standard for leakage testing

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Heating and

Ventilating

Association



DW/143 Ductwork Leakage Testing \ p ra cti ca l g uid •A practical guide to

DuctworkLeakage

Testing

(HVCA)

HEATING AND VENTILATING

CONTRACTORS' ASSOCIATION

Esca House, 34 Palace Court, London W2 4JG

Telephone: (020) 7313 4900 Fax: (020) 7727 9268

e-mail: [email protected] web: www.hvca.org

COPYRIGHT © 2000

by the Heating and Venti lating Contractors ' Association All rights reserved

(Revised) 20()()

ISBN: 0-903783-30-4

1

mailto:[email protected]

http://www.hvca.org/

http://www.hvca.org/




CONTENTS Page................ ,1,. ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• , 1 • •• •• ,1 •••••••••••••••••••••••••••••••••

Acknowledgements 2

Cautions 2Preface 3

PART ONE

Practical guide to leakage testing 4-6

Example of complete test sheet 7Hints on leakage testing 8-9

PART TWO

Ductwork classification and air leakage 10

Appendix A: Air leakage from ductwork 11-13Appendix B: Air leakage testing procedure 13-16

ACKNOWLEDGEMENTS

The HVCA records its appreciation and thanks to the persons and organisations who have freely

contributed to this work, and in particular to the members of the Drafting Panel.

Original DW/143 Drafting Panel 1983

J. H. G. Gardner (Chairman)

K.Angood

H. Brierley

H. Brocklehurst

P. Doyle

K.Waldron

K.Wheatley

Ductwork Group Technical Sub-Committee 2000

E. Poppleton (Chairman)

C. Collins

S. V . Howard

B. James

J. E. Murray

C. Robertson

G. P. Keller (Secretary, Ductwork Group)

J. M. Paynton (Former Secretary, Ductwork Group)

R. J. Miller (Former Secretary, Ductwork Group)

Front cover photograph by kind permission of Commtech Limited

WHERE NOT MANDATORY, DUCT LEAKAGE TESTING IS GENERALLY AN

UNJUSTIFIED SUBSTANTIAL EXPENSE.

FINANCIAL CAUTION

It is essential to realise that except where it is mandatory in Class C ductwork in DW/144 this document

is not an endorsement of the routine testing of ducts but purely a guide to outline the procedures,

necessary for testing ducts for conformity with air leakage limits.

When proper methods of assembly and sealing of ducts are used a visual inspection will suffice for the

verification of a well engineered construction.

2



PREFACE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Edgar Poppleton Chairman, Technical Sub-Committee Ductwork Group, 2000

Dctwork Specification DW1142, published by the HVCA in 1982, provided

for the first time in a long series of such publications for leakage limits overthe whole range of air pressures covered by the specification and (where

required) a test procedure to establish conformity.

Although leakage testing of high-pressure ductwork is still mandatory in DWI144

(as was the case in previous ductwork specifications issued by HVCA) the leakage

testing of ductwork designed to operate at low and medium pressures is required only

where so specified in individual job specifications.

With the retention of three pressure classifications in DW/144it is hoped that

the designer, having control over performance standards, will find leakage

testing an unnecessary contract expense with regard to low and medium

pressure ductwork see note Financial Caution (page 2).

Ductwork contractors faced with a job calling for leakage testing should take this

requirement very seriously and satisfy themselves as the job progresses that the

required leakage rate or rates are within the limits set by the designer or the client.

The cost of making good an installation that has been found on completion to have

failed in this respect can be very expensive.

DWI144 specifies leakage limits for the ductwork alone, because the ductwork

contractor has no control over the leakage characteristics of the various components

which go to make up the whole of the air distribution system. Where a job

specification calls for a leakage limit for the whole system, it will be for the designer

or client to ensure that the leakage rates of the components are also within the

required limits.

Edgar Poppleton Chairman,

Technical Sub-Committee Ductwork Group, 2000

3



Part One

A practical guide to

ductwork leakagetesting

1 General

With regard to air leakage, the responsibili-

ties for ensuring the achievement of a satis-

factory job is divided between the drawing

office, the factory and the ductwork installers

on site. It is essential that there is full co-operation between them.

2 The drawing office

2.1 Establish with the client or his represent-

atives the class of ductwork called for in the

job specification, i.e.:

Class A: up to 500 Pa positive

Class B: up to 1000 Pa positive

Class C: up to 2000 Pa positive

2.2 Establish with the client or their represent-

ative that the required leakage rate or rates

are for the ductwork alone (eg excluding

dampers, fire dampers, air handling units,

fans, coils, attenuators, terminal boxes)

unless, by prior agreement, the casings

for any such items have been manufac-

tured/sealed, by the supplier, to the required

standard of DW/144.

Additionally, establish the type of gasket

material required in relation to the pressure

class/velocity of the system.

Note:- Specific gasket material may be

required in locations such as clean rooms,

hospitals etc.

If a leakage limit is laid down for the whole

system, it will be for the client or the design-

er to ensure that the leakage characteristics

of the components are acceptable.

2.3 Agree with the client or designer the test

pressure for each section of the installation.

(Note that whilst duct construction specifica-

tion is related to the highest test class of the

duct installation it is important that each duct

test zone should only be tested to a pressure

to cover the mean working pressure of that

particular section of ducting - see A.9(b).

2.4 Decide on the best way to isolate the

installation into test zones. When doing so,

the drawing office should bear in mind the

test pressures called for, the allowable air

losses, the work sequence on site and the

capacity of the test equipment.

2.5 Arrange for the supply of suitable blanking

medium, e.g. heavy-duty polythene sheet.

2.6 Make sure that all test points and blanking

devices can be reached with the minimum of

difficulty after the ductwork has been

installed.

2.7 Ensure that a reading can be obtained, by

planning test sections to have a permitted

leakage of approximately 25 per cent less

than the total volume generated by the test

rig at the pressure required for each section.

2.8 Provide the ductwork installers with details

of the test zones, duct operating pressures

and test pressures; and indicate the nature of

the blanking devices, gasket material and

sealant to be used.

2.9 Prepare test sheets grvmg the information

called for on the sample test sheet shown on

page 7.

This information should indicate the test

content, the surface area of the ductwork to

be tested, and the permitted leakage of each

section to be tested (this leakage is to be

expressed in litres per second per square

metre of the ductwork surface area).

3 The factory

3.1 Take care to make components with a good

fit to minimise the use of sealant. A poor fit

cannot be remedied by the use of more

sealant - it will not work.

4



3.2 Seal all longitudinal seams, laps, cross joints,

rivets and duct penetrations generally, in

accordance with the requirements of

DW/144.

3.3 Make sure that sealant is properly applied to

the ends of all lock forms and other types of

longitudinal seam, and to the corners and

junctions between those seams and the cross

joints.

3.4 Take special care to have as small a clearance

as possible where there are penetrations of

the duct, as for example, damper spindles.

3.5 Fit and seal branch connections carefully, asrequired by DW/144.

3.6 To be sure of minimum leakage, special care

must be taken in the fitting and sealing of

access doors and panels etc.

3.7 To avoid the danger of breaking the seals, the

ductwork when ready to despatch to site

must be handled and loaded carefully.

4 Site work

For full details of procedure see Fig. 1 on Pages

8 and 9 and Appendix B Pages 14 and 15 .

4.1 Understand the proper use of the test rig.

It is expensive precision equipment. The

instructions must be read carefully and the

equipment handled in a responsible manner.

4.2 Make sure that the right type of test rig is

available for the job. A rig suitable for high-

pressure leakage testing is seldom suitable or

economic for testing low- or medium- pres-

sure ductwork, and vice versa.

4.3 Note that leakage testing is always done

under positive pressure even when the duct-

work is to operate under negative pressure.

4.4 Before installation, inspect all duct sections

to make sure that factory applied sealantshave not been damaged in transit. Make

good where any damage is noticed.

4.5 Ensure the correct gasket material has

been supplied and the application is in accor-

dance with the manufacturer's instructions.

Check with the drawings and specifications

where sealants are to be used on the crossjoints, and apply the sealants as necessary.

(Use only as much sealant as will do the job

- too much sealant is as bad as too little.)

4.6 Pay special attention to the sealing of joints

that will be difficult to reach after installation

of the ductwork.

4.7 Fix the blanking plates or other types of tem-

porary seal in the positions shown by the draw-

ing office. (Ensure that the blanking material isaccessible for subsequent removal.)

4.8 At the earliest opportunity agree with the

client or their representative on a progressive

testing programme.

4.9 Before presentation to the client or their rep-

resentative, it is essential that a preliminary

test is carried out on each section of the work

at the earliest opportunity to ensure that the

ductwork has been correctly manufactured

and site sealant correctly applied.

4.10 If these preliminary tests show that the leak-

age is over the limit, then:

4.10.1 Look for any obvious places where

there may be leaks, for example, an

open access door or missing or

punctured polythene blanks.

Simple methods of locating any

leakage are:

a) by listening for them;

b) by feeling for them especially

with a wet hand;

c) by applying soapy water over

the seams or joints;

d) by (with the agreement of the

client) using a smoke pellet.

NOTE When smoke pellets are

used, the smoke should be intro-

duced downstream of the test rigand not on its intake side.

5



4.10.2 Reseal or correct where you have

found the leakage source(s).

Manufacturing faults should

be reported to the factory

immediately.

4.10.3 Repeat the test after allowing

enough time for the sealant to cure.

(Remember that sealants take

longer to cure in cold weather.

Read the sealant manufacturer's

instructions. )

4.11 When satisfied with the results of the

preliminary tests then:-

4.11.1 On successful completion of thetest, offer the section to the client or

their representative for formal

acceptance and signature on the test

sheet;

4.11.2 A permanent record of tests must

be retained.

4.12 As tests are satisfactorily completed, remove

all blanking-off devices.

6



5 Example of a completed test sheetBased on ductwork shown on pages 8 and 9

Test No ..

General

Name of job ( Y ~ t t . ~ ~ f . : ! : ! ! : . . ' P ! . ~ C ! . .Building Ref. .. ( ' ( f ! . ' ! t . ! ? ( q r : ! ; .!. .

Part 1 - Physical details

a Section of ductwork to be tested . ~ ( d . . 4 ? ' ! t . f . I ! t . . 4 ? ' # ! ! ! . ' ! 1 . . ~ ( d J J . q p . ( . .

b Drawing Number ..g 9 . 1 : ~ ~ ! ! . ! . . .c Pressure Classification C/t l88 'C I (PROVIDED BY DESIGNERS). . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .

d Test static pressure ! . ~ 9 . Q T . t 1 . ~ p . q ! . J ? ( l : { I f- ! ¥ . ! - ? f N r F ' ! , E ; l ! ~ . I J U . F ? : . T f - ! T . A J ! ! J . I , :/ . 7 . ~

e Leakage factor ... Q . . ~ - ? . / ! t . ' E ! ! # . ~ ~ ! 1 : J : . ( .~~?"! .~:: . : .~.~~~.~:.~: !f Surface area of duct under test 80 St tJ It lre met res (FROM CALCULATIONS BELOW). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

g Maximum permitted leakage . ! . { ? / ( t : ( e . ~ ! 2 ? ~ 0 ( : . : : ! ! .

Part 2 - Test particulars

a Duct static pressure reading ! . - ? .9 . 9 .J l . t ! . ? ! . q ( ~ ( l ! M P . Rff. Mf. l 'f9 .Af li ! flWt{ ! l i~ !J ! . !r ; ) .

b Manufacturer and type of flow measuring device ~·.e S.~~ ..!.qg.7!~ .'!!~ .A to 100

N..I. (FROM RIG MANUFACTURERS

C Range of measurement of flow measuring device ~<r: .~?1.~~0 !:~~1!l!f'!:1!.~~!.

d Reading of flow measuring device g q _ . .~.P'q~fq!2? ( l : ! 1 . C ! t ; t , . ~ ! r : ! .

18/ '-1- .1 . (DERIVED FROM CHART SUPPLIED WITH RIG USING "d")

e Interpreted air flow leakage rate / ! r?:~. '?/~~0. ~ ~ ? " ! .E _ . R _ ~ c : ~ . ~ .E _ ~ I ? ~ ~ R _ . ~ ~ ~ . K : :. G _ ~ . I ? , If ? ~ ~ r .~ : !

f Duration of test (normally 15 minutes) ..!.-? ..'!!/ l(fI.~~ ..

D~te of test ! . : ! . . : 9 . 9 . Carried out by(.s~'!. t(:.~g.t!!.~:. . . . . . . . .Witnessed by ..~.~~ ..ignature] (Signature)

Printed Name.:~.ij.9.!'~~&........... Printed Name . r . ! . .~ , : ? ~ p . ~ . < ? ~ . .

and Company . r . ! l ? f P I ( F ! . J ? . ~ t . d : . . . . . . and Company / ! ~ .f ~ '! . J ? I ( ! . ~ ~ t . ~ . .

Periphery Length Area

millimetres metres square metres

3100 17.55 54.40

2500 5.57 13.93

1200 1.20 1.44

958 7.00 6.70

785 4.50 3.53

TOTAL 80.00

7



Fig. 1 Hints on Ductwork Leakage Testing

Take special care

with inaccessible

joints

6OOx6S0

800 x 7S0

FLEX

Kee p le ng th to a m in imum

aD d make su re tha t both

e nd c on ne ctio ns a re co r r e c t l y

sealed aD d tha t th e flexible

duc t itselfhas no leaks.

47S

TES T R IG

To be connected and o pe ra te d in

accordance wi1h t he appara tus

instructions. In general , site on

f irm le ve l base and ensure gauges

a re topped up with correct fluid

an d ze roed prior to commeocingFi t correct flow test. Inc l ined manometa' to read

measu r i ng device. leakage rate or pressu re d r op

w hic h c an be converted to leakage

rate by re ference to graph.

Iaorder toavoid

iKornct .........ofdad preaue

8ae tube froIIl tile

vertlal ... ometer...... be COaaeaMdirectly to the

network aader test.

SEQUENCE OF TEST

1. Prepare test sheet

2. Connect a n d adjust test rigto c or re ct p re ss ure .

3 . Rea d o ff le ak ag e rate.

4. R ese al ifn ec essa ry (a llo w time to cure).

S.Maintain test for IS mins.

6. S w itch o ff aD d allow to zero.

7. Reapply test pressu re aud check reading.

8. Re c or d d e ta ils on test sheet and ob ta in s ig natu re .

WARNINGTake care not to over prwsurtsesystem under test

8



11Ie . . .. . .. . .. . .. . .. dKtwoItl ......... _ ...... 011 . .. . 7

2500

rr<8OOX750~ I1 0 0 0 1

~=", ' "

K3 5 0 0 /

700 " , ' " V"

" "-.I 550 I~ I 0 " " -

f v tv----JJ \ ~

~p-- . .

3 ( ]50 ~ ~ = = b:=!!! ~f - - : : : : : v

~

.r

.>1oIi~

~.> ~

/ r - - - - - - -

Blank off all op e n

ends. Remembe r tor--

blaDk instrument

1appiogs a o d test

boles.4175

I--

I---

~

BIaDt at conven ient ~ ~er t ica l lD lDOl l le ter

to read p resswe place with access

for ease of re mova l ~. . . . .

intest sect ion . : : - - .

800 X 750 -~~ - - ~ - - - ~__.."""

H OW TO FIN D LEA KS

1.Look - par t icu lar ly at blaub, access openings

aD d difficult joints .

2. Listen - with test rignaming, leaks

should be audible.

3 . Feel - runn ing your hand (particularly ifwet)ove r joints ca n beJp to locate leab.

4. Soap a o d Water - paiDt ove r joints a o d look for bubbles •

5. Smoke Pellet - p la ced ins id e duc twork (obtain permission for use)

ORO No. 20433/12

9



Part Two

6 This section, apart from Appendix 'B', is

extracted from DW/144 - Specification for

Sheet Metal Ductwork, and for ease of refer-

ence the numbering as in DW /144 has been

retained. The leakage limits for EUROVENT

classifications A, Band C, as set out in their

document 2/2 (Air Leakage in Ductwork) have

been adopted for the low pressure, medium

pressure and high pressure Class C classifica-

tions.

Ductwork classification and

air leakage

6.1 Classification and air leakage limits

Ductwork classification and air leakage

limits are set out in Table l.

6.2 Compatibility with CEN

The leakage factors used in Table Ifor

Classes A, Band C are the same as those for

the classes similarly designated in the CEN

Document Pr EN 12237IPr EN1507.

6.3 Leakage at various pressures; and other

relationships

Applying the limits specified in Table 1,

Appendix A (Table 17) sets out the permitted

leakage at each of a series of pressures up to

a maximum for each class. Included in that

appendix is a graphical presentation of the

pressure/leakage relationship (see fig 178).

Appendix A, also gives details of the basis

for the leakage limits specified III

Table 1.

Table 1 Ductwork Classification and Air Leakage Limits

Staticressure limit

6.4 Air leakage testing

Air leakage testing of low and medium pres-

sure ductwork is not mandatory under the

specification DW/144.

Air leakage testing of high pressure ductwork

is mandatory under the specification DWIl44

and for details of testing procedure refer to

Part 1 of this guide.

Pa500

0.003 X pO.65

Air leakage limitslitres per second per squaremetre of duct surface area

Maximum air

t---P-OS-)'t-)'v-er-N--ti----I velocityega ve

PaS O O

mls10 0.027 X pO.65

1000

2000

Where p is the differential, pressure in pascals.

20 0.009 X pO.6550

750 40

10



APPENDIX A

Air leakage from

ductworkA.1 Introduction

Leakage from ducted air distribution systems

is an important consideration in the design

and operation of ventilation and air condi-

tioning systems. A ductwork system that has

limited air leakage, within defined limits, will

ensure that the design characteristics of the

system can be maintained. Itwill also ensure

that energy and operational costs are main-tained at optimum levels.

Ductwork constructed and installed in accor-

dance with DWI144 should minimise a level

of air leakage that is appropriate to the oper-

ating static air pressure in the system.

However, it is recognised that the environ-

ment in which systems are installed is not

always conducive to achieving a predictable

level of quality in terms of system air leakage

and it is therefore accepted that designers

may sometimes require the systems to be test-

ed in part or in total. It should be recognised

that the testing of duct systems adds a signif-

icant cost to the installation and incurs some

extra time within the programme (See 4.1 and

6.4 of DW/144 re mandatory testing).

A.2 Duct pressure

Ductwork constructed to DW1144 will be

manufactured to a structural standard that is

compatible with the system operating pressure.

There are three classes of duct construction to

correspondwith the threepressureclassifications:

Class A

Low pressure ducts suitable for a maximum

positive operating pressure of 500 Pascals

and a maximum negative pressure of -500

Pascals.

Class B

Medium pressure ducts suitable for a maxi-

mum positive operating pressure of 1000Pascals and a maximum negative pressure of

-750 Pascals.

Class C

High pressure ducts suitable for a maximum

positive operating pressure of 2000 Pascals

and a maximum negative pressure of -750

Pascals.

A.3 Leakage fromductwork

Leakage from sheet metal air ducts occurs at

the seams and joints and is therefore propor-

tional to the total surface area of the ductwork

in the system. The level of leakage is similar-

ly related to the air pressure in the duct sys-

tem and whilst there is no precise formula for

calculating the level of air loss it is generallyaccepted that leakage will increase in propor-

tion to pressure to the power of 0.65.

The effect of air leakage from high pres-

sure/velocity ductwork is critical in terms of

system performance, energy consumption

and the risk of high frequency noise associat-

ed with leakage.

These problems are less critical with medium

pressure/velocity systems, but should be

considered.

Low pressure/velocity ducts present thelowest risk in terms of the effect of leakage on

the effective operation of the system.

A.4 System leakage loss

As there is no direct relationship between the

volume of air conveyed and the surface area

of the ductwork system required to match the

building configuration it is difficult to express

air leakage as a percentage of total air vol-

ume.

Similarly, the operating pressure will vary

throughout the system and as leakage is relat-

ed to pressure the calculations are complex.

However, it is generally accepted that in typ-

ical good quality systems the leakage from

each class of duct under operating conditions

will be in the region of:

Class A low pressure 6%

Class B medium pressure 3%

Class C high pressure 2%

11



A.S Specifying air leakage testing

Respecting both the cost and programme

implications associated with testing ducts for

leakage, the designer may, for example indi-

cate that a particular system is tested as

follows:

a) High pressure ducts - all tested.

b) Medium pressure ducts - 10% of the

ductwork shall be selected at random and

tested.

c) Low pressure - untested.

Table 17 Air leakage rates

Maximum leakage of ductwork

Sta t ic Low-pressure Medium-pressure High-pressure

pressure Class A Class B Class C

differential

1 2 3 4

Pa Litres per second per square metre of surface area

100 0.54 0.18

200 0.84 0.28

300 1.10 0.37

400 1.32 0.44

500 1.53 0.51

600 0.58 0.19

700 0.64 0.21

800 0.69 0.23

900 0.75 0.25

1000 0.80 0.27

1100 0.29

1200 0.30

1300 0.32

1400 0.33

lSOO 0.35

1600 0.36

1700 0.38

1800 0.39

1900 0.40

2000 0.42

Note: Recommended 'mean' test pressures are highlighted in

bold type with the actual selection being left to the test

operator.

In the case where a random test is selected for

medium pressure ducts the following clause is

suggested for inclusion by the designer.

The designer shall select at random a maxi-

mum of 10% of the duct system to be testedfor

air leakage. The duct shall be tested at the

pressure recommended in Table 17of DWI144

for the classification for the section of the

ductwork that is to be tested.

The tests shall be carried out as the work pro-

ceeds and prior to the application of thermal

insulation.

In the event of test failure of the randomly

selected section, the designer shall have the

right to select twofurther sections at random

for testing. Where successive failures are

identified there shall be a right to require thecontractor to apply remedial attention to the

complete ductwork system.

The contractor shall provide documented

evidence of the calculations used to arrive at

the allowable lossfor the section to be tested

and the client, or his agent, shall witness and

sign the results of the test.

A.6 Special cases

There may be situations on a project wherecircumstances dictate that special considera-

tion be given to containing air losses, e.g. a

long run of ductwork may incur a dispropor-

tionate level of air loss.

In cases such as this example the designer can

specify an improved standard of airtightness,

i.e. 80% of allowable loss for Class 'B' ducts.

The designer should not specify a Class 'C'

test at Class 'C' pressure for a Class 'B' duct.

A.7 Suggested range of testing

(see cautionary note on page 2 of this guide)

• High pressure ducts 100% test

• Medium pressure ducts see A5

• Low pressure ducts Untested

• Exposed extract systems Untested

• Ceiling void extract

systems

• Secondary ducts from

VAV or fan coil units

• Flexible ducts

Untested

Untested

Untested

12



• Final connections and

branches to grilles and

diffusers Untested

A.S Testing of plant items

Items of inline plant (eg. Figs. 168 to 175) will

not normally be included in the air leakage

test. The ductwork contractor may include

such items in the test if the equipment has a

certificate of conformity for the pressure class

and air leakage classification for the system

under test.

A.9 Designer'scalculations

The designer can calculate with reasonableaccuracy the predicted total loss from a sys-

tem by:

a) Calculating the operating pressure in

each section of the system.

b) Calculating the surface area of the

ductwork in each corresponding pressure

section.

c) Calculating the allowable loss at the

operating pressure for each section of the

system (see Table 17 for allowable leak-

age figures).

A.10 Variable pressures in systems

Designers can achieve significant cost savings

by matching operating pressures throughout

the system to constructional standards and

appropriate air leakage testing, e.g. the prac-

tice of specifying construction standards for

whole duct systems based on fan discharge

pressures may incur unnecessary costs on a

project.

For example, some large systems could well

be classified for leakage limits as follows:

Plant room risers Class C

Main floor distribution Class B

Low pressure outlets Class A

~p.p.~~~~~~ .

Air leakage testing

Procedure

B.1 General

Section 6 (page 10)of this specification deals

with the performance requirements of duct-

work in respect of air leakage, and Table 17

(Appendix A) tabulates the limits of leakage

applicable to each class of ductwork.

Appendix B is solely concerned with recom-

mendations for the testing procedure.

B.2 Extent of ductwork to be

tested

B.2.1 The procedure set out in this section

is limited to the ductwork and those

items of in-line plant equipment that

are manufactured/sealed to the crite-

ria set out in Table 1 (also see

Appendix A.8).

B.2.2 The extent of the ductwork to betested and the method of selection

(where not included in the job spec-

ification) should be determined in

collaboration between the designer

and the ductwork contractor with

consideration having been given to

the recommendations outlined in

Appendix A.

B.2.3 Fit blanking devices in accordance

with the drawing office guidance

notes (Part 1, Section 2). To enable a

blank to be cut out after the testing is

completed, access may be required

adjacent to each blank.

B.2.4 Alternatively, rigid removable

blanking plates can be used,

although this involves remaking

joints.

13



DW/143 Ductwork Leakage Testing \ practic t!

Fig. 178 Permitted leakage at various pressures

Leakage in litres per second per square metre duct surface area

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14



B.3 Testing to be completed

before insulation, etc.

Testing shall be satisfactorily completed

before insulation or enclosure of the duct-work and before terminal units (if any) are

fitted.

B.4 Re·testing procedure where

necessary

B.4.1 The air leakage rate for any section

shall not be in excess of the permit-

ted rate for that section. Ifa first test

produces leakage in excess of the

permitted maximum, the sectionshall be resealed and retested until a

leakage not greater than the permit-

ted maximum for that section is

achieved.

B.4.2 If at the time of witnessing the test it

is apparent that excessive additional

sealing of seams or joints has been

done in order to meet the required

leakage level, the section of duct-

work under test shall not be countedas part of the tested ductwork,

except where the whole of the duct-

work is required to be tested.

B.S Minimum area to be tested

The section of ductwork to be tested shall

have an area large enough to enable the test

rig to register a measurable leakage.

B.6 Test pressures and leakage

rates

The maximum permissible leakage rates for

the full range of pressures are given in Table17. The recommended test pressures for the

various classes of ductwork are set out in

Table 2, and unless otherwise specified, the

choice of test pressure shall be at the discre-

tion of the test operator.

B.7 Test rig

B. 7.1 The accuracy of the test rig shall be

within:

± 10 per cent of the indicated flowrate, or 0.4 litres per second,

whichever is the greater; and

± 5 per cent at the indicated static

pressure in the duct under test.

B.7.2 The test rig shall be inspected by

the user before use on site, and

shall have a calibration certificate,

chart or graph dated not earlier than

one year before the test for which it

is used.

B.7.3 A schematic arrangement of an air

leakage test is given in Fig. 2.

B.8 Procedure

B.8.1 The section of ductwork to be test-

ed for air leakage shall be sealed.

Main ducts should be provided

Staticpressuredifferential

Low-pressureClass A

Pa

200

400

800

1200

1500

15



with flanged joints to enable

blanking plates to be fitted, while

small open ends may be sealed with

polythene or inflatable bags, which

should be left in position until final

connections are made.

B.9.1 Complete Part 1 of the Test Sheet.

B.9.2 Connect test rig to section of duct-

work to be tested.

B.9.3 Adjust test rig until the static pres-sure differential is obtained.

B.8.2 On low-pressure systems, final

grille spigots made as a second fix

operation shall be excluded from the

test. The joint shall, where practica-

ble, be checked by external visual

examination.

B.9.4 Check that the measured leakage is

within the permitted rate. (No addi-

tion shall be made to the permissible

leakage rate for access doors, access

panels or dampers where these are

included in the ductwork.)

B.8.3 Sufficient time shall be allowed

between installation and leakage

testing for sealants to cure.

B.9.5 Maintain the test for fifteen minutes

and check that the leakage rate hasnot increased.

B.8.4 Special care must be exercised in

making all joints which fall outside

the scope of the testing procedure,

i.e., joints between tested sections

of ductwork and between ductwork

and items of in-line equipment not

included in the test.

B.9.6 Reduce pressure in section to zero

by switching off the fan; then imme-

diately re-apply test pressure to

establish that the air leakage rate is

not greater than the previous read-

ing.

B.8.5 Due notice of tests shall be given, so

that arrangements for witnessing thetests can be made.

B.9.7 Record details on Part 2 of the Test

Sheet and complete, including wit-nessing.

B.9 Testing sequence 8.10Air leakage test sheet

The recommended sequence of testing is as

follows.

A example of a suitable Test Sheet is given

on page 7.

fan

Fig. 2 Schematic arrangement of an air leakage test

Blanking

plate

/'

Flow measuring device

(may be located onthe suction side ofthe fan)

Duct under test

Bleed valve (not necessary

/ if variable speedfan used)

Inclined gauge

16



(HVCA)

Heating and Ventilating Contractors' Association

Esca House 34 Palace Court London W2 4JG

Tel: 020 7313 4900

Fax: 020 7727 9268

e-mail [email protected]

web site www.hvca.org.uk


http://www.hvca.org.uk/

http://www.hvca.org.uk/


standard for leakage testing

Documents