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Design Closed Circuit

Design Closed Circuit

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Design Closed Circuit

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  1. Design Closed Circuit Introduction, May 2012

  2. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  3. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  4. 1. System OverviewHydrostatic Transmission ] N [ e c r o F e v Installed Engine Power i t c a r T Motor Ratio Pump Ratio A Speed [km/h] B • Continuously variable speed w/o loss of traction hydrostatic transmission - source 1 -

  5. 1. System OverviewHydrostatic Transmission • Motor output torque and speed depends on pump and motor displacement • Speed of hydrostatic transmission is reciprocal to displacements • Torque is proportional to displacements

  6. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  7. 2. Functionality of ComponentsIntegrated ChargePump

  8. 2. Functionality of Components Integrated Charge Pump • Charge pump is a fixed displacement pump (gerotor-type) which is directly connected to the pump input shaft • Charge pump displacement should be sized to approximately 10% of whole system displacement (pump and motor(s) displacements) in most applications

  9. 2. Functionality of Components Charge Pump - Functions Charge Pump flow rate functions: • Replenish leakage oil of pump and motor • Replenish loop flushing oil through the flushing valve • Provide flow for the servo control systems • Provide flow for auxiliary circuit functions e.g. parking brake release Charge Pump pressure functions: • Maintain low loop pressure • Provide sufficient pressure to activate the servo control systems

  10. 2. Functionality of ComponentsCharge Pressure Relief Valve

  11. 2. Functionality of Components Charge Pressure Relief Valve • Charge pressure relief valve is necessary to maintain low loop pressure • Protects the charge pump by limiting the charge pressure • Excess charge pump output flow is directed into the pump case

  12. 2. Functionality of ComponentsCharge Check Valve

  13. 2. Functionality of Components Charge Check Valve • It protects the charge pressure system (charge pump), otherwise a backflow from high pressure side will damaged the charge pump

  14. 2. Functionality of ComponentsLoop Flushing System

  15. 2. Functionality of ComponentsLoop Flushing System • Loop Flushing is necessary because of cooling requirements and contamination removal of system circuit • The LF-system removes fluid from the low pressure side of the closed circuit system • Loop Flushing valves are available with different flow rates to optimize flush flow requirements in all system operating conditions

  16. 2. Functionality of ComponentsHigh Pressure Relief Valve (HPRV)

  17. 2. Functionality of ComponentsHigh Pressure Relief Valve (HPRV) • High pressure relief valves are needed in hydrostatic transmission systems to limit maximum pressures • Pressures above the product ratings will damage the transmission • HPRV protect pumps, motors, hoses and other system components

  18. 2. Functionality of Components Pressure Limiter • Pressure Limiter is a non dissipative high pressure control • Limits the heat generated in the system when pressures are too high • PL changes the displacement of the pump in response to high system pressure

  19. 2. Functionality of Components Bypass • Bypass function allows an internal connection to be made between the two loops in the hydrostatic transmission • Function allows the vehicle to be moved without the engine running • Allows for disabled vehicles to be loaded onto a trailer or moved off the road • Intended to be for slow, short durations otherwise the hydrostatic transmission can be damaged

  20. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  21. 3. HydraulicFluidsWhat do you know about Hydraulic Fluids? Dirt Sun Water Air Blood Alcohol

  22. 3. HydraulicFluidsOverview Hydraulic Fluid Groups • Mineral oil based hydraulic fluids • Biogradeable hydraulic fluids • Syntetic ester (HEES) • Rape oil alkaline (HETG) • Fire resistance fluids • ATEX Regulation

  23. 3. HydraulicFluidsRecommended Hydraulic Fluids • Find recommended Hydraulic Fluids for Sauer-Danfoss hydrostatic components in Technical Literature* • Fluids meeting the technical literature requirements will very likely provide acceptable unit life • field testing is the only truly indication of fluid performance • Sauer-Danfosswarranty claim policies do not apply for fluid related damage *: “Hydraulic Fluids and Lubricants Technical Information”; page 20

  24. 3. HydraulicFluidsPhysical Behavior • Viscosity • Viscosity grade (VG) • Depends on temperature and pressure • Compromise between flow losses and leakage • Density • Depends on temperature and pressure

  25. 3. HydraulicFluidsPhysical Behavior Pressure-Behaviour Temperature-Behavior kinematic Viscosity kinematic Viscosity Temperature Temperature

  26. 3. HydraulicFluidsViskosity and Temerature Limits • Viscosity and temperature limits in the table “Viscosity and temperature limits” in technical information* are to be observed • Under normal operating condition it is recommended to keep the temperature in the range of 30 °C to 60 °C • Rule of thumb: fluid temperature increase from 80 °C [176 °F] to 90 °C [194 °F] may reduce fluid life by 50 % *: “Hydraulic Fluids and Lubricants Technical Information”; page 19

  27. 3. HydraulicFluidsAdditives Improvement of oil attributes • Viscosity-temperature behavior • Wear protection • Corrosion protection • Ageing resistance • Foam prevention • Bond to dirt particles

  28. 3. HydraulicFluidsSelection Criteria • Manufacturer‘s instructions • Release of diverse oils • Depends on system • Application (vehicle, temperature conditions) • Fill rate • Application environment • Climate • Area of application (i.e. environmental, flammability regulations, etc.)

  29. 3. HydraulicFluidsAdditional Information • Technical Information “Hydraulic Fluids and Lubricants” (520L0463) • Technical Information “Experience with Biodegradable Hydraulic Fluids” (520L0465)

  30. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  31. 4. FiltrationContamination Sources of contamination: • Installation • System components • Fill oil • Repair of a unit Types of contamination: • Metal • Synthetic materials • Organic materials • Plastic • Water • Etc. Scratches on Piston Shoe

  32. 4. FiltrationCleanliness Classes ISO 4406 1999: • Specification of three cleanliness classes correlated to particle size ≥4; ≥6; ≥14 [μm] • Example: ISO 18/16/13

  33. 4. FiltrationCleanliness Classes Sauer-Danfoss recommends the cleanliness classes below for different applications* Maximum class at machine start up 25/22/17 *: “Design Guideline for Hydraulic Fluid Cleanliness Technical Information” (520L0467), p. 13, Spreadsheet: “Fluid cleanliness requirements according to product“

  34. 4. Filtration Kind of Filtration Partial flow filtration + Small filter - Partial backflow of oil w/o filtration - Charge pump unprotected (pre-filtration necessary)

  35. 4. Filtration Kind of Filtration Full flow filtration + Complete oil filtration + Small filter - Charge pump unprotected ( pre-filtration necessary)

  36. 4. FiltrationKind of Filtration Suction filtration + Charge pump protected - Large filter surface necessary - Disadvantageous at low temperature

  37. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  38. 5. ReservoirOverviewArt der Filterung Tasks: • Fluid reservoir • Ensures there is enough oil for hydraulic system • Cooling • Separates dirt, water and air • Assures smooth fluid flow (laminar flow) at suction

  39. Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger Basic Hydrostatic (closed circuit)

  40. 6. Heat ExchangerFunctionand Type Removal of hydraulic-system heat • Prevents overheating of oil • Ideal oil-temperature should be 60 to 80°C Construction type in mobile hydraulic • Oil-air-heat exchanger Oil-airheatexchanger

  41. 6. Heat ExchangerDesign Criteria engine fan vehicle cooler SD FD system

  42. 6. Heat ExchangerSauer-Danfoss Fan Drive example: closed circuit

  43. The End MENU

  44. Many Thanks for YOUR Attention! When Chuck Norris says “420 bar" he is not quoting the pressure rating of the H1B motor, he is telling you how much pressure his foot will apply to your face. The three things that make hydraulics work: 1. Flow 2. Pressure 3. Chuck Norris

  45. Overview Literature Sources MENU - Source 1 - Ölhydraulik – Handbuchfür die hydrostatischLeistungsübertragungin der Fluidtechnik; Findeisen, D.; Springer