1 DW/144 Specification for Sheet Metal Ductwork Low, medium and high pressure/velocity air systems 1998 Copyright © 1998 by the Heating and Ventilating Contractors' Association All rights reserved ISBN 0-903783-27-4 Further copies of this publication are available from: Publications Unit Heating and Ventilating Contractors Association Old Mansion House Eamont Bridge Penrith Cumbria CA10 2BX Tel: 01768 860405 Fax: 01768 860401 e-mail: hvcapublications@welplan.co.uk THE INDUSTRY STANDARD Ken Parslow Chairman Executive Committee Ductwork Group 1996-98 For more than a decade-and-a-half, the DW/142 Specification for Sheet Metal Ductwork published by the Heating and Ventilating Contractors' Association has gained national and international recognition as the industry standard against which the quality of ductwork manufacture and installation can be judged In recent years, however, it has become increasingly evident to the members of the HVCA Ductwork Group that the developments in technology and working practices which have taken place since the drafting of DW/142 have rendered obsolete significant parts of the document It was an acknowledgement of this state of affairs which led the Technical SubCommittee of the Ductwork Group, ably chaired by Edgar Poppleton, to undertake the task of producing a radically revised specification which would promote best practice and quality standards well into the next Millennium This new publication - designated DW/144 - represents the direct result of that initiative The new specification recognises the computer age - with special reference to CAD/CAM procedures and techniques - and the international performance standards established by the Committee for European Normalisation (CEN), as well as the need to update and consolidate much of the information contained in the original DW/142 publication and its Addendum A companion volume During the drafting process, the Technical Sub-Committee has consulted widely with individuals and organisations throughout the building services and construction sectors in order to ensure that the new specification fully reflected the current the "state-of-theart" in terms both of technical expertise and industry best practice I firmly believe that this process has resulted in a publication which clearly demonstrates the high level of professionalism which exists within the ductwork community - and I take this opportunity of thanking all those who have contributed to its production In particular, my thanks go to Edgar Poppleton and his colleagues on the Technical Sub-Committee, to Keith Elphick for the provision of invaluable technical consultancy, and to Ductwork Group secretary Gareth Keller for overseeing the project as a whole MAINTAINING QUALITY Like most industries, the ductwork sector must be prepared continually to innovate in order to survive and prosper A key element in that innovation process is the timely review and updating of quality standards to ensure that they continue to offer realistic benchmarks to which all professional individuals and organisations can perform The development of this new Specification for Sheet Metal Ductwork - designated DW/144 - has been carried out with that objective in mind In the 16 years since the publication of its predecessor, DW/142 - and in the ten years since the supplementary volume Addendum A appeared many technical advances, changes in working practices and regulatory introductions and amendments have taken place The common performance standards for ductwork being developed by the Committee for European Normalisation (CEN), for example, had to be taken fully into account during the drafting process Similarly, notice had to be given to the provisions of the Control of Substances Hazardous to Health (COSHH) and Construction (Design and Management) Regulations, neither of which had been issued when DW/142 was published It is not possible - nor, I think, desirable - to include in this foreword an exhaustive catalogue of the points of difference between this specification and its predecessor These will clearly emerge from a detailed reading of the text I should, however, like to take the opportunity to highlight a few topics which I believe to be of particular significance They are: • the omission of high-pressure Class D (in order to conform to European practice); • the highlighting of information to be provided by the designer; • the end-sealing of ducts and explosion risks; • the removal of standard sizes of rectangular ducts; • the omission of cleated joints; • the acceptance of proprietary flanges certificated to DW/TM I no longer illustrated in detail; • the consolidation into the document of coverage of hangers and supports; • the addition of a note on linings, along with their cleaning considerations; • the consolidated graphical representation of Class A, B and C air leakage characteristics, mandatory testing Class C only; • updated appendices on galvanising after manufacture, stainless steel, pre-coated steel, aluminium, Eurovent and galvanised material, plus a bibliography; • transport, handling, storage and interface with DW/TM2 Guide to Good Practice – Internal Cleanliness of New Ductwork Installations; • an overview of fire-rated ductwork; • a new appendix on inspection, servicing and cleaning access openings (the default inclusion of Level should be noted); • a new section on standard component drawings - incorporating a framework of nomenclature, and a description of drawing symbols, abbreviations and rules - which is intended to reduce ambiguity and promote common understanding; • a rewritten description of all forms of dampers, for which I am indebted to Bill Clark and John Mawdsley of the HEVAC Association I take this opportunity to acknowledge the permission granted by the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) of the USA for the use of its tie rod specification (designer approval required) And I also include a plea on behalf of ductwork constructors to be allowed to make the final choice of components and techniques within the parameters set by the designer, and allowed within this specification to satisfy performance characteristics It will, of course, be clear to anyone who has ever taken on such a task that the production of this specification has involved a colossal input in terms of industry consultation and from a wide variety of individuals, a number of whom I should like to identify for special mention They are: former Technical Sub-Committee members Keith Waldron and the late Keith Angood; current members Chris Collins, Stuart Howard, Brian James and - last but by no means least - Jim Murray; technical consultant Keith Elphick; and Ductwork Group secretary Gareth Keller Finally, may I remind readers of the crucial importance of ensuring that all ductwork is manufactured and installed in a manner which is safe, efficient, effective and free of risk The publication of DW/144 is intended to assist significantly in the achievement of this objective Acknowledgements The HVCA wishes to record its sincere thanks to the following members - past and present - of the Technical Sub-Committee of the Ductwork Group, who contributed their time, knowledge and experience to the production of this document Edgar Poppleton (chairman) Keith Angood Chris Collins Stuart Howard Brian James Jim Murray Keith Waldron Technical Consultant: Keith Elphick Ductwork Group Secretary: Gareth Keller Contents Page Notes 10 Part One - Technical Information to be provided by the designer Introduction 11 Standards 11 Components 11 Particular Requirements 11 Part Two - Standards Application Ductwork Classification and Air Leakage Materials Ductwork Construction and Joint Sealing Part Three - Rectangular Ducts Rectangular Duct Sizes 10 Construction 10.1 General 10.2 Steel Thicknesses 10.3 Longitudinal Seams 10.4 Cross Joints 10.5 Stiffeners 10.6 Ductwork Galvanised After Manufacture 10.7 Fastenings 11 Fittings 11.1 Standardisation of Fittings 11.2 Stiffeners 11.3 Splitters 11.4 Turning Vanes 11.5 Branches 11.6 Change Shapes 11.7 Expansions and Contractions 11.8 Sealant Part Four - Circular Ducts 12 Standard Sizes 13 Construction 13.1 Longitudinal Seams 13.2 Cross Joints 13.3 Fastenings 14 Fittings 14.1 Standardisation of Fittings 14.2 Nominal Diameters 14.3 Sheet Thickness 14.4 Sealing of Joints Part Five - Flat Oval Ducts 15 Standard Sizes and Sheet Thicknesses 16 Construction (Spirally wound) 16.1 General 16.2 Longitudinal Seams 16.3 Cross Joints 16.4 Fastenings 16.5 Stiffening 17 Construction (Straight Seamed) 18 Fittings 18.1 General Construction Requirements 18.2 Standardisation of fittings 35 35 35 35 35 35 Part Six - Hangers and Supports 19 General 43 Part Seven - General 20 Access/Inspection Openings 21 Regulating Dampers 22 Fire Dampers 23 Smoke Dampers 24 Combination Smoke and Fire Dampers 25 Flexible Ducts 26 Flexible Joint/Connections 27 Protective Finishes 28 Connections to Building Openings 29 Internal Duct Linings 30 Thermal Insulation 31 Kitchen Ventilation 32 Fire Rated Ductwork 33 Standard Component Drawings and Abbreviations 13 13 13 14 15 15 15 15 15 15 15 16 16 16 16 16 16 16 16 16 17 17 Part Eight - Appendices Appendix A Air Leakage from Ductwork Appendix B Identification of Ductwork Appendix C Guidance Notes for the Transport, Handling and Storage of Ductwork Appendix D Ductwork Systems and Fire Hazards Appendix E Hot Dip Galvanizing after Manufacture Appendix F Stainless Steel for Ductwork Appendix G Pre-Coated Steel Appendix H Aluminium Ductwork Appendix J Eurovent Appendix K Summary of BS.EN10142: 1991 Continuously Hot-Dip Zinc Coated Mild Steel Strip and Sheet for Cold Forming Appendix L `Design Notes for Ductwork' (CIBSE Technical Memorandum No 8) Appendix M Guidance Notes For Inspection, Servicing and Cleaning Access Openings Appendix N Bibliography Appendix P Conversion Tables 27 27 27 27 27 29 29 29 29 29 35 35 35 35 35 47 48 49 50 51 51 52 53 53 54 54 54 54 54 75 80 82 83 85 86 89 90 91 92 93 94 95 97 List of Tables Table Page Part Two - Standards Ductwork Classification and Air Leakage Limits Part Three - Rectangular Ducts Constructional Requirements Low Pressure up to 500Pa Constructional Requirements Medium Pressure up to 1000Pa Constructional Requirements High Pressure up to 2000Pa Fastening Centres Part Four - Circular Ducts Standard Sizes Spirally-Wound Ducts Straight-Seamed Ducts Permitted fastenings and maximum spacings 10 Fittings Sheet Thicknesses Part Five - Flat Oval Ducts 11 Standard sizes and sheet thicknesses 12 Stiffening requirements low and medium pressures 13 Stiffening requirements high pressure 14 Permitted fastenings and maximum spacings 13-17 18-24 25-28 29 30 Socket and spigot cross joints Stiffeners Tie rod assembly Hard and Easy bends Turning Vanes 31 32-38 39-45 Part Four - Circular Ducts Spiral and straight seams Cross joints spirally wound ducts Cross joints straight seamed ducts 29 30-31 32-33 53-58 59-63 Part Five - Flat Oval Ducts Cross joints spirally wound ducts Cross joints straight seamed ducts 39-40 41-42 Part Six - Hangers and Supports Horizontal ducts bearers and hangers Vertical ducts supports 45-46 46 13 18 19 19 24 64-75 27 28 28 76-77 Part Seven - General Fire barrier/Fire damper expansion Flexible joint connections Standard component drawings Rectangular 125-152 Standard component drawings Circular 153-167 Standard component drawings Flat Oval 168-177 Plant/equipment/miscellaneous 78-79 80 81-124 29 29 36 37 38 40 178 Part Six - Hangers and Supports 15 Supports for horizontal ducts - rectangular, flat oval and circular Part Seven - General 16 Standard Abbreviations Part Eight - Appendices 17 Air Leakage Rates 18 Recommended duct identification colours 19 Examples of further identification symbols 20 Ductwork galvanized after manufacture rectangular 21 Compositions of the commonly used Stainless Steel grades 22 Rectangular aluminium ducts low pressure constructional requirements 23 Circular aluminium ducts low pressure constructional requirements 24 Zinc coating mass (weight) 25 Access requirements for inspection, servicing and cleaning 179 44 72-73 76 80 81 85 88 90 91 93 94 List of Illustrations Figs 1-8 10-12 Pages Part Three - Rectangular Ducts Longitudinal Seams Illustrations of panel stiffening Flanged cross joints 22 23 24 25 25 20 20 21 Part Eight - Appendices Permitted leakage at various pressures Example of duct identification symbol 50 52 55-61 62-67 68-70 71 78 81 Type 2B Cold rolled, softened, descaled and lightly worked with polished rolls A smooth finish brighter than 2D Type 2A/2R Bright annealed A cold finished reflective appearance retained through annealing essary, however, depending on the type of stainless steel being used F.6.3 As a general rule, the 400 series of stainless steels can be formed using normal mild steel settings The 300 series, however, because of the higher yield point and the greater rate of work hardening, will require higher working pressures Polished finishes Type 4/2J Dull polished A lustrous unidirectional finish produced by fine grinding, generally with abrasives of 150 grit size It has little specular reflectivity Further dull polishing after fabrication will diminish the effects on appearance of welds or accidental damage by blending them into the surrounding metal Type 5/2K Dull polished with specific requirements, to achieve a fine, clean cut surface finish with good corrosion resistance Type 8/2P Mirror polished A bright, nondirectional reflective finish with a high degree of image clarity F.6.4 Ductwork contractors who have experience of the use of stainless steel report difficulty in forming Pittsburgh and button punch snap lock seams As regards cross joints, socket and spigot joints are recommended, and one or two of the slide-on flanges are suitable In view of the foregoing, it is recommended that trials be carried out before starting on production F.7 Rectangular ducts The constructional requirements for rectangular stainless steel ducts are the same as for galvanized mild steel F.8 Circular ducts The constructional requirements for circular stainless steel ducts are the same as for galvanized mild steel F.9 Stiffening Wherever possible, the material used for stiffening should be of the same grade of stainless steel as used for the construction of the ducts, or should be made equally corrosion resistant to suit the environment in which the ductwork is situated F.4.2 Where other finishes are required, such as for aesthetic purposes, a range of patterned or textured (2F,2M) finishes is available Colour may be applied in the form of paint or lacquer, or the material may be supplied pre-coloured as by the 'INCO' process or by mill application of polymer coatings F.10 Fixings and fastenings The types of fastening and the maximum spacings specified in Table (rectangular) and Table (circular) also apply to stainless steel ductwork Fixings and fastenings should be of the appropriate grade of stainless steel as used in the construction of the ductwork, or should be made equally resistant to corrosion in relation to the environment in which the ductwork is situated The type of stainless steel fastening used should conform to the appropriate specification BS 6105: 1981 F.5 Surface protection F.5.1 No surface protection is required for stainless ductwork used indoors or outdoors, provided the correct quality is specified This is because the naturally occurring chromium-rich oxide film which is present on the surface of the metal, if damaged, reforms immediately by reaction between the steel and the atmospheric or other source of oxygen F.5.2 If a mixture of metals is used, such as mild steel supports for stainless steel ductwork, the surface of the mild steel must be adequately protected from the galvanic corrosion that might result from the intimate contact between the two types of metal (The appropriate protective finish should be employed See 27.3.5) F.11 Welding All the modern welding processes may be used to weld stainless steel but carburising operations such as oxyacetylene and carbon arc welding are not suitable The Tungsten inert gas (TIG) and resistance welding techniques are most likely to be used for thin gauge materials Attention is drawn to BS 4872: Part 1982, (welder qualification) and BS 7475: 1991 (welding processes) F.6 Construction F.6.1 Sheet thicknesses for stainless steel ductwork should be the same as for galvanized steel (see Tables 2, and 4) Provided the correct grade of stainless steel has been selected, there is no requirement for a corrosion allowance with stainless steels and the gauge can be selected on structural considerations only Selection of the correct welding electrodes and filler rods is important, particularly when welding dissimilar metals, such as stainless steels to non-stainless structural steels Reference for guidance should be made to BS 2901: Part 2: 1990 for rods and wires for gas shielded welding and BS 2926:1984 for electrodes for Manual Metal Arc (MMA) welding F.6.2 The forming of rectangular and circular ducts can be carried out by the use of conventional press working and sheet metal forming machines Some alteration in working practices may be nec- F.12 Avoidance of contamination Attention is drawn to the risks of rust staining of stainless steel surfaces resulting from contamination by nonstainless steel or iron debris 87 If particles such as filings of a non-stainless steel or iron are expressed into contact with a stainless steel, subsequent exposure to moisture will lead to staining of the surface as these particles rust Whilst this staining often can be removed without harm to the stainless steel surface, in aggressive environments corrosion products around the rust centre can create a risk of pitting of the stainless steel As a general rule, stainless steels should be kept free from iron dust and debris contamination In particular, wire brushes must be made of stainless steel and shot, beads and abrasive media used to clean surfaces must be `iron free' Contamination can arise from tools which have been used previously for cutting non-stainless steels without adequate cleaning and from abrasion on stillages and racks It is good practice to dedicate storage and bench areas for stainless steels, with soft surfaces, e.g wooden battens, to mininise scratching of the surface and if practicable designate stainless only working areas F.13 Fire dampers Stainless steel is an ideal material for use in the construction of fire dampers, because of its high resistance both to heat and corrosion It is therefore most applicable where a fire authority specifies a requirement for corrosion resistance F.14 Sealants, gaskets and tapes The sealing materials and methods set out in this publication are also applicable to stainless steel ductwork However, any chloride-based material, such as polyvinyl chloride (PVC), should be avoided, as breakdown of such material at certain elevated temperatures could lead to corrosion of the stainless steel F.15 General design considerations It is the designer's responsibility to indicate the type of stainless steel most suitable for the conditions to which the ductwork is to be exposed If users and designers are in doubt as to which material is appropriate to a particular application, technical advice may be obtained from the source noted below Table 21, showing the approximate correspondence between the chemical compositions of the commonly used stainless steel grades in BS 1449, Part 2: 1983, and the European Standard EN 10088-1, List of Stainless Steels (Part gives the chemical compositions and identifications of the stainless steels, it is for information Part of this standard describes the technical delivery conditions for sheet/plate and strip for general purposes.) This appendix is based largely on information kindly supplied by the Avesta Sheffield Technical Advisory Centre, ASTAC, P.O Box 161, Shepcote Lane, Sheffield S9 l TR Telephone: 0114 244 0060 Fax: 0114-242 0162 88 APPENDIX G - PRE-COATED STEEL G.1 Nature of the material G.1.1 'Pre-coated' steel is sheet, coil or strip to which has been applied at the steel mills a coating having a decorative or protective function, or both G.5 Ductwork construction from pre-coated steel G.5.1 The type of pre-coated steel most suitable for ductwork should be carefully considered, mainly from the point of view of the fabrication properties of the coating type It is probable that a plastisol coating will be found to be most suitable for ductwork, as this type of coating will withstand forming at normal ambient temperatures It also tolerates rougher handling during forming and erection than the much thinner paint coating types G.1.2 The basis metal to which the coatings are applied are hot-dip galvanized or aluminium-zinc coated sheet or coil, uncoated steel or electrogalvanized steel (e.g., Zintec) G.2 Range of coatings available G.2.1 A number of different types of coating, in various thicknesses, are available - PVC ('Plastisol' and 'Organosol'); paint coatings of several types, silicone enamels, etc G.5.2 Careful consideration should be given to the constructional methods to be used for ductwork to be made from pre-coated steel The principle to be followed should be to make seams and joints as unobtrusive as possible Some of the conventional methods of seaming may be used, but a number of others are not suitable Welding with conventional equipment should not be attempted Mechanical fastenings should be chosen with care having regard to appearance as well as efficiency; and sealant should be applied with these factors in mind Stiffening should be carefully considered in relation to appearance G.2.2 A wide range of colours and surface finishes are available, but there are minimum quantity requirements for some types of coating, finish and colour The characteristics of the particular type of coating contemplated for a particular use should be investigated in respect of formability, fastness to light, chemical resistance and other relevant properties G.2.3 The material can be supplied with one or both sides treated, with the specified coating Standard `backing coat' finishes are usually applied to the reverse side unless otherwise stated G.6 Handling, storage, transport and erection G.6.1 Much more care than usual is required in these respects, as the coatings are all to a greater or lesser degree susceptible to mechanical damage For example, sheet should not be dragged off the top of a pile but removed by `turning' off the stack G.3 Sizes available G.3.1 Pre-coated steel is available in sheet or coil form The maximum available width can vary according to the steel thickness required Availability varies according to type of substrate and coating, so prospective purchasers should query the sizes available for the specific type required G.6.2 With sheet pre-coated on one side only, it may be found desirable to stack face to face G.6.3 The flexibility of coatings of the types used on pre-coated steel depends on temperature Therefore, manipulation should be carried out at temperatures above 16°C (60°F) in order to minimise the risk of the film cracking on roll forming, etc If the material has been stored outside at low temperature, a warm-up period should be allowed before manipulation of the sheet is undertaken G.4 Sources of supply G.4.1 Pre-coated steel is widely available but it should be noted that minimum order quantities may apply The information on which this appendix is based has been kindly supplied mainly by British Steel plc More detailed information may be obtained from: British Steel plc, Product Development Centre, Shotton Works, Deeside, Flints CH5 2NH Telephone: Chester (01244) 812345 Fax: 01244 836134 89 APPENDIX H - ALUMINIUM DUCTWORK H.1 Scope This section applies only to rectangular and circular aluminium ductwork operating at low pressure, as defined in Tables 22 and 23 If consideration is being given to either higher pressures or flat oval ductwork then it would be prudent to seek advice from manufacturers who have the experience and capacity to manufacture aluminium ductwork H.2 Suitable grades H.2.1 Ductwork can be constructed from all the commonly used aluminium alloys, the choice depending on the purpose for which the ducts will be used and the service environment H.2.2 The alloys 1200, 3103 and 5251 (as specified in BS.EN485, BS.EN515, BS.EN573) are easy to form and to join, and have excellent resistance to atmospheric corrosion, with 5251 being rather more resistant to marine atmospheres H.2.3 These alloys can be supplied in various tempers produced by different degrees of cold rolling, so that a range of strengths is available In choosing a temper, it is necessary to consider any forming that will be done, as with the harder tempers the forming of tight bends might cause cracking Where high strength is required, alloy 6082-T6 sheet can be used H.2.4 Aluminium coil is available in plain form and prepainted finish H.3 Construction - rectangular ducts H.3.1 Table 22 sets out the minimum constructional and stiffening requirements for rectangular aluminium ducts and the permitted types of cross joint H.3.2 Sealant The sealant requirements set out in this specification for galvanized steel rectangular ductwork also apply to the longitudinal seams and cross joints in aluminium ductwork H.4 Construction - circular ducts H.4.1 Table 23 sets out the minimum constructional and stiffening requirements for circular ducts made from aluminium, and the permitted types of cross joint H.5 Fastenings H.5.1 The types of fastening and the maximum spacings specified in Table (rectangular) and Table (circular) apply to aluminium ductwork, except that such fastenings shall be of aluminium, stainless steel or monel metal H.6 Welding H.6.1 All the aluminium alloys can be welded by MIG (Metal and Inert Gas) or TIG (Tungsten and Inert Gas) methods, with argon as the shielding gas Helium or a mixture of helium and argon can be used, but not CO2 Alloys in a work-hardened temper are reduced to the annealed condition in the heat affected zone; 6082-T6 is reduced approximately from the T6 to the T4 temper Alloys 1200 and 3103 are easy to braze, as is 6082, but the latter needs to be re-heat treated to regain its strength H.7 Protective finishes H.7.1 No protective finishes are required for aluminium ductwork used indoors or outdoors in normal atmospheric conditions In moist atmospheres, particularly if they are contaminated by industrial effluent or by salt from the sea, surfaces not exposed to washing by rain will become roughened and covered with a layer of white corrosion product However, this has the effect of sealing the surface against further attack, and the mechanical properties of any but the thinnest of materials will be only slightly affected H.7.2 If surface protection is specified, any of the normal organic finishes can be used, including the laminated PVC films, although paints with heavy metal pigments are not suitable The use of prepainted strip in coil form provides a reliable quality finish and often proves more economical than painting after assembly Anodising provides an excellent finish for aluminium, but this process would have to be carried out after forming and would therefore not usually be practicable for ductwork, except perhaps for ducts formed from extrusions H.7.3 Mild steel section used in supporting aluminium ductwork shall have a protective finish (See 27.3.5) 90 Incorporates information provided by the Aluminium Federation Ltd., Broadway House, Calthorpe Road, Five Ways, Birmingham B15 1TN (telephone: 0121-456 1103), from whom more detailed information may be obtained APPENDIX J - EUROVENT J.1 General Some explanation of the function, composition, objectives and membership of EUROVENT is given below tate commercial exchanges between its member nations in the search for improved quality; and the adoption of rules, directives and codes of practice in the technical and economic spheres in the member countries' J.2 Membership EUROVENT is an omnibus word standing for the European Committee of the Construction of Air Handling Equipment The committee was formed in 1959, and in 1977 its constituent members were the relevant national associations in Austria, Belgium, Denmark, Finland, France, German Federal Republic, Italy, Netherlands, Norway, Sweden, Switzerland and the United Kingdom J.4 EUROVENT publications EUROVENT has published a number of documents in the air handling field, and these include Document 2/2 covering the procedure for testing for air leakage in ductwork, and provides for two levels of permissible air leakage for low-pressure air distribution systems Document 2/3 covers the standardisation of duct sizes J.5 Air leakage The basis on which air leakage is calculated in EUROVENT Document 2/2 has been adopted in DW/143 A practical guide to Ductwork Leakage Testing J.3 Objectives The objectives of EUROVENT are `to improve and develop technical matters in the manufacture and operation of air handling equipment; to improve the professional status of its members and to facili- Information about EUROVENT may be obtained from the HEVAC Association, Sterling House, Furlong Road, Bourne End, Bucks SL8 5DG (Telephone: 01628 531186 Fax: 01628 810423) 91 APPENDIX K - SUMMARY OF BS.EN10142: 1991 CONTINUOUSLY HOT DIP ZINC COATED MILD STEEL STRIP AND SHEET FOR COLD FORMING Note - The extracts from BS.EN 10142: 1991 have been prepared by the HVCA and are included here by courtesy of the British Standards Institution K.1 GENERAL K.1.1 The BS 2989: 1975 and 1982 entitled `Continuously hot-dip zinc coated and iron-zinc alloy coated steel: wide strip, sheet/plate and slit wide strip' summarised in DW/142 has been superseded by BS.EN10142: 1991 entitled `Continuously hot-dip zinc coated mild steel strip and sheet for cold forming' (including amendment A1:1995) K.1.2 British Standard BS.EN10142: 1991 sets out requirements for the conventional galvanized sheet and coil and for zinc-iron coated steel (Both these are included in DW/144 - see Section 7.) The type of steel normally used for ductwork is DX51D and Z275 K.2 STEEL GRADES K.2.1 BS.EN10142: 1991 and the grades of steel set out in others: Grade Name of grade DX51D + Z Bending and profiling quality DX52D + Z Drawing quality DX53D + Z Deep drawing quality DX54D + Z Special deep drawing quality Normal spangle (N) This finish is obtained when the zinc coating is left to solidify normally Either no spangle or zinc crystals of different sizes and brightness appear depending on the galvanizing conditions The quality of the coating is not affected by this NOTE Normal spangle is the type normally supplied for a wide variety of applications Minimized spangle (M) The surface has minimized spangles obtained by influencing the solidification process in a specific way The finish may be specified if the normal spangle applicable does not satisfy the surface appearance requirements K.5 SURFACE PROTECTION K.5.1 General Hot-dip zinc coated strip and sheet products generally receive surface protection at the producer's plant The period of protection afforded depends on the atmospheric conditions amendment A1:1995 lists the next column, among K.5.2 Chemical Passivation Chemical Passivation protects the surface against humidity and reduces the risk of formation of `white rust' during transportation and storage Local discolouring as a result of this treatment is permissible and does not impair the quality Application Forming quality steel suitable for manufacture of the most profiles and more difficult bending operations Forming quality steel suitable for simple drawing operations and for more difficult profiling operations Forming quality steel suitable for deep drawing and difficult forming operations Forming quality steel suitable for deep drawing and difficult forming operations where a nonageing steel is required K.5.3 Oiling This treatment also reduces the risk of corrosion of the surface It shall be possible to remove the oil layer with a suitable degreasing solvent which does not adversely affect the zinc K.5.4 Chemical Passivation and Oiling Agreement may be reached with the producer on this combination of surface treatment if increased protection against the formation of `white rust' is required K.5.5 Untreated Hot-dip zinc coated strip and sheet products complying with the requirements of this standard are only supplied without surface protection if expressly desired by the purchaser on his own responsibility In this case, there is increased risk of corrosion K.6 FORMING K.6.1 The British Standard says that provided that the profiling machine is set to avoid excessive stretching in the product, it is possible to form lock seams successfully with DX51 D + Z sheet up to a thickness of 1.5 mm and DX52D + Z sheet up to mm; and snap lock seams with DX51 D + Z up to 0.9 mm thick sheet and DX52D + Z sheet up to mm K.3 COATING TYPES AND TOLERANCES K.3.1 The types of zinc coating are set out in Table 24 BS.EN10142: 1991 (reproduced at the foot of this summary) K.3.2 Whilst the coating thickness is not subject to tolerances the substrate and consequently the gauge thickness does have accepted tolerances and these including sheet widths/lengths will be found in BS.EN10143: 1991 K.4 COATING FINISHES K.4.1 BS.EN10142: 1991 and A1 1995 includes a description of the various types of finish available: K.7 WELDING K.7.1 Care should be taken to use proper methods and procedures The iron-zinc coating is more suitable for resistance welding than the conventional zinc coating 92 APPENDIX L -'DESIGN NOTES FOR DUCTWORK' (CIBSE Technical Memorandum No 8) L.1 At the time of publication (1983) this technical memorandum brought together information on the design of ductwork systems L.2 The contents had been drawn from the relevant sections of the CIBSE Guide and other recognised references, and include additional material on good design practice The Notes make frequent reference to DW/142, and an effort was made to ensure consistency between the two publications Whilst DW/142 has now been superceded by DW/144, the technical memorandum, has not currently been updated but still contains relevant information that may be of use to a ductwork designer/manufacturer Whilst some of the information may now be superceded, TM8 includes chapters on: Pressure loss in ducts, including corrections for duct surface type, air pressure, air density, temperature and altitude, and loss factors for fittings Equivalent diameters of rectangular and flat oval ducts Standard dimensions of circular, rectangular and flat oval ducts Duct sizing methods, including velocity, equalfriction and static regain methods, and pressure loss calculations, with an example calculation Heat loss from and gain to air in the duct; condensation, noise control and fire Commissioning and testing Overseas work Drawing symbols in current use L.3 The flow of heavily contaminated air in ducts is not covered in detail in the Notes; nor are the constructional aspects of ductwork, which are dealt with in DW/144 L.4 The Notes were completed by references, a bibliography of over thirty titles and appendices covering properties of air, ductwork support loads, velocity pressure for air flow and conversion to SI units Technical Memorandum No was published by the Chartered Institution of Building Services Engineers, Delta House, 222 Balham High Road, London SW12 9BS (Telephone: 0181 675 5211) and whilst it is no longer available as a publication, it is still available in photo-copy form 93 APPENDIX M - GUIDANCE NOTES FOR INSPECTION, SERVICING AND CLEANING ACCESS OPENINGS M.1 GENERAL This appendix highlights, in summary form, the access consideration that should be made by the designer in terms of inspection, servicing and cleaning Having considered the scope and the design of the ductwork system relative to the guidelines outlined below the designer should clearly indicate which levels of access should be incorporated into the manufacture of a new ductwork system (See Table 25 and Note below it) M.2 DESIGN CONSIDERATIONS M.2.1 Inspection and servicing requirements are set out in Section 20 of this specification M.2.2 Cleaning requirements are set out in the HVCA publication TR17 "Guide to Good Practice, Cleanliness of Ventilation Systems" and the guide states "The precise location, size and type of access would be dependent on the type of ductwork cleaning, inspection and testing methods to be adopted." Care, protection and standards of cleanliness prior to commissioning are set out in the HVCA publication DW/TM2 "Guide to Good Practice, Internal Cleanliness of New Ductwork Installations" and the guide states "Where specific limits of cleanliness are required, ductwork shall be cleaned after installation by a specialist cleaning contractor." It will be in the interests of the designer, both financially and practically, to consider employing a specialist cleaning contractor at the outset of a contract to internally clean newly installed ductwork prior to handover This approach would realise the following benefits: i) The actual number of cleaning access panels could be determined to suit the method of cleaning to be adopted (This may be less than the maximum requirements listed under Level of Table 25) ii) Clear directions could be given to the ductwork contractor as to the size and location of cleaning access panels that are required to be fitted during the manufacturing process iii) The specialist cleaning operation prior to commissioning would enable the cleaning contractor to verify the practical access requirements for the future cleaning operations associated with a regular maintenance programme iv) A specialist cleaning operation prior to commissioning would allow the designer to omit from the specification the DW/TM2 requirements for factory sealing, protection, wipe downs and capping-off v) Specialist cleaning to the measurable standards defined in TR17 will allow an objective definition of cleanliness to be achieved Careful consideration must be given by the designer to the practical problems associated with the manufacture and fitting of suitably sized access panels on small cross section ducts and the circular faces of round and flat oval ducts in particular M.2.3 Special consideration must be given by the designer to the practical problems associated with gaining personnel access to heavily congested ceiling areas and multi-layered ductwork systems This approach would avoid the possibility of access panels being incorporated into a ductwork system at the manufacturing stage that were later found in practice to be inaccessible for either servicing or cleaning activities M.3 ACCESS TO IN-LINE EQUIPMENT This appendix only covers access/inspection through the ductwork body adjacent to an item of in-line equipment and not openings in the equipment itself 94 APPENDIX N - BIBLIOGRAPHY Research Reports RR01/95: Ventilation system hygiene - A review of published information on the occurrence and effects of contamination RR02/95: Air-to-air heat recovery RR03/95: Influence of HVAC on smoke detectors Included in this Bibliography are technical publications which may be of interest to ductwork designers fabricators and erectors, and to those in the heating, ventilating, air conditioning industries generally Enquiries should be made of the relevant organisation, at the address quoted Since its publication other addresses contained within DW/144 may have changed, and some publications may have been superseded NATIONAL ENGINEERING SPECIFICATION LIMITED Southgate Chambers, 37/39 Southgate Street, Winchester S023 9EH (Telephone: 01962 842058; Fax: 01962 868982) BUILDING SERVICES RESEARCH AND INFORMATION ASSOCIATION Old Bracknell Lane West, Bracknell, Berkshire RG12 4AH (Telephone: Bracknell (01344) 426511; Fax: 01344 487575) HEATING AND VENTILATING CONTRACTORS’ ASSOCIATION 34 Palace Court, London W2 4JG Telephone: 0171-229 2488; Fax: 0171-727 9268 Orders to HVCA Publications, Old Mansion House, Eamont Bridge, Penrith Cumbria CA10 2BX (Telephone: 01768 864771 Fax: 01768 867138) Email: hvcapublications@hvwelfare.co.uk DW/144 DW/143 DW/151 DW/171 DW/191 DW/TM2 DW/TM3 Specification for sheet metal ductwork (low-, mediumand high-pressure) (1998) A practical guide to ductwork leakage testing (1983) Specification for plastics ductwork Guide to good Practice for kitchen ventilation systems Guide to good practice glass fibre ductwork DWITM1 Acceptance scheme for new products -Rectangular cross joint classification Guide to good practice - Internal cleanliness of new ductwork installations Guide to good practice for the design for the Installation of fire and smoke dampers Application Guides AG.1/74 Designing Variable Volume Systems for Room Air Movement AG.I/91 Commissioning of VAV Systems in Buildings TN.6/94 Fire Dampers LB.65/94 Ventilation of Kitchens AG.3/89 The Commissioning of Air Systems in Buildings AH.2/92 Commissioning of Bems - A Code of Practice TN.24/71 Fire Dampers in Ventilating Ducts HEATING, VENTILATING AND AIR CONDITIONING MANUFACTURERS ASSOCIATION (HEVAC) Sterling House, Furlong Road, Bourne End, Bucks SL8 5DG (Telephone: 01628 531186 Fax: 01628 810423 Email: info@feta.co.uk) Other publications JSI H&V safety guide 5th edition JS2 Tool box talks JS5 Welding Safety booklet JS19 Safety facts booklet Fact sheets 1-24 2nd edition JS21 COSHH manual volume I Advice on compliance with the regulations JS 21A COSHH manual volume Assessment sheets JS23 Risk management manual TR/3 Brazing and bronze welding of copper pipework and sheet(1976) TR5 Welding of carbon steel pipework (1980) TR6 Guide to Good Practice for Site Pressure Testing of Pipework (1980) TR17 Guide to good practice cleanliness of ventilation systems Publications Air Diffusion Guide Guide to Air Handling Unit Leakage Testing Guide to Good Practice: Air Handling Units Real Room Acoustic Test Procedure Specification for the Certification of Air Filters Method of Test for Water Rejection Performance of Louvres Subjected to Simulated Rainfall CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS Delta House, 222 Balham High Road; London SW12 9BS (Telephone: 0181-675 5211 Fax: 0181-675 5449) Test Procedure for Acoustic Louvres CIBSE Guide Volume A Design Data Volume B Installation and Equipment Data Volume C Reference Data Fan Application Guide Commissioning Codes These Codes cover the preliminary checks, setting to work and regulation of various categories of plant The Codes give a guide to design implications Series A Air Distribution Systems Series B Boiler Plant Series C Automatic Control Systems Series R Refrigerating Systems Series W Water Distribution Systems Specification of Requirements for Natural Smoke and Heat Exhaust Ventilators Specification for Floor Grilles - Types, Performance and Method of Test Specification for the Determination of the Collection Efficiency of Sand Trap Louvres Domestic Mechanical Ventilation Systems with Heat Recovery Fan and Ductwork Installation Guide Guide to Fan Noise and Vibration Specification for Powered Smoke and Heat Exhaust Ventilators Specification of Requirements for Smoke Curtains Design Guide of Smoke Ventilation for Single Storey Industrial Buildings Including those with Mezzanine Floors and High Racked Storage Warehouses - Issue Guidance for the Design of Smoke Ventilation Systems for Covered and Underground Car Parks - Issue Application of Smoke Control Equipment and Systems: Guide to Good Practice - Issue Technical Memoranda TM Design Notes for the Middle East TM Design Notes for Ductwork TM 13 Minimising the Risk of Legionnaires Disease 95 BRITISH STANDARDS INSTITUTION Sales Department, 101 Pentonville Road, London N1 9ND (Telephone: 0171-837 8801) BS 381 C: 1996 CP 413: 1973 Colours (of ready-mixed paints) for specific purposes Ducts for building services BS 476: Fire tests on building materials and structures Part 4: 1984 Non-combustibility test for materials Part 6: 1989 Fire propagation test for materials Part 7: 1993 Surface spread of flame tests for materials SHEET METAL AND AIR CONDITIONING CONTRACTORS' NATIONAL ASSOCIATION INC (SMACNA) Headquarters: 4201 Lafayette Center Drive Chantilly Virginia 20151-1209 Mailing Address P.O Box 221230 Chantilly Virginia 20153-1230 Telephone (703) 803-2980 Fax (703) 803-3732 Part 20:1987 Fire resistance of elements of construction Part 21:1987 Fire resistance of loadbearing elements of construction Part 22:1987 Fire resistance of non-loadbearing elements of construction Accepted Industry Practice for Industrial Duct Construction (1975) Architectural Sheet Metal Manual (1993) Part 23:1987 Contribution of components resistance of a structure Contractors Guide for Modification to Construction Contracts (1993) Part 24:1987 Fire resistance of ventilation ducts to the fire BS 5588 Energy Conservation Guidelines (1984) Part 9:1980 Fire Precautions in the design and construction of buildings BS 729: 1971 Hot dip galvanized coatings for iron and steel articles BS 1449: Steel plate, sheet and strip Part 1:1991 Carbon steel plate, sheet and strip Part 2:1983 Stainless steel plate, sheet and strip and BS.EN 10149-2: 1996 BS.EN 10149-3: 1996 BS.EN 10131: 1992 BS.EN485 Parts 1-4 BS.EN515 1993 Wrought aluminium and aluminium alloys for general engineering purposes - plate, sheet and strip BS.EN573 BS 1474:1972 Wrought aluminium and aluminium alloys and bars, tubes and sections BS.EN755 BS.EN10142: 1991 BS.EN10143: 1991 Sprayed metal coatings Protection of iron and steel by aluminium and zinc against atmospheric corrosion Protection of iron and steel against corrosion and oxidation at elevated temperatures Continuously hot-dip zinc coated mild steel strip and sheet for cold forming - technical delivery conditions Continuously hot-dip zinc coated and ironzinc alloy coated steel sheet and strip tolerances on dimensions and shade BS 3533: 1981 Glossary of terms relating to thermal insulation BS.EN.ISO: 1479 Self-tapping screws and metallic drive screws BS.EN.ISO: 7049: 1994 BS 4800:1989 Paint colours for building purposes BS 4848: Hot rolled structural steel sections Part4: 1972 Fibrous Glass Duct Construction Standards (1992) Fire, Smoke & Radiation Damper Install Guide for HVAC Systems (1992) Guide to Steel Stack (1995) HVAC Air Duct Leakage Test Manual (1985) HVAC Commissioning Manual (1994) HVAC Duct Construction Standards-Metal & Flexible (1995) Addendum No I (Nov 1997) HVAC Duct Systems Inspection Guide (1989) HVAC Systems-Application (1986) HVAC Systems-Duct Design (1990) HVAC Systems-Testing, Adjusting & Balancing (1993) Indoor Air Quality Manual (1993) Managers' Guide for Welding (1993) Rectangular Industrial Duct Construction Standards (1980) Round Industrial Duct Construction Standards (1977) Seismic Restraint Manual (1991) (w/ Appendix E, 1993) Parts 3-6 1994 Energy Recovery Equipment & Systems (1991) Kitchen Equipment Fabrication Guidelines (1990) Parts 1-4 BS.EN22063: Ducted Electric Heat Guide for Air Handling Systems (1994) Equal and unequal angles BS 5422:1990 Specification for the use of thermal insulating materials BS 5720: 1979 Code of practice for mechanical ventilating and air conditioning in buildings BS 5970: 1992 Code of practice for thermal insulation of pipework SMACNA Master Index of Technical Publications (1995) Thermoplastic Duct (PVC) Construction Manual (1994) DEPARTMENT OF THE ENVIRONMENT (Publications Centre) H.M Stationery Office, 51 Nine Elms Lane, London SW8 5DR M & E No.1 1972 Electrical installations in buildings (New Edition) M & E No.3 1988 Heating, hot and cold water, steam and gas installations for buildings M & E No.4 1970 Central heating and hot and cold water installations for dwellings M & E No.1001971 Mechanical ventilation for buildings BRITISH STEEL PLC Market Communications Dept British Steel PLC Strip Products P.O Box 10 Newport South Wales NP9 OXN (Telephone 01633 290022) (Fax 01633 464087) Publication: Edge protection by zinc 96 ASSOCIATION FOR SPECIALIST FIRE PROTECTION Association House 235 Ash Road Aldershot Hampshire GU 12 4DD Telephone 01252 21322 Fax 01252 333901 Publications Fire Rated and Smoke Outlet Ductwork: An Industry Guide to Design and Installation HEALTH AND SAFETY EXECUTIVE Rose Court Southwark Bridge London SE1 9HS Telephone 0171-717 6000 APPENDIX P - CONVERSION TABLES Sheet thicknesses 97 98 NOTES 99 NOTES 100 101