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author: Some problems often occur during the design and manufacturing process of Li Yimin's bulk material machinery, and these problems are often discovered during installation and use. In order to avoid and reduce the occurrence of such problems, this article lists some common problems. For reference by those involved in design, manufacturing and use. Due to space limitations, this article only lists some of the issues. More issues still require everyone to continuously accumulate and summarize in daily work practice. 1. Regarding capacity parameters, motion parameters and geometric parameters, there are many parameters for bulk machinery, such as the capacity of the belt conveyor, the capacity of the bucket wheel stacker and reclaimer, the capacity of the ship loader and the ship unloader, etc., the belt speed of the belt conveyor of various equipment, the belt width of various equipment, the pitch speed and pitch angle of various equipment, the rotation speed and angle of rotation, the speed range of the cart, etc. These parameters should be adapted to the actual location requirements of the entire system and the site. Any parameter cannot be too large or too small. Too large and too small are detrimental to the system and equipment. Parameter issues actually include two aspects: overall design selection and equipment design. If the equipment parameters are determined unreasonably during equipment selection, the products produced will inevitably have unreasonable parameters. For example: a. In some sites, users select larger values for the parameters of the bucket-wheel stacker-reclaimer's material-retrieving capacity during the overall design. After the equipment is put into production, the subsequent belt conveyor or other equipment is overloaded. During design, the bucket volume of the bucket wheel is often designed to be too large, or the determined material density is smaller than the actual value. In order to reduce excessive material retrieval capacity, users usually replace the hopper or modify the hopper capacity. This problem has occurred on many sites. b. The belt width is too wide and the belt speed is too high. The width selection of the belt is related to the actual ability of the equipment to transport materials. The larger the capacity, the larger the amount of materials passing through per unit time, the wider the bandwidth, while also taking into account the characteristics of the materials. If the material is dense and hard, choose a wider belt. For calculations of belt width and speed, please refer to the free calculation software on this site for calculation. The belt speed should also be calculated based on the principle of moderation. When the particle size of the material is large, the width of the belt takes a larger value. When the belt speed is too high, it is easy to accelerate the wear of the belt and reduce the service life of the belt. Some designers leave too large a margin for the belt speed parameters, making the speed too high, thus reducing the life of the belt. c. Regarding the speed of each mechanism: There are certain principles for determining the speed of each mechanism of bulk material machinery. It is generally related to the capacity of the equipment, the required efficiency of the mechanism, and the inertial load of the motion mechanism. For equipment with a pitching mechanism, the pitching speed is generally described by the front end linear speed. On the premise that the mechanical efficiency can be met, the pitching speed is usually 4-6 meters/minute. Too low a speed will affect the efficiency, and too high a speed will increase the power of the drive motor and cause a large impact when the pitching mechanism is started or braked, which is detrimental to the stress on the steel structure. The traveling speed of the cart traveling mechanism of the bucket wheel stacker and reclaimer, ship loader and ship unloader is generally controlled below 30 m/min. The low speed should be determined according to the process requirements. For example, the bucket wheel stacker and reclaimer should be determined based on the material reclaiming capacity and footage, while the ship loader and ship unloader can take a lower low speed as the working speed. For the rotation speed of ship loaders and ship unloaders with slewing mechanisms, the front-end rotation linear speed is generally less than or equal to 30 meters/minute. The rotation speed of the bucket wheel stacker and reclaimer changes in direct proportion to the reciprocal of the cosine function. When the cantilever is parallel to the track, it is 0 degrees. The speed adjustment angle range is from 0 degrees to 70 degrees, and 70 degrees to 90 degrees is constant speed operation. In the design of the bucket wheel stacker and reclaimer, the maximum rotation speed must be limited, and the maximum rotation speed must be designed based on the reclaiming capacity. If the rotation speed is too low during material retrieval, insufficient material retrieval capability will occur. The rotation speed of the bucket wheel stacker-reclaimer in the material-retrieving state is the linear speed of the bucket wheel when it rotates horizontally. The speed range usually takes a value of 25-50 m/min. For equipment with a large material withdrawal capacity, such as 6000 tons/hour, the speed range is about 50 m/min. For equipment with a small material withdrawal capacity, the speed range is 25-30 m/min. If the rotation speed of the stacker-reclaimer's rotary mechanism is too low, the problem of insufficient material retrieval may occur. d. About geometric parameters: The geometric parameters of the equipment include track center distance, cantilever length, gyration radius, pitch angle, applicable ship pile height and other parameters. These parameters should be determined through careful layout, and must be considered from many aspects such as equipment, material yard, dock front, technology, etc., and cannot be ignored. For example, it is necessary to consider the maximum unloaded tide of the ship, the minimum tide of the full load, the height above the rail and the height below the rail of the material pile, the maximum allowable inclination angle of the belt conveyor at the highest and lowest pitch positions, etc. If the height value under the track in the material yard is too low, it will affect the rotation angle, which means that the bucket wheel cannot pick up the material at the base of the track foundation. There is also a problem of mutual adaptation between the track center distance and the parameters of the equipment. When the selected track center distance is too small, it is easy to cause excessive or too small wheel pressure failures. The above-mentioned parameter problems often lead to errors in the overall or equipment design, which ultimately lead to insufficient perfection of the equipment after it is put into production. On the stacker-reclaimer equipment or the ship-loader equipment, it may happen that the rotation angle cannot reach the actual required parameters due to the limitation of the geometric position. This will cause the actual application functions of the equipment to fail to meet process requirements and cause significant economic losses to users and manufacturers. On belt conveyors or bulk material machinery, such as ship loading and unloading machines, bucket wheel stackers and reclaimers, improper design of the geometric position relationship of the belt conveyor slides will cause material blockage, belt deviation, material scattering and other failures. e. Regarding the power parameters of each mechanism, the power of different equipment and different mechanisms has different calculation methods, and the specific values should be appropriate when making actual selections. Parameters that are too high or too low are detrimental to the equipment. Many users are willing to pursue higher power because they are worried that the power is not enough. In fact, too much power will increase the operating cost of the equipment. The more important point is that as the power increases, the load on some mechanisms also increases when overload occurs. For example, when the bucket wheel mechanism or slewing mechanism of a bucket wheel stacker and reclaimer is overloaded, the load on the steel structure of the entire machine will increase, which directly affects the strength or stiffness of the steel structure of the equipment. For this reason, it is not recommended to increase the margin of the driving motor power of each mechanism of the equipment too much. 2. Mechanism errors. Mechanism errors will occur during the design of the equipment. For example, the pulley magnification is incorrectly calculated in the pitch design or the design of the lifting mechanism and the cantilever telescopic mechanism. ； There are redundant constraints in the drive or transmission mechanism, resulting in shaft breakage. ； Fatigue damage of shaft parts due to calculation errors ； Gear parts have broken teeth due to insufficient strength during design. ； The standard reducer is too small and has a short service life. ； The first-stage transmission gear of the belt conveyor drive device has broken teeth and broken shafts ； The forms or organizational plans determined by some organizations are unreliable, resulting in frequent failures. During the installation stage, it may be found that the mutual installation size or shape is wrong, resulting in failure to install, etc. For important pins with rotating devices, they usually have sliding bearings that need to be lubricated. Special attention should be paid to the installation angle of the pin. An incorrect installation angle will cause the bearing to be lubricated at an angle where grease cannot be added. 3. Structural failure The so-called structure refers to the main load-bearing member that is welded by steel plates or shaped steel and is used to support the main body of the equipment or some components. The structure of these supports is generally composed of box beams or I-beams. Nowadays, most companies use advanced foreign finite element software to perform strength calculations when designing steel structures. There has been great progress in design methods. In general, continuous straight sections of the main structure of equipment are less prone to strength problems such as cracking, while failures are prone to occur at discontinuous locations, such as fractures, open welding, fatigue cracking, etc., especially at the bending points of beams, force transmission points, and connected stiffeners or gratings, which are frequent points of failure. Special attention should be paid to the design and manufacturing process, and the focus of the design should be on the local processing and force transmission of the steel structure component design. There are many major failures or accidents that occur in parts of beams or at force transmission points. In calculations, it is often difficult to simplify the mechanical model close to reality in parts of the structure or force transmission points. The mechanical model and mathematical model established must be as close as possible to the actual situation. Therefore, careful analysis of parts of the beam is required. In addition, the bending radius of the non-straight beam transition section should be as large as possible, because there is a certain degree of stress concentration in this section, and the stress here is much larger than that in the non-bending section. The smaller the bending radius of curvature, the greater the stress concentration. When a fault occurs in an important part, a major accident may occur, with the equipment overturning and the main stress-bearing parts breaking. Therefore, special attention must be paid to the design and calculation of structural parts, especially the design of partial steel structures. In addition, the welding of equipment during the manufacturing stage is equally important. Necessary flaw detection after welding, weld form, welding process, etc. are the conditions for ensuring the quality of structural parts welding. During the installation and use of equipment, there have been many major accidents in China where equipment collapsed due to equipment strength failure, causing heavy casualties and large economic losses. Therefore, attention must be paid to the strength of the equipment at all stages of design, manufacturing, installation, and use. Especially after the equipment is put into production, the bolt connections, welds, and component bodies of the equipment should be frequently observed for cracks, open welding, and fractures. Many devices have problems initially or after some time of application. It is also important to pay special attention to stiffness analysis and calculations when it comes to structures. General stability calculations and local plate and shell stability calculations are difficult to perform in existing application calculation software and should be carefully analyzed. Some equipment malfunctions or accidents occur due to deformation or instability of rods or beams. The results of various displacements of a certain point can be obtained in most application software. After understanding the displacement of each point, further decisions and analysis can be made. It is necessary to avoid deformation or deflection of certain beams of the equipment exceeding the specified value. In addition, water accumulation often occurs in some structures due to improper design, and leaks often occur in the electrical room of the machine room. 4. Control and dragging Since modern mechanical equipment control and dragging systems use relatively many products imported or manufactured by joint ventures, the failure rate of equipment control and dragging systems is relatively low, and its main manifestation is the reliability of all primary detection instruments. Such as the reliability of various limit switches, the reliability of various encoders, the reliability of the mechanical connection of the detection system, etc. The main performance in the design is whether the control and protection system is complete and reasonable. Whether the layout of various screen cabinets is reasonable, and whether the direction of various cables is reasonable and meets the specification requirements. 5. Problems with auxiliary structural parts Auxiliary structural parts are equipment safety protection facilities, such as walkways, ladders, railings, etc. Because they are not the main stress-bearing parts, they are easily overlooked in the design and manufacturing stages. As a result, a certain number of auxiliary steel structure components are found to be inappropriate in size or installation position and assembly method during the on-site installation stage. Ladder railings and walking platforms do not meet the requirements of safety regulations and standards, and the welding quality during on-site welding and installation is unqualified. Such problems require on-site modification or on-site inspection and correction. 6. Other problems In fact, not all design or manufacturing problems are problems that can be avoided or solved with more complex concepts. Often the simpler the problem, the more likely it is to occur. And there are still a lot of them, such as size errors, quantity errors, material errors, and errors in the most basic mechanical concepts. Simple and low-level errors account for about 80 to 90 percent of the total errors. Controlling and reducing simple errors has become the key to improving product quality. Characteristics of bulk material machinery and other general machinery: Bulk material machinery is a large piece of machinery produced in small batches. Most of the products are designed and manufactured for a certain project. They are not like the automobile manufacturing industry where the relative form parameters of the products are relatively fixed and a large number of products are produced. Therefore, there are certain differences in the design and manufacturing of equipment among different users. Because of this, the equipment will inevitably have problems and deficiencies of one kind or another. To improve the overall quality of the equipment, the product must be designed in strict accordance with the product specifications or contract regulations from the beginning. In the manufacturing stage, strict manufacturing processes must be formulated, and through serious and careful design and calculation, the equipment can meet the most complete requirements as much as possible. According to international practice, all aspects of enterprise management must be managed and required in accordance with the ISO 9000 series of standards. Necessary requirements for design work: The most important thing about a product is the design work. The following problems should be avoided during the design work:: You cannot apply it to a certain product when you do not fully understand or understand a certain technical issue. ； Necessary design review or inspection and verification work cannot be canceled because of the tight design work cycle. ； It is not allowed to design based on experience in actual design work. ； Detailed calculations and analyzes are required for all improved products ； Don’t design products you’re not sure about ； Institutions or structures designed by others should be used after understanding them. Do not use them before they are understood or not fully understood. Of course, this is not to oppose innovation or creation. The purpose is to make the designed or manufactured products reliable and truly achieve their due functions and quality. This article is a summary of many years of practical experience research. In fact, it is very difficult to comprehensively reflect a large number of problems in just a short article. This requires most engineering and technical personnel in this profession to discover and solve problems through years of in-depth work accumulation and research. All aspects of enterprises engaged in this industry should understand and deal with technical and quality issues from both economic and credibility aspects. Make the products designed and manufactured truly meet the requirements of the market economy and the requirements of users.