contamination and filters

Conditioning Conditioning System FluidSystem Fluid

Need for Fluid ConditioningNeed 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

Sources of ContaminantsSources of Contaminants

Contaminants in a hydraulic system include those: Built into the system during manufacture e.g. welding scales, lapping compounds, sands

from casting, debris during manufacturing System Generated: like wear products generated

inside the mating components Maintenance generated: contaminants generated by

opening or closing of system and exposed often to dirty maintenance environment

Sources of ContaminantsSources of Contaminants External conditions can

lead to contamination of system fluid

Routine refilling of the reservoir can contribute to fluid contamination– Use of dirty tools– Dirty replacement oil

Effects of ContaminationEffects 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

Effects of Effects of ContaminationContamination

Dirt leads to excessive wear

Controlling and Removing Controlling and Removing ContaminantsContaminants

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

Controlling and Controlling and Removing Removing

ContaminantsContaminants The reservoir must be considered:

– The basic unit for storage of system fluid– A primary contamination-control component– A primary heat-control component


The reservoir helps condition fluid


Strainers and filters trap insoluble material contained in hydraulic fluid

Strainers are generally considered coarse filters designed to remove only larger particles

Filters are generally considered fine filters that can remove small particles

Filters can be classified as Filters can be classified as surface type surface type or or depth type depth type filters.filters.

Surface-type filters provide a surface containing numerous holes to trap particles


ContaminantsContaminants Surface-type filters provide 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


ContaminantsContaminants Surface-type filter

Eaton Fluid Power Training

Microscopic view of numerous fluid flow routes in depth-type filter media

Depth-type filters use a mass of porous material to provide numerous flow routes that trap particles

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

StrainerStrainer A sump strainer has a basic housing Attached to the reservoir end of the pump inlet

line

Zinga Industries, Inc.

Filtration RatingsFiltration 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– No of dirt particles larger than a given particle size

counted upstream of the test filter divided by no of dirt particles counted downstream od the filter element under same pressure drop condition.

Filtration RatingsFiltration Ratings Comparison of particle sizes

Filter RatingsFilter 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

Filter System LocationsFilter 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


Pump inlet line is a basic filter location


System working line is a basic filter location


System return line is a basic filter location

Filter System LocationsFilter System Locations Other filter locations: pump case drain

Filter System LocationsFilter System Locations Other filter locations: in pressure-relief valve

return line

Filter System LocationsFilter System Locations Other filter locations: in bypass flow control

line

Filter System Fluid RoutingFilter 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

Filter System Fluid RoutingFilter 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

Filter System Fluid Filter System Fluid RoutingRouting

Full flow filtration


Proportional filtration


Off-line filtration


Portable off-line filtration

Front BackDonaldson Company, Inc.

Filter System Filter System MaintenanceMaintenance

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

contamination and filters

Documents

depth type filters

particlesdepthtype filters

surface type

adsorbentabsorbent filters

fine filters

coarse filters

manufacturing system

lost system