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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

Chapter 12

Conditioning System Fluid

Filtration and Temperature Control

objectives
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.

objectives4
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.

objectives5
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.

need for fluid conditioning
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.

contaminants and their sources
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.

contaminants and their sources8
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.

contaminants and their sources9
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.

effects of contamination
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.

effects of contamination11
Effects of Contamination
  • Dirt leads to excessive wear

Schroeder Industries LLC

Permission granted to reproduce for educational use only.

system operating temperature
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.

system operating temperature13
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.

system operating temperature14
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.

system operating temperature15
System Operating Temperature
  • Low fluid temperature causes problems

Deere & Company

Permission granted to reproduce for educational use only.

system operating temperature16
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.

controlling and removing contaminants
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.

controlling and removing contaminants18
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.

controlling and removing contaminants19
Controlling and Removing Contaminants
  • The reservoir helps condition fluid

Permission granted to reproduce for educational use only.

controlling and removing contaminants20
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.

controlling and removing contaminants21
Controlling and Removing Contaminants
  • Filters and strainers clean fluid

Schroeder Industries LLC

Permission granted to reproduce for educational use only.

controlling and removing contaminants22
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.

controlling and removing contaminants23
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.

controlling and removing contaminants24
Controlling and Removing Contaminants
  • Surface-type filter

Eaton Fluid Power Training

Permission granted to reproduce for educational use only.

controlling and removing contaminants25
Microscopic view of numerous fluid flow routes in depth-type filter mediaControlling and Removing Contaminants

Donaldson Company, Inc.

Permission granted to reproduce for educational use only.

controlling and removing contaminants26
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.

controlling and removing contaminants27
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.

controlling and removing contaminants28
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.

controlling and removing contaminants29
Filters may have spin-on elementsControlling and Removing Contaminants

Permission granted to reproduce for educational use only.

controlling and removing contaminants30
Controlling and Removing Contaminants
  • Bypass valve for a filter

Zinga Industries, Inc.

Permission granted to reproduce for educational use only.

controlling and removing contaminants31
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.

controlling and removing contaminants32
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.

filtration ratings
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.

filtration ratings34
Filtration Ratings
  • Comparison of particle sizes

Schroeder Industries LLC

Permission granted to reproduce for educational use only.

filter ratings
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.

filter system locations
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.

filter system locations37
Filter System Locations
  • Pump inlet line is a basic filter location

Permission granted to reproduce for educational use only.

filter system locations38
Filter System Locations
  • System working line is a basic filter location

Permission granted to reproduce for educational use only.

filter system locations39
Filter System Locations
  • System return line is a basic filter location

Permission granted to reproduce for educational use only.

filter system locations40
Filter System Locations
  • Other filter locations: pump case drain

Permission granted to reproduce for educational use only.

filter system locations41
Filter System Locations
  • Other filter locations: in pressure-relief valve return line

Permission granted to reproduce for educational use only.

filter system locations42
Filter System Locations
  • Other filter locations: in bypass flow control line

Permission granted to reproduce for educational use only.

filter system fluid routing
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.

filter system fluid routing44
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.

filter system fluid routing45
Filter System Fluid Routing
  • Full flow filtration

Permission granted to reproduce for educational use only.

filter system fluid routing46
Filter System Fluid Routing
  • Proportional filtration

Permission granted to reproduce for educational use only.

filter system fluid routing47
Filter System Fluid Routing
  • Off-line filtration

Permission granted to reproduce for educational use only.

filter system fluid routing48
Filter System Fluid Routing
  • Portable off-line filtration

Donaldson Company, Inc.

Back

Front

Permission granted to reproduce for educational use only.

filter system maintenance
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.

controlling fluid temperature
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.

controlling fluid temperature51
Controlling Fluid Temperature
  • Special operating conditions may result in system operating temperatures outside of the desired range
    • Low or high ambient temperatures
    • Lengthy high-pressure holding periods in system operating cycles

Permission granted to reproduce for educational use only.

controlling fluid temperature52
Controlling Fluid Temperature
  • Extreme variations in fluid temperature can cause major problems
    • Decreased performance of the system
    • Reduced service life of component parts

Permission granted to reproduce for educational use only.

controlling fluid temperature53
Controlling Fluid Temperature
  • Heat exchangers can be used to keep the operating temperature within the desired range
  • This is accomplished by either adding heat to or subtracting heat from the system fluid

Permission granted to reproduce for educational use only.

heat exchanger design and operation
Heat Exchanger Designand Operation
  • Heat exchangers used in hydraulic systems include:
    • Air-cooled radiators and finned conductors
    • Shell-and-tube and brazed-plate heat exchangers
    • Immersion heat exchangers
  • Shell-and-tube, brazed-plate, and immersion heat exchangers can heat or cool system fluid

Permission granted to reproduce for educational use only.

heat exchanger design and operation55
Heat Exchanger Designand Operation
  • Radiators consist of a series of small lines passing through a series of metal fins
    • Fluid flows through the lines
    • Heat from the system fluid passes through the tube to the metal fins and on to the air passing over the fins
    • Construction and operation is like the radiator in a car

Permission granted to reproduce for educational use only.

heat exchanger design and operation56
This radiator has a fan to increase airflow over the linesHeat Exchanger Designand Operation

HYDAC Technology Corporation

Permission granted to reproduce for educational use only.

heat exchanger design and operation57
Heat Exchanger Designand Operation
  • Shell-and-tube heat exchangersconsist of a bundle of tubes enclosed in a metal shell
    • Tubes extend into common chambers in the bonnets
    • Cooling or heating water passes through the tubes
    • Hydraulic fluid passes through the space between the shell and the bundled tubes

Permission granted to reproduce for educational use only.

heat exchanger design and operation58
Heat Exchanger Designand Operation
  • Typical shell-and-tube heat exchanger

Permission granted to reproduce for educational use only.

heat exchanger design and operation59
Heat Exchanger Designand Operation
  • Hydraulic fluid passes through the space between the shell and the bundled tubes

Permission granted to reproduce for educational use only.

heat exchanger design and operation60
Heat Exchanger Designand Operation
  • Shell-and-tube heat exchangers are available in one-, two-, and four-pass designs
  • Pass refers to the number of times the cooling or heating fluid passes through the length of the shell

Permission granted to reproduce for educational use only.

heat exchanger design and operation61
Heat Exchanger Designand Operation
  • One-pass heat exchanger

Permission granted to reproduce for educational use only.

heat exchanger design and operation62
Heat Exchanger Designand Operation
  • Two-pass heat exchanger

Permission granted to reproduce for educational use only.

heat exchanger design and operation63
Heat Exchanger Designand Operation
  • Four-pass heat exchanger

Permission granted to reproduce for educational use only.

heat exchanger design and operation64
Heat Exchanger Designand Operation
  • Water may pass through a shell-and-tube heat exchanger multiple times

Provided by API Heat Transfer

Permission granted to reproduce for educational use only.

heat exchanger design and operation65
Brazed-plate heat exchangers operate much like a shell-and-tube exchangerHeat Exchanger Designand Operation

MTS Systems Corporation

Permission granted to reproduce for educational use only.

heat exchanger design and operation66
Immersion heat exchangersHeat Exchanger Designand Operation

Kim Hotstart Manufacturing Company

Permission granted to reproduce for educational use only.

determining need for heat exchanger
Determining Need forHeat Exchanger
  • In a continuously operating system, the recommended temperature range for reservoir oil is generally 110°F to 140°F
    • Below the range may cause sluggish system operation or component damage
    • Above the range can shorten fluid service life, shorten seal life, increase varnish formation, and increase bearing wear

Permission granted to reproduce for educational use only.

determining need for heat exchanger68
Determining Need forHeat Exchanger
  • Analysis of system cycle times and load conditions can be used to identify the source of excessive heat
  • This information may lead to modifications of the system and cycle times to eliminate the need for a heat exchanger

Permission granted to reproduce for educational use only.

determining need for heat exchanger69
Determining Need forHeat Exchanger
  • Well-kept maintenance records can be a valuable analysis tool in determining the need for a heat exchanger
  • Need for a heat exchanger may be indicated by:
    • Seal failures
    • System fluid oxidation
    • Rapid varnish buildup
    • Elevated fluid temperatures

Permission granted to reproduce for educational use only.

review question
Review Question

The fluid-conditioning system of hydraulic-powered equipment provides fluid that is clean and maintained at an acceptable operating _____.

temperature

Permission granted to reproduce for educational use only.

review question71
Review Question

_____ percent or more of the prime mover horsepower is converted into heat that raises the fluid temperature in a hydraulic system.

Twenty

Permission granted to reproduce for educational use only.

review question72
Review Question

A(n) _____ is often considered a course filter that removes only the largest of the contami-nants that have entered the hydraulic fluid.

strainer

Permission granted to reproduce for educational use only.

review question73
Review Question

To trap contaminants, _____-type filters use a mass of porous material that provides many different flow routes.

depth

Permission granted to reproduce for educational use only.

review question74
Review Question

For all hydraulic systems, the minimum filtration level recommended by the National Fluid Power Association is _____ microns.

25

Permission granted to reproduce for educational use only.

review question75
Review Question

List the three general locations for a filter in a hydraulic system.

A. Pump inlet line, B. system working lines between the pump and actuators, and C. return and drain lines between components and the reservoir.

Permission granted to reproduce for educational use only.

review question76
Review Question

During operation, _____ flows through the tubes of the shell-and-tube heat exchanger, while _____ flows around the tubes.

water; hydraulic fluid

Permission granted to reproduce for educational use only.

review question77
Review Question

Multiple-pass shell-and-tube heat exchangers are made possible by dividers located in the _____ of the shell.

bonnets

Permission granted to reproduce for educational use only.

review question78
Review Question

Name three problems that may result if a hydraulic system is consistently operated at lower-than-recommended temperatures.

A. Reducing ability of fluid to lubricate, B. sluggish system operation, and C. pump cavitation.

Permission granted to reproduce for educational use only.