MIS303 Tree Dismantling 2nd ed.

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This book is one in a series of Minimum Industry Standards produced by Arboriculture Australia Ltd and the New Zealand Arboricultural Association in consultation with the national arboriculture community in both countries. These industry peer-reviewed documents provide a ‘body of knowledge’ which is shared by practitioners and can be used as the basis for training, dissemination of skills and professional development. 


This standard covers the basics of tree dismantling, including rigging techniques, the use of a chainsaw in trees, and some fundamental concepts of rigging forces and rigging system design. 


Information on equipment inspection, site setup, pre-start checks, tree inspection, rope use, knot tying, the operation of chainsaws, tree felling and tree access is contained within the appropriate MISs for those work tasks.


Contents


1: Preparing for tree removal

  • Introduction to tree rigging and dismantling


Arriving on site

  • Scope of works


Preparing to remove trees – site setup


Tree removal strategies


Tree inspection for dismantling

  • Hazard control measures for tree dismantling


Basic rigging concepts

  • Parts of an aerial rigging system


Selecting and inspecting rigging equipment

  • Rigging equipment: general concepts and terminology 

  • Rigging equipment inspection checklist


Aerial rigging systems

  • Common components of a rigging system

  • Selecting anchor points in trees – tree strength and structural integrity

  • Fixed rope anchor points – attaching a rope

  • Running bowline

  • Round turn with 2 half-hitches

  • Main attachment knot plus half-hitch

  • Clove hitch with two half-hitches

  • Cow’s hitch with better half

  • Timber hitch

  • Karabiner

  • Karabiner and sling

  • Shackle or similar connector

  • Other fixed-rope attachments

  • Moving rope anchor points

  • Natural crotch

  • Block, rigging block, impact block

  • Pulleys

  • Rigging rings

  • Moving rope anchor point attachment components

  • Sling, tape sling, tube tape sling

  • Loopie sling

  • Whoopie sling

  • Dead-eye sling

  • Other anchor points and attachment options

  • Rope brakes

  • Trunk wraps

  • Wraps in tree

  • PortaWrap or similar floating friction brake

  • Bollard, drum or similar


Rigging equipment configuration and proper use

  • Example of misconfigured rigging equipment


Designing a rigging system 

  • Rigging system design considerations

  • Estimating weight of sections

  • Tree species density table


Introduction to forces in rigging

  • Different loads on components in rigging system


2: Dismantling trees 

  • Performing works


Communication during tree work

  • Call-and-response protocol

  • Hand and whistle signals for use on tree sites


Using a chainsaw in trees 


Cut sequences and techniques – branches

Straight back cut 

  • Step cut – undercut made first – top cut inside

  • Step cut – undercut made first – top cut outside

  • Step cut – top cut made first

  • Step cut – lateral cuts

  • Scarf and back cut – downward

  • Scarf and back cut – upward

  • Box cut


Cut sequences and techniques – tree heads and timber

  • Falling the head out of a tree

  • Falling sections of timber

  • Falling sections of timber – landing sections flat

  • Cutting techniques where trunk diameter is greater than bar length

  • Blocking down: step cuts on timber


Falling techniques for tree dismantling – use of wedges and taglines 


Rigging operations 


Rigging attachment point: cut and behaviour 

  • Rigging upright sections

  • Rigging lateral sections or branches


Rope control during rigging operations 


Rope control: rope brakes and friction management 

  • Installing rope brakes 

  • Using rope brakes: adding tension 

  • Rope control during rigging operations – general principles 

  • Tips for using rope brakes 


Returning rigging components 


Specific rigging techniques 


Natural crotch rigging 


Applying friction at the point of cut 

  • Techniques for applying friction at the point of cut 

  • Branch removal – wraps method 1 

  • Branch removal – wraps method 2 

  • Artificial rope brake at point of cut 

  • Snatching – wraps at point of cut 


Snatching 


Minimising peak force in negative rigging 

  • Estimating peak loads in negative rigging 

  • Mass damping 


Bracing a rigging point 


Floating anchors: highlines and multiple point floating anchors


Speed line or zip line 


Running anchor rigging 

  • Running anchor rigging example 


Lifting systems 


Guying a tree 


3: Completing tree removal 

  • Biosecurity and transmission of pathogens 


Completion of works 


Appendix A: Rigging system diagrams 


Positive rigging systems 

  • Simple anchor | friction at base of tree 

  • Butt tying 

  • Tip tying 

  • Use of a tagline 76

  • Use of multiple anchor points 

  • Cradle rigging 

  • Lifting 

  • Friction applied at anchor point/s in tree 

  • Use of multiple rigging ropes – shared load or load transfer 11

  • Floating anchor 1: single floating anchor 12

  • Running anchor 1 183

  • Running anchor 2: speed line 184

  • Floating anchor 2: high line 185


Negative rigging systems 

  • Snatching 

  • Snatching – friction at point of cut 

  • Negative rigging – redirects 

  • Friction at the point of cut 1: negative branch rigging 

  • Friction at the point of cut 2: transferring loads 

  • Running anchor 3: negative rigging 

  • Vertical speed line 


Appendix B: Working the angles 


Introduction to forces 

  • Working in newtons 

  • Force, lever arm and bending moment 

  • Lever arm 

  • Force vectors at anchor points 

  • Deflection forces 

NZ Arboricultural Association​

1/23 Alma St, Buxton Sq, Nelson

PO Box 1193, Nelson 7040

04 472 6330

info@nzarb.org.nz

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