Granulometry of selected wood dust species of dust from orbital sanders

Formation and presence of dust in the timber premises is part of the technology. Dust is generated as a byproduct based on the method of machining. The paper deals with granulometric analysis of selected samples of wood dust sessile oak (Quercus petraea Liebl.) and from deciduous multiple-pore wood there was chosen European beech (Fagus sylvatica L.) and alder (Alnus glutinosa L.) and the mixture taken directly from timber production of grinders SCM SANDYA 300RCS) for the purpose of selecting the percentages of the various fractions (0.032; 0.063; 00:08; 0.125; 0.250; 0.5; 1; 2 mm) of samples of wood dust. Wood dust samples were made using a hand orbital sander BOSCH PSS 200AC and sizing on the automatic mesh vibratory sieve machine Retsch AS 200 control. The most frequent percentages of dust particles (between 50-79 %) in all samples of wood dust there were fractions of 32 and less than 32 μm (bottom). The most abundant percentage creates conditions of the risk of inhaling and respirable components contained in the fraction over 32 μm and the potential of formation of a dust-air explosive mixture. Comparison of results granulomertic fractions contribution of wood sanding dust typically processed wood in the furniture industry (beech, oak, spruce, fir, and alder) was significantly confirmed of the particle size.

Parameters of the laboratory model terrestrial forest fire created from the needles of pine (Pinus nigra)

The work deals with the monitoring of selected parameters in the model of terrestrial forest fire, which originated in forest litter (natural challenged material). A needle of black pine (Pinus nigra) was used as a fuel. For the model there was developed forest fire apparatus – wind tunnel, which simulates terrestrial forest fire on the basic model Superior Técnico in Lisbon (Portugal). In the apparatus, there is possibility to placing a sample on the basis of changes of coniferous litter and regulate the speed of the airflow over the layer of litter. The work reviews the effects of air velocity depending on time and temperature of coniferous leaf litter on the wind tunnel and the speed of flame propagation along the coniferous litter layer. In the article, there are original work results which show a significant effect of air flow over the surface of coniferous litter on a fire and the flame propagation speed after layer of litter. Threshold limits of the flow rate of air are in the range <0.5 m.s-1, 1.0 m.s-1>, in which there is an increase in linear speed of the spread of fire of 2 to 2.5 times. Subsequently, the linear speed of spread for models of terrestrial forest fire appeared significantly comparable at air speed 1.0 cm.s-1 and 2.5 cm.s-1. But time which shows spread of fire at specified speed has been reduced by 60% from the time of fire development at a speed of 0.5cm.s-1.