astm d341 viscosity chart

www.donaldson.com 153

Technical Reference Guide

Why Hydraulic Components Need Protection 154

How Contamination Damages Precision Parts 154

Types of Contaminant 154

Sources of Contamination 155

Fluid Conditioning 156

Proper Filter Application 157

Fluid Properties 157

Types of Hydraulic Fluid 158

Basic Hydraulic Filtration Principles 159

Hydraulic Filtration Pressure Drop ( P) 161

Fluid Viscosity Graph 162

Physical Characteristics of Filter Elements 163

Micron Size: Comparison of Familiar Particles 164

ISO Beta Rating System 165

Application Guide for Donaldson Media 166

Filter Efficiency Standards 167

Efficiency of Donaldson Filter Media(Re-rated per ISO 16889) 169

Cleanliness Level Correlation Table 170

Compatibility of Donaldson Filter Media with Various Hydraulic Fluids 171

Filter Positioning 172

Technical Reference Guide “The Blue Pages”

Donaldson provides this technical reference as a short course in “Hydraulic

Filtration 101”— for those who want to gain abetter understanding of fluid power filtration.

In industrial applications at factories all overthe world, we too often see hydraulic circuitsthat don’t include proper fluid filtration, orinclude it as an afterthought. Good filtrationneeds to be an integral part of the hydrauliccircuit to ensure the long life and proper operation of the pumps, valves and motors.A $100 filter protects your $100,000 equipment.

This guide is offered to aid in choosing the filter that will help you achieve the ideal cleanliness levels and longest life for your critical components.

Material in this section is in the public domain, not confidential, and may be copied for educational purposes at any time.Information was collected from many sources,both public and private, including DonaldsonCompany, Inc. Engineering Departments,Eaton Corporation, the Lightning® ReferenceHandbook from Berendsen Fluid Power,Hydraulics & Pneumatics Magazine, NationalFluid Power Association (NFPA), and variousindustry authorities.

Symbols Usedß Beta Ratio

cSt CentistokesP Pressure Drop or Differential Pressure

ISO International Standards Organizationμm Micron or micrometerppm Parts per millionSSUSUS

Saybolt Seconds Universal

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Studies show thatmost (typically 70%)of hydraulic compo-nent replacement isnecessary because ofsurface degradation,and most of that isdue to mechanicalwear. Proper filtration ofhydraulic fluids can lengthen component life.

Typical Factors in Component Life

This cutaway view of a simplehydraulic valveillustrates how particles damagecomponents. Innormal operation,

the spool slides back and forth in the valve body,diverting oil to one side of the valve or the other. If a particle lodges between the spool and valve body,it will erode small flakes from the metal surfaces. Asthese flakes are moved back and forth by the actionof the spool, they can roll into a burr that jams thespool and disables the valve.

Fluid power circuits are designed in all shapes andsizes, both simple and complex in design, and theyall need protection from damaging contamination.Abrasive particles enter the system and, if unfiltered,damage sensitive components like pumps, valvesand motors. It is the job of the hydraulic filter toremove these particles from the oil flow to help prevent premature component wear and system failure. As the sophistication of hydraulic systemsincreases, the need for reliable filtration protectionbecomes ever more critical.

Many different types of contamination may bepresent in hydraulic fluid, causing various problems.Some are:

Particulate (dust, dirt, sand, rust, fibers,elastomers, paint chips)

Wear metals, silicon, and excessive additives(aluminum, chromium copper, iron, lead, tin,silicon, sodium, zinc, barium, phosphorous)

Water

Sealant (Teflon tape, pastes)

Sludge, oxidation, and other corrosion products

Acids and other chemicals

Biological, microbes (in high water based fluids)

Hydraulic Components Need Protection

Types of Contaminant

How Contamination Damages Precision Parts

70% mechanical wear from:• abrasion• fatigue• adhesion

70% Surface Degradation

30% corrosion

15% Accidents

15% Obsolescence

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Component DamageLooking down the barrel of an hydraulic cylinder, we cansee the scratches along the inside surface. Don’t cut costsby eliminating hydraulic filters! It could cost you more inthe long run in major component repairs!



Load

Clearance Size Particlesinteract with surfaces to cause abrasive wear

DynamicClearance

(μm)

Rubber & ElastomersDue to temperature, time, and high-velocity fluid streams, rubber compounds and elastomersdegrade —thus releasing particulates into the fluid.This may be from hoses, accumulator bladders,seals, or other elastomer products.

High Water Based FluidsThe water in HWBF tends to support biologicalgrowth and generate organic contamination andmicrobes.

Replacement of Failed ComponentsFailure to thoroughly clean fluid conductor linesafter replacing a failed hydraulic pump will causepremature catastrophic failure.

Donaldson recommends frequent oil sampling toensure proper contamination control. Sample testpoints should be close to hydraulic pumps and atother key locations that provide safe, reliable accessto the fluid while under full system pressure.

Where Contamination Comes From

There are surprising number of different sources ofsystem contamination in hydraulic filtration.

New Hydraulic FluidAdding new fluid can be a source; even though it’sfresh from the drum, new hydraulic fluid isn’t clean.(It may look clean, but, remember, the human eyecan only see a particle the size of about 40μm.) Oilout of shipping containers is usually contaminated toa level above what is acceptable for most hydraulicsystems: typically, new fluid has a cleanliness levelabout the same as ISO Code 21/19, and water content is typically 200 to 300 ppm. Never assumeyour oil is clean until it has been filtered.

Built-in Built-in contamination, also called primary contamination, is caused during the manufacture,assembly and testing of hydraulic components.Metal filings, small burrs, pieces of teflon tape, sandand other contaminants are routinely found in initialclean up filtration of newly manufactured systems.

Ingressed Ingressed or external contamination comes fromthe environment surrounding the system. Dirt canenter the hydraulic fluid supply through leakingseals, reservoir breather caps, and worn cylinderrod seals. Ingressed moisture, particularly, cancause long-term problems. As a hot system cools at night, cool moisture-laden air can be drawn into the reservoir; as the air condenses, water isreleased into the reservoir. Water in excess of 0.5%by volume in a hydrocarbon-based fluid acceleratesthe formation of acids, sludge and oxidation thatcan attack internal components, cause rust, andadversely affect lubrication properties. The severityof ingression and type of contaminant are dictatedby the applications and environment.

InducedMaintenance procedures can introduce contaminationinto the system. Opening the system allows airborneparticles to enter. Leaving the system open duringoperation provides continuous ambient particleingression. Keep your system closed as much as possible.

In-OperationThe major source of contamination are the pump& actuators, the hydraulic cylinder, or thehydraulic motor. Wear-generated contaminants are a hazard during normal hydraulic system operation. The circuit actually generates additionalparticles as the fluid comes into contact with theprecision machined surfaces of valves, motors andpumps. Contaminant levels can keep doubling with every new particle generated. The result can be catastrophic if these contaminants are notproperly filtered out of the system.

Chip/Grittoo large to enter clearance

Flow

Motion

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Chemical RemovalRemoval of acids, sludge, gums, varnishes, soaps,oxidation products and other chemicals generallyrequires an adsorbent (active) filter with Fuller Earth,active type clays, charcoal, or activated alumina.

Heat Removal Removing heat is important to maintain viscosityand prevent fluid breakdown. Usually performedwith heat exchangers, including air-to-oil and water-to-oil types, finned coolers, or refrigerated units.

Heat Addition Added heat is used for cold temp start-up to getfluid viscosities within operational limits. Useheaters, immersion or in-line.

Kidney Loop FiltrationOne very effective way of ensuring thorough fluidconditioning is with a dedicated off-line circulationloop, or “kidney” loop, as illustrated below. Widelyused in industrial applications, this system uses aseparate circulation pump that runs continuously,circulating and conditioning the fluid. Multiplestages and types of filters can be included in thecircuit, as well as heat exchangers and in-lineimmersion heaters. For further information onfluid conditioning, consult your fluid power supplieror a reputable manual.

Fluid Conditioning is the term for the overall conditioning of the fluid in the hydraulic system,and encompasses particulate removal via filtersalong with other various methods for removingsilt, air, water, heat, acid, sludge or chemicals.

Particulate Removal is usually done with mechanical filters. A welldesigned reservoir that allows settling will alsohelp in keeping particulates out of the mainstreamfluid. For ferrous particulates and rust, reservoirmagnets or strainer band magnets can also beused. Other methods such as centrifuging or electrostatic filtration units can also be used,particularly in continuous batch processing andfluid reclamation.

Removal of Silt Silt, defined as very fine particulate under 5μm insize, requires very fine filtration or “oil polishing.”

Air Removal Getting air out of the system is best done byadding 100 mesh screen in the reservoir,approximately 30° from horizontal to coalesceentrained air and allow larger bubbles to rise tothe surface when reservoir velocities are low.

Water Removal This requires special water removal filters, referredto as absorbent or inactive. In systems with largequantities of water, a vacuum dehydration systemmay be necessary.

Fluid Conditioning

Pump

KidneyLoopFilter

PressureFilter

Breather

SuctionStrainer

PMSuctionFilter

ReliefValve

PM

Return-LineFilter



Lubricity The property of the fluid that keeps friction low andmaintains an adequate film between moving parts.

Viscosity The thickness of the fluid as measured by resistance toflow. The fluid must be thin enough to flow freely, heavy enough toprevent wear and leakage. Hydraulic fluids thicken when they cooland thin out as they heat up. Because some hydraulic systems workunder wide temperature extremes, viscosity can be an important factor.

Viscosity Index (VI) The rate of viscosity change with temperature:the higher the index, the more stable the viscosity as temperaturevaries. VI can sometimes be improved by additives, usually polymers.

Rust Resistance Rust inhibiting chemicals in hydraulic fluids helpovercome the effects of moisture from condensation.

Oxidation Resistance Oxidation inhibitors delay the sludgy/acidiceffects of air, heat, and contamination in the system.

Foaming Resistance Although control of foaming depends largelyon reservoir design, anti-foaming additives in the fluid also help.

Fluid Properties

When selecting a filter or replacement element,it’s important to first answer some basic questionsabout your application. Where will the filter beused? What is the required cleanliness level (ISOcode) of your system? What type of oil are you filtering? Are there specific problems that neededto be addressed?

It’s also important to think about the viscosityof the fluid in your system. In some machinerylubrication applications, for example, the oil isvery thick and has a tougher time passing throughthe layer of media fibers. Heating techniques andthe addition of polymers can make the liquid lessviscous and therefore easier to filter. Another optionis to install a filter with larger media surface area,such as the Donaldson HFK08 or HEK11 lowpressure filters, that can accommodate more viscous fluids.

Next, think about duty cycle and flow issues.Working components such as cylinders often create wide variations in flow—also called pulsating flow —that can be problematic for filters with higher efficiency ratings. On the otherhand, dedicated off-line filtration (also called “kidney loop”) produces a very consistent flow,so it makes sense to use a more efficient filter.

Filters used in applications with steady, continuousoperation at lower pressures will last longer thanfilters that must endure cycles of high pressure pulsating flow. Generally, the lower the micron rating of a filter, the more often it needs to bechanged since it is trapping more particles.

Finally, it’s wise to ask yourself, “How much is myequipment worth?” Calculate how much it wouldcost to replace the equipment in your system, incase of component failure, and make sure thoseareas are well protected with proper filtration.(For example, high performance servo valves arevery sensitive, costly components that need to beprotected with finer filtration media.)

Proper Filter Application Minimizing maintenance costs through goodcontamination control practices requires properfilter application based on the specific contami-nation problems. Good contamination controlmeans cost-effective filtration. When looking fora filter, first assess the needs of your system andany problem areas.

System Characteristics to ConsiderWhen Specifying Filtration1) Oil Viscosity

2) Flow

3) Pressure

4) What Components will be protected by the filter

5) Cleanliness level required (expressed in ISO code)

6) Type of oil/fluid

7) Environment (the system, the surrounding conditions, etc.)

8) Duty cycle

9) Operating Temperature

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Some types of HWBF:Oil-in-water emulsions: typically 95% water and5% oil, with the oil droplets dispersed through-out the water. Provide some fire resistance, butdue to oil content, other fluids are superior.

Water-in-oil emulsions (invert emulsion): typically40% water and 60% oil, with the water dispersedin the oil. Provide some fire resistance, but due tooil content, other fluids are superior.

Water-glycol: typically 40% water and 60% glycol. Excellent fire resistance. Since glycol is an antifreeze, water-glycol can be used atlower temps.

NOTE: HWBF may require reduced pressure rating of pumps and other components.

Phosphate Ester: Somewhat fire resistant andgood in higher temp operations. Aggressive fluids that attack elastomers, paints and plastics.Special seals required (EPR, Butyl rubber, orViton™). Note that synthetic fluids are typicallyphosphate esters, chlorinated hydrocarbons or a blend with good lubrication characteristics but usually with low viscosity index. As withstraight phosphate esters, use special seals, paintsand plastics.

BiodegradableWith increasing concern about the environmentalimpact of hydraulic system leaks and spills,biodegradable fluids are receiving expanded usage, particularly in Europe. There are two types of common biodegradable hydraulic fluids: (1) vegetable-based oils, such as sunflower or grapeseed oils, and (2) synthetic oils like diesters,etc. Generally, systems using biodegradable fluidsare derated for maximum and minimum tempera-tures. Users who replace standard hydraulic oilswith biodegradable oils must check with filtrationcomponent manufacturers to confirm that the fluidand components are compatible.

There are many kinds of fluids used for power,but they can basically be called petroleum-basedfluids, biodegradable fluids, and fire-resistantfluids. A brief description of some of the types ineach category are listed below; for details on theseor others, consult your fluid power supplier orrefer to a reputable manual on hydraulics, such asthe Lightning Reference Handbook, published byBerendsen Fluid Power, Whittier, CA 90601.

Petroleum Based (Hydrocarbon)These are the most commonly used fluids inhydraulic systems. Their major advantages are low cost, good lubricity, relatively low/non-toxicity,and common availability. This type of fluid is notjust plain oil; rather, it is a special formulationwith additives that make it suitable for hydraulicsystems. Mostly, the additives inhibit or preventrust, oxidation, foam and wear.

Variations:

Straight oils: same as petroleum-based oil but without the additives.

Automatic transmission fluids (ATF): excellentlow temp viscosity and very high VI.

Military hydraulic fluids (ie: MIL-H-5606 & MIL-H-83282): also called ‘red oil’ because of the color. Low viscosity, good for cold temp operations, but may have to be modified for pumps.

Fire Resistant FluidsThere are two types of fire-resistant fluids commonly used in hydraulic applications:Phosphate Esters and High Water Based Fluids(HWBF). Although generally not as viscous at cold temperatures as petroleum-based fluids,they are fire resistant due to their high content of noncombustible material. Very useful in over-coming the likelihood of fire caused by a brokenhydraulic line spraying petroleum fluid into a pit of molten metal, onto a hot manifold, into a heat-treating furnace, or other ignition source.

Types of Hydraulic Fluid��

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B. Cellulose Media

Cellulose fibers are actually wood chips, micro-scopic in size and held together by resin. As yousee in the photo below, the fibers are irregular inboth shape and size.

Celluose often has lower beta ratings, whichmeans there are smaller pores in the media.Smaller media pores cause more flow resistance,in turn causing higher pressure drop.

While cellulose provides effective filtration for awide variety of petroleum-base fluids, in certainapplications it results in poor filtration perform-ance as compared to synthetic media.

C. Water Removal Media

This is media formulated with dessicants andresins to remove moisture and condensation frompetroleum-based fluids. (For concentration ofwater greater than half of 1 percent (0.05%) in thehydraulic oil, we recommend you use a vacuumdehydrator unit.)

D. Wire-Mesh Media

Wire-mesh media consists of stainless steel, epoxy-coated wire mesh available in 3 mesh sizes:

• 100 mesh yields 150μm filtration • 200 mesh yields 74μm filtration • 325 mesh yields 44μm filtration

Typically wire-mesh filters will be applied to catchvery large, harsh particulate that would rip up anormal filter. You may also find this media usefulas a coarse filter in viscous fluid applications.

Filter MediaMedia is a term used to describe any material usedto filter particles out of a fluid flow stream. Thereare four basic types used to remove contaminationin hydraulic applications:

A. Synthetic Media

Synthetic fibers are man-made, smooth and roundedof provide the least resistance to flow. Their consis-tent shape allows us to control the fiber size anddistribution pattern throughout the media mat tocreate the smoothest, least inhibited fluid flow.

Consistency of fiber shape allows the maximumamount of contaminant-catching surface area and specific pore size control. The result is mediawith predictable filtration efficiencies at removingspecified contaminants (i.g., 4μm) and maximumdirt holding capacity.

The low resistance of synthetic media to fluid flow makes it ideal for synthetic fluids, waterglycols, water/oil emulsions, HWCF, and petroleum-based fluids.

Basic Hydraulic Filtration Principles

Donaldson’s SyntheticMedia: Synteq®

Photo of Donaldson Synteq®

synthetic filter media as seen magnified hundreds of times under the scanning electron microscope. The smooth rounded fibers provide low resistance to fluid flow.

Cellulose filter media —photo from scanning electron microscope —magnified hundreds of times.

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How Filter Media FunctionsIn a Filtration SystemThe job of the media is to capture particles andallow the fluid to flow through. For fluid to passthrough, the media must have holes or channels to direct the fluid flow and allow it to pass. That’swhy filter media is a porous mat of fibers thatalters the fluid flow stream by causing fluid totwist, turn and accelerate during passage

The fluid changes direction as it comes into contactwith the media fibers, as illustrated above. As thefluid flows through the media, it changes directioncontinuously as it works its way through the mazeof media fibers. As it works its way through thedepths of the layers of fibers, the fluid becomescleaner and cleaner. Generally, the thicker themedia, the greater the dirt-holding capacity it has.

Looking at a cross-section view of thefibers, we can see how the flowstream is accelerated as itflows into the spacesbetween the fibers.

How Filter Media Collects ParticlesThere are four basic ways media captures particles. The first, called inertia, works on large, heavy particles suspended in the flow stream. These particles are heavier than the fluid surroundingthem. As the fluid changes direction to enter thefiber space, the particle continues in a straight lineand collides with the media fibers where it istrapped and held.

The second way media can capture particles is by diffusion. Diffusion works on the smallest particles. Small particles are not held in place by the viscous fluid and diffuse within the flowstream. As the particles traverse the flow stream,they collide with the fiber and are collected.

The third method of particle entrapment is callinterception. Direct interception works on particlesin the mid-range size that are not quite largeenough to have inertia and not small enough todiffuse within the flow stream. These mid-sizedparticles follow the flow stream as it bendsthrough the fiber spaces. Particles are intercepted or captured when they touch a fiber.

The fourth method of capture is called sievingand is the most common mechanism in hydraulicfiltration. As shownat right, this is when the particle is too large to fit between the fiber spaces.



Synteq® fibers offer the least amount of resistanceto fluid passing through the media. Consistency of fiber shape allows the maximum amount ofcontaminant-catching surface area and specificpore size control. The result is media with predictable filtration efficiencies at removingspecified contaminants (i.g., 4μm) and maximumdirt holding capacity.

Natural cellulose fibers are larger than syntheticfibers and jagged in shape, so controlling size ofthe pores in the media mat is difficult and there is less open volume. In most applications thisresults in higher P as compared to synthetic filters. Higher beta ratings mean there are smallerpores in the media; smaller media pores causemore flow resistance, in turn causing higher pressure drop.

2. Dirt, ContaminantAs dirt gets caught in the media, it eventuallybegins to build up and fill the pore openings.As the poreopenings shrink,the differentialpressure (pres-sure drop)increases. This iscalled restriction.This photo fromour scanningelectron microscope shows actual dirt particlesbuilding up in the media pores.

Excessive dirt in the media can cause dirt migrationor even filter failure. Dirt migration occurs whenthe restriction is so great that the differential pressure pushes dirt deeper into the media and,eventually, through the media and back into thesystem. Filter failure occurs when the restrictionbecomes so high that the filter cartridge collapses(outside-in flow) or bursts (inside-out flow) torelieve the upstream pressure.

To avoid such catastrophe, use of a filter serviceindicator is recommended. It measures the pressuredrop across the filter, then signals when the filter is‘full’ and needs to be changed.

Hydraulic Filtration Pressure Drop

The difference between the inlet pressure and theoutlet pressure is called pressure drop or differentialpressure. It’s symbolized by P. P is an irrecover-able loss of total pressure caused by the filter, and ismostly due to frictional drag on the fibers in the media.

P may increase as the particulate rating or efficiencyof the filter (as expressed by its beta ratio) gets better.

P also increases as the filter is being loaded withcontaminant.

Four Major Factors Contribute to Pressure Drop

1. Filter MediaMedia is, of course, the main factor influencingpressure drop; indeed, it causes pressure drop.That’s why having a low-friction, high-flowing

media is soimportant. Thenatural celluloseor paper fibers(shown at left)typically used infiltration are large,rough, and asirregular as naturemade them.

Donaldson developed a synthetic media with smooth,rounded fibers, consistently shaped so that we cancontrol the fiber size and distribution patternthroughout the media mat, and still allow thesmoothest, least inhibited fluid flow. Our syntheticmedia is named Synteq®.

Natural Fiber Cellulose media, as seen under the scanning electron microscope.

Donaldson’s synthetic Synteq® filter media —photo from scanning electron microscope —magnified hundreds of times.

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Filter media, amount of contamination, the flowrate, and fluid viscosity are all factors in theimportance of sizing the filter for the systemrequirements. Filters that are too small won’t beable to handle the system flow rate and will createexcessive pressure drop from the start. The resultscould be filter operation in the bypass mode, filterfailure, component malfunction, or catastrophicsystem failures. Filters that are too large for thesystem can be too costly. Oversized filters requiremore system oil and higher cost replacement elements. Optimimal sizing is best.

3. FlowHigher flows create higher pressure drop. Withfast moving fluid, there will be more friction causing higher pressure drop across the media.

4. Fluid ViscosityMeasured in centistokes (cSt) or Saybolt SecondsUniversal (SSU or SUS), fluid viscosity is the resist-ance of a fluid to flow. As fluid viscosity increases,the cSt rating increases. Higher fluid viscosities alsomean higher pressure drop because the thicker oilhas a tougher time passing through the layer ofmedia fibers. Cold start fluid is a good example of highly viscous fluid. See chart below.

Viscosity/Temperature ChartA.S.T.M. Standard Viscosity-Temperature Chart for Liquid Petroleum Products (D 341-43) Saybolt Universal Viscosity

MIL-H-5606KEROSENE

DIESEL FUEL

JP4 AVERAGE

AUTOMATIC TRANSMISSION FLUID

TYPE A

SAE 30

SAE 20

SAE 140 GEAR OIL

SAE 40

SAE 5010W-30

SAE 10



Inside the element, the filter media can vary inthickness, pleat depth and pleat concentration.

For example, Donaldson hydraulic filters are generally equipped with either white (“Synteq”our synthetic material) or natural brown (paper or cellulose material) media. It is important tonote that media colors vary according to eachmanufacturer—it should not be assumed that anywhite-colored media is made of synthetic material.

Some of the most important characteristics of a filter element (structure, fiber diameter, volumesolidity, basis weight, thickness, layering) can onlybe detected under a microscope.

Physical Characteristics of Elements

There are two main differences in filter elements.The first is the design of the filter element itself,and the second is the type of media that is used in such elements.

Filter elements have some attributes that are immediately obvious to the casual observer, such as height, inside diameter, outside diameter, mediaconcentration, type of liner, seal design, and the waythe media and componets are glued or potted together.

� Liners must be structurally sturdy to withstandpressure variance, yet open enough to allowgood flow.

� Top seal design must be leak-free, with a gasketor sealing device that ensures a good sealthroughout the life of the filter. Standard sealsare made of BunaN material, which is fine formost applications. However, if the filtered fluidis diester or phosphate ester fluid, you’ll need aseal made of a fluoroelastomer such as Viton.

� Media potting is key since it holds the media inplace at each end. Not only should the pottingbe fully around the ends of the media to preventleaks, it should also be of a material that canwithstand the application. For instance, epoxypotting should be used in elements that mustperform in higher temperature environments,phosphate ester fluids and some high waterbased fluids.

Damaged EquipmentDamage happens when key filtration points are ignored! The pistons in this pump are severely damaged from contamination in the oil.

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Micron Sizes of Familiar Particles

Grain of table salt 100μm

Human hair 80μm

Lower limit of visibility 40μm

White blood cell 25μm

Talcum powder 10μm

Red blood cell 8μm

Bacteria 2μm

Silt <5μm

Typical ISO CleanlinessHere are some typical ISO cleanlinessrecommendations fromcomponent manufacturers.(These are guidelines;always check the ratingsspecified by themanufacturer of yourspecific components.)

*Requires precise sampling practices to verify cleaniness levels.Source: Vickers

Combining the ISO Rating andFilter Performance RatingsWhile filter manufacturers publish beta ratings for filter media to describe efficiency performancelevels, a direct connection between the beta ratingscale and the ISO rating scale cannot be made.

The solution is monitoring filter media performanceat removing particles in the 4μm, 6μm, and 14μmranges. Oil analysis and field monitoring are theonly ways to get these measurements. Combine datafrom several tests to form a range of performance.Remember, actual filter performance will varybetween applications.

Here’s how to determine which filter media willbest protect your hydraulic components: plot anymedia performance range on the ApplicationGuide to Donaldson Filter Media (page 166),then connect the dots to make a line. On the same graph, plot your component requirement.(Reference chart below for some popularcomponents, or ask your supplier for therecommended ISO rating.) If the line of the mediafalls below the ISO line, or if the bottom line ofthe filtration range does not intersect the ISO line,the component will be protected.

40μm

25μm

10μm2μm100μm

80μm

Disaster StrikesWhen filters are not a main componentof the hydraulic circuit, disasterawaits! Here, piston rings were eatenaway by contaminants.

Pressure <3000 PSI >3000 PSI210 Bar >210 Bar

PumpsFixed Gear Pump 19/17/15 18/16/13Fixed Vane Pump 19/17/14 18/16/13Fixed Piston Pump 18/16/14 17/15/13Variable Vane Pump 18/16/14 17/15/13Varibale Piston Pump 17/15/13 16/14/12

ValvesDirectional (solenoid) 20/18/15 19/17/14Pressure (modulating) 19/17/14 19/17/14Flow Controls (standard) 19/17/14 19/17/14Check Valves 20/18/15 20/18/15Cartridge Valves 20/18/15 19/17/14Load-sensing Directional Valves 18/16/14 17/15/13Proportional Pressure Controls 18/16/13 17/15/12*Proportional Cartridge Valves 18/16/13 17/15/12*Servo Valves 16/14/11* 15/13/10*

ActuatorsCylinders 20/18/15 20/18/15Vane Motors 19/17/14 18/16/13Axial Piston Motors 18/16/13 17/15/12Gear Motors 20/18/15 19/17/14Radial Piston Motors 19/17/15 18/16/13



Code More Than Up to & Including14 80 16013 40 8012 20 4011 10 2010 5 109 2.5 58 1.3 2.57 .64 1.36 .32 .64

Range of number of particles per milliliter:

Code More Than Up to & Including24 80,000 160,00023 40,000 80,00022 20,000 40,00021 10,000 20,00020 5,000 10,00019 2,500 5,00018 1,300 2,50017 640 1,30016 320 64015 160 320

ISO 4406 Contamination CodeThis correlates to the numbers in the boxes along the right side of the graph on the next page.

ISO 18/16/13

�μm

The Application Guide for Donaldson Filter Media on page 166 provides a data format forrating fluid contamination level and plotting filter media performance.

The vertical numbers on the left side of the chartrepresent particle counts in a logarithmic progressionof ten: .01, .1, 1,10, 102, 103, 104, 105 and 106. (Thisrepresents the number of particle in the oil sampleat the given size.) The numbers across the bottom of the chart represent particle size in microns.

Donaldson media efficiency performance levels arederived from the ISO 16889 test standard with NIST-certified on-line automatic particle countersand ISO medium test dust. The Donaldson mediaefficiency performance levels shown are based on test averages under steady flow conditions. Actualperformance levels may vary by application, viscosity,flow variance and contamination differences. ContactDonaldson or your Donaldson distributor for specificapplication calculations.

The international rating system for fluid contaminationlevels is called the ISO contamination code and it isdetailed in the ISO 4406 document. Most componentmanufacturers publish filtration level recommendationsusing the ISO code. The ISO code, located on the rightside of the media application guide on page 166, iseasy to use if you remember the 4μm, 6μm and 14μmnumbers along the bottom of the chart.

Manufacturer’s ISO contamination levels are basedon controlling the particle counts of 4μm, 6μm and14μm particles in hydraulic system oil. This level is

Media Application Guide and ISO Rating System

identified by measuring the number of particles 4μmand greater, 6μm and greater, and 14μm and greaterin one milliliter of the system hydraulic oil sample.

How to Use the ISO RatingExample: A cartridge valve manufacturer recommends an ISO cleanlinesslevel of 18/16/13.

1) On the Application Guide for Donaldson Filter Media on the next page, place a dot on the vertical 4µm line, horizontally even with the 18 box of the ISO code.

2) Place a dot on the vertical 6µm line horizontally even with the 16 box of the ISO code.

3) Place a dot on the vertical 14µm line horizontally even with the 13 box of the ISO code.

4) Connect the dots to get the ISO cleanliness level 18/16/13.

As illustrated below, particle counts falling on and above the 18/16/13 lineare damaging to the component and exceed the 18/16/13 specification setby the manufacturer.

Select a Donaldson media that falls below 18/16/13 to achieve cleanlinesslevel tolerable to the component.

4 6 14

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Application Guide for Donaldson Filter Media

μmμmμm�

Logarithmic Scale

This represents thenumber of particles

at a given size in the oil sample



Indicates that testing was done with

APC’s calibrated with NIST fluid

ß10(c) = 10001000 times more particles

upstream than downstream

that are 10 μm and larger

Why the Efficiency Rating TestStandard Was UpdatedThe International Industry Standard (ISO) formulti-pass testing provides a common testingformat for filter manufacturers to rate filterperformance. This standardization gives you theability to reliably compare published filter ratingsamong different brands of filters.

ISO test standards were updated in 1999 toreflect the improved technology available inparticle counters and other test equipment. Thenewer particle counters provide more precisecounting and greater detail —reflecting a truerindication of filter performance.

The National Fluid Power Association (NFPA),the National Institute of Standards & Technology(NIST), and industry volunteers, including severalengineers from Donaldson, helped revise the ISOstandard. ISO 16889 has been in force since late1999 and ISO 4572 is officially discontinued.

Better Test Dust

The old test dust (AC fine test dust or ACFTD)was “ball milled,” which produced dust particles of varying size and shape. Particle distributionwas often different from batch to batch. Theaccuracy of ACFTD distribution and previous APCcalibration procedure was questioned by industry,due to lack of traceability and certification.ACFTD hasn’t been produced since 1992.

Now, the new test dust (ISO medium test dust) is “jet milled” to produce consistent particle size,shape, and distribution from batch to batch. Seedust size comparison chart below.

Liquid Automatic Particle Counters (APC’s)

In the old test standard (ISO 4572), fluid samplesobtained in bottles and off-line particle countingwere allowed. Now, in the updated standard (ISO 16889), on-line, laser-based automaticparticle counters, especially made for measuringliquids, are required and bottle counting methodsare disallowed, as illustrated on next page.

Understanding the Beta Rating SystemThis information is provided as an aid tounderstanding fluid filter efficiency terminologybased on current ISO, ANSI and NFPA teststandards. It is not proprietary and may bereproduced or distributed in any manner foreducational purposes.

What Is Beta Ratio?

Beta ratio (symbolized by ß) is a formula used to calculate the filtration efficiency of a particularfluid filter using base data obtained from multi-pass testing.

In a multi-pass test, fluid is continuously injectedwith a uniform amount of contaminant (i.e., ISOmedium test dust), then pumped through the filterunit being tested. Filter efficiency is determined by monitoring oil contamination levels upstreamand downstream of the test filter at specific times.An automatic particle counter is used to determinethe contamination level. Through this process anupstream to downstream particle count ratio isdeveloped, known as the beta ratio.

The formula used to calculate the beta ratio is:

Beta ratio(x)= particle count in upstream oil___ particle count in downstream oil

where (x) is a given particle size

Filter Efficiency Standards

Find further information on ISO 16889at www.NFPA.com or your ISO document source.

Ask for ISO/TR16386: 1999 “The Impact of Changes in ISO Fluid Power Particle Counting—

Contamination Control and Filter Test Standards.”

Call 1-800-846-1846168


DownStream

Up Stream

pump

pump

InjectionReservoir

TestReservoir

TestFilter

* APC = Liquid AutomaticParticle Counter

� In-Line Liquid Automatic ParticleCounters (APC) are now required for proper testing.

� APC calibration follows ISO 11171procedures

� ISO 11171 uses NIST (NationalInstistute of Standards & Technology)certified calibration fluid

ISO 16889

Test Dust Size ComparisonsACFTD calibrated size (μm) per ISO 4402 corresponds to a NIST-calibrated size [μm(c)] per ISO 11171

ACFTD 0.8 1 2 2.7 3 4.3 5 7 10 12 15 15.5 20 25 30 40 50

NIST 4 4.2 4.6 5 5.1 6 6.4 7.7 9.8 11.3 13.6 14 17.5 21.2 24.9 31.7 38.2

Overall, you can have strong confidence in filterratings resulting from tests per ISO 16889, as theyare highly accurate. As always, keep in mind thatbeta ratings are laboratory measurements understeady flow conditions with artificial contaminants —the real proof of the performance is how clean thefilter keeps the fluids in the application. A good oilanalysis program that checks the cleanliness of theoil periodically will verify that the proper filters arebeing used.

BottleSample

BottleSample

pump

pump

InjectionReservoir

TestReservoir

TestFilter

DownStream

Up Stream

ISO 4572(Discontinued)

� Either bottle samples or APC’s were allowed.

� APC calibration followed ISO4402 ACFTD(Discontinued)

The old particle counter calibration was based on only 1 dimension of an irregularly-shapedparticle (the longest cord). Today, the particlecounter calibration is based on equivalentspherical area of an irregularly-shaped particle.

NIST provides calibration suspension, which iscertified with X number of particles at a certainsize. This is verified by NIST. The new way tolist beta ratios includes a subscript (c) to indicateNIST certified test suspension and assures you oftraceability and repeatability.

flow meter

flow meter

OnlineAPC*

OnlineAPC*



Donaldson hydraulic filter media beta ratings areaverage ratings obtained from multi-pass tests per-formed per the new ISO 16889 standard.

According to the ISO standard, each filter manu-facturer can test a given filter at a variety of flow rates and terminal pressure drop ratingsthat fit the application, system configuration and filter size. Your actual performance may vary depending on the configuration of the filter tested and test conditions.

Donaldson Hydraulic Filter Media Beta Ratings

Highlights of ISO 16889

ISO 4572 is now replaced by ISO 16889 as the international standard for Multi-PassTests to determine the efficiency (beta rating or beta ratio) and the dirt-holding capacity of the filter element.

The test bench for ISO 16889 must have On-Line Liquid Automatic Optical ParticleCounters (APC) calibrated using NIST (NationalInstitute of Standards & Technology)-certifiedcalibration fluid. This includes added enhacementsto APC’s, to allow for better resolution, accuracy,repeatability and reproducibility.

ISO 12103-1,A3 (ISO Medium, 5mm-80mm)Test Dust was selected as replacement dust forcalibration and testing procedures.

APC’s are calibrated by passing a sample of cal-ibration fluid with a known particle size distri-bution and producing a calibration curve tomatch the known count distribution.

NIST used the Scanning Electron Microscopeanalysis and statistical analysis techiques to cer-tify the particle size distribution.

Particle counts, upstream and downstream, aretaken every minute of the test.

Beta ratios are reported with (c) to designateNIST traceability.

ISO 16889 recommends reporting beta ratings at:Rating Efficiency2 ......................50%10 ....................90%75 ....................98.7%100 ..................99%200 ..................99.5%1000 ................99.9%

Example: ß4(c) =200 signifies that there are 200 timesas many particles that are 4μm and larger upstream asdownstream. This is 99.5% efficiency.

Example: ß5(c) =1000 indicates that there are 1000times as many particles that are 5μm and largerupstream as downstream. This is 99.9% efficiency.

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NEW Donaldson Filter MediaEfficiency Ratings

Per ISO 16889 Test Standards

FORMERMedia Rating NEW Rating NEW RatingNumber Beta

X=75 Beta

X(C)=200 Beta

X(C)=1000

per ISO 4572 per ISO 16889 per ISO 16889

Donaldson Synteq® Synthetic MediaNo. ½ 2μm <3μm(c) <3μm(c)

No. 1 3μm 4μm(c) 6μm(c)

No. 2 5μm 5μm(c) 9μm(c)

No. 2½ 10μm 8μm(c) 10μm(c)

No. 3 15μm 12μm(c) 14μm(c)

No. 4 16μm 15μm(c) 20μm(c)

No. 6 13μm 10μm(c) 13μm(c)

No. 9 22μm 18μm(c) 23μm(c)

No. 16 37μm 16μm(c) 22μm(c)

No. 20 40μm >50μm(c) >50μm(c)

Donaldson Cellulose MediaNo. 3 16μm 18μm(c) 24μm(c)

No. 10 25μm 19μm(c) 23μm(c)

No. 15 35μm 25μm(c) 29μm(c)

No. 25 na 32μm(c) >40μm(c)

Donaldson Wire Mesh MediaNo. 44 45μm nominalNo. 74 75μm nominalNo. 149 150μm nominal

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ISO Particles ISO FTD* Mil Std NASCode Per Milliliter Gravimetric 1236A 1638 SAE Level

>10 microns Level (mg/l) (1967) (1964) (1963)

26/23 140,000 100025/23 85,000 100025/20 14,000 100 70021/18 4,500 1220/18 2,400 50020/17 2,300 1120/17 1,400 1019/16 1,200 1018/15 580 9 617/14 280 300 8 516/13 140 1 7 415/12 70 6 314/12 40 20014/11 35 5 213/10 14 0.1 4 112/9 9 3 011/8 5 210/8 3 10010/7 2.3 110/6 1.4 0.019/6 1.2 08/5 0.6 07/5 0.3 506/3 0.14 0.0015/2 0.04 252/.8 0.01 10

* SAE Fine Test Dust --- ISO approved test and calibration contaminant.Source: Milwaukee School of Engineering Seminar, Contamination &Filtration of Hydraulic Systems

Cleanliness Level Correlation Table

Conversion of cleanliness specifications to filterperformance is not an exact science because thecontamination level in a hydraulic system is afunction of the ingression and generation rate aswell as the filter performance.

Factors That Affect CleanlinessLevels in a Hydraulic System

Abrasive wear in space between adjacent mov-ing surfaces of components.

Erosive wear at component edges or directionchanges where there is high fluid velocity.

Fatigue wear by particles trapped betweenmoving surfaces.

Identification of the Most SensitiveComponent

Required cleanliness level is dominated by thecomponent with smallest clearances and/orhighest loading on the lubricating film.

Best source for determining this level is thespecification published by the component man-ufacturer.

Higher pressures reduce component life, unlesscontamination level is decreased accordingly.

Operating at half the rated pressure of compo-nent will increase its life by more than fourtimes.

Percent of operating time at maximum pressure depends on individual machines and application.

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Filter Positioning Discussion

Fluid to be RecommendedFiltered MediaPetroleum-based Synteq

CellulosePhosphate Ester SynteqDiester SynteqWater Glycol SynteqWater-Oil Emulsion SynteqBiodegradable Fluid SynteqHWCF (high water

content fluids) SynteqCoarse Filtration Wire Mesh

Compatibility of Donaldson FilterMedia with Hydraulic Fluids

While Donaldson has developed many formula-tions of media, they can be divided into two broadcategories: natural fibers, usually cellulose, andsynthetic or man-made fibers.

A Note on SealsFilters with seals made of BunaN are appropri-ate for most applications involving petroleumoil and some high water content fluids. Filterswith seals made of Viton® or Fluorel® (both flu-oroelastomers) are required when using diesters,phosphate ester fluids. Donaldson offers bothtypes. (Viton® is a registered trademark ofDuPont Dow Elastomers, and Fluorel® is a reg-istered trademark of 3M Company.)

In Donaldson filters with flurorcarbon elas-tomer seals, epoxy potting is used to accommo-date higher temperature environments and forcompatibility with fluids such as phosphateester and high water based fluids. The plastisol(heat cured) and urethane (self curing) pottingmaterials used in other filters perform well withpetroleum-based fluids.

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Piston Pump DamageThe severe score marks on the piston slippers leave noquestion about why good hydraulic filtration is important.

Call 1-800-846-1846172


Pump

KidneyLoopFilter

PressureFilter

Breather

SuctionStrainer

PMSuctionFilter

ReliefValve

PM

Return-LineFilter

This portable kid-ney loop filter cart is manu-factured by DonaldsonFiltration AsiaPacific Pte Ltd in Singapore.

KIDNEY LOOP FILTERSBenefit: HighSometimes referred to as “off-line”filters, kidney loop filters achievevery fine filtration by maintainingsteady-state flow, independent ofthe hydraulic circuit.

With this type of filtration, theentire hydraulic system can keepoperating while the kidney loop fil-ter is being serviced.

A kidney loop filter utilizes low-pressure housings that are easilyaccessible and serviceable. These fil-ters can either be integrated intothe main hydraulic reservoir, orused in mobile filter carts like the

one shown at left to service manyhydraulic systems.

Note that kidney loop filters do not directly protect components—rather, their main function is to polish the oil to a very cleancondition. It’s also important to remember that an additional pump and motor will be required.

FILLER / BREATHER Benefit: HighTank breathers are placed onhydraulic reservoirs to preventatmospheric contamination fromentering and to allow for sufficient

air movementinside the reservoir.Breathers shouldprevent particleslarger than 3 microns from enter-ing the system. Thisis a sensible, afford-

able solution for any hydraulic sys-tem, but by all means cannot be theonly filter on a hydraulic system.

How to Best Position Filters in Your Hydraulic CircuitWithin every industrial hydrauliccircuit there are many possibleplaces for filters.

The best systems are strategicallyengineered to ensure that oil is fil-tered properly at each stage of itsjourney through the circuit.Ideally, filtration should occur inthe following places:

• In the Reservoir• Before/After the Pump• In the Return-line System• Off-line

In reality, many companies haveto make tough decisions aboutwhich filters they can afford andwhich ones they’ll have to livewithout.

Much depends on the cleanlinesslevel requirements of the compo-nents, environment, duty cycle ofthe equipment and other variablesthat can vary from application toapplication.

This diagram showshow various types offilters can be used inhydraulic circuits.

Filter Positioning Guide


Pressure Filters:

HFK08 (p.48)HEK11 (p.52)FIK (p.34)

HEK11 (p.52)

Suction Filtration:

HPK04 (p.88)HPK05 (p.92)

HDK06 (p.44)HFK08 (p.48)

FPK02 (p.80)HPK02 (p.76)HPK03 (p.84)

HMK24 (p.64)HMK05 (p.68)HMK25 (p.68)

Donaldson Models Designed for Return Line Filtration:

LPS04 (p.12)HBK05 (p.16)HMK04 (p.64)

Downsides are few, but worth noting…return-line filters can be subject to flow surges (whichcontribute to poor filterperformance) and they do not filter the drain lines.

NOTE regarding return-line andkidney-loop filtration: If you’relooking for a great value filterthat’s easy to maintain and withlots of media choices, this is a wise investment. Although thesefilters are very common, onedownside is that there are very few standards of consistency fromone manufacturer to thenext, soreplacement cartridges are not necessarily interchangeable.

PRESSURE FILTERBenefit: HighThis is also known as “last-chance”filtration. High pressure filters keepclean the oil that comes directly from the pumpso that themore expensivedownstreamcomponents(such as valvesand actuators)are protected.Pressure line filters offer protection fromcatastrophicpump failure.They are aworthwhileinvestment forhigh-value systems—as are found in theaircraft industry, paper and steelmills, plastic injection molding, andin die-casting machines.

One downside to high pressure filters is, ironically, the high pressure. The entire system must be stopped in order to service a high-pressure filter—unless a duplex configuration is used.When oil is shooting out of a pump at 6000+ psi, it will take out anything in its way! By nature,a high-pressure pump is a prime mover of fluids, so it will experiencesignificant wear over time. Servicecan also be more difficult because of its heavy-duty construction...asanyone who’s ever tried to change a slippery, 200-pound cast-iron filtercan attest.

RETURN-LINE FILTERBenefit: HighThe advantages of return-line filtersare many. They are usually low-pressure housings, which are lesstypically expensive. Their purpose is to collect the dirt from around the circuit as the oil returns to thereservoir. Much like the kidney loop,the return-line filter provides ultimateflexibility in positioning— it can perform almost anywhere within the return line circuit, either mountedinline or built into the reservoir.

SUCTION FILTERBenefit: MediumNormally placed between thereservoir and the pump, suctionfilters are designed to remove particles in the 5 to 150 micronrange. They are easier to service andless expensive than many other typesof filters—but because restriction inthe suction line must be kept verylow, filter housing size tends to belarger than similar flow return orpressure filter housings.

The most popular application forsuction filters is with variable-speed hydrostatic pumps commonlyfound in off-road mobile applicationsand industrial variable-speed drives.They are also often used in harshenvironments and charge pumpapplications.

SUCTION STRAINERBenefit: LowSuction strainers, or sump-type filters, are often used in hydraulicfluid reservoirs. Their only real use is to keep cigarette butts,moths, nuts & bolts and the like out of the pump. Instead,such contaminants can easily be eliminated by keeping the reservoir sealed and by using a Filler/Breather and Return-Line Filter.

astm d341 viscosity chart

Documents

lightning

technical

predictable

catching surface

berendsen

particle counter

kidney loop

phosphate