(lo

NATIONAL BUREAU OF STANDARDS REPORT

6408

PERFORMANCE TESTS OF

TWO THROW-AWAY TYPE "DUSTGARD" AIR FILTERS

MANUFACTURED BY

AMERICAN ROCK WOOL CORPORATION

WABASH, INDIANA

by

Carl W. Coblentz and Paul R. Achenbach

Report to

Public Buildings Service

General Services Administration

Washington, D. C.

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions find 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, I9S0. 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; invention 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. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic EnergyCommission. The scope 'of activities is suggested by the listing of divisions and sections on the

inside of the hack cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project or program. Published 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 monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

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

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circidar 360, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office, Washington 25, 1). C.

Inquiries regarding the Bureau’s reports should be addressed to the Office of Technical Information, National Bureau of Standards, Washington 25, D. C.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1000-30-4830 May 14, 1959 6408

PERFORMANCE TESTS OF

TWO THROW-AWAY TYPE "DUSTGARD" AIR FILTERS

MANUFACTURED BY

AMERICAN ROCK WOOL CORPORATION

WABASH, INDIANA

by

Carl W. Coblentz and Paul R. Achenbach

Air Conditioning, Heating, and Refrigeration Section

Building Technology Division

to

Public Buildings Service

General Services Administration

Washington, D. C.

IMPORTANT NOTICE

NATIONAL BUREAU OF $ intended for use within th to additional evaluation am

listing of this Report, eithe

the Office of the Director, | however, by the Governmei

to reproduce additional cop

Approved for public release by the

Director ot the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

progress accounting documents

Formally published it is subjected

g, reproduction, or open-literature

ission is obtained in writing from Such permission is not needed,

y prepared If that agency wishes <NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE TESTS OF TWO

THROW-AWAY TYPE "DUSTGARD" AIR FILTERS

by

Carl W. Coblentz and Paul R. Achenbach

1

.

INTRODUCTION

At the request of the Public Buildings Service,, General

Services Administrat ion, the performance characteristics of

two specimens of the same model of throw-away type "Dustgard"

air filters were determined. The scope of this investigation

included the determination of the arrestance of Cottrell precipitate and atmospheric dust, the dust holding capacity and

the pressure drop at an air flow rate of 800 cfm.

2.

DESCRIPTION OF THE TEST SPECIMENS

The test specimens were manufactured and supplied for test

purposes by the American Rock Wool Corporation of Wabash, Indiana,

and were identified by their trade name, "Dustgard." The filter media were 2-in. thick pads of light gray colored noncombustible fibers and were treated with an oily adhesive. The

cardboard frames measured 20 x 20 x 2 in. on the outside; they

consisted of a U-shaped channel, leaving a 1J 5/8 in. square

opening, i.e., 2.16 sq ft net face area. The weights of the

two test specimens were 435 grains and 438 grams, respectively

(approximately 15 1/2 oz).

3

.

TEST METHOD AND PROCEDURE

The performance of the filters was determined at 370 ft/min

face velocity, i.e., at an air flow rate of 800 cfm. The arrestance measurements were conducted in accordance with the NBS "Dust

Spot Method" as described in the paper, "A Test Method for Air

Filters" by R. S. Dill (ASHVE Transactions, Vol. 44, p. 379, 1938).

The aerosol used for the arrestance determination was Cottrell precipitate which had been sifted through a 100-mesh wire

screen. In order to simulate actual operating conditions when

loading the filters, four percent by weight of cotton linters,

previously ground in a Wiley mill with a four-millimeter screen.

- 2 -

was introduced simultaneously with the Cottrell precipitate.

The pressure drop of the filters was recorded after each increment of 20 grams of dust had been introduced into the test

apparatus. Whereas the arrestance determinations were made with

100 percent Cottrell precipitate, cotton linters were added to

retain a ratio of four parts by weight to every 96 parts of Cottrell precipitate, including that amount used for arrestance

measurements. Arrestance determinations were made at the beginning and at the end of the loading of each filter and also at

several intermediate load conditions.

Before introducing dust, the pressure drop of the first

test specimen was determined at five different air flow rates

from 420 cfm to 1200 cfm, corresponding to face velocities of

194 ft/min to 555 ft/min. Two arrestance determinations were

made on the second test specimen using the laboratory air as

the aerosol without addition of further particulate matter,

before arrestance determinations were made with Cottrell precipitate.

The filters were loaded with a dust concentration of approximately 1 gram of dust in 1000 cu ft of air until the pressure drop exceeded 0.5 in. W.G., at which point the test was

discontinued

.

4. TEST RESULTS

Table 1 shows the pressure drops of the first filter before

the loading test at air flow rates from 420 cfm to 1200 cfm, i.e.,

face velocities of 194 ft/min to 555 ft/min. The pressure drop

of the filter increased from 0.030 in. W.G. at the lowest flow

rate to 0.168 in. W.G. at the highest flow rate and was 0.088

in. W.G. at the rated face velocity of 370 ft/min.

Table 1

Pressure Drop of Clean Filter, Specimen 1

Air Flow Rate, cfm

420

600

800

1000

1200

Face Velocity, ft/min

T94

278

370

463

555

Pressure Drop, in. W.G.

0.030

0.055

0.088

0.125

0.168
. ’

.
-3-

Table 2

Performance of Filter Specimen 1 at 800 cfm

(370 ft/min Face Velocity)

Dust Load Pressure Drop Arrestance

g/sq ft in. W.G. jg

0 0.088 - 7 0.097 48*

54 0.180 54

118 0.300 63*

142 0.367 64*

190 0.516 65

* Average of two tests

Table 3

Performance of Filter Specimen 2 at

(370 ft/min Face Velocity)

800 cfm

Dust Load Pressure Drop Arrestance

g/sq ft in. W.G. ~T~

0 0.089 6 . 4 ( Note

5 0.097 50*

94 0.272 70*

124 0.336 71*

158 0.442 72*

177 0.521 73

Note A: This value presents the average of two tests in

which the laboratory air with its suspended particulate matter was the aerosol.

* Average of two tests

Tables 2 and 3 show the pressure drops and arrestance values

determined during the loading of the two test specimens. These

data are presented graphically in Fig. 1 as four smooth curves

drawn to approximately fit the individual points of observation.

It will be noted that the arrestance determined with the second

filter using the particulate matter of the laboratory air as an

aerosol is not shown on this graph.

American Rock Wool Corporat ion, DUSTGARD

DUST LOAD, grams per square foot
\
-4-

The dust load values shown in Tables 2 and 3 are the amount

of dust introduced into the test apparatus divided by the net

face area of the filter and diminished by the percentage of

dust fallout upstream of the filter. This fallout was determined

at the conclusion of each test by sweeping out the test apparatus

and calculating the ratio of fallout to the total dust introduced into the system.

The dust loads accumulated on the two test specimens when

the pressure drop had increased to 0.5 in. W.G. were taken from

the lower curves of Fig. 1 and are shown in Table 4 as the "Dust

Holding Capacity." Also indicated in this table are the "Mean

Arrestance" values^ which represent the average arrestance during

the period in which the capacity dust load was accumulated, taken

from the arrestance curves of Fig. 1.

Table 4

Dust Holding Capacity and Mean Arrestance

(Determined from Fig. l)

Filter Specimen No. 1 2

Dust Holding Capacity,, grams/sq ft 186 173

Mean Arrestance, percent 59 65

Although no difference had been noticed in the appearance

of the two filters before or after the tests, the observed arrestances were significantly different. No definite reason for

thre this difference can be -mad e c-r Fe<eeo

The differences in the results obtained on the two specimens

probably represent variations in the density or uniformity of the

media or variations in the amount of adhesive on the media at the

start of the test. However, the operation of the second specimen

with laboratory air as the aerosol for about two hours prior to

the first test with Cottrell precipitate may have had a small

effect on the results. During the two hours’ operation with atmospheric air as the aerosol, the pressure drop across specimen

No. 2 increased from 0.089 in. W.G. to 0.094 in. W.G. indicating

that the dust deposit had a measurable effect on the density of

the media. It is probable that this deposit consisted principally of fine particles which penetrated into the media and some

lint on the upstream surface.

Since the two specimens were tested one after the other by

the same personnel, it seems unlikely that the manipulations of

the operator were responsible for the observed differences in

test results.

USCOMM-NBS-DC

tj. S. DEPARTMENT OK COMMERCE

f tj. Su-fliton, Si'rrr'trity

NATIONAL mmlCAU OF STANDAHIIH

A. V. Antlit, l)irncfor THE .NATIONAL WIJWKAIJ OF STANDAWON

The scope of activities of the Nntionnl Bureau of Standards at Its headquarters in Washington,

I). C., dnd Its Major laboratories in Boulder, Colo., Is suggested in tlie following listing of the

divisions and sections engaged lit technical work. In general, each section ear lies out specialized

research, development, and engineering in the field indicated hy Its title, A brief 'description of

the activities, and of the resultant publications, appears on the inside front cover. WASHINGTON, BP. €.

KIcCtflltHy nnil Klfintl*Olllt;tt. Resistance and Reactance. Electron Devices. Electrical In- struments. Magnetic Measurements. Dielectrics.. Engineering Electronics. Electronic Instru- mentation. Electrochemistry.

Optica and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

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Materials. Constitution and Microstructure.

fllillidiug TeeOiaoiogy. Structural Engineering. Fire Protection. Air Conditioning, Heating,

and Refrigeration. Floor, Roof, and Wall Coverings. Codes and Safety Standards. Heal Transfer.

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Onto l*ro«M»SBtng Systems). SEAC Engineering Croup. Components and Techniques. Digital

Circuitry. Digital Systems. Anolog Systems. Application Engineering.

• Office of Basic Instrumentation. * Oliice of Weights and Measures.

IlOUB.tfBUIl, COBABBKABBO

BSnginwaring. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Gas Liquefaction.

B&adlo I*ra|»agaiioa I'liyaicft. Upper Atmosphere Research, lonospheri j Research. Regular Propagation Services, Sun-Earth Relationships. VUE Research. Ionospheric Communication

Systems.

Kadio BVo|injU(atfi<»i8 fEngiueerBUg;. Data Reduction liisirumeulalion. Modulation Systems.

Navigation Systems, itadio Noise. Tropospheric Measurements. Tropospheric Analysis. Radio

Systems Application Engineering. Radio-Meteorology.

Madia Standard*!. High Frequency Electrical ,Standards. Itadio Broadcast Service. High

frequency impedance Slumlords. Electronic Calibration Center. Microwave Physics, Microwave

Circuit Standards,
NBS