IMPROVEMENT OF THE BELT CONVEYOR STRUCTURAL ELEMENTS USING COMPOSITE MATERIALS

ABSTRACT

The analytical assessment of the operational parameters of the rollers in various designs made it possible to propose composite materials based on regenerated thermoplastics of the polyolefin class (PP, HDPE, HDPE) for the manufacture of their elements. Functional elements from the developed composites can be manufactured using high-performance injection molding and extrusion technologies, depending on the design version of the metal polymer roller. To increase the manufacturability of the injection molding and extrusion process, it is advisable to introduce ultrafine polytetrafluoroethylene in an amount of 1.0-5.0 wt % into the composition of the composite material as a processing additive, which not only increases the quality parameters of the surface layer, but also contributes to an increase in resistance to high temperatures and combustion. The use of the developed metal polymer roller supports allows you to reduce weight, replace expensive imported rolled pipes with domestic regenerated raw materials, reduce energy consumption during operation of the conveyor belt due to a decrease in mass and coefficient of friction, reduce the likelihood of dispersed cargo particles sticking to the working surface of the shell, leading to increased wear of the conveyor belt.

АННОТАЦИЯ

Прoвeдeннaя aнaлитичeскaя oцeнкa эксплуaтaциoнных пaрaмeтрoв рoликoв в рaзличнoм кoнструктивнoм испoлнeнии пoзвoлилa прeдлoжить для изгoтoвлeния их элeмeнтoв кoмпoзициoнныe мaтeриaлы нa oснoвe рeгeнeрирoвaнных тeрмoплaстoв клaссa пoлиoлeфинoв (ПП, ПЭНД, ПЭВД). Функциoнaльныe элeмeнты из рaзрaбoтaнных кoмпoзитoв мoжнo изгoтaвливaть высoкoпрoизвoдитeльными тeхнoлoгиями литья пoд дaвлeниeм и экструзии в зaвисимoсти oт кoнструктивнoгo вaриaнтa испoлнeния мeтaллoпoлимeрнoгo рoликa. Для пoвышeния тeхнoлoгичнoсти прoцeссa литья пoд дaвлeниeм и экструзии цeлeсooбрaзнo ввeдeниe в сoстaв кoмпoзициoннoгo мaтeриaлa в кaчeствe прoцeссингoвoй дoбaвки ультрaдиспeрснoгo пoлитeтрaфтoрэтилeнa в кoличeствe 1,0–5,0 мaс. %, кoтoрaя нe тoлькo пoвышaeт пaрaмeтры кaчeствa пoвeрхнoстнoгo слoя, нo спoсoбствуeт увeличeнию стoйкoсти к вoздeйствию пoвышeнных тeмпeрaтур и гoрeнию. Примeнeниe рaзрaбoтaнных мeтaллoпoлимeрных рoликooпoр пoзвoляeт снизить мaссу, зaмeнить дoрoгoстoящий импoртируeмый трубный прoкaт нa oтeчeствeннoe рeгeнeрирoвaннoe сырьe, умeньшить энeргoпoтрeблeниe при эксплуaтaции лeнтoчнoгo кoнвeйeрa вслeдствиe умeньшeния мaссы и кoэффициeнтa трeния, снизить вeрoятнoсть нaлипaния диспeрсных чaстиц грузa нa рaбoчую пoвeрхнoсть oбeчaйки, привoдящeгo к пoвышeннoму изнaшивaнию трaнспoртeрнoй лeнты.

Keywords: Conveyor belt, resistance to combustion, shells, thermoplastic compositions, modification, metal polymer rollers, housing, SolidWorks modeling.

Ключевые слова: Ленточный конвейер, стойкость к горению, обечайки, термопластичные композиции, модифицирование, металлоплимерные ролики, корпус, SolidWorks моделирование.

Introduction. A belt conveyor is a conveying machine for moving bulk and piece loads in a horizontal and inclined direction in a continuous flow without stopping for loading and unloading [1, p. 21-22].

One of the main structural elements of the conveyor belt is a roller support, which ensures the movement of the belt with reduced resistance and an increase in conveyor productivity due to the "grooving" formed by 3-7 rollers. The characteristic appearance of the three-roller support is shown in Figure 1.

The designs of belt conveyor elements used (roller supports, rollers, drums, belts) are largely determined by the operating conditions of the conveyor and significantly depend on the parameters of deformation and strength characteristics and granulometric composition of the transported mass. So, when moving a mass with a high specific gravity consisting of large fragments, tapes with a significant number of gaskets and a larger thickness of the working lining are used, rollers with increased outer diameter and axis diameter are used, etc. [11, p. 3-4].

However, the problem of ensuring a given resource of these conveyor elements during the transportation of coarse rocks is far from an optimal solution, since in practice their premature failure occurs. There are cases when the service life of conveyor rollers transporting coarse-grained rock did not exceed 40-50 hours. The low durability of the rollers is associated with the use of roller supports that are not adapted to these conditions, as well as ignoring the significant factors acting on the support, which leads to the choice of rollers with a service life that does not correspond to the optimal operating conditions of the conveyor [6, p. 5-6].

Figure 1. Typical design of a three-roller support of a conveyor belt

The rollers of belt conveyors include a shell, an axis located in the holes of bearings installed in the housing and containing sealing elements to reduce the negative impact of abrasive and corrosive media on the service life. Rollers in which the main elements (shell, axle, body) are made of carbon steels of various compositions when they are permanently connected, mainly by welding, have become the most widespread in belt conveyor designs.

Methods. The typical design of the roller of a belt conveyor made mainly of metal elements is shown in Figure 2. An analysis of the operating conditions of belt conveyors used in the construction industry, road construction and chemical industry indicates the expediency of modifying the common design of metal rollers to increase their operational life, reduce metal consumption, increase the manufacturability of manufacturing and installation, reduced cost [5-6].

In this aspect, metal polymer rollers have a special perspective, in the construction of which elements made of polymer or composite materials are used, made using high-tech methods of polymer and composite technology.

Figure 2. Typical design of a belt conveyor roller

It is obvious that a reasonable choice of functional materials to ensure optimal operating conditions for belt conveyors should be carried out based on the results of a system analysis, including structural, deformation-strength, corrosion-mechanical, materials science and technological aspects of creation and operation.

The conducted analyses in the field of designs of metal polymer rollers of conveyor belts have shown the presence of various methodological approaches to ensure high parameters of consumer characteristics.

Results and Discussions. A roller design has been developed in which the shell is made of a composite based on thermoplastics with a filler in the form of dispersed wood particles with a content of 10-50 wt. % [8, p. 170-171].

Composite materials based on regenerated thermoplastics of the class of polyolefins, polyamides, polyesters with various fillers of organic and inorganic nature – metal oxides, dispersed fragments of glass and carbon fibers, asbestos and functional components – flame retardants can be used to manufacture the shell of a metal polymer roller, seals, bearing housings [12-14].

To make a reasonable choice of the composition of the composite material for the manufacture of metal polymer roller elements with an optimal combination of operational, technological, and economic characteristics, the stress-strain state of belt conveyor rollers of various design designs was analyzed.

Various variants of the structural design of the metal polymer roller have been developed to assess their operational parameters, taking into account the manufacturability of manufacturing in mass production conditions at specialized enterprises (Figures 3, 4).

In option I, the shell 1 and the bearing assembly 8 are proposed to be made of a polymer thermoplastic material or a composition based on it. Fasteners of 2 standard types are provided for fixing the shell and the manufacturability of assembly and repair work. The labyrinth seal 7, made of composite materials by injection molding, reduces the intensity of the abrasive and corrosive effects of the operating environment on the bearing, which has a beneficial effect on the operational life of the roller when operating belt conveyors under the influence of atmospheric factors in the construction industry and road construction enterprises.

In the second variant of the structural design of the metal polymer roller (Figure 2), including the shell 2, bearing housing 4, bearing 7, locking ring 6, axis 1, packing ring 5, cover 3, it is assumed to use various composite materials based on polyolefins.

The roller shell can be made of a composite thermoplastic material with increased resistance to combustion. The use of a thermoplastic composition for the manufacture of a shell allows its production in the form of a semi-finished pipe product using a high-performance extrusion method.

At the same time, it is possible to use regenerated thermoplastics, which, in terms of their parameters of deformation and strength characteristics and wear resistance in conditions of abrasive and aggressive media, are practically not inferior to primary materials.

There is an annular groove in the shell housing, which ensures reliable fixation of the bearing housing by injection molding in compliance with all necessary process parameters.

Figure 3. Construction of the belt conveyor metal polymer roller (option I)

1, axis; 2, shell; 3, cover; 4, bearing housing; 5, packing ring; 6, locking ring; 7, bearing

Figure 4. Construction of the belt conveyor metal polymer roller (option II)

The presence of a polymer cover 3 in the roller structure, which is fixed by a locking ring 6, ensures reliable fixation of the bearing 7. To ensure the possibility of reducing the corrosion-mechanical wear of the bearing 7, a sealing element (oil seal) 5 is used in the design, which is made of rubber or thermoplastic elastomer and fits snugly to the axis 1 on one side and to the cover on the other.

The sealing effect is enhanced by filling the internal cavities formed between the bearing 7 and the cover 3 with a grease containing components that reduce corrosion damage to the friction element.

Conclusion. For the manufacture of the sealing element, it is advisable to use traditional rubber compounds, which are processed into a product by vulcanization in a mold according to specified technological modes.

For the manufacture of the friction unit element – axis, carbon steel 40 and traditional machining technology are used to obtain the necessary geometric parameters and surface roughness.

To evaluate the parameters of the stress-strain state of conveyor belt rollers, the SolidWorks software environment was used, which allows for solid-state, surface, frame and hybrid parametric modeling.

Two variants of the design of the conveyor belt roller were analyzed – metal polymer (Figure 2) and metal (Figure 3).

The creation of a finite element grid and engineering analysis for the stress-strain state of conveyor roller elements by the finite element method were carried out in the integrated SolidWorks computational CAE module SolidWorks Simulation.

The creation and design of design documentation was carried out using the automated system of design and technological preparation of production Compass 3D V14.

Acknowledgments. The authors of this work express sincere thanks to Prof. Struk V.A. and his team and also Prof. Riskulov A.A. for their practical supporting in conducting experimental research and obtaining results.

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