NATIONAL BUREAU OF STANDARDS REPORT

2699

PERFORMANCE TESTS OP OLEARABLE

IMPINGEMENT TYPE AIR FILTERS

TYPE EWA AND TYPE EWAP

(CONTINENTAL)

by

Henry S, Robinson

Thomas W» Watson

to

Bureau of Ships

Department of the Navy

<22

^

U. $. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

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 publications, appears on the inside of the nack

cover of this report.

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

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

Technology. Length. Gage.

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

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

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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.

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Development.

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Instrumentation.

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Frequency Standards. Microwave Standards.

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

Oectromechanici^ Ordnance, and development in advanced ordnance. Activities include

Ordnance Electronics. basic and applied research, engineering, pilot production, field testmg, 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,

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

Department of Defense. • Office of Basic Instrumentation • Office of Weights and Measures.
NATiOMAL BUREAU OF STANDARDS REPORT

NBS PROJECT NSS REPORT

1003“20”l4.7l5 29 3 1953 2699

PERFORMANCE TESTS OF CLEANABLE

IMPING-ElffiNT TYPE AIR FILTERS

TYPE EWA AND TYPE EV\lAP

Manufactured by

Continental Air Filters., Inc«

Louisville, Kentucky

by

Henry E. Robinson

Thomas ¥, Watson

Heating and Air Conditioning Section

Building Technology Division

to

Bureau of Ships, Code 32?

Department of the Navy

References NPO = 15479' Index No# NSM 130-001

The publication, reprint

unlees permission Is obtt

2S, D, C. Such permli

prepared ' If that agen<

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

rt, Is prohibited

rds, Washington

leen speciflcally

or Its own use.

PERFORMANCE TESTS OF CIEANABLE

IMPINGEITENT TYPE AIR FILTERS

TYPE EWA Am TYPE EWAP

Ic INTRODUCTION

At the request of the Burea.u of Ships, Code 32?s Navy De^

partment (NPO” 1514-795 Index Noo NSM 130-OOlj qualification tests

were made to determine the performance of cleanab3.e viscid^

impingement type air filters in accordance with Section of

Military Specification MIL“F“l6552 (Ships) dated 1 October 1951

as modified by Amendment 1 dated 15 April 1952

o

The tests were performed on specimen filters submitted by

the manufacturer at the request of the Bureau of Shlps^ and included determinations of the dust“ arresting efficiencyj pressure

drop, specific dirt load, and cleanability of the specimens at

three face air velocities, namely 300, 600, and 900 feet per

minute o

II« DESCRIPTION 0F THE FILTER SPECIMENS

The two filters submitted were manufactured by Continental

Air Filters, Incorporated, of Louisville, Kentucky, and were of

the cleanable viscid type, 20 x 20 x 2 inches in nominal sizeo

They were identified as Type EWA and Type EWAP air filters®

The media of the filters consisted of formed strips of

al-uminum about 2 inches wide which had been intricately corrugated with double compound curves® The strips were placed on

edge in non-nesting relationship, thus forming many honeycomb

openings and were held together at the edges by a steel retaining frame®

The Type EWA filter had approximately 5o5 layers of metal

per inch of pile® The filter had actual outside dimensions of

19 1/2 X 19 1/2^ X 2 inches, leaving a free opening l8 inches

square (2®25 ft^ net face area) and weighed 9®2 lb when clean®

The Type EWAP filter was similar in construction to the

Type EWA filter except that the layers of metal had been indented forming small dimples about 3/16 inch apart® Some of

these dimples were perforated, and some were not® The filter

had actual outside dimensions of 19 1/2 x 19 1./2 x 2 Inches,

leaving a free opening l8 1/16 inches square (2®2? ft® net face

area) and weighed 9ol4. lb when clean® There were approximately

5o7 layers of metal per inch of pile®

=> 2 °

The manufacturer submitted an adhesive designated as ”C-l”

oil for oiling both filters^ This was done in preparation for

test by immersing the filters in the liquid and letting the excess oil drain off with the filters standing on edge for a minimum of 16 hours prior to the testo

lllc TEST ilETHOD AND PROCEDUEE

The dust=arre sting efficiency of the 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, So Dill ( ASH¥E Transactions <, Volo

Po 379, 1938)o

Dirt-holding capacity was determined by supplying to the

filter air in which were dispersed cotton lint and Cottrell precipitate in the approximate proportions of and 96^ by weight,

respectivelyo 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 velocityo The lint used for this purpose

was Noc 7 cotton linters ground in a Wiley mill with 4 screeno

The efficiency and dirt-loading tests were made at three

different air velocities^ namely^ 300^ 600^ and 900 fpmo

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 percent lint and 96 percent Cottrell precipitate by weight was started* At intervals

the Increasing pressure drop of the filter was 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*00[|. inch W*G* per gram of dirt

mixture fed per square foot of filter face area*

The filter was then removed from the test duct and cleaned

by means of a stream of cold x^rater from a high-pressure 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*

“ 3

=

IVo TEST RESULTS

The pressure drops of the clean oiled filters^, in inch WoGo,

at 300c, 600 j and 900 fpm face air velocity, were measured at the

start of each of the tests, and after the 900 fpm test, as shown

in table lo

TABLE 1

Face Velocity, fpm 01 0 600 900

Type EWA

At start of 300 fpm test OoOl^ 0 o310

At start of 600 fpm test 0043 • lU .305

At start of 900 fpm test c042 o310

After 900 fpm test 0043 0 11+3 .305

Increase in PoD, after

3 cleanings, percent 2 0 0

Type EWAP

At start of 300 fpm test O0OI1.3 el32 .. o330

At start of 600 fpm test 0043 cl30 o326

At start of 900 fpm test 0 O4I1. 0 130 o 322

After 900 fpm test oOii.3 0I48 c 320

Increase in P,,D<, after

3 cleanings, percent 0 0 0

A summary of the test data obtained in dirt “loading test:

conducted at 300, 600, and 900 fpm face velocity is given in

table 2, for each of the filterso

TABLE 2

Filter Face Velocity Dirt Load*«- Pres sure Drop Efficiency

fpm grams/s q f

t

inch ¥G percent

EWA 300 0 O0O42

3 eOl+2 37

3 o 0lr2

8 0 Olj^ 39

39 o 0L!.8 14-3 62 6 Oii-6 38

70 o0l|6 u

TABLE 2 c orit Inue d

Filter Face Velocity Dirt Load'55- Pressure Drop Efficient

fpm grams /sq ft inch WG percent

EWA 300 75 O0O47 41

78 <, 04.8 4-0

107 0 O52 it2(p)

110 0O4.9 41 (A)

196 c 070 k8

257 «093 50 CP)

265 0O97 49CA)

276 0 IO3 54-

325 clk9 60

370 o203 61

391^ o250 64(P)

397 o264- 65(A)

4^9 o34-8 73

l|-59 o520 76

'55-Average mixt-ure ? 3o9^ lintj 96ol^ Cottrell precipitate by weight

Average rate of dirt loading? 17 <>3 grams per square foot per hour

0 Oolkk

5 o1L}4 44

11 0 144- 40

17 0 144- 43

24. 0 i5o 47

82 ol85 47(P)

87 0170 52(A)

133 o200 48

182 o25o 54

215 c300 57

236 o330 64(P)

2k2 o34-0 59(A)

251 o360 60

297 o5io 62

334. c675 66

352 0805 72

'55-Average mixtures [j.o0^ lint, 96% Cottrell precipitate by weight

o

Average rate of dirt loadings 21<,Ij- grams per square foot per hour
r

1 .

•'o.

t' ir

'f

, <4

''I

/'V

’rm

f

'

V.
5

TABLE 2 = continued

Filter Pace Velocity Dirt Load-' Pressure Drop Efficiency

fpm grams /sq ft inch WG percent

EWA 900 0 0e310 <= 6 c310 53

12 e305 52

52 0 3Ii 0 55(P)

9 »3i5 1i8(A)

6Il o3l5 51

79 , 31i5 5I1 117 .363 53

210 .510 60

27.''- ,6'h 65 (p)

' 231 .713 60(A)

302 .795 60

339 .990 65

348 1,050 68

-'Average mixture: Lt-oO/a lint, 965 Cottrell precipitate by weight.

Average rate of dirt loading; 20 » 2 grams per square! foot per hour

EV/AP 300 0 0,0h5

3 eOLj.5 38

8 ,0Il5 51

3h e 058 45

52 ,050 52

65 0 O 5 O 53

152 .075 39

188 ,093 58(P)

191 ,090 5KA)

207 ,102 50

256 ,15^^ 60

277 .195 61

290 ,212 62 ( P

)

203 e210 60(A)

335 .305 70

353 o526 77

*«-Average mixture; 1|,0% lint^ 9Gfo Cottrell precipitate by weight

Average rate of dirt loading; 21,0 grams per square foot per hour
l?l1

1
6

TABLE 2 “ continued

Filter Face Velocity Dirt Load'^-' Pressure Drop Efficiency

fpm graras/sq ft inch WG percent

SWA? 600 0 0,150 cm 6 ,150 *4-2 11 oi 50 k5

97 , 20li. 127 ,250 i^.8 (p)

133 o 220 50 (.A)

160 ,250

21 b ,363 6k

251 oIj-90 65

273 , 6l5 63(p)

278 ,610 68 (A)

300 ,81p0 69

ihiverage mixture: k,0% lint, 96% Cottrell precipitate by weights

Average rate of dirt loading: 22 „

5

gram.s per square .foot per hour

SWAP 900 0 0,322

18 ,322 kk

27 ,322 53

7k ,368 57

120 , k55 6 lCk

129 , I4.16 60 U)

I 8 k .536 61

21.1.0 ,729 69

285 ,925 75

-'^Average mixture: hi.„0% lint, 965 Cottrell precipitate by weighto

Average rate of dirt loading: 25 «k grams per square foot per hour

Note: Efficiencies marked (?) or (A) x\rere determinations y.iade

at the end of a dav of loadln.s, and at the start of the

next day of loading, respectively.

V. SUMMARY OF RESULTS

A. Performance

The test data are plotted in figure 1 and figure 2, which

show the variation of the pressure drop and of the efficiency

of the filters as they ^^^ere subjected to Increasing specific

dirt loading at face velocities of 300, 600, and 900 feet per

minute

,

" 7

Table 3 presents values of the pnessujre drop (PoDa). in

inches of waterj and of the approximate efficiency (Effa), in

percent, as taken from the curves of figirce 1 and figure 2, at

various specific dirt loadings.

TABLE 3

Spec. Dirt Ldg. 0 100 200 300 kOO

grams/sq ft (Initial)

Pace Vel., fpm P.D, Eff

.

P.D. 'Eff

.

P.D, Eff. P.D. Eff. P.D. Eff.

300 0.0k 37 .05

E’W'A

.07 k8 .12 k7 .26 66

600 ,lli- kk ,18 51 .28 56 .52 62 - - 900 ,31 53 .36 53 .49 59 .79 60 - -

EV/AP

300 0 , op 38 .06 kl ,09 50 .23 61

600 . lb 42 .21 li-h- .33 61 .8k 69 - 900 .32 5k Ji3 59 .59 63 - =. -

3. Gleanabillty

The pressure drops of the clean oiled filters at 300, 600,

and 900 fpm face velocity recorded in table 1 under Test Results

indicate that, after the filters had been subjected to three

loadings x^ith the dust-lint mixture and thi=ee cleanings and reoilings, their average pressure drops remained substantially the

same. It is believed that both filters can be considered as satisfactorily cleanable.

0. General

The fact that efficiencies determined at the end of a day

of loading of the filters (those marked (P) in table 2) XArere approximately the same as those made at the start of the next

day of loading (those marked (A)) indicates that the dirt loading rates to which the filters were subjected did not overtax

the wetting-rate of the filter adhesive and cause the filter

surfaces to become dry.

CONTINENTAL E W A

CD

UJ

(T3

</)

(/) UJ

o:

Q.

CONTINENTAL EWAP

100 200 300 400 500

FIG.

NBS LOAD, GRAMS PER SQUARE FOOT

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; 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. 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 Circular 460, Publications of

the National Bureau of Standards ($1.00). Information on calibration 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 Bureau of Standards, Washington 25, D. C.