NATIONAL BUREAU OF STANDARDS REPORT

PERFORMANCE TESTS OF CLEANABLE

IMPINGEMENT TYPE AIR FILTERS

TYPE HV-2 AND TYPE HV-2-16

manufactured byAmerican Air Filter Company, Inc.

Louisville, Kentucky.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

2285

by

Henry E. Robinson

Thomas ¥. Watson
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

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

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-20-4715 February IS, 1953. 22#5

PERFORMANCE TESTS OF CLEANABLE

IMPINGEMENT TYPE AIR FILTERS

TYPE HV-2 AND TYPE HV-2-16

manufactured by

American Air Filter Company, Inc.

Louisville, Kentucky

by

Henry E. Robinson

Thomas W. Watson

Heating and Air Conditioning Section

Building Technology Division

To

Bureau of Ships, Code 327

Department of the Navy

Reference: NPO - 15479 Index No. NSM 130-001

The publication, reprln

unless permission Isobt

25, D, C, Such permit)

cal ly prepared If that

Approved for public release by the

ar, ‘ 18 prohlbl,ed

. r

. ards, Washington Director of the National Institute of ha8 been 8pecl(i . Standards and Technology (NIST) , for its own use, on October 9, 201 5.
f II
Performance Tests of American Type HV-2 and HV-2-16 Air Filters

I. INTRODUCTION

At the request of the Bureau of Ships, Code 327, Navy Department

(NPQ'-*15479, Index No. NSM 130-001) qualification tests were made to

determine the performance of bleanable viscid-impingement 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 specimen filters submitted by the

manufacturer at the request of the Bureau of Ships, and included determinations of the dust-arresting efficiency, pressure drop, specific

dirt load and cleanability of the specimens at three face air velocities, namely 300 , 600 and 900 feet per minute.

II. DESCRIPTION OF THE FILTER SPECIMENS

The two filters submitted were manufactured by the American Air

Filter Company, Inc. of Louisville, Kentucky, and were of the cleanable viscid type, 20x20x2 inches in nominal size. They were identified by their nameplates as Type HV-2 and Type HV-2-16 air filters.

The Type HV-2 filter media was composed of V-crimped, and flat,

strips of 12-mesh screen wire, assembled by piling one alternately on

the other. The resulting media, seen in the direction of air-flow,

appeared to consist of pyramidal pockets each converging to a point

at the other face of the media, with each square pyramid bisected

along a diagonal by the flat screen. There were approximately four

V-crimped layers per inch of pile. The filter had actual outside dimensions of 19-1/2x19-1/2x1-7/3 inches, leaving a free opening

13-3/16x13-1/4 inches (2.31 ft 2 net face area) and weighed 10.2 lb.

when clean, without oil.

The Type HV-2-16 air filter was similar in construction to the

Type HV-2 except that 16-mesh screen wire was used throughout as

media and there was an average of 3.6 V-crimped layers per inch of

pile. The filter had actual outside dimensions of 19-l/2xl9-9/l6x

1-7/$ inches, leaving a free opening 13-1/4 inches square (2.31 ft 2

net face area) and weighed 11.9 lb. when clean, without oil.

2

The manufacturer submitted an adhesive designated as "BA

Viscosine" for oiling both filters. This was done in preparation for the 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 test.

III. TEST METHOD AND PROCEDURE

The dust-arresting 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. S. Dill (ASHVE Transactions, Vol. 44, p.

379, 1932).

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 l+%> and 96/6 by weight,

respectively. The average rate of feed of the contaminants wars 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 mill with 4. mm screen.

The efficiency and dirt-loading tests were made at three different air velocities, namely, 300, 600 and "90’Q 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 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 0.004 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 water 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

-

IV. TEST RESULTS

The pressure drop of the clean oiled filters, in inch

W.G. , at 300, oOO and 900 fptn face air velocity, was measured

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

shown in Table 1.

TABLE 1

Face Velocity, fpm 300 600 900

HV-2

At start of 300 fpm test 0 . 042 .13$ .232

At start of 600 fpm test .043 .141 .239

At start of 900 fpm test .042 .139 .232

After 900 fpm test

cleanings ,$

HV-2-16

.041 .133 .230

Increase in P.D. after 3

At start of 300 fpm test .050 .15$ .322

At start of 600 fpm test .049 .15$ .323

At start of 900 fpm test .050 .163 .342

After 900 fpm test .049 .161 .343

Increase in P.D. after 3 cleanings 9 %

- 2 7

A summary of the test data obtained in dirt-loading tests

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

Table 2, for each of the filters.

- 4

- TABLE 2

Filter Face Air Velocity Dirt Load* Pressure Drop Efficiency

fpm grams/sq.ft inch WG percent

HV-2 300 0 .042

10 .046 44

52 .057 50

90 .069 49 < p > 92 .068 ska)

133 .084 — 182 .103 56

204 .117 55 (P)

207 .115 59(A)

250 .151 61

304 .203 63

332 .243 65 < p > 335 .242 69(A)

388 .363 68

427 .433 75 ( p

)

429 .463 77 (A)

434 .508 80

* Average mixture: 4.2% lint, 95. £% Cottrell precipitate by weight.

Average rate of dirt loading: 15.6 grams per square foot per hour

HV-2 600 0 .141

30 .147 52

75 .202 56

102 .220 59 (p)

108 .224 60(A)

150 .253 59

247 .327 65 < p

)

253 .336 63(A)

269 .353 65

334 .436 - 393 .527 68 ( P

)

399 .564 69(A)

441 ;683 73

469 .839 75

* Average mixture: 4.1% lint, 95.9% Cottrell precipitate by weight.

Average rate of dirt loading: 19.9 grams per square foot per hour.

0 .282 — 26 .302 59

62 .392 60

108 .443 60 ( P)

117 .455 63(A)

162 .518 64

234 .609 65 ( P

)

243 .618 67(A)

325 .762 69

370 .852 75 ( P

)

379 ^884 74(A)

460 1.153 74

478 1.234 76

* Average mixture: 4*0% lint, 96% Cottrell precipitate by weight.

Average rate of dirt loading: 22.5 grams per square foot per hour

- 5 - TABLE 2 - continued

Filter Face Air Velocitv Dirt Load* Pressure Drop Efficiencv

fpm grams/sq.ft. inch WG percent

HV-2-16 300 0 .050 _

3 .050 47

6 .050 45

9 .050 47

69 .07T 52(P)

72 .070 50(A)

136 .100 •57

165 .115 59 ( p)

165 .114 59 (A)

209 .150 62

254 .200 64

270 .225 65(p)

273 .220 65 (A)

290 .262 72

327 .375 77

357 .520 75

* Average mixture: 4.2$ lint, 95.5$ Cottrell precipitate by weight.

Average rate of dirt loading: 15.0 'grams per square foot per hour.

HV-2-16 600 0 .155 — 6 .155 57

12 .162 59

63 .204 57

51 .217 57 ( P)

57 .224 61(A)

129 .255 61

176 .303 — 221 .347 65

p)

227 .349 63 (A)

307 .503 67

363 .715 72 ! P)

369 .719 77(A)

357 .533 77

* Average mixture: 4*0% lint, 96% Cottrell precipitate by weight.

Average rate of dirt loading: 20.4 grams per square foot per hour.

0 .342 — 9 .350 65

15 .357 65

72 .452 — 126 .522 67 < p > 135 .540 67(A)

159 .631 - 252 .749 70

279 .510 75 ( P

255 .530 76(A)

333 .955 - 361 1.103 75

HV-2-16 900

- 6 -

* Average mixture: lint, 96$ Cottrell precipitate by weight.

Average rate of dirt loading: 24.3 grams per square foot per hour.

NOTE: Efficiencies marked (P) or (A) were determinations

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

of the next day of leading, 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 were subjected to increasing specific dirt loading at

face velocities of 300, 600 and 900 feet per minute.

Table 3 presents values of the pressure drop (P.D.), in inches

of water, and of the approximate efficiency ( Eff . ) , in percent, as

taken from the curves of Figure 1 and Figure 2, at various specific

dirt loadings.

TABLE 3

Spec. Dirt Ldg. 0 100 200 300 400

grams/sq.ft. (Initial)

Face Vel'.fpm P.D. Eff. P.D. Eff. P.D. Eff. P.D. Eff. P.D, Eff.

HV-2

300 0,04 44 .07 51 .11 55 .20 63 .40 70

600 .14 .22 59 .29 63 .39 66 .56 69

900 .2$ 59 .43 60 .57 64 .72 67 .96 74

HV-2-16

300 0.05 47 .05 53 .14 61 .29 73

600 . 16 57 .23 61 .32 64 .49 67 — — 900 .34 65 .45 67 .65 69 .57 76 - -

B. Cleanability

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 filter had been subjected to three loadings with the dust-lint

mixture and three cleanings and oilings, the pressure drop of the Type

HV-2 filter was substantially the same as it had been at the start of

the tests. The Type HV-2-16 filter showed a slight increase' in pressure

drop at 900 fpm after its last cleaning, over its original measurement.

This change is within the uncertainty with which the cleaning opera-

- 7 -

tion, which is necessarily involved in the process of ascertaining cleanability , could be performed. It is believed both filters

can be considered as satisfactorily cleanable.

C. General

The fact that efficiencies determined at the end of a day of

loading of the filters (those marked ( P ) in Table 2) were 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”

- 7 -

tion, which is necessarily involved in the process of ascertaining cleanability , could be performed. It is believed both filters

can be considered as satisfactorily cleanable.

C. General

The fact that efficiencies determined at the end of a day of

loading of the filters (those marked (P) in Table 2 ) were 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”

AMERICAN H V - 2

100 200 300 400 500

LOAD, GRAMS PER SQUARE FOOT FIG. I

PRESSURE

DROP,

INCH

WG

EFFICIENCY,

PERCENT

AMERICAN H V - 2 -16

IOO 200 300 40

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

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

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and various consultation and information services. A major portion of the

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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

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Information on the Bureau’s publications can be found in NBS Circular 460,

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

Washington 25, D. C.