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The article presents the results of a study on the quality of conical picks for the purposes of tender procedures in accordance with the public procurement law in Poland. The pick studies presented here are one of the few that in practice allow the selection of an offer based on objectively determined numerical indicators defining the quality of the product and not only on the basis of price. Thanks to this, the contracting party can decide the relevance of price and quality in their evaluation of a pick. The geometrical and material parameters required in a tender, if not met, are the basis for rejecting a given offer of picks. The numerical parameter influencing the final evaluation of the offer is the picks’ rate of wear. Conical picks are tools for mining minerals, rocks, asphalt or concrete. They are used in many industries, especially in mining, construction and road engineering. In difficult working conditions, the durability of knives is limited to as little as several hours. Several dozen picks work on a cutting unit at the same time, and taking into account the price of a knife which oscillates around several dozen euros, significant operating costs are incurred. Therefore, the selection of tools with an optimum price-quality ratio is crucial. The article presents the results of studies on geometric parameters, material parameters and the rate of wear of 48 sets of picks conducted for a tender consisting of 14 tasks. The tender was conducted for 6 underground mines of a coal company. Five producers submitted their offers for selected tasks in the tender.
Generally, the choice of cutting attachment used in brush cutters for brushwoods and grasses depends on the type of work, on one hand, and the size of the engine, on the other. However, at the same time, the use of individually chosen cutting elements entails a certain risk of vibration resulting from their varying design and size, which has a big impact on comfort and working time, but most importantly on operator health.
The aim of the study is a preliminary analysis of the dangers due to vibration of brush cutters and to determine how the choice of the cutting attachment affects the intensity of the vibrations emitted by the machine. Furthermore, one aim was to determine the daily vibration exposure, relative to an equivalent value of vibration, experienced by the device operator.
This study involved four models of brush cutters with three machines of each model, differing in size (displacement and engine power) and equipped with six different cutting elements. A vibration acceleration test was carried out in accordance with the applicable PN-EN ISO 5349-1 and 2: 2004 and Directive 2002/44 / EC.
An analysis of the obtained results leads to the conclusion that the examined professional brush cutters emit vibrations of such intensity that the daily exposure limit (5 m s−2) is exceeded more than two-fold. One cannot directly determine the influence on vibration intensity by the type of cutting attachment or the exhaust, but it should be noted that use of a cutting unit as recommended by the manufacturer creates less harmful vibrations, especially when the engine runs at the nominal rotational speed. In order to minimise the risk due to vibrations from brush cutters, engines with a cylinder capacity below 45 cm3 are recommended to be equipped with trimmer heads and disk knives, while engines with over 50 cm3 should run with circular saws.