NATIONAL BUREAU OF STANDARDS REPORT

PERFORMANCE TESTS OF AN AUTOMATIC

RENEWABLE MEDIA AIR FILTER

ROLL-KLEEN, MODEL 3-70

manufactured by

Farr Company, Los Angeles, California

Carl W, Coblentz and Paul R. Achenbach

Report to

Public Buildings Service

General Services Administration

Washington 25 j L. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

6922
TUK NATIONAL HUKLAD OF STANDAMDS

Fimrlions ami Arlivilics

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national bureau of standards report

NBS PROJECT NBS REPORT

1003-30-10630 August 4 , i960 6922

PERFORMANCE TESTS OF AN AUTOMATIC

RENEWABLE MEDIA AIR FILTER

ROLL-KLEEN, MODEL 3-70

manufactured by

Farr Company. Los Angeles^ California

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 25 ^ D. C.

IMPORTANT NOTICE

NATIONAL BUREAU OF

intended for use yvithin tl to additional evaluation an

listing f.f this Report, eithi the Office of the Director,

i'.ov.'ever, by the Governme

to reproduce additional co

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

r progress accounting documents

formally published it is subjected

ig, reproduction, or open-literature

lission is obtained in writing from

. Such permission is not needed,

ly prepared if that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE TESTS OP AN AUTOMATIC

RENEWABLE MEDIA AIR FILTER

ROLL-KLEEN, MODEL 3-70

manufactured byFarr Company^ Los Angeles^ California

by

C. W. Coblentz and P. R. Achenbach

I . Int roductlon

At the request of the Public Buildings Service^ General

Services Administration^ the performance characteristics of

an automatic renewable media air filter were determined. The

scope of this examination included the determination of the

arrestances of the particulate matter in the laboratory air

and Cottrell precipitate^ at the rated air flow rate of the

device^ and at air flow rates 20 percent above and below this

rate; it included-,, further^ the observation of the pressure

drop^ the autom.atic advancement of the filter medium^ and

the determination of the dust-holding capacity of the filter

medium

.

2 . Description of Test Specimen

•The test specimen was manufactured and supplied for test

purposes by the Parr Company of Los Angeles^ California. It

was identified as their Roll-Kleen Model 3-70. The filter

medium reported on. was the fourth such roll supplied by the

manufacturer since the performance of the earlier mats did

not meet applicable Government applications with regard to

either arrestance or dust-holding capacity.

jf The filter medium was a glass fiber mat about 1 1/2”

thick and reinforced on the downstream side by a rigid webbing. The glass fibers appeared to be bonded by an organic

fibrous material and were covered with an adhesive. The mat

was supplied in a 3-ft wide roll, compressed to approximately

1/2 in. thickness. The clean roll was suspended in the upper

part of the housing and, after passing the 24 in. square air

flow opening, was rolled up on another spool at the bottom

of the housing by an electric motor. While passing from the

clean roll at the top of the housing to the bottom roll, the

medium was backed up by a stationary grid that prevented excessive deflection of the filter mat as it passed across the

air flow opening. The electric motor was controlled by a
•ASJ

'tf-

. i-.

r

T

•'M'' *" ''
1/

- 2 -

pressure switch. General Controls Type L-48A. This pressure

switch started the motor, l.e., the advance mechanism, when

a certain pressure drop across the filter medium was reached

This pressure drop could be selected in a wide range, whereas, the differential of about 0.07 in. W.G was fixed.

3 . Test Method and Procedure

The arrestance measurements were made in accordance with

the MBS ’’Dust Spot Method” described in a paper by R. S. Dill

and entitled, ”A Test Method for Air Filters” (ASHVE Transactions, Vol. 44, p. 379j. 1938 ).

For test purposes, the housing with the filter media in

place was installed in the test apparatus and carefully sealed

to prevent inward leakage of air except through the measuring

orifice. The desired rate of air flow through the filter was

established and samples of air were drawn from, the center

points of the test duct two feet upstream and eight feet downstream of the test specimen at equal rates and passed through

known areas of Whatman No. 4l filter paper. The change of the

opacity of these areas was determined with a sensitive photometer which measured the light transm.lsslon of the same spot

on each sampling paper before and after the test. The two

sampling papers used for each test were selected to have the

sam.e light transmission readings when clean.

For determining the arrestance of the filter, with Cottrell precipitate as the test dust, different size areas of

sampling papers were used upstream, and downstream, of the filter in order to obtain a similar increase of opacity on both

sampling papers. The arrestance A (in percent), was then calculated by the f orm.ula : A=.[l-_^ X ^)x 100

V su Au y

where Su and Sp were the upstream and downstream sampling areas

and AU and AD the observed changes in the opacity of the upstream and downstream sampling papers, respectively.

For determining the arrestance of the particulate matter

in the laboratory air, equal sampling areas were used for the

upstream and downstream samplers. A similar Increase of the

opacity of the upstream and downstream filter papers was
'jm \

1

r

iiir.
-3-

obtained by passing the sampling air through the upstream paper

only part of the time while operating the downstream sampler

continuously. This was accomplished by installing one solenoid

valve in the upstream sampling line and another one in a bypass line. The valves were operated by an electric timer and

a relay so that one was open while the other one was closed

during any desired percentage of the 5-mlnute timer cycle^ reversing the position of the two valves during the remainder

of the cycle. The arrestance^, A (in percent was then determined with the following formula:

A = 100 - T X ^

AU

where T is the percentage of time during which air was drawn

through the upstream sampler^ AU and AD being the changes of

opacity of the sampling papers^ as previously indicated.

The pressure drop of an automatic self-cleaning air filter of this type Increases during operation due to the accumulating dust load until it reaches the value at which the

pressure switch is set to operate the advance mechanism. Wxhen

the clean media is moved into the air stream^ the pressure

drop decreases until the pressure switch stops the advance

mechanism. The filter then operates repetitively in the onoff range of the pressure switch^ the pressure differential

controlling the length of the clean blanket that is moved

into the air stream and the rate of dust accumulation determining the frequency of the cycles. The operation of this

type of filter at a higher average pressure drop will increase

the dust load per unit area of the filter medium. This saving

on filter material^ however^ tends to be offset by the Increase

of the required blower power. The maximum pressure drop of

slightly below 0,5 in. W.G. selected for this test corresponds

to comm.on operating practice for this type of filter.

The following procedure was used for determining the performance of the test specimen. After the filter assembly^

with the new mat in place^ had been Installed in the test

apparatus^ the pressure drop of the clean blanket was determined at the rated face velocity of 500 ft/mln^ i.e., at an

air flow rate of 2000 cfm, and also at velocities of 20 percent above and below this value. To determine the uniformity

of the filter mat;, the blanket was then advanced approximately

4 feet and the above pressure drop measurements were repeated.

Thereafter^ several determinations of the arrestance were made
V
_ 4 -

wlth the particulate matter In the laboratory air as the aerosolj followed by arrestance determinations with Cottrell precipitate .

At the request of the manufacturer's representative^ who

attended the test^ some of these arrestance measurements were

made with Diglass filters Instead of Whatman paper. No significant difference in the arrestance value could be established^ using these two papers for collecting the sample. It

had been assumed that the differences in performance of previous filter mats observed at this Bureau and at the manufacturer's plant were the result of using different sampling

paper,.

After these arrestance determinations were made^ the

loading of the filter with a mixture of 96 parts by weight of

Cottrell precipitate and 4 parts of lint was started. The

Cottrell precipitate had been sifted previously through a 100-mesh screen and was dispersed into the test apparatus in

a ratio of 1 gram per 1000 cu ft of air. The lint was introduced into the air stream separately and had been prepared

by grinding No. 7 cotton linters through a Wiley mill with

a 4 mllllm.eter screen.

After the blanket had advanced several steps^ the arrestance determinations with both aerosols were repeated.

The distance of each advance of the filter media was observed

by means of small markers fastened to the mat. These markers

moved alongside a yardstick mounted in the filter housing and

could be observed through a glass window in the test duct.

A pilot light was Installed parallel with the advance motor

and enabled the operator to record 'the pressure drop of the

filter mat. Altogether^ a total of 20 advance cycles was

observed during which the blanket moved 49 Inches. At the

term.lnatlon of the test, a group of arrestance determinations

with Cottrell precipitate were conducted at face velocities

20 percent above and below the rated air flow of the specimen. A total of 21 arrestance determinations were made during

the test.

4 . Test Results

The test results are summarized in Tables 1 and 2.

Table 1 shows the observed values for dust load and the

average arrestance values at certain positions of the filter

mat using the particulate matter in the laboratory air or

Cottrell precipitate, at the rated air flow and at values

20 percent above and below the rated flow.

- 5

-

Table 1

Summary of Arrestance Determinations

Roll-Kleen Model 3-70

Dust Load Air Plow Rate Advance of Mat Arrestance Aerosol

g/ft width cfm in

.

%

*

0 2000 0 16 A

15 2000 0 70 C

312 2000 16 79 C

570 2000 32 81 C

730 2000 46 1/2 82 C

736 2000 46 1/2 20 A

748 1600 46 1/2 85 C

760 2400 46 1/2 80 C

* Aerosol A - Particulate matter in the laboratory air.

Aerosol C - Cottrell precipitate in the laboratory air.

NOTE: Each arrestance value presents the average of two or

more individual arrestance determinations.

The dust load is reported in grams per foot widths referring to the 2 -ft square air flow opening. At the end of the

test, a total of 1532 grams of dust and lint had been introduced into the test apparatus,, and no fallout was determined

in the upstream portion of the duct so that the full amount

had reached the filter.

The arrestance of the particulate matter in the laboratory air with a clean filter medium was observed to average

16 percent based on 3 tests. The arrestance of Cottrell precipitate for the clean filter was 70 percent, which is the

average of 4 individual arrestance determinations which ranged

from 69.2 to 71,9^.

It will be noted that the arrestance of Cottrell precipitate was 79^ when the filter mat had moved I6 in. but varied

between 8l and 82^ after a 32-ln. movement of the filter medium at rated face velocity. Steady state arrestance of Cottrell precipitate was approximately 8l^, and of the particulate matter in the laboratory air, about 20^, at the I’ated

flow. The arrestance of Cottrell precipitate increased to

85^ when the air flow rate was reduced by 20^, and decreased

to 80^ when the air flow rate was increased by 20^.

- 6 -

The dust load^ and pressure drop before and after each

advance of the filter medium,, together with the Incremental

and total mat travel are shown In Table 2 for the entire

test period.

Table 2

Mat Travel, Dust Load and Pressure Drop

Roll-Kleen Model 3-70

at Rated Face Velocity of 500 ft/mln

Dust Load

g/ft width

Travel of

Advance

Mat, In.

Total

Pressure Drop

Before Advance

, In. W.G.

After Advanc

0 0.170

213 5 5 0.495 0.420

240 3 8 0.460 0.400

271 2 10 0.460 0.400

302 3 13 0.495 0.420

334 3 16 0.495 0.415

365 2 18 0.485 0.410

386 2 20 0.500 0.440

417 2 1/2 22 1/2 0.500 0.420

448 2 24 1/2 0.495 0.420

469 2 1/2 27 0.495 0.420

490 2 1/2 29 1/2 0.490 0.415

521 2 1/2 32 0.495 0.420

531 2 34 0.495 0.420

562 2 36 0.495 0.430

593 2 38 0.500 0.430

6l4 2 40 0.495 0.425

645 2 1/2 42 1/2 0.495 0.420

674 2 44 1/2 0.485 0.425

696 2 46 1/2 0.490 0.425

729 2 1/2 49 0.495 0.420

The pressure drop of two sections of the clean filter

mat, 4 feet apart on the roll Is shown In Table 3- It Indicates a variation of about 5^ in the pressure drop for two

sections of the blanket 4 feet apart.

-7-

Table 3

Uniformity of Filter Medium

Roll-Kleen Model 3-70

Flow Rate Face Velocity Pressure Drop,, In. W.G.

cfm ft/min 1, Section 4 ft Further

2400 600 0.218 0.230

2000 500 0.160 0.170

1600 400 0.115 0.120

The dust load values shown in Tables 1 and 3 a^?e the cumulative weights of Cottrell precipitate and lint that had been

introduced into the test apparatus at the beginning of each

advance of the filter medium. With the exception of the first

advance cycle^ the blanket advanced between 2 and 3 in. for

each step. The individual advance could not be observed much

closer than ± 1/2 in. and it can be assumed^ therefore^ that

the advance distance was practically the same for each step

after the first 16 Inches of mat travel. The average pressure

drop before the advance was 0.491 in. W.G.^ with a maximum

value of 0.500 and a minimum of 0.460 in. W.G.^ whereas^ the

pressure drop at the termination of the advance cycle averaged

0.420 in. W.G.j with a maximum value of 0.440 and a minimum of

0.400 in. W.G.

The amount of Cottrell precipitate collected on a unit

area of filter medium during the steady state operation of

the test specimen provides a measure of the consumption of

mat length during actual use. Disregarding the insignificant

mass of particulate matter collected on the filter during the

arrestance determinations with laboratory alr^ the dustholding capacity per unit area at rated air flow is expressed

by the slope of the straight line in Fig. 1. This line was

drawn to approximate the least mean square distances of the

points of observation. According to this llne^ there were

750 - 250 = 500 grams per foot width of dust received by the

filter m.at while the filter mat traveled from the 8 . 7 - to the

51 . 5 -inch position^ a distance of 42.8 inches,, or 3.57 ft.

Therefore,, the dust-holding capacity was 500 ^ pijo grams

3.57

per square foot. Table 4 below presents a summary of the

performance data for this filter.

-8

Table 4

Summary of Test Results

Pressure Drop,, clean

at 600 ft/mln Face Velocity - 0,230 in. W.G.

at 500 ft/min Face Velocity - O.I7 O in, W.G.

at 400 ft/min Face Velocity - 0.120 in. W.G.

Average Operating Pressure* - 0.,491 in. W.G, to 0.420 in. W.G.

Average Arrestance*

Clean Mat,, Laboratory Air - 16/

Cottrell Precipitate - 70/

Steady State^, Laboratory Air - 20/

Cottrell Precipitate - 81/

Arrestance at Steady State with Cottrell Precipitate

at 600 ft/mln Face Velocity - 80/

at 400 ft/min Face Velocity - 85/

Dust-Holding Capacity* - l40 g/ft width

* At rated face velocity of 5 OO ft/mln.

USCOMM-NBS-DC

MAT TRAVEL v/s DUST LOAD

U.S. DEPARTMl'NT OF COMMICHCE

Frederick U. Mueller, Secretary NATIONAI, bureau OF STANDARDS

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

TIic scope of activities of tiie National Bureau of Standards at its major laltoratories in Wasliinplon. D.C., and

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In general, each section carries out specialized research, development, and engineering in ihe field indicated hy

its title. A brief description of the activities, and of the resultant publications, appears on tlu^ inside of the front cover. WASHINGTON, D.C.

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Optics and Metrology. Photometry and Colorimetry. Photographic Technology. I.ength. Engineering

Metrology.

Heat, Temperature Physics. Thermodynamics. Cryogenic Ph)8ics. Rheology. Molecular Kinetics. Free Radicals Research. Atomic and R.^diation Physics. Spcclrosco[)y. Hadiomelr)'. Mass Spcctromelry. Solid Stale I’hysics. Electron Phvsics. Atomic Physics. Neutron Physics. Radiation d'hcory. Radioactivity. X-rays. High

Energy Radiation. Nucleonic Instrumentation. Radiological l*]quipinent.

Chemistry, flrganic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry. Inorganic

Chemistry. I'dccirodeposition. Molecular .Structure and Properties ol (hises. Physical (ihemistry. d’hermochetnistry. .Spcctrociiemislry . Pure Substances.

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Organic and Fihrons Alatcrials. Rubber. Textih's. Paper. Leather, d’esling and S|)ecilicatious. Poly- m<w Structure. Plastics. Dental Research.

Metallnrgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion. Metal

Physics.

Mineral Products. Faigineering Ceramics. Glass. Refractories. Enameled Metals. (Jonsliliition anti Microstructure.

Building Technology. Strueliiral ICngineering. F^ire Protection. Air Conditioning, Healing, and Refrigt^ation. Floor, Roof, and Wall Coverings. Codes and Safely Standards. Hrtal 1’ransfer. Concreting Materials.

Ap]»iied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics.

Data Proce.ssing .‘systems. SIlAC Engineering Group. Components and Techniques. Digital Circuitry.

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• OlTice of Basic. Instrumentation. • Office of Weights and Measures. BOULDER, COLORADO

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I J