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Chapter 12

Chapter 12. Conditioning System Fluid. Filtration and Temperature Control. Objectives. Identify the typical contaminants found in hydraulic system fluid and describe the source of each.

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Chapter 12

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  1. Chapter 12 Conditioning System Fluid Filtration and Temperature Control

  2. Objectives • Identify the typical contaminants found in hydraulic system fluid and describe the source of each. • Explain the source of the energy responsible for increasing fluid temperature during hydraulic system operation. • Describe how reservoir design can be used to reduce fluid contamination. Permission granted to reproduce for educational use only.

  3. Objectives • List and compare the various filter media used for hydraulic fluid filtration. • Describe the filtration rating methods used with hydraulic filters and strainers. • Compare the characteristics of the various filter locations and circuits that may be used in hydraulic systems. Permission granted to reproduce for educational use only.

  4. Objectives • Explain the function of heat exchangers in a hydraulic system. • Describe the design and structure of heat exchangers commonly used in hydraulic systems. • Identify the factors that must be considered when determining the need for a heat exchanger in a hydraulic system. Permission granted to reproduce for educational use only.

  5. Need for Fluid Conditioning • Fluid-conditioning devices provide fluid that is clean and maintained at an acceptable operating temperature • As much as 75% of hydraulic system failures can be traced to system fluid contamination Permission granted to reproduce for educational use only.

  6. Contaminants andTheir Sources • Contaminants in a hydraulic system include those: • Built into the system during manufacture • Entering the system during operation • Resulting from component wear • Resulting from the breakdown of the hydraulic fluid Permission granted to reproduce for educational use only.

  7. Contaminants andTheir Sources • External conditions can lead to contamination of system fluid Reprinted courtesy of Caterpillar, Inc. Permission granted to reproduce for educational use only.

  8. Contaminants andTheir Sources • Routine refilling of the reservoir can contribute to fluid contamination • Use of dirty tools • Dirty replacement oil Permission granted to reproduce for educational use only.

  9. Effects of Contamination • Dirt in hydraulic fluid reduces the fluid’s ability to: • Provide lubrication • Seal clearances • Transfer heat • Transfer energy • This leads to increased wear, increased part clearances, and lost system operating efficiency Permission granted to reproduce for educational use only.

  10. Effects of Contamination • Dirt leads to excessive wear Schroeder Industries LLC Permission granted to reproduce for educational use only.

  11. System Operating Temperature • System operating temperature is a major concern when designing and operating hydraulic systems • Systems typically generate considerable heat during operation • Even well-designed systems convert 20% or more of the horsepower input into heat Permission granted to reproduce for educational use only.

  12. System Operating Temperature • System operating temperatures are usually monitored by measuring the temperature of the hydraulic fluid in the reservoir • In most systems, reservoir-oil temperature ranging from 110°F –140°F is considered desirable Permission granted to reproduce for educational use only.

  13. System Operating Temperature • Low fluid temperature can produce sluggish operation • This may result in: • Reduced operating efficiency • Pump damage caused by cavitation Permission granted to reproduce for educational use only.

  14. System Operating Temperature • Low fluid temperature causes problems Deere & Company Permission granted to reproduce for educational use only.

  15. System Operating Temperature • Hydraulic systems need to be designed to balance the rate of system heat input with the rate of heat removed by: • Conduction • Radiation • Convection Permission granted to reproduce for educational use only.

  16. Controlling and Removing Contaminants • The best route to follow to assure a clean operating system is preventing contaminants from entering the hydraulic system • This solution is not easily achieved • Designers, machine operators, and maintenance personnel must be aware of the sources of contaminants and how contaminants enter a system Permission granted to reproduce for educational use only.

  17. Controlling and Removing Contaminants • The reservoir must be considered: • The basic unit for storage of system fluid • A primary contamination-control component • A primary heat-control component Permission granted to reproduce for educational use only.

  18. Controlling and Removing Contaminants • The reservoir helps condition fluid Permission granted to reproduce for educational use only.

  19. Controlling and Removing Contaminants • Strainers and filters trap insoluble material contained in hydraulic fluid • Strainers are generally considered coarsefilters designed to remove only larger particles • Filters are generally considered finefilters that can remove small particles Permission granted to reproduce for educational use only.

  20. Controlling and Removing Contaminants • Filters and strainers clean fluid Schroeder Industries LLC Permission granted to reproduce for educational use only.

  21. Controlling and Removing Contaminants • Filters can be classified as surface type or depth type Zinga Industries, Inc. Permission granted to reproduce for educational use only.

  22. Controlling and Removing Contaminants • Surface-type filtersprovide a surface containing numerous holes to trap particles • Depth-type filters use a mass of porous material to provide numerous flow routes that trap particles Permission granted to reproduce for educational use only.

  23. Controlling and Removing Contaminants • Surface-type filter Eaton Fluid Power Training Permission granted to reproduce for educational use only.

  24. Microscopic view of numerous fluid flow routes in depth-type filter media Controlling and Removing Contaminants Donaldson Company, Inc. Permission granted to reproduce for educational use only.

  25. Controlling and Removing Contaminants • Depth-type filters are classified as either absorbent or adsorbent • Absorbent filters trap solid particles, water, and suspended soluble materials • Adsorbent filters also use chemical treatments such as activated charcoal to remove contaminants Permission granted to reproduce for educational use only.

  26. Controlling and Removing Contaminants • Filter housings range from simple threaded collars to castings with a metal bowl holding the element • Housings often include filter-element-condition indicators and bypass valves Permission granted to reproduce for educational use only.

  27. Controlling and Removing Contaminants • A sump strainer has a basic housing • Attached to the reservoir end of the pump inlet line Zinga Industries, Inc. Permission granted to reproduce for educational use only.

  28. Filters may have spin-on elements Controlling and Removing Contaminants Permission granted to reproduce for educational use only.

  29. Controlling and Removing Contaminants • Bypass valve for a filter Zinga Industries, Inc. Permission granted to reproduce for educational use only.

  30. Controlling and Removing Contaminants • Filter-element-condition indicators show when a filter needs to be changed Zinga Industries, Inc. Permission granted to reproduce for educational use only.

  31. Controlling and Removing Contaminants • Filter housing style and the ability of the unit to withstand system operating pressure depend on location • Sump strainers operate at slightly below atmospheric pressure • Filters in working lines must be able to withstand full system pressure Permission granted to reproduce for educational use only.

  32. Filtration Ratings • Level of filtration is commonly indicated by a micron rating • One micron is .000039 • Filtration level of 25 microns is commonly recommended as a minimum • Always follow the recommendation of the manufacturer Permission granted to reproduce for educational use only.

  33. Filtration Ratings • Comparison of particle sizes Schroeder Industries LLC Permission granted to reproduce for educational use only.

  34. Filter Ratings • Filters have absolute or nominal ratings • Absolute rating indicates all particles larger than the stated size will be removed • Nominal rating indicates the average pore size • Nominal rating does not guarantee removal of all particles larger than the stated size Permission granted to reproduce for educational use only.

  35. Filter System Locations • Filters may be located in: • Pump inlet lines • System working lines • Return and drain lines • Flow resistance through inlet line filters is a special concern as pump cavitation may develop if the filter element produces excessive pressure drop Permission granted to reproduce for educational use only.

  36. Filter System Locations • Pump inlet line is a basic filter location Permission granted to reproduce for educational use only.

  37. Filter System Locations • System working line is a basic filter location Permission granted to reproduce for educational use only.

  38. Filter System Locations • System return line is a basic filter location Permission granted to reproduce for educational use only.

  39. Filter System Locations • Other filter locations: pump case drain Permission granted to reproduce for educational use only.

  40. Filter System Locations • Other filter locations: in pressure-relief valve return line Permission granted to reproduce for educational use only.

  41. Filter System Locations • Other filter locations: in bypass flow control line Permission granted to reproduce for educational use only.

  42. Filter System Fluid Routing • One of three methods is used to route system fluid through a filter to assure filtration: • Full-flow filtration • Proportional filtration • Off-line filtration Permission granted to reproduce for educational use only.

  43. Filter System Fluid Routing • In full-flow filtration, all of the pump output is filtered • In proportional filtration, only part of the pump output is filtered during each system cycle • Off-line filtration uses a separate, small pump to continuously circulate system fluid from the reservoir through a filter Permission granted to reproduce for educational use only.

  44. Filter System Fluid Routing • Full flow filtration Permission granted to reproduce for educational use only.

  45. Filter System Fluid Routing • Proportional filtration Permission granted to reproduce for educational use only.

  46. Filter System Fluid Routing • Off-line filtration Permission granted to reproduce for educational use only.

  47. Filter System Fluid Routing • Portable off-line filtration Donaldson Company, Inc. Back Front Permission granted to reproduce for educational use only.

  48. Filter System Maintenance • A critical part of maintenance is a plan for the routine service of the filtration system • Schedule for filter and fluid replacement • Reservoir cleaning • Proper storage and handling of the hydraulic fluid used in the system Permission granted to reproduce for educational use only.

  49. Controlling Fluid Temperature • A well-designed hydraulic system operates within a desired system temperature range without special controls • 110°F to 140°F is considered ideal • As system operates, heat gain and loss factors balance to maintain temperature • Often, a heat exchanger is not needed to maintain the desired temperature range Permission granted to reproduce for educational use only.

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