Detektor på skördare för utsortering av träd med metallskrot
Fortifikationsverket which is the landlord for the Swedish national defence has a great problem in their forestry due to the relatively large amount of metal objects in their timber. These metal objects cause different types of economical losses in the timber refinement chain. To enable out sorting of logs containing metal objects already in the harvesting phase, Fortifikationsverket is interested of the possibility to utilize some type of metal detector in a harvesting head for that purpose.The goal of this study was to, with help of a case study, enlighten the problem that metal objects in timber cause for Fortifikationsverket and their customers of timber and to investigate conditions of to mount and utilize some kind of metal detector in a harvesting head at present.The saw timber deliveries by Fortifikationsverket during the time period 2003-2005 was used as a reference volume for calculations of economical losses. In this case study was included two sawmills where timber from Fortifikationsverket were delivered to for further refinement. Factors investigated were the type of damage metal objects caused in these two sawmills and the economical signification of these damages. Even the harvesting and managing of Fortifikationsverket´s timber in areas where trees contained relatively much metal objects and the harvesting procedure was investigated by interviewing entrepreneurs. Further, the possibilities to use some type of metal detector on a harvesting head for out sorting logs containing metal objects were investigated by interviewing scientists and specialists and by literature searches.The interval of damage costs for the sawmills included in this case study was approximately 14 000 ? 433 000 SEK. The economical scope for a metal detector amounted to approximately 130 000 SEK for the reference volume when only economical losses due to metal objects in connection with harvesting and transport where taken into consideration. Electromagnetics, X-rays, microwaves and ultrasound are methods which could be used to detect metal objects in timber. The tough environment provided by the harvesting head and the harvesting technique it self precludes a practical usage of these methods at present, but it could be theoretically possible with the aid of microwave technique.