EPA-600/2-76-280
October 1976
Environmental Protection Technology Series
PARTICULATE SIZING TECHNIQUES FOR
CONTROL DEVICE EVALUATION-
CASCADE IMPACTOR CALIBRATIONS
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed
to develop and demonstrate instrumentation, equipment and
methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the
new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the U. S. Environmental Protection
Agency, and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the Agency, nor
does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
This document is available to the public through the National
Technical Information Service, Springfield, Virginia 22161.
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EPA-600/2-76-280
October 1976
PARTICULATE SIZING TECHNIQUES
FOR CONTROL DEVICE EVALUATION:
CASCADE IMPACTOR CALIBRATIONS
by
Kenneth M. Gushing, George E. Lacey,
Joseph D. McCain, and Wallace B. Smith
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
Contract No. 68-02-0273
ROAPNo. 21ADM-011
Program Element No. 1AB012
EPA Project Officer: D. Bruce Harris
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
FOREWORD
As part of a program to evaluate pollution control devices
for stationary sources, the Process Measurement Branch, Industrial
Environmental Research Laboratory, Environmental Protection Agency,
has contracted Southern Research Institute to improve the state of
the art for making particle size measurements. Although this work
is continuing, the completion of this initial contract represents
the attainment of a significant milestone because it has lead to
the understanding and solution of several important problems
related to particle sizing. This work has resulted in several
reports which describe the development of prototype systems and
procedures for making particle size measurements in industrial
flue gases.
This final report includes the results of a calibration
study which was done to evaluate and quantify the behavior of
cascade impactors and to determine the accuracy of theories for
predicting their performance. The data included in this report
are unique and should be beneficial to cascade impactor users
and manufacturers.
fabert Ogfesby
Vice President
Southern Research Institute
11
-------
ABSTRACT
A calibration study of five commercially available cascade
impactors has been conducted to determine sizing parameters and
wall losses. A Vibrating Orifice Aerosol Generator was used to
produce monodisperse ammonium fluorescein aerosol particles 18
micrometers to 1 micrometer in diameter. A pressurized Collison
Nebulizer System was used to disperse Dow Corning Polystyrene
Latex (PSL) spheres 2 micrometers to 0.46 micrometer in diameter.
When ammonium fluorescein was used the mass collected by each
impactor surface was determined using absorption spectropho-
tometry of washes from the various surfaces. When sizing with
the PSL spheres a Climet Instruments Model 208A Particle Analyzer
was used to determine particle number concentrations at the inlet
and outlet of the test impactor. Results are reported showing
stage collection efficiency as a function of the square root of
the Stokes number, stage collection efficiency as a function of
particle size, and impactor wall losses (total, nozzle, and
inlet cone) as a function of particle size. It has been
determined that the values of the Stokes number for the 50%
collection efficiency are not generally the same for each impactor
stage. A table of these values is presented. Published theories
do not successfully predict these /tJ75 0 values, so empirical cali-
bration is required before these devices can be accurately used
in the field or laboratory.
-------
CONTENTS
Page
Foreword ii
Abstract iii
Figures v
Tables xii
Abbreviations and Symbols xiii
Acknowledgements xiv
1. Introduction 1
2. Conclusions 12
3. Description of Experimental Procedures 14
4 . Results of the Calibration Study 21
Wall losses 21
Calibration data - efficiency vs. /ijJ" 29
Calibration data - efficiency vs. particle
size 31
References 78
IV
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FIGURES
Number Page
1 Theoretical impactor efficiency curves for rectangular
and round impactors showing the effect of jet-to-plate
distance S, Reynolds number Re, and throat length T5. . 11
2 Schematic representation of the Vibrating Orifice
Aerosol Generator ................... 15
3 Ammonium fluorescein aerosol particles generated
using the Vibrating Orifice Aerosol Generator ..... ^
4 PSL calibration system for high and low flowrate
impactor ........................ 20
5 Impactor wall loss versus particle size. Andersen
Mark III Stack Sampler. (14 LPM, 22°C, 29.5" Hg,
1.35 gm/cm3) Nonisokinetic sampling .......... 22
6 Impactor wall loss versus particle size. Modified
Brink Model BMS-11 Cascade Impactor (Glass Fiber
Substrates). (0.85 LPM, 22°C, 29.5" Hg, 1.35 gm/cm3)
Nonisokinetic sampling ................. 23
7 Impactor wall loss versus particle size. Modified
Brink Model BMS-11 Cascade Impactor (Greased Col-
lection Plates). (0.85 LPM, 22°C, 29.5" Hg,
1.35 gm/cm3) Nonisokinetic sampling .......... 24
8 Impactor wall loss versus particle size. MRI Model
1502 Inertial Cascade Impactor. (14 LPM, 22°C,
29.5" Hg, 1.35 gm/cm3) Nonisokinetic sampling ..... 25
9 Impactor wall loss versus particle size. Sierra
Model 226 Source Cascade Impactor. (14 LPM, 22°C,
29.5" Hg, 1.35 gm/cm3) Nonisokinetic sampling ..... 26
10 Impactor wall loss versus particle size. Sierra
Model 226 Source Cascade Impactor. (7 LPM, 22°C,
29.5" Hg, 1.35 gm/cm3) Isokinetic sampling, ...... 27
v
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FIGURES (CONT'D)
Number Pag
11 Impactor wall loss versus particle size. University
of Washington Mark III Source Test Cascade Impactor.
(14 LPM, 22°Cf 29.5" Hg, 1.35 gm/cm3)
Nonisokinetic sampling ................. 28
12 Collection Efficiency (%) Versus Sty
Andersen Mark III Stack Sampler
Stage 1 - Stage 2
Uncorrected for Wall Losses . . . . „ ......... 32
13 Collection Efficiency (%) Versus /jj
Andersen Mark III Stack Sampler
Stage 3 - Stage 5
Uncorrected for Wall Losses .............. 33
14 Collection Efficiency (%) Versus /ij7
Andersen Mark III Stack Sampler
Stage 6 - Stage 8
Uncorrected for Wall Losses .............. 34
15 Collection Efficiency (%) Versus /ijj"
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Glass Fiber Substrates)
Uncorrected for Wall Losses .............. 35
16 Collection Efficiency (%) Versus /$
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Glass Fiber Substrates)
Uncorrected for Wall Losses .............. 36
17 Collection Efficiency (%) Versus /IJ7
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Greased Collection Plates)
Uncorrected for Wall Losses .............. 37
18 Collection Efficiency (%) Versus /$
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Greased Collection Plates)
Uncorrected for Wall Losses .............. 38
VI
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FIGURES (CONT'D)
Number Page
19 Collection Efficiency (%) Versus Sty
MRI Model 1502 Inertial Cascade Impactor
Stage 1 - Stage 3
Uncorrected for Wall Losses ..... ......... 39
20 Collection Efficiency (%) Versus /ijj
MRI Model 1502 Inertial Cascade Impactor
Stage 4 - Stage 7
Uncorrected for Wall Losses .............. 40
21 Collection Efficiency (%) Versus Sfy
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 14 LPM
Uncorrected for Wall Losses .............. 41
22 Collection Efficiency (%) Versus /i|7
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 14 LPM
Uncorrected for Wall Losses .............. 42
23 Collection Efficiency (%) Versus /i]7
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 7 LPM
Uncorrected for Wall Losses ..............
24 Collection Efficiency (%) Versus Sty
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 7 LPM
Uncorrected for Wall Losses .............. 44
25 Collection Efficiency (%) Versus /J7
University of Washington Mark III Cascade
Impactor Stage 1 - Stage 4
Uncorrected for Wall Losses .............. 45
26 Collection Efficiency (%) Versus /ijj" ,
University of Washington Mark III Cascade
Impactor Stage 5 - Stage 7
Uncorrected for Wall Losses .............. 46
VII
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FIGURES (CONT'D)
Number Page
27 Collection Efficiency (%) Versus-Sty
Andersen Mark III Stack Sampler
Stage 1 - Stage 2
Corrected for Wall Losses 47
28 Collection Efficiency (%) Versus S$
Andersen Mark III Stack Sampler
Stage 3 - Stage 5
Corrected for Wall Losses 48
29 Collection Efficiency (%) Versus ^
Andersen Mark III Stack Sampler
Si'tage 6 - Stage 8
Corrected for Wall Losses 49
30 Collection Efficiency (%) Versus /tjJ"
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Glass Fiber Substrates)
Corrected for Wall Losses 50
31 Collection Efficiency (%) Versus /i|>
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Glass Fiber Substrates)
Corrected for Wall Losses 51
32 Collection Efficiency (%) Versus /jj"
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Greased Collection Plates)
Corrected for Wall Losses 52
33 Collection Efficiency (%) Versus vAj7
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Greased Collection Plates)
Corrected for Wall Losses 53
34 Collection Efficiency (%) Versus /JT
MRI Model 1502 Inertial Cascade Impactor
Stage 1 - Stage 3
Corrected for Wall Losses 54
viii
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FIGURES (CONT'D)
Number Page
35 Collection Efficiency (%) Versus v/ijj"
MRI Model 1502 Inertial Cascade Impactor
Stage 4 - Stage 7 55
Corrected for Wall Losses ...............
36 Collection Efficiency (%) Versus /ij7
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 14 LPM
Corrected for Wall Losses ...............
37 Collection Efficiency (%) Versus S§
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 14 LPM
Corrected for Wall Losses . .............. 57
38 Collection Efficiency (%) Versus S§
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 7 LPM
Corrected for Wall Losses ............... 5°
39 Collection Efficiency (%) Versus /ij7
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 7 LPM
Corrected for Wall Losses ............... ^
40 Collection Efficiency (%) Versus /$
University of Washington Mark III Cascade
Impactor Stage 1 - Stage 4
Corrected for Wall Losses ...... .........
41 Collection Efficiency (%) Versus /ijj"
University of Washington Mark III Cascade
Impactor Stage 5 - Stage 7
Corrected for Wall Losses ............... 61
42 Collection Efficiency (%) Versus Particle Size
Andersen Mark III Stack Sampler (Stage 1 - Stage 8)
Uncorrected for Wall Losses (14 LPM, 22°C,
29.5" Hg, 1.00 gm/cm3) ................. 62
IX
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FIGURES (CONT'D)
Number Page
43 Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Glass Fiber Substrates) (Stage 0 - Stage 6)
Uncorrected for Wall Losses (0.85 LPM, 22°C,
29.5" Hg, 1.00 gm/cm3) 63
44 Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Greased Collection Plates)(Stage 0 - Stage 6)
Uncorrected for Wall Losses (0.85 LPM, 22 °C,
29.5" Hg, 1.00 gm/cm3) 64
45 Collection Efficiency (%) Versus Particle Size
MRI Model 1502 Inertial Cascade Impactor
(Stage 1 - Stage 7) Uncorrected for Wall Losses
(14 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3) 65
46 Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(14 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3)
(Stage 1 - Stage 6) Uncorrected for Wall Losses. ... 66
47 Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(7 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3)
(Stage 1 - Stage 6)
Uncorrected for Wall Losses 67
48 Collection Efficiency (%) Versus Particle Size
University of Washington Mark III Cascade Impactor
(14 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3)
(Stage 1 - Stage 7) Uncorrected for Wall Losses. ... 68
49 Collection Efficiency (%) Versus Particle Size
Andersen Mark III Stack Sampler (Stage 1 - Stage 8)
Corrected for Wall Losses
(14 LPM), 22°C, 29.5" Hg, 1.00 gm/cm3) 69
x
-------
FIGURES (CONT'D)
Number Page
50 Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Glass Fiber Substrates) (Stage 0 - Stage 6)
Corrected for Wall Losses
(0.85 LPM, 22°C, 29.5" Hg, 1.00 gin/ cm 3 ) . ....... 70
51 Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Greased Collection Plates) (Stage 0 - Stage 6)
Corrected for Wall Losses
(0.85 LPM, 22°C, 29.5° Hg, 1.00 gm/cm3 ) ........ 71
52 Collection Efficiency (%) Versus Particle Size
MRI Model 1502 Inertial Cascade Impactor
(Stage 1 - Stage 7) Corrected for Wall Losses 7?
(14 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3) .........
53 Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(14 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3)
(Stage 1 - Stage 6) Corrected for Wall. .Losses ..... 73
54 Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(7 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3)
(Stage 1 - Stage 6) Corrected for Wall Losses ..... 74
55 Collection Efficiency (%) Versus Particle Size
University of Washington Mark III Cascade Impactor
(14 LPM, 22°C, 29.5" Hg, 1.00 gm/cm3) .
(Stage 1 - Stage 7) Corrected for Wall Losses ..... 75
xi
-------
TABLES
Number Page
1 Cascade Impactor Calibration Study Operational
Parameters ....................... 2
2 Cascade Impactor Stage Parameters Andersen Mark III
EJtack Sampler ..................... 4
3 Cascade Impactor Stage Parameters Modified Brink
Model B Cascade Impactor ................ 5
4 Cascade Impactor Stage Parameters MRI Model 1502
Inertial Cascade Impactor ............... 6
5 Cascade Impactor Stage Parameters Sierra Model 226
Source Sampler ..................... 7
6 Cascade Impactor Stage Parameters University of
Washington Mark III Source Test Cascade Impactor. ... 8
7 Square Root of the Stokes Number at 50% Collection 75
Efficiency, /ijlso ...................
8 Particle Diameter (Micrometer) at 50% Collection
Efficiency, D so ... ................ 77
Xll
-------
LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
ACFM — Actual Cubic Feet Per Minute
C — Cunningham Slip Correction Factor, dimensionless
C — Vibrating Orifice Generator Solution Concentration
D — Particle Diameter, cm
d — Vibrating Orifice Generator Dry Particle Diameter, cm
D so — Particle Diameter at 50% Collection Efficiency
P
D. — Impactor Stage Jet Diameter, cm
F — Vibrating Orifice Generator Crystal Oscillation
Frequency, Hz
LPM — Liters Per Minute
PCNS — Pressurized Collison Nebulizer System
Q — Vibrating Orifice Generator Solution Flowrate, cm3/min
RE — Reynolds Number, pV.D./u or pV. 2W/y
S — Impactor Jet to Plate Spacing, cm
T — Impactor Jet Throat Length, cm
V. — Impactor Jet Velocity, cm/sec
VOAG — Vibrating Orifice Aerosol Generator
W — Impactor Jet Slot Width, cm
Symbols
p — Gas Density, gm/cm3
Pp — Density of Particle
M — Gas Viscosity, poise
4> — Stokes Number, dimensionless
ffys o — Square Root of Stokes Number at 50% Collection
Efficiency
Xlll
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ACKNOWLEDGMENTS
The cooperation, helpful suggestions and overall interest
shown by the Project Officer, D. Bruce Harris, during this three
year study is gratefully acknowledged.
xiv
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SECTION 1
INTRODUCTION
This final report for EPA Contract Number 68-02-0273
presents a comprehensive description of the methods and results
of a two year evaluation and calibration study of five com-
mercially available cascade impactors. These cascade impactors
and their manufacturers are listed below:
1.) Andersen Mark III Stack Sampler (Andersen)
Andersen 2000, Inc.
Atlanta, Georgia 30320
2.) Brink Model BMS-11 Cascade Impactor (Brink)
Monsanto Enviro-Chem Systems, Inc.
St. Louis, Missouri 63166
3.) MRI Model 1502 Inertial Cascade Impactor (MRI)
Meteorology Research, Inc.
Altadena,'California 91001
4.) Sierra Model 226 Source Cascade Impactor (Sierra)
Sierra Instruments, Inc.
Carmel Valley, California 93924
5.) University of Washington Mark III Source Test Cascade
Impactor (U. of W,)
Pollution Control Systems, Inc.
Renton, Washington 98055
The normal 5-stage Brink impactor has been modified by
Southern Research Institute to include an inline cyclone pre-
collector, a "0" stage, and a "6" stage.
Table 1 includes the operational parameters of the five
cascade impactors used in this study. The Brink was the only
impactor tested with two types of collection media. The Sierra
impactor was the only one systematically tested at two different
flowrates.
The Andersen impactor is used with glass fiber substrates
supplied by the manufacturer. For the Brink impactor a small
disc of glass fiber material was tested as well as a thin grease
-------
TABLE 1
Cascade Impactor Calibration Study
Operational Parameters
Laboratory Conditions - 73°F/22°C
29.5" Hg/750 mm Eg
Aerosol Particles - Ammonium Fluorescein Density - 1.35 gm/cm3
- Polystyrene Latex Density - 1.00 gm/cm3
No. of
Nominal Sampling
Impactor
Andersen
Brink (Modified)
Brink (Modified)
MRI
Sierra
Sierra
U of Washington
Stages
8
7
7
7
6
6
7
Substrate Material
Pre-cut glass fiber
filter mats
Glass fiber filter
inserts
Greased collection
plates
Greased collection
plates
Pre-cut glass fiber
filter mats
Pre-cut glass fiber
filter mats
Greased collection
plates
Flowrate
0.5 ACFM/
14.16 LPM
0.03 ACFM/
.85 LPM
0.03 ACFM/
.85 LPM
0.5 ACFM/
14.16 LPM
0.5 ACFM/
14.16 LPM
0.2 5 ACFM/
7.08 LPM
0 . 5 ACFM/
14.16 LPM
-------
layer. The MRI and U. of W. impactors are used with thin films
of grease on the collection plates. The Sierra is supplied with
pre-cut glass fiber mats.
The individual stage parameters for the Andersen, Brink,
MRI, Sierra, and U. of W. are listed in Table 2 through Table 6,
respectively. Even though the critical interior dimensions of
each impactor were supplied by the manufacturer, a measurement
of each quantity was also performed as a check. This was
necessary because differences in a jet diameter, for example,
can have a major influence on the collection characteristics of
an impactor stage. The Cumulative Fraction of the Impactor
Pressure Drop at each Stage was measured at the nominal flowrate;
however, this relationship should be valid at all practical
flowrates for which each impactor could be used. The Reynolds
number and jet velocities are based on the nominal flowrates
given for each impactor in Table 1.
To the user of an inertial cascade impactor the most
important consideration is the degree to which the data that is
obtained will duplicate the actual particulate size distribution
which is sampled. In order to transform the mass collected by
several impaction stages into a size distribution, an accurate
knowledge of the relationship between collection efficiency and
particulate size for each stage is essential.
Theoretically,, cascade impactor operation can be described
by the theory of impaction from a jet. The end result of such a
calculation is impaction efficiency versus particle size. Impac-
tion efficiency is defined as the fraction of particles of a
certain size in the jet which impact on a collection plate.
This value can be obtained theoretically or experimentally under
ideal conditions. The collection efficiency of an impactor
stage, however, is the ratio of the mass (or number) of particles
of a certain size collected on an impaction surface to the total
mass (or number) of particles of the same size in a jet impinging
on that surface. The collection efficiency is the product of the
theoretical impaction efficiency and the adhesion efficiency.3
The adhesion efficiency is the fraction of the number of
particles which adhere to the surface after touching it by the
impaction process. This depends in a large part on the surface
characteristics of the particle and collection surface. Thus,
there will be disagreement between the theoretical impaction
efficiency and the experimentally determined collection
efficiency in the cases where particle bounce, reentrainment,
electrostatic effects, wall losses and non-ideal geometry have
an effect. For this reason, the theory of impaction may not be
sufficiently accurate in predicting impactor performance.
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TABLE 2
Cascade Impactor Stage Parameters
Andersen Mark III Stack Sampler
Stage
No.
1
2
3
4
5
6
7
8
No. of
Jets
264
264
264
264
264
264
264
156
D.-Jet
Diameter
(cm)
.1638
.1253
.0948
.0759
.0567
.0359
.0261
.0251
S-Jet
to Plate
Distance
(cm)
.254
.254
.254
.254
.254
.254
.254
.254
S
°j
1.55
2.03
2.68
3.35
4.48
7.08
9.73
10.12
Reynolds
Number
45
59
78
98
131
206
284
500
Jet
Velocity
(m/sec)
0.4
0.8
1.3
2.0
3.6
9.0
17.1
31.5
Cumulative Frac-
tion of Impac-
tor Pressure Drop
at each stage
0.0
0.0
0.0
0.0
0.0
0.2
0.3
1.0
-------
TABLE 3
Cascade Impactor Stage Parameters
Modified Brink Model B Cascade Impactor
Stage
No.
0
1
2
3
4
5
6
No. of
Jets
1
1
1
1
1
1
1
D.-Jet
Diameter
(cm)
.3598
.2439
.1755
.1375
.0930
.0726
.0573
S-Jet
to Plate
Distance
(cm)
1
0
0
0
0
0
0
.016
.749
.544
.424
.277
.213
.191
S
D.
3
2
3
3
3
2
2
3
.82
.07
.10
.08
.98
.93
.33
Reynolds
Number
326
481
669
853
1263
1617
2049
Jet
Velocity
(m/sec)
1.
3.
6.
9.
21.
35.
58.
4
0
0
7
2
3
8
Cumulative Frac-
tion of Impac-
tor Pressure Drop
at each stage
0.
0.
0.
0.
0.
0.
1.
0
0
0
0
065
255
000
-------
TABLE 4
Cascade Impactor Stage Parameters
MRI Model 1502 Inertial Cascade Impactors
Stage No. of
No. Jets
1 8
2 12
3 24
4 24
5 24
6 24
7 12
D.-Jet
D
Diameter
(cm)
0.
0.
0.
0.
0.
0.
0.
870
476
205
118
084
052
052
S-Jet
to Plate
Distance
(cm)
0
0
0
0
0
0
0
.767
.419
.191
.191
.191
.191
.191
S
D .
D
.88
.88
.96
1.61
2.27
3.60
3.60
Reynolds
Number
281
341
411
684
973
1530
3059
Cumulative Frac-
Jet tion of Impac-
Velocity tor Pressure Drop
(m/sec) at each stage
0
1
3
8
18
45
102
.5
.1
.2
.9
.2
.9
.3
0.
0.
0.
0.
0.
0.
1.
0
0
0
0
045
216
000
-------
TABLE 5
Cascade Impactor Stage Parameters
Sierra Model 22"6 Source Sampler
Stage
No.
1
2
3
4
5
6
W-Jet
Slit
Width
(cm)
0.3590
0.1988
0.1147
0.0627
0.0358
0.0288
Jet
Slit
Length
(cm)
5
5
3
3
3
2
.156
.152
.882
.844
.869
.301
S
-Jet
to Plate
Distance
(cm)
0
0
0
0
0
0
.635
.318
.239
.239
.239
.239
Reynolds
S Number
W (@14.16 1pm)
1.77
1.60
2.08
3.81
6.68
8.30
602
602
800
808
802
1348
Jet
Cumulative Frac-
Velocity tion of Impac-
(m/sec) tor Pressure Drop
(@14.16 1pm) at each Stage
1
2
5
10
17
36
.3
.3
.4
.0
.4
.9
0
0
0
0
0
1
.0
.0
.0
.154
.308
.000
-------
CO
TABLE 6
Cascade Impactor Stage Parameters
University of Washington Mark III Source Test Cascade Impactor
Stage
No.
1
2
3
4
5
6
7
No. of
Jets
1
6
12
90
110
110
90
D.-Jet
Diameter
(cm)
1.842
0.577
0.250
0.0808
0.0524
0.0333
0.0245
S-Jet
to Plate
Distance
(cm)
1.422
0.648
0.318
0.318
0.318
0.318
0.318
S
°D
.78
1.12
1.27
3.94
6.07
9.55
12.98
Reynolds
Number
1073
565
653
269
340
535
929
Cumulative Frac-
Jet tion of Impac-
Velocity tor Pressure Drop
(m/sec) at each Stage
0.9
1.5
4.1
5.2
10.2
25.4
60.0
0.0
0.0
0.0
0.019
0.057
0.189
1.000
-------
The theory of the impaction process has been developed by
several researchers1'5 to a state where the efficiency of impac-
tion can be determined as a function of the particle size (D ) ,
Reynolds Number (Re), jet diameter or width (D . ,W) , the jet to
plate distance (S) , and the jet throat length (T) .
E = E (D , Re, S/D , T/D )
It is common practice to relate the particle size D to the
square root of the Stokes number, /^ . The Stokes number as
defined by Fuchs1* is the ratio of the particle stopping distance,
Si , (the distance a particle will travel in air when given an
initial velocity, V0) to the jet diameter or width (D . or W) .
2 CPPV°
or
* p 18 y D.
C = Cunningham Slip Factor,
D. = Jet Diameter (cm),
p = Particle Density (gm/cm3),
y = Gas Viscosity (poise), and
V0 = Jet Velocity (cm/sec).
By this procedure, the square root of the Stokes number /ij7 is
used in impaction theories as a dimensionless quantity proportional
to particle size.
Cp V«
This parameter is useful in presenting impactor calibration
data because data from all stages of an impactor can be placed on
a single graph, and under many circumstances would in theory lie
along a common curve. The value of /JJ7 at 50% collection
efficiency, /41 so i defines the impaction stage Dso, the particle
size at which half the particles of that size are collected and
half are passed to the next stage. Thus, D50 is used as the
effective stage cut diameter.
-------
Recently Marple5 has been able to construct theoretical
impaction efficiency curves for several values of the jet to
plate distance, jet Reynolds Number, and jet throat length.
Figure 1 shows the results of these calculations for both round
and rectangular jet impactors. The value of the square root
of the Stokes number used by Marple, /STK , differs from that
presented in this paper, /ijT , by a factor of /2~. It can be
seen from Figure 1 that for certain ranges of Re, S/D.; S/W,
or T/S; or T/W, the magnitude of /ijTsT is sensitive to-'these
parameters. This is a possible explanation for the unpredicta-
bility of commercial impactor behavior; e.g., compare Tables 2
through 6 and Figure 1.
During the course of this investigation several types of
measurements were made. Wall losses for each impactor were
measured when sampling ammonium fluorescein aerosols. Stage
collection efficiencies for each impactor were determined for
particle sizes from 15 micrometers diameter to approximately
0.4 micrometers. When sampling ammonium fluorescein aerosols
it was possible to measure the collection efficiencies both
corrected and uncorrected for wall losses. Because of the method
used to sample polystyrene spheres, the collection efficiency
data includes wall losses in the collection efficiency of the
stage being tested.
Section 3 contains a description of the experimental pro-
cedures and the results are given in Section 4.
10
-------
100
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>-" 60
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£ 20
0
T/Dj(S/Dj=1/2)
Round
S/W(T/W=1)
— — — Rectangular
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
(a) EFFECT OF JET TO PLATE DISTANCE (Re=3,000)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
VSTK
(b) EFFECT OF JET REYNOLDS NUMBER (T/W=1)
100
B 80
W
> 60
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140
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£ 20
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S/Dj(T/Dj=1/2)
Round
— — — - Rectangular
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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
STK
(c) EFFECT OF THROAT LENGTH (Re=3,000)
Figure 1. Theoretical impactor efficiency curves for rectangular
and round impactors showing the effect of jet-to-plate
distance S, Reynolds number Re, and throat length T.5
Note that /STK = D (Cp V0/9 yD.p, whereas /ij7 =
L P P J
D (Cp Vo/18 yD ) 2.
c P J
11
-------
SECTION 2
CONCLUSIONS
Five commercially available cascade impactors have been
calibrated during this study. The method of calibration and the
presentation of the results should make this data useful to both
the field operator of these devices as well as those interested
in the theory of impactor design.
Based on this work several conclusions can be drawn.
1. The value of /ijj50 for each stage of a multiple stage
impactor may be different. Prior to the current awareness of
the importance of impactor calibration, it was the practice of
many, cascade impactor manufacturers and users to assume that the
value oE /ijj50 for every stage was identical. In many cases the
experimental value determined by Ranz and Wong1 was used.
Attempts to perform calibrations were not comprehensive. The
theories of cascade impactor operation at this time do not
describs the behavior of cascade impactors accurately enough
to make it unnecessary to calibrate each device empirically.
It is hoped that the data presented here will aid in the develop-
ment of theoretical expressions which will better predict the
behavior of cascade impactors.
2. The stage collection efficiencies are sensitive to the
type of impactor collection substrate which is used. This is
evident in the comparison of the Brink Cascade Impactor data
using glass fiber collection substrates and greased collection
plates. This strong dependence of collection efficiency on
stage collection substrate material has also been explicitly
illustrated and discussed by Willeke2 and Rao.3
3. In the majority of cases the stage collection efficiency
never reaches 100% for any particle size but reaches a maximum
value that usually falls between 80% and 95%. This implies that
some greatly oversized particles will reach every stage beyond
the first stage. Unless suitable compensation can be made for
the presence of these oversized particles, their presence will
tend to bias the apparent particle size distribution toward
higher than actual concentrations of fine particles and reduced
concentrations of large particles. These errors probably tend to
be more significant for the fine particle end of the distribution.
12
-------
4. Ideally, an impactor stage should reach 100% collection
efficiency for some particle size and stay at that value for all
larger particle sizes. In practice, however, this is not the
case as demonstrated by this study. In general the stage col-
lection efficiency reaches a maximum less than 100% and then rolls
off and decreases for particles larger than a certain size. This
is attributed to the fact that these larger particles strike the
plate with appreciable momentum, bounce, and are thus carried to
a lower stage. The use of grease on the collection plates as well
as a reduction in the impactor flowrate tends to decrease the
magnitude of this problem. The Sierra impactor data illustrate
the increase in collection efficiency which resulted from a
decrease in sampling flowrate and concomitant reduction in bounce
and cascading of large particles to lower stages. This study
shows that in some cases the maximum efficiency was almost
doubled by lowering the flowrate. A discussion of this phenom-
enon has also been presented by Rao.3
13
-------
SECTION 3
DESCRIPTION OF EXPERIMENTAL PROCEDURES
Laboratory evaluation of the cascade impactors tested
during this study involved the use of two types of particle
generation systems, a Vibrating Orifice Aerosol Generator (VOAG)
and a Pressurized Collison Nebulizer System (PCNS). The VOAG
was used to generate monodisperse ammonium fluorescein particles
with diameters from 18 micrometers to 1 micrometer. The PCNS
was used to disperse three sizes of monodisperse Dow Corning
Polystyrene Latex (PSL) spheres, 2.02 micrometers, 0.82 micro-
meter, and 0.46 micrometer diameter.
The VOAG used in this study was designed and built at
Southern Research Institute, although similar devices have been
reported by several authors previously6'7'8, and a commercial
unit is. available from Thermo Systems, Inc.*
figure 2 is a schematic diagram showing the operating
principle of the VOAG. A solution of known concentration (in our
case, c. solution of fluorescein (C.20H1205) in 0.1N NHi,OH is
forced through a small orifice (5, 10, 15, or 20 \im diameter).
The orifice is attached to a piezoelectric ceramic which, under
electrical stimulation, will vibrate at a known frequency. This
vibration imposes periodic perturbations on the liquid jet
causinc- it to break up into uniformly-sized droplets. Knowing
the licuid flow rate and the perturbation frequency, the droplet
size ca.n be readily calculated. The solvent evaporates from the
droplets leaving the non-volatile solute as a spherical residue.
The final dry particle size can be calculated from the droplet
size through the known concentration of the liquid solution.
To calculate the dry particle size, the expression
1/3
dp = is USed'
*Thermo Systems, Inc., 2500 N. Cleveland, St. Paul, Minn. 55113
14
-------
Plexiglass Drying
Chamber
Vibrating
Orifice
Flow
Meters
Control
Valves
Charge Neutralizer
Signal Generator
Membrane
Filter
Syringe
Pump
Dry Air
Figure 2. Schematic representation of the Vibrating Orifice
Aerosol Generator.
15
-------
volume of solute
where C is the solution concentration or
volume of solution '
Q is the solution flow rate (cm3/min), and
F is the perturbation frequency (Hz).
By the use of smaller orifices, one can obtain much higher
operating frequencies. This in turn yields higher particle number
concentrations and allows a shorter running time to collect the
same maiss per stage. The running time must be sufficiently
long, however, to allow accurate determination of the stage
collect.ion efficiencies and wall losses. It was our experience
that the 20 ym orifice was consistently easier to use in
particle generation, primarily because of fewer clogging
problems.
Erior to particle generation the orifices were washed in
detergent with ultrasonic agitation and then rinsed several
times in distilled water, also with ultrasonic agitation. After
the filter and liquid handling system was flushed several times
with the aerosol solution to be used, an orifice was placed,
still wet with distilled water, or blown dry, into the crystal
holder and the syringe pump turned on. A jet of air was played
over the orifice to keep the surface clean until enough pressure
was built up behind the orifice to form a jet.
After a stream of particles was generated, a determination
of monodispersity had to be made. Two methods were used to
accomplish this. By using a small, well-defined air jet to
deflect the stream of particles, it was possible to tell when
the aerosol was mono or polydisperse. Depending on particle
size, the stream was deflected by the air at different angles, and
if the aerosol was polydisperse, several streams could be seen
at one time. By varying the crystal oscillation frequency, the
system could be fine-tuned to give only a single deflected
particls stream, thus indicating monodispersity. On several
occasions, the aerosol tended to drift from monodispersity. To
protect against this occurrence, periodic filter samples were
taken and checked by optical microscopy. This also provided a
good check on the sphericity of the aerosol because the final
particles were investigated instead of the primary liquid
droplets. The microscopy thus served as a check on proper
drying, satellites, correct size, and multiplets. Polonium 210
alpha particle sources were placed near the air stream as charge
neutralizers to reduce agglomeration and loss of particles due
to electrostatic forces. A three-foot-high plexiglass cylinder
was placed on the generator and dispersion and dilution air
turned on to disperse, dilute and loft the particles into a
plenum with Several sampling ports. During each test, filter
samples were drawn at intervals to insure continued monodis-
persity., Because of its nonhygroscopicity and physical9
16
-------
properties, ammonium fluorescein was used throughout these
studies as the test aerosol, although in theory, any material
that will dissolve readily in an evaporable solvent could be
used. Figure 3 shows one of the test aerosols generated with
the VOAG. In general, it was found that about 4% to 8% by mass
of the particles were of twice the volume (1.26 X diameter) of
the primary particles. Solvent impurities limited the smallest
size which could be generated with the VOAG using ammonium
fluorescein to approximately 1 micrometer diameter. Thus
optical microscopy was used as a secondary validation of
particle size.
When it had been determined that particles of the correct
size were being generated, each cascade impactor was allowed to
sample from the plenum for the required length of time to collect
a suitable sample. Nonisokinetic sampling was performed; how-
ever, it was determined by a series of tests that this did not
affect the collection efficiency of the impactor stages as com-
pared to isokinetic sampling results. It is likely that the
nozzle losses were influenced however.
Several impactors tested are normally used with a greased
substrate material on the collection plates. After several
trials usina Dow Corning High Vacuum Silicone Grease, Agar, K-Y
Jelly, and Vaseline*, it was "found that Vaseline was the most
convenient material to use as a substrate medium for this study
because it goes easily into solution in a small amount of benzene
permitting easy separation of the particles from the substrate
coating.
In all cases, a back-up filter was used to collect material
not caught by the last impaction stage of each device. This allowed
the calculation of the collection efficiency of all stages tested.
A pump and flow-metering device for each impactor insured
repeatability in flow rate during each test. After several
tests, it was determined that the Brink with bare plates did not
perform satisfactorily due to severe particle bounce and reen-
trainment. Accordingly, testing of the Brink with bare plates
was discontinued after sufficient data was taken to prove the
unreliability of that configuration as a sizing device. Sub-
sequently, only glass fiber substrates and greased plates were
used with the Brink impactor.
At the conclusion of the sampling period, each impactor
was carefully disassembled and all internal surfaces cleaned
with a solution of 0.IN NH^OH. Using a known amount of the
solution, each plate and surface was washed to dissolve and
rinse off the ammonium fluorescein particles. Where Vaseline
was used, a small amount of benzene was poured over the greased
collection plate in a small dish which was then placed in an
ultrasonic cleaner. A small amount of agitation caused the
*Cheesborough-Pond's Inc. N.Y., N.Y. 10017
17
-------
c
f
• «e
I
f
Figure 3. Ammonium fluorescein aerosol particles generated
using the Vibrating Orifice Aerosol Generator.
18
-------
Vaseline to dissolve and the ammonium fluorescein particles to
become well mixed. Adding a known amount of 0 . IN NHijOH to the
mixture with stirring caused the ammonium fluorescein to dissolve,
After the benzene mixture floated to the top of the NtUOH, the
ammonium fluorescein solution was pipetted off.
The quantity of material on each surface was determined by
absorption spectroscopy. Initially a Beckman Quartz Spectro-
photometer, Model DU, and later a Bausch and Lomb Spectronic 88
Spectrophotometer, calibrated with solutions of known concen-
tration of ammonium fluorescein, were used to measure the con-
centration of ammonium fluorescein in each wash. From knowledge
of the amount of wash solution, the dilution factor, if any, and
the absolute concentration, the mass of particles on each surface
could be calculated. With the mass on each plate and surface
known, the wall losses and stage collection efficiencies could
be calculated.
A Pressurized Collison Nebulizer System similar to that
reported by Calvert10 was assembled as shown in Figure 4. A
stream of dry dilution air is mixed with the nebulized suspension
to reduce the aerosol concentration and to aid in drying. Valves
placed upstream of the impactor allow variations in the flowrate.
Three sizes of PSL particles were used (2.02 ym, 0.82 ym, and
0.46 micrometers diameter). Each impactor stage was tested at
three flowrates near the nominal or designed impactor flowrate.
Thus nine calibration points were obtained for each stage of each
impactor. A Climet Instruments Model 208A Particle Analyzer was
used to monitor the impactor inlet and outlet concentrations.
Stages of each impactor were tested individually. This system
was designed to allow two different air flow strategies depending
on whether the impactor flowrate was higher or lower than the
Climet inlet flowrate. Because of the limited availability of
large PSL spheres, and because these data were supplementary to
the ammonium fluorescein data, only the impactor stages for which
information could be obtained with sizes of 2 micrometers
diameter and smaller were tested. Generally these were the lower
3 or 4 impactor stages. For simplicity and convenience, mass
flowmeters were used to measure the critical gas flowrates.
19
-------
PRESSURE GAUGE
fO
O
UIFI-USIONAL DRYER
MASS FLOW METER
THREE-WAY VALVE
BLEED VALVE
&VALVE A
VALVE B
/
-------
SECTION 4
RESULTS OF THE CALIBRATION STUDY
WALL LOSSES
During the portion of the calibration procedure using
ammonium fluorescein aerosols, data on wall losses were tabu-
lated. By washing each cascade impactor surface after sampling
a test aerosol, it was possible to obtain information on
particle losses occurring in nozzles, inlet cones, jet plates,
and other internal surfaces. These losses were calculated as
percentages of the total amount of aerosol entering the
impactor. Three types of wall losses were quantified: those
occurring in the nozzles alone (Nozzle Wall Loss), those
occurring in the inlet cone alone, where applicable (Inlet
Cone Wall Loss), and those occurring in the nozzle, inlet cone,
and other internal surfaces other than the collection substrates
(Total Wall Loss).
The wall loss data are shown in Figures 5 through 11 for
the seven impactor configurations tested as Percentage Wall
Loss Versus Particle Diameter. Except for Figure 10, all wall
loss data are based on the results of non-isokinetic sampling.
The degree to which non-isokinetic sampling influenced the
Nozzle Wall Loss is unknown.
In general, wall losses tend to decrease with particle size
and are negligible for particles smaller than about 1-2 micro-
meters in diameter. The majority of the losses occur in the
nozzles and inlet cones.
Wall losses can be attributed to particle settling, dif-
fusion, electrostatic attraction, bounce, and reentrainment.
Visual inspection of the nozzles and inlet cones indicate that
the losses were predominantly due to settling. All impactors
except the Brink were run in a horizontal position.
21
-------
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PARTICLE DIAMETER^ MICROMETERS
Figure 5. Impactor wall loss versus particle size. Andersen Mark III Stack
Sampler. (14 LPM, 22°C, 29.5"Hg, 1.35 gin/cm3) Nonisokinetic
sampling. Total wall loss - • Nozzle v>all loss - • inlet cone
wall loss - A
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Figure 6. Impactor wall loss versus particle size. Modified Brink Model
BMS-11 Cascade Impactor (Glass Fiber Substrates). (0.85 LPM,
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PARTICLE DIAMETER/ MICROMETERS
Impactor wall loss versus particle size. Modified Brink Model
BMS-11 Cascade Impactor ((Greased Collection Plates). (0.85 LPM,
22°C, 29.5"Hg, 1.35 gin/cm3) Nonisokinetic sampling. Total wall
loss - • Nozzle wall loss - •
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Figure 8. Impactor wall loss versus particle size. MRI Model 1502 Inertial
Cascade Impactor. (14 LPM, 22°C, 29.5"Hg, 1.35 gm/cm3) Noniso-
kinetic sampling. Total wall loss - • N6zzle wall loss - •
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Figure 9. Impactor wall loss versus particle size. Sierra Model 226
Source Cascade Impactor. (14 LPM, 22°C, 29.5"Hg, 1.35 gm/cm3)
Nonisokinetic sampling. Total wall loss -• No2zle wall loss
Uilet cone wall loss - A
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PARTICLE DIAMETER, MICROMETERS
Impactor wall loss versus particle size. Sierra Model 226
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Isokinetic sampling. Total wall loss - • Nozzle wall loss -
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Figure 11. Impactor wall loss versus particle size. University of Washington
Mark III Source Test Cascade Impactor. (14 LPM, 22°C, 29.5"Hg,
1.35 gin/cm3) Wonisokinetic sampling. Total wall loss -•
Nozzle wall.loss - •
-------
CALIBRATION DATA - EFFICIENCY VS. Sfy
Recall from the Introduction that if two or more impactor
stages have the same Reynolds Number, jet to plate spacing, and
jet throat length, then according to theory they should have the
same particle collection efficiency for the same magnitude of
the square root of the Stokes parameter. If these physical
parameters differ, or if different collection substrate media
are used, then these curves may not be identical. These
differences are evident in Figures 12 through 26, which present
in alphabetical order the Stage Collection Efficiency Versus /ijj"
for each cascade impactor configuration. These efficiencies
are based solely on the particles actually collected by an
impaction surface and those found downstream of that surface.
Particles on other surfaces such as the jet plate above the
impaction surface were not included in the efficiency shown
in these figures. These same impactor calibration data are
shown, calculated on a different basis, in Figures 27 through
41. In these figures the ammonium fluorescein data have been
corrected to include wall losses as follows:
The true collection efficiency is defined as the amount of
material collected by an impaction stage divided by the amount of
material incident on that stage. If material collected in jet
nozzles, inlet cones, and jet stage surfaces is combined with
the appropriate stage catch, the resulting collection efficiency
is not a true collection efficiency as defined above. These
"Corrected for Wall Loss" Stage Collection Efficiencies are
useful in analyzing results from field tests where particulate
collected on surfaces other than the impaction substrates is
combined with the regular stage catches. For instance, the
material collected in the nozzle, inlet cone, and 1st Jet Stage
of the Andersen Mark III would be combined with the mass on the
1st Collection Substrate in order to obtain a total mass which
would be presumed to have been caught on this collection sub-
strate, if these wall losses had not occurred. Also, material
on any lower jet stage would be combined with the appropriate
collection substrate catch. Collection Efficiencies corrected
in this way to include wall losses generally have higher magni-
tudes at all sizes.
The differences in /^50 for the different impactor stages
shown in the foregoing figures require that empirical cali-
brations be done. No existing theory is comprehensive enough
to compensate for the variations in geometry and application
techniques for single devices, among different devices, or among
different users.
29
-------
A difference can also be seen between the shapes of the
empirical calibration curves and the curves predicted by Marple's
theory,, The empirical curves show a smooth tail which approaches
zero for small values of t/jj7. Marple's theory, however, predicts
a sharp intersection between the efficiency curves and the
abscissa. The "tails" are possibly due, at least in part, to the
fact that the calibration aerosols cannot be made perfectly mono-
disperse, and always contain multiplets.11 Such "tails" are
probably unavoidable when using the VOAG, because these devices,
at best, produce about 4% doublets at all times.
The graphs also indicate a more severe problem, common to
all cascade impactors. On a majority of the stages the collection
efficiency does not reach 100% at any value as would be expected
theoretically. Also after reaching a maximum point, the curves
fall off to lower efficiencies at higher /ijT values. This means
that some large particles will not be collected on upper stages
and will be passed through the impactor to lower stages or even
the back-up filter. An accurate knowledge of this type of
behavior is essential to the proper design and application of
cascade impactors.
The theoretical data of Marple5 shown in Figure 1 indicates
shifts in the square root of the Stokes Number, ^, which depend
upon the jet to plate spacing ratio (S/D.) and the Reynolds
Number (Re) . The values of Sty corresponding to a given particle
collection efficiency increase for increasing Jet to Plate
Spacing ratio and decrease for increasing Reynolds Number.
Comparison of the values of these parameters as given in Tables
2 through 6 indicates that one would expect the Andersen Mark III
behavior to be affected by these parameter variations to a
greater extent than some of the other cascade impactors.
For the Andersen Mark III the values of the jet to plate
spacing ratio change from about 1.5 to 10 between Stage 1 and 8.
Theoretically this should cause the ffy curve to shift to larger
values and become much steeper. The Reynolds Number changes
from about 45 to 500 between stages 1 and 8. Theoretically this
should cause a shift to the left in the /ijj" values as well as
causing them to be steeper.
Although it is difficult to pinpoint the exact cause for
the shifts in the Andersen data shown in Figures 12, 13, 14, 27,
28, and 29, the general shift to smaller /ij7 values and the corre-
sponding increase in steepness could be due, in part, to a combi-
nation of these effects due to jet to plate spacing ratio and
Reynolds Number.
The values of these parameters for the other impactors in-
dicate that the effects would be much more difficult to separate
and characterize because of the smaller changes in these values.
30
-------
In Table 7 are presented the values of the square root of
the Stokes number, at 50% Collection Efficiency, vAJJ50 for all
impactor stages tested, both corrected and uncorrected for wall
losses.
CALIBRATION DATA - EFFICIENCY VS. PARTICLE SIZE
The data presented in the previous section are shown in
this section as Collection Efficiency Versus Particle Size.
Figures 42 through 48 show these data uncorrected for wall losses
while Figures 49 through 55 show the data corrected for wall
losses. The same features of non-ideal impactor behavior dis-
cussed above are also evident in these graphs.
In Table 8 are presented the values of the particle diam-
eter at 50% Collection Efficiency, D so, for all impactor stages
tested, both corrected and uncorrected for wall losses when
operated at the conditions stated in Table 1 with unit density
particles.
31
-------
OJ
ro
100
90
80
70
>-
o
S 60
LJ
50
~ 40
o
o
30
20
10
0
0
1 I T
i I
I I I I I
I I I I I
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1.2 1,3 1.4 1.5 1,6 1.7 1.8 1,9
Figure 12. Collection efficiency (%) Versus /iJ7
Andersen Mark III Stack Sampler
Stage 1 - Stage 2
Uncorrected for Wall Losses
-------
UJ
OJ
100
90
80
" 7°
o
3 60
o
UJ
z
o
50
J^
~ 401—
30
20
10
0
Af
1 I I T
i I i r
I I I I I I I I I
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1.6 1,7 1,8 1,9
Figure 13. Collection Efficiency {%) Versus
Andersen Mark III Stack Sampler
Stage 3 - Stage 5
Uncorrected for Wall Losses
-------
oo
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0.8 0,9 1.0 1,1 1,2 1.3 1,4 1,5 1.6 1.7 1,8 1.9
Figure 14. Collection Efficiency (%) Versus /ij7
Andersen Mark III Stack Sampler
Stage 6 - Stage 8
Uncorrected for Wall Losses
-------
U)
U1
100
90
80
~ 7°
o
I 60
o
III 3\*
40
30
20
10
o
I I I I I I
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0.8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1.6 1.7 1,8 1,9
Figure 15. Collection Efficiency (%) Versus /i]7
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Glass Fiber Substrates)
Uncorrected for Wall Losses
-------
CO
(Ti
0,1 0,2 0,3 0.4 0,5 0,6 0,7 0,8 0,9 1.0 1,1 1.2 1,3 1.4 1,5 1,6 1,7 1,8 1,9
Figure 16. Collection Efficiency {%) Versus /ijT
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Glass Fiber Substrates)
Uncorrected for Wall Losses
-------
U)
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1.1 1,2 1,3 1,4 1.5 1.6 1,7 1,8 1,9
Figure 17. Collection Efficiency {%) Versus /iJT
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Greased Collection
Plates)
Uncorrected for Wall Losses
-------
00
0.1 0,2 0,3 0,4 0.5 0,6 0.7 0,8 0.9 1,0 1.1 1,2 1.3 1,4 1,5 1,6 1,7 1,8 1,9
Figure 18. Collection Efficiency (%) Versus /ij»
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Greased Collection
Plates)
Uncorrected for Wall Losses
-------
vo
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5.1.6 1,7 1,8 1,9
/ijT
Figure 19. Collection Efficiency (%) Versus /ij7
MRI Model 1502 Inertial Cascade Impactor
Stage 1 - Stage 4
Uncorrected for Wall Losses
-------
0,1 0,2 0.3 0,4 0.5 0,6 0.7 0,8 0.9 1.0 1.1 1.2 1,3 1,4 1,5 1.6 1,7 1,8 1,9
Figure 20. Collection Efficiency (%) Versus /ijT
MRI Model 1502 Inertial Cascade Impactor
Stage 5 - Stage 7
Uncorrected for Wall Losses
-------
100
90
80
1 I I I I I I T
I I I I I I
I I I
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1.7 1,8 1,9
/JT
Figure 21. Collection Efficiency (%) Versus /JjT
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 14 LPM
Uncorrected for Wall Losses
-------
100
90
80
^ 70
o
2 60
o
UJ -^l
to u«
O
u
40
O
30
20
10
0
0
I
0,1 0,2 0,3 0,4 0,5 0,6 QJ 0,8 0.9 1,0 1,1 1.2 1.3 1.4 1.5 1.6 U 1.8 1.9
Figure 22. Collection Efficiency (%) Versus /ij>
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 14 LPM
Uncorrected for Wall Losses
-------
100
90
80
70
V
o
S 60
o
in -JL
o
i-^
t-
&• «J
U> Ul
o
o
30 —
20
10
I I I I I i I I I I I I
o
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1.9
Figure 23. Collection Efficiency (%) Versus /ijT
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 7 LPM
Uncorrected for Wall Losses
-------
100
90
80
70
>-
o
S 60
u
I—I
ih 50
p 40
u
UJ
30
o
u
10
0
0
1 I f
20 —
I I I I I I I I I I I I I I I I
0,1 0,2 0,3 0,4 0,5 0,6 0.7 0,8 0.9 1,0 1.1 1,2 1.3 1,4 1,5 1,6 1.7 1.8 1.9
Figure 24. Collection Efficiency (%) Versus /ty
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 7 LPM
Uncorrected for Wall Losses
-------
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1.6 1,7 1,8 1,9
Figure 25. Collection Efficiency {%) Versus /i]7
University of Washington Mark III Cascade Impactor
Stage 1 - Stage 4
Uncorrected for Wall Losses
-------
100
90
80
*! 70
>-
o
§ 60
o
4-
c 40
o
o
30
20
10
0
i i r
I I I I 1 J L I I I I I
0 0,1 0,2 0,3 0,4 0,5 0.6 0,7 0,8 0,9 1,0 1.1 1,2 1.3 1,4 1.5 1,6 1.7 1.8 1,9
Figure 26. Collection Efficiency (%) Versus /ij7
University of Washington Mark III Cascade Impactor
Stage 5 - Stage 7
Uncorrected for Wall Losses
-------
100
90
80
70
>-
u
S 60
u
£ 50
in •'«»
5 w
UJ
30
o
u
20
10
0
0
I I I I I I I I I I I I I I
0,1 0,2 0,3 0,4 0,5 0.6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 l.H 1,5 1,6 1.7 1,8 1,9
Figure 27. Collection Efficiency (%) Versus
Andersen Mark III Stack Sampler
Stage 1 - Stage 2
Corrected for Wall Losses
-------
100r
oo
I i r
i i i i i r
90 —
i r
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1.0 1,1 1,2 1,3 1,4 1,5 1.6 1,7 1,8 1.9
Figure 28. Collection Efficiency (%) Versus /ij7
Andersen Mark III Stack Sampler
Stage 3 - Stage 5
Corrected for Wall Losses
-------
VO
100
90
80
70
>-
o
B 60
u
t 50
ni -'U
g 40
U
O
u
30
20
10
0
i i i r
I I i I I
I I I I I I I I I
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9
Figure 29. Collection Efficiency (%) Versus
Andersen Mark III Stack Sampler
Stage 6 - Stage 8
Corrected for Wall Losses
-------
Ul
o
0 0,1 0,2 0,3 0,4 0,5 0,6 0.7 0,8 0,9 1,0 1,1 1,2 1,3 1.4 1,5 1,6 1.7 1,8 1.9
Figure 30. Collection Efficiency (%) Versus S\j>
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Glass Fiber Substrates)
Corrected for Wall Losses
-------
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1.6 1.7 1.8 1,9
Figure 31. Collection Efficiency (%) Versus /ij7
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Glass Fiber Substrates)
Corrected for Wall Losses
-------
Ul
0 0,1 0,2 0,3 0,4 0.5 0,6 0,7 0,8 0.9 1.0 1.1 1,2 1,3 1.4 1,5 1.6 1,7 1.8 1.9
Figure 32. Collection Efficiency (%) Versus /ty
Modified Brink BMS-11 Cascade Impactor
Stage 0 - Stage 3 (Greased Collection
Plates)
Corrected for Wall Losses
-------
en
I I I I I I
I I I I I
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1.7 1,8 1,9
Figure 33. Collection Efficiency (%) Versus Sty
Modified Brink BMS-11 Cascade Impactor
Stage 4 - Stage 6 (Greased Collection
Plates)
Corrected for Wall Losses
-------
100r
Ui
I I I f
i i i i r
I I I I l
I I I
l I I I
0,1 0.2 0,3 0,4 0,5 0.6 0,7 0.8 0,9 1.0 1,1 1,2 .1,3 1.4 1,5 1,6 1.7 1,8 1,9
Figure 34. Collection Efficiency (%) Versus /ijT
MRI Model 1502 Inertial Cascade Impactor
Stage 1 - Stage 3
Corrected for Wall Losses
-------
tn
en
I I I I I I I I I I I I I I I
0.1 0.2 0.3 0.4 0.5 0.6 0,7 0.8 0.9 1.0 1.1 1.2 1.3 1.1 1.5 1.6 1.7 1.8 1.9
Figure 35. Collection Efficiency (%) Versus /ij7
MRI Model 1502 Inertial Cascade Impactor
Stage 4 - Stage 7
Corrected for Wall Losses
-------
01
(Tl
100
90
80
~ 7°
o
S 60
o
£ 50
o
E 40 —
O
UJ
O
CJ
30
20
1C
0
0
1 i ! !
i—i—r
I I
F j 1 r
i i i i i
i i i i j i j L i j
I I I I
0,1 0,2 0,3 0,4 0,5 0,6 0.7 0,8 0,9 1,0 1,1 1.2 1.3 1.4 1,5 1.6 1.7 1.8 1,9
Figure 36. Collection Efficiency (%) Versus /ijT
Sierra Model 226 Inertial Cascade Impactor
Stage 1 - Stage 3 Flowrate = 14 LPM
Corrected for Wall Losses
-------
i i j i i i i i 1 i i i i i i
0.1 0,2 0.3 0.1 0.5 0.6 0.7 0.8 0.9 1.0 1,1 1.2 1.3 1.1 1.5 1.6 1,7 1.8 1.9
Figure 37. Collection Efficiency (%) Versus /ij7
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 14 LPM
Corrected for Wall Losses
-------
100
90
80
*t 70
o
£ 60
m -H
2 HO
CO HI
o
u
30
20 —
10
1 I I 1 I I I
• i
I I I i 1 I I I J l_L
0 0.1 0,2 0.3 0,4 0.5 0,6 0.7 0.8 0.9 1,0 1.1 1,2 1.3 1,4 1.5 1.6 1.7 1.8 1,9
Figure 38. Collection Efficiency (%) Versus /ij7
Sierra Model 226 Inertial Cascade Irnpactor
Stage 1 - Stage 3 Flowrate = 7 LPM
Corrected for Wall Losses
-------
100
90
80
70
£ 60
o
t 50
in •'«/
c 40
VO UJ
o
u
30
20
1C
0
1 I I I I
i i i i i i i r
I I I I I I I I I I I I I I I I
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1.1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9
Figure 39. Collection Efficiency (%) Versus /ij7
Sierra Model 226 Inertial Cascade Impactor
Stage 4 - Stage 6 Flowrate = 7 LPM
Corrected for Wall Losses
-------
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1.1 1.2 1,3 1,4 1,5 1.6 1.7 1.8 1.9
Figure 40. Collection Efficiency (%) Versus /ty
University of Washington Mark III Cascade Impactor
Stage 1 - Stage 4
Corrected for Wall Losses
-------
i I I i r
I I I I I I I I I I L I _L I I I
0 0.1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1.4 1,5 1,6 1,7 1,8 1,9
Figure 41. Collection Efficiency (%) Versus /ijT
University of Washington Mark III Cascade Impactor
Stage 5 - Stage 7
Corrected for Wall Losses
-------
t>o
.
O
u
O
Ul
O
O
100
90
80
70
60
50
40
30
20
10
1 I II I I I
1 I I I I I I I
.3 .4 .5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
Figure 42. Collection Efficiency (%) Versus Particle Size
Andersen Mark III Stack Sampler (Stage 1 -
Stage 8) Uncorrected for Wall Losses
(14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
20
-------
100
OJ
O
z
LU
O
LU
z
O
O
O
u
I I I I I I
.4
.5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
20
Figure 43. Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Glass Fiber Substrates) (Stage 0 - Stage 6)
Uncorrected for Wall Losses
(0.85 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
-------
O
z
UJ
O
LL
LL
UJ
z
O
O
ui
O
O
.4
.5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
20
Figure 44. Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Greased Collection Plates) (Stage 0 - Stage 6)
Uncorrected for Wall Losses
(0.85 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
-------
100
CTi
Ul
o
z
UJ
o
LL
O
LU
O
O
10
.3 .4
.5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
Figure 45
Collection Efficiency (%) Versus Particle Size
MRI Model 1502 Inertial Cascade Impactor
(Stage 1 - Stage 7)
Uncorrected for Wall Losses
(14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
-------
100
a?
»,
o
UJ
O
UJ
O
O
UJ
O
o
Figure 46.
PARTICLE DIAMETER, MICROMETERS
Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
(Stage 1 - Stage 6)
Uncorrected for Wall Losses
-------
(Tl
o
z
UJ
o
u.
u.
LU
o
o
UJ
o
o
I I I I I I I I
.4
.5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
20
Figure 47. Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(7 LPM. 22°C., 29.5"Hg, 1.00 gm/cm3)
(Stage 1 - Stage 6)
Uncorrected for Wall Losses
-------
CO
o
LU
U
111
O
U
U4
O
U
100
on
I I I I I I
Figure 48.
PARTICLE DIAMETER, MICROMETERS
Collection Efficiency (%) Versus Particle Size
University of Washington Mark III Cascade
Impactor (14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
(Stage 1 - Stage 7)
Uncorrected for Wall Losses
-------
(Ti
VD
u
z
UJ
o
LL
U.
UJ
O
UJ
O
O
.4
.5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
20
Figure 49. Collection Efficiency (%) Versus Particle Size
Andersen Mark III Stack Sampler (Stage 1 -
Stage 8)
Corrected for Wall Losses
(14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
-------
100
o
o
u_
u.
Ul
Z
O
o
I I I I II I
.4 .5 .6 .7 .8 .9 1.0 2 3 456789 10
PARTICLE DIAMETER, MICROMETERS
Figure 50. Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Glass Fiber Substrates) (Stage 0 - Stage 6)
Corrected for Wall Losses
(0.85 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
20
-------
o
z
UJ
O
u.
LL
Ul
O
UJ
O
U
Figure 51.
PARTICLE DIAMETER, MICROMETERS
Collection Efficiency (%) Versus Particle Size
Modified Brink BMS-11 Cascade Impactor
(Greased Collection Plates) (Stage 0 - Stage 6)
Corrected for Wall Losses
(0.85 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
-------
o
z
UJ
O
UJ
Z
O
o
UJ
O
O
I I I I III
Figure 52.
PARTICLE DIAMETER, MICROMETERS
Collection Efficiency (%) Versus Particle Size
MRI Model 1502 Inertial Cascade Impactor
(Stage 1 - Stage 7) Corrected for Wall Losses
(14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
-------
100
U)
o
z
—
o
z
O
LU
O
O
PARTICLE DIAMETER, MICROMETERS
Figure 53. Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(14 LPM, 22°C, 19.5"Hg, 1.00 gm/cm3) (Stage 1 -
Stage 6)
Corrected for Wall Losses
-------
O
z
If!
o
z
g
u
Ul
O
U
I I I I I I I
Figure 54.
PARTICLE DIAMETER, MICROMETERS
Collection Efficiency (%) Versus Particle Size
Sierra Model 226 Source Cascade Impactor
(7 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3) (Stage 1 -
Stage 6) Corrected for Wall Losses
-------
100
Ul
o
z
ui
ui
Z
o
u
o
a
I I I I I I II
Figure 55.
PARTICLE DIAMETER, MICROMETERS
Collection Efficiency (%) Versus Particle Size
University of Washington Mark III Cascade
Impactor (14 LPM, 22°C, 29.5"Hg, 1.00 gm/cm3)
(Stage 1 - Stage 7) Corrected for Wall Losses
-------
TABLE 7
Square Root of the Stokes Number at 50% Collection Efficiency, /ij>s 0
Oncorrecteci for wall Losses
Stage
Andersen
Brink (Glass Fiber)
Brink (Grease)
MRI
Sierra (14 LPM)
Sierra (7 LPM)
U. of W.
Stage
Andersen
Brink (Glass Fiber)
Brink (Grease)
MR!
Sierra (14 LPM)
Sierra (7 LPM)
U. of W.
0 1
.41
.31 .28
.31 .35
.
.44
.42
.17
Corrected
0 1
.31
.30 .32
.32 .35
.11
.33
.33
.12
2
.43
.27
.38
.27
.47
.47
.32
for Wall
2
.43
.27
.38
.25
.42
.48
.31
3
.41
.38
.24
.34
-
.36
.33
Losses
3
.41
.29
.34
.35
.65
.36
.29
4
.39
.37
.29
.32
.49
.44
.27
4
.39
.38
.26
.34
.49
.40
.27
5
.34
.40
.32
.33
.49
.46
.38
5
.33
.41
.33
.29
.42
.47
.37
6
.32
.27
.26
.35
.37
.44
.33
6
.32
.27
.27
.35
.43
.47
.35
7 8
.34 .29
.38
-
7 8
.33 .28
.40
.30
-------
TABLE 8
Particle Diameter (Micrometer) at 50% Collection Efficiency, D so
for the Conditions Stated in Table 1 p
Uncorrected for Wall Losses
Stage 0123
Andersen
Brink (Glass Fiber)
Brink (Grease)
MRI
Sierra (14 LPM)
Sierra (7 LPM)
U. of W.
Andersen
Brink (Glass Fiber)
Brink (Grease)
MRI
Sierra (14 LPM)
Sierra (7 LPM)
U. of W.
14.0
9.7 4.3
9.3 5.8
-
17.0
18.0
14.0
Corrected
Stage 0 1
10.5
9.7 4.7
9.3 5.4
9.1
9.8
14.5
10.5
10.4
2.45
3.7
11.0
8.2
11.0
11.2
for Wall
2
9.4
2.80
3.7
9.2
7.0
12.0
10.0
6.1
2.00
2.30
4.7
-
4.4
4.1
Losses
3
5.8
2.10
2.35
4.9
5.0
4.2
4.4
4.0
1.05
1.05
2.20
2.30
2.65
1.86
4
4.4
1.05
1.10
2.10
2.20
2.55
1.86
2.35
.76
.78
1.25
1.00
1.70
1.57
5
2.20
.75
.76
1.10
1.10
1.65
1.60
1.20 .76 .46
.43
.46
.31 .50
.67
.95
.67
678
1.20 .70 .43
.44
.46
.69 .52
.60
.95
.66 .30
-------
REFERENCES
1. Ra:.iz, W.D., and J. B. Wong. Impaction of Dust and Smoke
Particles, Ind. and En'g. Chem., 50, No. 4 (April, 1958).
2. Wi.Lleke, K. Performance of the Slotted Impactor. Am. Ind.
Hygiene Assoc. J., 683-691, September, 1975.
3. Rao, A. K. Sampling and Analysis of Atmospheric Aerosols.
Particle Tech. Lab. Publ. No. 269, Department of Mechanics
Engineering; University of Minnesota, Minneapolis, Minnesota
55455, June 1975.
4. Fuohs, N. A. (1964) The Mechanics of Aerosols, Pergamon
Pruss, New York.
5. Marple, V. A. A Fundamental Study of Inertial Impactors.
Ph,,D. Thesis, Mechanical Engineering Department, University
of Minnesota, Minneapolis, Minnesota 55455, 1970.
6. Berglund, R. N., and B.Y.H. Liu. Generation of Monodisperse
Aerosol Standards. Environmental Science and Technology,
Vol. 6, No. 2, 1973.
7. Lindblad, N. R., and J. M. Schneider. Production of Uniform-
Sized Liquid Droplets. J. Sci. Instru., Vol. 42, 1965.
8. Strom, L. The Generation of Monodisperse Aerosols by Means
of a Disintegrated Jet of Liquid. Rev. Sci. Instr., Vol. 40,
No. 6, 1969.
9. Stober, W., and H. Flachsbart. An Evaluation of Ammonium
Fluorescein as a Laboratory Aerosol. Atmos. Environ. Vol. 7,
1973.
10. Calvert, S. Cascade Impactor Calibration Guidelines.
EPA-600/2-76-118, U. S. Environmental Protection Agency,
Research Triangle Park, N.C., 1976.
11. Jaericke, R., and I. H. Blifford. The Influence of Aerosol
Characteristics on the Calibration of Impactors. Journal
of Aerosol Science, 5(5) :457-464, 1974.
78
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TECHNICAL REPORT DATA
(flease read Initructioiis on the reverse before completing)
1. REPORT NO.
EPA-600/2-76-280
3. RECIPIENT'S ACCESSION NO.
4. TITLE ANDSUBTITLE
Particulate Sizing Techniques for Control Device
Evaluation: Cascade Impactor Calibrations
5. REPORT DATE
October 1976
6. PERFORMING ORGANIZATION CODE
SORI-EAS-76-653
7. AUTHOR(S)
Kenneth M. Gushing, George E. Lacey,
Joseph D. McCain, and Wallace B. Smith
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
10. PROGRAM ELEMENT NO.
1AB012; ROAP 21ADM-011
11. CONTRACT/GRANT NO.
68-02-0273
12. SPONSORING AGENCY NAME AND ADDRESS
EPA. Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 3/73-7/76
14. SPONSORING AGENCY CODE
EPA-ORD
^.SUPPLEMENTARY NOTESIERL-RTP project officer for this report is D. B. Harris, 919/549-
8411 Ext 2557, Mail Drop 62. EPA-650/2-74-102a was previous report in this series.
16. ABSTRACTTne repOrt gjves results of o. calibration study to determine sizing parame-
ters and wall losses for five commercially available cascade impactors. A vibrating -
orifice aerosol generator was used to produce monodisperse ammonium fluorescein
aerosol particles 15 to 1 micrometers in diameter. A pressurized Collison Nebulizer
system was used to disperse Dow Corning polystyrene latex (PSL) spheres 2 to 0.46
millimeters in diameter. When ammonium fluorescein was used, the mass collected
by each impactor surface was determined using absorption spectrophotometry of
washes from the various surfaces. When sizing with the PSL spheres, a Climet Instr-
uments Model 208A Particle Analyzer was used to determine particle number concen-
trations at the inlet and the outlet of the test impactor. Results are reported showing
stage collection efficiency as a function of the square root of the Stokes number,
stage collection efficiency as a function of particle size, and impactor wall losses
(total, nozzle, and inlet cone) as a function of particle size. It has been determined
that the values of the Stokes number for the 50% collection efficiency are not gener-
ally the same for each impactor stage. A table of these values is presented. Publish-
ed theories do not successfully predict these values, so empirical calibration is
required before these devices can be used accurately in the field or laboratory.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Croup
Air Pollution
Aerosols
Dust
Measurement
Calibrating
Impactors
Stokes Law (Fluid
Mechanics)
Air Pollution Control
Stationary Sources
Particulates
Cascade Impactors
13B
07D
11G
14B
20D
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
94
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
79
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