Archive for December, 2010

Vegetation Management – Using the Mis-Match Cut to Free Hung or Snagged Trees on Power lines.

Saturday, December 4th, 2010

During and following severe storm events there is often a need to cut trees, remove large limbs and other debris off the power lines in order to begin the power restoration process. This work is often performed during the storm event or in conditions that are challenging due to weather, darkness and other factors. It is a known fact that working with a chainsaw is one of the most dangerous work procedures any worker can face, compound this with inclement weather and darkness and there is a potential for serious worker injury to occur.   

 Often the workers called on to perform these tasks are power linemen who may have received little specialized training in the skills needed to ensure their safety while working in these situations. Some time ago, while I was providing some basic chainsaw training for a utility client, I asked the student/lineman when they most likely used a chainsaw. Their answer was during or after storms to clear the lines in order to restore the power service. I knew the training we were there to provide did not cover this aspect of tree cutting and as a result, we developed and delivered a specialized curriculum to help lineman meet these challenges safely and efficiently.   

 Since then we have refined and developed techniques that help linemen cut trees and remove branches and debris from power lines. The most common risk that lineman take when cutting trees from the line is that they are typically standing too close to the cut, the line and the tree part when it is released. The review of logging accidents and fatalities indicate that when a cutter is within five feet of where the cutting and release takes place 90% of the accidents and fatalities occur.   

 It was with this in mind that we teach linemen how to use cutting techniques that allow the worker to be at a safe distance away when branches or trees are released. We can teach these techniques by using simple equipment already available and familiar to lineman. It is important that a lineman understand the severity of risk that exists when they are cutting trees hung on power systems.  Linemen already clearly understand the threat of electrocution.  It is the reactive forces of the chainsaw and trees that is most often not a part of the curriculum of most utility apprenticeship programs.   

 Training that teaches the correct techniques for basic tree cutting is necessary for linemen who cut trees on or near the power system during or after storm events in order to support and document due diligence for their occupational health and safety protocols. Documented training and qualification in techniques that provide options that can accommodate a variety of situations or scenarios addresses the problem and ensures diligence. In many cases linemen perform this work based on trial and error and the younger workers rely heavily and often solely on the experience of the seasoned journeyman lineman who often have learned the lessons the hard way. This leaves everyone exposed and at risk for a preventable and negligent inevitability.  If you have linemen or workers who perform these tasks, be sure that documentation of training and records exist that show your organization addresses the specialty situations posed by trees, tops or large limbs hung on the power lines.   

 Here is an example of a very simple technique that allows a cutter to be at a safer distant from a cut when it is released. In other words, it allows the cutter to be already away and in an escape route.  

Mis-match cut

 The mis-match cut or by-pass is a very simple and effective two-cut process that employs wood fibre strength to the cutters advantage. In addition by employing the use of a hand line, a common tool linemen use regularly, any lineman can cut a snagged or hung tree part and release it using the hand line from a safe working distance. Often one or two cuts will free the problem from the line allowing power restoration to commence.  

Making a mis-match cut

 This technique places the cuts in a staggered manner with the lowest of the cuts made in the direction of the intended pull. Attach the hand line to the tree part prior to commencing cutting. The cuts are made just pass half or through the mid way point of the diameter of the tree or branch. It is very important that the cuts are perpendicular to the force of gravity acting on the wood. Equally important is that both cuts bypass each other. The laminated strength of the wood fibres is strong enough to resist breaking, allowing time for the cutter to retreat and pull the piece free with the hand line at a safe distance. The pull of the hand line causes the kerf to close and the vertical wood fibre to release. 

If a mis-match / by-pass cut is unable to be released by pulling, the next option is to insert wedges into both kerfs and drive these wedges alternately until a small crack appears or any cracking or fracturing sound is heard.  It is very important that as soon as a crack is seen or heard that you stop driving the wedges and proceed to a safe distance.  In most cases pulling on the line at this point will release the snag.  Repeat the process as necessary.  

 The primary advantage of using this simple technique is that it allows the cutter to release the tree part at a safe working distance from falling debris, loaded power lines, flying branches or while holding a running chainsaw.  This technique is one of the most popular and is appreciated by linemen who have performed the work I have been describing. They recognize and appreciate the safety advantage this method provides and comment on how they wish they had learned it earlier in their careers. A short  2-3 day course can provide simple and effective work procedures that will improve linemen health and welfare while cutting trees from power lines during or after storm events in order to restore power to customers efficiently and safely. 

  The work many utility workers perform during or after storm events is not basic or ordinary. When called upon they enter an arena of risk seldom faced by many seasoned chainsaw workers – it makes sense that they receive training and education that provides the skills needed to face this dangerous work environment. 

  Dwayne Neustaeter