AS 4254 1995 ductwork for air handling systems in buildings

TABLE 2.2.2 LEAKAGE RATES IN UNSEALED LOW PRESSURE DUCTS2 surface area 25 60 125 250 0.52 0.94 1.46 2.27 2.3 RECTANGULAR DUCT REINFORCEMENT 2.3.1 General Ducts shall be reinforced as fol

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AS 4254-1995 Ductwork for air-handling systems in buildings

Licensed to LUU MINH LUAN on 26 Feb 2002

AS 4254—1995

Ductwork for air-handling systems

in buildings

and Air Conditioning It was approved on behalf of the Council of Standards Australia

on 21 September 1994 and published on 5 January 1995

The following interests are represented on Committee ME/62:

Association of Consulting Engineers AustraliaAustralian Assembly of Fire AuthoritiesAustralian Construction ServicesAustralian Institute of Refrigeration Air Conditioning and HeatingAustralian Uniform Building Regulations Coordinating CouncilBuilding Owners and Managers Association of AustraliaCouncil of Air Conditioning and Mechanical Contractors Associations of AustraliaDepartment of Health, New South Wales

Fire Protection Industry Associations of AustraliaInsurance Council of Australia

Metal Trades Industry Association of AustraliaState Projects, New South Wales

Additional interests participating in preparation of Standard:

Council of the City of Sydney

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Full details of all Australian Standards and related publications will be found in the Standards Australia Catalogue of Publications; this information is supplemented each month by the magazine ‘The Australian Standard’, which subscribing members receive, and which gives details of new publications, new editions and amendments, and of withdrawn Standards.

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PUBLISHED BY STANDARDS AUSTRALIA(STANDARDS ASSOCIATION OF AUSTRALIA)

This Standard was prepared by the Joint Standards Australia/Standards New ZealandCommittee ME/62 on Mechanical Ventilation and Air Conditioning In the preparation ofthis Standard, consideration was given to a number of publications and relevant Standards.This Standard follows a number of requirements set out in the Sheet Metal and AirConditioning Contractors National Association’s (SMACNA) HVAC Duct ConstructionStandards for metal and flexible ducts, but with the requirements adapted to the products

of local Australian industries

The objective of this Standard is to provide guidance to designers, manufacturers andinstallers of air-handling systems for buildings

The approach to using SMACNA as the basis for an Australian Standard was stronglyinfluenced by —

(a) the extensive long-term background of SMACNA, which led this document to beregarded as well developed; and

(b) the use of SMACNA in Australia over a considerable period as the basis for ductconstruction

Assistance gained from SMACNA is hereby acknowledged

The terms ‘normative’ and ‘informative’ have been used in this Standard to define theapplication of the appendix to which they apply A ‘normative’ appendix is an integralpart of a Standard, whereas an ‘informative’ appendix is only for information andguidance

Statements expressed in mandatory terms in notes to tables and figures are deemed to berequirements of this Standard

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Care should be taken to ensure that material used is from the current edition of the Standard and that it is updated whenever the Standard is amended or revised The number and date of the Standard should therefore be clearly identified.

Page

SECTION 1 SCOPE AND GENERAL

1.1 SCOPE 4

1.2 NEW DESIGNS AND INNOVATIONS 4

1.3 APPLICATION 4

1.4 REFERENCED DOCUMENTS 4

1.5 DEFINITIONS 5

1.6 GENERAL REQUIREMENTS 7

1.7 STATIC PRESSURE CLASSIFICATION 7

1.8 GALVANIZED STEEL THICKNESS 8

1.9 TESTING 8

SECTION 2 DUCT CONSTRUCTION AND INSTALLATION 2.1 DUCT WORK 9

2.2 DUCT SEALING 9

2.3 RECTANGULAR DUCT REINFORCEMENT 12

2.4 ROUND DUCT CONSTRUCTION 46

2.5 OVAL DUCT CONSTRUCTION 54

2.6 HANGERS AND SUPPORT SYSTEMS 56

2.7 DUCT LINERS AND INSULATION 64

2.8 FLEXIBLE DUCTWORK 66

SECTION 3 EXTERNAL EQUIPMENT INSTALLATION 3.1 GENERAL 71

3.2 ROOF PENETRATIONS 71

3.3 CONNECTION TO EQUIPMENT 71

3.4 SEALING OF EXTERNAL DUCTWORK 71

SECTION 4 FUNCTIONAL CRITERIA 4.1 DEFLECTION 76

4.2 MODELS FOR FUNCTIONAL STANDARDS 76

APPENDICES A PROCEDURE FOR RATING DUCT CONSTRUCTION METHODS RELATIVE TO THE CONSTRUCTION TABLES 78

B ‘J’ AND ‘I’ REINFORCEMENT RELATED TO ‘EI’ VALUES 80

C ALLOWABLE LOADS FOR TRAPEZE ANGLES 81

D CIRCULAR EQUIVALENT OF RECTANGULAR DUCTS 83

E WEIGHTS AND AREAS OF RECTANGULAR GALVANIZED STEEL DUCTS 84

F WEIGHTS AND AREAS OF CIRCULAR GALVANIZED STEEL DUCTS 85

STANDARDS AUSTRALIA

Australian Standard Ductwork for air-handling systems in buildings

1.3 APPLICATION This Standard applies to ductwork for air-handling systemsdesigned in accordance with the requirements of AS 1668.1 and AS 1668.2

1.4 REFERENCED DOCUMENTS The following documents are referred to in thisStandard:

AS

1397 Steel sheet and strip — Hot-dipped zinc-coated or aluminium/zinc coated

1449 Wrought alloy steels—Stainless and heat-resisting steel plate, sheet and strip

1530 Methods for fire tests on building materials, components and structures

1530.1 Part 1: Combustibility test for materials

1530.2 Part 2: Test for flammability of materials

1530.3 Part 3: Simultaneous determination of ignitability, flame propagation, heat

release and smoke release1530.4 Fire-resistance tests of elements of building construction

1599 Pressure sensitive adhesive packaging tapes

1668 The use of mechanical ventilation and air conditioning in buildings

1668.1 Part 1: Fire and smoke control

1668.2 Part 2: Mechanical ventilation for acceptable indoor-air quality

1682 Fire dampers

1682.2 Part 2: Installation

1734 Aluminium and aluminium alloys—Flat sheet, coiled sheet and plate

1866 Aluminium and aluminium alloys—Extruded rod, bar, solid and hollow shapes

1903 Reflective foil laminate

2338 Preferred dimensions of wrought metal products

3666 Air handling and water systems of buildings — Microbial control

3679 Structural steel

3679.1 Part 1: Hot-rolled bars and sections

UL 181 Factory made air ducts and air connectors

1.5 DEFINITIONS For the purpose of this Standard, the definitions below apply.

1.5.1 Airflow rate (herein referred to as ‘flow rate’) — the volumetric flow rate

derived from the mass flow rate by dividing it by the density, assumed to be 1.2 kg/m3(1.2 g/L)

1.5.2 Air-handling plant— a component part of an air-handling system that includes

equipment providing air movement, as well as equipment for the purpose of controllingthe direction, rate of airflow, division of airflow and condition of air, i.e concentrationlevel of contaminants, temperature and humidity

1.5.3 Air-handling system — a system for the purpose of directing air in a controlled

manner to or from specific enclosures by means of handling plant, ducts, plenums, distribution devices and automatic controls

air-1.5.4 Air-pressurization system — an air-handling system which establishes a pressure

differential to provide a flow of air from a fire-isolated escape route into normallyoccupied spaces

1.5.5 Air outlet — any opening through which air is delivered to an enclosure by an

air-handling system of a building

1.5.6 Approved and approval — approved by, or the approval of, the regulatory

authority concerned

1.5.7 Combustible— deemed combustible when tested in accordance with AS 1530.1.

1.5.8 Compartment — a fire compartment as defined in the Building Code of Australia 1.5.9 Downstream — in the direction of airflow.

1.5.10 Duct — a component part of an air-handling system, intended for the passage of

air from one part of an air-handling system to another (See also definition of ‘plenum’)

1.5.11 Duct liner — internal lining of duct usually provided for thermal or acoustic

insulation, or both, including the facing material thereon

1.5.12 Exhaust air — air, other than return air, removed from an enclosure by

mechanical means and discharged to atmosphere

1.5.13 Exhaust air intake — any opening through which air is extracted from an

enclosure by an air-handling system of a building

1.5.14 Exhaust outlet — an outlet from an air-handling system, discharging toatmosphere

1.5.15 Facing material — thin flexible material (e.g reflective foil laminate) used for

the facing of duct liner or insulation or for the manufacture of flexible duct

1.5.16 Fail-safe — the position the device reverts to upon loss of operating power as

applicable

1.5.17 Fire alarm — a device which may be operated manually or automatically and

which is intended to provide warning of the existence of a fire

1.5.18 Fire damper — a complete assembly complying with AS 1682.2.

1.5.19 Fire-isolated — separated by fire-resistant construction.

1.5.20 Fire resistance level (FRL) — the grading periods in minutes determined in

accordance with AS 1530.4 for—

(a) structural adequacy;

(b) integrity; and

(c) insulation, expressed in that order

1.5.21 Fire-resisting — describes an element of construction, component or structure

which, by requirement of the regulatory authority, has a specified FRL

1.5.22 Flexible connection — a section of flexible material used at junctions between

ductwork and items of plant that are subject to vibration

1.5.23 Flexible duct — a factory-made, preformed duct that can be bent or compressed

by hand

1.5.24 Hood — a component part of a local exhaust system intended for collecting

effluents

1.5.25 Infiltration air — air, other than supply air and make-up air, that enters an

enclosure or an air-handling system in an uncontrolled manner

1.5.26 Insulated flexible duct — flexible duct wrapped in a blanket of thermal insulating

material

1.5.27 Insulation— external lining of rigid or flexible duct usually provided for thermal

or acoustic insulation, or both, including any facing material thereon

1.5.28 Jacket/sleeve — an air and vapour tight enclosure around the insulating blanket

applied to insulated flexible duct

1.5.29 Joint — any surface connection made on the perimeter of a duct, other than a

seam

1.5.30 Leakage air — air, other than exhaust air, return air and relief air, that escapes

from an air-handling system in an uncontrolled manner

1.5.31 May — indicates the existence of an option.

1.5.32 Objectionable effluent —a ny unwanted airborne constituents that may reduce the

acceptability of air

1.5.33 Outdoor air — air outside the building.

1.5.34 Outdoor air intake — any opening through which outdoor air is admitted to an

air-handling system of a building

1.5.35 Plant room — a room which contains items of plant or machinery.

1.5.36 Plenum — an air compartment or chamber, intended for the passage of air, to

which one or more ducts may be connected and which forms part of an air-handlingsystem

1.5.37 Recycled air — that portion of indoor air removed from enclosures as return air

and returned as part of the supply air, by mechanical means

1.5.38 Regulatory authority — an authority having statutory powers to control design,

construction, installation, operation or testing of air-handling systems in buildings

1.5.39 Relief air — air that flows from an enclosure in a controlled manner by other than

mechanical means

1.5.40 Required — required by any government act, regulation, by-law or statutory rule,

or by any regulatory authority

NOTE: Fire insurance underwriters and other bodies may have requirements in excess of thoserequired by regulatory authorities

1.5.41 Return air — air removed from an enclosure by mechanical means All of the

return air may be expelled as spill air, or all or part of it may be recycled

1.5.42 Seam — any surface connection joining two longitudinally-oriented edges of duct

surface material occurring between two joints

1.5.43 Shall — indicates that a statement is mandatory.

1.5.44 Should— indicates a recommendation.

1.5.45 Spill air — that portion of return air that is not recycled.

1.5.46 Supply air — air introduced into an enclosure by mechanical means.

1.5.47 Upstream — against the direction of airflow.

1.6 GENERAL REQUIREMENTS A duct system is a structural assembly, theprimary function of which is to convey air between specific points To fulfil this function,the duct assembly must perform satisfactorily with regard to certain fundamentalperformance characteristics

Elements of the assembly are sheets (duct envelope), reinforcement, seams and joints.With regard to the duct assembly and its elements, theoretical or practical limits must beestablished for:

(a) Dimensional stability (deformation and deflection) under positive or negativepressure applications or static loads

(b) Leakage under positive or negative pressure

(c) Vibration

(d) Support (including any supplemental loads)

The following Items (e) to (i) are not covered in detail in this Standard, but are includedfor information:

(e) Noise generation and transmission

(f) Exposure to damage from—

(i) transportation and handling;

(ii) weather and temperature extremes;

(iii) flexure cycle;

(iv) chemical corrosion; and(v) other in-service conditions specific to the installation

(g) Impact loading such as —

(i) fire;

(ii) earthquake; or(iii) sudden stoppage of airflow

(h) Cleanability

(i) Resistance to airflow

In establishing limitations for these factors, consideration must be given to the effects ofpressure differential across the ductwork, airflow friction losses, air velocity, infiltration

or exfiltration, as well as the inherent strength characteristics of the duct components.Construction methods that will permit an economic attainment of the predicted anddesired performance must be determined

1.7 STATIC PRESSURE CLASSIFICATION The pressure classification numberdenotes construction suitable for a maximum level not less than the maximum operatingpressure in the portion of the system receiving classification from the designer Thepressure classifications are as follows:

Static pressure Pressure class Operating pressure range, Pa

125250500750

1.8 GALVANIZED STEEL THICKNESS All galvanized steel thicknesses nominated

in this Standard shall be read as base metal thickness

1.9 TESTING Where bulk insulation, facing materials and flexible or rigid ductworkmaterials are required to be subjected to fire tests, all such testing shall be carried out by

a registered testing authority in accordance with the Building Code of Australia Samplessubmitted for prototype testing shall be identical to manufactured product supplied under

a fire test certificate In order for supplied manufactured product to be identified withsupplied test certificates the certificates shall include the following minimum productdata:

(a) Manufacturer’s name or registered trademark and product name

(b) Thickness, R value, density of bulk insulation and all flame retardants used

(c) Nominal grammage (g/m2) of facing or lining material and all flame retardants used.(d) For facings and lining materials of a composite nature, bonded together with fireretardant adhesives during inner core or sleeve manufacture the adhesive type, allflame retardants used in the adhesive and the weight of adhesive applied (g/m2).Tested product shall comply with all of the test requirements of this Standard beforecompliance can be claimed

Regardless of pressure classifications, nothing herein is intended to preclude the use ofproducts or methods demonstrated to the satisfaction of the specifying authority to beequivalent in performance for the particular application.

If ductwork is required to have a fire resistance level (FRL), the ductwork and applied fireprotection system shall be identical to a prototype that has been submitted to a fireresistance test in accordance with AS 1530.4, or satisfies the requirements of the BuildingCode of Australia (BCA) This may require ductwork design to exceed the minimumrequirements of this Standard

NOTE: All ductwork should, where practicable, be installed allowing clearances for accesswhen carrying out testing, commissioning and maintenance routines

2.1.2 Kitchen exhaust ductwork Ductwork used in relation to kitchen exhaust systemsshall be constructed from galvanized sheet steel, stainless steel or other approved rigid,hard faced, fire retardant material, impervious to grease, smooth and free fromobstructions on the internal surfaces An internal masonry finish shall not be permitted

Vertical take-off ducts shall not be located directly over hood exhaust openings

Liquid-tight cleanouts, easily accessible and large enough to enable access to clean theinternal surfaces of the duct or plenum, shall be provided —

(a) at each change in direction of ductwork;

(b) at each duct junction;

(c) in horizontal runs at intervals of not more than 3 m; and

(d) at such other positions as may be specified

Horizontal ducts shall be installed with a rise in the direction of air flow of at least 1 in200

Flexible connections where required or permitted shall be of woven ceramic fibre withimpervious smooth linings or similar non-collapsible grease proof and fire resistantmaterial, and shall not exceed 300 mm in length

2.2 DUCT SEALING

2.2.1 General Ducts shall be sealed in accordance with Table 2.2.1 All sealantmaterials that are used on ductwork shall have, when tested in accordance with AS 1530.3 —(a) a smoke developed index not greater than ‘3’ (see AS 1530.3); and

(b) a spread of flame index not greater than ‘0’ (see AS 1530.3)

Where sealing is a requirement of this Standard, the following apply:

(i) Adhesives, mastics, gaskets, tape systems or combinations thereof are used to closeopenings in the surface of the ductwork through which air leakage would occur.(ii) Continuous welds are used.

(iii) Where distinctions between seams and joints are made, a seam is defined as thejoining of two longitudinally orientated edges of duct surface material occurringbetween two joints Helical lock seams are exempt from sealant requirements Allother duct surface connections made on the perimeter are deemed to be joints Jointsare inclusive of, but not limited to, girth joints, branch and sub-branch intersections,fitting subsections, louvre and air terminal connections, access doors, access panelframes and joints, duct, plenum and casing abutments to building structures

(iv) Sealing requirements apply equally to positive and negative pressure modes

(v) Externally insulated ducts located outside of buildings shall be sealed prior to beinginsulated as though they were inside For ducts located on the exterior of buildingsand exposed to weather, any potential points for air leakage shall be treated withexterior duct sealant An exterior duct sealant is defined as a sealant that is ‘capable

of forming a positive air and watertight seal, bonds well to the material involved,remains flexible with material movement and has a service temperature range of

−10°C to 78°C’ If exposed to direct sunlight, it shall be ultraviolet and ozoneresistant or shall, after curing, be coated with a material that will provide therequired resistance

(vi) The sealing requirements within this Standard do not contain provisions to —

(A) resist chemical attack;

(H) withstand continuous vibration visible to the naked eye;

(I) be totally leak-free within an encapsulating vapour barrier;

(J) create closure in portions of the building structure used as ducts, e.g ceiling

plenums, shafts, pressurized compartments; and(K) withstand temperatures outside the range of −10°C to 78°C, except for ducts

mounted outside the building

TABLE 2.2.1 DUCT SEALING REQUIREMENTS

Seal

Static pressure classification, Pa

A All transverse joints, longitudinal seams and

B All transverse joints and longitudinal seams 750

NOTE: Below 500 Pa, ductwork is to be sealed only where required by the designer.

Sealants, gaskets and tapes used to seal ductwork shall comply with the following:

(1) Sealants, gaskets and tapes shall be non-toxic under service conditions.

(2) All sealing materials shall maintain their elasticity and adhesive properties throughthe temperature range −10°C to 78°C

(3) All sealing materials shall be resistant to oil and water, after curing

(4) Adhesive tapes shall have properties not less than the polyethylene tape referenced

in AS 1599 (Serial Number 18) and shall be compatible with the sealant, whichshall not decrease the bonding quality Adhesive tapes shall not be used as theprimary sealing agent

NOTES:

1 Where special considerations are required, as in the pharmaceutical industry, the designershall stipulate the type of sealant to be used

2 It is not a requirement of this Standard that ductwork be leak tested

2.2.2 Kitchen exhaust ductwork sealing Ductwork used in relation to kitchen exhaustsystems shall be sealed as follows:

(a) Joints and seams shall be continuously welded, grooved or lapped, riveted andsoldered to form smooth-faced liquid-tight seals Other smooth-faced joints andseams of satisfactory mechanical strength and liquid-tightness may be appropriate.Liquid sealants or mastics shall not be used for sealing joints or seams unless —(i) held in compression between the surfaces of joints and seams; and(ii) of a type unaffected by grease, water or cleaning agents

(b) The girth joints of vertical risers shall be butt welded or flanged and bolted

2.2.3 Sealing media The following media are used for duct sealing:

(a) Mastics Mastics are putty-like materials the plasticity of which makes themsuitable for sealing where they can be moulded to suit the conformation of the area

to be sealed An acceptable ‘airtight’ seal can only be obtained when the mastic isheld in a joint either by lapping metal surfaces or by compression of the twosurfaces

(b) Liquids Liquid sealants are to be applied by brush or pump and shall only be usedwhere they are held in the joint by lapping metal surfaces and surfaces undercompression

(c) Gaskets Gaskets are used to seal between two surfaces under compression that may

be released periodically The material for the gasket shall be chosen so that itselastic memory and compressibility suit the degree and frequency of compression atthe joint to be sealed

(d) Tapes Tapes are used to seal insulation joints that are ‘butted’ or ‘sleeved’ Onflexible duct joints, they are used to provide a seal, a strong bond or a vapourbarrier and are required to have tensile strength to resist tearing They should havefire hazard properties at least equal to those stated in Clause 2.2

2.2.4 Surface preparation Surfaces to receive sealant shall be adequately cleaned andshall be free from oil, dust, dirt, rust, moisture and other substances that may inhibitbonding

2.2.5 Leakage Leakage is a function of static pressure, of manufacturing and ofinstallation techniques The amount of leakage in a system is therefore significantlyrelated to system size Airtightness in ducts cannot and need not be absolute, but ductsmust be sufficiently airtight to ensure economical and quiet operation of the system.Airtightness of the necessary order can be achieved by utilizing the static pressureconstruction class most suitable for the actual operating condition of the system andproper sealing of the ductwork In low pressure system design, leakage rates, inaccordance with Table 2.2.2, shall be applied to unsealed ducts

TABLE 2.2.2 LEAKAGE RATES IN UNSEALED LOW PRESSURE DUCTS

2

(surface area)

25 60 125 250

0.52 0.94 1.46 2.27

2.3 RECTANGULAR DUCT REINFORCEMENT

2.3.1 General Ducts shall be reinforced as follows:

(a) Unless specified otherwise, rectangular ducts shall be constructed and reinforced inaccordance with the following:

(i) Tables 2.3(A) to 2.3(G) for minimum duct metal thickness and minimum

joint reinforcement

(ii) Table 2.3(H) for types of joints and joint rating

(iii) Table 2.3(I) for types of intermediate reinforcement and reinforcement

ratings

(iv) Figures 2.3(A) and 2.3(B) for longitudinal seams and seam locations

(v) Figure 2.3(C) for tie rod details

(vi) Figures 2.3(D) to 2.3(Q) for rectangular duct construction

(B) if constructed with intermediate reinforcement at 750 mm centres a metal thickness of0.6 mm with a joint rating of J7 and intermediate reinforcement with a rating of I7.(b) Unless specified otherwise, the tables are based on using prime quality lockforminggalvanized steel, Grade G2 or G3 to AS 2338 with Z275 coating to AS 1397.Uncoated steel, prepainted steel, steel with metal coating such as aluminium oraluminium-zinc compounds and stainless steel may be used provided that aminimum corresponding base metal thickness and material strength is provided.Lockforming grades of such material must be used The use of alternative materialsrequires independent specification or approval by a designer The surfaceconditions, hardness, ductility, corrosion resistance and other characteristic features

of such materials must be judged acceptable for the service planned by the designer.(c) Unless otherwise specified, reinforcement components may be uncoated steel orgalvanized steel

(d) A reinforcement rating higher than indicated must be substituted when the tables donot provide the specific construction details for a lower classification A higherrated construction member may otherwise be substituted for convenience

(e) Joint spacing on unreinforced ducts is unlimited On ducts that requirereinforcement, joint spacing is unrestricted except that the joint itself must qualifyfor the minimum rating associated with the reinforcement spacing.

(f) Fittings shall be reinforced similarly to sections of straight duct On size changefittings the greater fitting dimension determines the duct metal thickness Wherefitting curvature or internal member attachments provide equivalent rigidity suchfeatures may be credited as reinforcement

(g) Duct wall thickness, joints, seams and reinforcements must be related practicably toprovide proper assembly

2.3.2 Longitudinal seams for rectangular duct (LS) Longitudinal seams forrectangular ductwork (see Figure 2.3(A)) shall be —

(a) suitably selected for the material, pressure classification and other constructiondetail applicable for the service; and

(b) formed and assembled with proper dimension and proportion for tight and securefit-up Notching shall be minimal and consistent with transverse joint make-upneeds

NOTES:

1 Seams may be of butt-weld, corner-weld, tack-weld or spot-weld design They may also be

of spiral lock-seam type

2 Pittsburgh seam (LS-1): Pocket depth varies from 6 mm to 15 mm depending on metalthickness and roll form equipment The most common sizes are 6 mm and 10 mm Used onstraight duct and fittings

3 Button punch snaplock (LS-2): 12 mm pocket depth is recommended for ducts where themetal thickness does not exceed 1.0 mm Not recommended for aluminium or other softmetal duct The seam may be used for 750 Pa static or less; however, screws or rivets must

be added at the ends of the seams on all ducts, when the duct is over 1200 mm width Notrecommended for pressure above 750 Pa, or for any ductwork in riser shafts

4 Grooved seam typical (LS-3): Type illustrated is also known as pipelock, flat lock orgrooved seam

5 Double corner seam (LS-4): Machines are available to automatically close this seam Insome localities it is known as a slide lock seam

6 Standing seam (LS-5): Unless otherwise required by the application, a 20 mm seam isnormally used up to 1200 mm duct width, with 35 mm seams for larger ducts May be used

on interior of the duct with due consideration for velocity level Fasten together at ends and

at 200 mm intervals

7 Single corner seam (LS-6): The seam is fastened at ends and intervals

2.3.3 Tie rods (t) Tie rods shall be provided where required in accordance with thefollowing (see Figure 2.3(C)):

(a) Tables 2.3(A) to 2.3(G) show areas where tie rods may be used

(b) Tie rods shall be attached to one of the members of the transverse joints whenproprietary made flanges or matching angle flanges are used See tie rod details,Figure 2.3(C)(d)

(c) When proprietary made flanges or matching angle flanges are not used, tie rodsshall be attached to the wall of the duct at a position not exceeding 35 mm from thetransverse joint Backing plates or plate washers shall be used on both sides of theduct wall and the locking nuts or spacers See rod details, Figure 2.3(C)(a), (b) and(c)

(d) Flat bar spacers may be used in lieu of tie rods See rod details, Figure 2.3(C)(e)

TABLE 2.3(A) RECTANGULAR DUCT REINFORCEMENT

125 Pa static pos or neg.

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

NOTE: t denotes tie rod at centre of transverse joint or intermediate reinforcement at a maximum of

1200 mm centres, whichever is the smaller.

TABLE 2.3(B) RECTANGULAR DUCT REINFORCEMENT

250 Pa static pos or neg.

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

1200 mm centres, whichever is the smaller.

TABLE 2.3(C) RECTANGULAR DUCT REINFORCEMENT

500 Pa static pos or neg.

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

1200 mm centres, whichever is the smaller.

TABLE 2.3(D) RECTANGULAR DUCT REINFORCEMENT

750 Pa static pos or neg.

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

1200 mm centres, whichever is the smaller.

TABLE 2.3(E) RECTANGULAR DUCT REINFORCEMENT

1000 Pa static positive only

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

1200 mm centres whichever is the smaller.

TABLE 2.8(F) RECTANGULAR DUCT REINFORCEMENT

1500 Pa static positive only

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

1200 mm centres, whichever is the smaller.

TABLE 2.3(G) RECTANGULAR DUCT REINFORCEMENT

2500 Pa static positive only

Minimum duct metal thickness/minimum reinforcement rating Maximum spacing between joints or intermediate reinforcement Duct

1200 mm centres, whichever is the smaller.

TABLE 2.3(H) RECTANGULAR DUCT TRANSVERSE JOINT TYPES AND RATINGS (J)

0.8 J1 TJ-1 drive slip (DC)

minimum metal thickness 0.8 mm Use duct sealant in corners Not recommended for pressures above 1000 Pa.

25 × 25 × 3 J4 TJ-2 angle reinforced drive

slip (ARDC) minimum metal thickness 0.8 mm Use duct sealant in corners Use fasteners or spot weld at

150 mm centres to attach reinforcement to duct wall.

Not recommended for pressures above 1000 Pa.

May be used where a smooth external finish is required.

Use duct sealant, fasteners at

200 mm centres Not recommended for pressures above 1000 Pa.

150 mm centres to attach reinforcement to duct wall.

Not recommended for pressures above 1000 Pa.

(SDS) minimum metal thickness 0.8 mm Use fasteners at 300 mm centres and 50 mm from corners Use duct sealant in corners Not recommended for pressures above 1000 Pa.

(continued)

TABLE 2.3(H) (continued)

20 × 0.6 J2 TJ-6 standing seam (SS) Use

button punch or fastener at

200 mm centres and 50 mm from each corner Use duct sealant in corners.

750 Pa and 8 mm bolts for pressures above 750 Pa at

200 mm centres and 50 mm from each corner.

15 mm min width gasket between flanges Use bolts at

150 mm centres and at each corner Use 8 mm dia bolts for pressure up to 1000 Pa and 10 mm dia for pressure above 1000 Pa Angle dimensions to AS 3679.1.

welded flange (ARWF) All

15 mm flanges shall be fully welded All flanges 20 mm and above may be riveted, screwed, spot-welded or tack- welded at 100 mm centres Use fasteners or spot weld at

150 mm centres to attach reinforcement to duct wall.

25 × 0.6 duct J4 TJ-13 integrated machine

rolled flange (IMRF), machine rolled mating flanges at the end of duct Use 15 mm min width gasket Use special corners and corner bolts Use joining clips at 150 mm from each end and at 300 mm centres, complying with machine- manufactured EI values.

machine rolled flange (RIMRF), machine rolled mating flanges at end of duct Use 15 mm min width gasket Use special corners and corner bolts Use joining clips at 150 mm from corners and at 300 mm centres Use reinforcing flat bar as required to comply with the rating needed Comply with machine-manufactured EI values.

Refer to manufacturer’s data for higher ‘J’ ratings and EI values.

TABLE 2.3(I) RECTANGULAR DUCT INTERMEDIATE TRANSVERSE

REINFORCEMENT (ITR)

H× W×T ITR-3 channel or U section

cold rolled or folded channel section Galvanized or primed prior to attaching to duct.

Use fasteners or spot weld at

150 mm centres and at corners to attach reinforcement to duct wall.

H×W ×L× T ITR-4 top hat section cold

rolled or folded top hat section Galvanized or primed prior to attaching to duct.

Use fasteners or spot weld at

150 mm centres and at corners to attach reinforcement to duct wall.

TABLE 2.3(I) (continued)

H×W ×T ITR-1 angles hot rolled, cold

rolled or formed mild steel angles Galvanized or primed prior to attaching to duct Use fasteners or spot weld at each corners and at 150 mm centres to attach

reinforcement to duct walls.

DIMENSIONS IN MILLIMETRES

FIGURE 2.3(A) RECTANGULAR DUCT LONGITUDINAL SEAMS (LS)

NOTE: Number of seams and location varies with joint type, sheet stock and assembly plans.

FIGURE 2.3(B) SEAM LOCATIONS

DIMENSIONS IN MILLIMETRES

FIGURE 2.3(C) TIE RODS (t)FIGURE 2.3(D) RECTANGULAR DUCT REINFORCEMENT

NOTE: Unless otherwise specified, all duct sides of 300 mm, or greater, in width, shall be stiffened by cross breaking or beading Internally insulated duct may be excluded from this requirement.

DIMENSIONS IN MILLIMETRES

FIGURE 2.3(E) RECTANGULAR DUCT REINFORCEMENTCROSS BREAKING AND BEADING REQUIREMENTS

TABLE 2.3(J) RECTANGULAR ALUMINIUM DUCT, ADAPTED FROM 750 Pa

OR LOWER STEEL CONSTRUCTION TABLES

Duct metal thickness equivalent Galvanized steel, mm

Aluminium equiv., mm (see Note 1)

0.6 0.9

0.8 1.1

1.0 1.3

1.2 1.7

1.6 2.1

Transverse joint reinforcement rating comparison

Alum req for

equiv steel rating

40 × 3

50 × 5 or

40 × 10

NOTES:

1 Use aluminium sheet to AS 1734 Grade A-3003-H14.

2 Use aluminium extruded section to AS 1866 alloy 6063.

TABLE 2.3(K) RECTANGULAR ALUMINIUM DUCT FOR SHOP FABRICATION USING

ALUMINIUM ANGLES AS TRANSVERSE JOINTS AND

INTERMEDIATE REINFORCEMENT

Duct longest side

mm

Aluminium sheet thickness mm

Transverse angle joints size mm

Spacing between reinforcement mm

Intermediate reinforcement size mm

1 Alternative aluminium extrusions may be used as intermediate reinforcement in lieu of angles provided that the stiffening capabilities of such sections are equal or superior to those of the angles specified in the table.

2 For longitudinal seams refer to Figure 2.3(A).

3 For cross breaking or beading refer to Figure 2.3(E).

4 For methods of construction refer to Clauses 2.4 and 2.5.

5 If using aluminium hangers and supports, increase the cross-section size by 2.5 times that required for galvanized steel duct.

TABLE 2.3(L) RECTANGULAR STAINLESS STEEL DUCT FOR SHOP FABRICATION SUITABLE FOR POSITIVE PRESSURES

Spacing between intermediate for pressure

Reinforcing stainless steel angle size

TJ-1 TJ-1 TJ-1 TJ-9 TJ-9 TJ-9

0.6 0.8 1.0

1 Cross breaking or beading shall be as for galvanized steel duct, refer Figure 2.3(E).

2 Stainless steel sheet shall be to AS 1449 alloy 304 L or as otherwise specified, provided it is suitable for lock forming.

3 Longitudinal seams shall be as for galvanized steel duct, refer Figure 2.3(A).

4 Reinforcement shall be attached to duct wall by spot weld or fasteners.

5 Fasteners shall be stainless steel pop rivets or screws.

6 Use hangers as for galvanized steel duct Use stainless steel hangers if required; galvanized steel hangers may be used if permitted by designers.

1 Fire dampers to be installed in accordance with AS 1682, Part 2.

2 Volume dampers should only be installed in order to balance the system.

3 Volume dampers or splitter dampers should be used to achieve correct system balance.

FIGURE 2.3(F) TYPICAL SUPPLY OR RETURN AIR DUCT LAYOUT

1 Volume control should be by branch dampers.

2 If a splitter is shown in the design its length should be 1.5 W or 1.5D3.

DIMENSIONS IN MILLIMETRES

FIGURE 2.3(G) PARALLEL BRANCHES — EXAMPLE DETAIL

1 Splitter damper to be fabricated from 1.2 mm galvanized iron.

2 Butt hinges pop riveted or spot welded to ductwork.

3 Volume dampers use 1.6 mm galvanized iron or proprietary aluminium damper, max blade length

FIGURE 2.3(I) VANE CHART