NATIONAL BUREAU OF STANDARDS REPORT

9404

PERFORMANCE TEST OF A

FOUR- PLEAT DYNEL FIBER FILTER

Manufactured by

Union Carbide Corporation

Linde Division

270 Park Avenue

New York, N. Y. 100X7

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

by

Charles M. Hunt
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assur- ing maximum application of the physical and engineering sciences to the advancement of technology

in industry and commerce. Its responsibilities include development and maintenance of the national

standards of measurement, and the provisions of means for making measurements consistent with

those standards; determination of physical constants and properties of materials; development of methods for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices

for incorporation in codes and specifications; advisory service to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Govern- ment; assistance to industry, business, and consumers in the development and acceptance of commercial standards and simplified trade practice recommendations; administration of programs in cooperation with United States business groups and standards organizations for the development

of international standards of practice; and maintenance of a clearinghouse for the collection and

dissemination of scientific, technical, and engineering information. The scope of the Bureau’s

activities is suggested in the following listing of its three Institutes and their organizational units. Institute for Basic Standards. Applied Mathematics. Electricity. Metrology. Mechanics. Heat. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radiation Physics. Radio Standards

Laboratory:* Radio Standards Physics; Radio Standards Engineering. Office of Standard Reference

Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.* Materials Evaluation Laboratory. Office of Standard Refer- ence Materials. Institute for Applied Technology. Building Research. Information Technology. Performance

Test Development. Electronic Instrumentation. Textile and Apparel Technology Center. Technical

Analysis. Office of Weights and Measures. Office of Engineering Standards. Office of Invention and

Innovation. Office of Technical Resources. Clearinghouse for Federal Scientific and Technical

Information.**

‘Located at Boulder, Colorado, 80301.

’ ‘Located at 5285 Port Royal Road, Springfield, Virginia, 22171.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

42103-40-4215630

NBS REPORT

9404

September 22, 1966

PERFORMANCE TEST OF A

FOUR- PLEAT DYNEL FIBER FILTER

Manufactured by

Union Carbide Corporation

Linde Division

270 Park Avenue

New York, N. Y. 10017

by

Charles M. Hunt

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 prt

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

iting of this Report, either in

Jffice of the Director, National

e Government agency for which

es for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Performance Test of a

Four-Pleat Dynel Fiber Filter

Manufactured by

Union Carbide Corporation

Linde Division

270 Park Avenue

New York, N. Y. 10017

by

Charles M. Hunt

Performance Test of a

Four-Pleat Dynel Fiber Filter

Manufactured byUnion Carbide Corporation

Linde Division

270 Park Avenue

New York, N. Y. 10017

by

Charles M. Hunt

1. Introduction

At the request of the Public Buildings Service of the General

Services Administration, performance characteristics of a four-pleat

Dynel fiber filter manufactured by the Linde Division of the Union

Carbide Corporation were determined. The scope of the investigation

included determination of the arrestance of the particulate matter

in laboratory air and of Cottrell precipitate by the filter. Pressure

drop across the filter at the rated flow of 1300 cfm was determined

as the dust load was increased from zero to a final pressure drop

in excess of 0.5 inches W. G., and the nominal dust holding capacity

of the filter was determined.

2. Description of the Test Specimen

The filter consisted of a replaceable filter media which was

formed into four vertical pleats, each about 11 inches deep. The

filter fit into a heavy wire rectangular frame having face dimensions

O ©f 20 inches x 20 inches, corresponding to a face area of 2.77 ft .
- 2 -

The pleats were self-supporting, and were not held in place

on the downstream side by the frame.

The filter media was white in color, and a scrim backing ©f

about 4 threads per inch was cemented to the downstream surface.

Under the microscope the fibers appeared somewhat flat with a typical

thickness of about 15 microns and width ©f about 30 microns. The

fibers would burn when held in a flame but extinquished immediately

upon withdrawal.

3. Test Method and Procedure

The filter was tested at the rated capacity of 1300 cfm. The

arrestance determination was 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 flow of air 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. Each sample of air was passed through Whatman

No. 41 filter paper. Arrestance determinations were made with the

particulate matter in laboratory air as the aerosol and also with

Cottrell precipitate injected into the air stream at an average concentration of about one gram per 1000 cu ft of air.
~3~

The relative amount of light passing through the sampling

papers was measured on the same area of each paper before and after

test, and the two sampling papers used for any one arrestance determination were selected to have the same light transmission when clean

One of the requirements of the dust spot method is that the

amount of light transmitted through the upstream and downstream dust

spots be approximately equal. Since the test filter removes some of

the dirt from the air, the downstream paper will nearly always be

lighter unless means are taken to equalize the optical density of the

two dust spots. This is accomplished by the unequal area method or

the timer method. In the unequal area method, the downstream sample

is drawn through a smaller area of paper than the upstream sample by

means of unequal sampling plates. In the timer method the sampling

areas are equal, but downstream sampling is continuous while upstream

sampling is intermittent, and controlled by a timer with a 5 minute

cycle. In most ef the arrestance determinations reported here unequal

sample areas were used to obtain dust spots of similar density. The

arrestance was then calculated by the equation:

( 1 )
-4-

where A represents the percent arrestance, AU and AD represent

the relative change in the amount of light passing through the

upstream and downstream papers due to the dust spots, and Sjj

and S D represent the areas of sampling paper upstream and downstream.

Two arrestances were made using the timer. In this case

arrestance was calculated by the equation:

where T is the fraction of the time sampled upstream, and the

other symbols have the same significance as before.

The filter was loaded with test dust consisting of 96 parts

by weight of Cottrell precipitate and 4 parts of No. 7 cotton linters.

The Cottrell precipitate was dispersed into the air stream at a rate

of approximately 1 gram per 1000 cu ft of air, and the cotton linters

were dispersed separately after each 20 gram increment of Cottrell

precipitate. Arrestance determinations were made initially and at

selected intervals in the dust loading process.

The total dust fed, the pressure drop across the filter, and

dust arrestance with atmospheric dust and Cottrell precipitate are

given in Table 1. Individual arrestance values rather than averages

are listed in this table because of the wide variation in individual

A ( 2 )

4. Results

values particularly with atmospheric dust. The data are also plotted
- 5 “

in Figure 1 where tipper curve represents arrestance of Cottrell

precipitate as a function of total dust fed, and the bottom curve

is similar plot of pressure drop across the filter. Points are shewn

for atmospheric arrestance, but no curve is drawn because of the wide

variations between replicate determinations, and no attempt was made

t© establish an average atmospheric arrestance. No entirely satisfactory explanation for the wide rang© of arr©stances with atmospheric

dust is offered, but th© filter was of the dry type, ©f moderate

efficiency, and may have released variable amounts ©f dust into the

downstream duct by "unloading" during the test. About 6.5 grams of

dust were collected from the first 5 feet ©f the floor of the duct

downstream from the filter after completion ©f the test.

The initial arrestance of Cottrell precipitate was 80.3 percent,

which is an average of the two determinations in Table 1. The average

arrestance, based on the area under th© upper curve in Figure 1, was

88.1 percent up to a pressure drop of 0.5 inches W. G. and 90.2

percent up to a pressure drop of 0.75 inches W. G.

The initial pressure drop across the filter was 0.245 inches.

A pressure drop of 0.013 inches was obtained with an empty frame in

the duct which had a 20 inch x 20 inch opening. This indicates that

a small part of the pressure drop across the filter arose from the

fact that it did not occupy the entire 2 ft x 2 ft duct area. The
6

filter reached a pressure drop of 0.5 inches W. G. after 860 grams

of dust had been £®d to the filter, and a final pressure drop of

0.754 inches W. G. was reached after 1362 grams of dust reached the

filter. At 1300 efra, 860 grams of dust corresponds to 660 grams

per 1000 cfm of rated capacity.

In table 2 some ©£ the important filter characteristics are

compared with requirements for a fype^C filter, according to General

Services Administration Air Conditioning Standard of December 1964.
-7-

Table 1

Performance of Union Carbide Four-Pleat,

Dynel Filament Filter at Rated Capacity of 1300 cfm

Total dust Pressure Percent Arrestance

feda drop Atmospheric Cottrell

(grams) (inches W.G.) dust precipitate —

0 0.245 22.9 79.9

40.3 80.7

--- 30.3 ----- --- 30.2

120 .282

203 .305 30.6 85.7 —

.304b 58.8 84.0 — 46.7

— - “ ~ 56.8

48.1 —

370 .364

453 .386 33.5 87.0

.386b — 35.5 89.2

28.

5

C 495 .403 --

— 598 .442 — . 436b ---- — 620 .468 ---- 810 .483 • — 870 .505 37.2 94.3 — .498b 35.8 92.3

--- 20.

4

C — 995 .545

1110 .597 97.0 —

—

— 92.1 —

— 92.0

1247 . 670 — 1362 .754 — 93.2 — —

93.2

a . 0.8g of dust was recovered upstream from the filter after the

conclusion of the test. From this it is assumed that practically

all dust fed reached the filter.

b. These pressure values were obtained after shutting down test duct

overnight or over weekend and restarting.

c. These arrestance values were obtained with the timer, while

all other values were obtained with plates of unequal area.
Table 2

Performance of Union Carbide Four^Pleat,

Dynel Filament Filter compared with

GSA Requirements for type-C filter

..

• * r Union Requirement

Carbide type“C

filter filter

Nominal dust holding capacity

when 0.5 inches W.G. is reached

(grams per 1000 cfm capacity)

660 357

Average arrestance of Cottrell

precipitate pH 00 00 80

USCOMM- NBS - DC
1