Bantlı Konveyörlerin Bilgisayarla Tasarımı

Abstract

Özellikle yığma türde malzemeler için en etkin taşıma sistemlerinden biri sürekli taşıma makineleridir. Bu tip makineler malzemenin çabuk,ekonomik ve daha kolay taşınmasını sağlarlar. Bu araştırmada, bantlı konveyörlerin tasarımını yapacak bir bilgisayar programı yazıldı. Program TURBOPASCAL programlama diliyle AutoCAD çizim programını kullanarak yazılmıştır. Program bantlı konveyörlerin başlıca kısımlarını oluşturan bant, tahrik ve dönüş tamburları, rulolar ve tahrik grubu seçimi, hesabı ve çizimleri bilgisayar yardımıyla yapılmış ve tasarım sonuçlarını standartlaştırır ve tasarım ilgili TSE, DİN, İSO standartlarına uygundur.

One of the most effective transportation systems especially for bulk materials is continuous conveyors. They enable to transporî rnaterials quickly. in this study a computer program has been developed in order to provide a computer aided design tool for belt conveyors. History of belt conveyors goes back to about iwo centuries. Severa! kinds of solutions exist depending on the possibilities of construction and the capability of the constructor. Early belt conveyors have been used for transportation of grain,,h however, coal and mineral ores have started to be carriedat the end of 19 century. Early models did not have rollers and goods have been sliding on wood ör plate guides. After flat ör concave chutes, towards the end of id century. triple rollers groups were introduced. Then, standard roller groups with bearing were introduced. it was obvious that belt conveyors were economic for carrying bulk materials över long distances at high capacities. Belt conveyors have found a sucsessfull application in transportation of materials like sand, stone, sugar, wheat, mineral ores at high capacities. Belt conveyors are employed to convey a great variety of unit loads bulk materials along horizontal ör gently indine paths and also to carry articles of light weight in line production from öne operation to another. They are extensivly used in ali branches of industry and ofen included in complicated instalations such as transfer lines, handling bridges, grader elevators, ete. According to design, belt conveyors classified as stationary, portable and mobile conveyors. According to their purpose, we distinguish general purpose and special purpose conveyores. A belt conveyor is simply composed of an infinite belt vvhich is streched betvveen two drums. Its purpose is to convey material from a feeding station to a discharge Vi point. In order to do this jqb, the belt is installed in an expediant mashinery. This machinery plant consist of the driving drum, connected with the drive unit, and a return drum whose position can be adjusted by means of a tensioning device. The frame construction together with the trough idlers carries the upper belt run, the return idlers carry the lower run. In addition a material feeding and discharge device is necessary in order to charge the material onto the belt or to remove it from the belt. To set this belt conveyor system in motion, a pre-tensioning force is necessary, started by the return pulley or tension drum, so that the peripheral forces on the drive drum can get going the belt. The "essence" of the complete plant is the conveyor belt. This is the main factor which determines whether the apparently simple principle of belt conveying will function smoothly. It is, therefore, a matter-of-course that both, designers and users, will pay particular attention to the conveyor belts. Drive (2) in driven (3) drums are mounted on the chassis (1). Belt (4) that passes around these drums is carried by the support (5) and return (6) rollers which are also mounted on the chassis. Snub drums (7) are used to prevent return oilers from the excess loads. Take up mechanism (9) is necessary for moving the belt. The other necessary parts are : loading hopper (10) to load material onto belt, discharge spout (11) to unload material from the belt, strippers and cleaners (12) to clean the belt. Figure 2- Main Parts of a Belt Conveyor [1]. Belt conveyors are used between -20° C and 125°C, and special situation belts can be used up to 170°C. Belt conveyors of total length from a few meter to 500km have been reported. Belt widths change from 300 mm to 3200 mm. Today capacities up to 20000 ton/hours are reached. Conveyor belts have a carcass made of textıles normally consıst of several superimposed pliesed. The purpose of this textile carcass is to take up the tensile forces. The kind of textile carcass and the woven fabrics used are pacing for the properties of the belt. The textile carcass is encased by a rubber coating to protect the textile core from mechanical damage and other external influyeces. The covers and edges of the conveyor belt can either be made of rubber ör of a suitable synthetic material. A steelcord belt, like any other conveyor belt, consists of a carcass vvith a protective cover. Steelcords, adjacent to each other in öne plane, form the carcass. in determination of belt width, the imrortant factors are partide size, percentage of maximum sized partide and flowability characteristics of the material. Due to these factors belt width is determined from tables. Hovvever, this is only an initial value and if the belt speed ( caıculated due to the above belt vvidth ) is smaller than the maximum allowable speed, then it will be taken as real value for the belt vvidth. Othervvise, vvalue of the belt vvidth is increased until belt speed becomes smaller than the maximum allovvable speed. Diameter, length and weight of the support and return rollers are determined due to belt vvidth from the related table. After that, spacing betvveen the support rollers is determined due to belt vvidth and bulk density of material from the related table. If lump size of the material is big ör material is tooheavy, then spacing of the support rollers must be decreased by 20 %. Also spacing of support rollers at the loading section of conveyor is taken as half of the normal value. Spacing of return rollers is taken as 2 times the spacing of support rollers. If conveyor has triple roller groups other than single and straight rollers, thendistance betvveen drums ( drive and driven drums) and the closest support roller becomes important in order to have a good troughed shape of the belt. This distance is also determined due to belt vvidth from the related table. Unit vveight of the belt is determined due to belt vvidth and bulk density of material from the related table. Thickness of top and bottom covers of the belt must be krıown also, since they will be necessary during the design prcedure. They are determined from the related tables due to some properties of material such as abrasiveness and stickiness. A conveyor belt plant can be planned and constructed appropriately only if the follovving informations are known:capasity requirements, nature of material, vvhich vvhould be conveyed, form of material, bulk dencity of material to be conveyed, conveying height and method of feeding. These detaıls are required to calculate the drive povver at the selected belt speed.A higher belt speed resulıs in every case in lovver belt tentions and in most cases a narrow belt. There are no general rules applicable to the selection of the drive arrengment. A multidrum drive indeed leads to lower belt tension than a single drum drive, but the Viii extra motors and gearbpxes may, under certain circumstances, be more expensive than the conveyor belt saving. The simplest drive is mostly the best. Each return drum which can be avoided reduces the number of reversed belt bendings and increases its lifetime.The feed station must be constructed in such a way that the drop heght is as low as posible and that heavy.coarse and stony material is prevented from striking the belt hard. If the belt is stressed under to severe condisions at the feeding station, a stronger belt design is necessary than that calculated on the basis of the belt tension. One of the most important points in the evaluation of power is determination of coefficient of friction. Coefficient of friction of the idler bearings depends mostly on the conveyor conditions as follows: a) Friction factor is taken as 0.03 for conveyors with poor alignment, temporary or portable conveyors operating in extremely cold conditions with frequent stopping and starting or extended operations at or below -40°C. b) Friction factor is taken as 0.022 for permanent or other conyors with good alignment and normal, regular maintenance. c) Friction factor is taken as 0.012 where the braking power of a downhill conveyor must be calculated. d) Friction factor is taken as 0.011 for systems in regular good conditions with respect to the climate, material, environment and the period of maintenance. The motor power is calculated from the formula: Nm=P.v/(1000.s). The pre-tension force for the operating condition of a belt conveyor is determined from the starting factor, the type of tensioning device (movable or rigid) and the location of the tensioning device (at head or tail of plant). Calculation of belt tensions also depended of type of drive:single, two or many-drum drive. A belt conveyor may have a mechanical or countrerweighted(gravity-type) take- up.The latter may in turn be divided into cariage-type and vertikal. In the screw take-up the tensioning pulley simultaneously serves as deflecting tail end pulley and rotates on a fixed shaft or in terminal bearings. The program, using AutoCAD has been writen in TURBOPASCAL programming language. This program includes file which has extension SCR and realizes drawing. This program includes some informations about the belt conveyors and their parts.A way of design of belt conveyors could be shown as the Figure. IX GİVEN DATA CONTROL OF ANGLE OF INCLINATION OF PLANT CALCULATION OF BELT WIDTH AND BELT SPEED CALCULATION OF IDLER ROLLERS AND THEIR LOCATION PRE-SELECTION OF BELT CALCULATION OF POWER BELT SUPPORT CONTROL - SAFETY FACTOR CALCULATION OF BELT TENSIONS SELECTION OF DRIVE-DRUM AND ROTATIONAL SPEED DESIGN OF BEARINGS AND SHAFTS CHOSEN OF LONGITUDINAL AXIS OF THE CONVEYOR CONCAVE AND CONVEX CURVE ANALYSE All Structue of the program should be flexible and it should be open to modification and easy to necessary choices must be presented to user on the screen. In this study, by using a computer selection, calculation and drawing of the appropriate belt conveyors elemants standardizes all desin results and the design conforms the relivant TSE, DIN and ISO standarts.After that results from calculation of belt conveyor are presented us by the program automaticaly using. SCR extansional file AutoCAD draws drawing with given information.This progam calculats and draws the belt conveyor, which is nessesary in industry. At different situations and polutions constructor for many short time can design it and this way optimization and organization of working proces develop.