Hangers
Risks
Hangers can be dislodged unexpectedly due to contact with ropes , contact with branches or when the tree is moved during tree work .
A hanger ( or widow maker ) occurs where a branch or tree part has failed or been cut off and become caught or suspended within the tree .
Hangers can be dead or living branches , and can be completely detached or still partially attached to their original union .
While some hangers can become securely lodged and stay suspended for many years , others may become easily dislodged whilst installing lines or moving through the tree . Any branch which has been cut off by the arborist before their injury but has remained in the tree should be treated as a severe hazard when planning a rescue .
Hangers can fall unexpectedly and hit ground workers or rescue climbers . Hangers will hit and slide down ropes to injure climbers .
Control measures
Use pulling ropes or throwlines to pull down hangers before working under the tree .
With large hangers , access tree on ‘ safe side ’ and secure the hanger to the tree structure using ropes or slings whilst working in the tree .
Always work on clearing hangers before conducting work underneath .
Hollows and cavities
Risks
Hollows may be a weak point in the structure of the tree .
A hollow or decayed section may reduce the structural integrity of the tree at that point .
Look for signs of woundwood or adaptive growth - smoother , ‘ rolled ’ wood around the cavity - if there is a lot of adaptive growth it can be a sign that the cavity is old , and the tree may have put on additional wood to compensate ( see image ). Hollows where there is no evidence of swelling or adaptive growth may fail at unexpectedly low loads .
Hollows where there is no evidence of swelling or adaptive growth may fail at unexpectedly low loads .
Control measures
Investigate extent of hollow and integrity of residual timber .
Conduct load and pull tests to simulate working loads on the structure .
Avoid applying load to the stem containing the hollow .
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