Course - three-belt conveyor

Contents

Contents

   Introduction

General part

1.1 Purpose of the machine. Scope of application of this machine

1.2 Brief technical characteristics and description of the main components of the machine

1.3 Requirements for electric drive and automation

1.4 Selection of current type and supply voltage value

1.5 Selection of electric drive system and speed control mechanisms

Design and Construction Part

2.1 Detailed description of operation of the control circuit diagram

2.2 Analysis of deficiencies of the existing control scheme

2.3 Development of structural control scheme

2.4 Development of a new schematic control diagram

2.5 Development of conveyor loading algorithm

2.6 Design and layout of connections (wiring diagram)

     2.7 Calculation and selection of power of the main drive motor, feed drive and auxiliary mechanisms

2.8 Selection of control equipment (Calculation and selection of control elements)

2.9 Safety Measures

Conclusion

List of sources used

Paper

Explanatory note : 36 pages, 6 figures, 9 tables , 8 sources.

Graphics documents: 1 sheet.

Control Circuit Diagram, Power Circuit

The belt conveyor is designed with the specified capacity (Q = 1300 t/h) and belt speed U = 2.65 m/s, length 850 meters and inclination angle  = 120. An explanatory note of 12 sheets and a graphic part 3 of the A1 sheet have been written. Sheet 1: Conveyor General View, Sheet 2: Actuator General View, Sheet 3: Tensioner General View.

Introduction

In recent years, conveyor transport has been increasingly used in metallurgical plants for transporting bulk loads of raw materials and fuel. This type of transport is used not only at newly built and designed enterprises, but also at existing ones - during the reconstruction of the main units. Conveyors are used to transport raw materials from car dispensers, sorting stations or from the wharf of the factory port to a warehouse, from a warehouse to an agglomeration factory, to blast furnace and coke-chemical workshops. Conveyor transport is also used to supply solid fuel to the CHP; limestone, ore and other materials - in steelmaking shops, etc.

Conveyor transport is widely used for domestic transport. This is greatly facilitated by an increase in the degree of continuity of technological processes of the first alterations of coke, agglomeration, blast furnace, steelmaking, in which other modes of transport do not provide the modern level of production of these alterations.

Of the conveyors of all types, the most widespread in metallurgical plants were belt, the share of which is 95-97%. The widespread use of conveyor transport is due to its advantages over other modes of transport when moving large volumes of goods over short distances. These advantages include simplicity of design, reliability of operation, high productivity and low operating costs. In addition, the use of conveyor transport allows increasing labor productivity and the degree of automation of production, reducing the area of ​ ​ the plant by 10-15%, reducing the distance between workshops, simplifying transport communications, taking the plant-wide railway station of arrival outside the plant. The introduction of conveyor transport makes it possible to increase the degree of safety in transport.

The possibility of using conveyor transport in metallurgical plants increases even more with the development and creation of heat-resistant belts that allow transporting hot materials of metallurgical production of agglomerate, slag, coke, etc.

Main part

 1 Purpose of the conveyor. Scope of this conveyor

Belt conveyors are widely used in metallurgical, mining and other industries. I use them to transport bulk and piece cargoes both over long distances and over long distances. The simplicity and reliability of their design ensures their operation for a long time. Belt conveyors can be used in both closed and open areas, which explains their widespread use in industry. Conveyors are of continuous type and are characterized by continuous movement of loads along a given route without stopping for loading or unloading. Movable bulk load is arranged in continuous layer on bearing element of machine - belt or in separate portions. The unit weights are also moved in a continuous flow in a predetermined sequence one after the other. Due to the continuous movement of the load, the absence of stops for loading and unloading and the combination of working and reverse movements of the load-carrying element, continuous machines have high productivity, which is very important for modern enterprises with large cargo flows. For example, a modern open-cast coal belt conveyor can transport up to 30,000 t/h of overburden rock, providing 10 railroad cars per minute. Stationary conveyors of long length are mounted from several sections. The length of one section reaches 250m. and in some cases 400 m.The belt conveyor (Fig.1) consists of an endless rubberized belt 1 enveloping the drive 2 and the tension drum 3. The belt is supported by support rollers 4 and 5. Drive drum receives rotation from motor 6 through reduction gear 7 or other gear. The upper part of the belt on which the load moves is called a working or cargo branch. The lower part of the tape is called the idle branch.

The drum driven by the drive is usually placed in front (in the direction of the belt movement) and is called drive or head.

The second end drum has a belt tensioning device and is called a tensioning or tail

 Carrying and pulling member of belt conveyor is endless flexible belt resting by its working  and idle branches on roller supports and enveloping drive and tension drums at conveyor ends. For short conveyors intended for piece loads, the working branch of the belt can slide along wooden or metal flooring. Belt motion is transmitted frictionally from drive drum. The necessary initial tension on the runaway of the belt is created by the tensioning drum with the help of a tensioner, which is mainly performed by the load drum. The belts are loaded with loose material through a loading funnel, which is installed usually at the beginning of the conveyor at the end drum. Belt unloading can be end from drive drum or intermediate drum, for which purpose mobile unloading trolley or stationary plow dischargers are used. Direction of flow discharged from material drum is provided by unloading box.   Rotating  brushes (capron, rubber) or a fixed scraper are installed on the working side to clean the tape from the remaining particles. For many transported materials, installation of a cleaning device is necessary, since adhered particles, forming a difficult to remove uneven crust on the rollers of the idle branch, can lead to their uneven rotation and accelerated wear of the tape. The rotary drum with spiral scrapers cleans the tape well.     To drop particles accidentally caught on the inner surface of the idle branch of the tape, it is recommended to install an additional dropping scraper in front of the tension drum. Cleaning of the belt after the drive drum is also necessary because adhered particles, crumbling from shaking under each support of the idle branch, can form blockages that complicate the operation of the conveyor. Different centering roller supports are used to center both branches of the belt and prevent its excessive transverse displacement. Drive of belt conveyor drum consists of electric motor, reduction gear box and connecting couplings. Roller batteries are installed on turning sections of route branches to provide smooth bending of belt or rotary drums. All conveyor elements are mounted on a metal structure attached to the foundation or to the load-bearing parts of the building. Steel structures with a drive drum, drive and unloading box are called a drive station. Elements of structure with tensioner make tensioning station. The rest relates to the middle part of the conveyor, which is made of identical linear sections. All linear sections, transition sections, drive and tension stations are bolted together. As a rule, multi-roller supports forming a grooved belt are used for bulk loads. This shape of the belt at the same width and speed allows for a more than double increase in performance. Two-drum discharge trolleys are designed for intermediate unloading of only loose materials to the sides of the tape along one of the discharge branch pipes. Stationary plow dischargers can be used for both bulk and piece loads. Designs of plow droppers movable on trolleys are known. In addition to the above mentioned elements, conveyors are equipped with locking devices or double-deck normally closed brakes, as well as catchers of the belt located on inclined sections of the route in case of its break, safety devices and automatic control devices. The design of the conveyor depends on the type of belts used. Belt conveyors with a steel belt, in the same scheme as general-purpose conveyors, differ from the latter in separate structural elements due to the increased stiffness of the belt. Drums for steel tape have large dimensions, and roller supports are made in the form of disks on one axis, spring rollers, flooring with or without sides.For conveyors with wire belts, supports with a single horizontal roller can be used. On these conveyors, due to the looseness of the belt, mainly piece weights are transported. Conveyors with wire belts can operate at a high temperature of up to 1100 °. The desire to eliminate the belt as a traction organ led to the development of cable belts with two traction ropes resting on the blocks and a belt with a load lying on them. The combination of the belt with the traction chain made it possible to create belt-chain conveyors. The traction chain at this conveyor rolls along the guide blocks, and the side parts of the belt rest on inclined supporting rollers. With belt conveyors, the length of the conveyor depends on the angle of inclination; the steeper the conveyor, the shorter its length. Reducing the length of the conveyor reduces its cost and reduces the area occupied by it in the production room or in the territory of the serviced object. Therefore, in order to reduce the length and cost of the conveyor and in case of production need, steeply inclined and vertical conveyors with large inclination angles up to 90 ° are used. Here you can note conveyors with upper pressing elements: with a chain mesh belt, a rubberized fabric belt and rollers with an additional blade belt. In many cases, an increase in the angle of inclination is achieved by using special corrugated ribbons with ledges or ridges on the working side. For highly dusty materials, conveyors are used with a tubular belt having a zipper and a device for opening and closing it. In conditions of rough terrain, it is convenient to use conveyors with a belt suspended on chains to brackets and steel wire ropes lying on support blocks. A type of these conveyors is considered to be conveyors with a tubular belt, also suspended from steel wire ropes on chains. Of the numerous family of mobile and portable belt conveyors, a light type steeply inclined belt loader with variable tilt angle and transverse bars on the belt is shown. Most mobile belt conveyors use a motor drum with an integrated drive and a screw tensioner located in the upper part of the machine. Belt conveyors for underground cargo transportation are designed for use in constrained overall conditions, as well as for the movement of people and heavy piece loads. Belt conveyors of high power and considerable length are similar in design to general-purpose conveyors. However, the individual elements of the heavy-duty conveyors differ not only in their proportional increase in size, but also in their qualitative peculiarities. The drive, for example, is made with two drive drums, the tensioner has a system for changing tension in the belt during start-up and when its material load changes. To load the belt, feeders are used that provide a certain load supply corresponding to the conveyor capacity. Conveyors use belt catchers, powerful brakes and devices to monitor operation and service safety. Calculation of heavy-duty conveyors should be carried out according to updated methods. Particularly important in calculating these conveyors is the use of reasonable precise values of belt resistance and resistance at the loading point.

 1 Requirements for electric drive and automation

Main features of belt conveyor electric drive operation. This drive is characterized by prolonged operation for considerable periods of time. This majority of the electric drive conveyor differs sharply from other lifting and transportation machines, which are characterized by a cyclic re-short-term mode of operation. Loading of the machine, transportation and removal of the load in the tape conveyor is carried out as a rule, without stops and without pauses in its operation. This significantly affects the calculation and selection of engines. For belt conveyor, relatively rare launches are characteristic, which usually occur several times a day. Their duration has little impact on belt conveyor performance. In many cases, the duration of the launch is specially increased in order to reduce overloads, acceleration of the load on the belt, waking up of it, as well as slipping of the belt during acceleration. The direction of rotation of the belt conveyor and therefore the electric drive shaft of the belt conveyor changes or rarely. Thus, the conveyor conveys bulk and lump materials or unit loads in one direction for a long time, the escalator also works for a long time to lift or lower passengers, etc. Only some belt conveyors, such as pendulum ropes, require frequent reversal of mechanisms.

The conveyor operates at a certain stable load. Transitions from idle to limit loads are very rare. Thus, fluctuations in the load on the escalator and its repeatability depend on the number of passengers, the consistency of train schedules, etc. The load on conveyors installed at heat stations, mining and other mills is even more stable.

Significant overloads occur in the operation of conveyors operating in the open air under difficult atmospheric conditions. They can be associated with freezing of the material, changing the temperature of lubrication of the mechanisms. On belt conveyors with a long length, you can observe the lag in the beginning of the movement of sections of the belt at a distance of 70... 100 meters from the oncoming branch at a steady speed of the engine. At that additional elastic tension is created in belt, and traction force is applied to subsequent sections of belt by jerk.

 2 Selection of current and supply voltage values

Drive supply voltage - 380 V. Conveyor capacity - 40 t/h, AC frequency 50 Hz. At the request of the consumer, the conveyor can be made for working with a different voltage.

1.5 Selection of electric drive system and control methods (feed drive and auxiliary mechanisms)

The electric drive of conveyors is subject to the requirements of high reliability, ease of maintenance, as well as ensuring an increased start-up moment. In some cases, additional requirements arise to ensure smooth start-up, prevent tape slipping, little speed control, and consistent rotation of several electric drives. All these requirements are sufficiently met by asynchronous short-circuited or phase rotor motors. One method of controlling a multi-drive conveyor is the use of an adjustable drive. Adjustable drive makes it possible to increase durability of conveyor and conveyor belt mechanisms due to elimination of impact loads and symmetrical operation of drive motors at start-up and in operating mode . And also allows you to eliminate the slip of the tape on the drive drum, which affects its wear. In addition, the safety of using the conveyor is improved by eliminating the possibility of igniting the belt during slipping. Since the speed control ensures uniform loading of the conveyor, the resistance to movement is practically constant. Consequently, conveyor drives must control the speed of movement of the load-carrying member at a constant torque on its shaft, that is, at a constant tension regardless of the speed control range. Simultaneously with a decrease in the speed of the traction organ, caused by a decrease in the productivity of the mining machine, its service life increases, as the frequency of envelope of the drum belt decreases. The service life of the tape increases almost in proportion to the decrease in its speed. This is particularly important since the cost of the conveyor belt is between 40 and 70% of the cost of the entire conveyor unit depending on the length of transport. To the same extent, the wear and tear of the mechanical part of the equipment is reduced.

Design Design Part

2.1 Detailed description of operation of the control circuit diagram

Before starting the conveyor line, the QS1 machines shall be switched on... QS3. A voltage is supplied to the control circuit, which leads to the operation of the time relay KT1... To KTZ and short circuit of normally opened contacts of KT 1.1... KT3.1. Note that the time relay is a DC relay. Therefore, the voltage on the coils of the time relay KT1... KTZ is supplied through rectifier diodes VD1... VD3. Consider starting the conveyor line. First, the motor Ml is started by pressing the button SB1. On a chain of SB2, SB1, KT1.1, KM1, KA1, KA2, FR1, FR2, KSL1, SQ1, FR7, KV1.3, SB5, SB6, SB7 tension on the coil of the contactor of KM1 moves. Contactor KM1 operates and closes its line contacts KM 1.1 in stator circuit of motor Ml. The motor starts and drives the conveyor belt. At the same time, the block - contacts KM1.2 shunting the button SB1 and the contact KM 1.3 are closed, which includes the lamp HL1 indicating the operating state of the first conveyor, the opening of the contact KM 1.4 leads to the removal of voltage from the coil of the time relay KT1, which controls the time required to accelerate the engine to maximum speed. The conveyor belt, which has come into motion, rotates the shaft of the tachogenerator BR1. When the conveyor belt reaches the maximum speed, the relay KV1 operates and closes its contacts KV1.1 in the circuit shunting the contact of the time relay KT1.1 and KV1.2 in the control circuit of the next conveyor. Time switch KT1 controls start time. After the specified time, the relay KT1 releases its armature and causes its contact KT1.1 to open in the circuit of the contactor KM1. However, contactor KM1 continues to be powered through closed pin KV1.1. If the tape does not reach its maximum speed for any reason during the start-up time, contact KT1.1 will open before contact KV1.1 closes. Motor M1 will stop as the power circuit of contactor coil KM1 will open. In case of normal start-up of the first conveyor, contact KV1.2 in the control circuit of the second conveyor will close. On the circuit SB3, KV1.2, KT2.1, KM2, FR4, FR3, KA4, KV3, KA3, KSL2, FR8, SQ2 voltage is supplied to the coil of contactor KM2. The latter operates and closes its contacts KM2.1 in the stator circuit of the second engine M2. The start of the second conveyor controls the time relay KT2 and the speed KV2 in a similar manner to the case discussed. Thus, interlocks from the speed relay KV1... KV3 and the time relay KT1... KT3 allow monitoring the start time of conveyors. You can stop the conveyor line from any route point by pressing one of the buttons SB5, SB6 or SB7 or from the control station SB2.

2.2 Analysis of deficiencies of the existing control scheme

The design of the belt conveyor has  a number of serious drawbacks: (1) due  to the fact that the belt receives significant traction  forces, expensive  and heavy multilayer belts have to be used; 2) the side edges of the tape , when  skewed , undergo rapid wear , and this, especially   in the presence of moisture , leads to rapid   decay of the exposed fabric   and destruction of the tape; 3 ) numerous support rollers require constant observation and care.  

Therefore , more   durable tape conveyors have recently become common, in which  two steel ropes located on both sides of the belt bear the entire main load. The belt serves only as a supporting element and therefore , taking only minor traction forces, can be made of a single layer of cotton fabric coated on both sides with a layer of rubber.    Steel plates or square rods at a distance of 700 to 1200 mm from each other are veiled across the belt, in special holes. The plates protrude on both sides  of the tape by 60-65 mm and with their ends enter the slots of bilateral steel shoes with rubber inserts. Shoes rest on ropes, supporting both branches of  the tape.   Plates and tape     assume grooved shape under action of material weight. During operation of the conveyor , shoes  , plates, belt and movable material move as a whole with the ropes. Thanks to the rubber inserts, the grip force of the shoes with the ropes exceeds the weight component of the transferred material even when transported with a slope of up to 19.5 degrees. To limit the sagging of ropes, pulleys are installed along the conveyor; the diameter of the upper pulleys is 260-280 mm, the lower ones are 220-240 mm. The number of supporting pulleys is 60-80% less than the number of roller supports of conventional belt conveyors. In order that the shoes after enveloping the head and tails of the ego drums again hit the rope, special devices are provided in the conveyor structure. When moving to the tail drum, the shoes remain on the lower ropes until they reach the lower part. At this point, the ropes are directed sequentially to the oblique pulleys. After bypassing these pulleys , the ropes return and pass under the pulley located   on the same axis as the drum , where  at the transfer point the shoes again sit on the ropes. Transport lifting equipment of this type has proved to be very reliable in operation: after two to three years of work, the wear of tape, ropes and shoes was very insignificant. The speeds were taken to be the same as for conventional belt conveyors, even when transporting large-piece materials and steep slope. The use of cable belts is particularly cost-effective with a conveyor length exceeding 200 m; in general, their length can be brought to 4 km. Further improvement of belt conveyors takes place in the following directions: 1) an increase in the angle of inclination due to the device on the working surface of the belt of ribs, shaped patches, corrugated surfaces, etc.; 2) increase of transportation length on one unit due to high-strength tapes or combination of tape with rope; 3) increased reliability of operation and service life of conveyor elements. The operation of belt conveyors is determined by the correct travel of the belt (absence of distortions), which is ensured by perpendicular to the longitudinal axis of the conveyor, the axis of the drums and roller supports.

2.3  Development of structural (functional) control diagram

The following symbols are adopted in Figure 5. The computer is an industrial computer, which is part of the APCS "Power Supply" and performs centralized control over the consumption of electricity for energy-intensive technological processes and forms the necessary "tips" for changing the mode of operation of plants, including conveyor ones, to reduce electricity consumption, if this is technologically possible and does not violate safety requirements. The CRIC device is a set of technical means for automatic monitoring of conveyor operation: switched on or off, operating under load or at idle mode. The UKRK device is a microprocessor device for correcting the conveyor operation mode, which interacts with the computer, the CRIC device and the automated conveyor unit and generates setpoints for the conveyor belt speed controller. An automated conveyor plant is a conveyor plant that is equipped with automation equipment. Currently, almost all belt conveyor lines of mines are automated, as a rule, with AUK.1M equipment, which provides centralized control of the start-stop processes of conveyors and automatic protection against the development of an accident in case of emergency situations. In our opinion, it is necessary to use computer-integrated automation systems to control conveyor installations, which have the ability to coordinate conveyor robots using computers and allow expanding, if necessary, the composition of technical means, in particular in our case, the use of automatic belt speed controllers. The ECS system is an accepted system for controlling the speed of a conveyor drive motor.

2.4 Development of schematic control diagram

Circuit diagram of belt conveyor drive.

The schematic diagram shows the complete composition of the elements of the device as a whole and all the connections between them, gives a basic idea of ​ ​ the principle of operation of this device. Any automatic device is a complex of separate structural or circuit elements, each of which performs the task of converting energy received from the previous element and transferring it to the subsequent element.

Elements are structurally completed devices that perform certain independent functions of signal conversion in control and control circuits. Schematic diagrams indicate all electrical elements in the form of schematic graphic symbols, next to which alphanumeric symbols are placed. Schematic diagrams display all elements of the system as a whole or its functional parts and their connections.

According to the performed functions, the following elements are included in the developed diagram:

Contactors, time and thermal protection relays, control buttons, current protection devices, motors, wires and cords, electromagnetic couplings

 Contactors or magnetic starters are used to control power circuits of the device. 

Contactor - is called an electromagnetic relay that has a powerful contact system. 

Thermal relays are used in electric motor overload protection circuits.

The measuring element of the thermal relay is a bimetallic element, which, when heated, bends and puts the system in an off or on state.

The electric motor is an element of the power electric circuit that drives all the ETS mechanisms.

2.5 Development of conveyor loading algorithm

To begin the upgrade of the circuit, you need to draw up an algorithm for the operation of the belt conveyor

A control algorithm is a set of prescriptions that determine the nature of external influence on a controlled object in order to implement a given functioning algorithm.

The operation algorithm refers to a set of requirements leading to the correct execution of the process.

Organization of machine maintenance

The system of scheduled preventive repairs provides for:

1. periodic maintenance, inspections and repairs of various types after a certain operating time of the object;

2. establishing a sequence of preventive and repair actions and operating time intervals between them depending on the operating conditions of the object, its technical characteristics, the type of production and properties of the processed materials during work operations;

3. performance of maintenance and ongoing repairs within the limits regulated by the scope of work, ensuring normal operable state of the facility; labor intensity of works depends on complexity and repairability of the object.

The following concepts and definitions are adopted in the PPM system: overhaul cycle, structure of overhaul cycle.

The overhaul cycle is the operating time of the machine in the clock between two overhauls, and for the new machine from the moment it was put into operation to the first overhaul. The duration of the overhaul cycle depends on the operating conditions of the facilities.

The structure of the overhaul cycle is the number, periodicity and sequence of all types of repairs and maintenance during the overhaul cycle.

Maintenance consists of a set of process operations, each of which forms part of the maintenance process carried out by one or more workers. The operation is a set of sequential actions for servicing the unit or group of units of the machine.

Operations, which by their nature, conditions of execution and periodicity are combined into certain groups, are called types of services: monthly (EC), TO1, TO-2, TO3, as well as seasonal (CO), carried out 2 times a year. Service types are a set of works designed to reduce the rate of wear of machines, ensure the required level of probability of their failure during periods between services and their effective use of fuel and other operational materials.

Monthly maintenance ensures normal operation of the machines during the working shift. It includes operations for refueling the machine with fuel and lubricants, checking the serviceability and operability of its component parts before commissioning, as well as ensuring the safety of its use as intended. The main purpose of the first second and third technical services is to identify faults and prevent failures by timely performance of control diagnostics, fastening, lubrication, filling, adjustment, electrical and other types of work without disassembling the units and removing individual units from the machines. If during scheduled maintenance critical states of individual structural elements are detected, then they are replaced with operable ones. During seasonal maintenance, machines are prepared for operation in cold or warm season. It is usually combined with one of the services.

The list of maintenance operations in is compiled according to the models of machines and equipment in accordance with the instructions and requirements of the operational and technical documentation of the manufacturers, taking into account their specific operating conditions. The list of high order maintenance operations includes works performed during lower order maintenance. At the same time, the work regulated by the requirements of the State Gortekhnadzor, which are carried out according to a special schedule, is taken into account.

External care of machine and equipment

External care operations include cleaning of cabins and workstations of drivers and operators, cleaning of undercarriages and working tools, washing of external surfaces of the machine, wiping of engines, boards, instrumentation equipment, glass, etc. When cleaning unpainted parts of cars, as well as soil adhered to them, and in winter, snow and ice, blades, scrapers and metal brushes are used, and hair brushes and wiping material are used for painted surfaces.

Sticky dust and dirt are removed from machine surfaces by external washing. At the same time, both cold and heated water up to 40-50 * С is used. To intensify the washing process, washing chemicals are used - special liquids and powders. Detergent solutions reduce the strength of the surface stress of the water film formed on the washed surface, and dissolve oily deposits, form emulsions and suspensions that are easily washed away. In order not to cause damage to the paint of the lining of the machines, the difference between the temperatures of the water and the washed surface should not exceed 18 - 20 * С.

Fastening works

Fastening works are performed to restore the required tightening of threaded connections. The labor intensity of fastening works reaches more than 20% of the total volume of work performed during maintenance of road machines. The high labour intensity of fastening works is due to the large number of fasteners, their lack of reliability, and in some cases the lack of scientifically sound bottom and recommendations on the periodicity of their maintenance.

Serviceability of fastening joint operating under conditions of long-term variable loading is estimated by degree of its preliminary tightening reduction. And the need for the fastening operation depends not only on the pre-tightening force, but also on the operating conditions, material and dimensions of the fastening parts, as well as on the design of the connected objects and the method of manufacturing the threaded connection elements. When evaluating the state of the fastener joint, restoring it, and determining the frequency of maintenance, consider the purpose and operating conditions of the objects. In this case, it is advisable to consider three groups of compounds.

The first group is threaded joints, on which the safety of movement or the performance of working operations of the machine (brakes, steering, etc.) depends. The second group is fasteners that ensure the strength of the structure. These connections usually bear power loading, and reliability and durability of operation of the machine in general depends on them (fastenings of the engine, the transmission, reduktorovit   . item).                                                    The third group is fasteners that ensure the tightness of the system (not included in the first group), which prevent leakage of liquid, gases (fuel, air, water and oil pipelines, etc.). The connections of the first group are checked most often and thoroughly using special devices and keys. Connections of the second group are checked by external inspection of fasteners and condition of locking devices and by test tightening with wrench. Compounds of the third group are checked visually by liquid trace, by pressure drop on instruments and by hearing (by hissing).

Control and adjustment works

The need to monitor the technical condition of the structural elements of road machines arises as a result of their wear, violation of the fits and gaps between the mating parts or deterioration of the functional properties of the components requiring periodic regulation or replacing the failed elements. When monitoring the state of objects, the gap between the conjugated parts is measured and deviations of dimensions from the norm are established, which determines the need for their regulation. At the same time as control and adjustment works, works are performed to eliminate minor faults detected at the same time.

There are two types of adjustments - compensation and adjustment, changing the output parameters of machines or its systems. Adjustment of the clearance in bearings, braking devices, adjustment of the tension springs of the track belts, etc. Adjustment adjustments are the setting of the position of the working fluid in the hydraulic system, etc. Methods and means of monitoring the technical condition of road machines and their component structural elements are different. They can be classified according to various characteristics: by types of machines and objects of control, by the assessed diagnostic characteristic and the parameter measured by the method of diagnosis; by technical means of measuring the determined parameter. Threaded connections are controlled visually by piercing bolt heads and testing their tightening with a wrench.

Lubrication of machines and filling with service materials

The main document for machine maintenance is the lubrication map, which consists of two parts - a diagram and a table. The diagram shows the location of all friction joints and assemblies on the machine, indicated by the corresponding numbers. The table has a single numbering with the lubrication points indicated on the diagram and contains the following data: name of friction parts with indication of their numbers on the lubrication diagram; number of lubricating points; recommended lubricant for summer and winter conditions; periodicity and quantity of lubricant supplied per lubricant; lubrication method. Lubrication card for each machine is applied to its operation manual.

When choosing a lubricant for lubricating a particular unit, it is necessary to take into account: the pressure, with an increase in which it is necessary to increase the viscosity and oiliness of the oils; a sliding speed with which the viscosity of the lubricants used should decrease; the temperature of the working surfaces and the environment, with which the viscosity of the oils should increase; condition of friction surfaces, between which viscosity of oils should increase as their processing deteriorates and gaps increase. In addition, when choosing oils and lubricants, it is necessary to take into account the location of friction pairs, the degree of dynamics of active loads, as well as the design features of lubricating systems.

Determining Machine Performance

The capacity of the conveying machine (plant) is determined by the amount of bulk or piece cargo transferred per unit time. Distinguish between technical and operational performance of the machine.

Technical (passport) capacity refers to the amount of transported cargo per unit of time when the load-carrying element of the machine is fully filled and while maintaining a constant nominal (passport) operating speed. Thus, the technical performance of the machine is determined by its parameters and properties of the transported load.

The operational capacity is determined taking into account the actual local operating conditions of the degree of filling of the load-carrying element of the machine and the use of the machine over time (as well as taking into account the properties of the transported cargo, if in some cases they change). Thus, the operational capacity depends not only on the technical parameters of the machine and the properties of the load, but also on the actual operating conditions.

Conclusion

Modern belt conveyors are distinguished by a small workload, high reliability of work and labor safety. The expansion of the volumes and the field of application of belt conveyors is associated with a further improvement in the structural and technological characteristics of the plants. The use of intermediate drives for belt conveyors has begun, allowing to increase the length of the stakes and thereby reduce the number of intermediate overloads (or completely eliminate them), reduce the turnover of the belt and increase its service life. The improvement of loading devices, roller-bearing and support structures of staves, as well as the creation of new special types of belt conveyors (belt belts) makes it possible to increase the lumpiness of rock cargoes moved by conveyors. The use of frost-resistant rubber belts, special lubricant grades and new structural materials for drive gears extends the field of application of belt conveyors to the Far North.

The application of automation ensures smooth starting of the belt conveyor, the ability to adjust the speed of the belt depending on the amount of incoming cargo flow, automatic control (by ultrasonic method) of the state of the roller supports, the integrity of the belt, weighing and recording the amount of cargo moved on the belt, etc.