Fluid Types

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Fluid Types

• Ch.3 Hydraulic Fluids
• Matthew Berning
• Derrick Shea

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Overview

• Several Fluid Types
• Characteristics of Fluid Types
• Comparisons of Fluid Types

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Fluid Applications

• Transmits power
• Absorbs temperature
• Lubricates fluid system
• Cools devices
• Carries away contaminants
• Creates internal seals

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Things to Consider in Choosing a Fluid

• Viscosity Index (VI) ability to maintain
  acceptable viscosity over a temperature
  variation.
• Flammability
• Specific Gravity
• Cost and Availability
• Environmental Concerns Biodegradable?
• Toxic or Pollutant?

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General Categories

• Petroleum Oils
• Fire Resistant Fluids
• Biodegradable Fluids

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Figure 3-14 Page 61
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Petroleum Oil (Hydrocarbon Based)

• Most common type used
• Specifically Blended
• All major oil suppliers produce at least one type
  of Petroleum Oil

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Advantages

• Low Cost
• Good Lubricity
• Ready Availability
• Relatively Low Toxicity

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Fire Resistant FluidsHigh-Water Based Fluids

• These Include
• Water-In-Oil Emulsions
• Oil-In-Water Emulsions
• Water-Glycols

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Fire Resistant Fluids (cont)

• High Specific Gravity
• Withstand Somewhat High Temperatures
• High Cost
• High Maintenance
• Require Flooded Conditions to Prevent
  Cavitations

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Phosphate Esters

• Attack
• Elastomers
• Paint
• Plastics
• Require rubber or fluorocarbon seals

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Synthetics

• Although dangerous to machine parts, have many
  advantages
• Oxidation resistance
• Reduced friction
• Long life and long drain intervals
• Operates at high and low temperatures

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Vegetable Oil Based Fluids

• Used in mobile equipment
• Include
• Soy
• Rapeseed
• Other vegetable oils

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Advantages

• Biodegradable
• No toxicity
• High VI
• Thermal stability
• Low volatility
• Additive compatible

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Disadvantages

• Expensive
• Water will degrade (poor Hydrolytic stability)
• Poor at low temperatures
• Oxidation stability

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Additives

• Used in stable fluids
• Creates
• Antiwear
• Antioxidation
• Antitrust

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Remember

• Temperature affects viscosity
• Additives are not always good
• Oxidation rates for petroleum-based oils double
  for each 18 Degree F rise in temperatures after
  140 degree F
• Petroleum oil at atmospheric pressure contains
  8-10 air, and cannot be observed

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References

• Eaton-Vickers Text, Industrial Hydraulics manual
  4th edition 2001
• http//www.mcmaster.com/
• UDRI Lab B Shoyrer Park Center