The article discusses the requirements for propellers of bottom mining machines for the development of deep-sea deposits of such unique minerals as ferromanganese nodules, deep-sea polymetallic sulfides, cobalt-manganese crusts. The main factor is the minimal impact on the underwater ecosystem. Based on existing prototypes of mining machines and patents, an analysis of the advantages and disadvantages of existing conceptual mechanisms for the movement of mining machines was carried out, as a result of which it was determined that the most promising machines are those that do not contact the surface of the seabed, but such machines have a number of disadvantages. No less promising today are walking and tracked vehicles. The paper presents simplified formulas for determining the required minimum traction force when moving underwater mining machines, and simplified formulas for determining the speed of movement were obtained, which also clearly indicates the advantage of floating mining machines. According to the obtained graphical dependencies, a set of parameters plays an important role in the productivity of mining machines, including the speed of movement, overall dimensions, weight, and shape of the machine. The article also describes a complex for the extraction of minerals dispersed along the seabed, developed by the staff of the Department of Mechanical Engineering of St. Petersburg State University with various configuration options for the complex depending on the type of mineral, as well as the density of its distribution.

The effect of high-temperature thermomechanical treatment (HTTT) on abrasive wear resistance of steel 30KHGGSA as the main material to manufacture holder of mining machine cutters is studied. The procedure of HTTT during deformation of cylindrical steel fragments at the preset settling-down rate and subsequent quenching is described. The finite element modeling in DEFORM-3 finds distribution of plastic strain in volume of forged pieces. On the plant based on the upright drilling machine, the abrasive wear resistance of forged pieces is tested on sandstone and siltstone as the medium-hardness and abrasivity co-rocks most frequently met in development heading. It is shown that pre-deformation of the fragments before quenching, i.e. HTTT, imporves the steel hardness from 44 to 55 HRC. It is shown that as against specimens nondeformed before quenching, the abrasive wear resistance of steel subjected to plastic straining up to εΣ ≈ 0.7 increases by 1.9 times in case of both siltstone and sandstone. Considering the obtained results, it is suggested to amend the manufacturing technology of cutters by quenching of fholder forging starting immediately from the forging temperature and by subjecting thereby the holder to high-temperature thermomechanical treatment. The cutting tool cartridge is to be held in the holder by cold pressing. It is assumed that HTTT application can essesntially (two times and more) improve wear resistance of steel holder head and, as a consequence, extend service life of cutters.

The presented research is focused on two issues. The first one is finding additional parameters that characterize the technical condition of an electric machine according to the current consumption. The second one is increasing of the informativeness of diagnostic methods in conditions of limited access to equipment and incomplete information. The paper discusses a method for diagnosing low and medium power asynchronous electric motors by electrical parameters. It is shown that asynchronous electric motors powered from a self-commutated voltage inverter have contained higher harmonic components in addition to the main harmonic. The non-sinusoidal voltage leads to the emerging of the highest current components in the stator winding of the motor. This is the reason for occurring of a pulsating component of the torque on the motor shaft. Therefore, there are two types of ripple: the one caused by the power supply from the self-commutated inverter and the one caused by defects. The moments’ coincidence of these ripples leads to increasing in the amplitude of oscillations. However, significant noise due to the presence of an autonomous inverter does not allow using the current spectrum to diagnose damage. Analysis of the hodographs of the Park’s vector of the stator current and voltage allows one to exclude harmonic components that were formed by the carrier frequency (and multiple of it). At the same time, analyzing the modulus of the Park’s vector and its spectrum, one can note pulsations of the amplitude values of the vector modulus corresponding to certain damage.