NATIONAL BUREAU OF STANDARDS REPORT

PERFORMANCE TEST OF A FOLDING AEROSOLVE

MODEL 3H-85 AIR FILTER

Manufactured by

Cambridge Filter Corporation

Syracuse,, New York

C. W. Coblentz and P. R. Achenbach

Report to

Public Buildings Service

General Services Administration

Washington 25 , D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

7396
THE NATIONAL BUREAU OF STANDARDS

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The (unctions 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

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July 1957 to June 1960 (Includes Titles of Papers Published in Outside Journals 1950 to 1959) (S2. 25); avail- able from the Superintendent of Documents, Government Printing Office, Washington 25, D. C.
NATIONAL BUREAU OF STANDARDS REPORT

PERFORMANCE TEST OF A FOLDING AEROSOLVE

MODEL 3H-8.5 AIR FILTER

Manufactured by

Cambridge Filter Corporation

Syracuse, New York

C, W. Coblentz and P. R. Achenbach

Mechanical Systems Section

Building Research Division

NBS PROJECT

1003 - 30-10630 January 5, 1962

NBS REPORT

7396

by

to

Public Buildings Service

General Services Administration

Washington 25* D. C.

IMPORTANT NOTICE

NATIONAL BUREAU OF STANI

intended for use within the Go\

to additional evaluation and revi listing of this Report, either in v the Office of the Director, Natio however, by the Government agi to reproduce additional copies f

Approved for public release by the published it is subjected

oj \- f/vMMuoiuii 10 ) 1 u i necucUi on October 9, 2015. pared that agency wishes

ress accounting documents

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE TEST OF A FOLDING AEROSOLVE

MODEL 3H-85 AIR FILTER

Manufactured by

Cambridge Filter Corporation

Syracuse,, New York

by

C. W. Coblentz and P. R. Achenbach

1. INTRODUCTION

At the request of the Public Buildings Service., General

Services Administration, the performance characteristics of

the Aerosolve Model 3 H-85 air filter were determined. The

scope of this examination included the determination of the

arrestance of particulate matter in the laboratory air, the

pressure drop and the dust-holding capacity of the filter at

the rated air flow rate of 1,000 cfm.

2. DESCRIPTION OF TEST SPECIMEN

The test specimen was manufactured and supplied for test

purposes by the Cambridge Filter Corporation of Syracuse, New

Yo rk 0 The filter medium was a mat, approximately one quarter

inch thick, made of glass fibers „ A microscopic examination

indicated a rather uniform fiber diameter of somewhat below

one micron and an average fiber length on the order of two

mm. The dry filter medium was supported by a smooth, thin

sheet of glass fibers on the downstream side. The filter

mat with its backing was formed into twelve one foot deep

pleats and was cemented into a collapsible frame 24 inches

square and 12 inches deep. Two opposite sides of the frame

were rigid and the others were made of flexible plastic

sheet. The filter cartridge was shipped in a folded or

collapsed condition. The cartridge was expanded to its

normal shape and size by pulling apart the two rigid sides.

It could then be easily installed into the supporting steel

wire frame, model 4H-1000. The total area of the medium was

approximately 44 sq ft.
- 2 -

3. TEST METHOD AND PROCEDURE

The filter was tested at the rated air flow rate of 1,000

cfm corresponding to a face velocity of 250 ft/min. The arrestance determinations were made with the NBS Dust Spot Method

described in a paper by R. S. Dill entitled "A Test Method for

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

filter under test was installed in the test apparatus and carefully sealed to prevent any by-pass of air or inward leakage

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 2 feet upstream and 8 feet downstream of the test

specimen at equal rates and passed through known areas of Whatman No. 4l filter paper. The arrestance determinations were

made with the particulate matter in the laboratory air as the

aerosol

.

The light transmission of the sampling papers was measured

on the same area of each paper before and after the test 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 particulate matter

in the laboratory air, equal sampling areas were used in the upstream and downstream samplers. A similar increase of the opacity of the two sampling papers was obtained by passing the

sampling air only part of the time through the upstream paper

while operating the downstream sampler continuously. This was

accomplished by installing one solenoid valve in the upstream

sampling line and another one in a bleed line by-passing the

sampler. The solenoid 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~minute 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 formula:

A = 100 - T x —AU

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

through the upstream sampler, and AU and AD are the observed

changes in the opacity of the upstream and downstream sampling

paper, respectively.
-3-

Arrestance determinations were made at the beginning and

at the end of the test and at several intermediate loading

conditions. The filter was loaded with Cottrell precipitate

to which cotton linters were added in a ratio of 4 parts to

every 96 parts of Cottrell precipitate. 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 pressure drop across the filter under test was recorded at the beginning of the test., after each arrestance determination., and after every 20-gram increment of Cottrell precipitate that was introduced into the test duct. The tests were

terminated when the pressure drop across the test specimen

reached 0.8 in. W.G.

4 . TEST RESULTS

A summary of the test results is presented in Table 1.

Table 1

Performance of Cambridge Model 3 H-85

Dust Load

g

Pressure Drop

in. W.G.

Arrestance

%

0 0.254

161 0.283

363 0.329

564 0.428

765 0.630

846 0.757

886 0.833

76.8

89.8

90.3

89.8

91.2

The "Dust Load" shown in this table is the amount of Cottrell precipitate and lint received by the filter. It is the

weight of dust introduced into the test apparatus diminished

by the amount of dust fallout upstream of the filter. The

percentage of dust fallout was determined from the ratio of

the weight of the dust that was swept out of the front section of the test duct at the conclusion of the test to the

total amount of dust introduced.
-lilt will be noted that the arrestance of the filter increased

from an initial value of 76.8 percent with a pressure drop of

0.254 in. W.G. to a value of 91.2 percent after 846 grams of dust

had been received by the filter and the pressure drop had

increased to 0.757 in. W.G.

Figure 1 presents a graph of the values shown in Table 1

with smooth curves approximating the line of the least mean

square distances from the points of observation.

A filter of this type is usually operated until its pressure drop has increased by 0.5 in. W.G. The dust-holding capacity, then, is the amount of the dust that has produced this

pressure drop., With an initial pressure drop of 0.254 in. W.G.

approximately 840 grams of dust had been received by the test

specimen when the pressure drop reached 0.754 in. W.G. The

average arrestance of approximately 88 percent is, then, indicated as an imaginary horizontal line which encloses equal areas

below and above the arrestance curve in figure 1.

USCOMM-NBS-DC
Cambridge Model 3H-85

Dust Load,, grams

II. S. DEPARTMENT OF COMMERCE

Luther H. Hodges, iec/c.Cary NATIONAL BUREAU OF STANDARDS

A. V. Aatin, Director

THE NATIONAL BUREAU OF STANDARDS

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