Conveyor Belt

A new generation of soft-start device for belt conveyor application

A new generation of soft-start device for belt conveyor application   conveyor system

  
 
Source: Resources Network Author: Jian-Feng Li Release Date: 2009.08.24
    In recent years, with the long-distance, large-capacity, high-power appearance of belt conveyors at home and abroad have developed a variety of types of soft-start device. Yanzhou Mining (Group) Co., Ltd. and its subsidiary coal mine great efforts in this regard, the positive application of the current application of new technologies has been, and was jointly conducted with the relevant scientific and technological research, in the soft-start research and application of belt conveyors to achieve remarkable achievements in the domestic counterparts have considerable reference value.

    Analysis of a belt conveyor soft-start device

    At present, the commonly used large-scale belt conveyor equipped with a hydraulic speed soft-start device, BOSS system, variable-speed coupling, CST (COntrolledStarTransmission) system, controllable transmission technology, AC motor soft starter, liquid viscosity transmission and frequency speed control devices. Yanzhou, Shandong University of Technology and Mining (Group) Company Nantun Coal Belt Conveyor soft-start device for these types of characteristics are analyzed.

    In addition to the study conclude that these commonly used large-scale belt conveyor soft-start device has significant advantages, it also pairs of their respective defects are summarized analysis, finally reached the following conclusion: all kinds of belt conveyors soft-start The devices work their own characteristics. For example, BOSS system, soft-start the process of heat great, transmission efficiency is low, can not be achieved without level adjustment, multi-drive power balance required to friction plate wear the cost of film with limited space led to a failure to start a real no-load; CST Control System together with the reducer, bulky, inconvenient to install, configure the backstop in high-speed shaft and brake more difficult; and, BOSS system and the CST system, controllable drive technology because it is expensive to import spare parts, so applications are not widespread, but the CST system is the only way to ensure that in an emergency stop or a sudden loss of power when the drive system to provide controlled parking. Liquid viscosity transmission and frequency control devices because of its internal hydraulic control system complexity, manufacturing and maintenance costs are high, the application is not widespread. When the belt conveyor unit when the power is less than 500kW, variable speed fluid coupling is the best choice for soft-start, despite its soft start-up performance worse than the liquid viscosity methods, there is slip, efficiency loss of about 2%, timing accuracy and transmission efficiency is less than frequency control, and CST. AC motor soft-start because they do not have the power balance and variable speed features, but must be complementary with the coupling constant filling to use, generally used for small and medium non-essential power transmission occasion, but its low cost, simple operation, in underground coal mine trough can be applied on a wide range of telescopic belt conveyor.

    More than two-point belt-driven machine chopper soft-start

    Yanzhou Mining (Group) Co., Ltd. and the Shanghai Branch of Coal Science Research Institute, to take advantage buck chopper soft driving principles, successfully developed a multi-point buck chopper-driven belt conveyor soft-start fully digital control technologies and products in order to facilitate the maintenance, control, precision, and so on to start a smooth demand.
QJR1-300/1140 Soft Start Control with English SSD591 all-digital transmission controllers, there are a number of internal re-configurable number of modules, through the appropriate combination of the speed loop and current cut-off to form a negative feedback loop. Closed-loop control method for the PI regulator. After a variety of power protection circuit module signal filtering and configuration, from the original selected several dozens of kinds of protection of the necessary protection. A given signal generator is programmable through the input of the slope, slope acceleration time and switching the input settings, you can easily control the tape speed up the time and switching time.

    In order to automate management requirements for coal mines, the soft starter operating in ways which can be directly started, you can also remotely start. At the same time can also be feedback to the superior control system to start, run and fault three groups of passive contact, for superior control system programmed to use. Currently used by coal mine belt conveyor, mostly multi-point multi-motor drive mode, in order to avoid the starting current, using the direct control of startup sequence to start when they use the delay method, so that several time-drive motor to start. As the soft starter to the starting current for the effective control, so start allowing several soft starter to start at the same time. In order to make several motor load balancing, soft starter with master-slave control mode, define a soft starter for the host, the rest is from the machine, the soft starter for the speed and acceleration control by the host to complete, from the plane to track the host state, to achieve current balance goals. In practice in the use of multi-point-driven belt conveyor, two drives of up to 1km distance between points is about current balance control signals in order to ensure reliable transmission, using a reliable V / F and F / V conversion technology for controlling the jamming signal, and to avoid long-distance transmission of the signal attenuation problem.

    3 belt conveyor viscous soft start device for liquid

    To date, Yanzhou Coal Mine Machinery Factory has developed a 150kW, 200kW, 500kW three kinds of fluid viscous soft start device, and a large belt conveyor in the major coal mining administrations successfully used the nearly one hundred sets achieved with -type machine slow, full, smooth start-up and multi-motor load balancing, reduce the strength and reducing motor with a capacity of 30% ~ 40%, has obvious economic benefits. Viscous learn new developments in the past 10 years, up a brand-new discipline. Viscous soft start device within the transmission mechanism is based on Newton’s law of friction. It is located between the asynchronous motor and reducer to accept power electric motors to drive the load rotation. Fluid pressure by controlling the size of the control shear film thickness, so as to realize soft-start device of liquid viscosity output torque control to achieve the purpose of soft start conveyor.

    They have considered two scenarios:

    Spring-Action. Through the piston oiling to pressure increases, the pressure plate springs to push the friction piece torn off. At this time, the motor no-load to start. Stepper motor control by using digital pressure valve so that oil pressure gradually reduced, the gap between the friction plate (cut oil film thickness) gradually decreased, so that the input and output rotational speed difference gradually smaller, until both ends simultaneously, to achieve right The purpose of soft start conveyor.

    Hydraulic-Action. By the hydraulic oil in the piston forces generated by the combination of the friction piece, springs back to places where the role play. Does not work, because of the pressure cylinder without oil, so the friction piece is out of state. When the conveyor needs of Kai car, first empty Kai motor, and then through the hydraulic system to lubricate the fuel tank. With the pressure gradually increased, the piston to overcome the elastic force of the spring will be clearance between the friction plate slowly getting smaller, the output shaft torque increases, the last friction plate that is fully integrated, no relative rotation, soft-start process is completed.

    Hydraulic-action with the spring-action to make the biggest difference is that with the force of friction films from different sources, the control mode is also quite different. Hydraulic-action in the biggest drawback is that after the end of Kai Tak vehicle hydraulic oil must maintain a certain pressure value, or will affect the normal use of conveyors.

    4 belt conveyor viscous soft start device development

    Yanzhou Coal Mine Machinery Plant from independently developed by a “belt conveyor viscous soft start device”, a better solution to the mine, port, etc. to use a huge amount of belt conveyor smooth start this one have long plagued manufacturers and the user’s problem, filling a gap in the domestic, but also makes conveyor machine fuel prices are therefore dropped about 30%.

    It is understood that this newly developed belt conveyor viscous soft start device is the use of liquid viscosity and shear film principle to achieve the output stepless speed adjustment, is a suitable long-distance, large capacity belt conveyor on the set of mechanical, electrical, hydraulic equipment in one can make a large belt conveyor start acceleration is regulated within the large-scale and control.

    Production site strongly suggests that the use of practice: This viscous soft start device in large-capacity, long-distance belt conveyor, in particular at the start when fully loaded use less than 0.3 can belt conveyor in accordance with m/s2 acceleration of smooth start, the minimum acceleration can be achieved 0.043m/s2, and to be able to 0.01 ~ 0.10m / s, within the scope of any regulation of speed, not only reduce the impact, greatly reduces the tension borne by tape, but can also significantly reduce tear tape, motor and other mechanical and electrical burn accidents, ensure the safety of machine operation, reliability, and maximizing the service life of parts made good practical effect, the economy and social benefits are significant. Experts believe that: the results of this study the technical performance of similar products in China as the leading level, and has a relatively high value of the promotion.

    5 large belt conveyor speed soft start fluid couplings Good

    Achieve the soft start conveyor machines take many forms, but the most widely used to be the number of variable speed fluid coupling consisting of soft-start mode. Yanzhou Coal Mining Area in recent years, investment in bandwidth, complete sets of 1.2m, the captain 1000m and the total power of more than 3 × 200kW fixed large-scale powerful underground belt conveyor 17 units, of which from the Yanzhou Mining (Group) Corporation developed mechanical system for repair works of 15 NTU power, high belt speed, multi-motor, large capacity belt conveyors, are used by the variable speed fluid coupling consisting of soft-start system, and has been affirmed in major coal using the site.

    Variable speed fluid coupling mainly by the rotating component, for the row of components, speed control devices, fuel tanks and coolers cabinet composed of such components. In fact, the fluid coupling is equivalent to a combination of centrifugal and turbine pumps. When the pump wheel rotation, behind the formation of the oil cavity rotating oil ring, allowing the oil level within the flow channel with the row of the oil phase to adapt to the oil chamber for the pump to the flow passage supplied a certain amount of oil, spoon equal amounts of the oil discharge pipe. When the spoon pipe move outward, the oil  Sidewall Conveyor Belt  ring thickening; the contrary, the oil ring thinning. In this way, by adjusting the device to manipulate the movement spoon pipe, with increasing or decreasing the thickness of the oil ring to increase or decrease by saying that we can achieve the purpose of stepless speed manual or automatic.

    Variable speed hydraulic coupling of the soft-start has the following characteristics: ① to improve the startup performance of belt conveyor. ② multi-drive the power balance. ③ enhance motor and tape life. ④ to reduce the impact of the grid. ⑤ easy to implement remote control and the central belt conveyor centralized control. ⑥ improve the reliability of belt conveyor is running. ⑦ has a very high performance and low cost. The experts pointed out: As the variable speed fluid couplings on the soft-start manner the many advantages of belt conveyor, if we can replace the constant filling coupling applied to the underground high-power telescopic belt conveyor is also bound to be a significant effect, currently being carried out experiments to explore the relevant units, variable speed fluid coupling soft-start will have a more broad application prospects.

    6 frequency conversion technology in the application of belt-driven research

    Yanzhou Mining (Group) Corporation Integrated Equipment Rental Station Frequency carried out in the application of mine belt conveyor research, summed up the use of inverter and inverter to drive the motor to the belt conveyor features.

    ① truly soft start conveyor. Soft-start feature will be the use of inverter motor soft start and soft-start combined conveyor, belt conveyor driven by motor slow start slow start, the tape within the slow release of energy stored can be played conveyor stop to minimize the impact generated when, almost on the tape not to cause harm.

    ② to achieve multi-motor-driven belt conveyor when the power balance. Application of Frequency on the belt conveyor drive generally used when a drag a controlled, multi-motor drive used master-slave control, to achieve power cracked.

    ③ tape with a strong reduction. As the converter start-up time in  Oil Resistant Conveyor Belt   the 1 ~ 3600s adjustable conveyor start-up time is usually 60 ~ 200s within a set of field conditions. Starting time extended significantly reduced with a strong demand for reducing the initial investment in equipment. Practical applications, due to start reducing the impact of mechanical systems as well as reduce wear and tear, in particular, rollers and roller life expectancy was extended several times.

    ④ inspection with features. Low-speed testing with the main function is to belt conveyor maintenance requirements. VVVF speed control system for the exchange of non-polar transmission, with a state inspection in the no-load adjustable 5% ~ 100% of rated speed with a speed within the scope of any band.

    ⑤ overloaded smooth start. Maximum operating frequency inverter output 1.5 times the rated speed, the most suitable for heavy starting.

    ⑥ automatic speed control. Inverter with the coal flow sensors can be automatically adjusted according to the severity of the load tape speed, energy-saving at the same time also reduces wear and tear tape.

    ⑦ energy. Is mainly reflected in the system power factor and system efficiency in two aspects. Under normal circumstances, coal mines motor margin in the design of a larger work, the vast majority can not be loaded with running the motor operates at full voltage, full load speed often very small, there are part-time no-load operation. Electric light load stator current active component is small, mainly non-reactive component of excitation, so power factor is very low. Using inverter drive, the power factor in the whole process up to 0.9 above, significant savings reactive power. Moreover, the motor and reducer directly to the hard link between the change, reducing the fluid coupling, the total system transmission efficiency increased by 5% ~ 10%. In addition, because mine are usually distant from the substation, the voltage fluctuation at different times are also relatively large, the use of the automatic voltage regulator function of frequency converter is also part of the energy-saving effect. In the match after the coal flow sensor can also automatically based on the size of the automatic speed control of coal flow.

    7 inverter soft start in the belt conveyor system
    Yanzhou Mining (Group) Company of Jining III coal mine owners from seven coal flow transport belt conveyor transport system components. Among them, a total of four northern belt conveyor drive unit, each motor power of 31.5kW, rated voltage of 1140V, the original has been using a motor + Coupler way to drive. Since the input ZJT type 1140V mining flame-proof and intrinsically safe after the smart transducer to achieve a soft start of belt conveyor running, use the results very satisfactory.