subject: Acceleration Control And Tension Test For Belt [print this page] In the good old days, a single horse driven cart was extended to two, four or six horse stage coach to cope with the increasing demand of passenger load. To ensure comfort to passengers from a sudden starting jerk, the horses were trained to move the coach very gently and gracefully. And when the horses galloped to full speed, they were whipped and controlled to ensure proper load share, thus avoiding an overturn or failure of components. Similarly, when belt conveyors grow longer, from 1 to 2 kilometres to 8 to 15 kilometres and haul 3000 to 4000 tonnes per hour over significant inclines and declines, the complex profiles place unusually stringent demands on the starting/stopping procedures, drive configuration on primary and secondary pulleys at the head end, tripper stations in the mid-sections and the booster station at the tail end. A conveyor belt is a non linear visco-elastic medium in which strain can propagate at some finite wave speed. Long conveyor belt is a gigantic rubber band full of elasticity and load inertia dynamics which can result in destructive consequences if not properly understood. Perhaps the most difficult conveyor characteristics to overcome are the velocity and tension waves present in the belt. In a conveyor with head drives only, these waves tend to propagate to the slack side of the belt where they are attenuated by friction and the take-up mechanism. When a fully loaded conveyor belt is started abruptly or with no acceleration control, high acceleration forces induce tension waves that can adversely affect the belt fabric, belt splices, drive pulleys, idler pulleys, shafts, bearings, speed reducers, motors and couplings. This can cause performance problems in vertical curves, excessive belt take-up movement, loss of drive pulley friction, spillage of materials, and festooning of the belt fabric. Therefore the drive system must produce a minimum torque powerful enough to start the conveyor, and controlled such that the acceleration forces are within safe limits. To understand better the velocity/acceleration ramp relationship, let us assume a conveyor starts with velocity increasing linearly at 0.1 meter per second. The acceleration will remain constant at 0.1 m/s2. After 40 seconds the belt attains its full speed of 4 m/s. At this point the acceleration will drop to zero. This is not a good method of starting a conveyor as the jerk at the very first instant will be a huge spike, then remains constant, which could be detrimental to conveyor performance. If the belt splice section happens to be at the drive pulley at the instance when a fully loaded belt is started abruptly, the starting jolt can rip the belt. The ability to control the drive acceleration torque providing a smooth soft start while maintaining belt tensions within specified safe limits is critical for belt conveyors performance. Soft controlled start drives on a long conveyor with multiple drives protect the belt and other conveyor components and help reduce investments costs.As the professional manufacturer of complete sets of mining machinery, such as Ball mills,Sand washing plant,Aggregate jaw crusher, Henan Hongxing is always doing the best in products and service.
