Conveyor Belt

Conveyors are mechanical devices or assemblies used to move items or packages with minimal effort. They usually consist of frames that support rollers, wheels, or belts and may be motor powered or manual devices. Belt conveyors convey material with the help of belt The belt of the conveyor may be of textile, strip steel, woven mesh steel wire.  Conveyors with textile belt  Conveyors with metal belt  Chain driven and rope driven belt conveyors N.B. Conveyors with rubberized textile belts have found the most extensive application. Types of belt conveyors: (i). According to the design a. Stationary conveyors b. Portable & mobile conveyors (ii). According to the purpose c. General purpose conveyor d. Special purpose conveyor Special purpose belts are used to convey hot loads or for operation at ambient temperature over +60°C and -25°C and also for the transport of material chemically injurious to the fabric or rubber cover of the belt. Special purpose belts include heat – resistant, frost resistant, and uninflammable and other types. Geometry of belt conveyor: According to their path of motion belt conveyors are classified as:  Horizontal  Inclined  Combined - Inclined horizontal - Horizontal inclined - Horizontal inclined horizontal - Inclined horizontal inclined

Parts of belt conveyors: 1. Belts: Various types of textile belts are employed in belt conveyors: Camel hair, cotton (woven or sewed), duck cotton. Rubberized textile belts are widely used. Conveyors belts should meet the following requirements: 1. Low hygroscopocity 2. High strength 3. Low own weight (Light in weight) 4. Small specific elongation 5. High flexibility 6. High resistivity to ply (Layer of material) 7. Long service life Rubberized textile belts: Rubberized textile belts are made from several layers known as plies of a rough woven cotton fabric known as belling. The plies are connected by vulcanization with natural or synthetic rubber. Sometimes the plies are made of extra – strong synthetic fabrics, Capron, perlon, nylon etc. 2. Idlers: Generally the belt is supported by idler rollers, in rare cases by a solid wood, or sheet steel, runway or a combination support comprising sections of a runway alternating with idle rollers. Idlers are used mainly in conveyors handling bulk loads, less frequently unit loads, while runways and combined supports are predominantly used for piece goods

According to their location on the conveyors, idlers are classified as upper (supporting the loaded strand of the belt) and lower (supporting the idler return strand of the belt). 3. Centering device: A number of reasons, such as eccentric loading, soiling, sticking of the material to the pulleys and rollers etc., may cause the belt to run crooked. To prevent the belt from running off the rollers, special “Belt training idlers” of various designs are used. These idlers automatically maintain belt alignment with respect to a device (idlers) called centering device. 4. Take ups: A belt conveyor may have a mechanical (screw type) or counterweight (gravity type) take up. The latter may in turn be divided into carries – type (sometimes called horizontal and vertical. In the screw take up the tensioning pulley simultaneously serves as deflecting til or pulley and rotates on a fixed shaft (best design) or in terminal bearings (worst design). In gravity take ups the tensioning pulley (serving simultaneously as tail and pulley) is placed on a movable carriage which is pulled backwards by means of a steel rope and deflecting pulleys. The vertical counterweight take up consists of three pulleys, (two deflecting and one tensioning) and are installed on the return strand of the conveyor. N.B. The carriage type take-up is superior to the vertical type because it is of much simpler design of considerably less height. 5. Drive units: In belt conveyors motive power is transmitted to the belt by friction as it wraps around the driving pulley rotted by an electric motor; the drive comprises the following parts: the pulley (Sometimes two pulleys), motor and the transmission gear between the motor and the pulley. Drives of inclined conveyors include a braking device which prevents slipping back of the loaded belt under the weight of the material conveyed if the current supplying the motor is interrupted. 6. Loading & discharging: Loading depends on the nature & characteristics of the load conveyed and the method of loading. Example: Charging For piece goods  various types of chutes are directly loaded onto the belt. For loose materials  feed hopper Discharging: Generally employed by - Scrapper ploughs - A throw – off carriage known as tripper (only used for bulk materials) N.B.: The discharge plough is a board placed at a certain angle α to the longitudinal axis of the belt and fastened on a frame. 7. Belt Cleaner: In case of dry particles: The clinging dry particles are cleaned by scrapper/wiper In case of wet and sticky materials: Revolving brushes are used Scrappers are mounted on  end pulley Brushes are mounted on  lower num. Belt cleaners are mounted near the discharge pulley

8. Automated hold back brakes: A sudden stoppage of a loaded inclined belt conveyor may cause slipping back of the loaded belt. This will happen if longitudinal component of load weight which is larger than the forces of frictional resistance to belt motion. - To prevent this type of spontaneous movement of the belt, a special hold back brake is mounted on the main or auxiliary shaft which keep inclined in conveyor. - It is a special protecting device which automatically disconnects the drive when the belt slips on the pulley. 9. Conveyor frame: - It is a supporting structure of the conveyor & is usually electrical welded - Consists of longitudinal beams, up-rights & cross pieces - The height of the frame is usually 400 – 500 mm - The spacing between upright is 2 – 3.5 m

Application of belt conveyors: 1. Convey great variety of unit loads & bulk loads 2. Foundry shop to convey mold or sand 3. Deliver fuel in power plant 4. Distribution of molding sand 5. Coal or ores mining 6. Cement & food industries 7. Carry articles of light weight in line production from one operation to another. Advantages of belt conveyors: 1. High capacity 500-5000 m3 /hour or more 2. Ability to transport loads for long distance (500-1000m or up) 3. Simplicity in design 4. Comparatively low in own weight 5. Reliable source 6. Convenient operation 7. Less skill required to operate Disadvantages of belt conveyors: 1. Not suitable for hot ashes & slag. 2. Not suitable granular, powder 3. Abrasive material can cause defect in conveyor Flight Conveyor Ordinary solid flight conveyors consists of essentially of open trough secured on frame work, along with runs the putting member fitted the terminal sprockets & pulleys and takes its motion from drive unit & it initially tensioned by take up.

Working Principle 1. The material to be conveyed is loaded into the through at any point along the carrying run & is pushed by the flights. 2. Discharge can be effected at any point through openings in the trough, shut with gates or sliding doors. 3. Both the lower and upper strands of the conveyor can served as loaded stands. 4. When necessary it can convey materials simultaneously in opposite direction. Application 1. Convey various powdered, granular & free flowing lump materials. 2. Mostly using coal mining operations. 3. Transport hot ashes & slug. 4. Special cable-disk conveyors are employed for handling piece goods such as wood, pulpwood etc. Advantages 1. Simple design 2. Ability to convey in both direction. 3. Easy loading & unloading at any point along the conveying run. Disadvantages 1. Crushing & breaking of the materials during transportation 2. Rapid wear of trough & moving parts. 3. Can not transport load for long distance(50-60m) 4. Low capacity & it is (150-200) tons per hour. Different Parts of Flight of Conveyors Trough: The Trough is a welded structure made of 4-6 mm sheet steel of rectangular or trapezoidal or of rolled profiles.  Troughs may be stumped of sheet steel.  In conveyors designed to handle light-weight materials (such as sawdust, grail etc ). The trough may be of wood.  The clearance between flight & trough should be (3-6) mm.  The trough is assembled of 4-6 m long sections. Drive Unit: The drive unit is of the usual type, commonly supplied with a reducing gear.  It’s duty to protect gear against breakages in case of an accidental overloads Take Up Unit: The take up chain & flight conveyors is of the screw or spring and screw type.  The adjustment length should be nit less than 1.6 times the chain pitch. Frame Work: The frame work of flight conveyors is generally welded of rolled profiles & assembled of separate sections. Flights: Flat rectangular flight symmetrically fastened on roller chains to carry the flights have found the most extensive application.  Are one of the most frequently used types is the box-type flight conveyor with having longitudinal slide plates. Pulling Member: The reliable and effective operation & long service life of a conveying machine will be ensured if the pulling member wraps freely around drums, sprockets & pulleys of small diameter.  Combines high strength & low weight.  The conveying machine without a pulling member will not fit into general classification as they have no identical purpose. Difference between belt conveyor & flight conveyor Belt Conveyor 1. Can not transport hot ashes & slag. 2. Ability to convey in one direction. 3. Loading and unloading takes place at the specified position/fixed point. 4. Can transport load for long distance (500-1000m or more) 5. High capacity. 6. Comparatively low in own weight. 7. Less skill required to operate Flight Conveyor 1. Can transport hot ashes & slag 2. Ability to convey in both direction. 3. Easy loading & unloading at any point 4. Can not transport load for long distance (50-60m) 5. Low capacity (150-200 tons per hour). 6. Comparatively high in own weight. 7. Comparatively skill required.