NATIONAL BUREAU OF STANDARDS REPORT

2923

SUMMARY OF RESULTS OF PERFORMANCE

TESTS OF TEN CLEANABLE IMPINGEMENT

TYPE AIR FIITERS

by

Henry E. Robinson

Thomas W. Watsoh

Heating and Air Conditioning Section

Building Technology Division

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, S^retary

NATIONAL BUREAU OF STANDARDS

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

The scope of activities of the National Bureau of Standards is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section is engaged in specialized research, development, and engineering in the field indicated by its title. A brief description

of the activities, and of the resultant reports and puhfications, appears on the inside of the back

cover of this report.

Electricity. Resistance Measurements. Inductance and Capacitance. Electrical Instruments. Magnetic Measurements. Apphed Electricity. Electrochemistry.

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

Technology. Length. Gage.

Heat and Power. Temperature Measurements. Thermodynamics. Cryogenics. Engines and

Lubrication. Engine Fuels. Cryogenic Engineering.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State

Physics. Electron Physics. Atomic Physics. Neutron Measurements. Infrared Spectroscopy.

Nuclear Physics. Radioactivity. X-Rays. Betatron. Nucleonic Instrumentation. Radiological Equipment. Atomic Energy Commission Instruments Branch.

Chemistry. Organic Coatings. Surface Cheipistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Aerodynamics. Engineering Mechanics. Hydrauhcs. Mass. Capacity, Density, and Fluid Meters. Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Organic Plastics. Dental Research.

MetaUurgy. Thermal MetaUmgy. Chemical Metallmgy. Mechanical Metallurgy. Corrosion.

Mineral Products. Porcelain and Pottery. Glass. Refractories. Enameled Metals. Concreting Materials. Constitution and Microstructure. Chemistry of Mineral Products.

Building Technology. Structural Engineering. Fire Protection. Heating and Air Conditioning. Floor, Roof, and Wall Coverings. Codes and Specifications.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Machine

Development. ^

Electronics. Engineering Electronics. Electron Tubes. Electronic Computers. Electronic

Instrumentation.

Radio Propagation. Upper Atmosphere Research. Ionospheric Research. Regular Propagation Services. Frequency Utilization Research. Tropospheric Propagation Research. High

Frequency Standards. Microwave Standards.

Ordnance Development. These three divisions are engaged in a broad program of research

Electromechanical Ordnance, and development in advanced ordnance. Activities include

Ordnance Electronics. basic and applied research, engineering, pilot production, field testing, and evaluation of a wide variety of ordnance materiel. Special skills and facilities of other

NBS divisions also contribute to this program. The activity is sponsored by the Department of

Defense.

Missile Development. Missile research and development: engineering, dynamics, intelligence,

instrumentation, evaluation. Combustion in jet engines. These activities are sponsored by the

Department of Defense.

9 Office of Basic Instrumentation • Office of Weights and Measures.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003 - 30-4715 November I 6 , 1953 2923

Summary of Results of Performance

Tests of Ten Cleanable Impingement

Type Air Filters

by

Henry Eo Robinson

Thomas W. ¥atson

Heating and Air Conditioning Section

Building Technology Division

to

Bureau of Ships, Code 327

Department of the Navy

References NPO - 15479 Index ioo NSN I 3 O-OOI

<@>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Ths publication, reprinting, or reproduction of this report In any form, either In whole or In part, la prohibited

unleia permission is obtained In wrItIngfremtheORice of the Director, National Bureau of Standards, Washington

25. D, C. Such permission Is not needed, however, by a Government agency for wh'ch a report has been specifically prepared If that agency wishes to reproduce additional copies of that particular report for Its own use,
1
Performance Tests of Ten

Cleanable Impingement“Type Air Filters

I. INTRODUCTION

At the request of the Bureau of Ships„ Code 327, Navy Department (NPO-15479, Index Noo NSM 130-001 j qualification tests

were made to determine the performance of cleanable viscidimpingement type air filters in accordance with Section 4<>5 of

Military Specification MIL-F-16552 (Ships) dated 1 October

1951 as modified by Amendment 1 dated 15 April 1952

»

The tests were performed on ten specimen filters submitted by m.anufacturers at the request of the Bureau of Ships,

and included determinations of the dust-arresting efficiency,

pressure drop, specific dirt load and cleanabilit}?’ of the

specimens at three face air velocities, namely 300, 600 and

960 feet per minute

o

This report presents a summary of the results obtained

for the ten filters, which were reported previously in seven

separate reports*

II* DESCRIPTION OF THE FILTER SPECIMENS

The ten filters were of the viscid-impingement cleanable

permanent type, all nominally 20x20x2 inches in size* Each

had an enclosing frame of metal, approximately 19“l/2xl9-l/2x2

inches in outer dimensions, leaving an opening for passage of

air into the media approxim.ately 1^ inches square, with a

corresponding net face area of approximately 2,27 square feet*

The filters had various types of metallic media, in most

cases of ferrous metal* With each filter its m.anufacturer furnished an oil or adhe-sive for oiling the specimen* This was

done in a uniform manner, in preparation for each test, by immersing the filter in the liquid and letting the excess oil

drain off with the filter standing on edge for a period of

from 16 to 24 hours in a room at a temiperature between 70 and

90°F*

The filters are designated in this report by letters chosen

at random, as indicated in Table 1* Filters designated by the

same letter were submitted by the same manufacturer*

III* TEST METHOD AND PROCEDURE

The dust-arresting efficiency of each filter was determined

by the NBS ”Dust Spot Method’^ using as a test dust Cottrell precipitate at a concentration of one gram per thousand cubic feet

of air* The test method is described in the paper "A Test Method

for Air Filters” by R* S* Dill (ASHVE Transactions, Vol* 44,

Po 379, 193^)0

„ 2

Dirt-holding capacity was determined by supplying to

the filter air in which were dispersed cotton lint and

Cpttrell precipitate in the approximate proportions of

4% and 96^ by weight, respectively. The average rate of

feed of the contaminants was not more than 25 grams per

hour per square foot of net filter face area at each face

velocity. The lint used for this purpose was No. 7 cotton

linters ground in a Wiley m.ill with 4 rnm screen.

The efficiency and dirt-loading tests were m.ade at

three different air velocities, namely, 300, 6 OO and 900

fpm.

In the tests at each velocity, the following uniform

procedure was employed. The clean filter, after oiling

and draining as described above, was installed in the test

duct and its initial pressure drop was measured at 300,

600 and 900 fpm air velocity. The initial efficiency of

the filter at the test velocity was then determined, following which the process of loading the filter with a mixture

of 4 percent lint and 96 percent Cottrell precipitate by

weight was started. At intervals the increasing pressure

drop of the filter vms recorded. At suitable periods as

loading progressed, the efficiency of the filter was determined using 100 percent Cottrell precipitate. In addition, the efficiency of the filter was determined at the

end of a day of loading, and at the start of the next day,

to ascertain whether the rate of dirt loading was overtaxing the wetting rate of the filter adhesive. The dirt loading was continued, in general, until the rate of pressure

drop rise increased to approximately 0.004 inch W.G. per

gram of dirt mixture fed per square foot of filter net face

area

,

The filter was then removed from the test duct and

cleaned by means of a stream of cold water from a highpressure hose nozzle, directed at and into the filter media.

After drying, the filter was re-oiled for subsequent tests

or for measurement of its initial pressure drop after the

final cleaning.

IV. TEST RESULTS

A. Performance

Table 1 presents values of the dust-arresting efficiency

and the pressure drop through each filter at various specific

dirt loadings (in grams of a mixture of cotton linters

and 96% of Cottrell precipitate, by weight, per square foot

of net filter face area), at air delivery rates corresponding to net face air velocities of 300, 6 OO and 900 feet per

minute

„
IIIIIIII
“ 3 -

B. Cleanability

Except as noted in one instance below, all of the filters,

treated with the oils supplied by their manufacturers, were

considered satisfactorily cleanable using cold water from a

pressure hose nozzleo In general, it appeared that filters

oiled with water-emulsifying oils were cleaned more readily

and quickly than those with non-emulsifying oilSo

Filter B1 could not be cleaned of all evident dirt by

the method used, and showed an increase of about S0% in pressure drop after three loading and cleaning operations,

Co General

None of the filters evidenced any tendency for its media

to become "dry” of adhesive as a result of the dirt loading

rates used, which were in general from 15 to 25 grams per

square foot per hour.
II

I

I

I

I

I

m
Table 1 Summary-—Cleanable Impingement-Type Air Filters

Efficiency and Pressure Drop at Various Specific

Dirt Loadings

Efficiency, % : Pressure dror,inch WoG,

Spec. dirt l^dL?. * 0 2^ 29^ • _Q_ 4Q0

=!'gram/sqoft

,

300 fpm Face Velocity

Filter No.

A1 37 42 4^ 47 66 : 0.04 .05 .07 .12 .26

A2 3^ 41 50 61 - : .05 .06 .09 .23

B1 43 51 57 69 — : .04 ,0^ .17 .35

B2 45 57 62 - : . 06 .12 .25

C 47 51 55 60 63 : .04 .07 .11 .19 . 44

D1 44 51 55 63 70 : .04 .07 .11 ,20 .40

D2 47 53 61 73 - : .05 .0^ .14 .29

E 42 51 56 65 : .05 .09 .17 .36 - F 51 54 63 74 - : .05 .Of? .15 ,41

G 54 52 53 69 - : .04 .06 .09 .33 - 600 fpm Face Velocity

A1 44 51 56 62 : .14 .If? .25 .52

A2 42 44 61 69 : .15 .21 .33 .54

B1 55 65 65 : .16 .31 .55 — B2 52 64 74 — - : .22 .37 .74

C 56 63 63 65 66 : 0 I 6 . 26 .32 .41 .59

D1 52 59 63 66 69 : .14 .22 ,29 .39 ,56

D2 57 61 64 67 : .16 .23 .32 .49

E 54 5^ 61 — : .1^ .29 .52

F 56 61 71 73 - : ,1S .26 .35 .59

G 60 63 63 71 ; ,14 .24 .31 .55 “

900 fpm Face Velocity

A1 53 53 59 60 a.

: .31 .36 .49 .79 as. A2 54 59 63 - - : .32 .43 .59 <» B1 63 74 - - : .45 .79 0. B2 5^ 71 - - « 0 .75 c=> — <», C 60 6^ 74 74 72 : .34 .53 .6^ .51 1.00

D1 59 60 64 67 74 : .2^ .43 .57 .72 .96

D2 65 67 69 76 — : .34 .45 .65 .57

E 63 66 - — - : .40 .63 c» F 61 73 77 73 : .36 .50 .65 .53 — G 65 69 69 75 - : .32 .49 .63 .55 -

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 Pubhc 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; 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 Energy Commission. The scope of activities is suggested by the listing of divisions and sections on the inside of the

front 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. Pubhshed papers appear either in the

Bureau’s own series of pubfications or in the jomrnals of professional and scientific

societies. The Bureau itself publishes three monthly periodicals, available from

the Government Printing Oflice: 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 foimd in NBS Circular 460,

Publications of the National Bureau of Standards ($1.00). Information on cali- bration services and fees can be found in NBS Circular 483, Testing by the National

Bureau of Standards (25 cents). Both are available from the Government Printing Office. Inquiries regarding the Bureau’s reports and publications should be

addressed to the Office of Scientific Publications, National Biueau of Standards,

Washington 25, D, C.