Application Analysis of Belt Scale in Port and Thermal Power Plant

The belt scale installed in port and wharf is used for commercial settlement, which requires good stability, good repeatability and high weighing accuracy. Based on the above requirements, the belt scale using multi roller suspension scale is used. For example, Shanghai port is jointly developed by many domestic manufacturers of belt weighers, and six sets of weighing roller suspension scales are used as the commercial settlement evidence for weighing by ships; Shanghai Baoshan Iron and steel company uses two groups of suspension weighing roller scales of Kubota, Japan, to weigh ore trade settlement from Australia; Beilun port, Ningbo, Zhejiang Province, is a complete set of equipment imported from Japan, Yama  To) commercial Weighing and measurement of two sets of roller suspension scale frame of company; Yingkou Xiangcheng port in Liaoning Province is a suspended scale frame which introduces Japanese big and technical technology. Therefore, all scales used in commercial measurement are made of high precision scale frame. In order to improve the weighing accuracy and long-term stability, Shanxi Xinyuan automation instrument company has developed the conventional two sets of idler, three sets of idler and four sets of idler suspension type to two four sets of supporting rollers in series into eight sets of double scale stands. The instrument adopts double channel input, the scale frame increases sampling time, and the stability and accuracy are improved, but the installation conditions are improved, The difficulty of debugging has increased obviously. In order to improve the accuracy and long-term stability of commercial measurement, Nanjing Sanye Industrial Co., Ltd. has developed an array belt scale. The so-called array type is composed of two roller straight bearing scales with multiple units, which can collect a large amount of weighing data. The weighing accuracy should be quite high, the technical content of field installation and commissioning is higher, and the installation conditions and technical requirements are higher. It is found that most of the products are used in the mining industry to weigh on horizontal belt, and the accuracy of measurement is also improved. The application environment of commercial scale is basically long belt conveyor, with good belt quality and good circumference from tens of meters to hundreds of meters. The belt width is 1200mm-2000mm, and the belt thickness is 10-15mm; The high flow transportation is 800t / H ~ 2250t / h, and the maximum flow is up to 6000t / h; The material is evenly transported and the phenomenon of material breaking is less, which is very beneficial to weighing. It is not conducive to weighing that the belt runs faster, and it is usually 1.6m/s ~ 3.15m/s. But the flow is large, the performance is stable, and the high accuracy can be obtained with more collection amount. The fuel metering management of thermal power plants generally adopts four roller suspension scale frame for the commercial measurement of coal in the plant, and the coal business measurement of the mine mouth power plant is used as the commercial accounting measurement. As an internal assessment, four sets of weighing roller double bar trunnion trunnion support scale frame are generally used as the internal assessment. The accuracy of weighing is lower than that of the incoming coal, and the cost is lower than that of the coal in the plant. Therefore, it has low sensitivity, but good stability, and is suitable for weighing with large flow, so it can be widely used in coal metering in thermal power plant. This scale frame is also used in coal preparation plant to calculate coal preparation quantity. In Shouyang fenlei coal preparation plant, Shanxi Xinyuan automation instrument company adopts Ramsey technology to produce belt scale frame supported by four supporting roller trunnions with double bar bar. The different is that channel steel is used as main lever and auxiliary lever instead of rectangular steel pipe. Whether the deflection of the equal distance between them is completely equal has not been obtained. Because the belt length has the choice of the best position for the selection of the scale frame, the belt tension device has a certain compensation effect on the belt tension change. The conditions of straight section before and after the scale frame can also be met. The technical requirements of Yamato corporation are five groups of roller distance before and after the scale frame. Ramsey technology requires that the straight line section is four sets of roller before and after the scale frame. The port belt scale can be regularly inspected and calibrated at the dynamic zero point when there is no ship incoming materials. The thermal power plant has two transport and standby conveying lines, and it can also conveniently complete the regular inspection and dynamic zero point calibration, which can guarantee the weighing accuracy of the belt scale. The author has conducted field test for more than 30 days in Taishan Power Plant in Guangdong Province, which proves that the belt has large conveying capacity, fast conveying speed, belt width, belt length, thickness and good belt quality. The tension of high-quality belt changes little, so the short-term zero stability and long-term zero stability can meet the standard of belt scale assessment.

In a power plant in Fujian Province, when the author re commissioning and inspection qualified, it used half a year. The three-stage rubber ring belt has a section of torn belt, and different types of belts are replaced. The belt hardware is different, and the belt winding degree is different. The symmetrical re production changes. The experience and lesson is that the same belt machine should use the same type of belt. In a power plant in Jilin Province, it is tilted 16 ° The suspension scale frame is installed on the belt conveyor. The manufacturer is not sure that the suspension scale rack is installed on the inclined belt for more than 6 °， This indicator is the conclusion that researchers have done experiments, that is, more than 6 ° The symmetry weight has an effect. The vertical limit bar tightly pulls the inclined gravity under the scale frame, which can not affect the weighing! The measured belt conveyor tilt 21 in a power plant in Shanxi Province °， The scale frame of double bar and four supporting roller indicates that the inclined belt shall not exceed 17 °， Some manufacturers mark no more than 18 °、 twenty °， This not only causes repeated weighing of materials, but also affects the weighing of belt scale. The pattern belt can be used to solve the material sliding and repeated weighing, and the balance frame of double bar and multi idler exceeds the weighing level limit. That is to say, the belt does not have the conditions for installing the belt scale at all. In port and power plant belt scales are mostly used in high speed, large flow, wide belt and long belt. During the verification, it is specified that 3 minutes or a whole belt time is specified to evaluate the short-term zero stability and 3 hours to evaluate the long-term zero stability. In use, it should be: 24 hours to assess short-term zero stability, 168 hours to assess long-term zero stability. The stability of belt scale is essentially to evaluate the belt change, the change of belt moisture is completely opposite to the change of belt surface moisture. Therefore, the key to evaluate the belt scale is to evaluate the quality of belt and the belt tension tension device. Some conveyor design departments, just carry the materials on. Excellent designers, considering the maximum flow rate of conveying capacity, common flow, belt wear degree, power consumption and belt tension change, select belt tension tension device to make the belt work in the best condition, and also give the belt scale the best condition

Good installation conditions. The conveyor belt length of thermal power plant is generally 300m-400m, and the inclination is 10 °～ eighteen ° In the strong lifting state, the four sets of double bar bar four sets of roller scale frame are generally used. According to the technical conditions of national standard GB 10595-89 belt conveyor, it is installed in the conveying system of thermal power plant. In order to prevent belt slipping and over tension, that is, belt floating phenomenon, the tension is basically constant. The car type tension device, heavy hammer type tension device and zyj50024d belt hydraulic tension device are adopted. The dynamic zero stability of belt scale is effectively stable. Considering the maximum flow rate of conveying capacity, common flow, belt wear degree, power consumption and belt tension change, the belt tension tension device is selected to make the belt work in the best condition and provide good installation conditions for belt scale. There are still many people who have studied the durability of the belt scale in recent years. The author thinks that the durability test of the belt scale is of little significance, whether it is 3-5 years, or 7-8 years of technology exchange technology exchange21. It is not so much the durability of belt scale, but also the durability of belt. The key is to see the belt durability time. When the belt scale is eroded by different environmental pollution, the corrosion of the metal body by humid, dusty, sulfur trioxides and toxic and harmful gases, some scales are rusted in less than half a year on the site, and rust is caused by water washing in coal transportation every day. The processing technology of the scale frame is generally painted with rust proof paint, finish coat, blue, blackened and galvanized, so as to save production cost, Many scales are only painted with one coat of finish paint, and rust begins to rust at the collision place during installation. After sales service found that the belt scale frame of coastal power plant rust to death less than a year. The power plant is divided into state maintenance and planned maintenance, and now it is called spot inspection (local maintenance) and face-to-face inspection (comprehensive overhaul). The rotating part of the belt conveyor system is worn faster, and the local spot inspection is more. Replacing a belt and a weighing roller all involve the durability of the belt scale. Why the belt scale verification period is set as year, which is derived from skin

Planned maintenance of belt conveyor is also scheduled in. Many large conveyor maintenance plans are 3-5 years, and the quality and maintenance of the conveyor are even 10-30 years. The accuracy of weighing will not exceed the error range naturally when the transportation is in good condition.

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