DW/1 54

166683

A

Heating and Ventilating

Contractors' Association

Specification

Ductwork r

J DI WI 54 Specification for Plastics Ductwork

Specification for Plastics

ACKNOWLEDGEMENTS The HVCA records its appreciation and thanks to the many people and organisations who gave advice and information during the preparation of this specification, and in particular to those members of the drafting panel who contributed their time, experience and knowledge.

DW/154 DRAFTING PANEL Graham Handley (Chairman) Mel Clarke Bernard Coates John Howes Melvyn Sargent Keith Elphick (Drafting Panel Secretary)

Gareth Keller (Ductwork Group Secretary)

Heating and Ventilating Contractors' Association

Esca House 34 Palace Court London W2 4JG

Tel: 020-7313 4900 Fax: 020-7727 9268

e-mail: contact@hvca.org.uk website: www hvca.org.uk

DW/1 54 First Edition 2000 2000 HVCA ISBN: 0-903783-31-2 1

(yf)

Page blank in original

DM154 Spec jflcation for Plastics Ductwork

FORE WORD

David Summerfield, President Heating and Ventilating Contractors' Association

D uring the years which have passed since DWI151 was first published 1974, it has taken its rightful place as the industry standard by which the manufacture and installation of plastics ductwork can be judged. However, advances in both plastics technology and good working practices during recent years have determined the necessity for a revised specification.

Accordingly, the HVCA Ductwork Group, Technical Sub-Committee, invited members of specialist plastic ductwork manufacturers and installers to form a Drafting Panel, for the purpose of producing a radically revised specification incorporating the latest working practices and setting new standards of quality which our 21st Century clients are entitled to expect.

In drawing up this new specification, the drafting panel has tried wherever possible, to use the layout and terminology of the widely acclaimed DW/144, thereby making reference easier for all concerned. During the drafting process, the panel has consulted with specialist material manufacturers, individuals and organisations throughout the industry in order to ensure that, as far as possible, all standards reflect 'up to the minute' knowledge and best practices.

I firmly believe that this effort has resulted in a new specification that clearly demonstrates the high standards of workmanship and professionalism found within the ductwork industry and I take this opportunity of thanking all those who have contributed to its production.

David Summerfield, President Heating and Ventilating Contractors' Association

3

Dm154 Spec jfication for Plastics Ductwork

CONTENTS Page

1

2 3 4

5 6 7 8

9

4

Foreword 3 PART ONE - TECHNICAL INFORMATION TO BE PROVIDED BY THE DESIGNER Introduction 6 Standards 6 Components 6 Particular requirements 6 PART TWO - STANDARDS Application 8 Ductwork classification and Air leakage 8 Materials 9 Ductwork construction and Joint sealing 9 PART THREE - RECTANGULAR DUCTS Rectangular duct sizes 11

10 Construction 11_ 10.1 General 11_ 10.2 Longitudinal seams 11_ 10.3 Sheet jointing seams 11 10.4 Socket and spigot joints 11 10.5 Flanged joints 11 10.6 Expansion joints 12 10.7 Stiffeners 12

11 Fittings 12 11.1 Standardisation of fittings 12 11 .2 Stiffeners 12 11 .3 Splitters 12 11 .4 Turning vanes 12 11.5 Branches 12 11.6 Change shapes 12 PART FOUR - CIRCULAR DUCTS

12 Standard sizes 16 13 Construction 16

13.1 General 16 13.2 Sheet jointing seams 16 13.3 Socket and spigot joints 16 13.4 Flanged joints 16 13.5 Stiffeners 17 13.6 Expansion joints 17 PART FIVE - HANGERS AND SUPPORTS

14 General 19 PART SIX - GENERAL

15 Access I Inspection openings 22 16 Regulating dampers 22 17 Fire dampers and Intumescent sleeves 24 18 Flexible I Expansion joint connections 24 19 Protective finishes 27 20 Connections to building openings 27 21 Discharge I Exhaust terminal 27 22 Thermal insulation 28 23 Fire retardant finishes on plastic ductwork 28 24 Reinforcement of ducts with GRP laminate 28 25 Standard component drawings and abbreviations 31

] D/W1 54 Spec j/ication for Plastics Ductwork .

PART SEVEN - APPENDICES Appendix A Air leakage from ductwork 49 Appendix B Guidance notes for the Transport, Handling and Storage of ductwork 54 Appendix C Fire retardant finishes 55 Appendix D Guidance notes for Inspection, Servicing and Cleaning access

openings 56 Appendix E Bibliography 58 Appendix F Conversion tables 60

Table LIST OF TABLES PART TWO - STANDARDS

1 Ductwork classification and Air leakage limits 8 PART THREE - RECTANGULAR DUCTS

2 Minimum constructional requirements Rectangular Un-reinforced UPVC and PP 13 3 Fastening centres Rectangular duct flange joints 13

PART FOUR - CIRCULAR DUCTS 4 Standard sizes 16 5 Fastening centres Circular duct Flange joints 17 6 Minimum constructional requirements Circular Un-reinforced UPVC 18 7 Minimum constructional requirements Circular Un-reinforced PPS and PP 18

PART FIVE - HANGERS AND SUPPORTS 8 Hangers and Supports Rectangular Horizontal Ducts 19 9 Hangers and Supports Circular Horizontal Ducts 19

PART SIX - GENERAL 10 Minimum constructional requirements Rectangular GRP Reinforced ducts 30 11 Minimum constructional requirements Circular GRP Reinforced ducts 30 12 Standard Abbreviations 47

PART SEVEN - APPENDICES 13 Air leakage rates 50 14 Access requirements for inspection, servicing and cleaning 57

LIST OF ILLUSTRATIONS Fig. PART THREE - RECTANGULAR DUCTS 1-4 Cross joints 14 5-6 Stiffeners 14 7 Tie rod assembly 14 8 Hard and Easy bends 14 9 Turning vanes 15

PART FOUR - CIRCULAR DUCTS 10-12 Cross joints 17 13 Stiffeners 17

PART FIVE - HANGERS AND SUPPORTS 14-16 Support bearers 20 17-18 Vertical ducts supports 20 19-22 Arrangement of bearers and hangers 21

PART SIX - GENERAL 23-25 Expansion joints 25 26-28 Flexible connections 26 29-33 GRP reinforced Cross joints and Stiffeners 31 34 Linear Thermal Expansion 34 35 Typical Design Stress 35 36-77 Standard component drawings Rectangular 33 78-105 Standard component drawings Circular 40 106 -115 Standard component drawings Plant/Equipment/Miscellaneous 46

PART SEVEN - APPENDICES 116 Permitted leakage at various pressures 52 Example of a completed test sheet 53

5

D1W154 Spec jfication for Plastics Ductwork

PART I Technical information to be provided by the designer to the plastics ductwork contractor 1 INTRODUCTION 1 .1 This specification relates to the manufacture

and installation of rectangular and circular ductwork constructed from plastics. The selection of construction methods is at the discretion of the manufacturer to conform with the performance requirements of the specified ductwork classification. Sections 2-4 below define the information to be provided by the designer.

2 STANDARDS

2.1 Pressure classification (Table 1)

2.2 Leakage classification (Table 1)

2.3 Positive and Negative pressures (Table])

2.4 Materials (Part 2 Section 7) 2.5 Any special system requirements 3 COMPONENTS

3.1 Access and drainage points Number and location of access doors and drainage points.

3.2 Regulating dampers Specification, location and mode of operation of all regulating dampers.

3.3 Fire stops Stops to meet the requirements of the Authority directly responsible for fire protection.

3.4 Flexible joint connections Specification and location of any flexible connections e.g. plant or building expansion joints.

4 PARTICULAR REQUIREMENTS

4.2 Environmental Environmental conditions, surrounding the ductwork.

4.1 Plastics material Type of plastics material from which the ductwork is to be manufactured, and details of ductwork to special requirements not within this specification.

inside and

4.3 Airflow Design airflow volume for all main ducts, branches and air terminals.

4.4 Pressure/velocities Design air velocities and pressures for all main ducts, principal branches and terminals.

4.5 External thermal/acoustic insulation The extent and type of insulation to be provided by others should be stated, including full specification for application and installation.

4.6 Spark testing If spark testing is required, the designer shall identify land marks in the contract programme for testing to be undertaken i.e. manufacture! installation, commissioning.

4.7 Air leakage testing The extent of any air leakage testing if required. While it shall be mandatory for high- pressure ductwork (as defined in this specification) to be tested for air leakage in accordance with the procedure set out in DW/143, "A Practical Guide to Ductwork Leakage Testing", no such testing of low-or medium-pressure ductwork is required.

4.8 Identification Details of colour coding or identification, if required. For further information see HVCA publication DW!144 Appendix B.

4.9 Solvents/fumes Details of design criteria used or adopted to avoid the trapping and discharge of liquids, solvent fumes or gases.

6

I D!W154 Specflcation for Plastics Ductwork

4.10 Protective finishes (Part 6 Section 19) 4.17 Reference to designer Details and specification of any protective In consideration of the foregoing, reference is finishes, also made to the designer in the following

clauses:- 4.11 Fire retardant finishes (Part 6 Section 23)

The extent and limits of protection for any fire Clause Page retardant finishes on plastic ductwork. 5.2 8 (Specific references must be defined). 5.3 8

10.6 12 4.12 Controls/sensing equipment 10.7.2 12

Details of positions and fixing configuration of 11.1 12 all sensors and test points to suit specialist 13.1 16 control and sensing equipment. 13.5.2 17

13.6 17 4.13 Special supports (Part 5 Section 14) 14.1 19

Details of any spanning, primary secondary 14.4 19 steelwork or special support requirements not 14.5 19 specifically covered by Section 14. 14.7 20

15.2 22 4.14 Attachment to building structure (Part 6 16.1 22

Section 20) 16.3.1 23 Specific requirements for the junction of 16.3.4 23 ductwork and associated components to 17.1 24 openings should be detailed and specified with 17.3 24 the limits of responsibility defined. 17.4 24

18.1 24 The design and provision of penetrations and 18.2 27 associated framings are outside the scope of 19.1 27 this specification. 21.1 27

22.2 28 4.15 Ductwork layout drawing 22.3 28

Details of any special requirements relating to 23.1 28 CAD, scales, etc. It is common practice and 25.2 31 cost effective for ductwork manufacturers to Appendix A 49 utilise their approved ductwork layout Appendix B 54 drawings as a basis of their manufacturing Appendix C 55 installation information by adding the Appendix D 56 necessary details to the same drawing. Scales of 1:50 or smaller may preclude this practice, therefore, larger scales might be more appropriate. The final choice of manufacturing/ installation scales shall be left to the ductwork contractor.

4.16 Other requirements Details of any requirements for the ductwork not in accordance with the provisions of this specification, including any modified construction required to conform with any requirements concerning external ductwork (See 5.3) or to meet the regulations of a local authority or other controlling body.

7

D/W154 Spec jfication for Plastics Ductwork

PART 2 Standards 5 APPLICATION

5.1 This specification sets out minimum requirements for the manufacture and installation of ductwork for commercial and industrial fume extraction and exhaust systems, made from any of the materials listed in Section 7 and being within the limits of size and/or material thickness specified in the relevant tables. Normal ambient operating temperatures are assumed within the pressure/velocity limits and the limits of air leakage for the various pressure classes prescribed in Table 1.

5.2 This specification is intended to apply to ductwork handling fume-laden air which are polluted or is otherwise exceptional in respect of temperature or humidity (including saturated air) for ductwork where the external surfaces are exposed to a hostile environment. The design, construction, installation, supports and finishes in such cases should be given special consideration by the designer in relation to the particular requirements of each application.

5.3 This specification is suitable for ductwork exposed to external atmosphere. The designer will need to give specific details of any special finishes/construction (See Section 19).

5.4 This specification is based on duct operating environments of not less than -10C and for: UPVC (non GRP reinforced) not exceeding 40C UPVC reinforced with GRP not exceeding 60C PPS and PP not exceeding 60C FBPP reinforced with GRP not exceeding 70C. Systems required to operate at temperatures outside those detailed above, although outside of the scope of this specification are not precluded, but the ductwork should be designed from first principles having regard for the physical, mechanical and chemical properties of the material. It must be noted that the corrosive resistance of all the above materials will decrease at temperatures approaching 5C to 10C below the parent materials heat distortion point. Further guidance on temperature effects is provided in 'Fig. 34 Linear Thermal Expansion' and 'Fig. 35 Typical Design Stresses for UPVC and PP'.

6 DUCTWORK CLASSIFICATION AND AIR LEAKAGE

6.1 Classification and air leakage limits Ductwork classification and air leakage limits are set out in Table 1.

6.2 Compatibility with CEN The leakage factors used in Table 1 for Classes A, B and C are the same as those for the classes similarly designated in the CEN Document Pr EN 12237/Pr EN 1507.

Table 1: Ductwork Classification and Air Leakage Limits (Reproduced from DW/144)

Where p is the differential, pressure in pascals. Note: *This specification DW/1 54 only covers construction up to 1500 Pa

8

Air leakage limits litres per second per square metre of duct surface area

5

0.027 x p65 0.009 x p65 0.003 x p65

Static pressure limit

Positive Negative 2 3

Duct pressure class

1

Low-pressure Class A Medium-pressure Class B High-pressure Class C

Maximum air velocity

4 Pa Pa rn/s 500 500 10

1000 750 20 *2000 750 40

] DM1154 Specification for Plastics Ductwork 6.3 Leakage at various pressures and other

relationships Applying the limits specified in Table 1. Appendix A (Table 13) sets out the permitted leakage at each of a series of pressures, up to a maximum for each class. Included in that Appendix is a graphical presentation of the pressure/leakage relationship.

DW/143 'A Practical Guide to Ductwork Leakage Testing', provides details of the basis for the leakage limits specified in Table 1.

6.4 Air leakage testing Air leakage testing of low and medium pressure ductwork is not mandatory under this specification. Air leakage testing of high pressure ductwork is mandatory under this specification and for details of testing procedure refer to DW/143 'A Practical Guide to Ductwork Leakage Testing'.

7 MATERIALS

7.1 Application This specification applies to ductwork constructed from materials as defined below, or equal. Minimum material thickness is to be taken as a nominal thickness as Tables 2,6,7, 10 & 11. All UPVC materials used shall be low flammability selfextinguishing compatible and UV stable with pigment colour to RAL 7011 and DIN 4802 Bi.

7.2 Types The materials covered by this specification are abbreviated herein as follows:- (UPVC) Unplasticised polyvinyl chloride (PPS) Self extinguishing polypropylene (PP) Polypropylene (GRP) Glass reinforced plastic (FOAM) Rigid polyurethane self

extinguishing foam (FBPP) Fabric backed polypropylene sheet

7.3 UPVC (Forms available) 7.3.1 Extruded sheet in thickness 3 mm to

12 mm (Dimensional tolerances to DIN 7748).

7.3.2 V series tube in sizes 110 mm to 1,400 mm dia. and fittings in sizes

110 mm to 600 mm dia. (Dimensional tolerances to DIN 8062).

7.4 PPS (Forms available) 7.4.1 Extruded sheet in thickness 3 nim to

12 mm (Dimensional tolerances to DIN 53479)

7.4.2 V series tube in sizes 110 mm to 630 mm dia. and fittings in size 110 mm to 400 mm dia. (Dimensional tolerances DIN 53479).

7.4.3 All PPS material used shall be compatible and comply with DIN 4102 part B and BS 476 part 7 class 4. PPS material should not be used for external applications without suitable protection (See Part 6 section 19).

7.4.4 It should be noted that PP is not fully compatible with PPS.

7.5 FBPP (Forms available) 7.5.1 Sheet in thickness 3 mm to 9 mm.

7.5.2 Continuous roll form in thickness 2 mm to 4 mm.

7.5.3 This particular material is specifically designed to be externally reinforced with GRP (See Section 24)

7.6 UPVC/GRP This is a form of composite laminate used where improved mechanical strength UV stabilisation or fire retardence is required.

7.7 UPVC/FOAMJGRP FBPP/FOAMJGRP This is a form of composite laminate used where insulation and/or support is required for special applications.

8 DUCTWORK CONSTRUCTION AND JOINT SEALING

8.1 Ductwork construction The selection of longitudinal cross joint and stiffener types within the criteria laid down in Parts 3 & 4 shall be used as a minimum standard.

9

0/WI 54 Spec jfication for Plastics Ductwork

8.2 Joint sealing and sealants.

8.2.1 General The integrity of the ductwork depends on the successful application of the correct jointing method.

8.2.2 Solvent cementing Solvent cementing is a satisfactory method of jointing circular UPVC socket and spigot or sleeve joints, as certain solvent based cements homo- geneously bond the PVC surfaces providing suitable joints. Solvent cementing is not practicable with PP, because of its high resistance to solvents. The procedure recommended by the cement manufacturer should be followed, but the following points are important.

8.2.2.1 Clearance between socket and spigot must be minimal because of the limited gap filling prop- erties of the cement.

8.2.2.2 Inside edges of sockets and outside edges of spigots should be slightly cham- fered and thoroughly cleaned.

8.2.2.3 Mating surfaces should be cleaned using a proprietary solvent cleaner to remove grease and slightly etch the surface.

8.2.2.4 The cement should be applied as quickly as possible to the socket and spigot over the full area of the mating surface; care should be taken to avoid the use of excessive cement.

8.2.2.5 The positioning of the joint must be achieved immed- iately after the cement is applied, and surplus cement removed.

8.2.2.6 The joint must be held in position for at least 5 minutes. A jig should be used if necessary to ensure that no twisting force is applied to the joint during the period.

NOTE: SOLVENT CEMENT JOINTING METHODS ARE NOT RECOM- MENDED FOR RECTANGULAR DUCT SECTIONS. IN ALL CASES, SEALANT MAT- ERIALS MUST BE APPLIED STRICTLY IN ACCORDANCE WITH THE MANUFACTURERS INSTRUCTIONS AND COSHH ASSESSMENT.

8.2.3 Hot air welding UPVC and PP may be welded by using the hot gas/filler rod method described below.

8.2.3.1 The welding gas can be nitrogen or compressed air, and shall be filtered free from suspended water, oil vapour and particulate

8.2.3.2 The filler rods shall be made from material to or compatible with the mat- erial being welded.

8.2.3.3 Butt weld joints shall be bevelled to an included angle of 600 to 90, and where possible welds shall be fully penetrated from both sides of the work.

8.2.2.7 Once made the joint should not be exposed to undue force for eight hours. The full strength of the joint is not achieved in less than twenty-four hours.

matter.

10

J D1W154 Specflcation for Plastics Ductwork

8.2.3.4 The joint faces and the filler rod surfaces must be clean and grease free and preferably roughened be- fore welding. In particular, any deposited filler rod that is charred must be scraped away bef ore additional runs are added.

8.2.3.5 The numbers of runs of filler rod shall be sufficient to give a thickness of cross section of the weld at least equal to the thickness of the sheet.

8.2.3.6 Where high frequency spark testing is specified, this shall be undertaken in accordance with the weld- ing instruction handbook.

Note: A full description of welding methods is given in the Welding Institute handbook entitled 'Data on Welding of Thermoplastics'. Relevant BS & CEN Standards are prEN 128 14-1 & 2, prEN 13067 and prEN 13100-1.

8.2.4 Completion of composite laminate joints Following solvent cementing or hot air welding of joints, completion of any specified external laminate shall be carried out to maintain the integrity of the construction. (See 8.2.2.7).

8.2.5 Gaskets These can be fabricated from various materials in the form of a pre-formed roll, sheet or strip, applied between opposing faces of flanged cross joints. It is advisable to select material recommended by the gasket manufacturer for the specific application intended.

PART 3 Rectangular Ducts

RECTANGULAR DUCT SIZES

This specification covers duct sizes up to a maximum longer side of 1500 mm. Duct sizes with an aspect ratio greater than 4:1 are not recommended. Although they offer no problems of construction, they increase frictional resistance and the possibility of noise.

10 CONSTRUCTION

10.1 General The minimum constructional requirements for UPVC and PP/PPS un-reinforced, are shown in Table 2.

10.2 Longitudinal seams Longitudinal seams should not be located at corners or in the underside of the duct.

10.3 Sheet jointing seams Seams shall be joined by continuous filler rod hot air welding or by fusion welding only, other forms of jointing are not acceptable.

10.4 Socket and spigot joints Socket and spigot joints shall be formed by purpose made double socket pieces 100 mm' long and of the same thickness material as the duct, welded into position on each standard length of duct, forming 50 mm deep sockets prepared and ready for final jointing on site with filler rod of the same formulation used for prefabrication. (See Table 2)

10.5 Flanged joints 10.5.1 Flanges

Fabricated flanges shall be constructed using miniumum of 9 mm thick, by 50 mm wide material of matching formulation depending on duct size as shown in Table 2. The flange shall be mounted true and square to the duct surfaces and welded on both sides as 10.3 and Figs. 3 & 4. Alternative construction may be

9 9.1

11

D1W154 Spec jfication for Plastics Ductwork

PART 4 Circular Ducts 12 CIRCULAR DUCT SIZES

The duct sizes in Table 4 have been selected from the ISO and CEN standard ranges as the preferred sizes.

Table 4: Circular ducts standard extruded tube sizes

Note: The above sizes are subject to normal manufacturing tolerances. Other sizes may be available in varying wall thicknesses and subject to test and operational pressure.

13 CONSTRUCTION

13.1 General This specification covers duct sizes up to a maximum diameter of 1500 mm. The minimum constructional requirements for UPVC & PP/PPS un-reinforced ducts shall be as Tables 6 & 7.

16

For smaller diameters, preformed fittings are available, otherwise fittings are fabricated from segments of duct or sheet welded together.

The terminology and description of circular duct fittings as set out in Section 25 are recommended for adoption as standard

practice, to provide common terms of reference for designers, quantity surveyors and ductwork contractors, and those using computers in ductwork design and fabrication. The requirements for circular duct fittings apply throughout the size ranges covered in this specification.

13.2 Sheet jointing seams Seams shall be joined either by continuous filler rod hot air welding or by fusion welding, Other forms of jointing are not acceptable.

13.3 Socket and spigot joints Socket and spigot joints shall be formed by purpose made double socket pieces 100 mm long and of the same thickness material as the duct, welded into position on each standard length of duct, forming 50 mm deep sockets prepared and ready for final jointing on site with PVC adhesive and/or filler rod of the same formulation used for fabrication.

13.4 Flanged joints 13.4.1 Flanges

Fabricated flanges shall be con- structed using minimum of 9 mm thick, by 50 mm wide material of matching formulation depending on duct size as shown in Tables 6 & 7. The flange shall be mounted true and square to the duct surfaces and welded on both sides as 10.3 and Fig. 12.

13.4.2 Drillings Drillings shall be placed to permit clearance to the external casing and any reinforcement of the ductwork.

13.4.3 Fastenings For normal application bright zinc plated bolts, nuts and washers shall be used in sizes and pitch centres shown in Table 5. Where special conditions prevail consideration of other material finishes such as stainless steel bolts, nuts and washers shall be used. In all cases, gasket materials as Section 8.2.5 shall be used.

Extruded tube ISO Standard Sizes (Nominal Diameter)

Wall Wall Thickness Thickness

mm mm mm mm 110 2.2 500 4.0 160 2.5 600 5.0 200 2.5 630 6.0 225 2.5 700 6.0 250 2.5 800 6.3 280 2.3 900 7.0 315 2.3 1000 8.0 355 2.5 1250 10.4 400 3.2 1400 10.8 450 3.5

J D1W154 Specflcation for Plastics Ductwork

restrictions, splitters shall be provided. Taper Transformation pieces from circular to square pieces, reducers and transformation pieces or rectangular shall be made as long as shall be manufactured from the thickness of possible and the angle shall be not more than material specified for the larger size duct. 22.5 (Fig. 55).

Table 2: Minimum constructional requirements rectangular un-reinforced UPVC and PP

Longer Side Minimum Joints Stiffeners Maximum spacing Sheet between

Thickness Joints/Stiffeners 1000 Pa 1500 Pa

1 2 3 4 5 6 mm mm mm mm mm

Up to 400 3 socket & spigot or flanged

as Figs. 1, 2, 3 401 to 600 4.5 flanged 50 x 9 flat 1200 800

50 x 9 flat welded both sides as Fig. 3 as Fig. 5

601 to 1000 4.5 flanged 50 x 9 flat 800 600 50 x 9 flat welded both sides as Fig. 3 as Fig. 5

1001 to 1500 6 flanged 75 x 9 flat 600 600 75 x 9 flat welded both sides as Fig. 3 as Fig. 5

or or 70 x 70 x 9 angle 50 x 50 x 5 angle

as Fig. 4 welded both sides as Fig. 6

Note: For constructional operating temperature limits refer to Part 2 Clause 5.4

Table 3: Fastening centres rectangular duct flange joints

Longer Pitch Bolt Size Side max

1 2 3 mm mm mm

Up to 400 100 8 with washers 401-600 100 10 with washers

601-1000 100 10 with washers 1001-1500 100 10 with oversized

washers

13

D/W154 Spec(fication for Plastics Ductwork

Cross joints rectangular ducts

Easy

Fig. 1 Socket and spigot joint (UPVC and PP) Continuous weld joint on Site Continuous weld

Fig. 3 Flange joint (UPVC and PP)

Gasket

bolt Continuous weld

TTT Fig. 2 Socket and spigot joint (UPVC only) Solvent cement Continuous weld or

cement

Fig. 4 Flange joint (UPVC and PP)

Continuous weld

Stiffeners rectangular ducts Fig.5 Flat

flat continuously welded

Fig. 6 Angle

angle continuously welded

1/

Tie rod assembly

J DM154 Spec jfication for Plastics Ductwork

15

Dm154 Spec jfication for Plastics Ductwork

utilised for attachment to plant or other equipment.

10.52 Drillings Drillings shall be placed to permit clearance to the external casing and any reinforcement of the ductwork, for the application of fastenings.

10.5.3 Fastenings For normal application bright zinc plated bolts, nuts and washers shall be used in sizes and pitch centres shown in Table 3. Where special conditions prevail consideration of other material finishes such as stainless steel bolts, nuts and washers may be used. In all cases, gasket materials as Section 8.2.5 shall be used.

10.6 Expansion joints Where the configuration of the ductwork does not provide for movement due to temperature change, or where such movement is restricted by branches or attachments, expansion joints should be specified by the designer. (See Section 18 Flexible/Expansion joint connections).

It is the responsibility of the designer to identify the positions of any necessary expansion joints based upon design parameters for the individual systems. (See Figs 23 to 25, 34 & 35).

Design Note : Examples of expansion joints shown in Figs. 23 to 25 are not suitable for movement exceeding 30 mm.

10.7 Stiffeners

10.7.2 Internal stiffeners The use of internal stiffening or bracing shall be acceptable if deemed necessary and approved by the designer. (See Fig. 7).

11 FITTINGS

1 1.1 Standardisation of fittings The terminology and descriptions of rectangular duct fittings as set out in Section 25 are recommended for adoption as standard practice to provide common terms of reference for designers, quantity surveyors and ductwork contractors, and for those using computers in ductwork design and fabrication.

Bends are designated as 'hard' or 'easy', and these terms as used herein have the following meanings:

Hard signifies rotation in the plane of the longer side of the cross section.

Easy signifies rotation in the plane of the shorter side of the cross section.

An example illustrating these terms is given in Fig. 8.

Fittings are fabricated by cutting and welding sheet.

1 1 .2 Stiffeners Shall be as 10.7 and Tables 2 & 10.

1 1 .3 Splitters Shall be as shown in Fig. 41 and welded as 10.3.

1 1.4 Turning vanes Where square bends are required turning vanes as shown in Fig. 9 shall be fitted.

11.5 Branches When fitting branch ducts to a main duct, care should be taken to ensure that the rigidity of the duct panel is maintained in terms of the stiffening criteria.

Change shapes Where a change shape is necessary to accommodate the duct and the cross-sectional area is to be maintained, the slope shall not exceed 22.5 on any side (See Figs. 52 to 56). Where a change in shape includes a local reduction in duct cross-sectional area, the slope should not exceed 15 on any side and the reduction in area should not exceed 20%. Where steeper angles are necessary due to site

10.7.1 External stiffeners Shall be fitted as specified in Tables 2 1 1 .6 & loandFigs.5&6.

12

J Dm1 54 Specflcation for Plastics Ductwork

13.5 Stiffeners

13.5.1 External stiffeners Shall be fitted as specified in Tables 6, 7 & 11 and Fig. 13.

13.5.2 Internal stiffeners The use of internal stiffening or bracing shall be acceptable if deemed necessary and approved by the designer.

13.6 Expansion joints Where the configuration of the ductwork does not provide for movement due to temperature

Cross joints circular ducts

change, or where such movement is restricted by branches or attachments, expansion joints should be fitted (See Section 18 Flexible! Expansion joint connections). It is the responsibility of the designer to identify the position of any necessary expansion joints based upon design parameters for the individual systems (See Figs. 23, 24, 25, 34 & 35). Design Note : Examples of expansion joints shown are not suitable for movement exceeding 30 mm.

Continuous weld

C''iiti

Fastening centres circular duct flange joints

Fig. 10 Socket and spigot joint (UPVC and PP) Continuous weld joint on weld

Fig. 12 Flange joint (UPVC and PP)

Gasket

Fig. 11 Socket and spigot joint (UPVC only) Continuous weld or Solvent cement Solvent cement

Table 5: Stiffeners circular ducts Fig.13 Flat

flat

continuously welded Diameter Pitch Bolt Size max

1 2* 3 mm mm mm

Up to 600 100 8 with washers 601-1000 100 10 with washers 1001-1500 100 10 with oversized

washers *Minimum of four fixings

17

rii;ation for Plastics Ductwork Table 6: Minimum constructional requirements circular un-reinforced UPVC

Diameter Minimum Joints Stiffeners Maximum spacing Sheet between

Thickness Joints/Stiffeners 1000 Pa 1500 Pa

1 2 3 4 5 6 mm mm mm mm mm

110 to 600 3 socket & spigot as Figs. 10& 11

or flanged as Fig. 12

601 to 1000 4.5 socket & spigot 50 x 9 flat 2400 2400 as Figs. 10 & 11 welded both sides

or flanged as Fig. 13 as Fig. 12

1001 to 1500 6 flanged 75 x 9 flat 1200 1200 as Fig. 12 welded both sides

__________ ____ __________

as_Fig. 13

Applies to Tables 6 and 7,

Note: 1. For constructional operating temperature limits refer to Part 2 clause 5.4. 2. To allow for consideration of extruded sections or fabricated components the material thickness is shown as nominal.

Table 7: Minimum constructional requirements circular un-reinforced PPS and PP Diameter Minimum Joints Stiffeners Maximum spacing

Sheet between Thickness Joints/Stiffeners

1000 Pa 1500 Pa 1 2 3 4 5 6

mm mm mm mm mm 110 to 500 3 socket & spigot

as Fig. 10 or flanged as Fig. 12

501 to 750 4.5 socket & spigot as Fig. 10 or flanged as Fig. 12

751 to 1000 6 flanged 50 x 9 flat 1200 1200 as Fig. 12 welded both sides

as Fig. 13 1001 to 1250 6 flanged 75 x 9 flat 800 800

as Fig. 12 welded both sides as Fig. 13

1251 to 1500 6 flanged 75 x 9 flat 600 600 as Fig. 12 welded both sides

as Fig. 13

18

J D!W154 Speqflcation for Plastics Ductwork

PART 5 Hangers and Supports 14 GENERAL

14.1 Supports are an essential part of the ductwork system, and their supply and installation are normally the responsibility of the ductwork contractor. The principles are as HVCA publication DW/144 Part 6, Section 19 and should be read in conjunction with this document.

Design Note : Designers may specify specific requirements which will supersede guidance given in DW/144.

14.2 Rectangular ducts Table 8 gives the minimum requirements for hangers and supports for un-reinforced ductwork.

14.3 Circular ducts Table 9 gives the minimum requirements for hangers and supports for un-reinforced ductwork.

14.4 Vertical ducts The design of supports for vertical ducts is dictated by site conditions and where practical, ducts should be supported at 4000 mm intervals or where they pass through a floor (but never exceeding 4500 mm) see Figs. 17 & 18.

14.5 External ducts Where ducts are external to buildings and may be subject to wind loading, support should be placed so as to restrain side thrust and should allow axial movement as necessary. It is the responsibility of the designer to calculate the effect of the particular prevailing conditions and to define any special support requirements.

14.6 Expansion joints Supports shall be designed to permit axial movement only and shall be provided on either side of expansion joints.

Table 8: Hangers and Supports rectangular horizontal ducts Longer Side Hanger Bearer Maximum spacing

Drop Roll Formed Rod Channel

1 2 3 4 5 Fig 15 Figs 14, 15, 16&21

mm mm mm mm mm

Up to 400 8 25 x 25 x 1.6 40 x 20 x 1.5 2400 401 to 600 10 40 x 20 x 1.5 40 x 20 x 1.5 2400 601 to 1000 10 40 x 20 x 1.5 40 x 20 x 1.5 2400 1001 to 1500 10 40 x 40 x 1.5 40 x 40 x 1.5 2400

Table 9: Hangers and Supports circular horizontal ducts

Longer Side Hanger Split Clips Maximum spacing Drop Roll Formed and Wrap-round Rod Channel Hanger

1 2 3 4 5 Fig. 15 Figs. 19, 20 & 22

mm mm mm mm mm

Up to 355 8 25 x 25 x 1.5 40 x 3 2400 356 to 600 10 40x20x1.5 40x5 2400 601 to 1000 10 40 x 20 x 1.5 50 x 5 2400 1001 to 1500 10 40x 40 x 1.5 70x6 2400

19

I 0/WI 54 Specfica1ion for Plastics Ductwork I

14.7 Protection Unless otherwise stated all supports shall be manufactured in material as specified in this

20

specification. Any special coating/paint finishes for protection against hostile environments shall be advised by the designer.

SUPPORT BEARERS

Fig. 14 Rolled steel angle

>-

Fig. 16 Inverted profile channel (alternatives) Fig. 15

Profile channel (alternatives)

Fig. 18 Vertical circular ducts Fig. 17 Vertical rectangular ducts

The support bearer, which, depending on duct/structural opening size, could be either channel or angle section, may be utilised in any of the following arrangements:-

a) To support the underside of a flat bar clip in halves (circular) b) To support the underside of either the stiffening frame of the flanged joint of any duct

section c) To support either a stiffening frame or a flanged joint below using drop rods/studding.

jDIW154Specfication for Plastics Ductwork

Arrangement of bearers and hangers (to be read in conjunction with Tables 8 & 9

which lists material sizes relative to duct sizes) KEY

Typical attachment Attachment

Limits refer to actual duct sizes insulation is additional

to structure to structure

I

jj' FlatBar I Drop rod, or Outline of

studding Insulation (if applicable)

drop rod, or studding / Alternative

\ Fig. 19 Wrap-round hanger Limit: 355 DIA

III ii .. ii 'S7

I I Rectangular I ill I I II, I III

LL

Fig. 21 Rolled or profiled bearer Limit: None

Alternative drop rod, or studding and welded boss (AJ /)1

'w-' Limit: 355 DIA Fig. 20 Flat strap hanger & split clips

y Drop rod, or studding I I

-

Fig. 22 Split clips Limit: 1500 DIA

21

ID/WI 54 Speccation for Plastics Ductwork I

PART 6 General 15 ACCESS/INSPECTION OPENINGS

15.1 General These are for inspection/servicing only. HVCA publication DW/144 Part 7 General. Section 20 sets out the requirements for access applicable to this specification.

15.2 Cleaning/maintenance Designers shall take specialist advice and then stipulate their requirements for the periodic internal cleaning/maintenance of ductwork and of the consequent need for adequate access for specialist cleaning equipment including the size, type and location/frequency of the actual access openings required.

Appendix D sets out guidance notes for the consideration of cleaning access and also makes reference to the HVCA publication TR 17 "Guide to Good Practice, Cleanliness of Ventilation Systems", which covers the subject in greater detail.

Note : A majority of installations in which plastic ductwork is used are considered to have a high operational risk potential and provision of access should address this.

16 REGULATING DAMPERS

16.1 General Balancing dampers and control dampers are elements inserted into an air distribution system, or element of an air distribution system. Balancing dampers permit modification of the air resistance of the system and consequently changing of the airflow rate. Control dampers control the airflow rate and may, in addition provide low leakage closure of the airflow.

22

The designer shall specify damper locations taking into consideration that good design practice requires a minimum of five times the diameter or width of the shortest side of uninterrupted flow between plant connections and the damper and select the damper type as

defined in 16.2 appropriate to the airflow, pressure, acoustic, temperature and corrosion characteristics.

16.1.1 Balancing damper To achieve the required distribution of air in the ductwork system at inlets and/or outlets. For this purpose, the damper blades are set and locked manually in position between fully open and fully closed.

16.1.2 Control damper To secure dynamic control of the air flow in the ductwork system. In this function, the damper will always be power actuated and may require to be modulated between fully open and fully closed, and to be capable of taking up any position between these extremes. In the fully open position, the damper should have a minimum pressure drop. In the fully closed position, it will not necessarily achieve a complete shut off.

16.2 Eypes of airflow control dampers Airflow dampers of various types are available for specific purposes as follows:

16.2.1 Single blade dampers Single-blade dampers shall consist of a single pivoted blade contained within a casing or section of ductwork. The blade shall be adjustable through a nominal 90 angle by means of a quadrant or similar operating mechanism. Where automatic control of the damper is required the spindle shall be extended to enable a powered actuator to be mounted.

Single-blade dampers shall have a maximum duct width of 400 mm and a maximum duct height of 400 mm for rectangular ducts; and for circular ducts a maximum diameter of 400 mm.

16.2.2 Multi-blade dampers Multi-blade dampers shall consist of a number of pivoted blades contained within a casing. The blades shall be

J D1W154 Spec jfication for Plastics Ductwork I

adjustable through a nominal 900 angle simultaneously by inter- connected linkage or gears, connected to a quadrant or similar operating mechanism. Where automatic control of a damper is required a spindle shall be extended to enable a powered actuator to be mounted.

There is no restriction on the size of duct in which multi-blade dampers or damper assemblies may be used. Where dampers are required for blade lengths in excess of 750 mm, the blades should be suitably reinforced or supported. No individual damper blade should exceed 200 mm in width.

16.2.3 Iris dampers Iris dampers shall consist of a number of radially interconnected blades which open or close within a casing with duct connections. The blades shall be simultaneously adjusted by a quadrant or similar operating mechanism.

Iris dampers shall be installed as specified by the manufacturer's operating and installation instructions, where the product is unidirectional with regard to airflow.

Iris dampers are available for circular ducts only in diameters up to 250 mm (it should be noted that the damper casing is approximately twice the diameter of the duct).

16.2.4 Backdraught dampers Air pressure operated uni-directional rectangular (single or multi-blade) with adapters if fitted to circular ducts.

16.2.5 Slide and blast gate dampers A damper used as a shut off facility with an external slide housing, allowing the blade configuration to be fully inserted to fully extended for maximum air flow.

16.3 Construction

16.3.1 Materials All products shall be protected against corrosion as necessary and supplied in a fully finished condition as specified by the designer.

16.3.2 Dampers used in low and medium pressure systems The following recommendations apply to dampers forming an integral part of ductwork with pressure classifications A and B air leakage limits.

The dampers shall be constructed to minimise distortion and prevent janiming in operation. The blades shall be sufficiently rigid to minimise movement when in the locked position.

The blades shall be securely fixed to the operating mechanism. All balancing dampers shall have a locking device located on the outside of the case and shall give clear indication of the actual blade position. All penetrations of the duct shall be fitted with suitable seals where necessary.

16.3.3 Dampers used in high pressure systems Regulating dampers used in ductwork systems to pressure classification C shall meet the construction require- ments specified in 16.3.1 and 16.3.2 with operating mechanisms out of the air-stream.

16.3.4 Proprietary types of damper The use of any specific type of proprietary damper shall be confirmed by the designer. In all cases, proprietary dampers shall meet the relevant requirements of this specification.

16.3.5 Damper casings Duct damper casings shall be constructed to meet the minimum

23

D1W154 Speccation for Plastics Ductwork I

leakage limits specified for the ductwork system to which they are installed.

In order to apply the square metre leakage calculation as detailed in DW/143 'A Practical Guide to Ductwork Leakage Testing', the reference casing area shall be taken as the perimeter size of the damper multiplied by the equivalent length of imetre e.g. an 800 mm x 400 mm duct damper shall have a surface area for casing leakage performance calculated as follows; {(2 x 0.8) + (2 x 0.4)) x 1

= 2.4m2 casing area

Other performance and rating test methods for dampers and valves are specified in ISO 5129 and BS/EN 1751, and are referenced below; a) Leakage past a closed damper

valve BS/EN 1751 b) Flow rate/pressure requirement

characteristics BSJEN 1751 c) Operational torque testing

BSIEN 1751 d) Thermal transfer testing

BS/EN 1751 e) Regenerated sound power levels

ISO 5129

16.4 Installation Dampers shall be installed in accordance with any relevant ISO, EN or British Standard, local building regulations and national codes of practice as well as the manufacturers' recommendations.

17 FIRE DAMPERSAND INTUMESCENT SLEEVES

17.1 General Dampers or sleeves are required on duct systems where the designer has stipulated the duct will penetrate a fire compartment. As in the majority of applications, thermoplastic ductwork is used where contaminated, corrosive or otherwise exceptional fumes are concerned, it is preferable to use fire dampers which are externally mounted i.e. of the intumescent operated crush type.

24

1 7.2 Fire rating The damper assembly should have a fire resistance rating equal to that of the fire barrier it penetrates and shall be fire tested and rated to the time/temperature curve of BS 476 Parts 20 and 22.

1 73 Intumescent sleeve At the time of writing this specification, qualified test results were available for rectangular dampers and circular dampers up to 355 mm diameter. Manufactures have indicated that they are able to provide specifications for other sizes and diameters. This information should be confirmed by the designer. Various types are available including those incorporating mechanical closing plates and those operated only by expanded intumescent media.

In all cases fire dampers and intumescent sleeves shall be supplied and installed in accordance with the manufacturers instructions and COSHH assessment.

1 7.4 Other types Fire dampers of various types are available for specific purposes, see HVCA publication DW/144. The designer should note that materials for construction should be suitable for the particular application.

IN ALL CASES, FIRE DAMPERS AND INTUMESCENT SLEEVES SHALL BE SUPPLIED AND INSTALLED IN ACCORDANCE WITH THE MANU- FACTURERS INSTRUCTIONS AND COSHH ASSESSMENT.

18 FLEXIBLE/EXPANSION JOINT CONNECTIONS

18.1 General properties The material used for flexible/expansion joints must meet the designers requirements for temperature, air pressure, fire resistance applicable to plastic duct systems, vibration and noise breakout when incorporated into a jointlconnection and shall comply with the standard of air-tightness specified for the ductwork system of which it forms part (See Figs. 23, 24, 25, 26, 27 & 28, for typical construction details).

Expansion joints

J D1W154 Spec jflcalion for Plastics Ductwork

Fig. 23 Moulded bellows type (rectangular and circular)

Fig. 24 Sleeve type (circular)

Fig. 25 Flanged sleeve (rectangular and circular)

25

Flexible sleeve

Sliding sleeve Band clip

Continuous weld

Sliding sleeve Continuous

weld UPVC AS SHOWN PP USE BACKING FLATS AS FIG. 28

ID/WI 54 Specification for Plastics Ductwork I Flexible connections

Band clip ______ Band clip * I

Fig. 26 Flexible sleeve with clips (UPVC and PP)

Flexible sleeve

Connection to plant

Fig. 27 Welded flexible sleeve (UPVC only)

Plasticised PVC sleeve continuously welded

Fig. 28 Flanged flexible connection (UPVC and PP)

26

JD/Wi 54 Specflcation for Plastics Ductwork I

18.2 Location Flexible joints are typically used at building expansion joints and fan inlets/outlets. Any others required should be indicated on the design drawings. Care should be taken to maintain alignment across joints/connections.

18.3 Length Flexible joints shall be kept as short as practicable above a minimum effective length of 50 mm. In no case shall a flexible joint exceed 250 mm in length.

18.4 Connections to rectangular ducts With flanged rectangular connections, the flexible material shall be held in place with flat plastic strips of not less than 6 mm thick attached to the flanges using suitable fixings. The more heavy weight type of flexible material may also be obtained formed into a channel section with corners fitted to give a neat air tight joint. For spigot connections the flexible material shall be held in place with flat plastic strips not less than 6 mm thick.

18.5 Connections to circular ducts With flanged circular connections the flexible material shall be held in place with flat plastic backing strips or proprietary clip bands with screw or toggle fasteners.

18.6 Welded flexible connections (Rectangular and Circular) Where the parent and flexible material are from similar based products, they can be joined to the duct using the welding method described in Section 8.2.3.

19 PROTECTIVE FINISHES

19.1 Unless otherwise stated all ductwork shall be manufactured in material as specified in this specification. Any special coating/paint finishes to be provided by the ductwork contractor shall be advised by the designer.

20 CONNECTIONS TO BUILDING OPENINGS

20.1.1 Openings in brick, block or concrete walls shall have inset frames to provide a suitable means of fixing grilles, louvers, masking flanges or the flanged ends of ductwork. The inset frames shall be constructed to maintain the structural integrity of the wall and where applicable cavities shall be suitably lined.

20.1.2 Openings in dry lining partitions shall have inset frames as 20.1.1.

20.1.3 Openings in cladding walls and roofs shall have flanged sleeves/frames to provide a suitable means of fixing as 20.1.1.

20.1.4 Horizontal and vertical openings exposed to outside atmosphere shall be provided with a suitable weathering finish at the external face especially where profiled cladding is used.

20.1.5 Timber framed openings are not permitted in fire compartment barriers.

20.2 Ductwork connections to building openings shall have a flange of suitable profile to permit practical fixing to the opening frame. In selecting the profile, consideration shall be given to Tables 2 and 10 in this specification relating to duct size and rating. Gasket strip or sealant shall be applied between the flange and building opening frame.

21 DISCHARGE/EXHAUST TERMINAL

21 .1 These shall be vertical, open ended and designed to meet and comply with current regulations on contaminated flues. The designer shall ensure that the design and performance is suitable for its intended purpose. Examples of some typical tenninal designs are shown in Figs. 102, 103, 104 & 105.

20.1 Forming and finishing building openings are not the responsibility of the ductwork contractor and the notes that follow are for guidance purposes only.

27

I D1W154 Spec jfication for Plastics Ductwork I

22 THERMAL INSULATION

22.1 The provision and application of thermal insulation to ductwork is not the responsibility of the ductwork contractor.

22.2 Where ductwork is required to be pre- insulated, the specification should be agreed with the designer.

22.3 Where the temperature of the air within the duct promotes condensation on the exterior surface of the duct and cause moisture penetration through the thermal insulation, vapour sealing may be required, and in this case the most important requirement is to limit penetration of the seal.

The extent of any vapour sealing of ductwork thermal insulation and the support method to be used must be clearly specified in advance by the designer.

22.4 For detailed information on the thermal insulation of ductwork, reference should be made to BS 5422:1990 which covers the specification for thermal insulation materials on pipes, ductwork and equipment (in the temperature range 40C to +700C) and BS 5970:1992 which is a Code of Practice for Thermal Insulation of Pipework and Equipment (in the temperature range 100C to +870C).

23 FIRE RETARDANT FINISHES ON PLASTIC DUCTWORK

23.1 The designer should note that ductwork constructed to DW/154 has no tested fire rating. For information see Appendix C.

24 REINFORCEMENT OF DUCTS WITH GRP LAMINATE

24.1 General Where ductwork is required in larger sizes than are covered by Tables 2, 4, 6 & 7, or with the increased strength sometimes necessary for industrial use, external reinforcement is normally provided by application of glass fibre/resin laminate.

28

GRP systems will bond satisfactorily with standard UPVC sheet, but for PP it is

necessary to use a specially prepared sheet with a glass fabric backing incorporated during manufacture.

The detailed techniques of fabrication using GRP are outside the scope of this specification, but the following notes are offered for guidance of ductwork fabricators.

24.2 Materials 24.2.1 Quality

The laminate is made up of polyester resin complying with BS 3532 and glass fibre complying with BS 3496 or BS 3749. The nominal ratio of resin to glass fibre should be 70/30 by weight.

24.2.2 Minimum properties The laminate shall comply with the following minimum physical properties:

Tensile strength - 70 MN/rn Tensile modulus - 7 GN/m Flexural strength - 140 MN/rn Bond strength (between laminate and substrate): Not less than 7MN/m Barcol hardness: Not less than manufacturer's specification.

The GRP reinforcement reduces the expansion of the parent material, but the resultant stresses are well within the strength of the bond. However the linear thermal expansion curves shown in Figs. 34 & 35 will serve as a guide.

Surface resistivity, electrical properties and acoustical properties are similar to the relevant unreinforced materials. The fire retarding properties of GRP may be improved by the use of specialist laminating resin.

24.2.3 Forms available GRP Laminate should be built up from the separate materials, i.e., resin and glass fibre in the form of chopped strand mat or spray rovings.

D/W1 54 SpecflcaIion for Plastics Ductwork I

24.2.4 Workshop conditions Polyester resins are sensitive to temperature and the workshop should be maintained at a temperature of between 200 and 25C. High relative humidities and damp conditions should be avoided. A good rate of air change must be provided preferably by mechanical ventilation.

24.2.5 Storage of materials Resin and curing agents should be stored in dark, cool conditions, away from the working area, and in conformity with statutory require- ments for the storage of flammable liquids. Because of the limited storage life of the unmixed resin and curing agents, materials should be checked before use to ensure that they are within the manufacturer's specified shelf life (usually six months from the date of manufacture).

conditions.

24.3 Surface preparation 24.3.1 UPVC

To achieve the specified bond strength, the surface to which the GRP is applied must first be thoroughly cleaned and then etched, either by mechanical means or by the use of a suitable solvent.

24.3.2 PP with glass fabric backing To achieve the specified bond strength, the fabric backing must be thoroughly impregnated with resin.

24.4 Mixing the materials for use The resin is a three part mix, comprising base resin, hardener and accelerator. The manufacturer's specified proportions are critical and the mixing sequence specified must be meticulously followed.

The resin has a very limited life after mixing and before use. It is dependent on the characteristics and bulk of the resin, the amount of hardener, the degree and method of acceleration, and the workshop conditions.

24.5 Methods of application 24.5.1 General

The mixed resin may be applied by hand or by spray deposition. The operation must be completed within the gel time of the system and the laminate fully consolidated, to achieve the physical properties specified.

24.5.2 Hand lay-up The duct surface is coated by hand with resin, using a brush, and a mat of glass fibre worked in until full consolidation achieved. The process is repeated until the required thickness is obtained.

24.5.3 Spray deposition The duct surface is coated with resin by spray gun, with the chopped glass rovings added through a separate nozzle. The full thickness is obtained in layers, with consolidation of each layer by hand roller.

24.6 Construction 24.6.1 General

Minimum constructional require- ments are specified in Table 10 for rectangular and Table 11 for circular ducts.

24.6.2 Joints and stiffeners Figs. 29, 30, 31, 32 & 33 show cross joints and stiffeners for reinforced UPVC and FBPP ducts.

24.7 Working practices The fabrication of ductwork specified in this document is not affected by the addition of GRP.

Glass fibre separately

should be stored under clean dry

29

D/W154Specflcation for Plastics Ductwork

Table 10: Minimum const,uctional requirements rectangular CRP reinforced ducts

Longer Side Minimum Sheet Cross Joints Stiffeners Maximum Thickness and Spacing

GRP Reinforcement Between Joints/Stiffeners

UPVC FBIFP UPVC/FBPP UPVCIFBIPP UPVC/FB/PP 1 2 3 4 5 6

mm mm mm mm mm mm

Up to 1000 3 plus 3 plus socket & spigot 75 x 9 flat 800 0.6 kg/rn2 0.6 kg/rn2 as Fig. 30 as Fig. 31 or

GRP GRP or flanged 50 x 50 x 5 plastic as Fig. 29 or MS inverted

angle as Fig. 32 or former as

Fig. 33 1001 to 2250 4.5 plus 3 plus 75 x 9 flange 75 x 9 flat 600

0.6 kg/rn2 1.2 kg/rn2 welded on as Fig. 31 or GRP GRP both sides 50 x 50 x 5 plastic

as Fig. 29 or MS inverted angle as Fig. 32 or former as

Fig. 33 2251 to 3000 4.5 plus 6 plus 75 x 9 flange 75 x 9 flat 600

1.2 kg/rn2 1.2 kg/rn2 welded on as Fig. 31 or GRP GRP both sides 50 x 50 x 5 plastic

as Fig. 29 or MS inverted angle as Fig. 32 or former as

Fig. 33 Note: 1 On rectangular duct up to 400 mm longer side no stiffeners are required.

2 Applies to Tables 10 & 11. For constructional operating temperature limits refer to Part 2 clause 5.4. 3 Tables 10 & 11 apply to all pressure classes up to 1500 Pa.

Table 11: Minimum constructional requirements circular GRP reinforced ducts Diameter Minimum Sheet Cross Joints Stiffeners Maximum

Thickness and Spacing GRP Reinforcement Between

Joints/Stiffeners UPVC FBPP UPVC/FBPP UPVC/FBPP UPVC/FBPP

1 2 3 4 5 6 mm mm mm mm mm mm

Up to 1000 3 plus 3 plus socket & spigot 50 x 9 flat 2400 0.6 kg/rn2 0.6 kg/rn2 as Fig. 30 as Fig. 31

GRP GRP or flanged as Fig. 29

1001 to 1750 4.5 plus 3 plus 75 x 9 flange 75 x 9 flat 800 0.6 kg/rn2 1.8 kg/rn2 welded on as Fig. 31

GRP GRP both sides or former as Fig. 29 as Fig. 33

1751 to 2500 6 plus 6 plus 75 x 9 flange 75 x 9 flat 600 1.2 kg/rn2 1.8 kg/rn2 welded on as Fig. 31

GRP GRP both sides or former as Fig. 29 as Fig. 33

Note: On extruded tube up to 600mm diameter no stiffeners are required.

30

J D1W154 Specflcation for Plastics Ductwork

GRP reinforced Cross joints and

25 STANDARD COMPONENT DRAWINGS AND ABBREVIATIONS

25.1 The illustrations in this section not only highlight, where applicable, geometric limitations for the design and manufacture of ductwork components but also recommend

Stiff eners

standard drawing representation, terminology and abbreviations for both ductwork components and some of the more commonly used ancillary/plant items.

25.2 Designers and surveyors should note that bills of quantities should provide a full description.

31

Fig. 29 Flange Joint Gasket

IJPVC or FBPP flat continuously welded

$ + GRP first layer

Fig. 32 Stiffener Inverted angle

. GR.P to final thickness

L /

MS. or UPVC angle held tempofarily until GRP added

a1thicess Fig. 30 Socket and spigot joint

GRP to final thickness

Fig. 33 Stiffener use of former

Fig. 31 Stiffener Flat

OR!' Section of required thickness Former (e.g. expanded polyurethane) or wood I

UPVC or FBPP flat continuously welded

32

L) o +12

c +10

+8

o +6

-1-4

-z

TEMPERATURE C

Note: Figs. 34 & 35 shaded area refers to GRP reinforced duct

D/W1 54 Specification for Plastics Dctwork 1 Fig 34: Linear Thermal Expansion

+14

0

-4

6 30 20 10 0 10 20 30 40 50 60 70 80 90

TEMPERATURE C

Fig 35: Typical Design Stress for UPVC and PP

I

7

6

5

4

3

2

1

0 30 20 10 0 10 20 30 40 50 60 70 80 90

I D/W154 Specification for Plastics Ductwork

STANDARD COMPONENT DRAWINGS RECTANGULAR

Short Radius Bend Applies to any angle and for ducts up to 400 mm wide

FIG DRAWING DETAILS

36 I

Straight Duct with socket and spigot joint

37 IIII_____________

Straight Duct with flanged joints

38 Straight Duct with flanged joints

39

1 j- Minimum throat radius = 100 mm

40

Throat radius W/2

Medium Radius Bend (as illustrated) Applies to any angle

Long Radius Bend Similar but radius = W Applies to any angle

Minimum throat radius = 100 mm

Short Radius Bend with splitters

- mm Splitters Splitter Position

i-- -- b--

401600 1 W/3

6011000 2 W/4 W/2

10011800 3 W/8 W/3 W/2

Splitters not required in bend angles less than 45

42 'A

" 4 Square Bend with turning vanes

41

0

33

DIWI 54 Spec jfication for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS RECTANGULAR

34

DETAILS

Radius Tee with internal deflectors

Radiussed Twin Bend

Swept Branch

Square Tee with Turning Vanes

Breeches Piece

'Y' Piece

[b/WI 54 Spec jflcation for Plastics Ductwork

STANDARD COMPONENT DRAWINGS RECTANGULAR

FIG DRAWING DETAILS

49 5 MAX. Angled Offset 50 30 MAX. Mitred Offset

51 fl Minimum throat radius = 100 mm

Radiussed Offset

52 22.5 MAX. Concentric Taper

22.5 max in either plane Splitters are required for angles greater than 22.5 and should bisect the angle between any side and duct centreline

53 22.5 MAX.

22.5 MAX.

Eccentric Taper . 22.5 max in either plane

Splitters are required for angles greater than 22.5 and should bisect the angle between any side and duct centreline

54 22.5 MAX. Offset Taper Splitters are required for angles greater than 22.5 and should bisect the angle between any side and duct centreline

Rectangular Round Transformation 22.5 MAX

35

D1W154 Specification for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS RECTANGULAR

Rectangular Flat Oval Transformation

Square Branch

Angled Branch

Shoe Branch

Bell Mouth Branch

36

irii 45 MAX

w

Bell Mouth

Telescopic Joint Illustrated with flange

Branch duct width (W)

Dimensions (A)

mm

Up to 200 300 400 600

Over 600

Branch duct width (W)

Dimensions (A)

mm

Up to 200 300 400 600

Over 600

Branch duct width (W)

Dimensions (A)

mm

Up to 200 300 400 600

Over 600

I D!W154 Spec jflcation for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS RECTANGULAR

FIG DRAWING DETAILS

64 NRD \\ Non-Return Damper

65

I

Multi-Leaf Damper Can be spiggoted or flanged, opposed or parallel blade

Alternative controls are:-

Hand

Motorised

Pneumatic

HD

ic,xtcJ MD

PD

L-J

66 BG I Blast Gate Damper

Fire/Smoke Dampers/Sleeves

2hr. Rating

With installation frame

4hr. Rating

Smoke damper

Intumescent Sleeve

67

2hr

4hr

SD

37

D1W154 Specflcation for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS RECTANGULAR

FIG DRAWING DETAILS

68

AP

AD

ic IC

>.

J <

Access Openings

Access Panel Removable

Access Door Hinged

.

Inspection Cover

69 \I(

Flexible Connection

70 Drop Cheeked Radiussed Twin Bend

Drop Cheek Bend

72 \ Air Flow Symbol

71

38

I D/W1 54 Specflcation for Plastics Ductwork

STANDARD COMPONENT DRAWINGS RECTANGULAR

FIG DRAWING DETAILS

I!

Air Terminal Plenums

Plenum with side connection 73

74

75

76

77

Plenum with top connection

Cover plate with connection

Special plenum with connection

Telescopic connection in direction of air flow

THE ABOVE DETAILS ARE TYPICAL PLENUMS

39

D1W154 Spec jflcation for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS CIRCULAR

FIG DRAWING DETAILS

78 i

-

{ - - Straight Duct With male and female connectors

(MALE) (FEMALE)

79 I! U

StraightDuct With flange joint and slip joint

80

THROAT RADIUS = D/2 AS STANDARD

Bend Moulded/Formed Applies to any angle, eg. 300, 450 60, 90 Medium radius bend as illustrated. Long radius similar but throat radius = D

81

D -I

THROAT RADIUS = D/2 AS STANDARD

Segmented Bend 900 four section minimum as illustrated

Other Angles 60 = 3 sections 45 = 3 sections 30 = 2 sections

40

I D1W154 Spec jfication for Plastics Ductwork

STANDARD COMPONENT DRAWINGS CIRCULAR

FIG DRAWING DETAILS

82

J R

Segmented Twin Bend Radius = D/2 max

May also be fabricated from tube

83 Equal Tee Moulded/Formed

84 Twin Bend Moulded/Formed

85 Taper Concentric 150 as illustrated. Eccentric 300 included angle.

86 MAX. Short Taper

15 MAX.

41

DM1154 Specflcation for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS CIRCULAR

FIG DRAWING DETAILS

87 Offset

88 I

Shoe Branch Off rectangular

Branch duct dia (D)

Dimensions (A)

mm Up to 200

,, 300 ,,

400 600

Over 600

mm 75 100 125 150 200

89 Conical Branch Also acceptable with full conical surface

Branch duct dia(D)

Dimensions

(A)

mm

lip to 200 400 600

Over 600

mm 75

125 150 200

90 Angle Branch

91 Shoe Branch

92 Bell Mouth Branch

Branch duct dia(D)

Dimensions (A)

mm Up to 200

300 400 600

Over 600

mm 75 100 125 150 200

93 Mitred Branch

42

I D!W154 Spec jflcation for Plastics Ductwork

STANDARD COMPONENT DRAWINGS CIRCULAR

94

300 TO 90

FIG DRAWING DETAILS

Breeches Piece

95 - Blank End

- () Multi-Leaf Damper Can be spiggoted or flanged, opposed or parallel blade.

Alternative controls are:-

Hand

Motorised

Pneumatic

-L

97 & SBD

Single Bladed Damper

98 NRD Non-Return Damper Vertical application only

96

43

Fire/Smoke Dampers/Sleeves

2hr Rating

With installation frame

4hr Rating

Smoke damper

Intumescent Sleeve

Access Openings

Access panel removable

Access door hinged

Inspection cover

D/W1 54 Spec jflcation for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS CIRCULAR

Iris Damper

Discharge Continental Cowl

CONTINENTAL COWL

44

ji4Secjcationfor Plastics Ductwork STANDARD COMPONENT DRAWINGS CIRCULAR

FIG DRAWING DETAILS

103 I

==H High Velocity Discharge Terminal

104 Offset Stack Discharge Terminal

105

-

m GAP

-1- VERTICAL DISCHARGE WITH WEATHER COWL

Vertical Discharge with Weather Cowl

45

DM1154 Specification for Plastics Ductwork I

STANDARD COMPONENT DRAWINGS PLANT/EQUIPMENT/MISCELLANEOUS

FIG DRAWING DETAILS

106 [\/vcv\t\w Rectangular Attenuator

107 Circular Attenuator

108 Bend Attenuator

109 Heating Coil

110 1

Cooling Coil

lii J v'\._-'[ Electric Heating Coil

112 ) Humidifier 113 Axial Fan

114 Non-standard Ductwork Cross hatching (of any separate type) indicates by reference to a key, any non DW/154 ductwork system.

115 Flexible Ductwork

46

I D1W154 Specification for Plastics Ductwork

TABLE 12 STANDARD ABBREVIATIONS

ABBREVIATION FULL

AD Access Door AFF Axial Flow Fan AHU Air Handling Unit ALT Aluminium AP Access Panel AlT Attenuator ATU Air Terminal Unit BE Blank End BG Blast Gate Damper CC Cooling Coil CF Centrifugal Fan CTA Cross Talk Attenuator CVU Constant Volume Unit DP Drain Point EHC Electric Heating Coil EJ Expansion Joint FAT Fresh Air Inlet FA From Above FB From Below FBPP Fabric Backed Polypropylene Sheet Flex/C Flexible Connection Flex!D Flexible Duct FC False Ceiling FCU Fan Coil Unit FD Fire Damper FFL Finished Floor Level FJ Flanged Joint FOAM Rigid Polyurethane Self Extinguishing Foam FOB Flat on Bottom FOT Flat on Top GAM Galvanised after Manufacture GRP Glass Reinforced Plastic GSS Galvanised Sheet Steel HC Heating Coil HD Hand controlled Damper HH Hand Hole HL High Level HVD High Velocity Discharge IC Inspection Cover ID Iris Damper IFS Intumescent Fire Sleeve

47

D/W1 54 Spec jflcation for PL stics Ductwork I

TABLE 12 STANDARD ABBREVIATIONS CONTINUED

ABBREVIATION FULL

IU Induction Unit LL Low Level MD Motor controlled Damper MS Mild Steel NRD Non Return Damper NTS Not to Scale OBD Opposed Blade Damper OE Open End PBD Parallel Blade Damper PD Pneumatic controlled Damper PP Polypropylene PPS Self Extinguishing Polypropylene PRD Pressure Relief Damper PVC Polyvinyl Chloride RFC Rolled Form Channel RSC Rolled Steel Channel RU Roof Unit SBD Single Blade Damper SD Smoke Damper Si Slip Joint ST/ST Stainless Steel SSL Structural Slab Level TA To Above TB To Below TD Top Down (In Direction of Flow) Ti Telescopic Joint TP Test Point TV Turning Vane TU Top Up (In Direction of Flow) UOS Unless Otherwise Stated UPVC Unpiasticised Polyvinyl Chloride US Underside UV Ultra Violet Light VAV Variable Air Volume 50 RSA Rolled Steel Angle (With Size)

48

] DM1154 Spec jflcation for Plastics Ductwork

APPENDIX A Air Leakage From Ductwork To be read in conjunction with DW/1 43 A practical guide to Ductwork Leakage Testing CAUTION As highlighted in both this document and DW1143, not enough emphasis can be placed on the fact that, except for high pressure class C, the much more stringent ductwork constructional standards brought about by the general acceptance of DW/154 have virtually negated the requirement for leakage-testing. It is essential to realise that except where it is mandatory this document is not an endorsement of the routine testing of ducts but purely a guide to outline the procedures for conformity with the air leakage limits in Table 1. Where the specified methods of assembly and sealing of ducts are used, a visual inspection will ordinarily suffice for verification of a well engineered and acceptably airtight construction. WHERE NOT MANDATORY, DUCT LEAKAGE TESTING IS GENERALLY AN UNJUSTIFIED AND SUBSTANTIAL EXPENSE.

A.1 INTRODUCTION Leakage from ducted air distribution systems is an important consideration in the design and operation of ventilation and air conditioning systems. A ductwork system that has limited air leakage, within defined limits, will ensure that the design characteristics of the system can be maintained. It will also ensure that energy and operational costs are maintained at optimum levels. Ductwork constructed and installed in accordance with DW1154 should minimise a level of air leakage that is appropriate to the operating static air pressure in the system. However, it is recognised that the environment in which systems are installed is not always conducive to achieving a predictable level of quality in terms of system air leakage and it is therefore accepted that designers may sometimes require the systems to be tested in part or in total. It should be recognised that the testing of duct systems adds a significant cost to the installation and incurs some extra time within the programme (See 4.7 and 6.4 re mandatory testing).

A.2 DUCT PRESSURE Ductwork constructed to DW/154 will be manufactured to a structural standard that is compatible with the system operating pressure. There are three classes of duct construction to correspond with the three pressure classifications: Class A Low pressure ducts suitable for a maximum positive operating pressure of 500 Pascals and a maximum negative pressure of 500 Pascals. Class B Medium pressure ducts suitable for a maximum positive operating pressure of 1000 Pascals and a maximum negative pressure of 750 Pascals. Class C High pressure ducts suitable for a maximum positive operating pressure of 2000 Pascals and a maximum negative pressure of 750 Pascals.

A.3 LEAKAGE FROM DUCTWORK Leakage from plastic air ducts occurs at the joints and is therefore proportional to the total surface area of the ductwork in the system. The level of leakage is similarly related to the air pressure in the duct system and whilst there is no precise formula for calculating the level of air loss it is generally accepted that leakage will increase in proportion to pressure to the power of 0.65. The effect of air leakage from high pressure! velocity ductwork is critical in terms of system performance, energy consumption and the risk of high frequency noise associated with leakage. These problems are less critical with medium pressure/velocity systems, but should be considered. Low pressure/velocity ducts present the lowest risk in terms of the effect of leakage on the operation of the system.

As there is no direct relationship between the volume of air conveyed and the surface area of the ductwork system required to match the building configuration it is difficult to express air leakage as a percentage of total air volume. Similarly, the operating pressure will vary throughout the system and as leakage is related to pressure the calculations are complex. However, it is generally accepted that in typical good quality systems the leakage from

49

A.4 SYSTEM LEAKAGE LOSS

D1W154 Specfication for Plastics Ductwork

each class of duct under operating conditions will be in the region of: Class A low pressure 6% Class B medium pressure 3% Class C high pressure 2%

A.5 SPECIFYING AIR LEAKAGE TESTING Respecting both the cost and programme implications associated with testing ducts for leakage, the designer may, for example indicate that a particular system is tested as follows:

a) High pressure ducts all tested. b) Medium pressure ducts 10% of the

ductwork shall be selected at random and tested.

c) Low pressure untested. In any case where a random test is selected for medium pressure ducts the following clause is suggested for inclusion by the designer.

Table 13: Air leakage rates

The designer shall select at random a maximum of 10% of the duct system to be tested for air leakage. The duct shall be tested at the pressure recommended in Table 13 for the classification for the section of the ductwork that is to be tested. The tests shall be carried out as the work proceeds and prior to the application of thermal insulation. In the event of test failure of the randomly selected section, the designer shall have the right to select two further sections at random for testing. Where successive failures are identified there shall be a right to require the contractor to apply remedial attention to the complete ductwork system. The contractor shall provide documented evidence of the calculations used to arrive at the allowable loss for the section to be tested and the client, or his agent, shall witness and sign the results of the test.

Static pressure

differential 1

Pa 100 200 300 400 500 600 700 800 900

1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Low-pressure Medium-pressure High-pressure ClassA Class B Class C

2 3 4 Litres per second per square metre of surface area

0.54 0.18 0.84 0.28 1.10 0.37 1.32 0.44 1.53 0.51

0.19 0.21 0.23 0.25 0.27 0.29 0.30 0.32 0.33 0.35 0.36 0.38 0.39 0.40 0.42

Note: Recommended 'mean' test pressures are highlighted in bold type with the actual selection being left to the test operator.

50

Maximum leakage of ductwork

0.58 0.64 0.69 0.75 0.80

J D/W1 54 Spec jfication for Plastics Ductwork ] A.6 SPECIAL CASES

There may be situations on a project where circumstances dictate that special consideration be given to containing air losses, e.g. a long run of ductwork may incur a disproportionate level of air loss. In cases such as this example the designer can specify an improved standard of airtightness, i.e. 80% of allowable loss for Class 'B' ducts. The designer should not specify a Class 'C' test at Class 'C' pressure for a Class 'B' duct.

A.7 SUGGESTED RANGE OF TESTING High pressure ducts 100% test Medium pressure ducts See A5 Low pressure ducts Untested Exposed extract systems Untested Ceiling void extract

systems Untested Secondary ducts from

VAV or fan coil units Untested Flexible ducts Untested Final connections and

branches to grilles and diffusers Untested

A.8 TESTING OF PLANT ITEMS Items of inline plant (eg. Figs. 106 to 115) will not normally be included in an air leakage test. The ductwork contractor may include such items in the test if the equipment has a certificate of conformity for the pressure class

and air leakage classification for the system under test.

A9 DESIGNER'S CALCULATIONS The designer can calculate with reasonable accuracy the predicted total loss from a system by:

a) Calculating the operating pressure in each section of the system.

b) Calculating the surface area of the ductwork in each corresponding pressure section.

c) Calculating the allowable loss at the operating pressure for each section of the system (see table 13 for allowable leakage figures).

A.1O VARIABLE PRESSURES IN SYSTEMS Designers can achieve significant cost savings by matching operating pressures throughout the system to constructional standards and appropriate air leakage testing, e.g. the practice of specifying construction standards for whole duct systems based on fan discharge pressures may incur unnecessary costs on a project. For example, some large systems could well be classified for leakage limits as follows:

Plant room risers Class C Main floor distribution Class B Low pressure outlets Class A

51

D/W1 54 Spec jflcation for Plastics Ductwork

Fig. 116 Permitted leakage at various pressures

52

0 0 co

0 0

0 0

0 0

0 0

0 0 en

0 0

0 0 2

0 0 oo 0 0

0 0 "C

0 0

0 0

0 0 en

0 0

0 0

0

Leakage in litres per second per square metre duct surface area

h

r 0

J D1W154 Specification for Plastics Ductwork

Example of a completed test sheet Test No

General Name of job Building Ref

Part 1 Physical details a Section of ductwork to be tested b Drawing Number c Pressure Classification ypjxps.). d Test static pressure e Leakage factor 14 ooirnis f Surface area of duct under test (FR g Maximum permitted leakage

Part 2 Test particulars a Duct static pressure reading b Manufacturer and type of flow measuring device i ,. / (FROM RIG MANUFACTURERS c Range of measurement of flow measuring device d Reading of flow measuring device

(DERIVED FROM CHART SUPPLIED WITH RIG USING "d") e Interpreted air flow leakage rate f Duration of test (normally 15 minutes) Date of test Caed out by Witnessed by .... (Signature) (Signature)

Printed Name... Printed Name ./ and Company and Company

Width and depth or diameter Periphery Length Area

millimetres millimetres metres square metres

800x750 3100 17.55 54.40

600x650 2500 5.57 13.93

300x 300 1200 1.20 1.44

305 dia. 958 7.00 6.70

250 dia. 785 4.50 3.53

TOTAL 80.00

53

I DM1154 SpecUication for Plastics Ductwork

APPENDIX B Guidance Notes For The Transport, Handling and Storage of Ductwork It is recommended that before a contract is finalised, that consideration is given to the subject of site access, material handling and storage as they have a strong influence on the cost efficiency of the overall activity of ductwork installation.

B.1 Storage and Handling of Raw Material Material should be stored in suitably designed racking out of direct sunlight. Where possible these racks should be metal to earth Edges of cut sheet may be sharp and protective gloves are advised. Wearing steel toe-capped boots is recommended. Most plastic sheet is manufactured with smooth surfaces and/or is supplied with protective coatings. Care must be taken to prevent accidental slippage of stacked materials. Being good electrical insulators, the movement of stock, unless earthed, will allow the build up of static. All stock shapes are chemically stable at normal temperatures. Whilst some raw materials used in their manufacture may themselves present a toxic hazard, once incorporated into the stock shape they no longer constitute such a hazard, and no dermatitic hazards are known nor are any environmental problems expected.

B.2 Transport Large capacity vehicles with high-sided open or closed-top bodies are the most suitable for the transport of ductwork. Careful consideration should be given to the unloading of transport on site as not all sites benefit from the material handling and access facilities that exist in a manufacturing workshop such as cranes, fork-lifts or loading bays. Site handling facilities along with vehicular access restrictions may influence the type and size of transport to be utilised. Lengths of ductwork should be positioned so as to avoid crushing. Lengths with projections, such as branches and bends, flanges, girths, damper quadrants should be loaded so as to

avoid damage to adjacent duct panels. In some cases, particularly on contracts calling for repetitive sizes, the use of timber jigs and spacers may be justified. Where reduced bulk and greater protection are major factors, such as consignments for export, transporting ductwork in 'L' shape sections may justify the increased site assembly costs.

Handling To minimise the risk of damage, duct sections should be clearly identified and deliveries to site should be closely linked to the installation programme, so as to avoid accumulation of unfixed ductwork and minimise double handling. It is important to recognise that ductwork panels, joints and corners are susceptible to damage and care must be taken when handling such material through a site. During handling, individual items of ductwork may be liable to slight cross sectional deformation until they become an integral part of a completed ductwork system. Whilst this may temporarily detract from its intended appearance, this deformation will not have any detrimental effect on the functionality of the finally assembled system. Installation of ductwork and associated plant items will inevitably involve manual handling. The responsibility of employers and employees to assess the risk of personal injury during manual handling operations is set out in the H.S.E. publication L23, Guidance on Manual Handling Regulations 1992.

B.4 Site storage Adequate floor space must be provided within the building for the site storage of ductwork. Such storage shall make due allowance for the storage of ductwork in stacks such that access between them is of sufficient width to permit the removal of items without interference to adjoining stacks. Ductwork components should be positioned so as to avoid crushing. Ductwork of small panel size may be stored horizontally; however care should be exercised to ensure that stack sizes are limited to within the structural strength of the duct sections to prevent distortion of the lower sections within the stack.

B.3

54

j D!W1 54 Specification for Plastics Ductwork B.5 Internal cleanliness of new ductwork

The site storage of ductwork introduces the important consideration of maintaining the internal cleanliness of the ductwork. Reference should be made to HVCA document:- DW/TM2 Guide to Good Practice Internal Cleanliness of New Ductwork Installations.

If the above conditions can not be satisfied consideration should be given by the designer to amending the specification to include for "Post Installation Cleaning" as covered by the HVCA document:-

TR/17 Guide to Good Practice Cleanliness of Ventilation Systems.

APPENDIX C Fire Retardant Finishes CI Improvement in the fire retardancy of plastic

ducts can be achieved to varying degrees and is wholly dependent upon the surface coating, laminating resin selected and construction specification adopted. In some instances smoke emission is considered equally with other specification requirements of the materials resistance to ignition and burning. It is, therefore, important for designers to establish the clients' and officers' detailed requirements and not rely on a third party's interpretation of 'fire resisting or fire retardant'. Where possible the specification should refer directly to compliance with a British or European Standard identifying the specific sections applicable. There are various types of resin and mat reinforcements that can achieve a Class 1 surface spread of flame rating when tested according to BS476 Part 7 (1987). This test puts materials into Class 1 - 4 in descending order of performance, according to the rate and extent of flame spread over their surfaces under standard heating conditions. Materials should also be tested for fire propagation to BS476 Part 6 (1989). This test measures the amount and rate of heat evolved by the material when subjected to standard heating

conditions. Test results are given as an index of Performance (i) which is based on three sub indices (i1), (i2), (i3). The higher the value of the Index of Performance (i) the greater is the material's contribution to fire growth. The higher the value of the sub-index (i1), the greater the ease of ignition and flame spread. The highest product performance classification, as defined in Approved Document B of the Building Regulations, is Class 0. This is achieved if a material surface of a