Influence of Allowances on Taking Log Deliveries
Research subject and fields:
This paper deals with differences between the declared and actually supplied volume of round wood, which can be seen in the sawmill log yards in taking log deliveries. These differences usually mean the losses for the suppliers. Authors focus on the length accuracy of supplied logs. They start with a comprehensive manual checking of log deliveries (2639 logs) and with calibration of electronic measuring equipment (238 logs) made by an accredited laboratory. Authors analyse the origins of the differences, they quantify the volume “voluntarily” given by the suppliers in the form of oversized allowances and the volume of the losses caused by classifying the logs to a lower length group if the necessary allowance lengths are not observed (the volume is counted using e.g. 1 m shorter nominal length). The term “extra allowance” is introduced for allowances longer than wanted, and the dependences among the length of extra allowances, log diameter, volume of extra allowances and number of logs with too short allowance are defined. Losses caused by both of these defects (over- or under-sized logs) are counted and compared. If the log length value is exactly the required one or close to it (it means nominal length and required allowance), the measuring equipment can still measure a lower value because of the required precision of 1 %. Losses are also caused by reclassifying the logs to a lower group. Suppliers cut the logs longer (make “extra allowances”) to ensure that the volume calculation is based on the right nominal length and not shorter. The research shows big differences between particular suppliers and their losses caused by extra allowances or reclassification of logs. The authors searched the optimum allowance in order to minimise the losses of the supplier. The results of the analysis give the following recommendations: for suppliers who do not use harvesters for felling and logging, it would be preferable to supply round timber in tree lengths due to the volume lost by reclassification. Today, however, this is not possible in most cases because large customers buy only logs because of technological reasons. Another aspect is the price, which is usually higher for raw material in logs. In the production of logs, it is preferable to increase the required 2 % allowance by 4-5 cm, if it is possible to produce the logs relatively accurately. If accuracy cannot be maintained, it is preferable to increase the allowance to about 7 cm (e.g. mountainous terrain, poor quality and curved timber, lack of experienced staff).