NATIONAL BUREAU OF STANDARDS REPORT

615-4

PERFORMANCE TESTS OF

FOUR CLEANABLE IMPINGEMENT AIR FILTERS

TYPE 902, 912, 9.102 and 9802

MANUFACTURED BY

RESEARCH PRODUCTS CORPORATION

MADISON, WISCONSIN

by

Carl W. Coblentz

and

Paul R. Achenbach

Report to

Bureau of Yards and Docks

Office of the Chief of Engineers

Headquarters, U. S. Air Force

Washington, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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national bureau of standards report

ms project rns report

1000-12-4801 September 18, 1958 6154

PERFORMANCE TESTS OF

FOUR CLEANABLE IMPINGEMENT AIR FILTERS

TYPE 902, 912, 9102 and 9802

MANUFACTURED BY

RESEARCH PRODUCTS CORPORATION

MADISON, WISCONSIN

by

Carl W. Coblentz

and

Paul R. Achenbach

Air Conditioning, Heating, and Refrigeration Section

Building Technology Division

to

Bureau of, Yards and Docks

Office of the 'Chief of Engineers

Headquarters, U. S. Air Force

Washington, D„ C.

IMPORTANT NOTICE

NATIONAL BUREAU OF

intended for use wjthln tl to additional evaluation ai listing of this Report, elth the Office of the Director,

however, by the Governrm

to reproduce additional c<

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

or progress accounting documents

5 formally jwbltehad It Is Subjected

isg, reproduction, or open-literature mission is obtained in writing from

C. Such permission is not needed,

ally prepared if that agency wishei

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE TESTS OF FOUR CLEANABLE IMPINGEMENT AIR FILTERS

TYPE 902, 912, 9102 and 9802

by

Carl W. Coblentz and Paul R. Achenbach

1 . Introduction

TLe performance characteristics of a group of cleanable

viscous impingement air filters were measured to provide information for evaluating the relative economy of cleanable

versus throw-away types of filters. " This investigation was

requested by the Defense Department through the Tri-Service

program of research and development at the National Bureau

of Standards to obtain the required data for the preparation

of new air filter specifications.

The test results presented herein were obtained on four

new filters and include determination of the arrestance and

pressure drop as a function of specific dirt load and information on cleanability for face velocities of 36O and

540 ft/min.

2 . Description of Test Specimens

The four test specimens were of the cleanable visdc

impingement type and were manufactured and supplied by t. Research Products Corporation of Madison., Wisconsin. They

were identified as "Industrial Filter" models #902 and

#912 and the "E Z Kleen" models #9102 and #9802. All specimens had outside dimensions of 19 1/2" x 19 1/2” j the

#902 and #9102 were 17/8 In. thick and #912 and #9802 were

7/8 inch thick; the net filter area of all specimen,s was

2.25 sq ft. The nominal thicknesses of 2 in. for filters

#902 and #9102 and 1 in. for filters #912 and #9802 will

be used for discussion purposes in the remainder of this

report

The frames were made of aluminum sheet formed' Into a

U-shaped channel. The aluminum used in the frames of the

Industrial type filters was approximately 0.05 in. thicks

whereas that for the E Z Kleen filters was approximately

0.020 In., thick. The filter media were also made of aluminum sheet which was slit and expanded into a light screen.

Each filter had coarse and fine screens in different numbers. The Industrial types used 0.010 and 0.006 in, thick

sheets and the E Z Kleen types used 0.006 and 0.003 in,

thick sheets; the latter types also had a reinforcing grid

of 0.100 in. aluminum wire made in 4 1/2 In. squares.
.
- 2 -

Adjacent layers of each media were placed so the direction of

expanding the sheets was at right angles in order to deflect

the air flow direction and promote impingement of dust. Prom

10 to 21 layers of expanded aluminum sheet were counted in

each filter.

The adhesive was supplied by the manufacturer, and was

identified by the trade mark #412 Super Filter Coat . It was

claimed that this adhesive would absorb odors, but this characteristic was not investigated during this test.

3. Test Method and Procedure

The performance of the filters was determined at 360

ft/min and 540 ft/min face velocity, i.e., at an air flow

rate of 810 cfm and 1215 cfm, respectively. The clean filters were immersed in the adhesive and left to dry in the

laboratory at least 16 hours before being weighed and installed in the test apparatus. The initial pressure drop

at each air velocity was measured and then the initial

arrestance at the air velocity desired for that test was

determined 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 determinations 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

#7 cotton linters, previously ground in a Wiley mill with

a four-millimeter screen, was fed simultaneously with the

Cottrell precipitate. The pressure drop of the filters was

recorded after each increment of 20 g of dust introduced

into the apparatus. Whereas the arrestance measurements

were tnade 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 the arrestance measurements. Arrestance

determinations were made at the beginning and at the end of

the loading period for each filter and at several intermediate load conditions. The filters were loaded with a

dust concentration of approximately 1 g dust in 1000 cu ft

of air until the pressure drop reached 0.5 in. W.G. in

360 ft/min face velocity tests and 0.8 in. W.G. in the tests

with 540 ft/min face velocity.

After the filters had been loaded to capacity, they were

cleaped with water and allowed to dry; then, oiled again as

previously described, weighed and installed in the test apparatus for determining any change in pressure drop and in

some cases for a new performance test.
» “ '
-3-

4. Test Results

Hie data off pressure drops and arrestancP observed during

the loading tests of the four filters are sumrftanized In

'Tables 1 to 8, inclusive.

Table 1

Performance of Industrial Filter #902(2 in. thick) at

360 ft/min Face Velocity

Load Pressure Drop Arrestance

g/sq ft in . W. G

~~¥~

0 0.060 —

3 0.062 53

7 0.062 53

151 0.152 61

215 0.210 62

266 0.310 65

325 0.495 64

331 0.515 “ —

Table 2

Performance of Industrial Filter #902(2 in. thick) at

540 ft/min Face Velocity

Load Pressure Drop Arrestance

g/sq "ft in. W.G. K> 0 0.146

3 0.149 59

94 0.241 57

139 0.805 58

193 0.439 64

247 0.605 66

283 0.775 70

293 0.815" --

-4-

Table 3

Performance of Industrial Filter #912(1 in. thick) at

360 ft/min Face Velocity

Load Pressure Drop Arrest ance

g/sq ft in . W . G

0 0.040

3 0.041 47

37 0.051 46

63 0.065 48

96 O.O87 50

181 0.165 45

215 0.215 47

274 0.340 52

300 0.424 49

317 O .509 52

Table 4

Performance of Industrial Filter #912(1 in. thick) at

540 ft/min Fade Velocity

Load Pressure Drop Arrestance

g/sq ft in. W.G. %

0 0.087 --

7 0.091 42

52 0.112 40

133 0.175 43

178 0.227 48

268 0.396 51

318 0.536 54

359 0 . 656 60

395 0.900

Table 5

63

Performance of E Z Kleen Filter #9102(2 in.

360 ft/min Face Velocity

thick) at

Load Pressure Drop Arrestance

g/sq ft in. W.G.

0 0.096 --

3 0.100 53

12 0.105 53

54 0.133 57

105 0.181 54

156 0.255 58

207 0.375 64

249 0.530 64

252 0.542 65

-5-

Tab 1 e 6

Performance of E Z Kleen Filter #9102(2

540 ft/min Face Velocity

in. thick) at

Load Pressure Drop Arrestance

g/sq ft in. W . G

~T~

0 0.190 --

3 0.193 56

7 0.195 56

40 0.216 55

103 0.287 61

112 0.305 60

157 0.368 62

202 0.451 61

247 0.605 63

294 0.805 65

298 0.808

Tab 1 e 7

66

Performance of E Z Kleen Filter #9802(1

360 ft/min Face Velocity

in. thick) at

Load Pressure Drop Arrestance

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

0 0.105 —

3 0.106 52

7 0.108 51

54 0.173 54

105 0.291 59

159 0.555

Table 8

62

Performance of E Z Kleen Filter #9802 (l

540 ft/min Face Velocity

in. thick) at

Load Pressure Drop Arrestance

g/sq ft in. W.G.

0 0.235

3 0.235 52

7 0.236 52

58 0.318 50

117 0.490 58

169 0.820 62

- 6 -

The preceding tables show the arrestance values and the

pressure drop as a function of the dirt load per square foot

of net filter area at face velocities of 360 ft/min and 540

ft/min. Pig# 1 to 4 present these same values graphically

using smooth curves to approximately fit the individual points

of observation.

Fig. 1 to 4 show that the arrestance of all four models

increased with increasing dust load, but the rate of increase

in arrestance varied considerably. For example, model 912

showed less than 3^ change in arrestance between the clean

and loaded filter at a face velocity of 360 ft/min, but the

same filter had about 20/ greater arrestance when loaded than

when clean at a face velocity of 540 ft/min. This filter

revealed only a small difference in pressure drop for the

two face velocities throughout most of the lqading period.

The dust loads indicated by these graphs at 0.5 in. W.G.

pressure drop for 360 ft/min face velocity and at 0.8 in. W.G.

for 540 ft/min face velocity have been tabulated in table 9

as "Dust Holding Capacity". Also shown in this table are

the mean arrestance values for each filter and each face

velocity during the period in which the capacity dust load

was being deposited.

Table 9 shows that the average arrestance during the

loading period was nearly the same for each filter at face

velocities of 360 ft/min and 540 ft/min. However, the

arrestance values were somewhat higher for the 2-in. thick

media than for the 1-in. thick media. This difference was

more pronounced in the Industrial type filters than in the

E Z Kleen types. There was no great variation in dustholding capacity between the two face velocities, but the

dust-holding capacity of the 1-in. thick E Z Kleen was

significantly lower than the rest.
,*
-7-

Table 9

Dust Holding Capacity and Mean Arrestance

(Determined from Pigs. 1 to 4)

Industrial Type E Z Kleen Type

Filter Number 902 912 9102 9802

Thickness of Filter, 2 1 2 1

inch

Face Velocity, 360 540 360 540 360 540 360 540

ft/min

Final Pressure Drop, 0.5 0.8 0.5 0.8 0.5 0.8 0.5 0.8

in. W.G.

Dust Holding Capacity, 326 290 316 386 240 294 152 168

grams/ sq ft.

Mean Arrestance, 60 62 48 48 58 61 56 55

percent

The weights of the oiled filters and also the pressure

drop values for both face velocities are shown in table 10

for the filters when new and after each' loading and cleaning

cycle

Table 10

Cleanability of Filters

Type and Condition;, of Filter

Weight

of Filter

grams

Pressure Drop, in.

360 ft/min 540 ft/r

#902

New 1690 0.065 0.140

After 1 loading and cleaning 1902 0.068 0.146

After 2 loadings and cleanings 1887 0.075 0.162

T? ^

It tf H 1908 O.O83 0.183

?? 2| tr !? ?t * 1655 0.060 0.130

* Adhesive mixed with water in ratio of 1:3 instead of

previous ratio of 1:1.

#912

New 1105 0.040 O.O85

After 1 loading and cleaning 1117 0.040 0.087

After 2 loadings and cleanings 1162 0.043 0,099

8 -

Table 10 (cont.)

Type and Condition of Filter

Weight

of Filter

grams

Pressure Drop., in. W.G

360 ft/min 5^0 ft/mi

New

#9102

982 O.O85 0.190

After 1 loading and cleaning — 0.096 0.210

After 2 loadings and cleanings 1065 0.105 0.220

New

#9802

677 0.105 0.235

After 1 loading and cleaning 695 0.106 0.235

After 2 loadings and cleanings 692 0.105 0.238

It will be noticed that the weight and also the pressure

drop of filter type 902 increased considerably during the

first three successive loadings. However^ when a fourth test

was made in which the adhesive was diluted with water in a ratio 1 to 3 instead of 1 to 1 as previously done,, the weight

and pressure drop decreased to values bfelbw those observed

for the new filter. Although the initial pressure drop with

the thinner adhesive was lower,, the dust holding capacity at

its final pressure drop was the same and no change in the

arrestance value was observed.
>' \ T v/;;:
Industrial Filter #902 (2" thick)

v 0 '100 200 300

Dust Load, grams per sq ft

Fig. 1

Dust Load, grains per sq. ft

Dust Load, grams per sq. ft

EZ Kleen Filter jf9&02 (l" thick)

Dust Load, grams per sq ft

U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

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

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