HARVESTER HEAD DAMAGE
Transcription
HARVESTER HEAD DAMAGE
HARVESTER HEAD DAMAGE WHAT IS THE COST? A GUIDE to ASSIST OPERATORS to MINIMISE VALUE LOSS HARVESTER HEAD DAMAGE WHAT IS THE COST? Prepared for SWI LIMITED by Don McConchie - Wood Quality Focus CONTENTS PURPOSE OF THE GUIDE 2 INTRODUCTION 2 CHARACTERISTICS OF LOG DAMAGE 3 LOG DAMAGE ASSESSMENT TECHNIQUE 8 CHARACTERISTIC DAMAGE IN SAWN BOARDS 11 VALUE LOSS 17 BASELINE DATA 18 HOW CAN OPERATORS MINIMISE HARVESTER HEAD DAMAGE? 20 CONSEQUENCES 22 CONCLUSIONS 24 Further Reading 25 Acknowledgements 25 Disclaimer: This Guide is intended by SWI as an 1 2 PURPOSE OF THE GUIDE This guide has been produced to help raise is presented to standardise damage assessment INTRODUCTION With the emphasis on safety and the increasing training can minimise damage, the severity of damage - logs with large branched whorls directly above the pruned log are more likely to be damaged to a greater extent, and/or less well maintained machines and the capacity for adjustment of feed industry to be able to readily determine the severity of damage and establish a link to value CHARACTERISTICS OF LOG DAMAGE Firstly incisions of various shapes (straight, thumbnail, spike or pineapple) generally to a depth up to 3 cm caused by the drive roller teeth, and tears or gouges caused when the stem stops moving through the harvester head when the depth of damage is measured, to the two faces of contact along the length of 3 4 the log and are usually <1 cm deep, although at rerun to remove a large whorl above the pruned rollers is classed as Low or occasionally Moderate Low the teeth incisions, more localised and is usually This deeper damage can occur when the harvester head jambs, for example and most commonly at a large whorl at the top of the pruned log causing the delimb knives to gouge The stem must be passing through the harvester measurement the knives can gouge towards the log can also occur when a grapple grabs the type of damage accounts for many Moderate Severe Moderate. 5 6 Moderate. Moderate. Severe. Damage which is generally bruising and incisions to the surface and immediate subsurface of log damage therefore results in the loss of high clearwood, along with the normal level of wane when ripping to width or docking, will reduce 7 8 LOG DAMAGE ASSESSMENT TECHNIQUE each log is assessed for the depth of damage <1 cm Low, 1-3 cm Moderate and >3 cm Severe To measure the depth of damage a normal single plane screw driver was used with coloured into damage marks either roller teeth incisions tape boundary), and The split of <1 cm and >3 cm was arrived at large data set of measured logs showed very is the depth of damage generally allowed in the more numerous and lesser depth of damage harvester head damage has not previously been number of logs may in fact be worse than Low be Moderate or Severe and a Moderate Severe The next series of photos show the high level of bark removal and the presence of grit on the log surface and within gouges typical of removal is seasonal in nature with less removed during the winter period of dormancy or Low and Moderate 9 10 Moderate CHARACTERISTIC DAMAGE IN SAWN BOARDS For the study to develop the log assessment face boards transferred from the mill prior to ripping which could have removed much of the damage along with the wane, and docking each board was then assessed by measuring the width if correctly ripped for wane and what the width would need to be reduced to, to remove to board feet using the appropriate measuring In the studies undertaken, the percentage loss of Clears ranged from no loss for 5 logs to a maximum 35% loss for a log classed as Severe A greater depth of cut occurs at the large end due to normal log taper and hence considerable 11 12 Boards can also show signs of damage but log The following photographs show examples of typical harvester head damage on boards loss of Clears Low 13 14 15 16 VALUE LOSS A number of factors contribute to loss of value - log diameter and shape, and within batches of logs the loss of Clears for opening face boards could fairly be regarded as 5%, 10% and 24% for Low, Moderate and Severe a 200 mm opening face cut then for every 1 cm depth of damage over and above the normal Clears When a millgate price for Clearwood of $700/m3 was used, the loss in value/m3 of logs processed Low Moderate and Severe Note: 17 18 BASELINE DATA Applying the this Guide, a sample of 1125 logs were assessed at mills and logging sites in both the North and logs, the majority of logs fall within the Low severity class (69%) with a similar breakdown of producing the Tenon pruned logs was unknown, but assumed to be variable as logs from a wide only 2-4% of logs were assessed as Severe Where the volume of pruned logs processed by harvester heads is known, results indicate there 3 19 Kaituna Nelson Taranaki Tenon TOTAL Location 69 68 78 70 62 3 2 4 4 3 29 20 26 34 28 Percentage of Logs by Severity Class Low Moderate Severe Harvester Head Damage Assessment by Log Severity Class 337 272 154 362 1125 No. of Logs 20 HOW CAN OPERATORS MINIMISE HARVESTER HEAD DAMAGE? In discussion with machine harvester manufacturers and operators within the trained on all aspects of the use of a - carry out regular and any other maintenance as and when it - when replacement or recommended by the appropriate - only run the head down the tree to length, every pass of the harvester head over the stem creates damage even if only - delimb knife pressures to be set correctly, use the “knife pressure based on - delimb knife edges to be correctly sharpened, excessively worn knives should Drive rollers - wear to be monitored, and - drive roller close pressure to be set - to be entered correctly into the harvester head computer and all sensors and encoders to be calibrated accurately this will avoid unnecessary reversing on the the stem to achieve “Find End” sensors - must be used before undertaking any form of log making or length bucking, to avoid unnecessary “biscuit “ 21 22 - trained operators can listen to the machines they operate and The result of worn feed rollers is that the physical length of the teeth decreases and the the stem and gouging if the reason for slipping is incidence of Moderate and Severe Excessive pressure will cause deeper tooth Moderate and Severe Running dull delimb knives usually does two This may increase the chance of Moderate the harvester head with constant stopping head thinks the diameter is larger than it actually is, it will apply excessive pressure while This also applies in reverse when the diameter is actually larger than calibrated, lower pressure increase in Moderate and Severe 23 24 CONCLUSIONS By using the suggested standardised assessment data from across the industry to monitor similar machines due to harvester head damage to be more FURTHER READING Grapple processor ACKNOWLEDGEMENTS Jason Huitema at Waratah and Chris Hancock at Woodsmanpro for their advice regarding We also thank Bernie Schluter at the Kaituna Mill for organising access to logs for assessment, and Graeme Young and Derek Gwynne of Tenon for access to logs for assessment and assistance 25