Of for the safe erection and use of scaffolding

8.3.4 OUTRIGGERS (NEEDLES)Design: It is sound and accepted engineering practice to use either steel oraluminium outriggers to support mechanical powered swinging stages. Forhand haulage, swinging stages and boatswain’s chairs, either metal or timberoutriggers may be used. The structural design used for outriggers must bebased on and conform to the appropriate New Zealand Standard.(a)For a swinging stage with two points of suspension, each outriggermust be designed to carry half the dead load of the working platformincluding hoists, etc. together with the full live load due to personsand materials as these loads are capable of being positioned at eitherend of the stage (see example in Appendix B2).(b) For a swinging stage with more than two points of suspension, eachinterior outrigger must be capable of carrying the full dead and liveload for each section between suspension points.Unless specifically designed by a registered engineer, each outrigger for amechanically-operated swinging stage must be:(a)(b)At least equivalent in strength to a 152 mm x 89 mm x 17.09 kg/mrolled steel joist when suspending a maximum load of 400 kg.At least 3.6 m in length when counterweighted.(c) Located so as not to project more than 1.5 m beyond the outer point ofsupport on the building or structure.The load exerted by an outrigger on a roof structure or parapet must bedistributed by providing adequate packing at its points of support, i.e. at theouter or fulcrum end, and the inner or counterweighted end.Stability and Counterweighting: Outriggers must be either counterweightedor secured to the building or roof structure by bolts or other structural fixing.Where an outrigger is stabilised by counterweights, the factor of safety againstoverturning must be at least 3 (see Appendix B for a method of calculatingcounterweights required).Where roof fixings are relied upon as the sole means of achieving stability,they must be capable of providing a factor of safety of 3 against uplift.Roof fixings shall be designed according to the stresses appropriate to thematerial. No component in the system must be loaded to more than themanufacturer’s recommendation.Outriggers must be prevented from rolling over or moving laterally due to theend movement of the stage. Where counterweights are used to providestability, they must be firmly attached to the outriggers by mechanical meansso that they cannot become accidentally dislodged due to any work or weathercondition.When strops are used, these must be positively secured to the outriggerswhich must be provided with stop ends. Shackles must be moused.Where counterweights are to be used behind parapets, etc. for direct securingto the top block strop, there must be sufficient weight to prevent movementwhen the stage or chair is subjected to shock-test loading. The weights shouldbe positively secured one to another and to the strop and should be of asuitable size in relation to the parapet.56 SAFE ERECTION AND USE OF SCAFFOLDING