Particle MeasurementTechnology in Practice.From Theoryto Application.

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Introduction toParticle Counting

1.1 Physics Fundamentals

1.1.1 Light Obscuration

1.1.2 Mesh Blocking Process

1.1.3 Process Limits

1.2 Test Dust

1.2.1 ACFTD / ISO MTD

1.2.2 Particle Sizes

1.2.3 Calibration standardISO 11171:1999

1.2.4 Calibration standardISO 11943:1999

1.3 ContaminationClassification

1.3.1 ISO 4406

1.3.2 SAE AS 4059

1.3.3 NAS 1638

The Right Tool for the Job

2.1 Product Overviewand Applications

2.2 Temporary Measurementand Fluid Service

2.3 Continuous Online Analysisin Test Rigs for DeterminingSurface Cleanliness

2.4 Continuous OnlineMeasurement in Hydraulic andLubrication Systems forCondition Monitoring

2.4.1 Typical InstallationExamples

2.4.1.1 Filter-Cooler /Heater Circuit

2.4.1.2 Pressure Circuit

2.4.1.3 Leakage Oil FlowMonitoring

2.4.1.4 Lubrication OilMonitoring

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2.4.2 General InstallationRecommendations

2.4.3 Conditioning Modules

2.5 Laboratory Equipment

Imprint3

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1 Introduction toParticle Counting

1.1Physics Fundamentals

1.1.1Light Obscuration

In optical contamination sensors,a beam of light is transmittedthrough the oil flow.On the reception side, the lightis obscured by the particles.

Fig. 1No obscuration of the light beam

Fig. 2Obscuration of the lightbeam by particles

The reception signal looks like thison an oscilloscope:

Fig. 3Reception Signal

Signal conversion:

Each of the signal peakscorresponds to obscurationby a particle.

The signal height or amplitudereflects the particle size.

The breakdown into 2, 5, 15, 25 µmand 4, 6, 14, 21 µm(c)

is determined via the thresholdvalues.

The principle of particle countingvia light obscuration is used in thesensors presented in section 2.

Oilflow

Lightsource

Photo-detector

Oilflow

Lightsource

Photo-detector

Particles

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1.1.2Mesh Blocking Process

The fluid flow is conveyedthrough one or more meshes.In so doing, the particles containedin the fluid are retained by themesh, thus generating a pressuredifferential (∆p) at the site of themesh inlet and outlet.

Increases in ∆p over time (t)provide information about particleloading.

Fig. 4MeshBlockage Sensor MBS 1000

Advantages:Mesh Blocking Processcan be used for

emulsions

high particle loading

opaque fluids

Disadvantages:

only trend monitoring is possible

no information on particle countspossible

no particle distributionmeasurement possible

no traceability to a calibrationstandard offered

1.1.3Process Limits

When measuring particulatecontamination using the sensorsdescribed in section 2, the oilcleanliness may not be aboveor below specific limits.

If the oil is “too clean” no particlereadings can be captured.The lower process limit isapproximately ISO 9/8/7.

Excess contamination leads tocoincidence (= temporal meetingof two or more signals caused byseveral particles aligned in thesame plane), rendering particlemeasurement no longer possible.This problem is encounteredwith cleanliness classes overISO 25/24/23.

Particle counting in emulsionsis not possible employingoptical methods. The principleof light obscuration is limitedto particles over 1 µm(c) in size.

For oil cleanliness classesof less than ISO 14/12/10,the direct comparison of an onlinemeasurement with an oil sampleis not always possible.Additional error sources whentaking oil samples:

contamination of environment

altered flow conditionsat sampling point

variable contamination atdifferent sampling points(tank, pressure line, offline circuit)

procedure for oil sampling(e.g. cleanliness of samplingadapter, fluid volume, machinecycle)

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1.2Test Dust

1.2.1ACFTD / ISO MTD

Until 1992 ACFTD (Air CleanerFine Test Dust) was valid as test dust.

Starting in 1997, a new test dust, ISO MTD(ISO Medium Test Dust) was stipulatedin ISO 12103-A3. ISO MTD forms the basisfor the SRM 2806 (Standard Reference Material)developed by the NIST (National Instituteof Standards and Technology, USA).

The ISO MTD dust is used for calibrating automaticparticle counters subject to calibration standardsISO 11171:1999 and ISO 11943:1999.

1.2.2Particle Sizes

In ACFTD dust the longest particledimension is used to specify size.

With the introduction of ISO 11171:1999,a new definition of particle sizes was stipulated.The standard defines the diameter of anarea-equivalent particle of ISO MTD dustas the particle size.Particle size specifications according to ISO11171:1999, the new calibration standard, containthe index(c), example: 4 µm(c), designatingthe calibration material used, certified andtraceable to a national standard.This notation is also used in the revisedISO 4406:1999 and the new ISO 11943:1999.

Fig. 5Particle size definition

1.2.3Calibration standard ISO 11171:1999

The ISO 11171:1999 calibration standard coversthe calibration of automatic particle counters for fluids.This standard is applied in the primary calibrationof laboratory particle counters. A suspensioncontaining ISO MTD contamination is usedfor calibration.

The reference particle counters used by HYDACand the ALPC Automated Laboratory Particle Counterare calibrated on the basis of ISO 11171:1999.

Fig. 6ALPC Automated Laboratory Particle Counter

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1.2.4Calibration standardISO 11943:1999

The ISO 11943:1999 calibrationstandard covers the calibrationof automatic online particlecounters for fluids.This standard is applied in thesecondary calibration of onlinelaboratory particle counters.

Fig. 8ContaminationSensors CS 1000 and CS 2000

The same ISO MTD contamination is usedas in ISO 11171:1999.

ISO 11943:1999 stipulates that online particle countersare connected in a hydraulic circuit with reference particlecounters calibrated according to ISO 11171:1999.

Fig. 9Schematic of a Calibration Test Rig

Fig. 7FluidControl Unit FCU 2000

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1.3ContaminationClassification

For a concise reference containingreference photographs, please referto our Contamination Handbook onfluid monitoring (stock no. 349339).

1.3.1ISO 4406

In ISO 4406, particle counts aredetermined cumulatively, i.e.> 4 µm(c), > 6 µm(c) and > 14 µm(c)

(manually by filtering the fluidthrough an analysis membraneor automatically using particlecounters) and allocatedto measurement codes.The goal of allocating particlecounts to codes is tofacilitate the assessmentof fluid cleanliness ratings.In 1999 the “old” ISO 4406:1987was revised and the size rangesof the particle sizes undergoinganalysis redefined.

The counting method and calibrationwere also changed. This is importantfor the user in his everyday work:

Even though the measurementcodes of the particles undergoinganalysis have changed, thecleanliness code will change onlyin individual cases. When draftingthe “new” ISO 4406 care was takento ensure that not all the existingcleanliness provisions for systemshad to be changed (Lit. ©HYDAC,“Filters- Power Fluid Technology,New Test Dust, New Calibration,New Filter Testing Methods – HowThis Impacts Everyday Work”).

Size ranges

Dimensiondetermined

Test dust

Comparablesize ranges

“Old” ISO 4406:1987

> 5 µm> 15 µm

Longestdimensionof a particle

ACFTD-dust

Old ACFTD-Calibration

ISO 12103-1A1

ISO 12103-1A2

ISO 12103-1A3

ISO 12103-1A4

NewNIST calibration

4 µm(c)

6 µm(c)

14 µm(c)

“New” ISO 4406:1999

1-10 µmultrafine fraction

SAE Fine,AC-Fine

SAE 5-80 µmISO MTDCalibration dustfor particlecounters

SAE CoarseCoarse fraction

ComparableACFTD dusts

< 1 µm4.3 µm15.5 µm

Overview of the changes:

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> 4 µm(c)

> 6 µm(c)

> 14 µm(c)

Diameterof the area-equivalent circleISO 11171:1999

Allocation of particle countsto cleanliness classes:

No. of particles / ml Clean-linessclass

Over Up to

2,500,000 > 281,300,000 2,500,000 28640,000 1,300,000 27320,000 640,000 26160,000 320,000 2580,000 160,000 2440,000 80,000 2320,000 40,000 2210,000 20,000 215,000 10,000 202,500 5,000 191,300 2,500 18640 1,300 17320 640 16160 320 1580 160 1440 80 1320 40 1210 20 115 10 10

2.5 5 91.3 2.5 8

The reproducibility of the resultsin cleanliness class 8 dependson the concentration of particlesin the sample undergoing analysis.If the number of particles countedin the sample is fewer than 20,the result has to be reported with ≥.

Example: 14/12/≥8

Note: increasing the measurementcode by 1 causes the particle countto double.

Example: ISO class 18 / 15 / 11 saysthat the following are found in 1 ml ofanalyzed sample:

1,300 - 2,500 particle > 4 µm(c)

160 - 320 particle > 6 µm (c)

10 - 20 particle > 14 µm(c)

Fig. 10Microscopic Examinationof an Oil Sample (100 ml),Magnification 100x(ISO 18/15/11)

1.3.2SAE AS 4059

Like ISO 4406, SAE AS 4059describes particle concentrationsin liquids. The analysis methodscan be applied in the same manneras ISO 4406:1999 and NAS 1638.

The SAE cleanliness classesare based on particle size,number and distribution.The particle size determineddepends on the measurementprocess and calibration,consequently the particle sizesare labeled with letters (A - F).

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The following table shows thecleanliness classes in relationto the particle concentrationdetermined:

2. Specifying a cleanliness classfor each particle size

Example:

Cleanliness class accordingto AS 4059: 7 B / 6 C / 5 D

Size B (5 µm or 6 µm(c)):38,900 particles / 100 ml

Size C (15 µm or 14 µm(c)):3,460 particles / 100 ml

Size D (25 µm or 21 µm(c)):306 particles / 100 ml

3. Indication of the highestcleanliness class measured

Example:

Cleanliness class according toAS 4059:6 B - F

The 6 B - F specification requiresa particle count in size ranges B - F.

The respective particleconcentration of cleanlinessclass 6 may not be exceededin any of these ranges.

A B C D E F

000 195 76 14 3 1 000 390 152 27 5 1 00 780 304 54 10 2 01 1,560 609 109 20 4 12 3,120 1,220 217 39 7 13 6,250 2,430 432 76 13 24 12,500 4,860 864 152 26 45 25,000 9,730 1,730 306 53 86 50,000 19,500 3,460 612 106 167 100,000 38,900 6,920 1,220 212 328 200,000 77,900 13,900 2,450 424 649 400,000 156,000 27,700 4,900 848 12810 800,000 311,000 55,400 9,800 1,700 25611 1,600,000 623,000 111,000 19,600 3,390 1,02012 3,200,000 1,250,000 222,000 39,200 6,780

> 1 µm> 5 µm >15 µm > 25 µm > 50 µm > 100 µm

> 4 µm(c) > 6 µm(c) > 14 µm(c) > 21 µm(c) > 38 µm(c) > 70 µm(c)

Size ISO 4402Calibration or opticalcounting*

Size ISO 11171,Calibration or electronmicroscope**

Size coding

* Particle sizes measuredaccording to the longestdimension.

** Particle sizes determinedaccording to the diameterof the projected area-equivalentcircle.

The SAE cleanliness classes canbe represented as follows:

1. Absolute particle count largerthan a defined particle size

Example:

Cleanliness class accordingto AS 4059:6

The maximum permissible particlecount in the individual size rangesis bold-faced in the above table.

Cleanliness class accordingto AS 4059:6 B

Size B particles may not exceedthe maximum number indicatedfor class 6.

6 B = max. 19,500 particles of sizeof 5 µm or 6 µm(c)

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Classes

Maximum particle Concentration [particles/100 ml]

1.3.3NAS 1638

Like ISO 4406 and SAE AS 4059,NAS 1638 describes particleconcentrations in liquids.

This standard is now obsolete butoften used in practice.The analysis methods canbe applied in the same manneras ISO 4406:1999.

Increasing the class by1 causes the particle countto double on average.

The maximum particle countsof class 10 are bold-facedin the above table.

Fig. 11Microscopic Examinationof an Oil Sample (100 ml),Magnification 100x (NAS 10)

Particle size [µm]

5-15 15-25 25-50 50-100 >100No. of particles in 100 ml sample

00 125 22 4 1 00 250 44 8 2 01 500 89 16 3 12 1,000 178 32 6 13 2,000 356 63 11 24 4,000 712 126 22 45 8,000 1,425 253 45 86 16,000 1,850 506 90 167 32,000 5,700 1,012 180 328 64,000 11,600 2,025 360 649 128,000 22,800 4,050 720 12810 256,000 45,600 8,100 1,440 25611 512,000 91,200 16,200 2,880 51212 1,024,000 182,400 32,400 5,760 1,024

Cleanlinessclass

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In contrast to ISO 4406, certainparticle size ranges are countedin NAS 1638 and allocatedto these measurement codes.

The following table shows thecleanliness classes in relationto the particle concentrationdetermined.

2 The Right Toolfor the Job

2.1Product Overviewand Applications

Fig. 12Product Overview

FluidControl Units (FCU) areoffered for temporary measurementand fluid service purposes.The Contamination Sensors (CS)are designed for stationaryapplications in hydraulic/lubesystems and test rigs.These sensors are also availableas units featuring a motor-pumpassembly, patented air suppression,and optional installation for theAS 1000 AquaSensor and HYDACLab®.

CS 2000 CSM 2000 CS 1000 CSM 1000 FCU 1000 FCU 2000 FCU 8000 BSU ALPCCSM 2000

Test benches OnBoard

Stationary Service Laboratory

The Bottle Sampling Unit (BSU)combined with the FCU 8000is used for analyzing oil samples.Simplified oil sampling can be donewith FCU 2000 and FCU 1000.The Automated Laboratory ParticleCounter (ALPC) can be usedto analyze up to 500 samples/day.The following table shows thekey differences between theindividual units:

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Fig. 13Typical Applicationsand Suitable Products(and Modules)

The various applications aresubdivided below into:

Temporary Measurementand Fluid Service

Continuous Online Analysisin Test Rigs for DeterminingSurface Cleanliness

Continuous Online Measurement inHydraulic and Lubrication Systemsfor Condition Monitoring

Laboratory Equipment

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2.2Temporary Measurementand Fluid Service

Portable FluidControl Units(FCU) (series 2000) are availablefor temporary measurement

and fluid service purposes.The FCU is available in variouscalibrations and models.All models feature a displaywith a keypad, a knob for adaptingthe flow rate, and an integratedminiature dot-matrix printer. Modelsare also available with/without an

internal pump for automaticallysuctioning fluids from oil samplesor the tank. The FluidControl Unitsare user-friendly and providefor reliable measurement results.

The following table providesa comparison of the various models:

The following prerequisitesapply to using the FCU:

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2.3Continuous OnlineAnalysis in Test Rigsfor DeterminingSurface Cleanliness

Using online particle countersfor checking componentcleanliness is described in detailin ISO 18413. In the process,the test oil is analyzed subsequentto component cleanliness analysis.Test rigs possess several factorswhich render continuous onlineanalysis difficult:

short measurement cycleschanging flow ratesair bubblesoil mixturesgreaseassembly lubricants

Stationary units, i.e.the Contamination Sensor Modules(CSM), are available for ensuringstable measurement conditions,thus enabling continuous onlineanalysis. The CSM 2000 andCSM 1000 models differ by virtueof the sensors used.The CSM is a standalone unitfeaturing a motor-pump assemblyand a contamination sensor.This enables the fluid to besuctioned out of lines andnon-pressurized tanks andconveyed through the sensorfor measurement.

The module also possessesa patented air suppression feature.This causes air present in the oil tobe dissolved by applying pressureand thus not counted as particlesin the optical contamination sensor.A moisture sensor, the AS 1000,or an oil level sensor,the HYDACLab®, can beintegrated in the oil stream.The HYDACLab® isa multi sensor for

temperaturemoistureviscosity changespermittivity alterations

The following prerequisites applyto the use of the CSM:

The following prerequisites applyin order to enable simpleintegration in the test rig, the CSMis used to suction oil in the vicinityof the return-flow line and conveyit through the particle counter.The CSM 1000 is used forstandard hydraulic applications.The CSM 2000 – combined witha supplementary CM-FS flowmeter– is available for difficult-to-countfluids (gear lubrication fluids,oil mixtures, grease concentratesand assembly lubricants).

The CSM contains a 400 µmprotective mesh (CM-S).

Fig. 14CSM 1000

Fig. 15CSM 2000

Fig. 16CSM 1000 integrated in test rig

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2.4Continuous OnlineMeasurement in Hydraulicand Lubrication Systems forCondition Monitoring

The series 2000 and 1000Contamination Sensors (CS)are available for continuous onlinemeasurement in hydraulic andlubrication systems, the sensorsbeing integrated permanentlyin the system. To this end, the flowrate has to be precision-adjustedin the respective measurementrange via the sensor.The Contamination Sensor is anorifice (hydraulically speaking).

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In contrast to the fluid service unitFCU, the flow rate is notsubsequently manually readjustedin the permanently integratedContamination Sensors.The limited flow range correlateswith a restricted working rangewith regard to pressure andviscosity. The following graphshows the difference in hydraulicworking range between theFCU and CS 1000.

Fig. 17Working Ranges of theCS 1000 and FCU 2000

Various ConditioningModules (CM)are available for regulating the flowrate within the permissible range.The ConditioningModules enablethe working range of the CS 1000and CS 2000 to be adaptedto the hydraulic conditions.These units are presented ina number of typical installationexamples.

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2.4.1Typical InstallationExamples

2.4.1.1Filter-Cooler /Heater Circuit

In a hydraulic circuit featuringa filter and cooler / heater unit,the CS can be integrated inthe bypass.

Industries / applications:Plastic injection molding machinery (OEM and MRO)Automotive / hydraulic presses (OEM and MRO)Steel manufacturing / paper manufacturing / power generation

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2.4.1.2Pressure Circuit

Integration is done via a pressure-compensatedflow control valve for medium pressure applicationsand when good oil cleanliness ratings are present.In high-pressure applications it is recommended thata filter be used for protecting the flow control valve.

2.4.1.3Leakage Oil Flow Monitoring

In hydraulic circuits in which large, costly pumpsare used it is important that the wear and tear posedto these pumps is measured. The optimal locationfor performing contamination measurement is theleakage oil line as particle concentrations buildup here the fastest.

Industries / applications:Plastic injection moulding machinery (OEM)Mobile / agricultural machinery, forestry equipment,stackers and lifting trucks, conveying equipment,mining machinery, construction machinery (OEM)

Industries / applications:Large-scale systems (OEM and MRO)

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2.4.1.4Lubrication Oil Monitoring

The ContaminationSensor Module CSM is availablefor lubrication oil monitoring. The pump providesa sufficient flow rate through the sensor.The CSM possesses a patented air suppressionfeature. Hydraulic pressure prechargingof 25 bar in the sensor is recommended forlubricating oil.

Industries / applications:Wind power generation systems and gear unitsSteel manufacturing / paper manufacturing /power generation

2.4.2General InstallationRecommendations

Certain criteria should be heededwhen installing the sensors so thatinterference is reduced.

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2.4.3Conditioning Modules

For information on the Conditioning Modules,please refer to the brochure “Fluid Monitoring -Technical Information” (when ordering, please statelanguage required: German or English).

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2.5Laboratory Equipment

Sample analysis in the laboratory:the BottleSampling Unit (BSU), AutomatedLaboratory Particle Counter (ALPC) and FCU 2000have been specifically developed for this purpose.Overview of the key features of these units:

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Imprint

3rd Edition, April 2008

Industriegebiet66280 Sulzbach / SaarGermany

Phone:+49 6897 509-01

Fax:+49 6897 509-846

Internet: www.hydac.comE-Mail: filtersysteme@hydac.com

HYDAC Filtertechnik GmbHService Technology / Filter Systems