New method for continuous weighing of tubular belt

New method for continuous weighing of tubular belt

[Abstract] This article introduces the principle composition and working mode of a new type of continuous weighing and measuring device, and emphatically describes the realization and control of intermittent static weighing of two weighing hoppers. While ensuring the effectiveness of environmental protection, it solves the problem that the tubular belt cannot be continuously weighed and measured. The system realizes the continuous conveying of materials by the tubular belt, and the purpose of rapid and accurate measurement.

[Keywords] continuous conveying; static weighing; tubular belt; method

At present, the environmental protection requirements of technological transformation projects are getting higher and higher. Tubular belts have received widespread attention for their environmental protection, moisture resistance, and high efficiency. The technological transformation of Saintbond company actively adopts the new process of tubular belt conveying, and the clinker lime powder from the lime plant is directly conveyed to the steel plant through the tubular belt. The application of the new technology, while highlighting the characteristics of environmental protection, moisture resistance, and high efficiency, has encountered considerable difficulties in weighing and measurement. Due to the bending of the tubular belt, it cannot meet the technical requirements for the installation of electronic belt scales. It solves the insurmountable problem in the application and promotion of new technology. Xinyu Iron and Steel Company broke the traditional electronic belt scale dynamic measurement method and successfully developed two weighing buckets for static weighing in turn to achieve the purpose of continuous, rapid and accurate measurement, and solved the technical problem of tube-shaped belt weighing and measurement. A new effective way has been found for belt weighing and measurement.

1. Scheme and composition

The basic design scheme: the material (lime powder) conveyed by the tubular belt is continuously conveyed to two weighing hoppers. The two weighing hoppers adopt alternate static weighing, alternate loading and unloading, and fast unloading and slow loading. The time gap is generated through quick unloading and slow loading, which not only ensures the static weighing of the weighing hopper, but also ensures the continuous conveying of the material by the tubular belt, realizing continuous, fast and accurate weighing and measurement. The system consists of two weighing hoppers, control devices, video and remote devices, etc. As shown in Figure 1.

Figure 1 Schematic diagram of the composition of the tubular belt weighing system

Figure 1 Schematic diagram of the composition of the tubular belt weighing system

1. Weighing bucket

The weighing hopper is composed of a weighing sensor, a weighing controller, and a limit device. The configuration of the weighing hopper should meet the technical requirements of the corresponding accuracy level.

(1) Selection of load cell

The load cell should be a column or bridge sensor, which has good side load and impact resistance, and is easy to install and maintain. Main technical parameters: ①Accuracy grade 0.03%; ②Sensitivity 2.0mv/v; ③Output impedance 350Ω±3Ω; ④Overload capability 150%.

(2) Weighing controller

Main technical parameters: ①Linearity: 0.01%; ②Input sensitivity: 0.2uv/d; ③Full-scale input signal range: 0～10mv; ④A/D conversion speed: 10 times/second; ⑤Internal part degree: 1 million yards ⑥Display division number: 60000 yards; ⑦The influence of zero temperature is ≤0.2μv/℃; ⑧The influence of full-scale temperature is ≤10ppm/℃; ⑨Sensor excitation power supply: voltage: DC15V±0.3V, maximum excitation current: 240Ma. Main functions: ①With automatic and manual calibration methods; ②With two main and secondary displays, the main display is the cumulative display, and the secondary display is the current display; ③It has the batching control mode; ⑤With automatic accumulation of discharge value; ⑥With relay control contact output (4 pairs of normally open and normally closed); ⑦With 4 standard analog output interfaces; ⑧With RS232 (or RS485) communication interface and 20mA current loop; ⑨With Conventional power solutions such as power failure protection.

(3) Limiting device

The system adopts a collision limit device and is installed near the sensor. The collision limit not only acts as a horizontal and lateral limit but also supports and protects the hopper in the vertical direction due to the inclination of the sensor. The weighing controller displays the accumulated weight on the large screen on-site through a 20mA current loop interface. The system is well grounded to ensure that the system can effectively prevent lightning strikes.

2. Control device

The control device consists of an intermediate feeding bin, a feeding and discharging valve and control equipment. A flap is set in the middle feeding bin to control the loading of the 1# and 2# weighing hoppers, and the feeding and discharging valves can be electric or pneumatic. Figure 2 shows the schematic diagram of the control system. The flaps in the middle feeding bin and the discharge valves of the two weighing hoppers are controlled by a single item, that is, closed when the power is turned on, and opened when the power is turned off, indicated by WK (WK1 is the flap in the middle feeding bin, and WK1 and WK2 are 1 #, 2# weighing hopper discharge valve), W is the contact output of the upper and lower control limits of the weighing controller. When the weighing weight reaches the set upper limit, the discharge contact (W discharge) opens the discharge, and closes when the discharge reaches the lower limit, and controls the discharge valve. The feeding belt control takes the contact according to the requirements of the electrical equipment, and the KH switch is used to select manual or automatic.

When the weighing hopper or other equipment (such as flaps, discharge valves, etc.) fails and cannot work normally, the control signals in the weighing controller and control cabinet will be input to the control room, alarm and stop the tubular belt conveyor from working .

3. Video and remote device

Two cameras are used, one camera monitors the entire working status of the weighing hopper, and the other camera must be able to see the cumulative weight displayed on the two large screens.

Automatic weighing articles

Figure 2 Schematic diagram of the control system

The remote device adopts a digital optical transceiver. The digital optical transceiver adopts a dedicated ASIC design and high-speed DSP technology, and a fully digital uncompressed, non-destructive broadcast-level transmission method. High definition and high resolution realize long-distance transmission through optical fiber with high quality and no damage. Use a pair of digital optical transceivers to remotely transmit video signals and RS232 (or RS485) signals to the measurement room via an optical core.

Second, the work process

The lime powder conveyed by the tubular belt passes through the flap in the middle feeding bin and falls into the 1# weighing hopper at the lower limit setting (hopper empty). When the lime powder weight of the weighing hopper reaches the upper limit setting (bucket full), the weighing controller of the weighing hopper will output two signals. One way to control the flap in the middle feed bin to switch, switch the material from 1# weighing hopper to 2# weighing hopper, 1# hopper scale feeding is finished, the weighing controller performs weighing collection, and the current displayed weight automatically accumulates To the cumulative display; another signal will open the discharge valve of the 1# weighing hopper for discharge. 2# weighing hopper is feeding at this time, 2# weighing hopper is feeding at the same time, 1# weighing hopper is discharged to the lower limit setting (bucket empty), at this time, the weighing controller of 1# weighing hopper sends out Bucket empty signal, close the discharge valve of 1# weighing hopper. The 1# weighing hopper is now in the state of waiting for material preparation. When 2# weighing hopper feeds to the upper limit setting (bucket full), repeat the same action of 1# weighing hopper.

The accumulated weight of the weighing controller is the automatic accumulation of the value of each unloading. The sum of the cumulative weight of the two weighing controllers is the total weight of the material (lime powder) conveyed by the tubular belt.

Three, other

1. The opening of the discharge port of the weighing hopper should be determined according to the maximum flow rate of the tubular belt. It is necessary to ensure that the discharge flow rate is larger than the feed flow rate to realize the "fast unloading and slow loading" working mode.

2. Two weighing hoppers alternately weighing and unloading can not only greatly reduce the capacity of the weighing hopper, but also the required height difference is also small. However, the capacity of the weighing hopper should be as large as possible based on the site conditions, so that the frequency of action of the flaps in the intermediate feed bin can be greatly reduced, and the service life of the equipment can be prolonged.

3. The load cell should be installed on the load-bearing beam. When steel structure is used as a load-bearing beam, it must have sufficient rigidity, otherwise, reinforcement measures should be taken to enhance the rigidity of the beam. Choose a weighing hopper with three load cells. When the discharge port is seriously deviated from the center of gravity of the hopper scale, load cells should be installed on both sides of the vertical bisector corresponding to the discharge port to form an isosceles triangle.

4. The weighing hopper adopts a fully enclosed system, and the material receiving port, discharge port and dust removal device must be independent and adopt soft connection. When the material is powder, the discharge valve of the weighing hopper should consider the sealing device. Reduce dust and point leakage, and ensure accurate measurement.

5. The surface of the cone part of the weighing hopper, the splitter plate and the flap, which are easily worn by materials, can be added with a wear-resistant layer. The material of the wear-resistant layer can be ultra-high molecular weight polyethylene.

6. The weighing hopper should be equipped with a special support for weights so that the weighing hopper can be calibrated regularly.

7. The system has two working modes: automatic and manual.

Four, concluding remarks

The system uses closed double scales, interlocked control, low system integration cost, easy implementation, and good environmental performance. Since it was put into operation, it has been operating in good condition, realizing continuous, fast and accurate weighing and measurement. The commissioning of the system has reached the domestic advanced level, highlighting the perfect combination of environmental protection and accurate weighing. It has accumulated useful methods for the weighing and measurement of tubular belts