NATIONAL BUREAU OF STANDARDS REPORT

8548

PERFORMANCE TEST OF THE "GLASSAIRE"

GLASS FIBER AUTOMATIC RENEWABLE FILTER MEDIA

manufactured by

Air Filter Sales and Service Co.

of Detroit, Mich.

by

Joseph C. Davis and Paul R. Achenbach

to

Public Buildings Service

General Services Administration

Washington, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assuring

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

421.03-30-4210630 November 10, 1964 8548

PERFORMANCE TEST OF THE "GLASSAIRE"

GLASS FIBER AUTOMATIC RENEWABLE FILTER MEDIA

manufactured by

Air Filter Sales and Service Co.

of Detroit, Mich.

by

Joseph C. Davis and Paul R. Achenbach

Mechanical Systems Section

Building Research Division

Institute of Applied Technology

to

Public Buildings Service

General Services Administration

Washington, D„ C.

IMPORTANT NOTICE NATIONAL BUREAU OF STAN

for use within the Government. Be and review. For this reason, the p whole or in part, is not authorize Bureau of Standards, Washington

the Report has been specifically pr

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

accounting documents intended

bjected to additional evaluation

sting of this Report, either in

)ffice of the Director, National

e Government agency for which

es for its own use.

11. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE TEST

OF THE

"GLASSAIRE" GLASS FIBER AUTOMATIC RENEWABLE

FILTER MEDIA

manufactured by

Air Filter Sales and Service Co.

of Detroit, Mich.

by

Joseph C. Davis and Paul R. Achenbach

1 . Introduction

At the request of the Public Buildings Service, General Services

Administration, the performance characteristics of the "Glassaire"

glass fiber roll-type filter media, manufactured by the Air Filter

Sales and Service Co. of Detroit, Michigan, were determined. The

scope of the investigation included the determination of the ar res- tance of Cottrell precipitate diffused into the laboratory air, and

the dust-holding capacity when the face velocity was maintained at

500 ft/min. and while the media was intermittently advanced with a maximum setting for the pressure drop across the media of 0.5 in.

W.G.

2 . Description of Test Specimen

The roll of media was supplied for test purposes by the Air

Filter Sales and Service Co. of Detroit, Michigan. The glass fiber

media, according to the manufacturer, had been purchased from the

American Air Filter Co. and had been treated with tricresylphosphate

in the jell form. The media was white in color and was 36 in. wide

by 65 ft. long and was nominally 2 in. thick. A high density backing was bonded to the downstream side of the material to provide a relatively high tensile strength and to minimize breakage of the media on the roll during service. Microscopic examination of the fibers in

the main body indicated that they were between 4 and 7 microns in

diameter. Their length ranged from 3 to 8 in. Microscopic examination of the fibers in the higher density backing indicated that they

were between 4 and 20 microns in diameter. Their length ranged from

about 5 in. to about 12 in. The approximate unit weight was 37 g/ft^.

The results of an infrared analysis showed that the adhesive was tricresylphosphate as claimed by the manufacturer.

After the test had been performed, an evaluation was made of the

unit weight of the tricresylphosphate in the media. Three determinations were made with the use of a Soxlett Extractor with absolute

- 1-
grade ethyl alcohol as the solvent. For each determination, a sample

of the media, 2x6 in. in area, was used. A white flocculent material which precipitated out during the process was removed by filtering through No. 41 Whatman filter paper. An average of the three

determinations for unit weight of tricresylphosphate was 21 g/ft^.

3 . Test Methods and Procedure

The medium was tested at a net face velocity of 500 ft/min.

The arrestance determinations were made with the "NBS Dust Spot

Method for Air Filters" (ASHVE Transactions, Vol. 44, p. 379, 1938).

For the test, the roll of media was installed in a roll-filter frame

constructed to fit the NBS test apparatus. This apparatus provided

an air-tight enclosure and adapters to fit the upstream and downstream

sections of the test duct. This roll-filter frame has been used previously for testing various media of this type.

The frame had two openings, 2 ft x 2 ft, one upstream and the

other downstream from the filter. The roll of filter media was placed

at the top of the frame on a spool and arranged so the media passed

immediately behind the downstream opening as it unrolled. The expended

media was rolled up on a similar spool at the bottom of the frame. The

bottom spool was driven by a motor actuated by a manually operated

switch when the pressure drop across the media reached o.5 in. W.G.

Nine vertical bars in the downstream opening served to prevent appreciable deflection of the media under the influence of the air pressure

difference. The edges of the media were supported in metal channels

to restrict by-pass of air between the media and frame.

The frame and Glassaire media were installed in the dust spot

test apparatus and carefully sealed to prevent any by-pass of air or inward flow into the test apparatus, except through the measuring

orifice. After establishing the correct air flow rate through the

filter, 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 area of Whatman No. 41 filter

paper. The arrestance determinations were made with Cottrell precipitate injected into the air stream at a ratio of one gram per 1,000 cu. ft. of air.

The light transmission of the sampling papers was measured before

and after the test on the same area of each paper, and the two sampling

papers used for any one arrestance determination were selected to have

the same light transmission when clean.

For determining the arrestance of the filter, different size areas of sampling paper were exposed upstream and downstream of the

filter in order to obtain a similar increase of opacity on the two

- 2-
sampling papers. The arrestance was calculated by the formula:

, S n AD, a = a - x x 100

where the symbo Is Sjj and Sjj are the upstream and downstream sampling

areas and AU and AD are the observed changes in the opacity of the

upstream and downstream sampling papers, respectively.

Arrestance determinations were made when the media was clean at

the beginning of the test, and at selected intervals of loading until

the intermittent advance of the media became representative of a steady

state operation. The arrestance determinations were made with Cottrell

precipitate only, while cotton 1 inters were added during the loading

process in a ratio of 4 parts to every 96 parts of Cottrell precipitate, including the Cottrell precipitate used for arres tance—measurements. The Cottrell precipitate had been previously sifted through a 100-mesh screen and the lint was prepared by grinding No. 7 cotton

linters through a Wiley mill with a 4-millimeter screen.

The advance of the filter media was observed through a window in

the test apparatus by determining the position of a marker, attached

to the mat, relative to a yardstick mounted in the filter housing,

adjacent to the mat. A pilot light connected in parallel with the

electric motor enabled the operator to note the position of the media

and to record the pressure drop across the medium at the beginning

and at the end of each advance cycle. The advance cycle, actuated by

the manually operated switch, was initiated when the pressure drop across the filter reached approximately 0.50 in. W.G. and was stopped

when the drop was about 0.454 in. W.G.

The position of the media at the beginning of each advance cycle was recorded as well as the corresponding cumulative dust load at the

time of advance. From this information a plot was made of the advance

of the media Vs. dust load, and when the relation between the two

parameters became very nearly linear, ten more determinations of ad- vance as related to load were made. The dust-holding capacity in

grams/ft- was then determined by drawing the best-fitting straight

line through the last eleven determinations.

The pressure drop across the media was recorded at the beginning

of the test, after each arrestance determination, after introduction

of each 20-gram increment of Cottrell precipitate and lint into the

test duct, and at the beginning and end of each advance cycle.

- 3

-
4. Test Res ults

The test results obtained on the "Glassaire" media at the air

flow rate of 2000 cfm are summarized in Tables 1 and 2.

TABLE 1

Performance of the "Glassaire" Roll Filter Media

At an Air Flow Rate of 2000 CFM

Cumulative

Dust Load

Total Advance

of Media

Pressure

Drop Arrestance*

grams inches in. W.G. per cent

0 0 0.162 74,2

1236 23.25 0.452 84.1

1406 28.50 0.454 84.2

1489 31.00 0.504 86.9

1489 31.00 0.452 84.5

1631 35 . 50 0.500 85.0

1698 37.25 0.504 85.1

1698 37.25 0.542 84.2

1761 39.25 0.450 85.0

* Cottrell precipitate in the laboratory air

It will be noted that the arrestance of the clean filter media was 74.2 percent and the average arrestance under steady-state con- ditions was 84.9% using Cottrell precipitate in the laboratory air

as the aerosol.

- 4

“
TABLE 2

Dust Load, Mat Travel, and Pressure Drop

of "Glassaire" Glass Fiber Media

Dust Load Mat Travel Pressure Drop, In. W.G,

grams inches

Advance Total

After

Advance

Before

Advance

0 0 0 .162 --

1007 -- 17.25 .453 .502

1090 2.25 19.50 .456 .502

1153 2.25 21.75 .450 .504

1236 1.50 23.25 .452 .498

1319 2.50 25.75 .450 .506

1406 2.75 28.50 .454 .502

1489 2.50 31.00 .452 .504

1568 2.00 33.00 .454 .504

1631 2.50 35.50 .470 .500

1698 1.75 37.25 .452 .504

1761 2.00 39.25 .450 .504

The first movement of the media was approximately 4 inches and

occurred with a dust load of 522 grams and at a pressure drop of

0.530 in. W.G. Steady-state conditions were indicated when the

media had advanced 17.25 in. and when the dust load was 1007 grams.

The pressure drop at this point was 0.453 in. W.G. Under steadystate conditions the pressure drop before advance ranged from

0.498 to 0.504 in. W.G. with an average 0.503 in. W. G. , and after

advance the pressure drop ranged from 0.450 to 0.470 in. W.G. with

an average of 0.45 in. W.G.

The graph of Figure 1 shows the performance of the media for

the 11 observations taken after steady-state observations were es- tablished. It will be noted that some of the individual points of

[

- 5

-
observation do not lie exactly on the straight line. These deviations occurred partly because the advance distance could be observed

on the scale only to the nearest quarter-inch mark, and because the

manually-operated switch was not opened or closed at exactly the same respective pressure drop each time. Based on the best-fitted straight

line through the observed data in figure 1, it is shown that after

17 inches of mat travel, the dus

t

A was 1000 grams, and after 40 in.

of travel, the dust load was 1800 grams. Thus, a mat travel of 23

inches was caused by the introduction of 800 grams of dust. The

dust-holding capacity of the media was calculated by dividing the

dust load increment by the total advance in feet during the corres- ponding loading period and by the width of the media.

300 12 Dust-holding capacity = x = 209 g/sq ft

The average performance values determined for the test specimen

were 84.9 percent arrestance and 209 g/sq ft dust-holding capacity.

The current requirements specified for the Type E media are 75 percent average arrestance and 200 g/sq ft dust-holding capacity using

Cottrell precipitate as the test dust.

- 6-
MAT

TRAVEL,

INCHES

MAT TRAVEL VERSUS DUST LOAD

AIR FILTER SALES AND SERVICE CO

RENEWABLE FILTER MEDIA

1000 1800

DUST LOAD (GRAMS)

Figure 1