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AS 1576.4—1991
Australian Standard�
Scaffolding
Part 4: Suspended scaffolding
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This Australian Standard was prepared by Committee BD/36, Scaffolding. It was approvedon behalf of the Council of Standards Australia on 20 August 1991 and published on7 October 1991.
The following interests are represented on Committee BD/36:
A.C.T. Administration, Office of City Management
Aluminium Development Council
Australian Federation of Construction Contractors
Confederation of Australian Industry
Department of Industrial Affairs, Qld
Department of Labour and Industry, Tas.
Department of Labour, S.A.
Department of Labour, Vic.
Department of Occupational Health Safety and Welfare, W.A.
Master Builders Construction and Housing Association, Australia
Metal Trades Industry Association of Australia
National Association of Scaffolding and Formwork Contractors
Workcover Authority, N.S.W.
Work Health Authority, N.T.
Review of Australian Standards. To keep abreast of progress in industry, Australian Standards are subject toperiodic review and are kept up to date by the issue of amendments or new editions as necessary. It is importanttherefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto.
Full details of all Australian Standards and related publications will be found in the Standards Australia Catalogueof Publications; this information is supplemented each month by the magazine ‘The Australian Standard’, whichsubscribing members receive, and which gives details of new publications, new editions and amendments, and ofwithdrawn Standards.
Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, arewelcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made withoutdelay in order that the matter may be investigated and appropriate action taken.
This Standard was issued in draft form for comment as DR 90080.
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AS 1576.4—1991
Australian Standard�
Scaffolding
Part 4: Suspended scaffolding
First published as AS 1576.4–1991.
Incorporating:Amdt 1–1992
PUBLISHED BY STANDARDS AUSTRALIA(STANDARDS ASSOCIATION OF AUSTRALIA)1 THE CRESCENT, HOMEBUSH, NSW 2140
ISBN 0 7262 7102 0
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PREFACE
This Standard was prepared by the Standards Australia Committee on Scaffolding. It is one ofa series of four Standards which collectively supersede and amalgamate AS 1575–1974,Tubes, couplers and accessories used in metal scaffolding and AS 1576–1974, SAA MetalScaffolding Code which will be withdrawn on 30 June 1992.
� Copyright — STANDARDS AUSTRALIA
Users of Standards are reminded that copyright subsists in all Standards Australia publications and software. Except where the Copyright Act allowsand except where provided for below no publications or software produced by Standards Australia may be reproduced, stored in a retrieval system inany form or transmitted by any means without prior permission in writing from Standards Australia. Permission may be conditional on an appropriateroyalty payment. Requests for permission and information on commercial software royalties should be directed to the head office of StandardsAustralia.
Standards Australia will permit up to 10 percent of the technical content pages of a Standard to be copied for use exclusively in–house bypurchasers of the Standard without payment of a royalty or advice to Standards Australia.
Standards Australia will also permit the inclusion of its copyright material in computer software programs for no royalty payment providedsuch programs are used exclusively in–house by the creators of the programs.
Care should be taken to ensure that material used is from the current edition of the Standard and that it is updated whenever the Standard is amended orrevised. The number and date of the Standard should therefore be clearly identified.
The use of material in print form or in computer software programs to be used commercially, with or without payment, or in commercial contracts issubject to the payment of a royalty. This policy may be varied by Standards Australia at any time.
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CONTENTS
Page
SECTION 1 SCOPE AND GENERAL 1.1 SCOPE 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 REFERENCED DOCUMENTS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 DEFINITIONS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 2 DESCRIPTION OF SUSPENDED SCAFFOLDING 2.1 GENERAL 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 SYSTEM OF ATTACHMENT TO STRUCTURE 8. . . . . . . . . . . . . . . . . . . . 2.3 HORIZONTAL MOVEMENT CAPABILITY 8. . . . . . . . . . . . . . . . . . . . . . . 2.4 SUSPENSION SYSTEM 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 TYPES OF CRADLES 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 3 MATERIALS AND COMPONENTS 3.1 STEEL 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 ALUMINIUM 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 SCAFFOLD TUBES AND COUPLERS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 SUSPENSION AND SECONDARY ROPES 10. . . . . . . . . . . . . . . . . . . . . . . . 3.5 SCAFFOLDING HOISTS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 COUNTERWEIGHTS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 STRUCTURAL PLYWOOD 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 TROLLEYS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 4 GENERAL REQUIREMENTS 4.1 GENERAL 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 GROUPING OF LIVE LOADS 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 WORKING LOAD LIMIT 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 STRENGTH OF SUPPORTING STRUCTURE 11. . . . . . . . . . . . . . . . . . . . . 4.5 LOAD–LIMITING DEVICE 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 VERTICAL SPEED 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 ROPE TENSION 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 STABILITY OF CANTILEVER SUSPENSION RIG 11. . . . . . . . . . . . . . . . . 4.9 CRADLE 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 ROPE 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 SUSPENSION AND SECONDARY ROPES 12. . . . . . . . . . . . . . . . . . . . . . . . 4.12 SUSPENSION RIG 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13 SUSPENSION RIG COMPONENTS 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 5 ELECTRICAL EQUIPMENT AND CONTROLS 5.1 GENERAL 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 CONTROL BOX 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 CONTROLS 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 ELECTRICAL CABLES 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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AS 1576.4—1991 4
STANDARDS AUSTRALIA
Australian Standard
Scaffolding
Part 4: Suspended scaffolding
SECTION 1 SCOPE AND GENERAL
1.1 SCOPE This Standard sets out requirements for the materials, and design, of suspended scaffolding including thesupporting structure.This Standard does not cover building maintenance units.This Standard is to be read in conjunction with AS 1576.1.1.2 REFERENCED DOCUMENTS The following documents are referred to in this Standard:AS1170 SAA Loading Code1170.1 Part 1: Dead and live loads and load combinations1170.2 Part 2: Wind loads
1418 SAA Crane Code1418.1 Part 1: General requirements1418.2 Part 2: Serial hoists and winches
1444 Wrought alloy steels — Standard and hardenability (H) series
1538 SAA Cold-formed Steel Structures Code
1554 SAA Structural Steel Welding Code
1576 Scaffolding1576.1 Part 1: General requirements1576.2 Part 2: Couplers and accessories1576.3 Part 3: Prefabricated and tube-and-coupler scaffolding
1577 Solid timber scaffold planks
1578 Laminated timber scaffold planks
1594 Hot-rolled steel flat products
1664 SAA Aluminium Structures Code
1665 SAA Aluminium Welding Code
1720 Timber structures1720.1 Part 1: Design methods
1734 Aluminium and aluminium alloys — Flat sheet, coiled sheet and plate
1866 Aluminium and aluminium alloys — Extruded rod, bar, solid and hollow shapes
1867 Aluminium and aluminium alloys — Drawn tubes
1874 Aluminium and aluminium alloys — Ingots and castings
2269 Structural plywood
2317 Collared eyebolts
3190 Approval and test specification — Residual current devices (current operated earth leakage devices)
3569 Steel wire ropes
3678 Hot-rolled structural steel plates, floorplates and slabs
3679 Hot-rolled structural steel bars and sections
4100 SAA Steel Structures Code
1.3 DEFINITIONS For the purpose of this Standard, the definitions given in AS 1576.1 and those below apply.
1.3.1 Articulated cradle — a cradle of several sections hinged together enabling workers to walk from one section toanother (see Figure 1.2).
1.3.2 Bay length — the distance between any two longitudinally adjacent support points on a cradle measuredhorizontally.
1.3.3 Boatswain’s chair— a special purpose cradle comprising a seat.
1.3.4 Counterweight— a weight or series of weights used to counterbalance the forces on the suspension rig againstoverturning.
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5 AS 1576.4—1991
1.3.5 Cradle — that portion of the assembly incorporating a suspended platform.
1.3.6 Double rope suspension system— a method of suspending a cradle using two hoists and two suspension ropesat each support point.
1.3.7 Fixed cradle— a cradle which does not traverse horizontally but which is capable of being raised and lowered.
1.3.8 Fulcrum point — the point of pivoting nearest to the outside edge of the suspension rig about which thebalancing moments of the suspension rig are calculated.
1.3.9 Inboard portion of the suspension rig— that portion of the suspension rig which is on the inside of the fulcrumpoint (see Figure 1.1).
1.3.10 Individual cradle — a cradle of one bay length (see Figure 1.3).
1.3.11 Lever arm— the distance between the fulcrum point and the centre of gravity of the suspension rig includingany counterweights.
NOTE: The projection length is the length which is used in the calculation of moments for stability.
1.3.12 Load-limiting device— a device that limits the lifting capacity of a scaffold hoist to a specific load below thestalling load of the motor.
1.3.13 Maximum total suspended load— the maximum force which can be imposed on the suspension rig includingthe working load limit on the platform, the self-weight of the platform and the suspension and safety ropes together withany portion of the means of suspension and the rope tensions, and any extra force resulting from the operation of theequipment and environmental loads.
1.3.14 Needle— a continuous structural member that extends from the suspension point to the extreme inboard endof the supporting structure.
1.3.15 Outboard portion of the suspension rig— that portion of the suspension rig which is on the outside of thefulcrum point (see Figure 1.1).
1.3.16 Prefabricated platforms— a framed assembly of one bay length, incorporating a walking surface, which iscapable of connecting to its support structure in such a way as not to be inadvertently dislodged. One or moreprefabricated platform units can be used side-by-side and end-to-end to form a working platform.
1.3.17 Projection length— the horizontal distance between the fulcrum point and the suspension point.NOTE: The projection length is the length which is used in the calculation of moments for stability.
1.3.18 Scaffolding hoist— a lifting appliance manually operated or power-operated through which the suspension ropepasses.
1.3.19 Working load limit — the working load limit is the maximum live load which may be placed on the cradleper bay.
1.3.20 Protective device— a device which will arrest the descent and support a cradle or boatswain’s chair in theevent of the failure of the suspension rope or the scaffolding hoist.
NOTE: A protective device may also prevent an overspeed descent.
1.3.21 Secondary rope— rope not normally carrying the weight of a cradle and the imposed load, but rigged for usewith a protective device.
1.3.22 Single-rope suspension system— a method of suspending a cradle using one hoist and a single suspension ropeat each support point.
1.3.23 Stop— the attachment at or near the end of a rail or track or at an intermediate point to prevent furthertraversing of the cradle.
1.3.24 Suspension-mounted hoist— a scaffolding hoist which is mounted on the suspension rig or trolley track withone end of the rope attached to the cradle.
1.3.25 Suspension gear— the assembly which joins the cradle to the suspension rig.
1.3.26 Suspension point— that point where the suspension rope is connected to the suspension rig.
1.3.27 Suspension rig— that portion of the structure (including the trolley track) mounted at a level higher than thecradle to support and position the cradle.
1.3.28 Suspension ropes— ropes carrying the weight of the cradle and the imposed load.
1.3.29 Travelling or traversing cradle— a cradle capable of being moved horizontally.
1.3.30 Traversing— moving laterally across the face of the building in a cradle.
1.3.31 Traversing ropes— ropes rigged for the purpose of traversing the cradle, but not carrying the weight of it.
1.3.32 Traversing suspension rig— a suspension rig mounted on wheels or castors and supporting a cradle.
1.3.33 Trolley— a wheeled mechanism intended to support a serial hoist and capable of travelling along a suspendedtrack.
1.3.34 Trolley track — the suspended rail which supports and guides trolleys in traversing installations.
1.3.35 Work cage— a cradle which is supported by a single suspension rope.
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AS 1576.4—1991 6
FIGURE 1.1 TYPICAL SUSPENSION RIGS
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FIGURE 1.2 TYPICAL ARTICULATED CRADLE
FIGURE 1.3 TYPICAL INDIVIDUAL CRADLE
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AS 1576.4—1991 8
SECTION 2 DESCRIPTION OF SUSPENDED
SCAFFOLDING
2.1 GENERAL Suspended scaffolding is described according to the system of attachment to the structure, thehorizontal movement of the cradle, the suspension system, and the type of cradle.
2.2 SYSTEM OF ATTACHMEN T TO STRUCTURE The system of attachment to thestructure may be one of thefollowing:
(a) Systems which rely on counterweights for their stability.
(b) Systems which are secured to the building or structure.
(c) A combination of systems specified in Items (a) and (b).
2.3 HORIZONTA L MOVEMEN T CAPABILIT Y Thehorizontal movement capability may be oneof thefollowing:
(a) Fixed.
(b) Traversing cradle.
(c) Traversing suspension rig.
2.4 SUSPENSION SYSTEM The suspension system may be one of the following:
(a) Hoist reeling — where the hoist reels the wire rope on to a drum within the hoist.
(b) Hoist climbing — where thehoist ‘climbs’ up the wire rope leaving the tail end of the ropehanging or reeled ontoa separate device below the hoist.
2.5 TYPES OF CRADLE S The cradles may be one of the following (see Figure 2.1):
(a) Articulated cradle The working area can be a single deck or several decks beneath each other.
(b) Individual cradle This type can have a single deck or several decks beneath each other.
(c) Boatswain’s chair.
(d) Work cage.
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9 AS 1576.4—1991
FIGURE 2.1 TYPES OF CRADLE
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AS 1576.4—1991 10
SECTION 3 MATERIALS AND COMPONENTS
3.1 STEEL Steel components shall be manufactured from steel complying with AS 1444, AS 1594, AS 3678,or AS 3679, as appropriate.
3.2 ALUMINIUM Aluminium components shall be manufactured from aluminium complying with AS 1734,AS 1866, AS 1867, or AS 1874, as appropriate.
3.3 SCAFFOLD TUBES AND COUPLERS
3.3.1 Tube Steel and aluminium tube shall comply with AS 1576.3.
3.3.2 Couplers and accessoriesCouplers and accessories shall comply with AS 1576.2.
3.4 SUSPENSION AND SECONDARY ROPESSuspension and secondary ropes shall comply with AS 3569.
3.5 SCAFFOLDING HOISTS Scaffolding hoists shall comply with AS 1418.2.
3.6 COUNTERWEIGHTS Counterweight material shall be durable, such that the weight shall remain constantunder working conditions. Bags of sand or similar material shall not be used.
The mass of the counterweight, in kilograms, shall be marked on it.
3.7 STRUCTURAL PLYWOOD Structural plywood shall comply with AS 2269.
3.8 TROLLEYS Trolleys shall comply with AS 1418.2 and the following requirements:
(a) Where intended for use with a cradle, the trolley shall be designed to incorporate a space bar.
(b) The working load limit shall be the greater of —
(i) the maximum rope tension; and
(ii) 5 kN.
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SECTION 4 GENERAL REQUIREMENTS
4.1 GENERAL The design of structural members and components shall comply with the relevant requirementsof the following Standards: AS 1170.1, AS 1170.2, AS 1418, AS 1538, AS 1554, AS 1664, AS 1665, AS 1720.1and AS 4100.
The design shall take account of:
(a) Wind sail conditions created by a weather cover, safety screening, or other sheeting material attached to ascaffold.
(b) The need for overhead and side protection for the occupants.
4.2 GROUPING OF LIVE LOADS The design of all parts of the installation shall take account of the possiblegrouping of the live loads at one end of the cradle.
4.3 WORKING LOAD LIMIT The working load limit shall be not less than light duty loading in accordancewith AS 1576.1. The working load limit, in kilograms, shall be marked on the cradle in each bay, in a placewhere it is clearly visible.
4.4 STRENGTH OF SUPPORTING STRUCTURE The structure supporting the suspended scaffold systemshall be able to sustain the maximum total suspension load. For mobile systems, this requirement applies to allpositions of its travel.
Where spreaders or pads are used to distribute a load on a roof or parapet, the material shall be such that a properdistribution of the load is achieved, and that the spreader or pad will not adversely deteriorate in the workingenvironment.
4.5 LOAD-LIMITING DEVICE Electrically powered scaffolding hoists shall have a device to limit the liftingcapacity of the hoist to a maximum 1.25 times the rating of such hoist.
4.6 VERTICAL SPEED The vertical speed of any suspended scaffold shall not exceed 12 m/min.
4.7 ROPE TENSION Rope tension for electrically powered scaffolding hoists is the summation of the loadwhich is limited by the load-limiting device in Clause 4.5, the gravitational load of the suspension rope and anytensioning weight.
Rope tension for other than electrically powered scaffolding hoists shall be the summation of —
(a) the self weight of the suspension rope and any tensioning weight;
(b) the self weight of the scaffolding hoist and any secondary rope device;
(c) that portion of the self weight of the cradle acting on the rope (or the self weight of the boatswain’s chair);and
(d) the rated live load for the cradle taking into account grouping of live loads or the rated live load of theboatswain’s chair.
4.8 STABILITY OF CANTILEVER SUSPENSION RIG
4.8.1 General Stability of a cantilever suspension rig against overturning shall be by counterweights oranchorage.
4.8.2 Determination of stability Factors in the determination of stability shall include the following:
(a) Three times the rope tension from Clause 4.7.
(b) The grouping of suspension ropes relative to attachment points.
(c) The outboard portion of the suspension rig and any attached traversing track.
(d) The inboard portion of the suspension rig including counterweights if used.
4.8.3 Lateral stability The suspension rig and cantilevers, and traversing track if used, shall have adequatelateral strength or be adequately braced against lateral sway in the longitudinal direction.
NOTE: The forces producing lateral sway include wind forces, surge from braking, and the applied force from traversing lines.
For a wire rope braced suspension rig, the restraining wire ropes shall be so angled in plan, or supplemented byadditional angled wire ropes or other means that lateral stability in both directions is achieved.
4.8.4 Counterweights Counterweights shall be fixed to the suspension rig in such a way as to prevent theirdislodgement under all expected conditions of operation of the equipment.
4.8.5 Suspension anchorage pointsSuspension anchorage points shall take into account the nature of thematerial into which the anchor is fastened.
Drilled-in anchors, whether expanding or chemical type, shall not be used in an anchorage system to resist atensile (pull-out) force.
Bolts used in an anchorage system shall be fitted with locknuts.
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AS 1576.4—1991 12
4.9 CRADLE
4.9.1 Width The width of the platform shall be not less than 450 mm.
4.9.2 End extensions End extensions to the cradle shall be limited in length to that allowed by the cradledesign.
4.9.3 Decking The decking of the platform shall have a surface that does not become slippery under expectedworking conditions. It shall be fixed so that it cannot be accidentally displaced. Except to the extent necessaryfor drainage, the decking shall be closely boarded, planked, or plated.
A prefabricated platform shall comply with the performance requirements of AS 1576.3.
Scaffold planks if used for decking shall comply with AS 1577 or AS 1578.
4.9.4 Guardrails, midrail, and toeboards Guardrails, midrails and toeboards shall be designed in accordancewith AS 1576.1 and fitted to the perimeter of the platform.
Where the cradle is tied to the building and the building forms a barrier at that level, the inner guardrails maybe removed provided they are not an integral component of the cradle design.
4.9.5 Suspension linkThe design of the link used to attach the hoist to the cradle shall take into account anyforces resulting from out of level of the cradle in any direction.
4.9.6 Buffers Where face wall rollers or buffers are used, they shall be attached to the cradle, and visible tothe operator.
4.9.7 Articulated cradles Articulated cradles shall be designed to take into account the configurations andresulting loads.
The hinged area shall be designed to minimize gaps in the decking, guardrails and toeboards.
4.9.8 Other shapesVarious shaped cradles may be used, and such configurations shall be specifically designedand special attention paid to the required suspension rig.
4.9.9 Boatswain’s chair The scaffolding hoist fitted to a boatswain’s chair shall be capable of being manuallyoperated by the user, in a safe manner, in an emergency or power failure.
4.10 ROPE Fibre ropes shall not be used for the lifting or suspension of scaffolding, but may be used fortraversing.
Steel wire rope of a construction other than that recommended by the scaffolding hoist manufacturer shall notbe used with such a hoist.
NOTE: Galvanizing of steel wire rope is recommended.
4.11 SUSPENSION AND SECONDARY ROPESSuspension and secondary ropes each shall be terminatedat the rig end with a thimble eye splice, or ferrule secured eye termination or other rope coupling device whichdoes not damage the rope and gives a strength of not less than 80% of the breaking load of the rope.
The rope shall hang freely from the suspension rig by an eye which complies with AS 2317 and shall not bereeved through the eye.
Rope bullet end termination shall be suitable for its purposes and finished to prevent overlaying.
Where appropriate, the tail end of the rope shall be fitted with a suitable rope clamping device to prevent the ropepassing through the hoist.
The rope shall be long enough so that the system does not run out of rope.
A secondary rope shall have a strength of not less than the relevant suspension rope.
4.12 SUSPENSION RIG The fulcrum point for static suspension rig is shown in Figure 1.1. The fulcrum pointfor a mobile suspension rig is the centre-line of the front wheel.
Adequate means shall be provided to ensure that the suspension system shall not slip off the end of the needle.
4.13 SUSPENSION RIG COMPONENTS
4.13.1 Trolley track Suspension from a scaffold coupler designed for joining tubes is not permitted.
Stops shall be attached to the trolley track using a positive method (e.g. nut and bolt). Friction stops shall notbe used.
4.13.2 Parapet clampsParapet clamps shall be used only where the parapet has adequate strength.NOTE: Parapet clamps should not be used on brick parapets.
4.13.3 Pulleys Where a wire rope passes over pulleys or around drums other than in winches and climbingdevices, such pulleys or drums shall have pitch circle diameters in accordance with AS 1418.1.
Guide pulleys external to the winch or climbing device shall have pitch circle diameters in accordance withAS 1418.1.
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4.13.4 Protective deviceA protective device shall be provided for each scaffolding hoist. The protective deviceshall operate on the suspension rope above the scaffolding hoist or on a secondary rope. A protective device shallcomply with the following requirements:
(a) The device shall be designed to withstand the greatest of the following:
(i) The combined loading of the working load limit and mass of the equipment in motion.
(ii) The inertial-effect loading of the combined loading of maximum working load limit and mass of theequipment in motion resulting from the operation of the protective device under free-fall stoppingconditions for the rate of deceleration determined by rational analysis, without stressing any componentin excess of 75% of its yield stress.
(iii) The inertial-effect loading of the combined loading of the working load limit and mass of the equipmentin motion due to the operation of the protective device under overspeed stopping conditions for the rateof deceleration determined by rational analysis without stressing any component in excess of 75% ofits yield stress.
(b) Means shall be provided to deactivate the device.
(c) The device shall be mounted in such a way that the stability of the cradle is not adversely affected when thedevice is activated.
4.13.5 Secondary ropeA secondary rope, where fitted, shall be independently attached to the suspension rig.
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AS 1576.4—1991 14
SECTION 5 ELECTRICAL EQUIPMENT AND CONTROLS
5.1 GENERAL Electrical equipment and controls shall comply with AS 1418.2 and the requirements of thisSection.
5.2 CONTROL BOX Where a central control box is fitted, the main supply cable shall be plugged into the box.From this box separate yokes shall lead to the winches.
The central control box, if fitted, shall include the following features:
(a) Socket-outlets for winches.
(b) An emergency stop button.
(c) A power-on light.
(d) A Type I or Type II residual current device complying with AS 3190.
The control box shall be fully enclosed, lockable, shatterproof and weatherproof. It shall be removable for safetyand security but at the same time shall be securely attached to the guardrails of the cradle on the side away fromthe building face when in use.
5.3 CONTROLS The hoists shall be operated at the hoist, from a central control box, or by the use of pendantcontrols within the cradle in accordance with AS 1418.1.
All operating buttons and levers shall be of the spring-loaded ‘dead-man’ type.
The electrical control system shall be designed so that any electrical failure or malfunction would cause thesystem to fail to safety. Protection shall also be provided against phase reversal in 3-phase systems.
5.4 ELECTRICAL CABLES Electrical cables shall comply with the following requirements:
(a) Electrical cables shall be purpose designed.
(b) Cables shall only be suspended from a device that does not damage the core wires. A built-in thimble is oneform of such device.
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