Fluids and Filtration Transmission Design Elements SauerDanfoss Hydraulic

Fluids and Filtration

Transmission Design Elements Sauer-Danfoss Hydraulic Unit Design Fluid Quality Pressure and Speed Ratings Transmission Design Component Sizing Circuit Design Customer Machine Design

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

Types of Contaminants • Water / other fluid • Air • Solid particles

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

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

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 ISO 4406 standard

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 4 mm – 18 is number of particles larger than 6 mm – 13 is number of particles larger than 14 mm

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

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

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

• Viscosity

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

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

Viscosity

EP Additives • When viscosity just isn’t enough – – Phospherous Zinc Phosphates (ZDDP) Molybdenum Polymers

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

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

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

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

Temperature Limits

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

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

Fluid Quality

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!

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

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!

Successful Experience • Premium grade antiwear mineral-based hydraulic fluids – – Premium turbine oils (except S 51) API CD engine oils - SAE J 183 Type F automatic transmission fluid -M 2 C 33 F Power shift fluids (Allison C-4, CAT TO-2)

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

Environmentally Friendly

Environmentally Friendly Fluids • When your customer wants: this instead of this

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

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

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

Fire Resistant

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

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)

Fire Resistant Fluids

Filtration

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

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

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

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

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’ don’t believe a word they say.

Literature 520 L 0463 520 L 0465

Literature 520 L 0466 520 L 0467

Cavitation