Numerical and Experimental Analysis of Fire Resistance for Steel Structures of Ships and Offshore Platforms

The requirements for the fire resistance of steel structures of oil and gas facilities for transportation and production of hydrocarbons are considered (structures of tankers and offshore platforms). It is found that the requirements for the values of fire resistance of structures under hydrocarbon rather than standard fire conditions are given only for offshore stationary platforms. Experimental studies on the loss of integrity (E) and thermal insulating capacity (I) of steel bulkheads and deck with mineral wool under standard and hydrocarbon fire regimes are presented. Simulation of structure heating was performed, which showed a good correlation with the experimental results (convective heat transfer coefficients for bulkheads of class H: 50 W/m2·K; for bulkheads of class A: 25 W/m2·K). The consumption of mineral slabs and endothermic mat for the H-0 bulkhead is predicted. It is calculated that under a standard fire regime, mineral wool with a density of 80–100 kg/m2 and a thickness of 40 to 85 mm should be used; under a hydrocarbon fire regime, mineral wool with a density above 100 kg/m2 and a thickness of 60–150 mm is required. It is shown that to protect the structures of decks and bulkheads in a hydrocarbon fire regime, it is necessary to use 30–40% more thermal insulation and apply the highest density of fire-retardant material compared to the standard fire regime. Parameters of thermal conductivity and heat capacity of the applied flame retardant in the temperature range from 0 to 1000 °C were clarified.

The Effects of Mineral Wool Fly Ash on Cohesive Soil Strength Behaviour

This research work represents updated results of cohesive soil strength improvement with mineral wool fly ash. In the investigations, these materials were used: Portland cement CEM I 42.5 R, fly ash obtained from a mineral wool production process, sand and clay. Mixtures were prepared as follows: dry mixing of Portland cement and fly ash; dry mixing of sand and clay; adding water into Portland cement and fly ash; adding sand and clay mixture into already prepared Portland cement and fly ash suspension. The content of fly ash replacing Portland cement varied from 0% to 40%, and the content of sand mixture varied from 20% to 60%. After 24 hours, investigated samples were taken out from cylinder forms and kept in a desiccator with a humidity of 90% and at 20 °C temperature. Uniaxial compressive strength of the samples was determined after 548 days and compared to previous research results obtained after 7, 28 and 183 days. The most predictable compressive strength is for samples, which composition is 100% cement and 0% fly ash. In these samples, the highest compressive strength was obtained, comparing them to the other investigated samples. Compressive strength change is minimal for samples with a 10–30% amount of fly ash. The most significant decrease in compressive strength was obtained for samples with a 40% fly ash after 183 days. Nonetheless, the compressive strength of these samples increased after 548 days and is almost the same as for samples with 100% Portland cement.

SYSTEM ANALYSIS OF TECHNOLOGICAL PROCESSES

The article discusses ways to solve engineering problems in the study of technological processes using methods of system analysis. The essence of this method is to study the technology as a cybernetic system with an assessment of the" reactions” of this system to external influences formed during an active experiment. At the same time, optimization problems are solved analytically. Analytical optimization is based on two main principles. The regression equations obtained as a result of processing experimental data and testing statistical hypotheses are models that adequately describe real processes. Each of these equations is an algebraic function of several variables, to which methods of mathematical analysis are applicable, including the study of extremums of functions in partial derivatives. The next step is to develop a process algorithm and develop computer programs that allow you to select the composition and predict the properties of the product. As an engineering interpretation, it is possible to construct optimized nomograms that allow solving both direct and inverse problems; that is, predicting the result or selecting technological factors. The research methods described in the article are implemented in the study of technologies of cellular concrete, foam concrete, cement-polymer concrete and products made of mineral wool and foam glass. As an example, the article considers the optimization of the selection of the composition of fine-grained concrete reinforced with chopped glass fiber. The implementation of the developed method allowed us to determine the optimal value of the determining parameters, including the consumption of fiber and plasticizer, as well as to form a method for studying the properties of products.

Thermosetting Binder for Fibrous Insulating Materials

Постановка задачи. Модернизация систем изоляции инженерных сооружений, в том числе и трубопроводов и промышленных объектов, направлена как на решение общих задач энергоэффективности, так и частных задач теплосбережения и экологической безопасности. В связи с этим разработка и применение связующего, отверждаемого при значительно меньших температурах и не содержащего фенолы, является актуальной задачей. Результаты. Эксперимент, проведенный для оценки влияния на адгезию к различным поверхностям комплексного связующего, отверждаемого в температурном интервале от 80 до 140 С, позволил определить оптимальные расходы латентного компонента и модификатора, которые составили соответственно 3,6-4,0 % и (2,6 ± 0,1) % по массе связующего при оптимальной температуре тепловой обработки 100 С. Расчетом установлено, что при переходе от тепловой обработки при 250 С к тепловой обработке при 100 С прямые затраты тепла снижаются на 60 %, а энергетические затраты на изготовление минераловатных цилиндров на 20-30 %. Выводы. Теоретически обоснована и экспериментально подтверждена возможность применения эпоксидного клея на латентных отвердителях в качестве связующего для высокопористых систем с распределением и отверждением этого связующего на тонких минеральных волокнах. Определены характеристические параметры процесса отверждения, длительность которого уменьшается с повышением температуры и содержания латентного отвердителя. Statement of the problem. The modernization of insulation systems of engineering structures, including pipelines and industrial facilities, is aimed both at solving general problems of energy efficiency, as well as the particular tasks of heat saving and environmental safety. Therefore the development and use of a binder that cures at much lower temperatures and does not contain phenols is an urgent task. Results. An experiment conducted to assess the effect on adhesion to various surfaces of a complex binder cured in the temperature range from 80 to 140 °C allowed us to determine the optimal flow rate of the latent component and modifier, which were 3.6-4.0 % and (2.6 ± 0.1) % respectively by the weight of a binder at an optimal heat treatment temperature of 100 °C. The calculation suggests that when switching from heat treatment at 250 °C to heat treatment at 100 °C, direct heat costs are reduced by 60 %, and energy costs for the manufacture of mineral wool cylinders by 20-30 %. Conclusion. The possibility of using epoxy glue on latent hardeners as a binder for highly porous systems with the distribution and curing of this binder on thin mineral fibers has been justified theoretically and confirmed experimentally. The characteristic parameters of the curing process have been identified whose duration decreases as temperature and the content of latent hardener increase.

Influence of the substrate on the yield and quality of microgreens of vegetable plants

Research on the effect of the substrate on growth rates, physiological and biochemical processes, yield and quality of lettuce, radish, mustard during the forcing of microgreens in greenhouses showed a positive result. For research, the generally accepted methods were used: laboratory, mathematical-statistical, physical. Evaluation of substrates for growing microgreens of lettuce, radish, mustard indicates that they are suitable for forcing in greenhouses. It was found that the duration of the growth phases of microgreens depends on the substrate. For lettuce, radish and mustard, the appearance of the root occurred on the second day. Greens were collected in 2020 for 8–10 days, in 2021 – for 7–8 days, which is influenced by the length of daylight hours and the ambient temperature. When growing microgreens of lettuce on mineral wool, the height of the plants was 4.48 cm.Radish and mustard had the tallest plants when grown on coconut substrate – 6.36 cm and 6.78 cm. The mass of 1000 pcs. plants is an important trait, which in turn determines the quality of microgreens. Maximum weight 1000 pcs. when grown on a coconut substrate, lettuce – 13.75 g, radishes – 69.61 g, mustard on mineral wool – 35.58 g. A high yield of leaf lettuce during the years of research was obtained when grown on a coconut substrate – 1.62 kg/m2, which significantly exceeded the control by 0.1 kg/m2. A high yield of radish was obtained when grown on a coconut substrate – 5.41 kg/m2, which significantly exceeds the control by 3.83 kg/m2. The mustard yield when using coconut substrate was 4.90 kg/m2, which is 3.38 kg/m2 higher than the control. Correlation analysis proves that for all the studied plants at the time of harvest, there is a direct strong relationship between the mass and its height, and its coefficient is r = 0.98.