Fulltext search in archive

Selected anticorrosion preserving agents were subjected to a comparison on the basis of tests made under operating conditions. Resistance of materials to corrosion markedly varies with operating conditions and impact of outer environment with the most important factors influencing the corrosion rate being SO₂ content, temperature and humidity. Relative protective efficiency of preserving agents was assessed on the basis of weight losses of protected and unprotected samples. It was found out that the material's resistance to corrosion is significantly depending on warehousing conditions (SO₂, temperature, humidity, etc.) and on the quality of the applied preservant. Depending on various environments, the values of relative protective efficiency of water-soluble preservant and preserving agent based on vegetable oils were ranging from 38-87% and 47-75%, respectively.

The cost modelling for growing and harvest of selected energy crops and further costs for recommended forms of energy crops processing to biofuels was conducted. Importance and effect of subsidies on resulted costs for biofuels production was assessed. The result are then total costs per unit of fuel weight which range from 469 to 1,806 CZK/t for biofuels processed to form of chopped material or pressed bales and from 881 to 2,466 CZK/t for briquettes and pellets. The result costs per energy unit in biofuel have ranged from 59 to 121 CZK/GJ. On basis of economical data is evaluated the biofuels competitive power in comparison with main competitive fuels on market. The energy crops specific costs without subsidies are higher thus their position on market will be complicated, lower specific costs can be expected only when residual biomass would be utilised (grain straw). The competitive power of the energy crops will be much better as the subsidies are utilised in 2004 and total specific costs for chopped material are from 82 to 142% of brown coal price, 95-137% for briquettes in comparison with the brown coal briquettes. The energy utilisation if winter wheat and sorghum is economically unsuitable.

One of the basic demands for milking machines is to maintain a constant vacuum level if air consumption by milking machine is changed. The author designed a device with reducing valve for vacuum level regulation and a simultaneous vacuum pump control enabling electric power to be reduced. The paper deals with a comparison of the operation of standard control valves with the newly designed device used for vacuum regulation from the viewpoint of dynamic properties. When measuring vacuum stability by applying various regulation methods and a subsequent statistical evaluation of the results obtained it was proven that the function of the newly designed regulating device was comparable with the best reducing valves used so far.

The goal of the measurement of the tractor ZTS 164 45 equipped with digital electrohydraulical control EHR-D BOSCH during ploughing with ploughs KUHN (4 bottoms) and 5 PHX 35 (5 bottoms) was to obtain time dependent states of pressure in the hydraulic system of the three point hitch of tractor. From the point of view of comparison of obtained results testing conditions were determinated with respect to physical and mechanical properties of soil such as soil volume mass, soil humidity, penetration resistance and shear resistance of soil. Beyond these measurements also measurements of operation parameters as a ploughing depth, ploughing width, working speed and fuel consumption were accomplished. The measured results of physical and mechanical properties of soil show big content of loam elements and stones in the soil. Simultaneously the measured results of the operation parameters of the ploughing sets confirmed that the ploughs KUHN and 5 PHX 35 are suitable for tractor ZTS 164 45. Based on the measured results there is a possibility to infer following conclusions: Control system of the three point hitch offers a reliable function. Hydraulic circuit is equipped by an improper distributor which causes pressure peaks which are corres-ponding with safety valve adjustment. Hydraulic circuit has a low conductive resistance. Loading of tractor body is higher when using mounted plough than with semi mounted plough.

Approach to the problems of sugar-beet tubers surface damage dependence on harvesting technology. Investigation of sugar-beet tubers damage when falling on wood and iron surfaces and in the next case tuber damage caused by their fall on the tuber heap. Research of damage rate dependence on the fall height. Evaluation of damage rate was carried by the I.I.R.B. method (method used by all sugar-beet growing countries of Western Europe). The results refer that no considerable differences in damage rate after the fall on the wood or iron bottoms have been ascertained. The height of 1.5 m can be considered in all cases as the limit value of the tubers fall, when share of heavily damaged tubers reached acceptable values of 10-15%, but that the share increases significantly at higher falling height. The lifting bodies construction requires also a knowledge of dependence between root depth and force for tuber release from soil in relation to the tuber weight. Medium force needed for tubers lifting ranges from 17 to 27 kp, maximum value 50 kp was found out for tubers of weight above 3 kg.

In the paper are presented results of grain outer quality loss investigation during its post-harvest treatment. Objective was to determine the grain damage during its transport by bucket elevators of type "SANFON" at bucket peripheral velocity 2.0 m/s and 2.8 m/sof capacity 40 t/hand 80 t/h, respectively. The damage was investigated at counter-flow and parallel-flow bucket filling. From the measured results resulted the conclusion, that the bucket elevators tend rather to grain crushing, i.e. fraction creation than to smaller damage. On basis of partial knowledge chain elevators have no significant tendency to fraction generation, but incline considerably to the transported grain total mechanical damage at performance significantly lower than is the nominal one. In that case total mechanical damage ranged from 1.78 to 1.98%. Auger conveyers tend rather to total mechanical damage of transported grain than to the fraction creation. This is caused mainly by the friction between the transported grain and transporting "trough". Total mechanical damage is in range from 1.36 to 1.73%. Belt elevators are friendly to transported grain and therefore are evitable for grain horizontal transport in lines for reception, treatment and storage of food grain crops.