Pipe fittings, which are one of the main elements of any type of pipeline networks, can be used for various purposes: shut-off, reverse, safety, control, separating, shutting off, etc. In order to control the performance of this element, it is necessary to carry out various tests in the prescribed manner, the main ones being pneumatic. This study is devoted to the development of equipment for in-plant pneumatic testing of rotary check valves for pipeline systems of hazardous production facilities with ultra-high parameters of the working environment. For this design of the installation, the simulation of the stress-strain state of the elements of the installation was carried out, as well as the gas-dynamic calculation of the test circuit of the installation.

Keywords: rotary check valve, pipeline fittings, pipeline system, mathematical modeling, finite element method, strength analysis, stress-strain state, computational fluid dynamics, pneumatic testing, technological pneumatic installation

The article provides a brief analysis of the processes that occur when starting an electric motor. Mathematical relations modeling the process of starting a direct current motor are presented. Graphical dependences allowing to determine parameters of a thermistor providing an optimum start-up of a direct current machine have been obtained.

Keywords: starting current, thermistor, starting rheostat, thermal characteristic, DC motor, boundary conditions, torque resistance, idealized rheostat, heat loss, economical starting

The article gives a brief analysis of thermal processes occurring during the start-up of an electric motor. Mathematical relations modeling the distribution of thermal energy in the thermistor during the process of starting the DC motor are presented. Graphic dependences are presented, which allow to make arrangement of thermoresistors for the starting rheostat and to determine parameters of the starting rheostat obtained in this way. Application of the starting rheostat made on the basis of thermistors, provide an optimal starting of a DC motor.

Keywords: control gears, thermistor, starting rheostat, DC motor, temperature, dynamic characteristic, form of starting current

Location of compensating devices is determined by various factors: configuration of power supply system, enterprise load schedule, type and length of power lines, parameters of capacitor banks, value of supply voltage. We consider the influence of the above factors on the creation of a mathematical model to determine the location of compensating devices, taking into account the minimum economic costs.

Keywords: compensating devices, reactive power compensation, power system, power grids of industrial enterprises, load schedule, mathematical model, reduced costs

The article discusses the production and use of environmentally friendly fuel - pellets. A review of the designs of mobile pellet production plants was carried out, the advantages and disadvantages of these designs were identified. Potential consumers of pellets and equipment (heating boilers for which pellets are the fuel) are considered. A mobile complex for the production of pellets on the chassis of the MSN-10-004-03 . The technology of pellet production using a mobile mobile installation is described.

Keywords: pellets, mobile plant, design, biofuels, production technology

Pipeline networks today are the main and one of the safest ways to transport all kinds of media. This engineering system consists of various elements, one of which is pipeline fittings that regulate the parameters of working media and protect pipelines from overpressure. In order to control the operability of pipeline fittings, it must be subjected to comprehensive tests, one of which is a leak test. The presented study describes the developed design of a technological hydraulic installation intended for use as part of process equipment for conducting in-plant testing of pipeline valves. The results of modeling the stress-strain states of the main units, as well as the hydraulic calculation of the test circuit of the installation are presented.

Keywords: rotary check valve, pipeline fittings, pipeline system, mathematical modeling, finite element method, strength analysis, stress-strain state, computational fluid dynamics, hydraulic tests, technological hydraulic installation