CVSfB
I
143
A practical guide to
DUCTWORK LEAKAGE TESTING
Based on the requirements of DW/142 specification for sheet metal ductwork
(57.91
I
Ih
I
(A3ul
COPYRIGHT © 1983 by the
Heating and Ventilating
Contractors' Association
All rights reserved
HEATING AND VENTILATING
CONTRACTORS' ASSOCIATION
Esca House, 34 Palace Court,
London W2 4JG
Telephone: 071 229 2488
Fax: 071 727 9268
Obtainable from: HVCA Publications,
Old Mansion House, Eamont Bridge, Penrith,
Cumbria, CAIO 2BX
Telephone: (0768) 64771 Fax: (0768) 67138
Price: £9 (including inland postage)
Overseas: Surface mail £10.50 Air mail £11.00
3
Contents
Part One
Page
Acknowledgements
.
4
Preface
.
5
Financial Caution
.
6
Practical Guide to leakage testing
.
7-8
Example of complete test sheet
.
9
Hints on leakage testing
.
10-11
Part Two
Page
13-15
Air leakage from ductwork
Nomogram converting area basis to percentage of airflow
.
16
Air leakage testing procedure
.
17-18
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.
DW/143 Drafting Panel
J. H. G. Gardner (Chairman)
K. Angood
P. Doyle
K. Wheatley
K. Waldron
H. Brocklehurst
H. Brierley
J. M. Paynton (Former Secretary, Duct Work Group)
R. J. Miller (Secretary, Duct Work Group)
4
PREFACE
Ductwork Specification DW/142, published by the HVCA in 1982, provides
for the first time in a long series of such publications for leakage limits over the
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 mandatory in
DW/142 (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 introduction offour pressure classifications in DWI142 it is hoped
that the designer, having selectional control of constructional standards, will
find leakage testing an unnecessary contract expense with regard to low and
medium pressure ductwork. However, it is possible that initially the advent of
more stringent constructional requirements may be followed by an increased
demand by clients and specifiers for the testing oflow-and medium- pressure
ductwork and this booklet has been prepared in order to assist ductwork
contractors to minimise the cost of this unfamiliar operation.
It will be noted that the leakage limits specified in Appendix A of DW/142
are expressed in litres per second per square metre of duct area. It is however
possible that some ductwork specifications will still quote leakage limits as a
percentage of air flow. In order that the area basis can be converted to a
percentage equivalent a nomogram from DW/142 has been reproduced in
this booklet on Page 16.
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
indeed.
DW/142 specifies leakage limits for the ductwork alone, not for the
complete air distribution system. This is 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.
J. H. G. Gardner,
Chairman, Executive Committee,
Duct Work Group, 1982/83.
5
FINANCIAL CAUTION
As highlighted in the Prefaces ofboth this document and DWI142 not
enough emphasis can be placed on the fact that the much tighter ductwork
constructional standards brought about by the general acceptance of
DW/142, virtually negates the requirement for leakage testing, except for the
high pressure classes C & D.
It is essential to realise that except where it is mandatory this document is
not an endorsement of the routine testing ofducts but purely a guide to
outline the procedures, necessary for testing ducts for conformity with air
leakage limits set forth in a designer's specification.
When proper methods of assembly and sealing of ducts are used a visual
inspection will ordinarily suffice for verification of well engineered
reasonably air right construction.
WHERE NOT MANDATORY, DUCT LEAKAGE TESTING IS
GENERALLY AN UNJUSTIFIED SUBSTANTIAL EXPENSE.
6
Part One - A practical guide tel ductwork
leakage testing
I GENERAL
With regard to air leakage, the responsibility for
ensuring the achievement of a satisfactory job is
divided between the Drawing Office, the Factory
and the Site Erection Operatives. It is essential
that there is full co-operation between them.
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 THE DRAWING OFFICE
2.7 To ensure that a reading can be obtained,
plan test sections to have a permitted loss of
approximately 25 per cent less than the total
volume generated by the test rig at the pres-
The drawing office must:
2.1 Establish with the client or his representatives 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
Class D: up to 2500 Pa positive
sure required for each section.
2.8 Provide the erectors 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 giving the information
called for on the sample test sheet shown on
page 9.
This information should indicate the test
content, the surface area of the ductwork to be
tested, and the permitted loss for each section
to be tested (this loss is to be expressed in litres
per second per square metre of the ductwork).
2.2 Establish with the client or his representative that the required leakage rate or rates are
for the ductwork alone i.e. excluding dampers,
fire dampers, air handling units, fans, heater
batteries, silencers, terminal boxes, etc.
Additionally, establish the type of gasket
material required in relation to the pressure
class/velocity of the system.
3 THE FACTORY
Note:- Specific gasket material may be required in locations such as clean rooms,
hospitals etc.
3.1 Ductwork specification DW/142 requires
the sealing of more joints than was the case in
previous specifications. Care must therefore
be taken to make components with a good fit,
and to use only enough sealant to make a
satisfactory joint. A poor fit cannot be
remedied by the use of more sealant - it will
not work.
H a leakage limit is laid down for the whole
system, it will be for the client or the designer
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
specification 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 ofducting - see A.2.5(b).
3.2 Seal all longitudinal seams, laps, cross
joints, rivets and duct penetrations generally,
in accordance with the requirements of
DW/142.
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
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.
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.
7
3.5 Fit and seal branch connections carefully,
as required by DW/142.
carried out on each section of the work at the
earliest opportunity - before presentation to
the client.
3.6 To be sure of minimum leakage, special
4.10 If these preliminary tests show that the
leakage 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 introduced downstream of
the test rig and not on its intake side.
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 set.
(Remember that sealants take longer to do
this in cold weather. Read the sealant
manufacturer's instructions.)
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 for despatch to site
must be handled and loaded carefully.
4 SITE WORK
For full details of procedure see Appendix B
Pages 17 and 18 and the diagram on Pages 10
and II.
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 highpressure leakage testing is seldom suitable or
economic for testing low- or medium- pressure
ductwork, and vice versa.
4.3 Note that leakage testing is always done
under positive pressure even when the ductwork is to operate under negative pressure.
4.4 Before erection
Inspect all duct sections to make sure that
factory applied sealants have not been damaged in transit. Make good where any damage
is noticed.
4.11 When satisfied with the results of the
preliminary tests then:4.11.1 Offer the section to the client's
representative for formal acceptance;
4.11.2 On successful completion ofthe test
obtain a signature - on the test sheet;
4.11.3 A permanent record of tests must be
retained.
4.5 Ensure the correct gasket material has
been supplied for your situation and the application is in accordance with the manufacturer's instructions. Check with the drawings
and specifications as to where sealants are to
be used on the cross joints, and then apply the
sealants as necessary. (Use only as much sealant as will do the job - too much sealant is as
bad as too little.)
4.12 As tests are satisfactorily completed,
remove all blanking olT devices.
4.6 Pay special attention to the sealing of
joints that will be difficult to reach after erection of the ductwork.
Relevant Conversion Factors
Pressure
4.7 Fix the blanking plates or other types of
temporary seal in the positions shown by the
Drawing Office. (Again, make sure that the
blanking material can be reached when it has
to be removed.)
To convert
Multiply by
Inches water gauge to millibars
2.491
Inches water gauge to pascals (Pa)
249.1
I Pa = 1 Newton per square metre = 10,2 millibars
4.8 At the earliest opportunity agree with the
client or his clerk of works on a progressive
testing programme.
Volume Flow
To convert
4.9 To ensure that the ductwork has been correctly manufactured and site sealant correctly
applied it is essential that a preliminary test is
Multiply by
Litres per second to cubic metres
per hour
8
3.60
a con1pleted test sheet
Based on dllldwod{ shownn oun page 10 and 11
Test No
.
N.ew +It>~ Pt'Ciecl
General
Name of job
Building
Ref.
.
·wiM~···%iit··i~'
.....................................................................................................................
Part 1 - Physical details
a
Section of ductwork to be tested ..~ .. ~~.. ~
b
Drawing Number
c
Pressure Classification
d
Test static pressure
e
Leakage factor
f
Surface area of duct under test
g
Maximum permitted leakage
.:?:c:>i~~.1. ~~
O\ass B.
,
.
(PROVIDED BY DESIGNERS)
S?:#.J!~/~I.~f
(I'R?".'.~f.T~!~~~31~~.'.2.l
~~ ~ ~
~~.C?~.~~~.l!~~~9!".~~~~??:'~
@y: .,~)~~:
(5?B':':~.1?B:.~~TIPL:.ll<':' .•. ~D.O
~ ~~
a
Duct static pressure reading
b
Type of flow measuring device
c
Range of measurement of flow measuring device
d
Reading of flow measuring device
e
Interpreted air flow leakage rate
f
Duration of test (normally 15 miuutes)
~ .. ~ ~ .r''5
'2D 5
?:.~.'..~?....
.
:::::::::~::~::.::::::::::::::::::::::::::::~~~~~~~~:~~~~:~~~:~~:~;~~:3~~
Part 2 - Test particulars
Date of test ...
.:s.~ul .. ~
(~? ?!~TE.~.'!f!'.~~~~ Y!:I:E!
Q..~ ~ .. ~/ ~~.: .(~~~ .R'.G.M.~~(~~~~!
~~ .. ~
(I'R0 ~IG!
:
Carried out
~~~~~'::.~~~~.~~~.~~.~!c:~
~~
;
1-r:::.1u
(DERIVED FROM CHART SUPPLIED wm-t RIG USING "d")
<:-?Y.I,.! ••.•(~~t:1.~ .~I.~~.~~.~!~. ~~.~~?~ ~I.~~:~
IS ~
.
~~.::~:::::.::::::.... ~~;~~~~~~.~~.~::kl.~
Width and depth
or diameter
Periphery
Length
Area
millimetres
millimetres
metres
square metres
800 x 750
3100
17.550
54.405
600 x 650
2500
5.570
13.925
300 x 300
1200
1.200
1.440
305 dia.
958
7.000
6.706
250 dia.
785
4.500
3.533
TOTAL
9
80.009
Hints on Ductwork Leakage Testing
Take special care
with inaccessible
joints
500
600 x 650
800 x 750
250 dia.--\-~
300 x 300
305 dia.
---Jt-t'J..::::.llj
4595
FLEX
Keep length to a minimum
and make sure that both
end connections are
correctly sealed and that
the flexible duct itself
has no leaks.
475
In order to avoid
incorrect readings
of duct pressure
the tube from the
vertical manometer
should be connected
directly to the
ductwork under test.
TEST APPARATUS
Site on firm level base and
ensure gauges are topped up
with correct fluid and
zeroed prior to
commencing test.
Fit correct flow measuring
device.
Inclined manometer to
read leakage rate
SEQUENCE OF TEST
1.
2.
3.
4.
5.
6.
7.
8.
Prepare test sheet.
Connect and adjust test apparatus to correct pressure.
Read off leakage rate.
Reseal if necessary (allow time to cure).
Maintain test for 15 mins.
Switch off and allow to zero.
Reapply test pressure and check reading.
Record details on test sheet and obtain signature.
10
WARNING
Take care not to over pt"essurise
system under test
The dimensions on this ductwork are used in an example on page 9
800 x 750
700
5925
50
Blank off all open
ends with polythene
carefully taped into
position to avoid leaks.
Remember to blank
instrument tappings
and test holes.
rtical manometer to
d duct pressure
4175
Blank at convenient
place with access
for ease of removal
800 x 750
HOW TO FIND LEAKS
1. Look - particularly at blanks, access openings
and difficult joints.
2. Listen - with test apparatus running, leaks
should be audible.
3. Feel- running your hand (particularly if wet)
over joints can help to locate leaks.
4. Soap and Water- paint over joints and look for bubbles
5. Smoke Pellet-placed inside ductwork (obtain permission for use)
DRG No. 20433112
11
Hints on Ductwork Leakage Testing
I~~~
~
~
~
300,300
Take special care
with 1""""lbl,
. - - - - - - joints
~
~
~
,::::,
-
~
FLEX
/
Keep length to a minimum
and make sure Ihal both
cnd connections are
correctly sealed and that
the flexible duct itself
has no leaks.
In order to avoid
incorrect readings
of duct pressure
the tube from the
vertical manomeler
should be connected
directly to the
ductwork under test.
The dimensions on this ductwork are used in an example on page 9
""
600 x 650
\
"-
250 dia,':::::
/
t
;
~
j ~
111
305di~
---.1J!Q
~
250 dia.
-\
~ L'f'
I~./
LJJ
~~
~
V
r
V
V
/
Blank off all open
ends with polylhene
carefully taped into
position to avoid leaks.
Remember to blank
I
./
I
7450
475
/
,/
~
-
A-
y /\
/
aoo'750
~459S
~
instrument tappings
TEST APPARATUS
~
/
p
~
and test holes.
Site on firm level base and
ensure gauges are lopped up
with correct fluid and
zeroed prior to
commencing test.
Fit correct flow measuring
device.
::..----
~
i~
V
~
~~
I~
Inclined manometer to
read leakage rate
,Yertical manometer to
~el!d duct pressure
,.t
BI"k"
'O"~ ----
0
PI"OWlth""'~~
for
ease of removal
800 x 750
............
SEQUENCE OF TEST
I.
2.
3.
4.
5.
6.
7.
8.
250dl,j\--
II~
3500
~
t+
F'\1
\,
~
i
==- ~ ~305dl'.
BOO x 750
~
~
250dia.
r-.....
Prepare test sheet.
Connect and adjust lest apparatus 10 correct pressure.
Read off leakage rate.
Reseal if necessary (allow time to cure).
Maintain test for 15 mins.
Switch off and allow to zero.
Reapply test pressure and check reading.
Record details on test sheet and obtain signature.
WARNING
Take care not to over pressurise
system under test
HOW TO FIND LEAKS
1. Look - particularly at blanks, access openings
and difficult joints.
2. Lislen - with test apparatus running, leaks
should be audible.
3. Feel- running your hand (particularly if wet)
over joints can help to locate leaks.
4. Soap and Water- paint over joints and look for bubbles
5. Smoke Pellet- placed inside ductwork (obtain permission for use)
DRG No. 20433/12
10
11
Part Two
This section is predominantly extracted from DW/142 - Specification for Sheet Metal Ductwork, and for ease
of reference the numbering as in DW/142 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 classifications. EUROVENT document 2/2 has no
standard for a leakage class equivalent to our Class D and therefore the leakage limits for high pressure
ductwork used in DW/141 (the predecessor to DW/142) have been retained.
(5 AIR LEAKAGE STANDARDS
6.1 Limits for each pressure class
Permitted air leakage is related to four standards
of airtightness, as set out in Table 2.
6.2 Compatibility with EUROVENT
The leakage factors used in Table 2 for Classes A,
Band C are the same as those used for the classes
similarly designated in the Eurovent Document
2/2 (Air Leakage in Ductwork).
6.3 Leakage at various pressures; and other
relationships
Applying the limits specified in Table 2,
Appendix A (Table 31) sets out the permitted
leakage at each of a series of pressures up to the
maximum for each class. Included in that
appendix is a graphical presentation of the
pressure/leakage relationship; and also charts
from which may be determined leakage as a percentage of airflow for classes A, B or C.
Appendix A also gives details of the basis for the
leakage limits specfied in Table 2.
to establish conformity with the relevant leakage
limits'set out in Table 2.
Testing for leakage of ductwork within the low
and medium ranges of pressure in this specification will not form part of the ductwork contract
unless this requirement is set out in the job specification - see also Note (2) on page 1 ofDW 142.
Table 2 Air Leakage Limits
Air leakage
Leakage limit
J
2
Ii tres per second per square
metre of duct surface area
Low-pressure-
Class A
6.4 Testing for air leakage
All ductwork operating at pressures classified in
this specification as 'high pressure' shall be tested
0.027 x p'.65
Medium-pressureClass B
0.009 x pO.65
High-pressureClass C
0.003 X po."
High-pressureClass D
0.001 x p"'"
where p
IS
the differential pressure In pascals
APPENDIX A - AIR LEAKAGE FROM DUCTWORK
A.I.3 Pressure/leakage relationship
For a given pressure, the leakage through an
orifice of a given area will vary according to its
shape. With installed ductwork, the leakage
orifices are of differing shapes, so a precise value
cannot be given to the pressure/leakage relationship. However, Swedish tests on a variety of constructions have shown that for ductwork operating within the range covered in this specification, leakage can be taken as proportional to
pressure to the power of 0.65. (This value has
been adopted by EUROVENT in preparing their
Document 2/2 - Air Leakage in Ductwork - see
Appendix L - and has also been adopted in this
specification (see Table 2) and has been applied
in Table 31.
A.I GENERAL CONSIDERATIONS
A.I.I Leakage points in ductwork
Air leakage in installed ductwork occurs almost
entirely at the longitudinal seams and the cross
joints, particularly at the corners, and at the
intersection of the seams and cross joints.
A.I.2 Leakage related to duct area
In practice, leakage can be taken as proportional
to the surface area of the ductwork, whether
rectangular or circular, even though there may be
considerable variation in different sections of a
complete system because of the changing sizes of
the ducts and the number and variety of the fittings. The surface area is easily calculable as part
of the design procedure.
13
A.2 LEAKAGE LIMITS - RELATIONSHIPS
A.2.t Limits for each pressure class
Applying the values given in Table 2 (page 13).
the permitted leakage at each of a series of pressures up to the maximum for each class is set out
in Table 31.
A.2.2 Graphical presentation
The pressure/leakage relationships given In
Table 31 are expressed graphically in Fig. 169.
A.2.3 Leakage as a percentage of airflow
As air leakage is related to surface area of the
ductwork, it cannot in advance of the detailed
calculations be expressed as a percentage of total
airflow, nor will a percentage loss be acceptable
as a standard of performance. However, application of the leakage limits to a variety of ductwork
systems indicates that under oparating conditions
air losses will usually be within 6 per cent of total
airflow for the low-pressure class and 3 per cent
for the medium-pressure class. For the highpressure class, air loss is likely to be between 2
and 0.5 per cent, according to which leakage limit
is applied.
A. 2.4 Special cases
The percentages mentioned in A.2.3 apply to
normal ratios of duct area to airflow; but where
the ratio is high (e.g. long runs of small ducts), it
may be necessary for the designer to specify a
higher standard of airtightness in order to keep
the actual leakage within an acceptable limit.
A.2.5 Designer's required calculations
Designers will be concerned with the total loss of
air through leakage which must be allowed for
the ductwork, and will need to:
(a) calculate the pressure class;
(b) calculate the surface area and estimate
the mean system pressure difference for
the ductwork system (or part ofsystem);
Alternatively, the designer may:
(d) decide on the maximum total leakage that
he can accept;
(e) calculate the surface area and estimate the
mean system pressure difference for the
ductwork system (or part of system) and
from these determine the required pressure class.
A.2.6 Leakage of complete system
DW/142 deals only with the ductwork. The leakage characteristics of plant items and accessories
are not within the control of the ductwork contractor, and therefore any leakage limits and leakage testing called for under DW/142 shall be
understood to apply only to the ductwork itself.
Table 31
(c)
Low-pressure
Class A
Med-prcssure
Class B
Class C
J
2
3
4
100
0.54
0.84
0.28
300
1.10
0.37
400
1.32
1.53
0.44
5
0.51
0.58
0.19
0.64
0.21
800
0.69
0.75
0.23
0.25
0.80
0.27
I HXI
0.29
0.10
1200
0.30
0.10
1300
14(XI
0.32
0.11
15m)
0.33
0.35
0.12
1600
17m)
0.36
0.12
11.38
0.13
0.13
1800
1900
0.39
0.40
2000
0.42
2100
14
Class D
0.18
600
700
9ml
10m)
I
I
Litres per second per square metre of surface area
200
500
calculate the total leakage using the appropriate rate from Table 31.
Maximum leakage of ductwork
High-pressure
Static
pressure
differential
Pa
Definition of mean pressure
Pm = PI + P2, where:2
Pm = mean or average pressure.
P I = operating pressure at the beginning of the
ductwork system or part of system.
P2 = operating pressure at the end of the ductwork system or part of system.
IT IS RECOMMENDED THAT MAXIMUM
TEST PRESSURES AND LEAKAGE RATES
SHOWN IN TABLE 32, PAGE /7, BE
ADOPTED.
Air leakage rates
0.11
0.14
0.14
0.14
2200
0.15
23ml
0.15
2400
0.16
2500
0.16
Fig. 169
Permitted leakage at various pressures
(a) LOW & MEDIUM PRESSURE CLASSES - LEAKAGE LIMITS
1::
~
6l
1.5
~
b 1.25
e
~
.."'ill.
0" 1.0
""g 0.75
~
..""'
c . 0.5
~
()
IIKl
21Xl
31Ml
-lOO
son
600
7110
XOO
t)O(l
Pressure difference in pascals
11l()O
(b) HIGH PRESSURE CLASSES - LEAKAGE LIMITS
'~"
'~" 0.40
't:
=
"'
~ 0.35
""~
~IU()
~
'&" (1.25
.."'ill.
,
"C ILO
=
o
~
:: lJ.IS
.5
~(UIS
.!.'i
3
()
}50
500
750
1000
12;i(J
1500
1750
Pressure difference in pascals
15
200ll
25(}()
Fig. 170
Leakage as percentage of airflow
1000
f-- .. 1000
600
l-
/'
1000
200
60
v:
1/
200
6001-
.
I- 400
40-
--
100
200
60
40100
80
,
10
,
,..e.-
b"L.-
100
60
/'
l/
f.:--
V
If
/'
2O!?L-
~
./
-
-
40
80
~
..
V
80
V
~
V
-,.
20
i/
I
101~ 1// V
--
1/
1/
1/ 1/
1/
.
6
20
60
,
4
lO L
"
"u
S
I
br'
20
0
,
10
V
,
6
.
-
40
10
2
V
V
1/ 1/
V 1/
'00
60
6
V
~
/'
'00
20
1--
/'
2000
100
600
/'
1-- .. .-
600
200
600
l/
j,.L
21-/
Y
1
200
5
....
+
j'/
1/
I
,
<
~
./
1
"
, , ,
'00
!
I,
,
t
600 800 1000
CLASS A
2000
I
I
I
1
/
!
,
, I!
2
3
4
CLASS 8
,
!
!
CLASSC
I
,,
!
2
1
u
I,
5 6I
!
!
.5
LEAKAGE(Us)
,
,
10
3
, , ,,
4
,
5 6
1
,
'
!
!
2
3
,
!
PERCENTAGE lEAKAGE
MEAN DIFFERENTIAL PRESSURE (Pal
Examples of use of charts
Mean differential pressure
Duct area
.
Airflow
.
Example I
Class A
320Pa
80m2
2 m3/s
.
Calculated
Maximum permitted leakage
Percentage of airflow
.
91.8
4.58
Based on charts prepared by EUROVENT.
reproduced by kind permission.
16
Example 2
ClassB
800Pa
200m2
6m3 /s
Chart
reading
92
4.6
Calculated
138.8
2.31
Chart
reading
139
2.3
APPENDIX B - AIR LEAKAGE TESTING PROCEDURE
B.3 Testing to be completed before insulation, etc.
Testing shall be satisfactorily completed before
insulation or enclosure of the ductwork and before
terminal units (if any) are fitted.
B.l GENERAL
Section 6 (page 13) of this specification deals with
the performance requirements of ductwork in
respect of air leakage, and Table 31 (Appendix A)
tabulates the limits of leakage applicable to each
class of ductwork. Appendix B is solely concerned
with recommendations for the testing procedure.
B.4 Retesting procedure where necessary
B.4.1 The air leakage ra.te for any section shall
not be in excess of the permitted rate for that
section. If a first test produces leakage in excess
of the permitted maximum, the section shall be
resealed and retested until a leakage not greater
than the permitted 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 ductwork under test shall not be counted as part of
the tested ductwork, except where the whole of
the ductwork is required to be tested.
B.2 Extent of ductwork to be tested
B.2.1 The procedure set out in this section is
limited to the ductwork. Terminal connections,
and items such as air handling deYices, terminal
boxes, sound attenuators, heat exchangers,
builder's work construction, are excluded from
the tests.
B.2.2 The proportion of the ductwork to be
tested and the method of selection (where not
included in the job specification) should be
determined in collaboration between the
designer and the ductwork contractor. Where
the method is by random selection, the use of
polythene sheet or similar insertion blanks between duct cross joints and duct-mounted components will assist in avoiding delays in installation when tests are being carried out.
B.2.3 To enable the blank to be cut out after the
testing is completed, access may be required
adjacent to each blank. This procedure used on
either side of a duct-mounted component will
enable the component to be included in a subsequent additional test if specified.
B.2.4 Alternatively, rigid removable blanking
plates can be used, although this involves
remaking joints.
Table 32
B.S Minimum area to be tested
The section of ductwork to be tested shall have an
area large enough to enable the test apparatus to
register a measurable leakage.
8.6 Test pressures and leakage rates
The maximum pennissible leakage rates for the
full range of pressures are given in Table 31. The
recommended test pressures for the various classes
of ductwork are set out in Table 32, and unless
otherwise specified, the choice of test pressure
shall be at the discretion of the test operator.
Recommended maximum test pressures (with leakage rates)
Maximum leakage of ductwork
Static
pressure
differential
Low-pressure
Class A
3
2
J
High-pressure
Class C
Class D
4
5
Litres per second per square metre of surface area
Pa
200
400
800
1200
1500
2000
Medium-pressure
Class B
0.84
1.32
0.44
0.69
0.30
0.35
--
..
~
'" .
....
..,""'........
17
-
0.12
0.14
B.7 Test apparatus
B.7.1 The accuracy of the test apparatus shall
be within:
± 10 per cent of the indicated flow rate, or
0.4 litres per second, whichever is the
all joints which fall outside the scope of the
testing procedure, Le., joints between tested
sections of ductwork and between' ductwork
and other units.
B.8.5 Due notice of tests shall be given, so that
arrangements for witnessing the tests, if
required, can be made.
greater; and
± 5 per cent at the indicated static pressure
in the duct under test.
B.7.2 The test apparatus 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
B.9 Testing sequence
The recommended sequence of testing is as
follows.
B.9.1 Complete Part 1 of the Test Sheet.
B.9.2 Connect test apparatus to section of ductwork to be tested.
B.9.3 Adjust test apparatus until the static
pressure differential is obtained.
B.9.4 Check that the measured leakage is within the permitted rate. (No addition shall be
made to the permissible leakage rate for access
doors, access panels or dampers where these are
included in the ductwork.)
B.9.5 Maintain the test for fifteen minutes and
check that the leakage rate has not increased.
B.9.6 Reduce pressure in section to zero by
switching off the fan; then immediately re-apply
test pressure to establish that the air leakage
is used.
B.7.3 A diagram of a suitable test apparatus is
given in Fig. 171.
B.8 Procedure
B.8.1 The section of ductwork to be tested for
air leakage shall be sealed. Main ducts should
be provided 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.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
practicable, be checked by external visual
rate is not greater than the previous reading.
B.9.7 Record details on Part 2 of the Test Sheet
and complete, including witnessing.
examination.
B.8.3 Sufficient time shall be allowed between
erection and leakage testing for sealants to cure.
B.8.4 Special care must be exercised in making
Fig. 171
B.I0 Air leakage test sheet
A specimen of a suitable Test Sheet is given on
page 9.
Diagram of typical apparatus for air leakage tests
Bleed valve (not necessary
Blanking
/plate
L
Flow measuring device
(may be located on
the suction side of "the fan)
"
if variable speed
/fanused)
Duct under test
Electrically
driven fan
Duct tcst
pressure gauge _
Inclined gauge
18