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Bowtie risk templates

Bowtie — Fall from Height on Steel Erection

Construction bowtie for operatives working 12 m above ground on open steel: 4.3 exposures a year reduced to 0.49 falls, ranking the PASMA-trained tower assembler above the safety netting and flagging its green handover tag as uncontrolled.

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Fall from height — steel frame erectionHAZARDOperatives working 12 m above ground on open steelTHREATSPREVENTIVE BARRIERSRECOVERY BARRIERSCONSEQUENCESEdge protection removed for acrane liftPermit to remove signed bythe site agentSafety netting rigged onelift below the face85% · mitigationPermanent edge protectioninstalled before decking70%Fragile surface surveymarked on the daily brief60%Crawling boards at everyroof light75%Tag left green after a partialdismantlePASMA-trained assemblerwith a handover tag70%Pre-use inspectionrecorded in the site diary45% · detectionTwin-lanyard harnessclipped to a rated anchor70% · mitigationRescue plan with a trainedteam on site40% · recoveryAir bag deck under theerection zone60% · mitigationSite first responder, airambulance in 15 min45% · recoveryIndependent temporaryworks inspection weekly35%Unprotected leadingedge during decking1.5/yr → 0.0675/yrFragile roof lightstepped on duringsurvey0.6/yr → 0.06/yrMobile towerincorrectly assembled2.2/yr → 0.363/yrFatal fallsev 5 · risk 0.4415Life-changing spinalor head injurysev 4 · risk 0.4316HSE prohibitionnotice halting theprojectsev 2 · risk 0.6377Operative fallsfrom theworking level0.4905/yrtop-event frequencyTop event0.4905/yrinherent 4.3/yrResidual risk1.51inherent 47.3Risk reduction96.8%threat side 88.6%Barriers113 threats · 3 consequencesDominant threatMobile tower incorrectly assembled74% of the top eventResidual risk 1.51 against an inherent 47.3 — the barriers remove 96.8% of it. 2 things are probably not what was meant — every path and every escalation factor was check…Barrier criticality — residual risk if that one barrier were removed1. PASMA-trained assembler with a handover tag+2.61 ×2.72. Safety netting rigged one lift below the face+1.18 ×1.83. Twin-lanyard harness clipped to a rated anchor+1.03 ×1.74. Pre-use inspection recorded in the site diary+0.9148 ×1.65. Air bag deck under the erection zone+0.6475 ×1.46. Crawling boards at every roof light+0.5544 ×1.4FindingsConsequence "HSE prohibition notice halting the project" rests on ONE barrier. Defence in depth is the claim a bowtie is drawn to make, and a single barrier is a single point of failure: the day …Escalation factor "Tag left green after a partial dismantle" degrades barrier "PASMA-trained assembler with a handover tag" and nothing is holding it off. The 70% credited to that barrier — and e…Each of the 3 consequences is credited the full top-event frequency of 0.4905/yr — the model here is that one top event produces all of them, so the residual score of 1.51 adds 3 outcomes to one …

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title "Fall from height — steel frame erection"
hazard "Operatives working 12 m above ground on open steel"
top "Operative falls from the working level"
unit "/yr"

threat "Unprotected leading edge during decking" likelihood: 1.5 {
  barrier "Safety netting rigged one lift below the face" effectiveness: 0.85 type: mitigation
  barrier "Permanent edge protection installed before decking" effectiveness: 0.7 {
    escalation "Edge protection removed for a crane lift" {
      control "Permit to remove signed by the site agent"
    }
  }
}

threat "Fragile roof light stepped on during survey" likelihood: 0.6 {
  barrier "Fragile surface survey marked on the daily brief" effectiveness: 0.6
  barrier "Crawling boards at every roof light" effectiveness: 0.75
}

threat "Mobile tower incorrectly assembled" likelihood: 2.2 {
  barrier "PASMA-trained assembler with a handover tag" effectiveness: 0.7 {
    escalation "Tag left green after a partial dismantle"
  }
  barrier "Pre-use inspection recorded in the site diary" effectiveness: 0.45 type: detection
}

consequence "Fatal fall" severity: 5 {
  barrier "Twin-lanyard harness clipped to a rated anchor" effectiveness: 0.7 type: mitigation
  barrier "Rescue plan with a trained team on site" effectiveness: 0.4 type: recovery
}

consequence "Life-changing spinal or head injury" severity: 4 {
  barrier "Air bag deck under the erection zone" effectiveness: 0.6 type: mitigation
  barrier "Site first responder, air ambulance in 15 min" effectiveness: 0.45 type: recovery
}

consequence "HSE prohibition notice halting the project" severity: 2 {
  barrier "Independent temporary works inspection weekly" effectiveness: 0.35
}