Application of Large-capacity, Multi-arc and Long Belt Conveyor System in Longkou Hydropower Station

Abstract: The Yanziya finished aggregate conveying system consists of a 6km long curved belt conveyor with a head-to-tail height difference of 130 meters. The conveyor has four arc-shaped turning sections with a radius of 1000m and bears 6.5 million tons of finished sandstone bone. Material transfer mission. This paper analyzes and introduces the long belt conveyor from the aspects of long rubber system layout, process design and equipment selection.

Key words: dragon opening; long tape machine; application

I. Overview

The Longkou Hydropower Station is a compacted gravity dam with a capacity of 1.8 million kw. The total concrete volume of the main project is 3.55 million m3. The Yanziya sand and gravel processing system undertakes the task of processing 6.5 million tons of finished aggregates. The finished aggregate is transferred to the dam area. The transfer yard is undertaken by a 6km long turn belt conveyor. The bright line segment is 912m, and the total length of three tunnels is about 5097m, of which the maximum length of a single section is 2733m, and the clearance dimension of the tunnel section is 4.5m×4m. The belt conveyor spans the Zhongjiang River Gorge between the two mountains, with cliffs of more than 70 degrees on both sides, and the terrain is steep, crossing the Jinhe Village and Longkou Village. The construction and installation of building foundations are affected by various factors and are difficult.

Second, the tape machine design parameters selection

1. Conveyor line and tape winding form

2. Conveyor belt selection

The conveyor belt acts as a traction and load bearing in the conveyor. The conveyor belt transports 6.5 million tons of aggregate without replacement, and the joint is vulcanized. According to the calculation, the parameters of the conveyor belt are as follows: the conveyor belt model is ST1600, the steel cord core belt has a bandwidth of 1200mm, the belt quality is qd=35.5kg/m, the belt thickness is 20mm, the wire rope diameter is 5mm, and the upper and lower cover rubber thickness is 7mm.

3. Roller type and structure

The selection of the idler is related to the bearing capacity, life, load size, width of the conveyor belt, running speed, operating conditions, working system of the conveyor, material to be transported, bearing life, maintenance and other factors. The types of rollers of the machine are: grooved idlers, parallel (or V) idlers, buffer idlers, and self-aligning idlers.

4. Drive unit

The driving device is composed of an electric motor, a liquid-viscous soft start, a speed reducer, a flexible coupling and the like. The heart and power source of the conveyor directly affect the running stability of the entire conveyor, the life of the machine and the cost of manufacturing and use.

5. Motor

Model YKK5002-4, power 560KW, cooling mode air-to-air cooling, voltage level 10kV, protection class IP54, insulation class F. The motor has a box structure.

6. Liquid sticky soft start

Model YNRQD-560/1500 liquid viscous soft starter. The motor can start at no load, reduce the impact on electrical and mechanical; can provide adjustable, smooth, non-impact starting torque; can achieve power balance under multi-motor drive; automatic overload protection can be realized when the conveyor is overloaded; In normal operation, the transmission efficiency can reach 100%; the stepless speed regulation can be realized, and the speed regulation sensitivity is high to meet different work needs.

7. Reducer

The gear unit of the drive unit is a SEW parallel shaft reducer with a fan. The utility model has the advantages of high transmission efficiency, stable operation, low noise, small volume, light weight, long service life and high carrying capacity. The model is M3PSF90, the input speed of the high speed shaft is 1500r/min, the rated power is 1121kW, the transmission ratio i is 20, and the heat capacity PG1 is allowed.

8. Brake device

The full-load parking of the belt conveyor is the most difficult condition for braking. If the parking slows down during braking, the dynamic vibration of the tape will cause the local tension of the tape to be too high or too low, which may cause the broken belt and local parts. Accidents such as sagging of the tape. The brake is selected from the cold disc type controllable moving device. The model is KZP-Ф1200/2×100. The maximum braking torque of a single unit is 59kN·m. One set is arranged at the tail of the machine head to control the movement of the conveyor.

Third, the selection of the turning section parameters

1. Turning section structure and turning radius

The turning of the belt conveyor is to raise the curve in the conveyor belt of the turning section and install the roller obliquely, so that the turning section of the conveyor generates the outward thrust through the idler during the running, and overcomes the tension caused by the turning of the conveyor belt. Internal shifting ensures normal operation of the conveyor belt when cornering.

2. Turning section roller structure

The angle of the plane and space is changed by the operation principle of the flexible belt surface of the belt conveyor. The movement and angle change control of the belt conveyor is realized by the friction principle between the belt surface and the driving drum. The belt conveyor has a maximum turning angle of 45.26°. According to the different force of the tape, the AB segment structure, the BC segment structure and the CD segment structure are selected.

3. Tensioning device selection

Tightening with a heavy hammer ensures that the conveyor has sufficient tension to prevent the conveyor belt from excessively loosening between the rollers causing the material to be thrown and increasing the resistance to movement, preventing slippage and ensuring the tension of each point of the conveyor belt to drive the conveyor belt normally. The device has the advantages of simple structure, reliable work and small maintenance, but has certain requirements on terrain and space. There is a gully at 200m from the head of the tape machine, which is at the arc of the D segment. The tensioning device is stretched in the arc segment, which is the first case in the tape machine industry. Because the tension of the arc segment is easy to make the tape run off, and the tensioning device 2 the uneven roller affects its use. life. In the installation and use, the method of adding the guiding roller is adopted to force the tape to smoothly run from the arc running to the straight line within 5m before and after the tensioning. It is proved that the use effect is good, the tension of the device is 190KN, and the tensioning stroke is 20m.

4. Electrical control system

The automatic operation of the equipment is realized in the central control room through the PLC and computer control system. The control system has the detection and protection functions of the main faults, enabling unmanned operation by the machine. It has various main status parameter display functions to facilitate fault analysis. It is equipped with accessory devices such as belt conveyor deviation, slip and emergency stop switch. The main control contents include accurate measurement of conveyor speed and detection of computer closed-loop control status; realization of slip protection and overspeed protection; start and stop of conveyor under various working conditions Automatic control for various protections and alarms.

5. Auxiliary equipment for distribution

The tunnel ventilation is provided by an axial fan, and the fan is arranged at 100 meters. The lighting along the line and the tunnel is illuminated by waterproof, dustproof and anti-corrosion 80W fluorescent lamps with a spacing of 20 meters. A special sound and light system for the conveyor is used along the line; a fire water supply pipe is provided, and a pressure reducing valve and joint are provided every 50 meters.

Fourth, no-load, heavy-duty debugging operation and its effect

1. If the starting time is too short and the starting acceleration is too fast, the speed and tension of the conveyor belt will be negative. Excessive deflection will be caused by the pressure of the conveyor belt as a flexible body, which is not allowed. When the soft starter is used, the starting acceleration increases from zero. When the starting time reaches a certain value, the starting tension is greatly reduced and the conveyor starts smoothly. The commissioning and trial operation of single machine, multi-machine, no-load and heavy load are strictly carried out according to the commissioning outline. The heavy-duty commissioning is loaded at 20%, 50%, 80% and full load, and the continuous operation of the test run under various loads. The time is not less than 8 hours.

2. Before starting the commissioning, check the speed reducer, brake, drive, electrical signal, electrical control protection, insulation, etc. before starting. During the commissioning process, the bearing temperature, hydraulic oil temperature, conveyor speed, and retarder temperature are in a normal state.

3. The deviation value of the straight section and the turning section of the conveyor should be within the requirements of the national standard; the on-site starting time is adjusted within the range of 40-300 seconds, generally adopting the 90S-150S sinusoidal acceleration starting mode.

4. It can be started 10 times in full load within one hour, once every 6 minutes; realize interlock control with the belt machine before and after.

5. It has protection functions and protection display along the line, such as parking, slipping, deviation, tearing, over-temperature, watering, smoke; it is required to stop along the line and display the corresponding fault point every 100 meters, which is convenient for finding faults.

6. No-load and heavy-duty debugging results, the delivery volume exceeds the design requirement of 2500t/h, and the whole machine system is successfully debugged at one time. After the system is completed, it has been running for 8400 hours, and the finished aggregate of gravel aggregate has reached 6.5 million tons, with a maximum delivery capacity of 2983t/h. The equipment is in good working order.

7. In the head section of the long belt conveyor, the volume of the transfer bin in the dam area is set to 210,000 m3, and only the live volume of the silo can meet the aggregate demand of 17 days of concrete pouring during the peak period. The larger storage capacity can ensure long distance. The tape machine has sufficient inspection and maintenance time and obstacle processing time, except for the daily equipment maintenance, there is no downtime.

V. Conclusion

The long belt conveyor transports the finished aggregate, which has high conveying capacity, large transportation capacity, energy saving and environmental protection, and low transportation cost. The current technology is mature and is gradually applied in hydropower systems, such as Longtan and Xiangjiaba Hydropower Station. The conveyors have all been successful. The long-distance belt conveyor of Longkou Hydropower Station transported 6.5 million tons of finished sandstone aggregates. From the economic comparison point of view, the unit price of belt conveyor is 0.332 yuan/t.km, the total transportation price is about 15.96 million yuan; the distance of dump truck transportation is 18.3. Km, the transportation unit price is 1.55 yuan/t.km; the total transportation price is about 226.96 million yuan. There is also road maintenance and maintenance costs at 7800 yuan / km. The installation cost of the belt conveyor system is about 45 million yuan, which is a very good economic result.

Sandstone aggregate production and stone yard excavation and useless material stripping transportation account for more than 70% of the hydropower station project transportation. A reasonable transportation plan is of great significance to the project cost and environmental protection. For a long time, hydropower stations have adopted more highway schemes. Because the western hydropower stations basically use artificial sandstone aggregates, the material-form conditions are mostly high slopes, the rock mass unloading deformation is heavier, the fractures are developed, and the geological conditions are complex. The cost of road car transportation is often extremely high and the safety risks are high. Partial transportation of finished materials adopts the method of “long belt conveyor”, which has obtained obvious economic and social benefits. As long-distance conveyor belt conveyor has little impact on the surrounding environment, energy saving and transportation economic advantages are obvious, it will be further promoted and applied. .

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