Ductwork Systems

NPQSM3-10 Ductwork Systems

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National Productivity and Quality Specifications (NPQS)

M3-10 Ductwork Systems


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CONTENTS Page

SECTION M3-10, DUCTWORK SYSTEMS 3

1. PRELIMINARIES AND GENERAL CLAUSES 3 1.1 Scope 3 1.2 Related Sections & Interfaces 3 1.3 Standards and Codes 3 1.4 Trade preliminaries 4

2. PERFORMANCE CRITERIA AND REQUIREMENTS 4

3. MATERIALS 4

4. WORKMANSHIP 4 4.1 General 4 4.2 Fabrication 5 4.3 Installation 9

5. VERIFICATIONS AND SUBMISSIONS 18

6. ASSOCIATED WORKS 18

PROJECT SPECIFIC DATA SHEETS (PSD) 19

1. PSD M3-10-1, DUCTWORK 19

2. PSD M3-10-2, AIR FILTERS 23

3. PSD M3-10-3, ATTENUATORS 25

4. PSD M3-10-4, FIRE DAMPERS 27

5. PSD M3-10-5, SMOKE DAMPERS 28


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MECHANICAL VENTILATION & AIR CONDITIONING SPECIFICATION, WORK PACKAGE M3, AIR DISTRIBUTION SYSTEMS & EQUIPMENT

SECTION M3-10, DUCTWORK SYSTEMS

1. PRELIMINARIES AND GENERAL CLAUSES

Read this specification with Preliminaries and all other contract documents.

1.1 Scope

Provide air distribution ductwork system(s) as required by the building description clauses, as detailed on the drawings and in Project Specific Data sheets PSD M3-10-1, PSD M3-10-2, PSD M3-10-3, PSD M3-10-4 and PSD M3-10-5.

1.2 Related Sections & Interfaces

Read this work section in conjunction with the relevant requirements of the other work sections as follows:

M3-20, Air Systems Insulation

M3-30, Air Handling Units

M3-40, Fan Coil Units

M3-50, Air Terminal Devices

M3-60, Fans & Fan Units

M3-80, Related Electrical Works

M1-20-1 Pipework, Valves & Fittings

1.3 Standards and Codes

1.3.1 General

Unless otherwise agreed by the SO/Engineer, ensure all of the Works comply with the relevant requirements of the Standards and Codes listed below or referenced in the body of the Specification. Alternative Standards and Codes may be proposed for approval by the SO/Engineer, provided it can be demonstrated that the alternative Standards and Codes comply with the requirements of the standards specified . All Standards and Codes quoted are current version, unless specific year references are noted.

Singapore Code of Practice SS CP13

HVCA (UK) DW/144 & DW/143

SMACNA Ductwork Specifications

Code of Practice for Fire Precautions in Buildings

Spring Singapore.


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1.3.2 Local Authorities

Ensure that the works comply with the relevant authority regulations and directions.

Where the terms “testing authority”, “approving authority”, “local authority or “local authorities” are used in this section, the bodies referred to are as follows:-

Public Utilities Board

Fire Safety & Shelter Department

SP Services Ltd

Power Grid Ltd

City Gas Pte Ltd

Info-comm Development Authority (IDA)

Energy Market Authority

National Environment Agency

1.4 Trade preliminaries

1.4.1 Operation and Maintenance Manual

Provide full information for inclusion in the O & M Manual.

1.4.2 Contractor Designs & Submissions

Where design verifications or design works & submissions are required to be carried out, defined either in this specification or in Project Specific Data, employ a suitably qualified QP to carry out and endorse those designs.

2. PERFORMANCE CRITERIA AND REQUIREMENTS

Ensure systems provide airtight distribution as prescribed by reference documents.

3. MATERIALS

Use materials as required within the standards and codes listed.

4. WORKMANSHIP

4.1 General

Use the Heating and Ventilating Contractors' Association (HVCA), 'Specification for sheet metal ductwork - low, medium and high pressure/velocity systems - DW/144' (or SMACNA equivalent) and the requirements of this Specification for materials, construction and identification of ductwork.

Where Table numbers are quoted for metal ductwork, these refer to HVCA DW/144.


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4.1.1 Test Holes

Provide test holes in all main and branch ducts and adjacent to all duct-mounted temperature and humidity sensors, and at main supply air ducts close to outlets from equipment.

Provide test holes at 150mm or less centres across the longer side of the duct to consist of factory fabricated tap screw brazed into a 40mm wide bar and riveted to the duct. Ensure the test hole assembly provides an airtight and non-corrosive arrangement.

Agree at site the locations of all test holes, at points of minimum turbulence, and mark and record. Ensure the number provides the total coverage required for duct size and number of traverses to ASHRAE recommendations.

Where test holes are provided to thermally insulated ducts protect the insulation with expanded metal 0.5m upstream and 1.5m downstream of the penetration.

Ensure test holes are accessible for airflow measurement, system balancing, testing and commissioning activities.

4.1.2 Lightweight Ducting

( Not in use. )

4.1.3 Aluminum/Phenolic-Foam Board Ductwork

( Not in use. )

4.2 Fabrication

4.2.1 Ductwork Construction

All references to tables are those of HVCA DW/144.

Ensure sheet metal for fabrication is new and free from blisters, pits and imperfections in coating. Ensure galvanising is to BS EN ISO 1461: 1999. Clean, prepare and paint with zinc-rich paint to BS 4652 at works all raw edges and areas of metal where galvanizing has been destroyed. Repair transit damage at site prior to erection. Repair all cut edges with zinc-rich paint to BS 4652.

Use the fewest number of joints possible.

Duct sizes are clear internal required airway dimensions. Make allowance for any linings and their coverings. No obstructions or rough surfaces are permitted within any ductwork.

Where internal linings are required, ensure that the lining is held in continuous contact with duct surfaces under all operating conditions by fixings to prevent detachment and fibre migration.

Use cross-breaking and beading on low velocity ductwork only, but not where rigid external insulation is to be applied.

Use factory-made take-offs of conical, bellmouth, or shoe type. Do not use duct size square take-offs from main ducts.

Use fabricated fittings for change direction, size, shape and connections.


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Do not form holes in main ducts for branches greater than the branch size.

Do not use perforated rivets in the manufacture or erection of ductwork. The use of locations only where alternative methods are not possible. Submit a record of these locations.

Construct larger ducts to the Sheet Metal and Air Conditioning Contractors' National Association (of North America) (SMACNA) publications 'HVAC Duct Construction Standards - Metal and Flexible -2nd Edition 1995' and 'Round and Rectangular Industrial Duct Construction Standards, 2nd Edition 1995', with Addendum No.1 1997.

Provide adequate local stiffening at instrument and controls penetrations and connections to provide rigid mountings.

Provide and submit a certificate to confirm that all ductwork constructions comply with the relevant HVCA DW/144 tabulated gauges.

Where site dimensions cannot be obtained in advance of preparation of shop drawings, make provision to accommodate any discrepancies between the drawings and site requirements. Show provisions for dismantling, by means of bolted, gasketted flanged joints, on the shop drawings.

Construct rectangular ducts using longitudinal seams with sealant applied internal to the joint seam itself.

Use sheet steel thicknesses to Tables 2 to 4 of DW/144 dependent on pressure classification.

Make circular ducts of spirally wound or straight seam construction. Use sheet thicknesses to Tables 7 & 8 of DW/144. Make fittings of spirally wound construction thicknesses.

Make flat oval ducts of spirally wound construction with duct and fittings sheet thicknesses to Table 11 of DW/144.

Incorporate stiffening provisions.

Incorporate sealant in and tightly form all seams. Do not use edge sealants.

Use sealant between sheet and flange section in cross joint assemblies. Ensure the sealant does not serve as the duct skin.

Provide flanged joints at all plant and equipment items, at structural walls and floor slabs and elsewhere where required for disconnection purposes.

Ensure joint corners and junction details are mutually compatible with the longitudinal seam used.

Assemble tie rod stiffeners for rectangular and flat oval ducts with internal and external nut, metal and compressible washer.

Fit double skin turning vanes in short radius ('hard') bends over 300mm deep and in all change-direction fittings, except in kitchen exhaust ventilation systems.

Do not exceed a slope of 15 degrees for change shape tapers.

Make all segmented bends for circular ducts in five sections.

Make circular radius pressed bends of one diameter throat radius.

Make change shape tapers for circular ducts 15 degree concentric.


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Joint sheet metal casings to air handling equipment components to suit the maximum operating pressure and permitted air leakage.

Do not use self-adhesive sealing tapes. Use only glass fibre reinforced tape fixed with spray-applied adhesive at site.

Terminate air terminal branch ducts clear of final connection flanges.

Provide ductwork connections to building openings, external louvres, grilles etc. with compatible flanges for airtight fixing.

Ensure supports for internal ductwork generally comply with HVCA DW/ 144-6, except that attachment of horizontal ductwork from duct flanges will not be permitted.

Bolt frames and blades fabricated from galvanized mild steel or aluminium sections and sheet together. If welding methods of assembly are used reinstate the galvanizing immediately on completion of welding.

Assemble frames and blades fabricated from aluminium alloy extruded sections by inert gas shielded arc-welding, or bolt or rivet together.

Fit galvanized wire bird screens 10mm mesh size to the inner face of louvres which extend over the full face of the louvre and are removable for cleaning.

4.2.2 Ductwork Cleanliness

Ensure ductwork delivered to site meets 'Intermediate Level' of HVCA DW/TM2.

Make provisions for cleaning 'in use' generally to HVCA TR/17.

On completion clean ductwork by blowing-out using system fans, after pre-cleaning by brushing or other means without detrimental effect to finished areas and complete before terminal units are finally connected.

Cover open end of all ductwork at the end of each workday to prevent ingress and settlement of dust inside the ductwork. Do not use any type of waste material for this purpose.

Clean ductwork to a higher standard in special areas intended to house sensitive equipment or furnishings.

4.2.3 Materials

Use corrosion resistant materials, including fixings, or treat to resist corrosion.

4.2.4 Control Dampers

Construct dampers to HVCA DW/144.

Make volume control dampers up to 300mm wide single blade type.

Make volume control dampers greater than 300mm wide as opposed blade type.

Finish all dampers to be used with air terminals in matt black paint.

Construct non-return (self-closing) dampers to ensure positive shut-off and quiet closure.

Make splitter dampers single blade type of 1.6mm thickness galvanized mild steel sheet with full width heavy brass hinges and componentry of non-ferrous materials. Ensure blade dimensions give clearance to prevent noise generation.


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Provide minimum 8mm diameter threaded galvanized adjusting rod with indicator to show adjusted position.

Ensure that automatic (motorised) dampers in the closed position do not allow leakage of more than 2% of local design air volume.

4.2.5 Fire and Smoke Dampers

Arrange fire dampers acting as dual fire and balancing dampers to enable variable blade setting as determined by air balance.

Provide smoke dampers in any ductwork to prevent transfer of smoke into a designated escape route.

Ensure fire dampers and smoke dampers are rated for the particular fire compartmentation, meet the requirements of FSSD and have the approval of the Local Authority.

Ensure FSSD approves the method of fixing

Provide fire dampers to SS 333 and install to SS CP 13.

Ensure fire dampers of the cased folding-blade spring-loaded type have a replaceable and re-settable release mechanism. In the open position ensure the blades do not restrict the airstream.

Provide dampers for horizontal mounting with stainless steel closure springs and positive blade locking devices.

Provide dampers in circular or flat oval ductwork with integral spigots to suit the containing ductwork.

Provide plate (single) blade type fire dampers to close against full perimeter stops upon activation by a temperature-sensitive device. Ensure the casing and blade are of appropriate thickness for the fire rating. Provide means for blade and release device reset.

Ensure fire or smoke damper release mechanisms are to BS EN 54-7.

Provide purpose-made frames for building-in to structure.

Provide access openings adjacent to fire and smoke dampers for inspection. Ensure size is sufficient to permit resetting of release mechanism and blades by one person; make access provision in accordance with SS CP13.

Also provide/ensure access to fire damper and smoke damper assemblies through builders work elements.

4.2.6 Fire-Rated Ductwork

Construct the ductwork to meet the requirements of method 3 of BS 5588-9 and BS 476-24 for stability, insulation, integrity and minimum cross sectional area of 75% at design conditions and in accordance with the requirements in SS CP13. Insulate fire rated ductwork where necessary to achieve these requirements.

4.2.7 Thermal Insulation

Refer to M3-20, Ductwork Thermal Insulation.

Make provisions for the fixing of thermal insulation material.


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Apply rigid slab to rectangular ducts with top and bottom members overlapping side slabs, all secured with corrosion-resistant serrated steel bands with locking devices applied to ensure insulation material is not compressed.

For ducts and equipment items with side dimensions in excess of 1000mm attach insulation with hangers with spring clip washers at 600mm square pitch for fixing.

Insulate exposed circular and flat oval ductwork with lamella mattress faced with glass fibre reinforced aluminium foil of Class "O" rating suitably secured, and facings overlaps securely fixed.

Insulate concealed rectangular, circular and flat oval ductwork with non-combustible, resin bonded fibrous mattress fixed to 150mm wide bands of suitable adhesive at 300mm centres with 1.6mm bright soft steel wire spirally wound at 450mm pitch.

Complete insulated ductwork with a full retaining, non-penetrating, wrap of zinc-coated hexagonal steel wire netting with joints laced with 1.6mm bright soft steel wire.

4.2.8 Insulation to Ductwork Access Doors

Insulate proprietary and custom made access doors, covers and panels proposed for use at least to the same standard as of the enclosing ductwork.

Insulate custom-made access doors as for enclosing ductwork with insulation contained within a BS 1474 channel section frame with mitred corners and aluminium external and internal facing sheets incorporated, bedded in mastic. Provide facing panels of 0.7mm minimum thickness aluminium sheet.

4.2.9 Insulation at Ductwork Supports

Line ductwork bearer supports with incompressible non-combustible insulating material to the same thickness as the specified insulation.

Leave sufficient clearance at drop rod fixings to bearer supports of suspended ductwork for the application of insulation, vapour barrier and finish covering to the duct sides.

4.3 Installation

4.3.1 General

Establish and maintain site storage areas to comply with HVCA DW/TM2.

Provide all necessary ductwork, control, isolating, fire, smoke and balancing dampers, grilles and diffusers to form complete air distribution systems.

Install ductwork free from sway, drumming and movement. Ensure ductwork is true-to-size and accurately aligned.

Securely support and install ductwork parallel to building construction and in true horizontal and vertical planes.

As far as practicable, align longitudinal seams where permanently visible after installation.

Support duct branches and equipment items locally to prevent distortion.


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Provide flexible connections between ductwork and fans and other equipment items.

Provide and maintain access to ductwork system components which require inspection, cleaning, or adjustment.

At every point of duct penetration of the building envelope, provide a sealed louvre, weather cowl or protective flashing and full closure plate to prevent ingress of water.

Paint ductwork immediately behind and connected to an intake or exhaust louvre, on internal and external surfaces with epoxy resin or bitumastic paint for a length from the louvre equal to the louvre height, or to the nearest equipment item, whichever is the lesser. Slope the bottom side of the ductwork connection downwards towards the louvre and arrange drainage.

Slope fume or vapour-laden ducts down to a drainage point. Where ducts are metal, do not “cross-break” the bottom panel.

Where personnel entry into the duct is necessary, provide floor plates connected to stiffeners to accept the loading, with suitable additional local supports.

Extend lubrication points, not easily reached, to an accessible position.

4.3.2 Hangers and Supports

Provide hangers and supports fabricated from hot-dipped galvanized steel plate, angle and channel sections for indoor applications.

Ensure support spacing and loadings include all ductwork system components which cannot be provided with individual supports.

Ensure the size, strength and materials used for external ductwork supports are suitable for the ductwork, system components, insulation, cladding and prevailing external conditions. Provide cross- bracing between adjacent supports where necessary to resist wind loading.

Submit full details of all hangers and supports.

Support horizontal ducts at spacings to Table 15 of DW/144, and additionally at branches and equipment items. Support vertical ducts off floor slabs and by purpose-made brackets fixed to the structure where spacing exceeds 4m.

Do not vary fixings particularly specified for supports.

Paint duct hangers wherever exposed in humid air or to view.

Install hangers for ducts to be thermally insulated to provide clearance for the insulation and any vapour barrier or other covering to be applied and finished. Line horizontal bearers with low compression insulating material.

Ensure that the insert and vapour barrier are not compressed or damaged by the load imposed. Extend inserts an adequate distance each side of the support to allow the insulation to be abutted and the vapour barrier to be sealed to the insert.


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4.3.3 Access Openings

Provide access openings, arranged and sized to permit full access necessary for maintenance. Provide inspection covers to permit associated equipment item to be viewed.

Provide rigidly framed access openings and inspection covers with gasketted airtight covers designed for easy removal and accurate relocation and fixing.

Ensure access doors are of same fire rating as parent ductwork.

Use the minimum number of quick-release fastening devices compatible with the loading.

Do not use self-tapping screws.

Subject to the duct size, provide access and inspection openings as shown below.

Provide access openings for inspection of fire dampers in accordance with SS CP13.

Ensure access to fire and smoke dampers provides for full manual resetting of the shutter.

Provide access covers with retention devices.

Make personnel access doors hinged, a minimum of 600mm wide and matching the duct depth less 50mm, and fit with restrainers.

Provide such hinged access doors with double-sided operating handles for safe exit.

Fit proprietary insulated double-skin hinged access doors in all insulated ducts.

Locations of access points required are summarised below:

Item Access Opening Inspection Cover

Centrifugal fan √ (inlet & outlet)

Axial fan √ (inlet & outlet)

Fire / smoke damper √ (full width access)

Volume control damper √ (400mm+ wide) √ (up to 400mm wide)

Automatic control damper √ (400mm+ wide) √ (up to 400mm wide)

Filter bank √

Cooling coil √ (upstream) √ (downstream)

Heating coil √ (upstream) √ (downstream)

Humidifier √ (at units)

Cleaning point √

Turning vanes √ (upstream)

Attenuators √ (upstream)

Riser bases √

Control Dampers √


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Non-return dampers √

Fit balancing dampers in each branch from a main or sub-main duct, and elsewhere as required to satisfactorily commission the system. Maintain the required distance from the branch-piece.

Ensure automatic damper actuators have:

a. Sufficient torque to open and close against the maximum out-of-balance pressure across the damper.

b. Position indicators, unless fitted to terminal units.

c. Manual override facility, unless fitted to terminal units.

d. A linear stroke/control signal characteristic.

4.3.4 Control Dampers

Install dampers in permanently accessible positions.

4.3.5 Fire Dampers

Provide fire dampers in any ductwork passing through each and every fire compartment wall.

Install fire dampers in accordance with SS CP13, FSSD: requirements and the recommendations of the product manufacturer.

Build-in purpose-made installation frames with expansion allowance to formed openings in fire compartment walls, floors or other openings designated. Mask the joint line with firmly fixed metal plating all round to prevent penetration of any gap by flames or gases.

Restrict openings sizes to require the minimum of incombustible infill material, to provide a homogeneous construction and maintain the fire resisting integrity of the structure.

Do not support fire dampers and frames by means of adjacent ductwork.

Always set fire dampers and frames parallel to the plane of the wall or floor.

Where dampers cannot be positioned in the thickness of a fire barrier, enclose the ductwork or casing between the barrier and the furthest side of the damper case with fire resistant material of equal fire rating to that of the fire barrier. Adequately support and fix to the barrier, in accordance with the manufacturers recommendations, to meet recognised and approved fire test methods.

Fix dampers for flexible cavity barriers as the manufacturers' recommendations for the application. Provide suitable frames and brackets to ensure compliance with fire test methods.

Set blade release mechanisms normally retaining fire dampers in the open position to operate at 74°C ±2°C.

4.3.6 Fire-Rated Ductwork

Wherever possible install fire-rated ductwork at the highest level, above all other services. Where this cannot be achieved protect all services installed directly


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above the fire-rated ductwork with material of similar fire-rating to the fire-rated ductwork.

Obtain all necessary supports, cover and aligning strips and other accessories required for the complete installation of the fire-rated ductwork system from the same manufacturer as that for the fire-rated system.

Ensure all fire rated ductwork is a fully tested and certified proprietary product and has the approval of FSSD.

Ensure fire rated ductwork can achieve the requirements of protection method 3 described in BS 5588-9, and comply with the performance criteria in BS 476-24.

Ensure that the fire resistance of the ductwork, when tested from either side (external and internal), is not less than the fire resistance of the construction elements in the area through which it passes and in any case is not less than 2 hours.

Ensure the ductwork support system satisfies the requirements of BS 476-24.

Provide access panels for components as described for ductwork. Provide panels suitable for frequent use without compromising the fire rating and leakage performance of the ductwork.

Submit PE certification for all fire-rated ductwork constructed and installed at site.

4.3.7 Ductwork Fire Cladding

Where specified or shown on Drawings, clad ducting with ‘Vicuclad’ board or equivalent applied strictly in accordance with the manufacturers’ printed and published instructions.

4.3.8 Flexible Connections

Provide flexible joints of 50mm minimum and 250mm maximum lengths without intrusion into the airway under any condition. Support ductwork and align to prevent undue stress in the flexible joint.

Ensure flexible joints are fire rated and tested in accordance with BS 476-20.

Provide flexible connections to SS CP13.

Do not use flexible connections at staircase pressurisation systems nor smoke-stop lobby ventilation fans. At these positions provide flanged joints.

Tightly clamp flexible joint connections to prevent air leakage. Ensure that the material remains flexible and without strain or distortion. Secure material to plain circular spigots by use of clipbands with adjustable-screw toggle fitting. Secure jointing to flanged spigots by a drilled backing flat iron flange bolted through properly formed holes in the flexible material to the fixed flange.

Ensure that the method of connection permits removal and replacement without dismantling of ductwork.

4.3.9 Bendable and Flexible Ducts

Ensure flexible ducting complies with air-tightness requirements for rigid ducts within the same system and is suitable for the system pressure.


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Provide non-combustible materials Class O rating, non-rigid ducts of bendable aluminium, flexible metal or flexible fabric construction.

Provide minimum length of 1500mm to plug-in diffusers to give repositioning facility.

Restrict the maximum length of each non-rigid section to 4000mm, as SS CP 13.

Form changes in direction in long radius. Restrict bends where necessary to two per length with 90° minimum included angle. Ensure minimum throat radius is two diameters.

Provide adequate support to prevent sagging. Kinked or flattened non-rigid ductwork will be rejected.

Form any test holes required in rigid ductwork adjacent to flexible lengths.

4.3.10 Low Velocity Plastics Ductwork

( Not in use. )

4.3.11 Noise Attenuators

Select and provide sound attenuators to meet the specified space noise criteria whether shown on the relevant drawings or not. Ensure sound attenuators sizes are not less than the cross-sectional area of the enclosing ductwork. Where sound attenuators are larger than the duct dimensions provide the appropriate transformation pieces.

Ensure noise attenuators are designed, constructed and tested by a specialist manufacturer and match the adjacent assemblies. Ensure the airways are free from projections into the airstream.

Ensure performance figures including insertion loss are derived from tests carried out in accordance with BS 4718 Methods of test for silencers for air distribution systems. Achieve performance under system operating conditions. Include for the use of the vapour barrier in Attenuator dynamic insertion loss data provided.`

Construct attenuator casings from galvanized steel sheet. Make joints longitudinal, lockformed and mastic sealed during construction. Weld end flanges to the casings, and supply with slotted bolt holes or other fixing details as necessary.

Ensure casing thickness and flange construction are in accordance with HVCA Specification DW/144 (or SMACNA equivalent), but with minimum thickness 0.8mm.

Use noise absorbent materials which are of limited combustibility, when tested to BS 476-6 have a fire propagation index (I) not exceeding 12 with not more than 6 deriving from the initial period of the test (i-1), and class 1 spread of flame to BS 476-7.

Ensure materials are rot-proof, non-hygroscopic, will not support pests nor fungi, be free of objectionable odour at installed working condition, do not constitute a health hazard at any time, and will not promote corrosion under normal site conditions nor structurally deteriorate resulting from inadvertent contact with water.


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Select materials to withstand an air passage velocity of at least 25m/s without surface erosion or other material migration. Pack loose or fibrous materials under not less than 5% compression to eliminate voids due to settling.

Ensure the vapour barrier material is resistant to chemicals as required for the application.

Use vapour barriers in aggressive atmospheres not exceeding 0.07mm thickness and install in a non-taut state. Ensure the material achieves Class I to BS 476-7, and does not emit toxic or hazardous fumes if ignited.

Clearly mark the direction of airflow on the attenuator outer casing.

Make rectangular attenuators splitter elements round-nosed and to stand vertically and be a close fitting within the casing. Design L-section and T-section splitter attenuators for smooth airflow to minimize self-generated noise. Fit splitters in bend attenuators perpendicular to the plane of the bend.

Make splitter elements easily removable for cleaning. Fit the necessary access panels with effective airtight seals which retain their performance after repeated use.

4.3.12 Air Filtration

Provide air filters with specified efficiency to ASHRAE 52.2 – 1999.

Ensure filter banks are fully accessible for inspection, filter replacement and general maintenance.

Provide a manometer indicating differential pressure mounted externally adjacent to each filter bank.

House filter banks in a metal frame. Ensure the frame cannot distort in use and is treated to prevent corrosion.

Ensure filter elements are rigidly and securely held in the frames and are without distortion. Ensure plastics frames are suitable for the conditions in which they operate and are approved by the local Fire Authority.

Provide filter media and frames to comply with SS CP13 and to meet the Local Authority and the appropriate Fire Authority's fire and smoke requirements

Ensure filter panels and bags can sustain at least two times the initial pressure drop without distress.

Provide filter bank frames of same supply as the cells.

4.3.13 Panel Filters

Form filter banks of a number of individual elements of uniform size, retained in a steel or aluminium framework by suitable spring clips. Weld or rivet joints in the frame sections. Bolt individual frames together to form the complete filter bank and to prevent by-pass of air.

4.3.14 Bag Type Filters

Form bags from woven glass fibre cloths in multiple layers and grades, properly stitched and sealed or from synthetic (non-fibrous) material.


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Bond the opening of each bag to a rigid sub-frame to fit into the filter bank framework.

Provide each element with an effective perimeter gasket to prevent by-pass of air.

Ensure bags remain fully inflated to expose maximum filter surface at air velocities related to 30% of system design duty.

4.3.15 Electronic Air Cleaners (EAC)

Locate EACs designed for operation with a 240V 1phase 50hZ with ground electrical supply in return ducts for areas as shown on Drawings or designated bars, discos and lounges.

Select unit for required airflow and efficiency 95% for 0.01 micro-metre to ASHRAE Standard 52-76.

Ensure units offered are UL listed and/or CSA certified and approved for use in Singapore by the relevant Authorities.

Ensure the unit is based on two-stage electrostatic precipitation stage1-ioniser section, stage 2-collector section.

Provide a unit having galvanized mild steel cabinet, fan and motor with sealed-for-life ball-bearings, heavy duty commercial electronic cells, solid-state power supply and protective screens and pre-filters.

Ensure solid-state supply provides high voltage (DC) to the self-regulating ionizer and collector sections.

Provide a safety interlock switch to automatically interrupt the power supply when the access door or grille is opened.

Provide a status lamp to indicate correct power operation.

Locate indicator lamps, access doors and grilles at front of unit for ease of access.

Ensure the ionizer and collector sections have the correct ratio of ionising wires and collector plates.

Ensure that intake and discharge grilles, pre-filter and electronic cells (with handle) are removable for cleaning without the use of tools, and the power supply can be disconnected without removing the electronic cells.

Arrange the EAC to be monitored remotely by a Solid State Performance Indicator (SSPI) and to have LEDs to display On/Off status, Wash and Check indication. Provide suitable voltage-free contacts for connection to BMS

Interlock the EAC with the AHU operation.

Provide coarse filters to protect the EAC from larger particulate matter.

Give indication of auto-wash in progress and electronic cell servicing required via indicating lamps.

4.3.16 Internal Insulation

Fix lining materials to internal surfaces of airways in locations of thicknesses listed, to leave the indicated clear airway dimensions after application. Seal all


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joints and cut edges to prevent erosion, and to present a smooth face to the airstream.

Retain linings in position with expanded or perforated metal sheets secured with mechanical fixings. Firmly attach fixings to airway walls. ‘Return’ metal lining sheets at the end of each airway section.

Set out fixing stud spacing at (top) 150mm centres, vertical sides 250mm and bottom 300mm.

The SO/Engineer will inspect internally lined duct sections before installation.

Damaged factory or site-applied linings will be rejected at any stage of delivery, storage or erection of systems.

Use adhesives that are non-combustible after application.

Ensure lining materials used are incombustible, rot-proof and non-hygroscopic, as approved by the relevant local Authority.

Ensure the complete assembly of materials is non-combustible as defined in BS 476-4. If combustible, ensure linings have an Index of Performance (I) not exceeding 12, of which not more than 6 shall derive from the initial period (i) of the test to BS 476-6.

Face the lining material with a thin, tough and smooth acoustically transparent membrane presented to the air stream and held in position with a securely fixed perforated metal sheet. Select the facing to prevent surface erosion or other material migration at an air passage velocity of at least 25m/s.

Ensure the installed duct lining has the following minimum sound absorption coefficients when measured in accordance with BS EN 20354.

Thickness (mm) Octave Band Centre Frequency (Hz)

125 250 500 1k 2k 4k

15 0.1 0.25 0.45 0.65 0.9 0.85

25 0.1 0.35 0.55 0.85 0.95 0.95

50 0.35 0.5 0.85 0.95 0.95 0.95

4.3.17 External Louvres

Install framed louvre bladed sections at air intake and discharge openings with the required net effective areas as shown on the drawings.

Make louvres weatherproof with horizontal angled blades to prevent entry of driving rain.

Refer to architectural specifications for louvre fabrication and installation.

Weather seal and acoustically seal frames into openings with a suitable mastic. Arrange flanges to fully mask the opening.

4.3.18 Identification of Ductwork

Identify ductwork to the recommendations of DW 144 Appendix B.


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Provide explanatory charts and damper schedules.

Permanently affix symbols to ducts by use of painted, stencilled letters and figures or self-adhesive plastics applied to a smooth clean surface, or by use of engraved plastic or metal labels riveted to equipment items.

Set symbols at 6m intervals on main ducts and within 3m of the main on each branch. Fix symbols in positions to be easily read from operators' level.

Identify special ductwork by particular alphanumeric or colour codes.

Provide fire rated ductwork with additional words "FIRE DUCT" permanently marked in red at 4m intervals with letters 50mm -0/ + 5mm in height.

5. VERIFICATIONS AND SUBMISSIONS

Test systems to guarantee operation at a specified leakage rate, as required within Appendix B of HVCA Specification DW/144, together with 'Method of Testing - DW/143' (or SMACNA equivalent).

6. ASSOCIATED WORKS

Provide details of builders’ work requirements for plinths, bases and openings in structure for equipment, ducts and fire/smoke dampers and making-good.

Arrange electrical connections for airflow switches, and sensors generally, installed in ductwork. Refer to M3-80, Related Electrical Works.

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MECHANICAL VENTILATION & AIR CONDITIONING SPECIFICATION, WORK PACKAGE M3, AIR DISTRIBUTION SYSTEMS & EQUIPMENT

PROJECT SPECIFIC DATA SHEETS (PSD)

1. PSD M3-10-1, DUCTWORK

Job Title:

Purpose of Issue: (Not Used – Please Refer To Drawings)

General Data

Unit Reference

Quantity

Location

System

Type

Speed Control

Ductwork Systems Required Required Required Required

Specification Type Reference Type DW1 Type DW2 Type DW3 Type DW4

Duct Construction Standard DW144 DW144 DW144

Duct Test Standard DW143 DW143 DW143

Ductwork Construction Class A – Low Pressure B – Medium Pressure C – High Pressure Special

Duct Profiles Rectangular/Circular Rectangular/Circular Rectangular/Circular

Duct Positive Pressure Rating – Pa 500 1000 2000

Duct Negative Pressure Rating – Pa 500 750 750

Duct Material Hot Dip GSS Hot Dip GSS Hot Dip GSS

External Finish Natural Natural Natural

Internal Finish Natural Natural Natural

Maximum Air Temperature - °C

Location Internal

Duct Cleanliness Standard – DWTM2 Intermediate Intermediate Intermediate

Access Panels For Inspection DW144 DW144 DW144

Access Panels For Cleaning – HVCA TR/17 TR/17 TR/17

Ductwork Systems Offered Offered Offered Offered

Specification Type Reference

Duct Construction Standard

Duct Test Standard

Ductwork Construction Class

Duct Profiles

Duct Positive Pressure Rating – Pa

Duct Negative Pressure Rating – Pa

Duct Material

External Finish

Internal Finish


Location

Duct Cleanliness Standard – DWTM2

Access Panels For Inspection

Access Panels For Cleaning – HVCA

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Performance Data Required Offere

d Require

d Offere

d Require

d Offere

d Require

d Offere

d

Ductwork

System

Specification Reference

Location

Design Maximum Velocity – m/s

Max System Ext Static Pressure – Pa

Max System Differential Pressure

Extent of Pressure Testing - %

Max Test Pressure

Duct Cleanliness Standard @ Handover

Surface Deposit Limit (DTT) - µ m

System


Location





Max Test Pressure



System


Location





Max Test Pressure



Ductwork Plenums Required Offered Require

d Offered

Required

Offered Require

d Offere

d

Specification Type Reference Type DWP1 Type DWP2 Type DWP3 Type DWP4

Plenum Type Air Terminal Octopus Box External Louvre Special



Ductwork Construction Class A – Low Pressure A – Low Pressure A – Low Pressure Special

Ductwork Leakage Class A A A

Duct Profiles Rectangular/Circular Rectangular/Circular Rectangular/Circular

Duct Positive Pressure Rating – Pa 500 500 500

Duct Positive Negative Rating – Pa 500 500 500

Duct Material Hot Dip GSS Hot Dip GSS Hot Dip GSS

External Finish Natural Natural Natural

Internal Finish Natural Natural Natural

Duct Cleanliness Standard – DWTM2

Access Panels Inspection/Cleaning


Design Operating Pressure – Pa

Max System Differential Pressure – Pa

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Test Pressure – Pa

Flexible Ductwork Required Offered Require

d Offered

Required

Offered Require

d Offere

d

Specification Type Reference Type DWP1 Type DWP2 Type DWP3 Type DWP4

Application Air Terminal VAV Box Fan Movement Joint



Duct Type

Duct Material

Maximum Diameter – mm

Maximum Length – mm

Normal Operating Pressure – Pa

Maximum Differential Pressure – Pa


Maximum Air Velocity – m/s

Pressure Drop @ MAV – Pa/m

Duct Leakage Class – DW144

Factory Pre-Insulated

Connection Type

Minimum Throat Radius

Spread of Flame Rating

Acoustic Lining

Model Reference

Volume Control Dampers Required Offered Required Offere

d Require

d Offered

Required

Offered

Specification Type Reference Type VCD1 Type VCD2 Type VCD3

Damper Blade Configuration Single Multi

Damper Action Opposed

Casing Material

Blade Material

Blade Profile

Blade Linkage Type

Edge Seal Material

Connection Type

Model Reference

Required Offered Required Offered

Lockable Control Mechanism

Blade Position Indicator

Lined Ductwork Required Offered Required Offere

d Require

d Offered

Required

Offered

Specification Type Reference Type LDW1 Type LDW2

Lining Material

Lining Thickness – mm

Facing Material

Facing Thickness – mm

Lining Fixing method

Facing Fixing Method

Maximum Clear Airway Velocity – m/s

Spread of Flame Rating – Class

63 Hz

125 Hz

Minimum – 250 Hz

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Sound Absorption – 500 Hz

Coefficients – 1 kHz

2 kHz

4 kHz

8 kHz

Testing Required Offered Required Offered

Performance Type Tests Type Samples

Works Performance Tests

Site OEM Performance Tests

Additional Information

1. Documents Referred to:

HVCA DW144 Specification for Sheet metal Ductwork 1998 HVCA DW/TM2 Guide to Good Practice ‘Internal Cleanliness of New Ductwork Installations – 1991’ HVCA TR/17 Guide to Good Practice ‘Cleanliness of Ventilation Systems’ 1998

2. Ductwork Cleanliness standards required apply to the entire ductwork system including fittings and ancillary devices such as dampers, plenum boxes, etc.

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2. PSD M3-10-2, AIR FILTERS

Job Title:


General Data

Unit Reference

Quantity

Location

System

Type

Performance Data Required Offered Require

d Offered

Required

Offered

Required

Offered

Filter Application Pre Filter Final Filter

Filter Type Panel Bag

Filter Media

Filter Test Standard BSEN 779 BSEN 779

Filter Group & Class

Average Dust Arrestance - %

Average Dust Spot Efficiency - %

DOP Efficiency - %

Sodium Flame Efficiency - %

Air Flow Efficiency - %

Air Flow Rate - m³/s

Max Air Velocity – m/s

Filter Face Velocity – m/s

Filter Media Velocity – m/s

Clean Filter Pressure Drop – Pa

Dirty Filter Pressure Drop – Pa

Design Filter Pressure Drop – Pa

Dust Holding Capacity – g

Non-Combustibility Test

Combustibility Rating

Surface Spread of Flame Standard


Max Operating Temp & RH - °C/%

Max Operating Temp & RH - °C/%

Constructional Data

Frame Material

Frame Finish

Filter Module Fixing Method

Seal Type

Seal Material

Access Arrangement

Unit Reference

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Dimensional Data Required Offered Required Offere

d Require

d Offere

d Require

d Offered

Module Height – mm

Module Width – mm

Module Depth – mm

Overall Unit Height – mm

Overall Unit Width – mm

Overall Unit Depth – mm

Front Access – mm

Side Access – mm

Overall Weight – kg

Accessories Required Offered Required Offered

Differential Pressure Manometer

Independent Test Certificates

Spare Set of Filters

Testing Required Offered Samples Required Offered

Performance Type Tests � Type Samples




1. Independent test certificates shall be provided with the Tender for model types being offered.

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3. PSD M3-10-3, ATTENUATORS

Job Title:


General Data

Unit Reference

Quantity

Location

System

Type

Speed Control


d Offer

ed Require

d Offere

d Require

d Offered

Air Flow Rate - m³/s

Air Velocity – m/s

Pressure Drop – Pa

Length – mm

Width or Diameter – mm

Height – mm

Weight – kg

63 Hz

125 Hz

Dynamic Insertion Loss – 500 Hz

dB – 1kHz

2 kHz

4 kHz

8 kHz

Construction Data

Casing Material

Casing Finish

Casing Sheet Thickness – mm

Splitter Casing Material

Splitter Casing Finish

Splitter Casing Sheet Thickness – mm

Sound Absorption Material

Splitter Face Pattern

Splitter Face Material

Air Leakage Class – DW 144

Connection Type



Round Nose Splitters Saturated Atmosphere Operation

Removable Splitters Special Finish

Encased Absorption Material

Waterproof Construction

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Testing Required Offered Samples Required Offered

Performance Type Tests � Type Samples



Type Performance Tests Required Offered Samples Required Offered

Insertion Loss Performance Tests Pressure Loss Performance Tests

Regenerated Noise Performance Tests


1. Type test data shall be provided to demonstrate that the equipment performs to the required standards. 2. Include the effects of regenerated noise on insertion loss performance.

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4. PSD M3-10-4, FIRE DAMPERS

Job Title:


General Data

Unit Reference

Quantity

Location

System

Type


d Offered

Required

Offered Require

d Offered

Fire Rating – hours

Max Face Velocity – m/s

Max Air Pressure Drop – Pa

Max Differential Press. (Closed) – Pa


Fusible Link Temperature Rating - °C

Construction Data

Casing Material

Casing Finish

Blade Configuration

Blade Material

Blade Finish

Side Seal Material

Spring Material

Release Mechanism

Dimensional Data

Frame Width (Top) – mm

Frame Width (Bottom) – mm

Frame Width (Sides) – mm

Max Damper Height – mm

Max Damper Width – mm


Blades Out of Airstream Mechanical Position Indicator

Installation Frame Damper Position Microswitches

Dry Wall Frame Remote Mechanical Release

Fire Curtain Frame Remote Electrical Release

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5. PSD M3-10-5, SMOKE DAMPERS

Job Title:


General Data

Unit Reference

Quantity

Location

System

Type


d Offer

ed Require

d Offere

d Require

d Offered

Fire Rating – hours

Max Face Velocity (MFV) – m/s

Air Pressure Drop @ MPF – Pa

Max Differential Press. (Closed) – Pa

Damper Air Leakage @ 500 Pa – l/s.m²


Fusible Link Temperature Rating - °C

Electrical Supply – V/∅/Hz

Construction Data

Casing Material

Casing Finish

Blade Configuration

Blade Material

Blade Finish

Side Seal Material

Spring Material

Release Mechanism

Dimensional Data

Frame Width – mm

Length – mm

Max Damper Height – mm

Max Damper Width – mm


Installation Frame � Motorised Remote Reset

Dry Wall Frame Mechanical Position Indicator

Fire Curtain Frame Damper Position Microswitches

Manual Reset Actuator Mounting Sleeve

Integral Reset Button & Status Lamp Access Panel �

Fail Closed

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