NATIONAL BUREAU OF STANDARDS REPORT

6938

PERFORMANCE TEST OF A "DUST-GARD"

THROW-AWAY TYPE AIR FILTER

by

Carl W. Coblent z and Paul R. Achenbach

Report to

Public Buildings Service

General Services Administration

Washington 25 j, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards: the determination of physical constants and

properties of materials; the development of methods and instruments for testing materials, devices,

and structures; advisory services to government agencies on scientific and technical problems; in- vention and development of devices to serve special needs of the Government; and the development

of standard practices, codes, and specifications. The work includes basic and applied research,

development, engineering, instrumentation, testing, evaluation, calibration services, and various

consultation and information services. Research projects are also performed for other government

agencies when the work relates to and supplements the basic program of the Bureau or when the

Bureau’s unique competence is required. The scope of activities is suggested by the listing of

divisions and sections on the inside of the back cover.

Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers. These papers appear either in the Bureau’s own series of publications or in the journals

of professional and scientific societies. The Bureau itself publishes three periodicals available from

the Government Printing Office: The Journal of Research, published in four separate sections,

presents complete scientific and technical papers; the Technical News Bulletin presents summary

and preliminary reports on work in progress; and Basic Radio Propagation Predictions provides

data for determining the best frequencies to use for radio communications throughout the world.

There are also five series of nonperiodical publications: Monographs, Applied Mathematics Series,

Handbooks, Miscellaneous Publications, and Technical Notes. Information on the Bureau’s publications can be found in NBS Circular 460, Publications of the

National Bureau of Standards ($1.25) and its Supplement ($1.50), available from the Superintendent

of Documents, Government Printing Office, Washington 25, D.C.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

I960 ' 6938

A "DUST-GARD"

AIR FILTER

( Carl W. Coblent-z and Paul R. Achenbach

Air Conditionings Heatings and Refrigeration Section

Building Technology Division

1003-30-10630 August 17s

PERFORMANCE TEST OF

THROW-AWAY TYPE

by 1

to

Public Buildings Service

General Services Administration

Washington 25 j, D. C„.

NATIONAL BUREAU OF ST/

Intended for use yvlthln the 1

to additional evaluation and r

liitlr.? r.f this Report, either I *he Office of the Director, Na

f.owevor, by the Government

to reproduce additional cople

IMPORTANT NOTICE

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

regress accounting documents

mally published it is subjected

reproduction, or open-literature

Ion is obtained in writing from

Such permission Is not needed,

prepared If that agency wlshel

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

UinwiAL

PERFORMANCE TEST OF A "DUST-GARD"

THROW-AWAY TYPE AIR FILTER

by

C. W. Coblentz and P. R. Achenbach

1

Introduction

At the request of the Public Buildings Service,, General

Services Administration, the performance characteristics of a throw-away type air filter, identified by the trade name "DustGard, ” were determined. The scope of this examination included

determination of the arrestance of Cottrell precipitate, pressure drop, and dust-holding capacity at 370 ft/min face velocity of specimens with nominal thicknesses of 1 and 2 inches.

As part of an investigation made by the National Bureau of

Standards for the Department of Defense, the same performance

examinations were also made at a face velocity of 540 ft/min.

2

Description of Test Specimens

The test specimens were supplied by the U. S. Gypsum Company of Wabash, Indiana. The nominal size of these filters

was 20 x 20 Inches a,Yid 2 in. and .1 In. thick, respectively.

The filter medium was made of glass fibers and held in a cardboard frame with channel-shaped cross section. The face of

the filters was 17 5/8 in. square, offering a net face area

of 2.16 square feet. The weight of the clean 2 -in. filter

was 482 grams and that of the 1 -in. filter was 380 grams (17

oz and 13 1/2 oz, respectively). The filters were sprayed at

the factory with an adhesive.

3

Test Method and Procedure

Arrestance determinations were made with, the NBS ”Dust

Spot Test Method” using Cottrell precipitate as the aerosol.

The test method is described In a paper entitled, "A Test

Method for Air Filters,” by R. S. Dill (ASHVE Transactions,

Vci. 44. p. 379 , 1938).

The filters were placed in a frame, sealed to prevent

any by-pass of air, and then installed in the test apparatus.

During the test, samples of air were drawn from, the center

points of the test duct 1 ft upstream and 8 ft downstream of

the test specimen at equal rates and passed through known

areas of Whatman No. 4.1 filter paper. The ratios of the upstream and downstream filter paper areas were selected to

- 2 -

obtain a similar increase of opacity. The change of opacity of

these areas was determined with a sensitive photometer which

measured the light transmission of the same spot on each sampling paper before and after the test. The two sampling papers

used for each test were selected to have the same light transmission readings when clean. Air was drawn through both samplers while measured amounts of Cottrell precipitate were

introduced into the test apparatus. The arrestance, A (in percent),, was then computed by the following formula:

A = 100 - x x 100

Sp AU

where Sd and Su are the respective downstream and upstream filter sampling paper areas and AD and AU the respective changes

in opacity of the sampling papers. The aerosol used for the

arrestance determination was Cottrell precipitate, which had

been previously sifted through a 100-mesh wire screen. In

order to simulate actual operating conditions when loading

the filter, 4 percent by weight of No. 7 cotton linters, previously ground in. a Wiley mill with a 4-millimeter screen,

were introduced simultaneously with the Cottrell precipitate.

Whereas the arrestance measurements were made with Cottrell

precipitate only, the cotton, linters were added during the

loading process and a sufficient amount was included to obtain an overall weight ratio of 96 to 4 parts by weight, including that portion of Cottrell precipitate which was used

for arrestance determinations.

Arrestance determinations were made at the beginning and

at the end of the loading period for each filter at each face

velocity. Also, additional arrestance determinations were

made at selected intervals while the filter was being loaded.

The pressure drop across the filter under test was .re- corded at the beginning of the test and after each increment

of 20 grams of Cottrell precipitate were introduced into the

test apparatus. The filters were loaded with a dust concentration of approximately .1 gram per 1000 cu ft of air until

the pressure drop reached 0.5 in. W.G. for the test conducted

at 370 ft/min face velocity, and 0.8 in. W.G. for the testconducted at 540 ft/min face velocity.

3-

4. Test Results

Tables 1 to 4 show the observed pressure drop, arrestance

and dust loads of the filters. The dust load per square footnet face area at the reported intervals is the weight of dust

and lint introduced into the test apparatus, diminished by the

fallout in the upstream portion of the test duct during that

interval, divided by the net face area of the filter. The total fallout was determined at the end of each test by weighing

the dust swept out of the upstream portion of the test duct.

For computing the dust load per square foot net face area, the

amount of dust and lint introduced into the test apparatus was

multiplied by 1 minus the ratio of fallout to the total dust

introduced, and divided by the net face area of the filter, ac

cording to the following formula:

D x (l - F)

L =

A

where L = dust load., grams per square foot

D = dust and lint introduced, grams

A = net filter area, square feet

p _ total fallout

total dust and lint introduced

The values shown in Tables 1 to 4 are graphically presented in Fig. 1 and 2, and smooth curves that approximate

the curves of the least mean square distances of the individual points of observation have been fitted to the data.

It will be noted that the dust-holding capacity, i.e., the

dust load at final pressure drop, of the 1-in. filter was

considerably lower than that of the 2-in. filter, at both

air velocities, whereas the arrestances of both filters were

similar. Table 5 summarizes the test results for both filter thicknesses and face velocities. The dust-holding capacity shown in this table is that dust load which, according

to the graph or test results, was reached at the final pressure drop of 0.5 to 0.8 in. W.G., respectively. Also shown

in this table are the mean arrestances for each filter under

the various test conditions, during the period in which the

capacity dust load was accumulated. These values were obtained by drawing horizontal lines through the arrestance

curves in Fig. 1 and 2, which would give the same areas between the curves and the lines above and below.

The initial pressure drop increased from 0.086 in. W.G.

across the 1-in. thick filter and 0.107 in. W.G. across the

2-in. thick filter to 0.156 in. W.G, and 0.196 in. W.G., respectively, with an increase in face velocity from 370 ft/min

-4-

to 540 ft/min, an increase of approximately 90 percent in each

case. The dust-holding capacity of the 1-in. thick filter decreased from 190 g/sq ft to 173 g/sq ft when the air velocity

was raised from 370 ft/min to 540 ft/min, whereas the dustholding capacity of the 2-in. thick filter slightly increased,

from 254 to 264 g/sq ft, with the increase of the face velocity.

The arrestance values determined for the clean filters

ranged from 58 percent to 63 percent and increased from 77 to

79 percent when the filters were loaded to their final pressure drop. The average arrestance for all four test conditions was between 72 and 73 percent. Except for the increase

of the arrestance value due to the dust load, which is to be

expected with this type of filter, there was no significant

difference of the arrestance in either of the test conditions.

Table 1

Performance of

U.S. Gypsum Co. "Dust-Gard" 1-in.

(Face Velocity, 370 ft/min. Aerosol,

Thick Air Filter

Cottrell Precipitate)

Dust Load

g/sq ft

Pressure Drop

in. W. Go

Arrestance

fo

0 0

4 0

57 0

110 0

154 0

190 0

086 - 091 58

194 72

304 75

411 77

505 78

Table 2

Performance of

U.S. Gypsum Co. "Dust-Gard” 1-in.

(Face Velocity, 540 ft/min. Aerosol,

Thick Air Filter

Cottrell Precipitate)

Dust Load

g/sq ft

Pressure Drop

in. W. G„

Arrestance

%

0 0

4 0

60 0

117 0

173 0

156 - 164 63

357 70

535 77

800 79

-5-

Table 3

U.S. Gypsum Co.

(Pace Velocity, 370

Dust Load

g/sq ft

0

4

48

92

136

180

251

Performance of

"Dust-Gard" 2-in.

ft/min. Aerosol,

Pressure Drop

in. W. G.

0.107

0.110

0.186

0.245

0.296

0.357

0.492

Thick Air Filter

Cottrell Precipitate)

Arrestance

£

61

72

75

75

76

78

Table 4

Performance of

U.S. Gypsum Co. "Dust-Gard" 2-in. Thick Air Filter

(Face Velocity 540 ft/min. Aerosol, Cottrell Precipitate)

Dust Load

g/sq ft

Pressure Drop

in. W. G.

Arrestance

%

0 0.196

4 0.203

60 0.357

117 0.469

175 0.594

228 0.699

264 0.801

59

71

71

74

76

77

Table 5

Summary

"Dust-Gard"

of Test Results on

Throw-away Air Filters

Thickness of Filter, inch

Face Velocity, ft/min

Final Pressure Drop, in. W.G.

Initial Pressure Drop, in. W.G.

Dust-Holding Capacity, g/sq ft

Initial Arrestance, %

Average Arrestance, %

Final Arrestance, %

1 2

370 540 370 540

0.5 0.8 0.5 0.8

0.086 0.156 0.107 0.196

190 173 254 264

58 63 61 59

72 73 73 72

78 79 78 77

USCOMM-NBS-DC

DUST LOAD

O o

(n <3 n ^

>

liTTI

U.S. DEPARTMENT OF COMMERCE

Frederick 1J. Mueller, Secretary NATIONAL BUREAU OF STANDARDS

A. V. Amin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

Boulder. Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the, field indicated hv

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the front cover. WASHINGTON, D.C.

Electricity and Electronics. Resistance and Reactance. Electron Devices. Electrical Instruments. Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic Instrumentation. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Photographic Technology. Length. Engineering

Metrology.

Heat. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheology. Molecular Kinetics. Free

Radicals Research. Atomic and Radiation Physics. Spectroscopy. Radiomctry. Mass Spectrometry. Solid State Physics. Electron Physics. Atomic Physics. Neutron Physics. Radiation Theory. Radioactivity. X-rays. High

Energy Radiation. Nucleonic Instrumentation. Radiological Equipment.

Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analy tical Chemistry. Inorganic

Chemistry. Electrodeposition. Molecular Structure and Properties of Cases. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics. Mass anil Scale. Capacity, Density, and f luid Meters. Combustion Controls.

Organic ami Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Poly- mer Structure. Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion. Metal

Physics.

Mineral Products. Engineering Ceramics. Glass. Refractories. Enameled Metals. Constitution and Microetructurc.

Building Technology. Structural Engineering. Fire Protection. Air Conditioning, Heating, and Refrigeration. Floor, Roof, and Wall Coverings. Codes and Safely Standards. Ileal Transfer. Concreting Materials.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics.

Data Processing Systems. SEAC Engineering Group. Components and Techniques. Digital Circuitry.

Digital Systems. Analog Systems. Application Engineering.

• Office of Basic Instrumentation. * Office of Weights and Measures. BOULDER, COLORADO

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Gas Liquefaction. Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular Propagation

Services. Sun-Earth Relationships. VII F Research. Radio Warning Services. Airglow and Aurora. Radio

Astronomy and Arctic, Propagation.

Radio Propagation Engineering. Data Reduction Instrumentation. Modulation Research. Radio Noise. Tropospheric Measurements. Tropospheric Analysis. Propagation Obstacles Engineering. Radio-Meteorology. Lower Atmosphere Physics.

Ihidio Standards. High Frequency Electrical Standards. Radio Broadcast Service. High Frequency I in* pedance Standards. Electronic Calibration Center. Microwave Physics. M icrowavc Circuit Standards. Radio Communication and Systems. Low Frequency and Very Low Frequency Research. High Fre- quency and Very High Frequency Research. I lllra High Frequency and Super High Frcqucncv Research. Modulation Research. Antenna Research. Navigation Systems. Systems Analysis. Field Operations.