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Fluids and Filtration
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Transmission Design Elements
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Hydraulic Fluid Roles

• Remove/Deal With Contamination
• Lubricate (separate moving parts)
• Transfer Heat
• Prevent Corrosion

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Types of Contaminants

• Water / other fluid
• Air
• Solid particles

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Water/Fluid Contamination

• Water or other fluids in a system may result in
• corrosion
• cavitation
• altered fluid viscosity
• Water can react with some fluids
• create harmful chemical by-products
• destroy important additives
• Good hydrolytic stability
• Fluid compatability
• ASTM D-2619 and JDQ 84

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Air Contamination

• Air increases the compressibility of the fluid
• creates a spongy system that is less responsive
• Air creates a loss of efficiency
• Higher operating temperatures
• Increased noise levels
• Loss of lubricity
• Increases oxidation
• Good anti-foam and resist dissolved air

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Particle Contamination

• Solid Particles increase wear in your system
• Solid Particles can stick valves / plug orifices
• Size quantity of these particles
• Allowable contamination is determined by the
  ISO4406 standard

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ISO Solid Contaminant Code

• Each level describes the amount of particles for
  a given particle size
• Example 22/18/13
• 22 is number of particles larger than 4mm
• 18 is number of particles larger than 6mm
• 13 is number of particles larger than 14mm

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Cleanliness Levels

• Important notes
• Old standard only used two numbers
• Exmaple 18/13 was 18 for 5mm particles and 13 for
  15mm particles
• 22/18/14 fluid has TWICE as many particles of the
  14mm size as 22/18/13 fluid

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Hydraulic Fluid Roles

• Remove/Deal With Contamination
• Lubricate (separate moving parts)
• Transfer Heat
• Prevent Corrosion

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Lubricate

• Hydrodynamic Lubrication (Viscosity)
• EP (Extreme Pressure additives)

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• Viscosity

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Viscosity Requirements

• Fluid must have high enough viscosity to maintain
  oil film between sliding surfaces
• Fluid that is too thin will result in excessive
  leakage and adhesive wear
• Viscosity and temperature limits must be met
  simultaneously
• Viscosity depends on fluid selection
• Remember low temperature viscosity during
  selection

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Viscosity

• Viscosity Index (VI) improved fluids
• Higher VI, usually more susceptible to sheardown
• Sheardown may lower operating viscosity below the
  originally specified value

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Viscosity
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EP Additives

• When viscosity just isnt enough
• Phospherous
• Zinc Phosphates (ZDDP)
• Molybdenum
• Polymers

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Hydraulic Fluid Roles

• Remove/Deal With Contamination
• Lubricate (separate moving parts)
• Transfer Heat
• Prevent Corrosion

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Effects of High Temperature

• Affects viscosity (lubricity, film thickness)
• Limits life of rubber seals
• high temperatures cause rubber to harden, crack
• Fluid breaks down
• sheardown occurs easier at higher temperatures
• thermal stability is critical
• Could mean air in system
• cavitation possible

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Temperature Requirements

• Size heat exchangers to keep fluid within
  recommended temperature limits
• Select worst continuous operating conditions
• For most machines, this occurs at highest
  transmission output speed obtainable
• Should test to verify these temperature limits
  are maintained
• Excessive heat may be generated by other circuit
  components

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Temperature Requirements

• Circuit designs should avoid depending on high
  pressure relief valves as part of the control
  system
• Frequent operation of these relief valves will
  generate intolerable heat
• Circuit components with high internal leakage
  also contribute to heat problems
• Circuits containing flow control valves such as
  flow dividers are susceptible to heat generation
  since they function by restricting oil flow with
  a pressure drop

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Temperature Limits
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Sources of Heat

• Component malfunction or circuit design
• High psi relief operation
• Inherent internal leakage
• Flow dividers, throttling devices
• Long power loop lines
• Extended roading

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Hydraulic Fluid Roles

• Remove/Deal With Contamination
• Lubricate (separate moving parts)
• Transfer Heat
• Prevent Corrosion
• Fluid compatibility with metals

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Fluid Quality
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Fluid Quality

• System Life depends on Fluid Quality
• 85 to 90 of all service problems are fluid
  related!
• Poor Fluid affects Hydraulic Systems
• Does not necessarily break components
• Causes loss of Efficiency
• Reduced Speed
• Reduced Power
• Fluid selection can lessen the impact of unusual
  environmental factors
• If you are getting good results with your current
  fluid, change with CAUTION!

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Fluid Quality

• Loss of Efficiency is caused by
• Smearing Parts rubbing, material transfer
• Caused by low fluid viscosity, lack of lube film
• Cavitation Fluid implosion, material removal
• Caused by air in fluid
• Etching Chemical corrosion, material removal
• Fluid becomes acidic due to presence of water
  and/or excessive temperature
• Scoring Grooves in parts, material
  removal/transfer
• Caused by particles of abrasive material in fluid

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Fluid Recommendations

• No set rules for choosing fluid
• Is a fluid is acceptable? How to get it approved
• Fluid producer should provide primary data
  including proof the fluid does work on piston
  equipment
• Approvals not published by pump mfgs.
• pump mfgs do not produce fluids
• pump mfgs do not control changes in fluid
  chemistry
• If the current fluid is working, change with
  caution
• Talk to your fluid people!
• Talk to your filter people!

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Successful Experience

• Premium grade antiwear mineral-based hydraulic
  fluids
• Premium turbine oils (except S51)
• API CD engine oils - SAE J183
• Type F automatic transmission fluid -M2C33F
• Power shift fluids (Allison C-4, CAT TO-2)

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Successful Experience

• Tractor fluids (IH Hytran, etc) -- except some
  have shown etching of yellow metals
• ATF except some Dexron III -- has shown etching
  of yellow metals
• Fire resistant fluids (at modified conditions)
• Environmentally acceptable (biodegradable) fluids

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Environmentally Friendly
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Environmentally Friendly Fluids

• When your customer wants

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Some Key Terms

• Readily Biodegradable
• 60 breakdown within 28 days
• Inherently Biodegradable
• 60 breakdown within 90 days
• Ashless
• typically contains no zinc or other heavy metals

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Types

• Vegetable Based
• HETG Rape Seed, traditionally
• Mineral Oil Based
• no recognized ISO classification
• Synthetic
• HEPG Polyglycol
• HEES Synthetic Ester
• HEPR - Polyalphaolefins
• Many new proprietary types

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Considerations

• Temperature
• Pressure
• Speed
• Long term fluid quality
• Increased maintenance interval
• Special filtration

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Fire Resistant
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Fire Resistant Fluids

• Phosphate ester or ester with oil
• Polyolester
• Invert emulsion
• Water glycol
• HWCF (define)

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Fire Resistant Fluids

• Require special system considerations
• Seals (with Skydrol)
• Inlet plumbing
• Reservoir size
• Filter size
• Modified operating parameters
• Increase maintenance frequency
• Fluid monitoring (bacterial growth, breakdown,
  etc)

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Fire Resistant Fluids
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Filtration
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Filters

• Filters clean the oil at start-up maintain
  acceptable levels of contamination as particles
  are ingested during system operation
• Filtration -- controlling particle sizes and
  quantities to meet appropriate levels
• Fluid cleanliness can only be maintained by
  selecting a filter capable of removing
  contaminants from the system

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Filter Selection

• Dependent on circuit design
• Fluid cleanliness requirement
• Particle ingression rate
• Maintenance interval
• Dirt holding capacity
• Built-in dirt
• Clean-up rate

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Filter Selection

• Filters are selected to meet the previous
  requirements using rating parameters of filter
  efficiency and capacity
• Filter efficiency -- how well the filter removes
  contaminants from the fluid
• Filter capacity -- how much contaminant the
  filter is capable of removing before a filter
  replacement is needed

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Filter Selection
Filter Efficiency designated by Beta Ratio Beta
(b) Ratio Upstream particles
Downstream particles bx 10 10 or 90
efficient 1 x particle
size in microns b10 10, means that 90 of all
particles 10 microns and larger are filtered out.
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Filter Testing

• ISO 16889 Multi-Pass Test
• Pressure drop/flow,
• Variation in particle removal abilities (Beta
  ratio) with size,
• Variation in performance with time and
  differential pressure,
• Weight of test contaminant retained by the
  filter,
• Filtration ratings over a wide size range, and
• Filtration performance over a wide range of
  particle sizes.
• What does an Absolute rating on a filter mean?
• Absolutely dont believe a word they say.

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Literature
520L0463
520L0465
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Literature
520L0466
520L0467
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Cavitation