The Handbook of Hydraulic Filtration · and gas filtration and separation, fuel conditioning and filtration, hydraulic and lubrication filtration, fluid power products and fluid condition

The Handbook ofHydraulic Filtration

Brochure: FDHB289UKSeptember 2006

Parker HannifinHydraulic Filter Division EuropeFDHB289UK.

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The Handbook of Hydraulic Filtration

Contents

Introduction

1

Contamination Basics 2

Contamination Types & Sources 4

Fluid Cleanliness Standards 12

Filter Media Types & Ratings 16

Filter Media Selection 20

Filter Element Life 22

Filter Housing Selection 24

Types & Locations of Filters 28

Fluid Analysis 32

Appendix 34


Parker’s Handbook of Hydraulic Filtration is intendedto familiarise the user with all aspects of hydraulicand lubrication filtration from the basics to advancedtechnology.

It is dedicated as a reference source with the intentof clearly and completely presenting the subjectmatter to the user, regardless of the individual levelof expertise.

The selection and proper use of contaminationcontrol products is an important tool in the battle toincrease production while reducing manufacturingcosts. This handbook will help the user makeinformed decisions about hydraulic filtration.


Contamination Basics

Functions of Hydraulic Fluid

Contamination Causes Most Hydraulic Failures

The experience of designers and users of hydraulic and lube oil systems has verified the following fact:over 85% of all system failures are a direct result of contamination!

The cost due to contamination is staggering,resulting from:

• Loss of production (downtime)• Component replacement costs• Frequent fluid replacement• Costly disposal• Increased overall maintenance costs• Increased scrap rate

Filtration Fact

Properly sized, installed, andmaintained hydraulic filtration playsa key role in machine preventativemaintenance planning.


2

Contamination interferes with the four functions of hydraulic fluids:

1. To act as an energy transmission medium.2. To lubricate internal moving parts of

components.3. To act as a heat transfer medium.4. To seal clearances between moving parts.

If any one of these functions is impaired, thehydraulic system will not perform as designed. Theresulting downtime can easily cost a largemanufacturing plant thousands of Euro’s per hour.Hydraulic fluid maintenance helps prevent orreduce unplanned downtime. This is accomplishedthrough a continuous improvement programmethat minimises and removes contaminants.

Filtration Fact

The function of a filter is to cleanoil, but the purpose is to reduceoperating costs.

Actual photomicrograph of particulate contamination(Magnified 100x Scale: 1 division = 20 microns)

Handbook of Hydraulic Filtration

Micrometre Scale

Contaminant Damage

• Orifice blockage• Component wear• Formation of rust or other oxidation• Chemical compound formation• Depletion of additives and oil degredation

Hydraulic fluid is expected to create a lubricatingfilm to keep precision parts separated. Ideally, thefilm is thick enough to completely fill the clearancebetween moving parts. This condition results in lowwear rates. When the wear rate is kept lowenough, a component is likely to reach its intendedlife expectancy, which may be millions ofpressurisation cycles.

The actual thickness of a lubricating film dependson fluid viscosity, applied load, and the relativespeed of the two surfaces. In many components,mechanical loads are to such an extreme that theysqueeze the lubricant into a very thin film, less than1 micrometre thick. If loads become high enough,the film will be punctured by the surface roughnessof the two moving parts. The result contributes toharmful friction.

3

Particle sizes are generally measured on themicrometre scale. One micrometre (or “micron”) is one-millionth of one metre, or 39 millionths of aninch. The limit of human visibility is approximately32µm micrometres. Keep in mind that mostdamage-causing particles in hydraulic orlubrication systems are smaller than 14µmmicrometres. Therefore, they are microscopic andcannot be seen by the unaided eye.

Component Microns

Typical Hydraulic Component Clearances

Anti-friction bearings 0.5

Vane pump (vane tip to outer ring) 0.5-1

Gear pump (gear to side plate) 0.5-5

Servo valves (spool to sleeve) 1-4

Hydrostatic Bearings 1-25

Piston pump (piston to bore) 5-40

Servo valves flapper wall 18-63

Actuators 50-250

Servo valves orifice 130-450

Substance Microns

Relative Sizes of Particles

InchesGrain of table salt 100 .0039

Human hair 70 .0027

Lower limit of visibility 40 .0016

Milled flour 25 .0010

Red blood cells 8 .0003

Bacteria 2 .0001


Contamination Types & Sources

Particle Contamination

TypesParticulate contamination is generally classified as “silt” or “chip”. Silt can be defined as the accumulationof particles less than 5µm over time. This type of contamination also causes system component failure overtime. Chips on the other hand, are particles 5µm+ and can cause immediate catastrophic failure. Both siltand chips can be further classified as:

Hard Particles• Silica• Carbon• Metal

Soft Particles• Rubber• Fibres• Micro Organism


4

Filtration Fact

Additives in hydraulic fluid aregenerally less than 1 micron andare unaffected by standardfiltration methods.

Types of Contamination

Silt

Flow

1. ParticulateSilt (0-5µm(c))Chips (5µm(c)+)

2. Water (Free & Dissolved)

3. Air


Sources

Damage

If not properly flushed,contaminants frommanufacturing and assembly will be left in the system.

These contaminants includedust, welding slag, rubberparticles from hoses and seals,sand from castings, and metaldebris from machinedcomponents. Also, when fluid isinitially added to the system,contamination is introduced.

During system operation,contamination enters throughbreather caps, worn seals, andother system openings. Systemoperation also generates internalcontamination. This occurs ascomponent wear debris andchemical by-products react withcomponent surfaces togenerate more contamination.

5

Filtration Fact

New fluid is not necessarily cleanfluid. Typically, new fluid right out of the drum is not fit for use inhydraulic or lubrication systems.

Generated Contamination

Abrasive Wear - Hard particlesbridging two moving surfaces,scraping one or both.

Cavitation Wear - Restrictedinlet flow to pump causes fluidvoids that implode causingshocks that break away criticalsurface material.

Fatigue Wear - Particlesbridging a clearance cause asurface stress riser thatexpands into a spall due torepeated stressing of thedamaged area.

Erosive Wear - Fine particles ina high speed stream of fluid eataway a metering edge or criticalsurface.

Adhesive Wear - Loss of oilfilm allows metal to metalcontact between movingsurfaces.

Corrosive Wear - Water orchemical contamination in thefluid causes rust or a chemicalreaction that degrades asurface.

A. Three-bodymechanicalinteractions canresult in interference.

B. Two-body wear iscommon in hydrauliccomponents.

C. Hard particles cancreate three-bodywear to generatemore particles.

D. Particle effects canbegin surface wear.

A B

C D Stress raisers causedby particle collisions

Built-in Contamination

Natural Contamination

Ingressed Contamination

Generated Contamination

Catalytic Effect



Prevention

• Use replaceable element or desiccant style filters for reservoir air breathers.• Flush all systems before initial start-up.• Specify rod wipers and replace worn actuator seals.• Cap off hoses and manifolds during handling and maintenance.• Filter all new fluid before it enters the reservoir.

External Contamination Sources


6

Filtration Fact

Most system ingression enters a system through the old-stylereservoir breather caps and thecylinder rod glands.

System Ingression Rate

Ingression rates for Typical Systems

Mobile Equipment 108-1010 per minute*

Manufacturing Plants 106-108 per minute*

Assembly Facilities 105-106 per minute*

*Number of particles greater than 10 microns ingressed

into a system from all sources.


Water Contamination

TypesThere is more to proper fluid maintenance than just removing particulate matter. Water is virtually auniversal contaminant, and just like solid particle contaminants, must be removed from operating fluids.Water can be either in a dissolved state or in a “free” state. Free, or emulsified, water is defined as thewater above the saturation point of a specific fluid. At this point, the fluid cannot dissolve or hold any morewater. Free water is generally noticeable as a “milky” discoloration of the fluid.

7

Filtration Fact

System Contamination Warning Signals• Solenoid burn-out.• Valve spool decentering, leakage, “chattering”.• Pump failure, loss of flow, frequent replacement.• Cylinder leakage, scoring.• Increased servo hysteresis.

Visual Effects of Water in Oil

1000 ppm(.10%)

300 ppm(.03%)

Fluid Type PPM

Typical Saturation Points

%Hydraulic Fluid 300 .03%

Lubrication Fluid 400 .04%

Transformer Fluid 50 .005%



Damage

Anti-wear additives break down in the presence of water and form acids. The combination of water, heatand dissimilar metals encourages galvanic action. Pitted and corroded metal surfaces and finishes result.Further complications occur as temperature drops and the fluid has less ability to hold water. As thefreezing point is reached, ice crystals form, adversely affecting total system function. Operating functionsmay also become slowed or erratic.

Electrical conductivity becomes a problem when water contamination weakens the insulating properties ofa fluid, this decreases its dielectric kV strength.


8

• Corrosion of metal surfaces• Accelerated abrasive wear• Bearing fatigue• Fluid additive breakdown• Viscosity variance• Increase in electrical conductivity

Filtration Fact

A simple ‘crackle test’ will tell youif there is free water in your fluid.Apply a flame under the container.If bubbles rise and ‘crackle’ fromthe point of applied heat, freewater is present in the fluid.

Typical results of pump wear due to particulate and water contamination


Sources

9

Fluids are constantly exposed to water and water vapour while being handled and stored. For instance, outdoorstorage of tanks and drums is common. Water may settle on top of fluid containers and be drawn into thecontainer during temperature changes. Water may also be introduced when opening or filling these containers.

Water can enter a system through worn cylinder or actuator seals or through reservoir openings.Condensation is also a prime water source. As the fluids cool in a reservoir or tank, water vapour willcondense on the inside surfaces, causing rust or other corrosion problems.

• Worn actuator seals• Reservoir opening leakage• Condensation• Heat exchanger leakage

Filtration Fact

Hydraulic fluids have the ability to‘hold’ more water as temperatureincreases. A cloudy fluid maybecome clearer as a system heats up.

% Water In Oil

0

50

100

150

200

250

% B

eari

ng L

ife R

emai

ning



Absorption Centrifugation Vacuum Dehydration

This is accomplished by filterelements that are designedspecifically to take out freewater. They usually consist of alaminate-type material thattransforms free water into a gelthat is trapped within theelement. These elements fit intostandard filter housings and aregenerally used when smallvolumes of water are involved.

Separates water from oil by aspinning motion. This method isreally only effective with freewater, in larger volumes

Separates water from oil througha vacuum and drying process.This method generally associatedwith for larger volumes of water,but is effective with both the freeand dissolved states.

Prevention

Excessive water can usually be removed from a system. The samepreventative measures taken to minimise particulate contaminationingression in a system can be applied to water contamination.However, once excessive water is detected, it can usually beeliminated by one of the following methods:


10

Filtration Fact

Absorption filter elements haveoptimum performance in low flowand low viscosity applications.

Vacuum Dehydration System

Prevention


Sources

Air Contamination

TypesAir in a liquid system can exist in either a dissolved or entrained (undissolved, or free) state. Dissolved airmay not pose a problem, providing it stays in solution. When a liquid contains undissolved air, problemscan occur as it passes through system components. There can be pressure changes that compress the airand produce a large amount of heat in small air bubbles. This compressability of air means that control ofthe system is lost. The heat can destroy additives, and the base fluid itself.

11

If the amount of dissolved airbecomes high enough, it willhave a negative effect on theamount of work performed bythe system. The workperformed in a hydraulic systemrelies on the fluid being relativelyincompressible, but air reducesthe bulk modulus of the fluid.This is due to the fact that air isup to 20,000 times morecompressible than a liquid inwhich it is dissolved. When air ispresent, a pump ends up doingmore work to compress the air,and less useful work on thesystem. In this situation, thesystem is said to be ‘spongy’.

• Loss of transmitted power• Reduced pump output• Loss of lubrication• Increased operating

temperature• Reservoir fluid foaming• Chemical reactions

Air in any form is a potentialsource of oxidation in liquids.This accelerates corrosion ofmetal parts, particularly whenwater is also present. Oxidationof additives also may occur.Both processes produce oxideswhich promote the formation ofparticulates, or form a sludge inthe liquid. Wear and interferenceincreases if oxidation debris isnot prevented or removed.

Damage

Filtration Fact

Free water is heavier than oil, thusit will settle to the bottom of thereservoir where much of it can beeasily removed by opening thedrain valve.

• System Leaks• Pump aeration• Reservoir fluid turbulence

• System air bleeds• Flooded suction pump• Proper reservoir design• Return Line Diffusers


Fluid Cleanliness Standards

The new ISO 11171 (International StandardsOrganization) Cleanliness Level Standard replacedISO 4406 upon acceptance of ISO MTD (MediumTest Dust) as a replacement for ACFTD. The mostwidely-used version of this standard references thenumber of particles greater than 4, 6, and 14micrometres in 1 millilitre of fluid. The number of 4+and 6+ micrometre particles is used as a referencepoint for “silt” particles. The 14+ size rangeindicates the quantity of larger particles presentwhich contribute greatly to possible catastrophiccomponent failure.

In order to detect or correct problems, acontamination reference scale is used. Particlecounting is the most common method used toderive cleanliness level standards. Very sensitiveoptical instruments are used to count the numberof particles in various size ranges. These counts arereported as the number of particles greater than acertain size found in a specified volume of fluid.


12

Range number

Micron

ISO Classification & Definition

Actual Particle CountRange (per ml)

18 4+ 1,300 - 2,500

16 6+ 320 - 640

13 14+ 40 - 80

ISO CODE 18 / 16 / 13

Particles> 4 microns



The ISO codes 4, 6, 14 microns replace the 2 digit 5, 15 microns and3 digit 2, 5, 15 microns in use prior to the introduction of ISO MTD.Their use continues and the results remain comparable with the 4, 6,14 micron ISO codes.

123456789

10111213141516171819202122232425262728293031323334353637383940

4.24.65.15.86.47.17.78.49.19.8

10.611.312.112.913.614.415.215.916.717.518.219.019.720.521.222.022.723.524.224.925.726.427.127.928.529.229.930.531.131.7

ACFTD size (ISO 4402:1991) µm

NIST (ISO 11171) size µm[c]

Particle size obtained using;

Particle Counts Comparison TableTable G.2 – Correlation between particle sizesobtained using; ACFTD (ISO 4402:1991) & NIST (ISO 11171)calibration methods

Note; This table is only a guideline. The exact relationship betweenACFTD sizes and the NIST sizes may vary from instrument toinstrument, depending on the characteristics of the particle counterand the original ACFTD calibration.ISO 1999. All rights reserved.

Handbook of Hydraulic Filtration13

Filtration Fact

Knowing the cleanliness level of afluid is the basis for contaminationcontrol measures.

ISO 21 / 19 / 17 fluid (magnification 100x) ISO 16 / 14 / 11 fluid (magnification 100x)

Range number

Number of particles per ml

More than

ISO 4406:1999 Chart

Up to and including24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

80,000

40,000

20,000

10,000

5,000

2,500

1,300

640

320

160

80

40

20

10

5

2.5

1.3

.64

.32

160,000

80,000

40,000

20,000

10,000

5,000

2,500

1,300

640

320

160

80

40

20

10

5

2.5

1.3

.64


Fluid Cleanliness Standards

Component Cleanliness Level Requirements

Many manufacturers of hydraulic and load bearingequipment specify the optimum cleanliness levelrequired for their components. Subjectingcomponents to fluid with higher contaminationlevels may result in much shorter component life.

In the table opposite, a few components and theirrecommended cleanliness levels are shown. It isalways best to consult with componentmanufacturers and obtain their written fluidcleanliness level recommendations. Thisinformation is needed in order to select the correctlevel of filtration.

It may also prove useful for any subsequentwarranty claims, as it may draw the line betweennormal use and excessive or abusive operation.


14

Components ISO Code

Fluid Cleanliness Required for TypicalHydraulic Components

Servo control valves 16 / 14 / 11

Proportional valves 17 / 15 / 12

Valve & piston pumps / motors 18 / 16 / 13

Directional & pressure control valves 18 / 16 / 13

Gear pumps / motors 19 / 17 / 14

Flow control valves, cylinders 20 / 18 / 15

New unused fluid 20 / 18 / 15

Filtration Fact

Most machine and hydrauliccomponent manufacturers specifya target ISO cleanliness level toequipment in order to achieveoptimal performance standards.

Handbook of Hydraulic Filtration15

Size Range(Microns) 00

NAS 1638 CLEANLINESS CLASSIFICATION CODES (per ml.)

2 to 5

5 to 15

15 to 25

25 to 50

50 to 100

>100

7.75

1.25

0.22

0.04

0.01

0.00

0

15.50

2.50

0.44

0.08

0.02

0.00

1

31

5

0.89

0.16

0.03

0.01

2

62

10

1.78

0.32

0.06

0.01

3

124

20

3.56

0.63

0.11

0.02

4

248

40

7.12

1.26

0.22

0.04

5

496

80

14.25

2.53

0.45

0.08

6

992

160

28.50

5.06

0.90

0.16

7

1984

320

57

10.12

1.80

0.32

8

3968

640

114

20.25

3.60

0.64

9

7936

1280

228

40.50

7.20

1.28

10

15872

2560

456

81

14.40

2.56

11

32302

5120

912

162

28.80

5.12

12

63488

10240

1824

324

57.60

10.24

Code toISO4406: 1999 >4 Microns

Particles per Millilitre (ISO11171 um [c])

Cleanliness Level Correlation Table

>6 Microns >14 Microns

NAS 1638(1964)

Disavowed SAElevel (1963)

23/21/18

22/20/17

21/19/16

20/18/15

19/17/14

18/16/13

17/15/12

16/14/11

15/13/10

14/12/09

13/11/08

12/10/07

11/09/06

10/08/05

80,000

40,000

20,000

10,000

5,000

2,500

1,300

640

320

160

80

40

20

10

20,000

10,000

5,000

2,500

1,300

640

320

160

80

40

20

10

5

2.50

2,500

1,300

640

320

160

80

40

20

10

5

2.50

1.30

0.64

0.32

12

11

10

9

8

7

6

5

4

3

2

1

0

00

6

5

4

3

2

1

0

SAE AS 4059

–

A12 / B12 / C11

A11 / B11 / C10

A10 / B10 / C9

A9 / B9 / C8

A8 / B8 / C7

A7 / B7 / C6

A6 / B6 / C5

A5 / B5 / C4

A4 / B4 / C3

A3 / B3 / C2

A2 / B2 / C1

A1 / B1 / C0

A0 / B0 / C000

Filtration Fact

Colour is not a good indicator of afluid’s cleanliness level.

NoteDue to the differences in the way in which each of these methods are designed, it is not possible to offer a precise, direct comparison. The correlation table above offers comparisons that are accurate within accepted limits


Filter Media Types & Ratings

Surface Media

For surface type filter media, thefluid stream basically has astraight through flow path.Contaminant is captured on thesurface of the element whichfaces the fluid flow. Surface typeelements are generally madefrom woven wire.

Since the process used inmanufacturing the wire clothcan be very accuratelycontrolled, surface type mediahave a consistent pore size.This consistent pore size is thediameter of the largest hardspherical particle that will passthrough the media underspecified test conditions.However, the build-up ofcontaminant on the elementsurface will allow the media tocapture particles smaller thanthe pore size rating. Likewise,particles that have a smallerdiameter, but may be longer inlength (such as a fibre strand),may pass downstream of asurface media.

The filter media is that part of the element which removes the contaminant.Media usually starts out in sheet form, and is then pleated to expose more surface area to the fluid flow.This reduces pressure differential while increasing dirt holding capacity. In some cases, the filter media mayhave multiple layers and mesh backing to achieve certain performance criteria. After being pleated and cutto the proper length, the two ends are fastened together using a special clip, adhesive, or other seamingmechanism. The most common media include wire mesh, cellulose, fibreglass composites, or othersynthetic materials. Filter media is generally classified as either surface or depth.


16

Filtration Fact

Surface media can be cleaned and re-used. An ultrasonic cleaner is usually the bestmethod. Depth media typically cannot becleaned and it is not re-usable.

Surface Media

25 µm


Depth Media

For depth type filter media, fluidmust take indirect paths throughthe material which makes up thefilter media. Particles aretrapped in the maze of openingsthroughout the media. Becauseof its construction, a depth typefilter media has many pores ofvarious sizes. Depending on thedistribution of pore sizes, thismedia can have a very highcaptive rate at very smallparticle sizes.

The nature of filtration mediaand the contaminant loadingprocess in a filter elementexplains why some elementslast much longer than others. Ingeneral, filter media containmillions of tiny pores formed bythe media fibres. The poreshave a range of different sizesand are interconnected

throughout the layer of themedia to form a tortuous pathfor fluid flow.

The two basic depth media typeswhich are used for filter elementsare cellulose and fibreglass.

The pores in cellulose mediatend to have a broad range ofsizes due to the irregular sizeand shape of the fibres. Thisresults in variable particleremoval. Due to this unreliableperformance cellulose is nolonger popular with companiesrequiring reliable, predictableperformance. In contrast,fibreglass media consist offibres which are very uniform insize and shape. The fibres aregenerally thinner than cellulosefibres, and have a uniformcircular cross section. These

17

Typical course fibreglass construction (100x) Typical fine fibreglass construction (100x)

typical fibre differences accountfor the performance advantageof fibreglass media. Thinnerfibres mean more actual poresin a given space. Furthermore,thinner fibres can be arrangedcloser together to producesmaller pores for finer filtration.Dirt holding capacity, as well asfiltration efficiency, are improvedas a result.

Flow Direction

Depth Media

MediaMaterial

CaptureEfficiency

Dirt HoldingCapacity

DifferentialPressure

Life in aSystem

Overall ThroughLife Cost

General Comparison of Filter Media

Wire Mesh Low Low Low Moderate

Cellulose Moderate Moderate High Moderate

Fibreglass High High High Moderate

High Very High Very High

Moderateto HighModerateto High

Graded LayerFibreglass

Moderateto High

Moderateto High

Moderateto Low


Filter Media Types & Ratings

The Multipass Test

The filtration industry uses the ISO 16889“Multipass Test Procedure” to evaluate filterelement performance. During the Multipass Test,fluid is circulated through the circuit under preciselycontrolled and monitored conditions. Thedifferential pressure across the test element iscontinuously recorded, as a constant amount ofcontaminant is injected upstream of the element.

Online laser particle sensors determine thecontaminant levels upstream and downstream ofthe test element. This performance attribute (TheBeta Ratio) is determined for several particle sizes.

Three important element performancecharacteristics are a result of the Multipass Test:

1. Dirt holding capacity.2. Pressure differential of the test filter element.3. Separation or filtration efficiency, expressed as

a “Beta Ratio”


18

Flow Meter

DownstreamSample

UpstreamSample

TestFilterP Gauge

Reservoir

Contaminant

Variable Speed Pump

Multipass Test

∆

Beta Ratio

The Beta Ratio (also known asthe filtration ratio) is a measureof the particle capture efficiencyof a filter element. It is thereforea performance rating.

As an example of how a Beta Ratio is derived from aMultipass Test. Assume that50,000 particles, 10micrometres and larger, werecounted upstream (before) ofthe test filter and 25 particles atthat same size range werecounted downstream (after) ofthe test filter. The correspondingBeta Ratio would equal 200, asseen in example 1.

Filtration Fact

Filter media ratingsexpressed as a BetaRatio indicate amedia’s particleremoval efficiency.

The example would read “Betaten equal to 200.” Now, a BetaRatio number alone means verylittle. It is a preliminary step tofind a filter’s particle captureefficiency. This efficiency,expressed as a percent, can befound by a simple equation.(Example 2)

“X” is at a specific particle size

β

β x =# of particles upstream# of particles downstream

10 (c) = =50,000

25200

Efficiencyx = ( )1-β

1001

Efficiency10 = ( )1-200

1001

= 99.5%

N particles upstream > x µm N particles downstream > x µm

ßx(c) = N particles upstream > x µm / N particles downstream > x µm

Example 1

Example 2


So, in the example, the particular filter tested was99.5% efficient at removing 10 micrometre andlarger particles. The Beta Ratio/ Efficiencies tableshows the general range Beta Ratio numbers andtheir corresponding efficiencies.

19

Filtration Fact

Multipass test results are verydependent on the followingvariables:• Flow rate• Terminal differential pressure

Beta Ratio(at a given particle size)

Capture Efficiency(at same particle size)

Beta Ratios / Efficiencies

1.01 1.0%

1.1 9.0%

1.5 33.3%

2.0 50.0%

5.0 80.0%

10.0 90.0%

20.0 95.0%

75.0 98.7%

100 99.0%

200 99.5%

1000 99.9%

Beta Ratio

DownstreamParticles Beta Ratio (x) Efficiency (x)

UpstreamParticles

50,000 = 2 50.0%

5’000 = 20 95.0%

1,333 = 75 98.7%

1,000 = 100 99.0%

500 = 200 99.5%

100 = 1000 99.9%

100,00050,000

100,0005,000

100,0001,333

100,0001,000

100,000500

100,000100

100,000 > (x) microns


Filter Media Selection

Instructions

From the following seven (7) system parameter tables, select the weighting factor which applies to your application. Add theseweighting factors together and consult the ‘Total Weighting Graph’ (Figure 1). The total weighting factor is found on the verticalaxis. Draw a straight line from left to right, starting at the total weighting factor number. This line is parallel to the horizontal axis.The total weighting line will intersect the media rating range band (found in the graph) at two points.

Next, draw a line from the two intersection points down to the horizontal axis. This axis shows the particle sizes where the mediashould have a Beta rating of at least 200 (99.5% separation efficiency). This indicates the most suitable range of media ratings foryour application. Consult the individual product catalogue(s) to match this result to a specific media.


20

Table APressure & Duty Cycles(To take account of the Normal operating pressure & it’sseverity of change, both in magnitude & frequency)

Pressure; Select operating pressureDuty;LIGHT Continuous operation at rated pressure or lowerMEDIUM Medium pressure changes up to rated pressureHEAVY Zero to full pressureSEVERE Zero to full pressure - with transients at high

frequency (0.6Hz) (e.g. power unit supplying a punching machine)

Select weighting from table below;

Pressure Duty

PSI Bar Lt Med Hvy Sev0-1015 0-70 1 2 3 4

1015-2175 70-150 1 3 4 52175-3625 150-250 2 3 4 63625-5075 250-350 3 5 6 7

5075+ 350+ 4 6 7 8

Weighting No.

Table BEnvironment

Examples WeightingGood Clean area’s, Lab’s 0Average General machine shops

assembly plants 1Poor Mobile mills (metal & paper) 2Hostile Foundries, also where

ingression of contaminant isexpected to be very high 3

Weighting No.

Table CComponent Sensitivity

Examples WeightingVery High High performance servo valves 8High Industrial servo valves 6Above average Piston pumps, proportional valves,

compensated flow controls 4Average Vane pumps, spool valves 3Below average Gear pumps, manual & poppet valves 2Minimal Ram pumps & cylinders 1

Weighting No.

Table DLife Expectancy

Hours Weighting0-1,000 0

1,000-5,000 15,000-10,000 210,000-20,000 3

20,000+ 5

Weighting No.

Table EComponent Economic LiabilityTo account for the cost of component replacement

Examples WeightingVery High Large piston pumps, large high

torque low speed motors 4High Cylinders, servo valves, piston motors 3Average Line mounted valves 2Low Subplate mounted valves, inexpensive

gear pumps 1

Weighting No.

Table FOperational Economic LiabilityTo account for the cost of downtime

Examples WeightingVery High Very expensive downtime of certain

paper, steel mill equipment &automotive equipment 5

High High volume production equipment 3Average Critical, but non-production equipment 2Low Equipment not critical to production 1

Weighting No..

Table GOperation Economic LiabilityTo account for the cost of downtime

Examples WeightingHigh Mine winding gear breaking systems 3Average Where failure is likely to cause a hazard 1Low Some hydraulic component test stands;

negligible hazard 0

Weighting No.

Total Weightingof all Tables


Selecting the Correct Media

A number of interrelated system factors determines the most suitable filter media for a particular application. The following mediaselection method was developed by the British Fluid Power Association (B.F.P.A.) and is used with permission. This media selectionprocess uses a ‘weighting’ system based upon the relative importance of major systems factors. Simply add the individual‘weighting’ factors from the seven (7) system parameter tables on the previous page. Then, consult the ‘Total Weighting Graph’(Figure 1) to find the appropriate rating range of suitable media. This rating range is based upon ‘absolute’ media ratings, wherethe Beta rating is equal to or greater than 200 (99.5% separation efficiency).

It must be emphasized that the rating range obtained can only be considered as an approximation. Precise operating parametersare often difficult to quantify by both users and makers of filtration equipment. Once the approximate rating range has beenestablished, the final media selection should be based on the specific characteristics of a given medium. For more informationabout specific media performance, the appropriate product catalogue’s should be consulted.

21

Example

Consider a large hydraulic excavator operating in a quarry. The hydraulic includesspare pressure compensated piston pumps and very large lift cylinders.

Operating Pressure & Duty Cycle (Table A)The system operates at 245 bar with extremes ofboth flow and pressure fluctuations in a cycle that isrepeated approximately four times every minute. Forthis reason it is considered to be Heavy Weighting = 4

Environment (Table B)The environment in which this machine is workingcan, in dry weather, be very dirty. As a result,ingression is likely to be high.Poor Weighting = 2

Component Sensitivity (Table C)Although the majority of the components areconsidered to be of average sensitivity, the pumps are;Above Average Weighting = 4

Life Expectancy (Table D)The annual usage is about 2000 hours & componentlife is expected to be about 4 years hence 8000hours and a weighting of;5,000-10,000 Hours Weighting = 2

Economic Liabilities (Components) (Table E)Components such as lift cylinders & variable pistonpumps are quite expensive for the end user topurchase.Component costs are high, hence;High Weighting = 3

Economic liabilities (Operational) (Table F)Economic liabilities caused by downtime varydepending upon the specific quarry situation, but thehigh capital cost of the system puts it in HIGH category.High Weighting = 3

Safety Liabilities (Table G)No additional weighting to take account of safety isrequiredLow Weighting = 0

Total Weighting(Sum of individual Weightings) = 18The weighting selected is in the range of 4 to 13microns. The media selected should have aminimum Beta Ratio Beta13 = 200 (99.5% efficient)

Filtration FactThere is no direct correlationbetween using a specificmedia and attaining a specificISO cleanliness classification.Numerous other variablesshould be considered, suchas particulate ingression,actual flow through filters,and filter locations.

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

94 6 10 14 17 21 25 32 38

Tota

l Wei

ght

ing

Fac

tors

Microns; Beta200 (99.5% Efficient at the Rated Size and Greater)

Rating Range

Figure 1


Filter Element Life

Contaminant Loading

Contaminant loading in a filter element is simplythe process of blocking the pores throughout theelement. As the filter element becomes blockedwith contaminant particles, there are fewer poresfor fluid flow, and the pressure required to maintainflow through the media increases. Initially, thedifferential pressure across the element increasesvery slowly because there is an abundance ofmedia pores for the fluid to pass through, and thepore blocking process has little effect on theoverall pressure loss. However, a point is reachedat which successive blocking of media poressignificantly reduces the number of available poresfor flow through the element.

At this point the differential pressure across theelement rises exponentially. The quantity, size,shape and arrangement of the pores throughoutthe element accounts for why some elements lastlonger than others.

For a given filter media thickness and filtrationrating, there are fewer pores with cellulose mediathan fibreglass media. Accordingly, thecontaminant loading process would block thepores of the cellulose media element quicker thenthe identical fibreglass media element.

The multilayer fibreglass media element is relativelyunaffected by contaminant loading for a longertime. The element selectively captures the varioussize particles, as the fluid passes through theelement. The very small pores in the media are notblocked by large particles. These downstreamsmall pores remain available for the large quantityof very small particles present in the fluid.


22

Filter Contamination Loading Curve

Time

Diff

eren

tial P

ress

ure

Incremental

Life

Filtration Fact

As an element loads withcontamination, the differentialpressure will increase over time;slowly at first, then very quickly asthe element nears it’s maximum life.


Filter Element Life Profile

Every filter element has a characteristic pressuredifferential versus contaminant loading relationship.This relationship can be defined as the “filterelement life profile.” The actual life profile isobviously affected by the system operatingconditions. Variations in the system flow rate andfluid viscosity affect the clean pressure differentialacross the filter element and have a well-definedeffect upon the actual element life profile.

The filter element life profile is very difficult toevaluate in actual operating systems. The systemoperating versus idle time, the duty cycle and thechanging ambient contaminant conditions all affectthe life profile of the filter element. In addition,precise instrumentation for recording the change inthe pressure loss across the filter element isseldom available. Most machinery users anddesigners simply specify filter housings withdifferential pressure indicators to signal when thefilter element should be changed.

The Multipass Test data can be used to developthe pressure differential versus contaminant loadingrelationship, defined as the filter element life profile.As previously mentioned, such operatingconditions as flow rate and fluid viscosity affect thelife profile for a filter element.

Life profile comparisons can only be made whenthese operating conditions are identical and thefilter elements are the same size.

Then, the quantity, size, shape, and arrangementof the pores in the filter element determine thecharacteristic life profile. Filter elements that aremanufactured from cellulose media, single layerfibreglass media and multilayer fibreglass media allhave a very different life profile. The graphiccomparison of the three most common mediaconfigurations clearly shows the life advantage ofthe multilayer fibreglass media element.

23

00 5 10 15 20 25 30 35 40 45 50

10

20

30

40

50

60

70

80

90 6

5

4

3

2

1

100

CAPACITY (GRAMS)

Cellulose MultilayerFibreglass

Single LayerFibreglass

DIF

FER

EN

TIA

L P

RE

SS

UR

E (P

SI)

DIF

FER

EN

TIA

L P

RE

SS

UR

E (b

ar)

Element Types Life Comparison


Filter Housing Selection

Pressure Ratings

Location of the filter in the circuitis the primary determinant ofpressure rating. Filter housingsare generically designed forthree locations in a circuit:suction, pressure, or returnlines. One characteristic ofthese locations is theirmaximum operating pressures.Suction and return line filters aregenerally designed for lowerpressures up to 34 bar.Pressure filter locations mayrequire ratings from 100 bar to420 bar. It is essential to analysethe circuit for frequent pressure

spikes as well as steady stateconditions. Some housings haverestrictive or lower fatiguepressure ratings. In circuits withfrequent high pressure spikes,another type housing may berequired to prevent fatiguerelated failures.

Filter Housings

The filter housing is the pressure vessel whichcontains the filter element. It usually consists oftwo or more sub-assemblies, such as a head (orcover) and a bowl to allow access to the filterelement. The housing has inlet and outlet portsallowing it to be installed into a fluid system.Additional housing features may include mountingholes, bypass valves and element conditionindicators.

The primary concerns in the housing selectionprocess include mounting methods, portingoptions, indicator options, and pressure rating. All,except the pressure rating, depend on the physicalsystem design and the preferences of the designer.Pressure rating of the housing is far less arbitrary.This should be determined before the housing styleis selected.


24

Filtration Fact

Always use anelement conditionindicator with anyfilter, especially thosethat do not have abypass valve.

Visual / electrical elementcondition indicator

Drain Port

Pressure Housing

Filter Element

Inlet Port

Bypass valveAssembly


The Bypass Valve

The bypass valve is used toprevent the collapse or burst ofthe filter element when itbecomes highly loaded withcontaminant. It also preventspump cavitation in the case ofsuction line filtration. Ascontaminant builds up in theelement, the differential pressureacross the element increases. Ata pressure well below the failurepoint of the filter element, thebypass valve opens, allowingflow to go around the element.

Some bypass valve designshave a “bypass to-tank” option.This allows the unfiltered bypassflow to return to tank through athird port, preventing unfilteredbypass flow from entering thesystem. Other filters may besupplied with a “no bypass” or“blocked” bypass option. Thisprevents any unfiltered flow fromgoing downstream. In filters withno bypass valves, highercollapse strength elements arestrongly recommended,especially in high pressurefilters. Applications for using a“no bypass” option includeservo valve and other sensitivecomponent protection. Whenspecifying a non-bypass filterdesign, make sure that theelement has a differentialpressure rating close tomaximum operating pressure ofthe system. When specifying abypass type filter, it can generallybe assumed that themanufacturer has designed theelement to withstand the bypassvalve differential pressure whenthe bypass valve opens.

After a housing style andpressure rating are selected, thebypass valve setting needs tobe chosen. The bypass valvesetting must be selected beforesizing a filter housing. Everythingelse being equal, the highestbypass cracking pressureavailable from the manufacturershould be selected. This willprovide the longest element lifefor a given filter size.

Occasionally, a lower settingmay be selected to helpminimize energy loss in asystem, or to reduce back-pressure on anothercomponent. In suction filters,either a 0.14 bar or 0.2 barbypass valve is used tominimise the chance of potentialpump cavitation.

25

Filtration Fact

An element loadingwith contaminant willcontinue to increasein pressure differentialuntil either:• The element is replaced.• The bypass valve opens.• The element fails.

0

2

Beta Performance Lost by Cyclic Flow and Bypass Leakage.

Eff

ecti

ve F

iltra

tio

n R

atio

B10

4

6

Steady F

low–No Le

akag

e

Unsteady Flow–No Leakage

8

10

0 2 4 6 8 10 12

12

Unsteady Flow–10% Leakage



B10 From Multipass Test

BetaLost byCyclicFlow

0 bar

BlockedBypass Filter

66 bar

69 bar

Filter

(ElementsBlocked)

Flo

w69 bar


Filter Housing Selection

Element Condition Indicators Housings And Element Sizing

The element condition indicator signals when theelement should be cleaned or replaced. Theindicator often has calibration marks which alsoindicates if the filter bypass valve has opened. Theindicator may be mechanically linked to the bypassvalve, or it may be an entirely independentdifferential pressure sensing device. Indicators maygive visual, electrical or both types of signals.Generally, indicators are set to trip anywhere from5%-25% before the bypass valve opens.

The filter housing size should be large enough toachieve at least a 3:1 ratio between the bypassvalve setting and the pressure differential of thefilter with a clean element installed.

For example, the graph on the next page illustratesthe type of catalogue flow/pressure differentialcurves which are used to size the filter housing. As can be seen, the specifier needs to know theoperating viscosity of the fluid, and the maximumflow rate (instead of an average) to make sure thatthe filter does not spend a high portion of time inbypass due to flow surges. This is particularlyimportant in return line filters, where flowmultiplication from cylinders may increase thereturn flow compared to the pump flow rate.

If the filter described in the graph was fitted with a3.5 bar bypass valve the initial (clean) pressuredifferential should be no greater than 1.1 bar. Thisis calculated from the 3:1 ratio of bypass settingand initial pressure differential.


26

Filtration Fact

Always consider low temperatureconditions when sizing filters.Viscosity increases in the fluid maycause a considerable increase inpressure differential through thefilter assembly.

Filter Element Sizing

Diff

eren

tial

Pre

ssu

re

3:1Minimum

Ratio

CleanElement

P

FilterBypass

CrackingPressure

LIF

E


Most standard filter assembliesutilize a bypass valve to limit themaximum pressure drop acrossthe filter element. As the filterelement becomes blocked withcontaminant, the pressuredifferential increases until thebypass valve cracking pressureis reached. At this point, theflow through the filter assemblybegins bypassing the filterelement and partly flowsthrough the bypass valve. Thisaction limits the maximumpressure differential across thefilter element. The importantissue is that some of thecontaminant particles within thesystem fluid also bypass thefilter element. When thishappens, the effectiveness ofthe filter element iscompromised and the attainablesystem fluid cleanlinessdegrades. Standard filterassemblies normally have abypass valve cracking pressureset at between 0.8 and 7 bar.

The relationship between thestarting clean pressuredifferential across the filter

element and the bypass valvepressure setting must beconsidered. A cellulose elementhas a narrow region ofexponential pressure rise.

For this reason, the relationshipbetween the starting cleanpressure differential and thebypass valve pressure setting isvery important. This relationshipin effect determines the usefullife of the filter element.

In contrast, the useful elementlife of the single layer andmultilayer fibreglass elements isestablished by the nearlyhorizontal, linear region ofrelatively low pressure dropincrease, not the region ofexponential pressure rise.Accordingly, the filter assemblybypass valve cracking pressure,whether 0.8 or 7 bar, hasrelatively little impact on theuseful life of the filter element.Thus, the initial pressuredifferential and bypass valvesetting is less of a sizing factorwhen fibreglass media is beingconsidered.

27

Filtration Fact

Pressure differential in a filter assemblydepends on:1. Housing and element size2. Media grade3. Fluid viscosity4. Flow rate5. Fluid Density

Typical Flow / Pressure Curves For a Specific Media28P-2 High Collapse Elements Only

43.5

29.0

0

0 13 26 66

Flow (US GPM)

Flow (l/min)50 100 250200

0.0

∆p (

bar

) 20QH

1.0

2.0

3.0

0

0.5

1.5

2.5

53

14.5

∆p (

psi

d)

10QH05QH02QH

150 300

39 79


Types & Locations of Filters

Air Filter

The forgotten system filter, the air filter is animportant, integral part of the contamination controlpackage. Any breathing system (one which allowsair to be drawn into and expelled from, the fluidreservoir during system operation) will require an airfilter. A good quality air filter, sized to meet theneeds of the system components, will be aneffective barrier against the ingress of contaminants.Effective contamination control can be attained byjust removing the contaminants that enter the fluidsystem, however, how much more effective wouldthe system filters be, if the contaminants beingingested by a breathing system were preventedfrom entering the system? Why allow contaminantsto enter the system and then spend time & moneytrying to remove them? Fit a fine, high capacity EABor ABL environmentally friendly air filter and preventthe initial ingress, this way, the system filters can betaking out contaminants generated from within thesystem itself.

Pressure filters are located downstream from thesystem pump. They are designed to handle thesystem pressure and sized for the specific flowrate in the pressure line where they are located.

Pressure filters are especially suited for protectingsensitive components directly downstream fromthe filter, such as servo valves. Located justdownstream from the system pump, they also helpprotect the entire system from pump generatedcontamination.Suction Filters

Filter Types & Locations

• Air Filter• Suction• Pressure• Return• Off-line


28

Suction filters serve to protect the pump from fluidcontamination. They are located before the inlet portof the pump. Some may be inlet “strainers”,submersed in the fluid. Others may be externallymounted. In either case, they utilise relatively coarseelements, due to cavitation limitations of pumps. Forthis reason, they are not used as primary protectionagainst contamination. Some pump manufacturesdo not recommend the use of a suction filter. Alwaysconsult the pump manufacturer for inlet restrictions.

Filtration Fact

Suction strainers are often referredto by “mesh” size:60 mesh = 238 micron100 mesh = 149 micron200 mesh = 74 micron

Suction Filter

To System

Pressure Filters

To System

Pressure Filter


Return Filters

When the pump is the mostsensitive component in a system,a return filter may be the bestchoice. In most systems, thereturn filter is the last componentthrough which fluid passes beforeentering the reservoir. Therefore,it captures wear debris fromsystem working components andparticles entering through worncylinder rod seals before suchcontaminant can enter thereservoir and be circulated.Since this filter is locatedimmediately upstream from thereservoir, its pressure rating andcost can be relatively low.

In some cases, cylinders withlarge diameter rods may resultin “flow multiplication”. Theincreased return line flow ratemay cause the filter bypassvalve to open, allowing unfilteredflow to pass downstream. Thismay be an undesirable conditionand care should be taken insizing the filter.

Both pressure and return filterscan commonly be found in aduplex version. Its most notablecharacteristic is continuousfiltration. That is, it is made withtwo or more filter chambers andincludes the necessary valvingto allow for continuous,uninterrupted filtration. When afilter element needs servicing,the duplex valve is shifted,diverting flow to the opposite

29

Duplex Filter Assembly

filter chamber. The dirty elementcan then be changed, whilefiltered flow continues to passthrough the filter assembly. Theduplex valve typically is an opencross-over type, which preventsany flow blockage.

Cylinder has 2:1ratio piston areato rod diameter.

Return line filter is sizedfor 250 lpm.

125 lpm

Return Line Filter


Types & Locations of Filters

Off-Line Filtration

Also referred to as recirculating, kidney loop, orauxiliary filtration, this filtration system is totallyindependent of a machine’s main hydraulic system.Off-line filtration consists of a pump, filter, electricalmotor, and the appropriate hardware connections.These components are installed off-line as a smallsub-system separate from the working lines, orincluded in a fluid cooling loop. Fluid is pumped outof the reservoir, through the filter, and back to thereservoir in a continuous fashion. With this“polishing” effect, off-line filtration is able to maintaina fluid at a constant contamination level. As with areturn line filter, this type of system is best suited tomaintain overall cleanliness, but does not providespecific component protection. An off-line filtrationloop has the added advantage that it is relativelyeasy to retrofit on an existing system that hasinadequate filtration. Also, the filter can be servicedwithout shutting down the main system. Mostsystems would benefit greatly from having acombination of suction, pressure, return, and off-line filters. The table on the opposite page may behelpful in making a filtration location decision.


30

Filtration Fact

The cleanliness level of a system is directly proportional to the flowrate over the system filters.

Off-Line Filter

Pump

Off-LineFilter

Optional Cooler

Air FilterExisting

Hydraulicor LubeSystem

Flow Rate Effect on Off-Line FiltrationPerformance

.01

.1

23/21/18

20/18/1519/17/14

18/16/1316/14/12

15/13/10

For beta rated filters witha minimum rating of beta (10) = 75

(Number of particles > 10 micron ingressing per minute)

Source based on Fitch, E.C., Fluid Contamination Control, FES, Inc.,Stillwater, Oklahoma, 1988.

Num

ber

of p

artic

les

upst

ream

per

milli

litre

gre

ater

than

refe

renc

e si

ze

ISO

Cor

rela

tion

1

10

1 G

PM (3

.8 lp

m)

10

GPM

(38

lpm

)

1

00 G

PM (3

80 lp

m)

102

103

103 104 105 106 107 108 109 1010 1011 1012

104

105

106

Ingression rate


Comparison of Filter Types and Locations

31

Filter Location Advantages Disadvantages

Air Filter • By preventing initial ingress, removal • Initial costby the system filter is not needed. • Location can encourage damage

• High capacity. • Oil leakage• Easy access for servicing.• Cost effective.• Environmentally friendly• Can be used to remove both

particulates and water.

Suction • Last chance • Must use relatively(Externally protection for the pump. coarse media, and/or largeMounted) housing size, to keep

pressure drop low due to pump inlet conditions.

• Cost is relatively high.• Much easier to • Does not protect

service than a downstreamsump strainer. Components from pump

wear debris.• May not be suitable for

many variable volumepumps.

• Minimum system protection.

Pressure • Specific component • Housing is relativelyprotection expensive because it

• Contributes to overall must handle full systemsystem cleanliness level. pressure.

• Can use high • Does not catch wear efficiency, fine filtration, debris from downstream

filter elements. working components.• Catches wear debris from pump

Return • Catches wear • No protection fromdebris from components, pump generatedand dirt entering contamination.through worn cylinder • Return line flow surgesrod seals before it enters may reduce filterthe reservoir. performance.

• Lower pressure • No direct componentratings result in lower protection.costs.

• May be in-line or in-tank for easier installation.

• Relative initial cost is low.

Off-Line • Continuous “polishing” of • Relative initial cost is high.the main system hydraulic • Requires additional space.fluid, even if the system is • No direct componentshut down. protection.

• Servicing possible withoutmain system shut down.

• Filters not affected by flowsurges allowing for optimumelement life and performance.

• The discharge line can bedirected to the main systempump to provide superchargingwith clean, conditioned fluid.

• Specific cleanliness levelscan be more accuratelyobtained and maintained.

• Fluid cooling may be easilyincorporated.


Fluid Analysis

Portable Particle Counter

The most important development withinthe field of fluid system maintenance isthe Portable Particle Counter.Developed to allow on site, rapididentification of the levels of particulatesin systems, these instructions are nowthe accepted way of monitoring levelsof solids in fluid systems.

Capable of accurately and repeatedlyreporting levels of particulates down to2 microns in size, they are alsolightweight, portable and reliable.

With a test taking typically 2 minutes,laser particle counters offer portablecounts and cleanliness codes. UsuallyISO and NAS.

For water content, viscosity andspectrometer analysis, samples shouldbe sent to a certified laboratory.

Filter Types & Locations

• Patch Test• Portable Particle Counter• Laboratory Analysis

Fluid analysis is an essential part of anymaintenance programme. Fluid analysis ensuresthat the fluid conforms to manufacturerspecifications, verifies the composition of the fluid,and determines its overall contamination level.


32

Filtration FactAny fluid analysis should always include aparticle count and corresponding ISO code.

Laboratory Analysis

The laboratory analysis is a completelook at a fluid sample. Most qualifiedlaboratories will offer the following testsand features as a package:

• Viscosity at 90°CViscosity at 100°C

• Viscosity Index

• Neutralisation number

• Water content

• Particle counts

• Spectrometric analysis (wear metalsand additive analysis reported inparts per million, or ppm)

• Trending graphs

• Photo micrograph

• Recommendations

In taking a fluid sample from a system,care must be taken to make sure thatthe fluid sample is representative of thesystem.

To accomplish this, the fluid must bedrawn into a certified clean containerthe fluid must be correctly extractedfrom the system.

When it is impossible to run an on-lineanalysis, it is acceptable to drain fluid intoa clean container, for analysis away fromsite. ISO 4021 (1992) is the acceptedstandard for extracting fluid samplesfrom an operating hydraulic fluid systemand should be followed at all times.

The goal is a representative fluid sample,one which, as closely as possible,reflects the condition of the system fluid.

1st The system should have been atoperating temperature for at least30 minutes before the sample istaken.

2nd Sampling valves should be openedand flushed for at least 15 seconds.

3rd The clean sample bottle should bekept sealed until the fluid andvalve are ready for sampling.

A complete procedure follows in theappendix.

Filtration FactThe only way to know thecondition of a fluid isthrough fluid analysis.Visual examination is notan accurate method.


Appendix


Sampling Procedure

Obtaining a fluid sample for particle counts and / or analysis involves important steps to make sure you aregetting a representative sample. Often erroneous sampling procedures will disguise the true nature ofsystem cleanliness levels. Use one of the following methods to obtain a representative system sample.

This is applicable whether on line or bottle sampling is being done. However, bottle sampling is particularlysusceptible to error, due to the number of opportunities for contaminants to enter the samples.

33

1. For systems with a sampling valveA. Operate system for at least 30 minutes.B. With the system operating, open the sample

valve allowing 200ml to 500 ml (7 to 16ounces) of fluid to flush the sampling port.(The sample valve design should provideturbulent flow through the sampling port.)

C.1. Online SamplingConnect the online particle counter and runsamples until a minimum of 3 consecutivecomparable samples are obtained.

C.2. Bottle SamplingUsing a wide mouth, pre-cleaned samplingbottle, remove the bottle cap and place inthe stream of flow from the sampling valve.Do NOT “rinse” out the bottle with initialsample. Do not fill the bottle more than 80% full.

D. Close the sample bottle immediately. Next,close the sampling valve. (Make priorprovision to “catch” the fluid while removingthe bottle from the stream.)

E. Label the sample bottle with pertinent data:include date, machine number, fluid supplier,fluid number code, fluid type, and timeelapsed since last sample (if any).

2. Systems without a sampling valveA. Operate the system for at least 30 minutes.B. Use a small hand-held vacuum pump bottle thief

or “basting syringe” to extract sample. Insertsampling device into the tank to one half of thefluid height. You will probably have to weight theend of the sampling tube. Your objective is toobtain a sample in the middle portion of thetank. Do not let the syringe or tubing come intocontact with the side of the tank.

C. Put extracted fluid into an approved, pre-cleaned sample bottle as described in thesampling valve method above.

D. Cap immediatelyE. Label with information as described in

sampling valve method.

Regardless of the method being used, observecommon sense rules. Any equipment which isused in the fluid sampling procedure must bewashed and rinsed with a filtered solvent. Thisincludes vacuum pumps, syringes and tubing.Your goal is to count only the particles already inthe system fluid. Dirty sampling devices and non-representative samples will lead to erroneousconclusions and cost more in the long run.


Appendix

Parker Cleanliness Service Report Example


34

Filtration Fact

Rule of thumb: size the pump flow of an off-line package at aminimum of 10% of the mainreservoir volume.


3 Parker Filtration Products With One Aim

Contamination Control Solutions

Knowing how contaminated your oil is and knowing how to clean it to approved standards are key issuesbut with simple solutions.

Do you know how dirty your oil is?Parker Filtration has the cost effective solutions. Hand-held Oilcheck to monitor oil cleanliness, Guardianportable filter systems and Par-Fit interchange replacement elements - quality products and effectivesolutions to reduce equipment downtime caused by fluid contamination.

35

Parker Oilcheck know the condition of the oil in your system

With Parker Oilcheck, you can check your oil condition any time, any place andanywhere. Hand-held oilcheck provides an operator with a comparison betweennew and used oils and potentially gives a warning of impending engine failure.Parker Oilcheck will save you money and reduce the risk of equipment downtime.

Parker Guardian The first line ofdefence in protecting your hydraulic Systemagainst contamination.

The Guardian portable filtration system is aunique pump/motor/filter combinationdesigned for transferring mineral, conditioning petroleum-based andwater emulsion fluids. It will protect your system from contamination ingress when addingnew fluid, because new fluid is not necessarily clean fluid.

The Guardian is a supremely robust and portable filtration system that will assist in defending a hydraulicsystem from particulate and or water contamination, removing particulate down to 2µ when fitted with theappropriate dedicated element. The guardian is ideal as an offline filtration/conditioning system on yourhydraulic system reservoir.

Parker Par-FitParker Filtration’s quality range of interchangeablehydraulic elements numbers in the thousands.

Genuine Parker elements are available for almost everymanufacturer in the world and that quality in manufacturecan very often mean that Parker element performs to ahigher standard than the original it is replacing.

Visit the Par-Fit online element selector atwww.parker.com/parfit and discover for yourself just how extensive our range of interchangeable elements is. That’s why we say ‘Fit Par-Fit Fit Quality.

19 to 2626 to 4040 to 55

55+17

17 to 238.6

10 to 2632 to 86

107 to 430650

54.5

99210

100

50

9213132434649526371

93

139

91826283538404453606170798896105114123131

4693139148185200213232278315324371417464510556602649695

591415182021232731323641455054596468

Rounded Actual


Appendix

Quick Converter


36

0.21.12.24.46.68.811.013.215.417.619.822.0

Imperial Gallons

33.044.055.066.077.088.099.0110.0121.0132.0143.0154.0165.0176.0187.0198.0209.0220.0

0.22001.09982.19974.39946.59918.798810.998513.198115.397817.597519.797221.9969

32.995443.993854.992365.990776.989287.987798.9861109.9846120.9830131.9815142.9799153.9784164.9769175.9753186.9738197.9722208.9707219.9692

0.2641.3212.6425.2837.92510.56713.20915.85018.49221.13423.77526.417

39.62652.83466.04379.25292.460105.669118.877132.086145.295158.503171.712184.920198.129211.338224.546237.755250.963264.172

0.31.32.65.37.910.613.215.918.521.123.826.4

39.652.866.079.392.5105.7118.9132.1145.3158.5171.7184.9198.1211.3224.5237.8251.0264.2

15102030405060708090100

1502002503003504004505005506006507007508008509009501000

0.010.010.020.030.030.040.050.060.060.07

0.10.20.30.30.40.50.60.60.71.42.12.83.46.913.820.727.634.5

0.006890.013790.020680.027580.034470.041370.048260.055160.062050.06895

0.137900.206840.275790.344740.413690.482630.551580.620530.689481.378952.068432.757903.447386.8947613.7895220.6842827.5790434.47380

1.4502.9014.3515.8027.2528.70210.15311.60313.05314.504

29.00843.51158.01572.51987.023101.526116.030130.534145.038290.075435.113580.151725.1891450.3772900.7544351.1315801.5087251.885

1.52.94.45.87.38.7

10.211.613.114.5

29.043.558.072.587.0

101.5116.0130.5145.0290.1435.1580.2725.21450.42900.84351.15801.57251.9

0.10.20.30.40.50.60.70.80.91.0

2.03.04.05.06.07.08.09.010.020.030.040.050.0100.0200.0300.0400.0500.0

Actual Rounded

US GallonsLitresRounded Actual

Bar

Actual Rounded

PSIDBarpsid

cSt ISO - VG CentiposeSG

(0.876)

SUS (SSU)4.635 0.454

SSF

Viscosity Conversion Chart

10203032404346506068708090100110120130140150

FluidViscosity (cSt)Weight

At Temp

°C

SAE to Centistokes

SAE 10SAE 20SAE 30SAE 40SAE 40SAE 50

#2 Fuel Oil#4 Fuel Oil#5 Fuel OilBunker C#6 Fuel Oil

ConversionFactor = cSt x

Comparisons are made at 38 degrees CcSt; CentistokesISO; International Standards OrganisationCentipoise; CentipoiseSUS; Saybolt Universal Seconds (same as SSU)SSU; Saybolt Seconds Universal (same as SUS)SSF; Seconds Saybolt Furol

============

============

==================

==================

==========

==========

==================

==================

>

<


Common Conversions

37

AtmosphereAtmosphereAtmosphere

BarBar

MillibarPascal (Pa)Pascal (Pa)

To Convert

PressureBarPSI

Ins HgKg/sq Metre

PSIIns Hg

BarPSI

Into....

1.0132514.6959529.9212610,2000.069

0.029529990.000010.000145

Multiply by....

CentimetresCentimetres

MetresMetresMetresMicronsMicronsMicrons

MillimetresMillimetres

DistanceFeet

InchesFeet

InchesYardsInchesMetre

MillimetreFeet

Inches

30.482.54

3.2808339.369961.093610.0000390.0000010.0001

0.003280830.03937

KilojouleKilowatt

Newton MetreNewton Metre

EnergyHorsepowerHoursepower

Inch pound (lb)Foot pound(lb)

0.00037250611.3410228.85074623.73036

CelciusCelcius

Fahrenheit

TemperatureFahrenheit

KelvinKelvin

((OC x 9.5)+32)OC + 273.15

255.9278

Cubic CentimetresCubic CentimetresCubic CentimetresCubic Centimetres

Cubic MetresCubic MetresCubic MetresCubic Metres

LitresLitresLitresLitresLitres

Litres / MinLitres / MinLitres / Min

VolumeCubic Feet

Cubic InchesLitres

US GallonsCubic Feet

Cubic InchesLitres

US GallonsCubic Centimetres

Cubic FeetCubic Inches

GallonsUS Gallons

Cubic Centimetres / MinCubic Feet / Min

Gallons / Min

0.000035210.061020.0000010.0002642

35.31061,0231,000264.201,000

0.03531561.02340.2200830.264170

1,0000.0350.264

GramsKilogramsKilogramsTonnes (t)

MassPounds (lb)

GramsPounds (lb)

Tons (tn)

0.00220461,000

2.204621.102311

Centimetre2

Centimetre2

Centimetre2

Kilometre2

Kilometre2

Kilometre2

Metre2

Metre2

Metre2

AreaInch2

Foot2

Yard2

Inch2

Foot2

Yard2

Inch2

Foot2

Yard2

1,550,0030.0010763910.000119599

155003e +0091076391e +007

1,195,9901,550.00310.763911.19599

BarPSI

Ins HgKg/sq Metre

PSIIns Hg

BarPSI

To Convert

PressureAtmosphereAtmosphereAtmosphere

BarBar

MillibarPascal (Pa)Pascal (Pa)

Into....

0.98692330.068045960.033421059.80665E-05

14.5033.86388100,000

6,894.747

Multiply by....

FeetInchesFeet

InchesYardsInchesMetre

MillimetreFeet

Inches

DistanceCentimetresCentimetres

MetresMetresMetresMicronsMicronsMicrons

MillimetresMillimetres

0.03280830.3940.30480.02540.914425,400

1,000,0001,000

394,80025.40

HorsepowerHoursepower

Inch pound (lb)Foot pound(lb)

EnergyKilojouleKilowatt

Newton MetreNewton Metre

2,684.520.74569990.11298481.355818

FahrenheitKelvinKelvin

TemperatureCelciusCelcius

Fahrenheit

(OF - 32) / 1.8OK - 273.15

-457.866


LitresUS GallonsCubic Feet

Cubic InchesLitres

US GallonsCubic Centimetres


GallonsUS Gallons

Cubic Centimetres / MinCubic Feet / Min

Gallons / Min

VolumeCubic CentimetresCubic CentimetresCubic CentimetresCubic Centimetres

Cubic MetresCubic MetresCubic MetresCubic Metres

LitresLitresLitresLitresLitres

Litres / MinLitres / MinLitres / Min

28,316.8516.38706

1,0003,785.412

0.028316851.638706E-05

0.0010.00378541

0.00128.31685

0.016387064.5443.7850.001

28.316854.546092

Pounds (lb)Grams

Pounds (lb)Tons (tn)

MassGrams

KilogramsKilogramsTonnes (t)

453.59240.001

0.45359240.9071847

Inch2

Foot2

Yard2

Inch2

Foot2

Yard2

Inch2

Foot2

Yard2

AreaCentimetre2

Centimetre2

Centimetre2

Kilometre2

Kilometre2

Kilometre2

Metre2

Metre2

Metre2

6.4516929.03048,361.274

6.4516e -0109.290304e -0088.361274e -007

0.000645160.092903040.8361274

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Documents

The Handbook of Hydraulic Filtration · and gas filtration and separation, fuel conditioning and filtration, hydraulic and lubrication filtration, fluid power products and fluid condition