Study On Operating Theory Of Long-distance Extensible Belt Conveyor And Its Tension Control Technology

An extensible belt conveyor is important equipment for transferring bulk solids on fully-mechanized coal faces,which normal operation may guarantee coal amounts and production efficiency for the coal face and be a key point.At present,collierys producing 10 millions-tons coal per year are more and more in our country,which results in that the extensible belt conveyor for coal surface may have longer haul and greater transportation amount.In recent years,the extensible belt conveyors with the longer haul and greater transportation amount have frequently had a serious accident in their practical operating,which tells us a real fact that in this aspect our researching work is lag in production needs,especially in being how a belt tension change and controlled during starting,stopping and tails moving forward on time of operating for non-stable state movements.In this article,being a studying object for the longest distance and the biggest transportation amount by the present domestic coal mines with the extensible belt conveyor,a dynamics model of a discrete system for a conveyor is carried out through analyzing on belt viscoelasticity using the Voigt model,for which modeling and simulating are carried out using the AMESim dynamics analysis software.In this article,dynamics researching results are obtained in two processing conditions of the staring and stopping for the idling and full loadings.Four special points are mainly analyzed(forehead driving pulley input point,middle pulley input point,tail drum input point and tightened pulltey output point)for their belt speeds,displacements,accelerations and belt tensions.Moreover,the tensioning forces and speeds of a take-up winch and the displacements of a take-up carriage are investigated in processing of starting in a condition of operating of idling and full loading,from which the optimal starting time and speed curve are determined.In this article,being our researching project,stopping operating of the a type of 6 kilometer extensible belt conveyor has conducted,in which there are two different working conditions,one is a controllable stopping and another free and power failure one.Speeds,displacements,decelerations and tension forces changes of the belt have been studied in the different stopping situations for each analyzing points,respectively.Meanwhile,tension forces and speeds of the take-up winch and displacements changes of the take-up carriage are studied,from which the optimal starting time and speed and an adjusting method under different stopping conditions are determined.Those researching results provide a theoretical basis on designing for a take-up device with variable frequency speed regulations and a buffer device.In this article,it is carried out mainly on the studies of the conveyor belt’s displacements,changing features of speeds,tension forces and driving forces on head and middle driving pulleies,tension forces of take-up winch and tension speed changes when the extensible belt conveyor’s tails are moved forward automatically during performing.Those problems are analyzed on the practical performing of the extensible belt conveyor under special working conditions.Relationships of materials changing and tension forcing are investigated.A reason of the problems of belt overlapping and frames pouring of the extensible belt conveyor is explored,from which the periodic variation rule of the minimum tension point along the positions of the belt is studied,and a relevant solution method and strategy are proposed,which is also tested in the scene.The problems above mentioned have been solved by this method.A method of solving on the problem with the vibration happened in the belt storage unit is proposed through analyzing of the reasons of the vibration and the relationships of the vibration and the tensions and distances between two idlers.Under guiding of the theoretical analyzing results of the extensible belt conveyor’s operating in the conditions of non-stable states with starting,stopping and tail’s moving forward,a method and stagey has been formulated on controlling of belt tensioning forces,and developed a new type of device of automatically tensioning with the variable frequency speed regulation and a buffer device used in a condition of the power failure.A dynamic analysis,commercial and sits tests are made.The test results indicated that those mechanisms may satisfy the different requests for the tensions under varying operating conditions for ultra long distances,greater transportation amounts of performing with such extensible belt conveyor.A new type of device of automatically tensioning with the variable frequency speed regulation is developed using comprehensively mechanical kinetics theory,dynamics simulation software and the modern testing technology and the method combined the theory with the simulation and testing to study the theory of operating and the control of tensions for the extensible belt conveyor,which may be used in solving the practical problems.