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    FLAMMABLE

    Millipore Particle Monitoring Guide

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    INTRODUCTION ..................................................................................... 1Sampling Guidelines......................................................................................................2

    Fluid Sample Collection ..............................................................................................2Surface Sample Collection ..........................................................................................2

    Analytical Methods for Determination of Particle Contamination......................................2

    Sampling Apparatus......................................................................................................3Filters........................................................................................................................3Filter Holders.............................................................................................................4

    AIR AND GAS MONITORING.................................................................. 5

    Applications..................................................................................................................5Clean Rooms .............................................................................................................5Industrial Hygiene......................................................................................................5Gas Lines ..................................................................................................................5

    Regulations ...................................................................................................................6

    Sampling and Filtration .................................................................................................6

    Air Monitoring Equipment..............................................................................................6Filter Holders.............................................................................................................6Flow-Limiting Orifices.................................................................................................7Filters........................................................................................................................7

    Clean Room and General Air Sampling ..........................................................................7Air Sample Collection.................................................................................................7

    SamplingPoints .................................................................................................................. 8Sampling Time ........................................ ............................................ ................................ 8

    Air Sampling Procedure .............................................................................................937 mm Monitoring Cassette Method ..................................................................................... 947 mm Stainless Steel Monitor Method.................................................................................. 9

    Table of Contents

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    Personal Sampling for Industrial Hygiene .................................................................... 10Sampling Point........................................................................................................ 10Cassette Use ........................................................................................................... 10Personal Sampling Procedure................................................................................... 11

    25 mm Cassettes............................................................................................................... 11

    Gas Lines ................................................................................................................... 12

    Sampling Times....................................................................................................... 12Clean Room Garments ................................................................................................ 13

    Sampling Procedure................................................................................................ 13Counting ................................................................................................................ 13

    LIQUIDS AND COMPONENT MONITORING ...........................................15Applications ............................................................................................................... 15

    Sample Collection and Filtration Methods..................................................................... 16Equipment .............................................................................................................. 16

    Sampling Bottles................................................................................................................ 16Filter Holders .................................................................................................................... 16Sampling Kits.................................................................................................................... 16

    On-Line Sample Collection and Filtration .......................................................................17Quick-Release Valve Installation............................................................................... 17Monitoring Cassette Sampling Procedure .................................................................. 18

    Batch Sample Collection and Filtration ......................................................................... 20Container Cleaning................................................................................................. 20Sampling Valves ..................................................................................................... 21Sample Collection ................................................................................................... 21Filtration Equipment Preparation............................................................................... 22Filtration Procedure ................................................................................................. 22Patch Test Kit Collection and Filtration....................................................................... 24

    Equipment Preparation ......................................... ............................................. ................ 24Sample Collection ............................................................................................................. 24Filtration Procedure ........................................................................................................... 25

    Components Monitoring.............................................................................................. 25Tubing and Hoses Sampling..................................................................................... 26Small Valves and Manifolds Sampling ...................................................................... 26Large Valves and Fittings Sampling .......................................................................... 26

    ANALYSIS ............................................................................................ 27Optical Microscope Particle Counting........................................................................... 27

    Filter Clearing......................................................................................................... 28Acetone/Triacetin Method..................................... ............................................... .............. 28Dimethylphthalate and Diethyloxylate Method ..................................................................... 29Microscope Immersion Oil Method ..................................................................................... 29

    Equipment .............................................................................................................. 29Measuring Eyepiece (Reticle) Calibration............................................................................. 30

    Particle Counting..................................................................................................... 31Scanning Electron Microscope (SEM) Particle Counting.................................................. 32

    Sample Preparation................................................................................................. 33Calibration ............................................................................................................. 33Particle Size and Counting....................................................................................... 33

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    iii

    Particle Gravimetric Analysis....................................................................................... 34Filter Selection ........................................................................................................ 34Sample Preparation................................................................................................. 35Results Weighing and Calculation ............................................................................ 36

    Matched-Weight Filters or Matched-Weight Cassettes .......................................................... 36Control Filter Method......................................................................................................... 36Inorganic (Noncombustible) Fraction................................................................................... 36

    Particle Identification .................................................................................................. 37Optical Microscopy................................................................................................. 37Other Methods........................................................................................................ 37

    Colorimetric Patch Method .......................................................................................... 38

    TYPICAL CONTAMINATION LEVELS........................................................ 39Hydraulic Fluids.......................................................................................................... 39

    NAS 1638, Jan. 1964Aerospace Industries Association of America, Inc. ...................... 40

    Aircraft Fuels .............................................................................................................. 40

    Rocket Propulsion & Service Fuels................................................................................ 40

    Ambient Air................................................................................................................ 41

    Clean Room Garments ................................................................................................ 41

    FILTER SELECTION ................................................................................. 43MF-Millipore (Mixed Cellulose Esters) Membrane Filters ................................................ 43

    Chemical Compatibility............................................................................................ 43Thermal Stability ..................................................................................................... 43Matched Weight Membranes................................................................................... 43

    Isopore Track-Etched (PC) Membrane Filters.............................................................. 44Surface Retention Characteristics.............................................................................. 44Track-Etched Membranes for Particle Analysis........................................................... 44

    Fluoropore and Mitex (PTFE) Membrane Filters............................................................. 44Chemical Compatibility............................................................................................ 44

    Thermal Stability ..................................................................................................... 44Silver Membrane Filters (Pure Silver)............................................................................ 44

    Availability............................................................................................................. 44

    Durapore(Polyvinylidene Fluoride) Membrane Filters................................................. 45Broad Chemical Compatibilities................................................................................ 45Availability............................................................................................................. 45

    Qualitative/Quantitative Wet-Strengthened Ashless Depth Filters.................................. 45

    Glass Fiber Filters without Binders ............................................................................... 45

    PVC Membrane Filters................................................................................................. 45

    Prefilters..................................................................................................................... 45Type AP40 Microfiber Glass Discs (for Analysis Only) without Binder Resin ................. 45

    Type AP10 Absorbent Pads ..................................................................................... 45Type AP30 Thick Support Pads................................................................................. 45

    Air and Fluid Monitoring Applications Guide................................................................ 46

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    APPENDIX ............................................................................................ 61Aerosol Analysis Cassettes, 25 mm ............................................................................. 61

    Aerosol Analysis ..................................................................................................... 62Ordering Information .............................................................................................. 62

    Fluid Contamination Analysis Cassettes, 37 mm........................................................... 63Contamination Analysis........................................................................................... 63

    Matched-Weight..................................................................................................... 63Ordering Information .............................................................................................. 63

    Fluid Sampling Kit ...................................................................................................... 64Applications ........................................................................................................... 64Specifications.......................................................................................................... 64Ordering Information .............................................................................................. 64

    Compact Fluid Sampling Kit ........................................................................................ 65

    Patch Test Kit.............................................................................................................. 66Applications ........................................................................................................... 66Specifications.......................................................................................................... 66Ordering Information .............................................................................................. 66

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    I

    article contamination is of particular concern in processing, manufacturing, packaging,

    transporting and operating systems with electronic and mechanical components and their

    associated fluids. The levels of particle contamination that are tolerated in these systems

    are extremely low and must be monitored. Particle volume and size factor into how well

    and how long a system will operate. Large particles cause a system to breakdown faster

    than small particles, but a large number of small particles can also cause premature system

    failure. Fluids and fluid streams that are routinely monitored include fuels, gases, hydraulic

    oils, lubricants, water, chemicals, precision component rinses, cleaning tanks, boilers, and

    pharmaceutical products. Routine analysis of clean room environments, building abate-

    ments, and worker safety in an industrial environment are all reliant on methodology forparticle analysis of air.

    Millipore designed this manual to help you monitor air and fluid in the workplace. We

    manufacture a variety of products for you to use as analytical tools for collecting, identify-

    ing, and measuring particles in the air during a manufacturing process or for determining

    worker exposure by personal air monitoring. Prolonged workplace and environmental

    exposure to airborne contaminants has been linked to a number of occupational diseases.

    National and international regulatory agencies have established standard methods of anal-

    ysis and set threshold limits for a large number of liquid and airborne contaminants.

    Millipore has specialized in providing products for occupational and environmental moni-

    toring for over 30 years and continues to meet todays demanding standards.

    This manual references recommended NIOSH, OSHA and ASTM methods of quantitatively

    measuring contamination using Millipore filters. These methods incorporate the use of fil-

    ter collection of particles for analysis by a variety of methods, including AA, Spectrophoto-

    metric, ICP and HPLC-UV analysis. Nearly every particle-monitoring situation poses special

    problems and requirements that can not be foreseen or covered adequately in a single

    publication. This manual, therefore, provides essential elements of procedures and tech-

    niques. Experienced Quality Control Engineers can use this manual as a point of departure

    in developing their own standard procedures.

    In order to determine particle contamination in liquids, you can use sampling methods

    including direct, batch and on-line sample collection.

    Introduction

    P

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    SAMPLING GUIDELINESIn order to sample for particle contamination in

    any system (gases, liquids, or component sur-

    faces), you must collect particles on a filter. You

    should reliably adhere to the same sampling pro-

    cedure to ensure valid, reproducible results. Sam-

    pling variables can be categorized as follows:

    Sampling Contamination:All sampling equip-

    ment, collection containers, analytical appara-

    tus and filters must be clean to use subsequent

    measurements as a valid index of the system

    you plan to test.

    Sample Adequacy:The number of samples,

    sample volume, and sampling time are depen-

    dent on the level of system contamination and

    the type of measurement you are performing.

    You must sample sufficient material to clearly

    measure critical levels of contamination. As

    an example, 100 mL would be representativeof a high performance hydraulic system by

    microscopic particle counting; 1 to 5 gallons

    (4-20 liters) would be a representative sample

    for gravimetric analysis of a turbine fuel sys-

    tem.

    Air monitoring standards require a minimum

    of 10 cubic feet (280 liters) for measuring the

    air in a clean room environment down to Class

    10,000. Proportionately greater volumes are

    needed for Class 10, 100 and 1000 clean

    rooms.

    Fluid Sample CollectionThe samples must represent the entire fluid system

    when the system is operating normally in order to

    be meaningful and reproducible. You should take

    samples of viscous fluids from areas of high turbu-

    lence where particles are mixed throughout the

    fluid cross section. When you are sampling a static

    system and the system contents cannot be thor-

    oughly mixed, take a multilevel sample.

    Surface Sample CollectionYou cannot remove all contaminating particles

    from a component surface by rinsing. It is impor-

    tant to use the same sampling (flushing) procedure

    every time you analyze the samples. The analytical

    results from such sampling do not indicate the

    total extent of surface contamination, but yieldmeaningful and reproducible data.

    ANALYTICAL METHODS FORDETERMINATION OFPARTICLE CONTAMINATIONThere are many test procedures for particle con-

    tamination. The Air and Fluid Applications Guide

    in Chapter VI briefly describes NIOSH, OSHA and

    ASTM methods using filtration for sample collec-

    tion, monitoring and preparation of particle and

    chemical contaminants. These procedures havebeen specifically designed for monitoring contami-

    nants in the workplace and are dedicated to

    worker safety. The following analytical methods

    are described in detail with step by step proce-

    dures:

    Particle Counting:A quantitative method for

    determining particle contamination by count-

    ing the particles on a filter through a micro-

    scope.

    Gravimetric:A quantitative method for deter-

    mining contamination level by weight.

    Patch Testing:The Patch Test is a colorimetric,

    semi-quantitative method that allows for visualevaluation of contamination levels based on

    the characteristic color of the particle matter.

    Spectroscopy, HPLC-UV and x-ray diffraction are

    methods that will not be described in this text but

    may be applicable.

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    Introduction 3

    SAMPLING APPARATUSMost sampling techniques require filters, filter

    holders and a pump with vacuum or positive pres-

    sure.

    FiltersYou can use different types of filters for particle

    monitoring: screen (also known as membrane) and

    depth (Figures 1 and 2). The screen filter is a uni-

    form, continuous mesh of polymeric material with

    precisely defined pore size. These filters are avail-

    able in nitrocellulose, nylon, PTFE or PVC. The

    material type you use depends on its compatibility

    with the fluid you need to sample. Screen filters

    consist of a screen configuration with defined size

    openings. Most screen filters are hydrophobic and

    you can easily rinse them without retaining any

    liquid droplets that can interfere with the analysis.

    Depth filters have a matrix of randomly-orientedfibers pressed, wound, or bonded together into a

    random matrix of flow channels. Unlike screen fil-

    ters, depth filters have a nominal pore size, caus-

    ing the filter to retain a range of particles during

    initial use. Due to the random orientation of fibers,

    depth filters do become saturated and eventually

    the pores become larger with use. Therefore, Milli-

    pore recommends you use them for prefiltration or

    as a support pad in many of the monitoring proce-

    dures. Factors such as the size of the particles,

    fluid/filter compatibility and the filtration method

    determine which filter you should use. Refer to the

    Air and Fluid Applications Guide in Chapter VIfor the proper monitoring method and the appro-

    priate filters. You can also refer to the compatibil-

    ity guide in the Millipore laboratory products

    catalogue.

    Figure 1. Schematic cross section, screen-type

    (membrane) filter. Particles retained on surface.

    Figure 2. Schematic cross section, depth-type filter.

    Random entrapment of particles.

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    Filter HoldersIn general, you use Millipore particle-monitoring

    filters as discs with an underlying support to pro-

    tect the filter against pressure differentials achieved

    during filtration. You can install or clamp filter

    discs in the filter holders between parallel sealing

    surfaces or gaskets. There are two types of Milli-pore filter holders for use in contamination analy-

    sis:

    Reusable Filter Holders: Millipore provides a

    variety of reusable filter holders constructed of

    stainless steel, glass or polypropylene for both

    liquid and atmospheric sampling. We recom-

    mend these holders for many procedures per-

    formed in a laboratory benchtop environment.

    Disposable Filter Holders: Millipore also pro-

    vides a variety of disposable filter holders

    depending on the specific method. Air moni-

    toring cassettes are available in 25 and 37 mm

    diameters in a two- or three-piece configura-tion. The 37 mm cassettes are constructed of

    transparent polystyrene. The 25 mm are con-

    structed of all-conductive carbon filled

    polypropylene. Both cassette configurations

    are available preloaded or empty. A wide

    range of filters in different pore sizes are avail-

    able for these cassettes to meet both unique

    and standard sampling requirements. All cas-

    settes are assembled in a clean room environ-

    ment to minimize background particle

    contamination. For preloaded cassettes, the

    average background particle count has been

    determined and is marked on the outside ofeach package. Cassettes are also available with

    matched weight membranes to eliminate the

    need for preweighing test filters for gravimet-

    ric analysis.

    The procedures described in this manual may

    involve hazardous materials, operations, and

    equipment. If you plan to follow these procedures,

    you are responsible for establishing appropriate

    safety and health practices and determining the

    applicability of regulatory limitations before you

    begin. For example, if you use Millipores Hydrosol

    stainless holder (XX20 047 20) for flammable liq-

    uids, you must ground it according to the direc-

    tions provided with the product. The Hydrosol

    unit is fitted with a grounding screw and comes

    complete with a grounding lead fitted with an alli-

    gator clip.

    WARNING: If you are filtering petroleumether or other flammable sol-

    vents, you must ensure that the

    Hydrosol unit is grounded to pre-

    vent arcing from static electricity

    created during filtration.

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    II

    APPLICATIONSIt is important to conduct air and gas monitoring in many of todays workplaces, wheresuch techniques are necessary in clean rooms, for industrial hygiene, and in gas lines.

    Clean RoomsTodays processes involving gyroscopic, mechanical, servo, and electronic systems areextremely sensitive to dust particles. Particle contamination can have a damaging effect onhighly sensitive products. This has created a demand for monitoring manufacturing andassembly areas, test laboratories, and clean rooms for particle contamination. Millipore fil-ters have been recommended for clean room monitoring for many years.

    Industrial HygieneIndustrial hygienists perform air monitoring for the analysis of hazardous particles, asbes-tos fibers, chemical vapors, and dust by area sampling and personal sampling.Millipore recommends a two or three piece 37 mm monitoring cassette for area samplingand a 25 mm monitoring cassette with or without a cowl for personal sampling. (See Airand Fluid Applications Guide in Chapter VI.) Both configurations are available from Milli-pore, in addition to the filters specified in the method.

    Gas LinesYou monitor gas lines through an in-line filter holder. The in-line filter cleans the gasstream and, at regular intervals, you can remove the filter from the holder and analyze it

    for contamination.

    Air and Gas Monitoring

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    REGULATIONSIn the U.S., the EPA (Environmental ProtectionAgency) regulates environmental exposure whileOSHA (Occupational Safety and Health Adminis-tration) regulates exposure in the workplace.NIOSH (National Institute of Occupational Safety

    and Health) develops the test methods in associa-tion with OSHA, the CDC (Center for Disease Con-trol and Prevention) and the U.S. Department ofHealth and Human Services. When the EPA adoptsa NIOSH standard method, it is referenced in theU.S. Federal Register. The Air and Fluid Applica-tions Guide in Chapter VI references NIOSH,OSHA and ASTM methods. These organizationsfocus on the workplace and worker safety in devel-oping their procedures. OSHA regulates exposureof over 100 air and fluid contaminants that can bemonitored and sampled by membrane filtration.

    In Europe, European Community Directives arepublished in the Official Journal of the EuropeanCommunities. For asbestos, the Asbestos Interna-tional Association has published a comprehensivemethod for determination of asbestos in environ-mental and occupational settings. This method rec-ommends monitoring asbestos through a Millipore25 mm all conductive carbon-filled polypropylenecassette with cowl.

    SAMPLING AND FILTRATIONIn air monitoring and sampling procedures, air is

    drawn by vacuum through a 37 mm two- or three-piece polystyrene cassette preloaded with thespecified filter and support. In order to calculatethe particles per unit volume of air, use the follow-ing equation:

    where L = liters of air, t = unit of time,T = total sampling time, and V = total volumein liters.

    Then measure the number of particles on the filter(P) by weight or direct counting, and complete thefollowing equation:

    While there are a variety of different samplingmethods, the two basic air sampling proceduresarepersonal samplingto determine individualworker safety and area sampling to determine thesafety of the entire work environment.

    For personal sampling, you place the holderwithin the workers breathing zone (cassette open-ing facing down) and connect through flexible vac-uum tubing to a flow-controlled battery-operatedpump attached to the workers belt. Sampling istypically carried out long enough to represent afull work shift (minimum of 1/2 the full shift).Flow rate is usually 1 to 4 liters per minute,adjusted according to expected fiber and particleconcentrations.

    For area sampling, you mount the holder verticallyon a stand and direct toward a representative airspace. You connect the holder to an appropriatevacuum pump through flexible vacuum tubing,and adjust the flow rate. If you use a Milliporethreaded hose adapter (XX62 000 04), you can reg-ulate the flow by inserting the appropriate flow-limiting orifice. Millipore supplies orifices in amatched set to monitor a range of flow rates.

    AIR MONITORING EQUIPMENTAir monitoring equipment consists of filter hold-ers, flow-limiting orifices, and filters. See the fol-lowing sections for details.

    Filter HoldersMillipore 47 mm stainless steel filter holders aredesigned for sampling large volumes of particles inair, such as those found in a large dust environ-ment where protective clothing would be worn.These filter holders are available in an open con-

    figuration for maximum unimpeded flow in openatmosphere sampling, or a closed system with aninlet dispersion chamber for optimum particle dis-tribution on the filter. In critical situations, the fil-ter holder must be pre-cleaned and the filter pre-counted for background particles.

    A 37 mm monitoring cassette is best for monitor-ing low particle volume in a clean environment.These cassettes have been pre-cleaned duringassembly with the average surface particle back-ground count supplied with each lot.

    To eliminate the need for pre-weighing test filters,

    matched weight cassettes are also available forgravimetric analysis. Each of these cassettes con-tains two superimposed filters matched in weightto within 0.1 mg. These filters are available in 47and 37 mm disc sizes.

    T = VL

    t

    = particles per liter of airP

    V

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    Air and Gas Monitoring 7

    Flow-Limiting OrificesThe flow-limiting orifice is a simple way to controlflow rate. Insert the specific orifice into thethreaded outlet (vacuum-connected) end of eithera Millipore 47 mm filter holder (stainless steel) ora Millipore aerosol adapter (stainless steel) when

    using a 37 mm contamination cassette. When youapply the required level of vacuum, air flowsthrough the filter and orifice at a constant rate.The amount of vacuum required to maintain thecorrect flow rate for each orifice available is listedin Figure 3. The applied vacuum must be equal toor greater than the specified level. The orifice isavailable in a two liter/min configuration for a con-stant flow rate, or a set of inlet pressures to moni-tor a range of flow rates.

    FiltersThe filters required for each air monitoring appli-cation depends on the contaminant. Pore size, fil-ter compatibility and analytical method all play apart in filter choice. All Millipore filters displayhigh particle collection efficiency over a broadrange of particle sizes. The most recommended fil-ter is a 0.8 m cellulosic, (AA), which has beenshown to retain essentially 100% of all airborneparticles (>99.99%). The binderless glass fiber(depth) filter has been shown to have a retentionefficiency of >99% for a 0.3 m aerosol of dio-ctylphthalate (DOP). Millipore also offers PVC,PTFE, nylon, and silver filters to fit the specificapplication. For published NIOSH, OSHA and

    ASTM procedures, refer to the Air and FluidApplications Guide in Chapter VI to find the rec-ommended filter.

    CLEAN ROOM ANDGENERAL AIR SAMPLINGThe following section outlines air sampling tech-niques including a general discussion of collectingair samples and a description of specific proce-

    dures for air sampling using Millipore filters, hold-ers and cassettes.

    Air Sample CollectionAirborne particle contamination can vary signifi-cantly depending on the operations being carriedout. To minimize sample variability, you shouldsample during an entire shift, ~8 hours. The finalresult is determined by the average level of expo-sure. Alternatively, your sampling times can beshort, sometimes only a few minutes, to deliber-ately measure how high the exposure is duringspecific dust-generating operations.

    Orifice FlowRate Minimum Required Vacuum

    (L/min.) mm Hg In Hg PSIG

    1 300 12 6

    2 300 12 6

    3 300 12 6

    4.9 400 16 8

    10 500 20 10

    14 550 22 11

    Figure 3. Vacuum required for function of flow-

    limiting orifices.

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    Sampling PointsYou should take samples as close as possible tothe point where the critical operations are carriedout. The vacuum pump should be located awayfrom the sampling area, preferably outside thecontrolled environmental enclosure itself. In gen-

    eral practice, you should place the filter surfacevertically, facing outward into the room towardsthe highest traffic area.

    For air sampling in clean rooms and other dust-controlled areas, the ASTM recommendations forsampling points are indicated in Figure 4. Sampleat 1 and 2 in areas less than 150 sq. ft. Use points1, 2, 3, 4 and 5 in larger areas to 1000 sq. ft. Theparticle count is determined as the average of allpoints. For glove boxes and other small enclo-sures, sample at point 1.

    Sampling TimeThe number of air samples required for a givenarea is based on the floor area, air flow interrup-tions, and the room volume.

    Depending on the method, samples must be largeor small enough to be measured and representa-

    tive of the area being evaluated.The following chart describes the recommendedsample size, flow rate and time required for moni-toring the specified areas and performing a micro-scopic count.

    *Larger sample volumes are required for Class

    1000, 100 and 10 clean rooms.

    1

    54

    32

    21

    Figure 4. Clean room sampling plan as recom-

    mended by ASTM.

    DescriptionSample(cu. ft.)

    Flow Rate(1pm)

    Time(min.)

    Clean Rooms(down toClass 10,000)*

    10 10 28

    Country Air 5 10 14

    City Air 1 1 28

    Factory Air 0.5 0.5 28

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    Air and Gas Monitoring 9

    Air Sampling Procedures

    37 mm Monitoring Cassette Method1. Thread the flow-limiting orifice (if using one

    to control flow rate) into the barbed end of theaerosol adapter (Figure 5) and attach it to the

    vacuum hose.2. Remove bottom (red) plug from three-piece

    transparent cassette and insert the luer con-nector end of the aerosol adapter (Figure 6).

    3. Remove top cover of cassette. Do not removeyellow plug.

    4. Apply vacuum for specified time to take sam-ple (Figure 7).

    5. After sampling, replace cassette cover beforeremoving from stand, to protect filter.

    6. Send to lab for analysis.

    47 mm Stainless Steel Monitor Method1. Clean monitor thoroughly to reduce extrane-ous particles.

    2. Perform a microscopic particle count or weighthe filter to determine baseline particle con-tent. (Store filter in PetriSlide until ready foruse.)

    3. Screw limiting orifice into hose adapter andattach vacuum hose.

    4. Place test filter, grid-side up, on supportscreen in base.

    5. Lock filter into place using blue anodizedlocking ring.

    6. Apply vacuum for specified time to take sam-ple.

    7. Open filter holder, remove filter and return toPetriSlide for subsequent evaluation. (SeeChapter IV for analysis techniques.)

    Figure 5. Placing flow-limiting orifice into outlet of

    aerosol adapter.

    Figure 6. Inserting luer end of aerosol adapter into

    cassette outlet.

    Figure 7. Sampling air using 37 mm cassette con-

    nected to vacuum pump.

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    PERSONAL SAMPLING FORINDUSTRIAL HYGIENEThis section describes the process of personalsampling for industrial hygiene including deter-mining a sampling point, choosing the correct cas-

    sette, and using each type of cassette.

    Sampling PointPlace the cassette, open filter surface facing down,in the workers breathing zone so that the air sam-pled will be representative of what the workeractually inhales.

    Cassette UseYou may use the cassette with a closed or openface (depending on the reference method). Anopen-faced cassette (inlet cover removed) allows

    uniform particle or fiber distribution across the fil-ter. With a closed-face cassette (inlet cover on), theair enters through the single hole at the center ofthe inlet cover. This technique is more commonlyused for nuclear power plant applications.

    The 37 mm monitoring cassette is available with acenter ring, when required. A two-piece configura-tion is commonly used for personal air sampling.The cassette can be installed in a Cyclone samplerfor gravimetric analysis of large dust particles,such as coal (Figure 8).

    The Millipore 25 mm monitoring cassette is avail-able either with a center ring or with a 50 mm con-

    ductive extension cowl that helps protect themembrane from inadvertent contamination, mini-mizes static electricity and helps ensure uniformparticle or fiber distribution.

    Figure 8. 37 mm monitoring cassette installed in a

    Cyclone sampler.

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    Air and Gas Monitoring 11

    Personal Sampling Procedure

    25 mm Monitoring Cassette Method1. Attach hose to adapter (after removing plug

    and stand).

    2. Attach hose to pump (Figure 9). If pump has

    been recently calibrated, go to step 4.3. Preferably once a day, calibrate the pump.

    Connect a flow meter to the cassette inlet byremoving the red plug in the cassette coverand inserting a connector attached to tubing(Figure 10). Alternatively, remove the cassettecover and place the cassette inlet over the flowmeter outlet. Adjust the pump flow controlscrew (for personal sampling, 2 L/min is usu-ally recommended).

    4. Connect the cassette to clothing in the breath-ing zone (Figure 11).

    5. Note the time and start the pump to collectsample.

    6. At the end of the sampling period (commonly8 hours for personal sampling), replace theinlet cover to protect filter and insert outletplug.

    7. Send to lab for analysis.

    igure 9.25 mm aerosol cassette connected to per-

    sonal sampling pump. Clothing clip fixed to tubing.

    igure 10.Calibrating personal sampling pump using0-4 L/min flow meter with cassette connected in-line.

    Figure 11. Cassette attached to worker's clothing in

    breathing zone. Personal sampling pump clipped to

    trouser belt.

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    GAS LINESThe Gas Line Filter Holder is best for in-line moni-toring of gases (Figure 12). The advantage of thisholder is that you can remove the filter for furtheranalysis without removing the holder from the line(Figure 13). For details on other filter holders, see

    the Millipore laboratory products catalogue.

    Sampling TimesGas lines should be checked monthly or quarterly,depending on usage. You should also check gaslines during each line transfer to prevent crosscontamination. When you are troubleshooting aproblem, periods as short as a few hours may beadequate. At the other extreme, you may changeand analyze filters every three months on cleangas streams. A gas line filter prevents particle con-tamination in a clean outlet stream, which can be

    critical for highly sensitive instruments such as gaschromatography or atomic absorption.Figure 12.In-line sampling from compressed gasbottle with the 25 mm gas line filter holder.

    Figure 13. Removal of filter for analysis from gas

    line filter holder.

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    Air and Gas Monitoring 13

    CLEAN ROOM GARMENTSThe procedure for sampling clean room garmentsrequires that you draw filtered air through fivedesignated 0.01 sq. ft. areas of a single thicknessof the garment fabric at a rate of 14 liters perminute (L/min)for one minute per area. Loose

    particulate contaminants on or in the garmentimpinge on the surface of a Millipore filter. Exam-ine the filter microscopically to determine thenumber of particles (>5 m) removed from thegarment.

    Sampling Procedure1. Screw the 14 L/min limiting orifice into the

    filter holder outlet and connect the holderto a vacuum source (of at least 55 cm Hg.at 14 L/min) using a hose.

    2. Carefully place a Type AA black filter, grid-

    side up, on the support screen in the filterholder base using clean forceps. Similarlyplace a Type SM white filter on top of the filter(Figure 14). Lock in place with the blue lock-ing ring. When ready to sample, see step 3.

    3. Place the outer surface of the test garmentover the tapered (male) body of the holder.Secure the prefilter adapter assembly over thetest portion of the fabric (Figure 15).

    4. Apply vacuum and sample with the same filterfor a period of one minute for each of the fivetest areas. Be sure to turn vacuum off aftereach test.

    5. Open the filter holder, remove the sample fil-ter, and place it on a PetriSlide for subsequentcounting. (See Chapter IV.)

    CountingFor garment monitoring, it is customary to countand tabulate particles in two categories only:

    1. All particles with the major dimension greaterthan 5 m.

    2. Fibers (longer than 100 m with a length-to-width ratio exceeding 10 to 1).

    Each garment sampling area is 0.01 sq. ft. as

    defined by the clean room monitoring filter holder.Five sampling areas, therefore, provide a garmentsample of 0.05 sq. ft. Multiply the total filter countby 20, for example, for 5 sample areas and reportresults in terms of particles per sq. ft. and fibersper sq. ft. of garment.

    Figure 14. Filter is centered on base of garment

    monitoring holder. The prefilter is placed onto the

    filter

    Figure 15. Test garment secured between prefilter

    adapter section (right), and the filter holder (left).

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    III

    APPLICATIONSProcess water may contain particles present in the feed water or in-line contaminantsresulting from corrosion and mechanical wear. The cleaning process for manufacturedcomponents contributes to particle contamination as well. Particles such as metal filings,joint compound and lubricating residues begin to accumulate with usage and eventuallybecome damaging to the product. During chemical and electronic manufacturing pro-cesses, particles from feed water or cleaning solvents can contaminate or destroy the prod-uct. The automotive and semiconductor industries have implemented quality controlprocedures for fluid particle monitoring and must be certified by many of their componentsuppliers. Particle contamination monitoring procedures are also in place for boiler feed-

    water and reactor cooling waters, which must be monitored for particle contaminationprior to startup and at regularly scheduled intervals during operation.

    Aviation fuels pick up particle contaminants all along the route from refinery to aircraft.These particles commonly consist of fine sand, metal chips, metallic oxides, gums and res-ins the products of corrosion, scaling, vibration and abrasion.

    Hydraulic fluids pick up contamination as a result of oxidation and polymerization of thefluid itself during operation at high pressures and temperatures. These contaminants con-sist of organic gums, varnishes and acids that combine with other particles to form asludge. Over time, additional particle contamination can occur as a result of erosion andmechanical wear.

    Liquids andComponent Monitoring

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    SAMPLE COLLECTIONAND FILTRATION METHODSWhen using batch (indirect) sampling, collect theliquid in a container. Next use the Millipore PatchTest Kit to filter and analyze it on site, or send it to

    a laboratory for subsequent filtration and analysis.When sampling by this method, you must makesure that both the collection containers and thelaboratory filter holders are clean to avoidunwanted contamination. This technique requiresspecific equipment preparation and laboratorytesting. Therefore, Millipore does not recommendit for critical applications such as monitoring fuels,component systems, process waters or boiler watersystems.

    The direct sampling method, where you filter yoursamples directly at the fluid inlet from a fuel orwater line, is a simpler and more reliable proce-

    dure. Direct sampling eliminates the possibility ofintroducing extraneous contamination from thesample containers. If the liquid is under pressurein excess of 10 psi, filter your samples directly atthe sampling point using a Millipore samplerdevice that contains a disposable two-piece filtercassette. The sampler/cassette assembly isplugged into a quick-release sampling valveinstalled at the outlet of the system or storagetank. The operating pressure (100 psi max.) forcesliquid through the assembly. The initial volume isdirected through the valve and bypass hose toflush the sampler. The sample volume passes

    through the filter cassette into a graduated con-tainer attached to the sampler base. After sam-pling, you may analyze the test filter on-site usinga colorimetric method (Patch Test) or send it to thelaboratory for more detailed analysis (e.g. particlecounting or gravimetric analysis).

    Gravimetric analysis consists of preweighing a fil-ter before use and then weighing it again after thesample has been filtered. The difference in thetwo weights determines the approximate particlecontent. Or, using another method of gravimetricanalysis, you pass the sample through two pre-weighed filters placed in the same holder. For con-

    venience, Millipore matched-weight membranesare available as disc pairs or in preloaded transpar-ent polystyrene cassettes. Each cassette containstwo superimposed filters matched in weight towithin 0.1 mg. As the sample passes through bothfilters, all the contaminants are retained on theupper test filter. The difference in the weights ofthe filters after drying is the weight of the contam-inant in the sample. Using matched weight pairs

    eliminates the need to preweigh the filters andrules out any extraneous contamination of the testfilter.

    EquipmentThis section outlines the equipment you will need

    to conduct liquids and component monitoring.

    Sampling BottlesFor field use, unbreakable plastic bottles clearlyhave an advantage over breakable glass bottles.When possible, bottles should be slightly largerthan the sample size and graduated on the outside.The Patch Test Kit for field use includes 120 mLtransparent PVC bottles.

    Filter HoldersFluid contamination filter cassettes are transparent,disposable filter holders that have been precleaned

    and preassembled. The cassettes are made ofimpact resistant polystyrene and have been specifi-cally manufactured for the filtration of fuels andhydraulic fluids. If you want to use them with anyother chemical, please call Millipore Technical Ser-vice or refer to the Millipore catalogue for productcompatibility. Each box of monitoring cassetteshas the average background particle count markedon each package. These 37 mm cassettes are avail-able empty or preloaded with Millipore filters andsupport pads.

    Millipore 25, 37, and 47 mm glass or stainless steel

    holders are used for vacuum filtering liquids in thelaboratory. When filtering flammable liquids, youmust use a stainless steel filter holder fitted withgrounding wires. Millipore fluid test kits, patchtest kits, and 47mm Hydrosol units all contain therequired grounding capability.

    WARNING: If you are filtering petroleumether or other flammable sol-vents, you must ensure that thestainless steel filter unit isgrounded to prevent arcing fromstatic electricity created duringfiltration.

    Sampling KitsMillipore has developed sampling kits specificallydesigned for monitoring aviation and hydraulic flu-ids. These kits are also used in monitoring storagetanks, coolant waters, and some solvent cleaningtanks. (Check the Millipore laboratory productscatalogue for compatibility information.)

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    Liquids and Component Monitoring 17

    ON-LINE SAMPLE COLLECTION

    AND FILTRATION

    If the liquid you plan to test is under pressure(between 10 and 100 psi), you can filter the sam-ples directly at the sampling point. To do this, use

    a Millipore Sampler Assembly and a clean dispos-able Fluid Contamination Cassette containing aMillipore filter. The Millipore Fluid Sampling Kits(ideal for this purpose) are portable, self-containedkits. The larger kit consists of a stainless steel sam-pler, connecting valves and everything needed forfrequent on-site sampling of liquids from pressur-ized systems. The smaller kit contains a compactaluminum filter holder with a stainless steel inletand outlet sampling core. Connecting valves andadditional equipment are sold separately. Usingeither of these kits eliminates the need for samplebottle cleaning and prevents cross contamination.

    Plug the sampler assembly, containing a cassette,into a stainless steel quick-release valve installedin the system line (Figure 16). The operating pres-sure (100 psi max.) forces liquid through theassembly. The initial volume is directed through abypass line to flush the valve and inlet hose. Thesample volume then passes through the filteringcassette and into a graduated container. Alterna-tively, you may transfer the fluid to a collectionvessel by means of a sampling tube.

    After sampling, either send the filter cassette to thelaboratory for analysis or evaluate it on site usingthe appropriate method. Refer to the Air and

    Fluid Applications Guide in Chapter VI for theproper monitoring method.

    Quick-Release Valve InstallationInstall the quick-release valve horizontally or ontop of a pipe where there is a high velocity flowduring flushing (Figure 16). Millipore recommendsa permanently installed quick release valve toavoid test variation and non-repeatability. Do notmount on the bottom of a pipe or tank where par-ticles can collect and will not all be rinsed awaywith the initial flush. One stainless steel quick-release valve is supplied with the Millipore fluidsampling kit. You can purchase additional valvesfor permanent installation at appropriate samplingpoints on systems throughout a given facility.Once permanent sampling valves have beeninstalled, an operator may tour the facility with thesampling kit, and filter samples directly using anew filter cassette at each point.

    Figure 16. Quick disconnect valve fitted in hori-

    zontal position into piping.

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    Quick-Release Valve Installation, continuedWhen installing the quick-release valves:

    Do not omit the dust plug supplied with eachvalve.

    Regulate the pressure immediately upstreamof the valve to a maximum of 100 psi if neces-sary.

    Monitoring Cassette Sampling ProcedureAfter installing the quick-release sample valves atthe appropriate points in the system, use the fol-lowing instructions for all analytical proceduresperformed using the Millipore Fluid Sampling Kit(Figure 17).

    1. Unscrew the sampler. Remove the protectiveplugs from the 2-piece filter cassette and savethe plugs for reuse (Figure 18). Install the cas-sette into the sampler with the filter facing up

    (Figure 19).

    NOTE:Millipore recommends MAWG 037 P0or MABG 037 P0 contamination moni-toring cassettes when performing directparticle analyses. We recommend theMAWP 037 PM matched weight cas-settes to eliminate the need to preweighthe filters when performing gravimet-ric analyses.

    2. Screw the sampler tightly together. Connectthe bypass hose from the three-way inlet valve

    to the hole in the side of the sampler (Figure20 and Figure 21).

    3. Screw the hose with the grounding wire intothe bottom of the sampling unit.

    4. Place the three-way inlet valve in the offposition and remove the dust caps from thequick-release sample valve and the inlet hosenipple. Retract the valve collar and insert thenipple firmly into the valve. Release the collarwhen the nipple is seated.

    5. Place the outlet of the hose into a container.

    Turn the three-way valve to the flush position

    and allow fluid to flow through the bypass tub-ing to flush contaminants from the sampling

    valve, the hose and the three-way valve (typi-

    cally about 100 mL for hydraulic fluids and one

    gallon [3.8 liters] for aircraft fuels).

    FLAMMABLE

    Figure 17. Sampling fuel from fuel truck with sam-

    ler using the grounded, remote sampling assembly.

    FilterMembrane

    Support Pad

    Bottom Half

    Plastic Monitor(Spoked Side)

    Plastic Plug

    Plastic Plug

    Top HalfPlastic Monitor

    Flow

    Figure 18. Two-piece preloaded monitoring cas-

    sette.

    Figure 19. Installing cassette (plugs removed) into

    body of sampler.

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    Liquids and Component Monitoring 19

    Monitoring Cassette Sampling Procedure,continued

    6. Hold the sampler upright, turn the valve to thetest position, and allow the desired samplequantity to flow through the cassette and intothe graduated container. Turn the three-way

    valve to off when the desired sample volumehas been collected.

    CAUTION: Some pumping systems (e.g. air-craft refuelers) develop a vacuumwhen stopped, which can cause

    backflow and rupture the filter inthe cassette. Always turn the sam-pler three-way valve to off beforepumping is discontinued.

    7. Retract the valve collar, remove the samplerand replace the dust caps.

    8. Disconnect the bypass hose from the side of

    the sampler, unscrew the sampler and removethe cassette (keep upright). Insert the syringevalve into the bottom of the cassette andpump it dry (Figure 22). Replace the cassetteprotective plugs, label it and return it to thelaboratory for analysis.

    For ASTM Method D2276: Place the filter in aPetriSlide and compare to ASTM standards booklet.

    When performing a colorimetric method:Remove filter from cassette and place in PetriSlide.Compare the color of the filter to the color stan-dard chart. Report color rating and volume tested.

    When using matched weight filters: Removeboth filters from the cassette and weigh each filter.The result is the weight of the bottom filter sub-tracted from the top.

    Figure 20. Connecting bypass hose from valve to

    bypass port of standard sampler.

    Figure 21. Connecting bypass hose from valve to

    bypass port of compact monitoring sampler.

    igure 22. Removing fuel from cassette using

    -way syringe unit.

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    BATCH SAMPLE COLLECTION

    AND FILTRATION

    As an alternative to in-line monitoring, you can col-lect liquid samples in containers and then analyzethem on site or send them to the laboratory for

    analysis. Cleanliness of the sample collection con-tainers is critical. Containers should be graduatedand preferably slightly larger than the sample size.

    Container CleaningBefore each use, clean the sample containers asfollows:

    1. Wash thoroughly with a standard laboratorycleaning solution. For critical work, check bot-tle cleanliness by filling and shaking with fil-tered solvent to dislodge particles. Then filterand analyze the solvent. If the standard clean-ing procedure is not effective, you may needto clean with dilute acid or a low surface ten-sion fluid (CFC-Free Contact Cleaner).

    2. Rinse each container twice with Milli-Q water.In this and in all other rinsing operations, asolvent filtering dispenser is especially conve-nient. By squeezing the bulb on the flask, asshown in Figure 23, a stream of solvent isforced from the flask, through a Millipore fil-ter, and out of the flexible dispenser tip.

    When you need to clean many containers atone time, the Filterjet solvent dispenser isespecially effective and convenient (Figure

    24). When connected to a pressurized solventtank, it provides a strong jet or spray of ultra-clean solvent in a continuous or trigger-con-trolled action.

    3. Rinse the sample containers with membranefiltered isopropyl alcohol to remove residualrinse water. A final rinse of membrane filteredCFC-Free Cleaning solvent (miscible with iso-propyl alcohol) is desirable if you are going touse the containers to collect oil or hydraulicfluid samples.

    4. Place a small square of Saranor Mylarplas-tic film, rinsed with membrane filtered solvent,over the mouth of the sample container beforereplacing the cap. This minimizes the dangerof contaminating the container with particlesfrom the screw cap. After closure, any residualrinse solvent evaporates in the empty samplecontainer and creates a slight vapor pressurein it. This pressure tends to blow particlesaway from the mouth when the container isopened for sampling.

    Figure 23. Flushing sample container with solvent

    filtering dispenser.

    Figure 24. Filterjet solvent dispenser connected to

    pressure vessel and vacuum/pressure pump.

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    Liquids and Component Monitoring 21

    Sampling ValvesThe best sampling valves, such as ball or plugvalves, provide a straight fluid path when open(Figure 25). In-line sampling valves must be madeof a non-corrosive material, such as stainless steel.They should be flushed clean when first installed.

    If connected at a tee in the system, the valveshould be oriented upward or horizontally so thatany sediment in the fluid stream will not tend tosettle into the tee and valve.

    In dynamic systems, sampling valves should belocated at points where baffles or changes in direc-tion or pipe dimensions create turbulence. Ifpossible, they should be installed just before themost contamination-sensitive components in thesystem.

    In static systems, such as storage tanks, the sam-pling valve should be located at the outlet connec-tion. In the case of drums and similar fluidcontainers, the conventional stopcock or drainvalve will usually suffice for sampling purposes.

    Sample CollectionDynamic systems should be operated for severalminutes before taking the sample. This ensuresthat contaminants are evenly distributed through-out the system.

    1. Open the sampling valve while the system isoperating and allow sufficient liquid to flowinto a waste container to flush out the valve.Never take the sample immediately upon

    opening the sampling valve.2. Remove the cap from the sample bottle and

    hold it in your free hand.

    3. Place the bottle into the liquid stream immedi-ately and collect the desired volume (Figure26). Do not rinse the container in the sam-ple fluid.

    4. Remove the container from the stream andreplace the plastic film and cap.

    5. Turn off the sampling valve.

    NOTE:Avoid wiping the sampling valve or theneck of the bottle with a cloth or paper

    towel since this may introduce fibersinto the sample.

    6. Label the container.

    7. Return the sample bottle to the laboratorypromptly for filtration and analysis.

    NOTE:If you would rather analyze your sam-ples on-site, see the Patch Test Kit Col-lection and Filtration section later inthis chapter.

    Figure 25. ESP Valve fitted in horizontal position

    into PVC high purity water line.

    Figure 26. Collecting water sample from ESP Valve

    fitted into D.I. water line.

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    Filtration Equipment PreparationBefore using the laboratory filter apparatus (Figure27), you should carry out the following cleaningprocedure:

    1. Wash the filter holder in a standard laboratorycleaning solution. Rinse with hot water.

    2. Rinse twice with laboratory grade water, dis-pensed from either a solvent filtering dis-penser (Figure 28) or a Filterjet solventdispenser (Figure 24).

    3. Rinse with membrane filtered isopropyl alco-hol (dispensed from either a solvent filteringdispenser or Filterjet solvent dispenser) toremove water and allow to dry.

    For critical applications, check filter holder cleanli-ness by passing clean (already filtered) fluidthrough the filter holder and inspecting the filterfor particles. If particles are visible, the cleaning

    procedure should be repeated or modified.

    Filtration ProcedureThis procedure should be carried out on a sanitarysurface or under a laminar flow hood.

    1. Remove the membrane disc from the packingusing forceps and rinse its surface with mem-brane filtered petroleum ether or a CFC-FreeCleaning Solvent (Figure 29). Place it on thefilter holder base (Figure 30). When using agridded filter, place grid-side up.

    2. Attach the funnel to the base with the springclamp.

    WARNING: If you are filtering petroleumether or other flammable sol-

    vents, you must ensure that theHydrosol unit (XX20 047 20) isgrounded to prevent arcing fromstatic electricity created duringfiltration.

    Figure 27. Liquid filtration system glass filter

    holder, 47 mm, connected to trap and vacuum

    Figure 28. Flushing inside walls of glass filter

    funnel with solvent filtering dispenser.

    Figure 29. Flushing filter with solvent filtering

    dispenser.

    Figure 30. Placing membrane filter on base of

    47 mm glass filter holder.

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    Liquids and Component Monitoring 23

    Filtration Procedure, continued3. Pour the entire contents of the sample bottle

    into the funnel (Figure 31).

    4. Rinse the sample bottle with membrane-fil-tered solvent and pour into the funnel.

    5. Apply vacuum to the filter flask. When filtra-

    tion is almost complete, release the vacuum.

    6. Use some membrane-filtered solvent to care-fully rinse the funnel walls while some liquidstill remains in the funnel (Figure 32). Do notdirect the solvent stream onto the filter surface it will disturb the particle distribution. Usea solvent that evaporates readily so that the fil-ter dries quickly. You can obtain informationon recommended quick drying CFC-Cleanersfrom Millipore's Technical Service.

    7. Apply vacuum and pull the remainder of thefluid through the Millipore filter disc.

    For gravimetric analysis only: While vac-uum is applied, rinse the surface of the filterwith a jet of filtered solvent, moving the accu-mulated sediment towards the center of the fil-ter.

    For microscopic particle counting: To avoiddisturbing the even distribution of particles onthe filter surface, do not rinse the funnel wallsor the filter surface.

    8. Release the vacuum.

    9. Remove the funnel from the holder. Using for-ceps, immediately place the Millipore filter in

    a clean plastic PetriSlide identified with thesample number.

    Figure 31. Pouring liquid sample into funnel of

    47 mm glass filter holder.

    Figure 32. Rinsing the funnel walls.

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    Patch Test Kit Collection and FiltrationIf you need to analyze your sample on-site, useMillipores Patch Test Kit, a portable filtration sys-tem that includes filter color rating and particleassessment scales that correspond to recognizedstandard contamination levels.

    Equipment PreparationBefore using the Patch Test Kit, you should carryout the following assembly and cleaning proce-dure:

    1. Assemble test filtration apparatus. Remove47 mm filter holder assembly from vacuum fil-tration flask, if necessary using butt end of for-ceps to pry against flask rim at cut-out slot(Figure 33). Invert holder assembly and installin flask with funnel up, seating holder baseflange evenly against flask rim.

    2. Wash down inside of funnel. Close vent holein solvent dispenser cap with finger tip, andsqueeze bottle to direct jet of filtered solventagainst all inner surfaces of funnel (Figure 34).Use enough solvent to carry all contaminantsthrough filter holder screen and into flask.

    3. Install test filter. Remove funnel from test fil-ter holder by turning knurled ring to left untilfree, then lifting. With forceps, center a 47 mmwhite test filter disc on wire mesh supportscreen (Figure 35). Replace funnel, andretighten knurled ring to seal filter in place.

    4. Attach syringe vacuum pump.The free end

    of the flexible tube attached to the syringe isfitted with a small nylon adapter. Insertadapter firmly into small hole on side of filterholder base (Figure 36). Tube and adapter arenormally left attached to syringe for storage,but can be removed for cleaning.

    Sample CollectionUsing filtered solvent, rinse out the inside of theclear plastic bottle you will use to hold test fluidsample, then discard the used solvent (Figure 37).Fill the sample bottle to the shoulder point withfluid to be tested, and cap securely.

    Figure 33. Remove 47 mm filter holder assembly

    from vacuum filtration flask.

    Figure 34. Wash down inside of funnel.

    Figure 35. Center 47 mm white test filter disc on

    wire mesh support screen.

    Figure 36. Insert adapter in the end of the syringe

    tube into hole on side of filter holder base.

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    Liquids and Component Monitoring 25

    Filtration Procedure1. Filter test sample. Shake sample bottle, and

    pour contents into funnel, pouring against fun-nel walls to distribute fluid evenly over filter.Then work syringe plunger to draw vacuuminside flask, until level of fluid in funnel just

    begins to fall, showing start of filtration (Fig-ure 38).

    2. Rinse contamination from sample bottle.Fill test sample bottle 1/3 full with filtered sol-vent, shake thoroughly, and pour into funnelas soon as level of fluid permits (Figure 39).Operate syringe again to sustain filtration ifnecessary.

    3. Rinse contamination from funnel walls.When sample level in funnel drops to narrowneck of funnel, wash down inner surfaces offunnel with stream from filtered solvent dis-penser (Figure 34). Do not let solvent stream

    directly strike test filter. Work syringe to drawall fluid through filter.

    4. Check test filter against standard. Removefunnel from base, lift off test filter with for-ceps, place face-up in uncovered PetriSlide,and let dry completely in still air. Replace Pet-riSlide cover, and compare filter appearancewith standard to determine the contaminantlevel (Figure 40). If trichloroethane or drycleaning fluid is used as solvent, filter must bedry before placing in PetriSlide, to avoidclouding plastic.

    COMPONENTS MONITORINGAll components monitoring procedures involverinsing the item to be sampled with particle-freesolvent, then recovering the solvent and filtering itthrough a Millipore filter for subsequent analysis.

    The recovery of particles and reproducibility of thetest will depend upon:

    The nature of the solvent used. CFC-Free Con-tact Cleaners or alcohol, and water are com-monly used. Once you have chosen a solvent,avoid switching from one to another.

    The volume of solvent per unit surface area. The flow intensity of spray velocity.

    The intensity of any mechanical or ultrasonicagitation of the liquid in contact with the sur-face.

    Figure 37. Rinse inside of sample collection con-

    tainer.

    Figure 38. Work syringe plunger to draw vacuum

    inside flask.

    Figure 39. Rinse contaminant from sample bottle

    and pour into funnel.

    Figure 40. Check test filter against standard to

    determine contamination level.

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    COMPONENTS MONITORING,continued

    In establishing a test procedure, you must fix thesefactors as part of the test criteria. The examplesthat follow are illustrative only. You may analyzethe collected liquid by any of the procedures listedin the Analytical Methods for Determination ofParticle Contamination section in Chapter I,although particle counting analyses are most oftenused. Once established, conduct the test procedurefor a given device the same way each time toachieve maximum reproducibility.

    Tubing and Hoses Sampling Short Lengths: Fill the tubing you need to test

    approximately 3/4 full with a membrane-fil-tered solvent. Cap each end and turn end overend or flex six times. Decant the solvent

    directly into a clean glass filter holder or into aclean sample bottle. Process sample for filtra-tion in the laboratory.

    Long Lengths:Connect a source of pressurized,membrane-filtered solvent to the test tubing.Place the membrane filter immediately beforethe tubing to be tested. Collect the solventfrom the end of the tubing in a clean samplebottle. (Use 10X the internal tubing volume asa guide to the total solvent volume. If largevolumes of solvent are used, it may be neces-sary to take a sample from the collected sol-vent.) Process sample for laboratory filtration.

    Small Valves and Manifolds SamplingConnect the part by means of suitable adaptersand clean hoses to a source of pressurized mem-brane filtered solvent. Collect the solvent at theoutlet of the part in a clean sample bottle or pass itthrough a Millipore sampler.

    Large Valves and Fittings SamplingTransport the part in a clean container protectedfrom plant and machining debris. Remove any pro-tective covers. Hold the component with gloved

    hand (preclean the glove if necessary) over a filterholder funnel, a clean sample container or a cleantray (Figure 41). Direct a forceful stream of mem-brane filtered solvent over entire componentincluding inner surfaces and crevices. Collect theentire volume of liquid for analysis. Use approxi-mately 200 mL of solvent per square foot of sur-face area (2 L/m2). Apply at least 200 mL offlushing solvent, regardless of component size.

    Figure 41. Flushing component with Filterjet gun

    (connected to pressurized solvent reservoir).

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    IV

    OPTICAL MICROSCOPE PARTICLE COUNTINGDirect particle counting on a Millipore filter is a simple and rapid procedure where youexamine the filter directly with incident light or render it transparent so that you can applytransmitted light. The filter is placed directly on the movable stage of a binocular micro-scope with the contaminant side up. It is slowly traversed back and forth. As particlescome into the field of view they are counted in several discrete size ranges.

    Using the light microscope for direct counting on a filter offers a number of importantadvantages. You can:

    Determine the size distribution of particles.

    Detect large particles or fibers easily.

    Identify particles to locate sources of contamination.

    You can vary the procedure to accomplish your specific goals. When you are only inter-ested in very large particles (>150 m), you can be less careful about cleaning your equip-ment. If appropriate, save time by counting particles down to 50 or 100 m rather thandown to 2 or 5 m, since such procedures are adequate in many instances.

    In all particle counting procedures, adequate illumination, well-aligned optics and carefuloperator training are necessary.

    Analysis

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    Filter ClearingFor transmitted light microscopy, you must renderthe filter transparent, a procedure called clearingthe filter. Several methods are available, but youshould always use mixed esters of cellulose mem-brane filters.

    Acetone/Triacetin Method1. Switch on the acetone heating block and hot

    plate.

    2. Put a small volume of acetone in the syringe.

    3. Cut the filter into four quarters using a rockingmotion with a sharp scalpel (Figure 42).

    4. Place a quarter of the membrane filter (sampleside up) on a cleaned glass microscope slide(Figure 43). The other quarters are availablefor additional tests.

    5. Place the slide on the small stand approxi-

    mately 2 cm below the outlet of the vaporizer(Figure 44).

    6. Inject 0.25 mL of acetone. The filter normallyclears immediately. If it does not totally clear,repeat the acetone injection and reduce theslide to outlet distance for subsequent filters.

    7. Place one to three drops of glycerol triacetate(Triacetin) on the acetone cleared filter (Figure45), then immediately lower a clean cover sliponto the Triacetin at an angle (Figure 46). Donot press on the cover slip. A cover slip isessential if particles below 5 m are to becounted.

    8. Heat the filter on the hot plate for a few min-utes to accelerate the clearing process (ifneeded). The mounted filter is stable and willnot disintegrate.

    Once the filter sample has been cleared andmounted, carry out ordinary light and phase con-trast microscopy. If you used a gridded filter, thegrids will remain visible to aid counting and togive a focal plane of reference.

    Figure 42. Cutting quarters from particle-laden

    25 mm filter for subsequent clearing and examination.

    Figure 43. Placing filter section onto a cleaned

    1" x 3" microscope slide.

    Figure 44. Clearing filter with acetone vapor

    stream from acetone vaporizer.

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    Analysis 29

    Dimethylphthalate and Diethyloxylate MethodTo prepare mounting medium:

    1. Dissolve Millipore aerosol analysis filter in a1:1 solution of dimethylphthalate and diethy-loxylate (ratio of 0.2 g filter to 1 mL of solu-tion). You can make up large volumes of this

    solution and store it out of sunlight in a stop-pered bottle. Filter mounting medium as it isdispensed using a solvent-resistant syringe fil-ter unit.

    2. Place a drop of mounting medium on a freshlycleaned glass microscope slide to mount themembrane filter sample. For best results whencleaning slides, rinse with filtered CFC-FreeContact Cleaner.

    3. Use a scalpel to cut a wedge-shaped piecefrom the filter with an arc length of about 1cm. Carefully store the remaining filter. Avoidcontamination in the event a second wedge

    must be cut.4. Transfer the wedge of filter (keep sample side

    up) to the drop of mounting media usingsmooth tipped filter forceps. Cover with acover slip. The filter becomes transparent inabout 15 minutes at room temperature.

    Microscope Immersion Oil MethodUsing forceps, float the filter on a film of immer-sion oil in the cover of a plastic petri dish. Drawthe filter over the rim of the cover to remove anyexcess oil and mount on the glass microscopeslide.

    EquipmentWhen using a Millipore Fluid Contamination Anal-ysis Kit to collect samples, you will need only themicroscope illuminator, stage micrometer and tallycounter.

    A suitable microscope for particle counting shouldhave:

    a binocular body

    a mechanical stage

    a multiple nosepiece

    4X, 10X and 20X objectives a 10X Kellner or wide-field eye piece

    The Millipore XX76 100 00 microscope meetsthese requirements.

    Figure 45. Adding Triacetin solution to acetone

    cleared filter.

    Figure 46. Cover slip placed at an angle over

    cleared filter containing Triacetin.

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    Measuring Eyepiece (Reticle) CalibrationBefore counting and measuring particles, you mustcalibrate the measuring eyepiece reticle of themicroscope using a stage micrometer. The scale iscalibrated with each objective to be used in thecounting/measuring procedure.

    The stage micrometer is a glass slide with etchedgraduations (Figure 47). These graduations areaccurately measured in millimeters as follows:(a) From A to B = 1 mm (1000 m); (b) From B toC = 0.1 mm (100 m); (c) From C to D = 0.01 mm(10 m).

    1. Swing the lowest magnification objective intoposition.

    2. Remove the eyepiece from the microscope(Figure 48) to focus the eyepiece reticle. Lookthrough the eyepiece with one eye and focusthe reticle while keeping the second eye openand focused into the distance. This procedure

    minimizes eye strain when particle counting.Replace the eyepiece in the microscope.

    3. Place the stage micrometer onto the micro-scope stage. Adjust the microscope to bringthe graduations of the stage micrometer intosharp focus.

    4. Line up the eyepiece reticle with the stagemicrometer (Figure 49).

    Assuming that the example diagram representswhat is seen when using a 4X objective (and10X ocular), line up and calibrate the reticledivisions. Based upon 100 divisions of this ret-

    icle subtending 1050 m on the stagemicrometer, the calibration would be:

    The figure of 10.5 m/fine division wouldremain fixed for this particular combination ofmicroscope, 4X objective, 10X eyepiece andreticle.

    5. Repeat the above tests for the other objectivesto be used.

    6. Make a note of these calibration factors for

    future use with this microscope.

    1010

    100= 10.5 m per fine division

    A B CD

    STAGE MICROMETER

    Dimemsions

    A to B = 1 mm (1000 m)B to C = 0.1 mm (100 m)C to D = 0.01 mm (10 m)

    Figure 47. A standard stage micrometer.

    MEASURING EYEPIECE

    0 20 40 60 80 100

    Figure 48. A standard measuring eyepiece (reticle)

    containing 100 linear graduations.

    1,050 m

    100 Divisions of Eyepiece subtend 1,050m Each division of eyepiece = 10.5m

    0 20 40 60 80 100

    Figure 49. Knowing the subdivisions of the stage

    micrometer (top), the divisions of the measuring

    eyepiece (bottom) may be sized from it and will

    remain constant at that magnification.

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    Analysis 31

    Particle CountingCalibrate the eyepiece scale if this has not beendone. When using transmitted light microscopy,you must first render the filter transparent. (Seeprevious section Filter Clearing.) This procedureresults in a transparent wedge of filter mounted on

    a glass microscope slide. If you are using incidentlight microscopy, place the Millipore filter on a 2"x 3" glass microscope slide (1" x 3" is adequate for25 mm filters). You may want to grease the slidelightly to hold the filter in place. A PetriSlide maybe used as an alternative.

    1. Mount the glass slide or PetriSlide containingthe filter onto the microscope stage.

    2. Move the microscope stage so that the parti-cles on the membrane appear to pass underthe measuring eyepiece (Figure 50). Count thenumber of particles in each designated sizerange found in a number of fields selected

    using the double diameter counting plan (Fig-ure 51). The number of particles counted mul-tiplied by the number of fields should be equalto or greater than 500. A field may be any des-ignated area, but is most commonly defined bythe width of a grid square on the Millipore fil-ter (3.08 mm) and the length or a portion ofthe length of the measuring eyepiece scale.Always size particles by their longest dimen-sions. Fibers (i.e. particles larger than 100 mwith a length to width ratio greater than 5:1)are usually listed separately.

    3. Count the entire filter surface when counting arelatively small number of particles at lowmagnification, as shown in Figure 52.

    When less than the entire filter surface iscounted, multiply the number of particlesactually counted by the total filter area dividedby the area counted. The conversion factor touse is:

    where:

    A = Effective filtering area in mm of Millipore fil-

    ter disc. For glass filter holders it is 960 mm.Use 900 for field cassettes. (For other filtersand holders, refer to the Millipore laboratorycatalogue).

    3.08 = Width in mm of filter grid square.

    L = Length in mm of unit area.

    N = Number of unit areas counted.

    A

    3.08 LN

    1

    0

    2

    3

    4

    5

    L

    3.08 mm

    SuggestedUnit Area

    AlternateUnit Area(for highlycontaminatedsample)

    Grid Square

    FieldObservedThrough

    Microscope

    MeasuringEyepiece

    Scale

    Figure 50. With Millipore filter on the microscope

    stage, movement of the stage makes particles appear to

    pass under the divisions on the measuring eyepiece.

    Figure 51. Double-diameter counting plan (count

    articles in shaded areas).

    0

    20

    Figure 52. When scanning the entire filter at 40X

    magnification, the ocular micrometer scale is

    vertically aligned at the top left of the filtration

    area. The filter is scanned from left to right in the

    first pass, and each successive pass travels in the

    opposite direction.

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    Particle Counting, continuedA typical counting work sheet is shown in Figure53. Any particle size ranges may be used. Theseranges are taken from SAE ARP-598A.

    When you take samples of materials such ashydraulic fluids by means of the fluid sampler, it is

    important that you remove all excess fluid fromthe Millipore filter using a vacuum syringe beforethe cassette is opened. (See the On-Line SampleCollection and Filtration section in Chapter III fordetails on the fluid sampler.) Flushing solventthrough the cassette at this point may seriouslydisturb the particle distribution. It is always goodpractice to prepare a blank, proceeding through allthe filtering and counting operations without intro-ducing any sample to determine the backgroundcount. This is an excellent measure of glassware,solvent and technique cleanliness. Blank countsshould not exce