Machines. Technologies. Materials.
Vol. 13 (2019), Issue 6

Table of Contents

  • MACHINES

    • Choosing a model to determine deformations

      pg(s) 245-247

      If the material from which the equipment is made is known, constant and periodic loads are known and the displacement of equipment points are measured by the dynamic model, it is possible to determine the forces that cause these displacements and deformations themselves. If the deformations are within acceptable limits, then the equipment operation continues, otherwise the equipment must be stopped to eliminate deformations; at best, deformation can be eliminated without stopping the equipment.

    • Exergy analysis of two water pumps from steam power plant at four different loads

      pg(s) 248-251

      Paper presents exergy efficiency and loss analysis of condensate extraction pump (CEP) and main boiler feed pump (BFP) from a conventional steam power plant. Based on the required measured operating parameters at four different loads, it was observed that an increase in driving power for both pumps follows an increase in power plant cumulative developed power. Both analyzed pumps do not have the highest exergy losses at the highest observed load, as can be usually expected. Main boiler feed pump has the highest exergy efficiency, which is equal to 87.00%, at power plant nominal load, while the highest exergy efficiency of condensate extraction pump (95.77%) was observed at 60% of power plant nominal load. The influence of the ambient temperature on both pumps exergy efficiencies and losses is almost negligible.

    • Development of theory of the drive of stationary agricultural machines with lever mechanisms

      pg(s) 252-253

      The improvement of the efficiency of agricultural machines of a modern technical level can be achieved when new methods of the theory of mechanisms and machines are used during calculations and design of their working bodies and in general of machine aggregates. The task of the research was to develop a new algorithm for solving the second problem of dynamics of lever mechanisms with electric drive, which are used in modern agricultural machines A new algorithm for solving the second problem of dynamics of lever mechanisms of agricultural machines equipped with an electric drive has been developed. The algorithm finds application in calculations of flat lever mechanisms of stationary agricultural machines.

    • Equipment for the production of a continuous band or a block of foam glass

      pg(s) 254-256

      Based on the experience gained during the creation, experimentation and study of two devices and technologies for the production of foam glass from household glass waste according to Bulgarian Patents Nos. 65718/24.11.2004 and 65745/26.05.2006, an idea was developed for a new device for which a patent application has also been filed. The basic operational concept of the previous devices is preserved, but some of their deficiencies discovered during their experimentation have been corrected.

  • TECHNOLOGIES

    • An innovative approach for repairing of corroded reinforced concrete industrial structures in aggressive environment by high-tech hybrid reinforced sprayed concrete with capillary crystalline admixture

      pg(s) 259-262

      Solvay Sodi JSC, Devnya, Bulgaria, is the biggest calcite soda production plant in Europe. It is built in 1974 and it works in three-shift production regime up to present days. The exploitation environment is highly influenced by numerous factors, acting corrosively on main reinforced concrete structures – active atmospheric processes (in continental type moderate climate), sea water born chloride-aerosols, as well chemical attack caused by carbon dioxide and nitric acid, presented in the air in form of evaporation. The most reinforced concrete structures need urgent remedial measures to restore the load-bearing capacity of its components.
      The “light soda” silos are reinforced concrete facilities (cylindrical shells) which repair has to be executed during continuous production process. The options for repair of these structures and restoration of their load bearing ability by specially designed innovative high-tech hybrid reinforced sprayed concrete, containing capillary crystalline admixture, are discussed in the report.
      The in-situ tests and wide-range comparative studies are carried out, covering basic physical and mechanical structural characteristics of the proposed sprayed concrete for wet spraying and another one – based on proportioned dry ready mix.
      The original scientific results concerning strength-deformation properties, phase composition and structure of hardened sprayed concrete, directly related to the durability in aggressive environment, are obtained by X-ray diffraction (XRD), differential thermal analysis (DTA), mercury porosimetry, low temperature gas adsorption (BET-method) and computer X-ray tomography.
      The static and dynamic analysis of the structure is performed using the test results obtained and the fully specified engineering solution has been presented to restore the load-bearing capacity of the structures with a guaranteed service life of at least 50 years.

    • Quality control of multi-pass weld by means of acoustic emission

      pg(s) 263-265

      The article proposes a method of assessing the quality of multi-pass weld by acoustic emission. The AE method involves the identification of developing defects at the stage of stress changes in the material, as well as in the statically loaded state. In the process of control two independent data collection systems were used, which worked in the process of testing synchronously. The selected method of control of the object has a number of advantages over other methods of NDT.

    • Reducing the energy intensity of multi-product machinery production by improving the core production infrastructure

      pg(s) 266-267

      Multi-product machinery production forms a machine park of an industrial organization, so the finished products must provide high-quality and economic indicators while using them in productions. The problem of increasing the level of production efficiency is analysed in such organizations depending on the improvement of the basic production infrastructure. The new, quantitative indicators are presented, which help justify the interrelations of material, labor and energy production costs. The necessity of implementation of innovative technological processes at the preproduction phases is justified, which allows to reduce the level of material intensity, labor intensity and energy intensity of production and increase the efficiency of the production organization.

    • Economic analysis of replacement of conventional welding technology with unconventional

      pg(s) 268-272

      The technological and social environment in which we live changes very quickly. Competition grows from time to time, so it is a constant tendency towards product and service providers to achieve a competitive advantage, and thus satisfy the needs of consumers. In order to achieve the above, the organization is often at a crossroads where important decisions are needed, which are most often related to the investment in new equipment or technology. Also, in parallel with the decision to invest in new equipment or technology, a decision is made to retain or upgrade the existing one. In order to make the right decision, often well-known postulates of engineering economies are often used, which include systematic assessment of the economic values of the proposed solutions. In order for economies to be acceptable, solutions must show the existence of a positive relationship between long-term benefits and long-term costs, as well as ensuring the success and survival of companies in the market. In this paper, the economic costeffectiveness of replacing the existing electrolytic welding technology with insoluble electrode in inert gas (TIG), the new FSW welding technology is considered.

    • Testing of automaticized system for complex non-destructive study of metallic materials

      pg(s) 273-276

      Presented a program to test the automatized system complex non-destructive testing of structure and physical and mechanical properties of samples and products from metallic materials. The system consists of several modular devices that measure two non-destructive information parameters based on methods with different physical bases (magnetic, acoustic, thermoelectric, etc.). In the work are presented only two modular unit – MULTITEST MC010 for testing ferromagnetic materials, using the methods of measurement of the magnetic noise voltage and magnetoacoustic emission and MULTITEST CD010 for testing of metallic materials with the methods for measuring the speed and the attenuation coefficient of ultrasonic waves in the materials. Have been developed – general methodology of the system for testing / measuring equipment and methods for calibration and metrological instruments in operation of the system in a complex  non-destructive testing. Conclusions are made on the reliability of system measurements when used in complex non-destructive control of metallic materials.

  • MATERIALS

    • Influence of polymer molar mass on the properties membranes whit graphene oxide

      pg(s) 277-280

      The aim of the study was to assess the influence of the polymer molar mass on the properties of polymeric membranes produced with the addition of carbon nanostructures (commercial graphene oxide, GO). The membrane support layer was made from polysulfone (PSU) dissolved in dimethylformamide (DMF). The polymer matrix was formed from polyvinylidene fluoride (PVDF) dissolved in dimethylacetamide (DMAC). PVDF, serving as the base polymer, was purchased in two different physical forms, i.e granules with a molar mass of 530,000 g/mol and powder with a molar mass of 534,000 g/mol. The membranes were prepared via wet phase inversion, with or without the addition of GO to volume of the polymer matrix. The experiments helped to determine the thickness, tensile strength and contact angle of the produced membranes. Hydrodynamic studies allowed calculating the volumetric permeation flux and total resistance of both the reference membranes and the membranes containing GO was evaluated using a laboratory OSMONICS KOCH ultrafiltration unit.