NATIONAL BUREAU OF STANDARDS REPORT · NATIONALBUREAUOFSTANDARDSREPORT 6954 PERFORMANCETESTSOPAPRAMTHROW-AWAYTYPEAIRFILTER manufactured"by PramAireCorporation DivisionofPramCorporation

NATIONAL BUREAU OF STANDARDS REPORT

6954

PERFORMANCE TESTS OP A PRAM THROW-AWAY TYPE AIR FILTERmanufactured "by

Pram Aire CorporationDivision of Pram Corporation

Providence, Rhode Island

by

Carl W* Coblent z and Paul R« Achenbach

Report to

General Services AdministrationFederal Supply ServiceWashington 25

t

D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

FOR OFFICIAL OSE ONLY

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The I'unclions of the National Bureau of Standards are set forth in the Act of Congress, March3, 1901, as amended by Congress in Public Law 619, 1950. These include the development andmaintenance of the national standards of measurement and the provision of means ami methods for

making measurements consistent with these standards; the determination of physical constants and

properties of materials; the development of methods and instruments for testing materials, devices,

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agencies when the work relates to and supplements the basic program of the Bureau or when the

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Publications

The results of the Bureau’s work take the form of either actual equipment and devices or pub-

lished papers. These papers appear either in the Bureau’s own series of publications or in the journals

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National Bureau of Standards ($1.25) and its Supplement ($1.50), available from the Superintendent

of Documents, Government Printing Office, Washington 25, D.C.

NATIONAL BUREAU OF STANDARDS REPORTHBS IFROiCCT NB8 REPORT

1003-30-10630 September 8, i960 695^

PERFORMANCE TESTS OP A PRAM THROW-AWAY TYPE AIR FILTERmanufactured by

Pram Aire CorporationDivision of Fram^ Corporation

Providence, Rhode Island

by

C, W. Coblentz and P. R. AchenbachMechanical Systems SectionBuilding Research Division

toGeneral Services Administration

Federal Supply ServiceWashington 25> L. C.'

IMPORTANT NOTICE

NATIONAL BUREAU OF 8T/

IritenHedl For use yvlthin the (

to additional evaluation and nllsti(i^ cf this' Report, either ii

the Office of the Director, Nal

hov/ovor, by the Government 1

to reproduce additional copiei

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

ogress accounting documenUnally published it la subjected

eproductlon, or open-llteraturo

Ion Is obtained In writing front

Such permission Is not neededi

trepared if that agency wlahei

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

FOR OFFICIAL USE ONLY

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PERFORMANCE TESTS OF A FRAM THROW-AWAY TYPE AIR FILTER

manufactured by,

Fram Aire CorporationDivision of Fram Corporation

Providence,, Rhode Island

by

Carl W. Coblentz and Paul R» Achenbach

lo Introduction

At the request of the Federal Supply Service, GeneralServices Administration, the performance characteristics oftwo specimens of the Fram throw-away type air filter weredetermined. The scope of this examination Included the ar-restance of Cottrell precipitate in laboratory air, the pres-sure drop, and the dust-holding capacity of the specimens at370 ft/min face velocity.

2 . Description of Test Specimen

The filters were manufactured and supplied for testpurposes by the Fram Aire Corporation, Division of FramCorporation, of Providence, Rhode Island, and were intendedto be identical in construction. The test specimens werenominal 20 x 20 x 1 in. filters and measured I 9 3/^ in.square and 15/16 in. thick on the outside. The filter'medium was held in a cardboard fra?ne with channel-shapedcross section which left a net face area of I7 7/8 in.square, l.e., 2.22 sq ft.

The weights of the two specimeris were 240 and 235grams, respectively (approx, 8 1/2 oz). The filter mediawere of a light plastic felt about 1/2-in. thick. Themedium would not sustain combustion and according to themanufacturer’s claims was treated with a bactericidalsubstance. A perforated metal sheet was Installed in theframe to support the downstream face of the filter media.

3 . Test Method and Procedure

The filter was tested at a face velocity of 370 ft/mincorresponding to an air flow rate of 820 cfm. The arrest-ance determinations were made with the NBS ’’Dust SpotMethod” described in a paper by R. S, Dill entitled, ”A

- 2 -

Test Method for Air Filters/' (ASHVE Transactions j Vol. hk

,

p. 379, 1938). The filter under test was supported in a

frame which fitted the test apparatus and was carefullysealed to prevent any by-pass of air or inward leakageinto the test apparatus, except through the measuringorifice. The desired rate of air flow through the filterwas established, and samples of air were drawn from thecenter points of the test duct 2 feet upstream and 8 feetdownstream of the test specimen at equal rates, and passedthrough known areas of Whatman No. 4l filter paper. Thearrestance determinations were made with laboratory airinto which Cottrell precipitate was injected and diffusedat a ratio of 1 gram per 1,000 cu ft of air.

The two sampling papers used for each arrestance de-termination were selected to have the same light trans-mission when clean. The light transmission was measuredwith a sensitive photometer on the same portion of eachpaper before and after the test. In order to obtain simi-lar increases of opacity with both samplers, different sizeareas were used upstream and downstream of the filter. Thearrestance, A (in percent), was calculated by the followingformula

:

A = _ ^ X ^Su AU

X 100

where Sp and Sp are the downstream and upstream areas andad and AU the observed changes in the opacity of the down-stream and upstream sampling areas, respectively.

Whereas the arrestance determinations were made withCottrell precipitate only, cotton lint was added duringthe loading process in a ratio of 4 parts to every 96 partsby weight of Cottrell precipitate, including that amountused for arrestance measurements. The Cottrell precipi-tate had been previously sifted through a 100 mesh screenand the cotton lint was prepared by grinding No. 7 cottonllnters in a Wiley mill with a 4 millimeter screen.

Arrestance determinations were made at the beginningand at the end of the loading period of each test specimenand at several intermediate load conditions. The pressuredrop across the filter under test was recorded after eachincrement of 20 grams of dust had been introduced into thetest duct. The test was terminated when the pressure dropreached O.5 in. W.G.

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4. Test Results

A summary of the test results of the two specimens ispresented in Table 1 which shows the dust load, pressuredrop, and the arrestance values.

Table 1

Performance of a

Fram Throw-away Type Air Filter1 inch Nominal Thickness, 370 ft/min Face Velocity

Dust Loadg/sq ''ft

0

53972

126

Pressure Dropin. W.G.

FIRST SPECIMEN0.1200.1310.2200.3100.496

Arrestance

54*66*

6976*

SECOND0 0

5 0

47 0100 0

135 0

SPECIMEN110 —

116 50214 65353 73505 73

* Indicates average of two arrestance determinations.

The ’’Dust Load” shown in this table is the dust re-ceived by 1 sq ft net filter area. It is the weight of theCottrell precipitate and lint Introduced into the test ap-paratus divided by the net face area of the filter and di-minished by the percentage of dust fallout upstream of thefilter. This dust fallout was determined at the conclusionof the test by sweeping out the test duct and calculatingthe percentage of fallout to the total dust Introduced.

It will be noted that the pressure drop and the ar-restance of the first specimen was a little higher thanthat of the second one, associated with a slightly higherweight of the first specimen. The initial arrestances ofthe filters were 54^ and 30%, and the final arrestances,76^ and 73^^ respectively. The pressure drops of the

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clean filters were 0.120 and 0.110 in. W.G., respectively.The dust-holding capacity^ which is the dust load per unitarea at the final pressure drop of 0.5 in. W.G., averaged130 g/sq ft. The first specimen, presumably because of itshigher arrestance, had a dust load of 126 g/sq ft at 0.496in. W.G., whereas the second specimen showed 135 g/sq ftat 0.505 in. W.G.

Figure 1 presents a graph of the values shown in Table1 with smooth curves approximating the line of the leastmean square distances from the points of observation of bothspecimens. The average arrestance of approximately 67^ istaken as the imaginary horizontal line which would encloseequal areas above and below the arrestance curve.

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U.S. DEPARTMENT OF COMMERCEFrederick H. Mueller, Secretary

NATIONAL BUREAU OF STANDARDSA. 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., andBouldei;, Colo., is suggested in the following listing of the divisions and sections engaged in technical work. In

general, each section carries out specialized research, development, and engineering in the field indicated by its

title. A brief description of the activities, and of the resultant publications, appears on the inside of the front cover.

WASHINGTON, D.C.

ELECTRICITY, Resistance and Reactance. Electrochemistry. Electrical Instiniments. Magnetic Measurements.

Dielectrics.

METROLOGY. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering

Metrology. Mass and Scale. Volumetry and Densimetry.

HEAT. Temperature Physics. Heat Measurements. Cryogenic Physics. Rheology. Molecular Kinetics. Free

Radicals Reseav.ch. Equation of State. Statistical Physics. Molecular Spectroscopy.

RADIATION PHYSICS. X-Ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological

Equipment. Nucleonic Instrumentation. Neutron Physics.

CHEMISTRY. Surface Chemistry. Organic Chemistry. Analytical Chemistry. Inorganic Chemistry. Electro-

deposition. Molecular Structure and Properties of Gases. Physical Chemistry. Thermochemistry. Spectrochem-

istry. Puie Substances.

MECHANICS. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Combustion Controls.

ORGANIC AND FIBROUS MATERIALS. Rubber. Textiles. Paper. Leather. Testing and Specifications.,

Polymer Structure. Plastics. Dental Research.

METALLURGY. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion. Metal Physics.

MINERAL PRODUCTS. Engineering Ceramics. Glass. Refractories. Enameled Metals. Constitution and

Microstructure.

BUILDING RESEARCH. Structural Engineei'ing. Fire Research. Mechanical Systems. Organic Building Ma-terials. Codes and Safety Standards. Heat Transfer. Inorganic Building Materials.

APPLIED MATHEMATICS. Numerical Analysis. Computation. Statistical Engineering. Mathematical

Physics.

DATA PROCESSING SYSTEMS. Components and Techniques. Digital Circuitry, Digital Systems. Analog

Systems. Applications Engineering.

ATOMIC PHYSICS. Spectroscopy. Radiometry. Mass Spectrometry. Solid State Physics. Electron Physics.

Atomic Physics.

INSTRUMENTATION. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical

Instrumerrts. Basic Instrumentation.

Office of Weights and Measures.

BOULDER, COLO.

CRYOGENIC ENGINEERING. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. GasLiquefaction.

IONOSPHERE RESEARCH AND PROPAGATION. Low Frequency and Very Low Frequency Reseai’ch. Ion-

osphere Research. Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Seiwices.

RADIO PROPAGATION ENGINEERING. Data Reduction Instrumentation. Radio Noise. Tropospheric Meas-

urements. Tropospheric Analysis. Propagation -Terrain Effects. Radio-Meteorology. Lower Atmosphere Physics.

RADIO STANDARDS. High frequency Electrical Standards. Radio Broadcast Service. Radio and Microwave

Materials. Atomic Frequency and Time Standards. Electronic Calibration Center. Millimeter-Wave Research.

Microwave Circuit Standards.

RADIO SYSTEMS. High Frequency and Very High Frequency Research. Modulation Research. Antenna Re-

search. Navigation Systems. Space Telecommunications.

UPPER ATMOSPHERE AND SPACE PHYSICS. Upper Atmosphere and Plasma Physics. Ionosphere and

Exosphere Scatter. Airglow and Auiora. Ionospheric Radio Astronomy.