Felling Operations
Author: Ruan Malan
Felling is the process of individually cutting down trees for a wide range of reasons. Reasons within the forestry industry include silvicultural and production thinning, to increase health of remaining trees, as well as clearfelling, removing every tree in an area.
Felling operations are done in these three ways;
Motor-manual– chainsaw
Machine-assisted – chainsaw with machine assistance with felling direction
Mechanised – completed by machine
Felling cuts
To fell a tree a cut has to be made. All felling cuts have these 3 components [4]:
Scarf – Controls falling direction
Backcut – Allows tree to fall
Hingewood – Increases safety of fall
Different combinations of those three components in terms of, length, height and depth, allow for multiple unique cuts. A trained feller is able to select the best combination to allow for a safe procedure which is still time effective and material efficient. Changing the type of scarf used is the easiest way to alter the felling cut, Every type of scarf has its speific uses and advantages. The alternative scarf cuts according to Competenz (2005) are:
Felling Cut Diagram
Vee scarf
Reduces the amount of sloven when butting-off
Swedfor scarf
Should only be used for softwoods less than 40cm in diameter, otherwise
can be dangerous. As the scarf is more open, it prevents unneeded damaging of the hingewood.
Humboldt scarf
Reduces butt (end of tree) waste when felling on steep ground. Also improves the ease of processing the log in the cable logging operations.
Scarfs
Safe Mechanisesd Felling Process
A safety guide was developed by Competenz (2005), with similar themes displayed in SafeTWorks (n.d.), in response to the number of workplace fatalities involved in the industry. In 2013 alone, ten people lost their lives in the forestry industry, most died within the felling process. Since 2010, 25 people have died within the industry and 867 people were reported to have suffered serious harm [1]. However, the true values are expected to be higher as some indicents are not reported. The guides and code of conducts are constantly being reviewed and updated, to help prevent the unnecessary deaths occurring.
Following is an adaptive, yet detailed process outlining the safe mechanised tree felling procedures designed by Competenz (2005):
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Initial Safety Procedure:
1. Clear scrub away from around tree for better vision and to avoid machine damage.
2. Remove lower branches on stem if necessary.
3. Assess tree lean and crown weight.
4. Decide where tree will be felled.
5. Approach tree from the side away from the lean.
Safety Considerations
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Machine Preparation:
1. Determine distance from the machine to the tree being felled. Overreaching reduces the machine’s power in the boom and arm, and reduces stability. Being too close can mean that the boom is at full lift when the dipper arm is brought in close, reducing the ability to control the tree after it is severed.
2. Grasp the stem in the felling head.
3. Fine tune the positioning; place the head as low on the tree as possible to ensure a low stump.
4. Check the head is in the correct position for the desired felling direction.
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Felling Procedure:
1. Tighten grasp on tree.
2. Place some push tension in the stem.
3. Make the felling cut in a single smooth cut.
4. Whilst cutting push the tree in the direction of required fall, avoiding upward pressure.
5. Once the cut is complete allow the saw to retract.
6. Check that the saw has returned before moving the tree.
7. A small amount of upward lift may be required as the chainsaw completes the cut. This will keep the cut open and avoid jamming.
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Gathering
1. Lift the stem away from the stump when the cut is complete and the saw is retracted.
2. Swing the tree to the bunch position when the fall is complete
