacement and filter changes, reducing pump failures by 30%.
Dewatering Methods and Restoration Strategies
Once water is present, removal depends on its state—free, emulsified, or dissolved. Common dewatering techniques include:

• Gravity Separation
  • Letting fluid settle in a tank and draining water from the bottom
    
  • Effective only for free water
    
  • Requires downtime and large reservoir capacity
    
• Centrifugal Separation
  • Spinning fluid to separate water by density
    
  • Works for free and some emulsified water
    
  • Requires specialized equipment and maintenance
    
• Vacuum Dehydration
  • Heating fluid under vacuum to evaporate water
    
  • Removes dissolved and emulsified water
    
  • Ideal for high-value systems and synthetic fluids
    
• Coalescing Filtration
  • Using filter media to merge water droplets for removal
    
  • Effective for free and emulsified water
    
  • Limited against dissolved moisture
    
• Absorptive Media
  

• Desiccant filters that trap water molecules
  
• Best for low-volume systems and mobile equipment
  
• Must be replaced regularly
  

A restorer in Ontario used a portable vacuum dehydrator to treat a contaminated hydraulic tank on a telehandler. After two cycles, water content dropped from 0.9% to 0.03%, and fluid clarity returned.
Preventive Measures and Fluid Management
To prevent water intrusion:

• Use sealed reservoirs with desiccant breathers
  
• Store fluid indoors in sealed containers
  
• Avoid pressure washing near hydraulic components
  
• Replace worn seals and inspect breather caps
  
• Sample fluid regularly and track water content trends
  

Recommended service intervals:

• Fluid sampling: every 500 hours or quarterly
  
• Filter replacement: every 250–500 hours
  
• Reservoir inspection: monthly
  
• Breather and seal check: every 100 hours
  

A technician in Florida added a fluid management protocol to his equipment checklist. By tracking fluid condition and replacing breather elements proactively, he extended hydraulic component life by 40%.
Conclusion and Recommendations
Water contamination in hydraulic fluid is a silent threat that erodes performance, damages components, and shortens equipment life. Whether caused by condensation, poor storage, or seal failure, it must be addressed quickly and thoroughly.
Recommendations include:

• Monitor fluid condition with regular sampling and moisture sensors
  
• Use vacuum dehydration or coalescing filters for effective water removal
  
• Implement sealed fluid storage and desiccant breathers
  
• Train operators and technicians in contamination prevention
  
• Document fluid history and service actions for long-term reliability
  

With disciplined fluid management and proactive dewatering strategies, hydraulic systems can operate cleanly, efficiently, and reliably—delivering the power and precision that modern equipment demands.