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Importance of fluid cleanliness in hydraulics

Looking to the modern machinery requirements hydraulics play a very active & crucial role in machine drives. As the high-precision machinery uses advanced hydraulic components like axial pumps & proportional valves maintenance of such elements is the most vital necessity. In hydraulics more than 80% of problems are due to contaminated fluid & so it is important to keep system fluid very clean & free of contaminants. Looking to these points latest concepts & methods of oil cleaning should be taken in prime consideration.

Tasks of a Hydraulic Filter

Bearinglubrication film

Fine/coarseparticle

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15

75D

iam

eter

in µ

m

Human hair

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Particle Proportions

4

Contamination Classes

NAS 12 ISO 21/18

Fresh oil,delivery in barrels

NAS 7 ISO 15/13

Fresh oil,delivery in mini containers

NAS 9 ISO 18/15

Fresh oil,delivery in tank trucks

NAS 5 ISO 14/11

Required for modernhydraulic systems

YearYear DevelopmentDevelopmentFiltration rateFiltration rate

19401940 First use of air and oil filters for First use of air and oil filters for 100 100 µmµm

engines; strainersengines; strainers

19501950 Big increase of hydraulicBig increase of hydraulicapplications and so filtrationapplications and so filtration

19601960 Use of star pleatedUse of star pleated 50 50 to 100 µmto 100 µm

mesh packs with inner coremesh packs with inner core

19701970 Development of paper andDevelopment of paper and up to 3 up to 3 µm µm

metall fleece elementsmetall fleece elements nominalnominal

19801980 Launch of the Multipass Test,Launch of the Multipass Test, up to 3 µm up to 3 µmstart of absolute filtrationstart of absolute filtration

absoluteabsolute

1990 1990 Absolute filtration in all applicationsAbsolute filtration in all applications 1 µm and 1 µm and 2µm2µm

absolute absolute

Filtration Technology Development

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Origins of Contamination

•External contamination•Internal contamination•Assembly•Initial contamination•Abrasion•New oil•Repairs

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Effects of contamination (Wear due to dirt particles)

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Clearances in various hydraulic components-01

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Surface & Depth filtration

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Filter arrangement in hydraulic system

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Suction line filter

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Pressure Line Filter

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Typical selection chart for pressure line filters

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Return Line Filter

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Typical selection chart for suction & return filters

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Filler & Breather with filling sieve

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Typical selection chart for filter in breather

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Cleanliness classes as per ISO 4406

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Cleanliness classes as per NAS-1638

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Comparison of Contamination Classifications

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Recommended filter pore sizes for Rexroth components

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Degree of separation Beta ratio

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Filter efficiency

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Some facts about contamination problem & filters

From time to time development has taken place for better method of oil cleaning. A continuous research & innovation is going on world-wide for Better & better filter technology.Contamination ingress in hydraulic system cannot be brought to zero.To clean the oil to a certain class is not difficult but what difficult is, to maintain that cleanliness level consistently during working cycles.As you go for fine filter you should be more careful & prompt to keep watch on filter clogging & replacement.We cannot keep hydraulic systems healthy without filters & protection to hydraulic system can be given by on-line filters only & not by other off-line cleaning methods.

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Electrostatic cleaning method

Electrostatic cleaning can be useful to control micro-level contaminants. Particularly if your main trouble is fine particles this can be very useful method for off-line cleaning.

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Working principle of ELC machine

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Cleaning range of ELC M/c. (General Idea)

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Filter is a must

• ELC is good technique for removal of micro-level contamination. ELC concept reduces the danger of hydraulic system malfunction where very small particles can affect severely. Moreover continuous running of ELC systems reduces load on working filters of the system.

• But a misconception that ELC can take place of filtration should be removed from one’s mind. On-line safety of hydraulic components can be achieved with protection filters only & not with ELC methods.

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The

Driv

e &

Con

trol

Com

pany

Thanks for your attention