29-03-2014, 03:23 PM
Belt Conveyor
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INTRODUCTION
The belt conveyor is an endless belt moving over two end pulleys at fixed positions and used for transporting material horizontally or at an incline up or down. The main components of a belt conveyor are:
1. The belt that forms the moving and supporting surface on which the conveyed material rides. It is the tractive element. The belt should be selected considering the material to be transported.
2. The idlers, which form the supports for the carrying and return stands of the belt.
3. The pulleys that support and move the belt and controls its tension.
4. The drive that imparts power to one or more pulleys to move the belt and its loads.
5. The structure that supports and maintains the alignments of the idlers and pulleys and support the driving machinery.
Application
Conveyor belts are widely used in mineral industry. Underground mine transport, opencast mine transport and processing plants deploy conveyor belts of different kinds to adopt the specific job requirements. The main advantages of conveyor belt system are:
1. A wider range of material can be handled which pause problems in other transportation means. Belt conveyor can be used for abrasive, wet, dry, sticky or dirty material. The lump size of the transported material is limited by the width of the belt. Belts up to 2500 mm wide are used in mining industry.
2. Higher capacity can be handled than any other form of conveyor at a considerably lower cost per tonne kilometre. Conveyor belts with capacity of 11000t/h and even higher can be deployed to match with higher capacity mining machinery.
3. Longer distances can be covered more economically than any other transportation system. A single belt conveyor or a series of belt conveyors can do this. Belt conveyors can be adopted for cross-country laying.
4. By the use of many forms of ancillary equipment such as mobile trippers or spreaders bulk material can be distributed and deposited whenever required.
5. Many other functions can be performed with the basic conveying like weighing, sorting, picking, sampling, blending, spraying, cooling, drying etc.
6. Structurally it is one of the lightest forms of conveying machine. It is comparatively cheaper and supporting structures can be used for many otherwise impossible structures such as crossing rivers, streets and valleys.
7. The belt conveyor can be adopted for special purposes (fire resistant, wear resistant, corrosion resistant, high angle negotiation etc.) and can be integrated with other equipment.
INFORMATION REQUIRED TO DESIGN A BELT CONVEYOR
1. Length of conveyor from centre to centre of end pulleys.
2. Inclination-level or inclined. Either degree of inclination, or distance to be lifted or lowered.
3. Average capacity per hour.
4. Maximum capacity per hour.
5. Material to be conveyed, and weight per cubic foot. 6. Average size of material.
7. Size of largest pieces and percentage in feed.
8. (a) Nature of material -dry or wet (moisture content).
(b) Abrasive or corrosive?
9. How material is to be fed to the belt and particulars of feed point or points.
10. How material is to be discharged from the belt i.e. overhead pulley or by trippers, and particulars of discharge points.
11. General indication of supporting structure.
Pulley
A conveyor belt system uses different types of pulleys like end pulley, snub pulley, bend pulley etc. as shown in the Figure 3. The end pulleys are used for driving and sometimes for making tensioning arrangements. Snub pulleys increase the angle of wrap thereby increasing the effective tension in the belt. The pulley diameter depends on the belt width and belt speed.
Pulleys are used for providing the drive to the belt as well as for maintaining the proper tension to the belt.
Minimum transition distance as shown in Table 4 should be followed while placing idlers in front of pulleys.