NATIONAL BUREAU OF STANDARDS REPORT

7597

PERFORMANCE TEST OF THE FILTREX TYPE GFC-3

AUTOMATIC RENEWABLE AIR FILTER MEDIA

manufactured by

Drico Industrial Corporation

Passaic,, New Jersey

Carl W. Coblentz and Paul R. Achenbach

Report to

Bureau of Facilities

Post Office Department

Washington, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

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national bureau m iminiii report

MBS PROJECT '

_ MBS REPORT

1003-30-10630 August 23, 1962 7597

PERFORMANCE TEST OF THE FILTREX TYPE GFC-3

AUTOMATIC RENEWABLE AIR FILTER MEDIA

manufactured by

Drlco Industrial Corporation

Passaic, New Jersey

by

Carl W. Coblentz and Paul R. Achenbach

Mechanical Systems Section

Building Research Division

to

Bureau of Facilities

Post Office Department

Washington, D. C.

NATIONAL BUREAU OF f Intended for use within th to additional evaluation an

listing of this Report, elthi the Office of the Director, however, by the Governme

to reproduce additional co t

IMPORTANT NOTICE

progress accounting documents Approved for public release by the formally published It is subjected

Director of the National Institute of f' reproduction, or open-literature c . , , , , , /xTTOT^ lssion is obtained in writing from Standards and Technology (NIST) Such permi88lon is not needed, on October 9, 2015. ly prepared If that agency wishes

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PERFORMANCE TEST OF THE FILTREX TYPE GFC-3

AUTOMATIC RENEWABLE AIR FILTER MEDIA

manufactured by

Drico Industrial Corporation

Passaic, New Jersey

by

Carl W. Coblentz and Paul R. Achenbach

1

Introduction

At the request of the Post Office Department, Bureau of Facilities, the performance characteristics of two specimen rolls of

the Filtrex type GFC-3 automatic renewable air filter media was

determined. The scope of this examination included the determination of the arrestance and the dust-holding capacity of the

media operated at a face velocity of 500 ft/min and at a pressure drop not exceeding 0.5 in. W. G. The performance of the

media was observed using Cottrell precipitate only as the

aerosol

,

2.

Description of Test Specimen

The two rolls of media were manufactured and supplied by the

Drico Industrial Corporation of Passaic, New Jersey, and were

identified as their Filtrex type GFC-3 automatic renewable air

filter media. The media were supplied in rolls 3 ft wide and

approximately 65 ft long and were made of glass fiber. The

fiber mat was about 2 in. thick when it expanded after unrolling and it was noticeably less dense at the upstream face

of the mat than at the downstream side. The fibers appeared

to be bonded with an organic binder and were treated with an

oily adhesive. A microscopic examination of the fibers indicated that most of them were between 30 and 50 microns in

diameter and several inches long.

3

Test Method and Procedure

The media were tested at the rated face velocity of 500 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. 37SL

1938). The two rolls of media were installed in turn in a
-2

"Conomatic" roll-filter frame manufactured by Continental Air

.Filters., Inc., of Louisville, Kentucky, for the test. This

mechanism was modified for use with the National Bureau of

Standards air filter test apparatus by providing it with an

air-tight enclosure and adapters to fit the upstream and downstream sections of the test duct. This roll-filter frame had

been used previously for testing the manufacturer's own media

and was representative of the apparatus used for this type of

media. The Conomatic frame equipped with the Filtrex media

was installed in the test apparatus and carefully sealed to

prevent any bypass 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 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 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 used upstream and downstream of

the filter in order to obtain a similar increase of opacity

on the two sampling papers. The arrestance was then calculated by the formula:

S D AD

A = (l - — x —) x 100

Sy AU

where the symbols Sy and are the upstream and downstream

sampling areas and AU and AD are the observed changes in the

opacity of the upstream and downstream sampling paper,

respectively.

Arrestance determinations were made at the beginning and at

the end of the test of each specimen and at several intermediate loading conditions. The arrestance determinations
3-

were made with Cottrell precipitate only, while cotton linters

were added during the loading process in a ratio of 4 parts to

every 96 parts of Cottrell precipitate, including that amount

of Cottrell precipitate used for arrestance 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 pressure drop across the media was recorded at the beginning of the test of each specimen, after each arrestance deter

mination, after introduction of each 20-gram increment of

Cottrell precipitate into the test duct, and at the beginning

and end of each advance cycle.

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 record the pressure drop across the medium at

the beginning and at the end of each advance cycle. The

pressure switch was adjusted to commence the advance cycle

when the pressure drop reached approximately 0.500 in. W. G.

4. Test Results

The pressure drop and arrestance values determined for the two

rolls of media tested are shown in table 1. The first roll

had an initial pressure drop of 0.160 in. W. G. and an initial

arrestance of 60 percent. Later arrestance determinations

made when the medium was being advanced periodically indicated

75 and 79 percent. The dust-holding capacity of this roll did

not meet the specified 200 g/sq ft, as will be referred to

later. Therefore, the test of this roll of media was discontinued and the manufacturer furnished another roll of media

with modified characteristics.

The pressure drop of this second roll, when clean, was 0.125

in. W. G. and its arrestance 67 percent. Eight arrestance

determinations, made at pressure drops between 0.460 in. W. G.

and 0.498 in. W. G. and averaging 0.483 in. W. G., showed

arrestance values from 73 to 75 percent, averaging 74 percent.
-4-

Tables 2 and 3 show the observed values of the mat travel,

the dust load, and the pressure drop across the media before and after the advances for the first and second rolls,

respectively.

Table 2 shows that the first roll received a dust load of

740 g per foot width, or 1480 g total for the 24-in. wide

filter area while advancing a total of 46 inches.

After an initial advance of 3 in. the mat advanced in 28

steps ranging from 1 in. to 2 in. The pressure drop across

the mat at the start of the advance cycle ranged from 0.48

in. W. G. to 0.505 in. W. G. The maximum specified pressure drop of 0.5 in. W. G. was exceeded five times toward

the end of the test even though no adjustment of the pressure switch was made.

Table 3 gives the corresponding values for the second roll.

A total of 1688 g of dust was used and the medium advanced

22 times for a total of 38 inches, the first time 4 in. and

then between 1 in. and 2 in. each time.

The pressure drop at the start of the advance cycle was adjusted to 0.500 in. W. G. during the earlier advance cycles

but came up to 0.502 in. W. G„ twice towards the end of the

test. The pressure drop at the end of the advances was between 0.44 in. W. G. and 0.46 in. W. G., after an initial

value of 0.49 in. W. G.

The dust-holding capacity of the specimens was determined

as the slope of the straight line that best fitted the

points of observation when plotting the mat travel against

the respective dust load, as shown in Fig. 1. This figure

shows the performance of the media after 1000 g of dust had

been introduced into the test apparatus, i.e., 500 g per

foot width, and a repetitive cyclic advance of the specimen

media had been established. According to this graph, the

first roll received 232 grams of dust/ft of width while

moving 16 in., from the 30-in. to the 46-in. position, corresponding to a dust-holding capacity of

232 x — = 174 g/sq ft.

16
5

The second roll received a dust load of 358 g per foot width

while advancing from 19 to 40 in., a distance of 21 in. The

dust-holding capacity of this roll was

358 x 11 = 205 g/sq ft

21

Table 4 presents a summary of the observed performance data

of the two specimens of media and the required values

according to applicable federal specifications.

The dust-holding capacity of media of this type Increases

when the average pressure drop increases and when the individual advance lengths are kept small. During this test the

pressure drop was adjusted so close to the maximum of 0.5 in.

W. G, initially that this value was exceeded a number of

times by a small amount and the advances during the steady

state operation averaged approximately 1,5 in. These favorable test conditions were undoubtedly a factor in causing

the performance of the test specimens to approach the specification requirements so closely.

USCOMM-NBS-DC

Table 1

PRESSURE DROP AND ARRESTANCE OP

PILTREX TYPE GPC-3 MEDIA

Pressure Drop,, In, W. G, Arrestance, %

RODL #1

0.160

0.162

0,-484

0.461

60

61

75

79

ROLL #2

0.125

0.127

0.485

0.460

0.464

0.492

0.495

0.498

0.482

0.485

67

67

75

74

74

74

73

74

74

74
Table 2

MAT TRAVEL, DUST LOAD, AND PRESSURE DROP OP

FILTREX GFC-3 FILTER MEDIUM, FIRST ROLL

Dust Load Travel of Mat, in. Pressure Drop

g/ft width Advance Total

Before

Advance

188 3 3 0.490

198 2 5 0.490

218 2 7 0.485

239 2 9 0.488

260 2 11 0.485

271 1 12 0.490

297 2 14 0.480

302 1 15 0.480

334 1 1/2 16 1/2 0.500

344 1 1/2 18 0.498

375 2 20 0.500

396 1 1/2 21 1/2 0.500

407 1 22 1/2 0.500

427 1 1/2 24 0.500

448 1 25 0.497

469 2 27 0.500

490 1 1/2 28 1/2 0.498

511 1 1/2 30 0.500

531 1 31 0.500

552 2 33 0.500

573 1 34 0.500

584 2 36 0.504

605 1 1/2 37 1/2 0.488

636 1 1/2 39 0.495

667 1 1/2 40 1/2 0.502

678 1 41 1/2 0.500

698 1 1/2 43 0.504

719 1 1/2 44 1/2 0.504

740 1 1/2 46 0.505

THE

in. W. G.

AlterAdvance

0.450

0.450

0.445

0 . 445

0.445

0.445

0.450

0.450

0.470

0.460

0.460

0.460

0.460

0.460

0.460

0.460

0.460

0.460

0.460

0.460

0.470

0.450

0.450

0.450

0.460

0.460

0.460

0.460

0.460
Table 3

MAT TRAVEL, DUST LOAD, AND PRESSURE DROP OP THE

FILTREX GFC-3 FILTER MEDIUM, SECOND ROLL

Dust Load Travel of Mat, in. Pressure Drop, in. W. G.

g/ft width Advance Total

Before

Advance

After

Advance

281 4 4 0.512 0.49

303 2 6 0.502 0.45

334 2 8 0.503 0.45

354 2 10 0.501 0.45

385 1 1/2 11 1/2 0.500 0.45

427 1 1/2 13 0.502 0.46

448 1 1/2 14 1/2 0.500 0.46

479 2 16 1/2 0.500 0.46

500 1 1/2 18 0.500 0.45

531 2 20 0.500 0.44

563 1 21 0.500 0.45

594 2 23 0.500 0.44

615 1 1/2 24 1/2 0.500 0.45

636 1 1/2 26 0.500 0.45

656 1 27 0.500 0.46

688 2 29 0.502 0.45

719 1 30 0.500 0.46

740 2 32 0.500 0.45

771 1 1/2 33 1/2 0.500 0.45

792 1 1/2 35 0.500 0.45

813 1 1/2 36 1/2 0.500 0.45

844 1 1/2 38 0.502 0.46

Table 4

SUMMARY OF TEST RESULTS AND

SPECIFICATION REQUIREMENTS

Arrestance Dust-Holding Capacity

g/sq 'ft

Roll #1

Roll #2

Specification

77 174

74 205

75 200

Requirement

Mat Travel vs. Dust Load

500 600 700 800 900

SDust Load, grams per foot width
-

- I•
U, S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL. BUREAU OF STANDARDS

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

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

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