NATIONAL BUREAU OF STANDARDS REPORT

/o. oo

8337

RECOMMENDED SPECIFICATION FOR

TEST PROCEDURES TO DETERMINE SUITABILITY OF

DUCTS FOR USE IN RESIDENTIAL

WARM AIR HEATING AND AIR-CONDITIONING SYSTEMS

by

Selden D. Cole and Paul R. Achenbach

/

to

Federal Housing Administration

Washington, D„C.

<^Jbs>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-20-10437 April 14, 1964 8337

TEST

RECOMMENDED

PROCEDURES TO

SPECIFICATION FOR

DETERMINE SUITABILITY OF

DUCTS FOR USE IN RESIDENTIAL

WARM AIR HEATING AND AIR-CONDITIONING SYSTEMS

by

Selden D. Cole and Paul R, Achenbach

Mechanical Systems Section

Building Research Division

to

Federal Housing Administration

Washington, D„C.

IMPORTANT NOTICE NATIONAL BUREAU OF STA

for use within the Government, f and review. For this reason, the whole or in part, is not authorit Bureau of Standards, Washingtoi

the Report has been specifically [

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

s accounting documents intended objected to additional evaluation

listing of this Report, either in

Office of the Director, National

the Government agency for which

pies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

RECOMMENDED SPECIFICATION FOR

TEST PROCEDURES TO DETERMINE SUITABILITY OF

DUCTS FOR USE IN RESIDENTIAL WARM AIR HEATING

AND AIR-CONDITIONING SYSTEMS

Section I. Requirements

The following requirements apply to ducts used in residential

warm air heating and air-conditioning systems serving one or two

family residences not over three stories in height. Requirements A

through G apply to rigid, semi-rigid, and flexible ducts regardless

of where they are located in the structure. Requirement H applies

only to rigid or semi-rigid ducts installed in walls, attics, occu- pied spaces, or suspended from floor joists or beams. Requirement I applies only to ducts installed in or under concrete s labs-on-ground

.

Requirement J applies only to flexible ducts.

A. Odor Emission Test (Section V)

B. Micro-organism Resistance Test (Section VI)

C. Erosion Test (Section VII)

D. Impact Test (Section VIII)

E. Air Leakage Test (Section IX)

F. Deformation and Deterioration at High Temperature & Humidity

(Section X)

G. Collapse and Rupture Tests (Section XI)

H. Bending and Permanent Deformation Test (Section XII)

I. Bending and Crushing Test (Section XIII)

J. Crushing Test for Flexible Ducts (Section XIV)

Section II. Labeling and Identification

Any duct material manufactured by one company and submitted for

acceptance shall bear an identifying mark or symbol representing that

material. Ducts offered under a contract as having met the test re- quirements shall bear the same identifying mark as the test specimens

which met the requirements. If at any time a manufacturer changes a duct material or its fabrication procedures in a way that measurably

affects any of the performance characteristics described in this

specification, a different identification mark shall be assigned to

the product, and this new product shall be tested for compliance with

the performance requirements before acceptance.

-

1 -
Section III. Sampling and Rejection Procedures

for Test Specimens

Sampling: Test specimens shall be new material selected from

regular production stock and shall not be taken from the first

or last part of a production run.

Rejection: (1) Duct specimens shall not be accepted for test

unless each test specimen bears a clearly visible identification mark or symbol which has been assigned to all identical

duct material manufactured by that company. (2) If, during

the tests, one specimen fails to meet a specific test re- quirement, a second specimen shall be subjected to the same

test. If two specimens fail to meet any one test requirement, the duct material shall be rejected as not meeting the

acceptance requirements.

IV. Specimen Size and Specimen Conditioning

Each duct specimen shall be of nominal 8-inch diameter or of

equivalent cross section area, if rectangular, and shall be

at least six feet long.

A-l In case a given test requires only a portion of a specimen,

the portion shall be taken more than six inches from either

end of the specimen.

A-2 In case more than one specimen is required for a test, the

two or more specimens shall be joined by a method recommended

for installation by the manufacturer of the duct.

B. The duct specimens shall be conditioned to moisture equilibrium in room air at a relative humidity of 50 ± 5 percent and

a temperature of 80 ± 5°F before subjection to specific test

requirements

.

A.

B.

Section

A.

Section V. Odor Emission Test

A. Purpose : The purpose of this test is to determine whether or not a duct or duct material emits excessive objectionable or nonob jectionable odor.

B. Test Specimen : The test specimen shall consist of a 6-foot

length of duct complying with Section III and Section IV, Paragraphs A and B.

- 2

-
C. Apparatus and Materials : The following materials shall be

assembled to form an apparatus illustrated in Fig. 1:

1. Two centrifugal blowers and motors

2. Electric resistance heaters

3. New and clean sheet metal tubes with connecting elbows,

tees, plugs, and a shutoff damper

4. An observation chamber

5. Thermocouples or thermometers

6. A thermostat with an adjustable temperature range up

to 225°F and a differential of 5 degrees or less

7. Specimen supports

8. Pitot tube or orifice and pressure taps

9. Pipe or blanket type insulation

10.

A panel of not less than 15 observers

In addition, three familiar sources of odor such as coffee, am- monia, apple, orange, garlic, or perfume shall be available.

D. Qualifying the Odor Panel : Each proposed observer on the

odor panel shall be subjected to three familiar odors by drawing

the odor into the outside air inlet indicated in Fig. 1. After

the introduction of each odor, the system shall be purged for

several minutes with outdoor air before introduction of the next

odor. No observer shall be used on the 15-member panel who

fails to recognize the three familiar odors in the observation

chamber

.

E. Test Procedure:

1. The test specimen shall be supported in the specimenholding chamber. Heated air at a temperature of 200°F

shall be recirculated over the duct specimen and the electric resistance heater for a period of 4 hours with the

damper at the outlet side of the fresh-air blower closed.

2. After the four-hour preconditioning period at 200°F,

the test specimen shall be cooled to ambient temperature.

Outdoor air shall then be blown over the specimen for one hour to purge all parts of residual odors.

3. With the outdoor blower stopped and the damper closed,

the duct specimen should then be reheated by recirculating

air at a temperature of 200°F over the electric resistance

heater for at least 30 minutes.

4. Immediately following this heating period, the first

observer from a panel of 15 should be stationed in the observation chamber while outside air is passed over the

heated duct at a velocity of 500 fpm as determined by the

pitot tube or orifice and thence to the observation chamber

- 3-
for a period of 2 minutes. The observer shall record whether

or not an odor was detected, whether it was objectionable or not, and whether it was weak or strong. His observations

shall not be revealed to other panel members.

5. Steps 3 and 4 should then be promptly repeated with each

member on the odor panel except that the reheating period

for all observers after the first shall be only 5 minutes.

F . Basis of Acceptance :

1. The odor panel shall consist of 15 members qualified by

the procedures in Section V-B.

2. A specimen duct will not be considered acceptable if

more than 5 members of the odor panel report an objectionable odor or if more than 10 members report a perceptible

non-objectionable odor.

Section VI. Micro-Organism Resistance Test :

A. Purpose : The purpose of this test is to evaluate the resistance of samples of fabricated ducts to the growth of mold.

B. Test Specimens : Each unit of specimens shall consist of

twelve samples of material each 1 1/2" x 1 1/2" square, selected

as in Section III, Paragraph A, and Section IV, Paragraphs A & B

.

C. Apparatus, Medium and Test Fungi :

1. Apparatus shall consist of:

a. An autoclave , capable of maintaining an interior temperature of 122 ± 2°C. (251 ± 3.6°F.) at a pressure

of 15.5 ± 0.5 pounds per square inch gauge for the

purpose of sterilizing glassware and the medium.

b. Erhlenmeyer flask, 100 CC capacity

c. Glass beads , 1/4" in diameter, 5 pieces

d. Glass pipettes , two required

e. Wire loop , of nichrome wire

f. Petri dishes , 10 centimeters in diameter with covers capable of being sealed with cellophane tape. One

Petri dish is required for each of the twelve samples

comprising a test unit.

- 4-
g- Filter paper , cellulosic

h. An incubation chamber , capable of maintaining a temperature of 29 £ 1°C. (84.5 ± 1.8°F.) and a relative

humidity of at least 50 per cent.

i. A sterile room , dust free, using sterilamps, antiseptic spray, or air filtration under pressure to maintain sterile conditions.

2 . Test fungi :

a. Chaetomium globosum shall be Chaetomium globosum,

A.T.C.C. 6205.

b. Aspergillus niger shall be Aspergillus niger A.T.C.C.

6275.

3. Medium : A culture medium of the following composition:

NH3 N03 ..... 3.0 grams

KH

2 P04 ....... 2.5 t!

MgSO4 .7H2 0 . . . . . 2.0 II

k

2 hpo4 ....... 2.0 II

Agar .... 20.0 II

DISTILLED WATER to make 1000 milliliters

The pH shall be adjusted to a range of 6.4 to 6.8 with

HC1 or NaOH as required. This is the base medium for

both fungi cultures. However, the medium to be used

for the Aspergillus niger shall be specially enriched

by the addition of 30 grams of brown sugar per liter

of solution.

D. Test Procedure :

1. Medium as specified in Item 3 shall be prepared and

poured in the required number of Petri dishes to a depth of 3/8".

2. Sterilize in the autoclave all of the apparatus in

Paragraph C, Item l.b through g including the medium

contained in the Petri dishes by retention in the autoclave at the temperature and pressure prescribed in

- 5

-
Paragraph C, Item l.a for 60 minutes. After sterilization remove to sterile room of Paragraph C, Item l.i,

taking care not to contaminate the sterilized equipment

and medium. The sterile room shall be used for all

preparation procedures.

Cultures, stock and substocks, and inoculum :

a. Chaetomium globosum fungus stock cultures shall be

carefully maintained on strips or squares of sterile

porous filter paper, or blotting paper, on a sterilized culture medium as specified in Paragraph C,

Item 3, and Paragraph D, Item 2. If there is evidence of contamination, the culture shall be promptly

renewed. The culture may be kept for not more than

four months in a refrigerator at approximately 3° to

10°C.

(1) Subcultures shall be prepared from a stock culture by transferring spores from the stock culture to a sterilized covered Petri dish containing sterilized medium. The subculture shall then

be incubated for a period of 7 to 21 days at 29

± 1°C. (84.5 ± 1.8°F.) in the incubation chamber

until in a ripe fruiting condition.

(2) Inoculum shall be prepared by transferring the

spores with the sterilized wire loop to a sterilized Ehrlenmeyer flask containing 5 sterilized

glass beads and 10 ml. of distilled water. This

mixture shall be shaken sufficiently to break up

the spores after which the solution shall be

diluted to 200 ml.

b. Aspergillus niger fungus stock cultures shall be

carefully maintained as specified in Paragraph D,

Item 3. a on a medium as specified in Paragraph C,

Item 3 for this growth.

(1) Subcultures shall be prepared and incubated as in Paragraph D, Item 3.a(l) using a medium as specified in Paragraph C, Item 3.

(2) Inoculum shall be prepared as specified in Paragraph D, Item 3. a (2).

Six specimens of each test unit as defined in Section III,

Paragraph A, and Section IV, Paragraphs A.l & B, shall be

inoculated with each of the two varieties of fungi. Three

will be inoculated with the face side up; three, with the

back side up.
a

.

Preparation : Each specimen shall be handled under

aseptic conditions and shall be sterilized by dipping

in 70 per cent ethanol for a few seconds followed by

a thorough rinse in distilled water after which each

is put in place firmly in the center of the solidified agar medium in its respective Petri dish. Six

of the specimens shall be tested with one fungi and

six with the other. Also of each subunit of six,

three shall have one surface in contact with the

medium and three with the opposite surface as stated

under Paragraph D, Item 4.

b. Controls shall be placed in each Petri dish along

with the specimen. Each control shall be a strip of

sterile blotting paper or filter paper, Paragraph C,

Item l.g, placed on the agar separated from the specimen. The purpose of the control is to provide a medium for the fungi, thus proving that the fungi is

active

.

c. Inoculation with a particular fungus shall be made by

using a sterile pipette individual to the fungus.

With the pipette, approximately 1 . 5 ml . of inoculum

shall be distributed over the specimen, the control

and the surrounding medium.

5. Incubation of the inoculated specimens shall be continued

for a period of 28 days at a temperature of 29 ± 1°C.

(84.5 ± 1.8°F.) and a relative humidity of 90 percent.

An approximate incubation condition is obtained by placing the covered and sealed Petri dishes in a room or chambers maintained at 85°F and 50 percent relative humidity .

E. Basis of Acceptance : Test dishes with controls that do not

exhibit a substantial growth of fungi after 7 days of incubation

shall be rejected and shall be started anew. A unit test, the

controls of which indicate a substantial fungus growth, shall be

examined after the required period of 28 days incubation. If

after this period any one of the specimens shows evidence of

evenly distributed or intense localized fungus growth under 10 X

magnification on either side of the sample (excluding growth over- lapping the edges), the test sample shall be considered to have

failed under the test of Section VI. See Section III, Paragraph

B for details on rejection procedure in event of failure to meet

requirements

.

Photographs of the specimen taken at the end of the 28-day

incubation period are required as a part of the test on fugus

resistance. Each photograph shall be taken with a scale laid

- 7 -
beside the specimen to indicate its size, and the light conditions shall be such that the photographs reveal the nature and

height of the fungus growth on the surface of the material.

The photographs should be enlarged so the specimen will be a 6" x 6" size in the enlargement.

Section VII. Erosion Test

A. Purpose ; The purpose of this test is to evaluate the airerosion of a duct under accelerated conditions.

B. Test Specimens : Each test specimen shall be selected according to Section III, Paragraph A, and Section IV, Paragraphs A $ B.

C. Apparatus and Materials : The following apparatus and materials shall be assembled as indicated in Figure 2:

1. A blower with sufficient capacity to provide an average

air velocity of 4000 fpm through the duct specimens.

2. High efficiency panel filters for fan inlet.

3. Velocity measuring instruments.

4. A collection chamber with U.S. Standard 200-mesh sieve

screen.

5. Cellophane tape, 3/4 inches wide.

6. Microscope, Power 10X

D. Test Procedure ;

1. The apparatus shall be assembled as in Figure 2 without

cellophane tapes and screen in place. Air shall be passed

through the test unit at a velocity of 4000 fpm for a period of 10 minutes to purge the system.

2. After purging, cellophane tapes shall be installed at

the blower discharge and in the entrance to the collection chamber, the collection box shall be wiped clean,

and the 200-mesh screen installed on the collection box.

3. Air at a velocity of 4000 fpm shall be passed through

the test specimens for a period of 4 hours.

4. At the end of the four-hour period, the cellophane tapes

from both stations shall be removed from he system and

examined under the microscope, and ’ „ collection box

shall carefully be cleaned with a soft hair brush. The

200-mesh screen shall be examined for foreign particles.

-8
E. Basis of Acceptance : The erosion properties of a duct specimen

shall be unacceptable if:

1. The tapes removed from the collection box reveal more foreign particles adhering to the surfaces than on the tape

removed from the duct at the fan air outlet when examined

under the microscope

„

2. The collection box sweepings reveal macroscopic particles

that can be identified with the duct specimens.

3. The 200-mesh screen reveals visible particles adhering

to its surface that can be identified with the duct speci- mens .

Section VIII. Impact Test

A. Purpose : The purpose of this test is to determine the resist- ance of ducts to impact damage from falling objects.

B. Test Specimens shall be selected according to Section III,

Paragraph A, and Section IV, Paragraph A.

C. Apparatus : The apparatus shall consist of:

1. One steel ball 2 inches in diameter and weighing 1.18 pounds

2. Depth gage and steel rule

3. An iris diaphragm and adjustable support for holding the

steel ball at a predetermined height and releasing it

without initial momentum

D. Test Procedure :

1. The duct specimen shall be placed lengthwise on a flat

surface

.

2. The support holding the steel ball shall be placed and

adjusted so that the ball is exactly 30 inches above the

high point of the outside surface of the specimen.

3. Three drops of the steel ball should be made at the quarter points of the specimen with impact on the top surface

of the specimen.

4. The depth and size of the indentations shall be measured

and recorded.

5. If the test specimen is of rectangular cross section, the

impact shall be made on the longer side of the duct.

- 9

-
E. Basis of Acceptance ; The impact resistance of a duct specimen

shall be unacceptable if: 1.

Any one of the three indentations caused by the falling

ball is more than 3/4 inches deep measured to the nearest

1/16 inch.

2. The inside vertical diameter is reduced by more than 10%

of the initial diameter at the point of maximum indentation.

3. The specimen is cracked or ruptured or delaminated at one

of the three points of impact.

Section IX. Air Leakage Test

A. Purpose : The purpose of this test is to determine the air

leakage of duct specimens and the joints between specimens.

B. Test Specimens : Each test specimen shall be selected according to Section III, Paragraph A, and Section IV, Paragraph A.

2

and B, and shall be 6 feet long.

C. Apparatus : The apparatus shall consist of:

1. Duct hangers

2. A source of air pressure at about 1 inch W.G.

3. A pressure tap at center of each end cap.

4. A manometer with a range of 1 inch W.G.

5. An integrating air flow meter with a range of 5 to

100 f

t

3 /hr

.

D. Test Procedure:

1. Two test specimens, each six feet long, shall be connected

by a jointing method recommended by the duct manufacturer,

and shall be installed as shown in Figure 3.

2. Apply a continuous internal static pressure of 0.50 inches

water gage to the test specimens for a period of one hour.

3. Record the air flow meter reading at the beginning and at

the end of the one hour period to determine the total air

leakage.

E. Basis of Acceptance : The air leakage rate measured by the air

flow meter, expressed in cubic feet per hour, should not exceed

20 (twenty) multiplied by the internal volume of the two joined

specimens expressed in cubic feet.

“ 10-
Section X. Deformation and Deterioration

at High Temperature and Humidity

A. Purpose : The purpose of this test is to determine whether or not a duct will adequately retain its shape, rigidity, and physical integrity under exposure to high humidity and high temperature

in an accelerated test.

B. Test Specimen ; The test specimen shall be selected according

to Section III, Paragraph A, and Section IV, Paragraphs A and B,

and shall be 6 feet long.

C. Test Apparatus : The test apparatus shall consist of:

1. A fog room capable of maintaining 100 percent humidity at

constant temperature in the range of 70°F to 75°F.

2. A unit heater with air delivery temperature controllable

at 250°F and suitable for attaching a discharge duct.

3. A blower capable of delivering air at 1000 fpm through

the unit heater and duct specimen.

4. Velocity measuring instruments (Pitot tube)

5. Temperature measuring devices

6. Duct hangers

D. Test Procedure :

1. A 6-foot duct specimen shall be suspended in the fog room

by metal duct hangers from each end of the specimen. If

the test specimen is rectangular in cross section, the

longer dimension shall be placed horizontally. After

mounting the specimen and before starting the test, the

outside diameter in a vertical direction shall be mea- sured at midlength and at each end. The distance between the bottom surface of the duct at the midpoint

between hangers and a reference straight edge in contact

with the two hangers at the bottom of the duct shall also

be measured. A means shall be provided for identifying

the orientation of the duct in the hangers.

2. The duct specimen unit shall remain suspended in the fog

room for a period of 19 hours under saturation conditions at a controlled temperature between 70°F and 75°F.

3. After 19 hours in the fog room, the specimen shall be

removed and installed as a part of the discharge duct

system of the unit heater.

4. Air at a temperature of 250°F and a velocity of 1000 fpm

shall be circulated through the duct for a period of 4

hours

.

- 11 -
5. The specimen shall be supported in the fog room again

with the same orientation as before.

6. The 19-hour exposure in the fog room followed by 4 hours'

exposure to hot air in the unit heater system shall be

repeated seven times.

7. The outside diameter and the distance between the bottom

of the duct and the straight edge shall be measured at

the positions described in D-l above, after completion

of the 7 exposure periods in the fog room, and while the

specimen is still suspended in the fog room.

E . Basis of Acceptance :

1. The outside diameter at any of the three stations of

measurement shall not change more than 1/2 inch.

2. The sag at midlength of the specimen shall not increase

more than 1/2 inch as a result of the seven exposure

cycles to high temperature and humidity.

3. There shall be no visual evidence of cracks, fractures,

delamination, corrosion or deterioration inside or outside of the test specimen.

Section XI. Collapse and Rupture Tests

A. Purpose : The purpose of these tests is to determine whether

or not duct specimens connected by typical jointing methods possess the strength and other physical characteristics necessary

to prevent collapse, rupture, deterioration or excessive change

in cross-section area under selected levels of positive and negative internal pressures.

B. Test Specimens : Two duct specimens 6-feet long and complying

with Section III, Paragraph A, and Section IV, Paragraphs A- 2 and

B shall be used for the collapse and rupture tests. The same specimens may be used for the two tests if the first test produces no adverse effects, but separate specimens shall be used

for the two tests if the first test produces measurable deterioration or permanent deformation.

C. Test Apparatus : The materials and apparatus required for the

collapse and rupture tests are as follows:

- 12 -
1. Sources of air pressure and vacuum

2. A manometer with a range from 2 in. W.G. vacuum to 5 in.

W.G. positive pressure

3. A cap for each end of the test duct fitted with a pressure connection

4. Duct hangers

D. Test Procedure :

1. Two test specimens, each 6 feet long, shall be connected

by a jointing method recommended by the duct manufacturer

and shall be supported as indicated in Fig. 4.

2. The end caps shall be fitted and sealed against air

leakage

.

3. The manometer shall be connected to the pressure connection on one end cap and the sources of vacuum and pressure

shall be connected in separate tests to the pressure connection on the other end cap.

4. The cross-section area and length of the test unit should

be measured and recorded.

5. For the rupture test, a positive pressure of 5 in. W.G.

shall be maintained on the test unit for one hour, whereas

for the collapse test, a vacuum of 2 in. W.G. shall be maintained on the test unit for one hour.

6. At the end of the rupture and collapse tests and while

the test pressure is maintained on the interior of the test

unit, the amount of distortion and increase or decrease in

cross-section area of the duct shall be determined and re- corded. The test specimens shall also be examined on the

exterior for evidence of rupture, cracking, delamination, or other deterioration while they are still under the test pressure, and shall be similarly examined on the interior after

release of the test pressure. Any change in the physical

characteristics shall be described and recorded.

E . Basis for Acceptance :

1. The test specimens shall not collapse, rupture, crack,

delaminate, or otherwise visibly deteriorate as a result of

the application of the positive or negative test pressures.

2. The cross section area shall not decrease more than 15

percent of the initial cross section area in any plane at

right angles to the center line throughout the length of

- 13 -
the test unit during the test with a negative internal

pressure, nor shall the increase in cross-section area

at any plane exceed 15 percent during the test with

positive internal pressure.

Section XII. Bending and Permanent Deformation Test

A. Purpose : The purpose of this test is to determine the

deflection of a duct under externally-applied concentrated

load and the permanent deformation upon load removal.

B. Test Specimen : The test specimen shall be selected in

accordance with Section III, Paragraph A, and Section IV,

Paragraphs A and B.

C. Test Apparatus : The apparatus and materials required are

as follows:

1. Two duct hangers of a type recommended by the manufacturer; or alternately, two bearing blocks, 3/4 inch in

thickness, shall be used and shall provide a clearance between the bottom of the duct and a reference surface of at

least 2 inches. The bearing blocks for round ducts shall

have a curved upper surface of a radius equal to the external

radius of the duct, and shall contact a 120-degree arc on the

duct circumference. The bearing blocks for rectangular ducts

shall be flat and of a length at least equal to the width of

the duct.

2. A loading block four inches long with a curved lower sur- face of a radius equal to the external radius of the duct

shall be used for round ducts, and it shall contact an arc

of 30 degrees on the top of the duct. The loading block for

rectangular ducts shall extend across the face of the duct

at right angles to the center line, and shall have a dimension of 4 inches parallel to the center line of the duct.

3. Metal weights totalling 10 lb including the weight of the

loading block.

D. Test Procedure :

1. The test duct shall be supported six inches from each end

of the specimen using either the hangers or the bearing blocks.

If the duct specimen is rectangular in cross section, the

longer dimension shall be placed in a horizontal position.

2. The vertical distance from a horizontal reference surface

under the duct specimen to the bottom of the duct shall be

measured at midlength.

- 14 -
3. The loading block and weights, totalling 10 lb, shall be

placed on top of the duct at midlength and left there for

24 hours.

4. After 24 hours the distance between the horizontal ref- erence surface under the duct and the bottom of the duct at

midlength shall be measured again.

5. The 10-lb load shall, be removed and the distance to the

reference surface beneath the duct measured as before 5 minutes after load removal.

6. The horizontal and vertical outside diameters of the duct

at midlength shall be measured not more than 10 minutes after

load removal.

E . Basis of Acceptance :

1. The duct specimen shall withstand the load without damage.

2. The maximum change in deflection at the bottom of the

duct as a result of the load application shall not exceed

1/2 inch after the load has been in place 24 hours, nor more

than 3/8 inch five minutes after load removal.

3. After load removal, the vertical and horizontal outside

diameters of the duct at midlength shall not differ from the

original dimensions by more than 1/2 inch.

Section XIII. Bending and Crushing Tests

A. Purpose : The purpose of these tests is to determine the sus- ceptibility of a duct to damage by bending or crushing during

installation in concrete slabs.

B. Test Specimens : Test specimens shall be selected in accord- ance with Section III, Paragraph A, and Section IV, Paragraphs A

and B. Separate specimens shall be used for the bending and

crushing tests.

C. Test Apparatus : The apparatus and materials required are as follows

1. A loading block 3 5/8 x 3 5/8 x 12 inches having two adjacent longer edges rounded to 1/2-inch radius.

2. Two bearing blocks 1 5/8 x 1 5/8 x 8 inches.

- 15 -
3. A horizontal flat surface at least 6 feet long.

4. Weights totalling 160 lb in increments of about 10 lb, or other means such as a testing machine for gradually applying

load to the loading block.

D. Test Procedure :

1. For the bending test the duct specimen shall be supported

on the bearing blocks laid crosswise to the duct 6 inches from

either end, with the bearing blocks resting on the horizontal

flat surface.

2. The loading block shall be placed crosswise on top of the

duct at midlength.

3. Load shall be applied to the loading block in increments

of about 10 lb to a total of 160 lb.

4. The deflection of the top and bottom surfaces of the duct

shall be measured at midlength before loading started and

after each increment of 10 lb additional load up to a total

load of 160 lb.

5. After being loaded at 160 lb for one minute, the load

shall be removed and the deflection of the top and bottom of

the duct at midlength measured 5 minutes after load removal.

6. For the crushing test, a new duct specimen shall be supported directly on the horizontal flat surface and steps 2-5,

inclusive, repeated.

E . Basis of Acceptance :

1. In the bending test, the duct shall be able to withstand

a load of 160 lb without deflecting more than 1 inch at midlength on the bottom or deforming more than 3 inches at the

station of load application on the top. Permanent deformation after load removal shall not exceed 1/4 inch at the

bottom or 1/2 inch at the top.

2. In the crushing test, the duct shall be able to withstand

a load of 160 lb without deforming more than 3 inches at the

station of load application on the top. Permanent deformation

after load removal shall not exceed 1/4 inch at the top.

3. There shall be no cracks, fractures, delamination or other visual permanent damage as a result of the bending or crushing tests.

- 16 -
Section XIV. Crushing Test for Flexible Ducts

A. Purpose : The purpose of this test is to determine the temporary deflection and permanent deformation of flexible ducts under

specified loading conditions.

B. Test Specimen : The test specimen shall be selected in ac- cordance with Section III, Paragraph A, and Section IV, Paragraphs

A and B.

C. Test Apparatus : The test apparatus is the same as that re- quired for the crushing test in Section XIII.

D. Test Procedure : The test procedure is the same as that specified for the crushing test in Section XIII except that the load

shall be applied in increments of 5 lb instead of 10 lb.

E . Basis of Acceptance :

1. The duct specimen shall be able to withstand a load of

40 lb without deforming more than 3 inches at the station of

load application on the top. Permanent deformation after

load removal shall not exceed 1/2 inch at the top.

2. There shall be no cracks, fractures, delamination, or other visual permanent damage as a result of the crushing

test

.

- 17 -

Fresh

Air

Inlet I I—

buO •H

APPARATUS

FOR

ODOR

TEST
Fig. 2 - APPARATUS FOR EROSION TEST
Actual

or

Simulated

Hangars (1)

«H CO o co 0) 2 8 * & $ u

<D 4-> 0s§I—I

pzn

•H

Fig. 3-

APPARATUS

FOR

AIR

LEAKAGE

TEST
a

Ct5 0

COCO

CDU

OhU

s!

«h e ° §

CD

O

O CtJ O k

to

O

-3-

&J0 •H

[L

APPARATUS

FOR

RUPTURE

AND

COLLAPSE

TESTS

V