Research on improving the reliability of steel drum sealing
Liu Guoliang, the 3602 factory of the Chinese People's Liberation Army
Seal reliability is a very important quality characteristic in many quality requirements of steel drum products. For a steel drum, if its sealing performance is poor, although other quality characteristics (such as surface quality, coating, coating, geometric size, etc.) are good, the main function of the steel drum is lost, but it is only one. Only scrap, this is well known. From a statistical point of view, in a batch of dangerous goods steel drum products, although most of them are good, even if only one seal is unreliable, this is not allowed for manufacturers and users. It is necessary to carry out various researches to ensure that the factory products are 100% qualified. Therefore, it is particularly urgent and important to improve the sealing reliability of steel drums.
First, the necessity of conducting product reliability research
At present, under the conditions of establishing a socialist market economy in China, enterprises are asking for the focus of competition on quality. The reliability of product quality is a common concern of designers, manufacturers and users, and an important indicator for comprehensive evaluation of product quality. Therefore, it is necessary to carry out research on product quality reliability with modern emerging engineering science.
The reliability of a mechanical product refers to the ability to perform a prescribed function under specified conditions within a specified time. In this definition, three â€œregulationsâ€ and one â€œfunctionâ€ are involved.
(1) â€œIn a specified time periodâ€ means that there is a certain time requirement for maintaining the quality and performance of the product, as reliability varies with time. For steel drums, it mainly means that after the contents are contained, there should be no leakage and deterioration of the contents during the specified service life. This is an important design indicator.
(2) "Under specified conditions" means the conditions of use of the product, such as density, temperature, humidity, load, impact, medium, etc. For steel drums, different types of barrels should be adapted to different media. Galvanized barrels, spray barrels, and ordinary barrels are not suitable for the contents. Second, the performance of the double and double round side barrels is different. Steel drums with Class I performance requirements of the International Maritime Regulations must be triple rounded. This is the main technical indicator and requirement for the design of packaging containers.
(3) â€œSpecified functionâ€ means the accuracy, strength, stability, etc. of the product. For steel drums, in addition to the theoretical capacity, nominal capacity, material thickness and material requirements, the number and size of the closures are also specified.
(4) Under the specified time, conditions and functions, the product may meet the requirements or may not meet the requirements. This is a random event. Random events can be quantitatively described by probability. The probability that a product will perform a specified function under specified conditions within a specified time is called the reliability of the product. Clearly, reliability is a measure of the probability of product reliability.
From the definition of reliability, we can recognize the need to conduct reliability studies. When steel drums are used to contain dangerous articles that are flammable, explosive, corrosive and highly toxic, if one of the steel drums leaks due to poor sealing, resulting in burning, explosion, corrosion and poison, it will be given to people. The loss of life and property brings huge losses, especially for export products, and the consequences are even more serious. Therefore, the user must be satisfied with the absolute and reliable product quality to meet the different levels of user needs.
With the rapid development of science and technology, product upgrading has accelerated, especially in the petrochemical industry. The requirements for packaging containers are increasing, the scope of use is wide, the environment for use is more severe, and the reliability of steel drums is more prominent. The viewpoints and methods of reliability have become an indispensable basis and means for quality assurance, safety assurance, and product liability prevention.
Second, the factors affecting the reliability of steel drum sealing
As we all know, the steel drum production process is:
After this production process, the factors that affect the quality of the product naturally involve all aspects. These factors, including people, machines, materials, methods, and the environment, all have varying degrees of impact on the quality of the product. Therefore, every employee who requires the company to engage in management and production positions should be clear about the quality responsibilities and tasks that they undertake, and do their jobs with a high degree of responsibility. Only in this way, with excellent work quality, we can guarantee the manufacture of high quality products. This is one of the main contents of a quality assurance system established and improved by the company.
At present, China's steel barrel industry generally has problems of low management level, outdated equipment and low personnel quality. The quality of the products produced is poor, the consumption of raw materials is high, and the economic benefits are not good. The quality of the products has always stayed at the level as long as it does not leak. Rarely work hard to study how to improve the reliability of the problem, resulting in difficult product quality, export earnings is difficult. The main reason is the low technical content. The barrel production technology is too simple. The consequence is that the stamina is insufficient and the competitiveness is not strong. Therefore, it is necessary for us to seriously study the production process of steel drums.
Steel plates for steel drums must be purchased according to national standards. More attention should be paid to reducing the damage on the surface of the steel plate in the transportation process. Strict inspection is required before production, and unqualified steel plates (geometry size, shape, surface condition, etc.) are not transferred to the production process.
In the process of shearing, it must be cut strictly according to the process regulations. Strictly control the edging of the wavy edge and the é•°JJ curved steel plate, because this steel plate will stop the subsequent process, increase the scrap rate and affect the quality of the hem. We know that the crimping of the barrel is strictly required. If the dimensions of a steel plate are inconsistent, the difference is very large. In some places, the winding layer is too thick, and in some places, the winding layer is not enough, which will reduce the sealing reliability of the steel drum.
The edging process mainly ensures the welding quality to remove the surface oxide layer of the domestically produced hot-rolled carbon steel sheet. Cold rolled steel sheets can not be used in this process. In the edging process, the oxide layer in the specified range (15-20 mm) is ground. Grinding, cornering, and the presence of these defects can lead to weld seam de-welding, burn-through, weld head cracks, and the like. It will undoubtedly affect the sealing quality of steel drums, such as seam leakage and poor sealing of the coil.
It is necessary to strengthen the adjustment of the welding specification of the seam welding process and the finishing of the roller to prevent defects caused by poor welding process.
It is necessary to strictly control the angle of the edge and the height of the edge of the barrel. Usually the angle of the edge should be 95 Â° + 5 Â° edge height inspection should use a special template. The quality of the trimming process is closely related to the quality of the steel drum. If the edge angle and the edge height do not meet the specified requirements, the number of curling layers may be insufficient or the thickness of the rolled layer may cause leakage of the iron tongue. Therefore, this process should be included in the quality management point, and key control should be carried out to select high-quality employees to operate in the process.
The focus should be on the inspection of the barrel cover. Pay attention to the uniformity and thickness of the glue. If the glue film is not continuous, there is a blank, which causes the center rubber ring of the roll to be cut off, which does not form a complete seal ring, thereby greatly reducing the reliability of the seal, especially the impact resistance.
In the assembly process of the barrel and the top (bottom) of the barrel, the quality of the curling directly determines the level of sealing reliability, so the position of the curling roller should be checked regularly. This process is prone to problems such as loose curling, loose tongue, sharp corners, insufficient winding layer, and the shape or structure of the coil does not meet the requirements. The presence of these defects affects the tightness of the steel drum.
Third, measures to improve the reliability of the seal
The problems that arise from the sealing of the steel drum are mainly the closure and the crimping assembly, so only the two problems will be discussed below.
1. The seal of the closure. GB325 "Packaging Container Steel Barrel" national standard stipulates that the steel drum is allowed to have one injection port and one venting port and only one injection port. This provision reflects its flexibility. The number of installed closures can be agreed between the manufacturer and the user. At present, from the perspective of the use of domestic steel drums, the general contents are extracted by open injection or by electric and manual pumps, so there is no pressure balance problem in the barrel. When in use, the general user does not open the vent for the convenience of the drawing. This shows that the venting port has a poor practical effect. I think there are at least two advantages to removing the vent: one, economic. To install a vent, you need to install 4 more parts. Plus the total labor cost is 2 yuan. This is a very impressive number for high-volume production companies. Second, the lack of a vent reduces the number of leaks. Because the GB13251 standard stipulates the type of steel drum sealer as shown in Figure 1. This type of closure is a double seal.
The sealing structure shown in Fig. 1 is the same as the sealing structure of Fig. 2. In Figure 2, the plug, gasket, and top (bottom) of the closure form a tight sealing barrier. It can effectively prevent the leakage of the contents of the barrel. The elasticity of the structural ring shown in Figure 1, the cross-sectional dimension, the rigidity of the top of the bucket, in the state of the material and geometrical dimensions of the gasket, if the top of the bucket is deformed by a large impact load, the liner will be removed from the top of the bucket, resulting in leakage. Because the leakage of such a structural closure is simply not compensated, this is the biggest drawback of the structure. Figure 2 shows the structural type. The disadvantage is that the inner end of the barrel is higher than the inner surface of the top of the barrel, so that the contents cannot be dumped clean. This problem can be solved by the structure shown in Figure 3, that is, two 2-5mm holes are drilled on the coil. Another disadvantage is that if the coil is not assembled properly, the coil will easily fall off. This problem can be solved by improving the assembly. Moreover, the assembly of some plastic spiral coils abroad is also adopted in this type. Therefore, the sealing reliability of the structure shown in Fig. 2 is higher than that of Fig. 1.
2. Measures to improve the reliability of crimping assembly sealing
Some in-depth research has been done on the steel barrel community at home and abroad. But I think that although these studies are more scientific, they still have a lot of experience. Most of them only use the abstract fuzzy lines to outline the curling structure. Even the GB325 national standard indicates the curling structure. Therefore, the current understanding of the curling is shallower. The following is a set of realistic research pictures to analyze the various models of the curling and its feasibility in practice.
(1) The structure of a rectangular five-layer rectangular bead is shown in Fig. 4. Molding requires two crimping wheels to complete. The first crimping wheel completes the primary occlusion state of the hem (as shown in Figure 5). This state is the basis of the formation of a close five-layer curl, but the layer is loose. The tight crimp shown in Figure 4 can only be formed by the action of the two crimping wheels.
The shape of the rectangular bead should be rounded and the corners should be rounded, and the sharp corners and tongues shown in Figure 6 should not appear. The sharp corner phenomenon is caused by improper adjustment of the roller or uneven thickness of the material. The roller is improperly adjusted, so that the material at the layer is forcibly flowed to the gap at the transition R between the sealing plate and the bottom cover to form a sharp corner, or a metal tongue is formed to flow into the gap between the roller and the barrel. The sharp corners or the iron tongue cause stress concentration and thus affect the overall rigidity of the bead, so that the impact resistance of the barrel is significantly reduced. Seriously, due to poor carrying capacity, the barrel will be filled with the contents and will be dropped during the turnaround.
(2) The arc-shaped curling edge believes that the structural form of the circular-shaped curling edge should be as shown in Fig. 7. The so-called seven layers should be seven layers along A or along the B direction. This form of corrugated sealing channel is longer than the five-layer bead and has a larger bead diameter A or B. Knowledge of material mechanics indicates that the rigidity of a circular member depends primarily on its diameter. That is, the diameter is large, and its rigidity is strong. Rigidity refers to the ability of a component to resist external forces without deformation (yield). The round crimp shown in Figure 7 can be machined from our existing equipment and is therefore feasible. Three rollers are required to implement the structure. There are high requirements on the shape and size of the roller, the adjustment position, the stretch size of the lid, and the geometry and shape of the barrel edge. The ability to achieve seven layers of round crimping can greatly improve the reliability of the barrel's crimp sealing. This is the direction of our efforts.
Despite the incomparable superiority of round curling, in the actual development, some barrel mills lacked the correct theoretical guidance, often rely on experience, or imitate some data or samples, without in-depth study of the corresponding technical data and theory. You can use it if you mistakenly think that someone else has a successful model (or drawing). The result is counterproductive. The root cause is the process structure and technical details of the undigested and absorbed related materials when introducing the sample or data, which leads to the separation of motivation and effect.
Most people think that steel drums are a product with low precision requirements. This view is incorrect. On the surface, the steel drum is a rough product, but like other products, it has rough places and places where it is demanding. We must treat this differently and we cannot generalize it. We have to be "thick" and "fine" appropriate. It is possible to appropriately relax parameters that have little effect on the functional requirements. For parameters that have a large impact on function, we must take it seriously and analyze it carefully. It must be strictly controlled from the aspects of parts, molds, equipment precision, etc., and each quality can be closed to produce high-quality, high-reliability steel drum products.
At present, the method of processing the steel drum's crimping roller is generally adopted. First of all, let's not talk about whether the sample itself is reasonable or not. Suppose it is reasonable, but the comparison test is still an approximation. The accuracy that this method can achieve is relatively low. It is unscientific for the process of crimping which requires high precision. Because it is difficult to ensure that the accuracy of a batch of rollers is within a certain range. This brings discomfort to equipment adjustment, roller adjustment, geometrical dimensions of product parts, and the ability to guarantee product quality.
At present, the method of manufacturing and repairing the rolled roller of the steel drum industry adopts the method of sample comparison processing. The roller quenching hardness of most manufacturers is very high. Once the groove is worn, it is ground and repaired with a grinding wheel and the sample is inspected. I think it can be improved by the following ideas. Now the two rollers are made of high quenching hardness to improve the wear resistance. Instead, the combination of wear-resistant â€œsoftâ€ material and high-hardness roller is adopted, that is, the first wheel is made of high hardness to ensure strength and Abrasion resistance; the second roller can be processed with a wear resistant material such as cast iron or bronze. This can ensure the life of the crimping groove, and it can be repaired by molding. It can basically ensure the accuracy of the groove shape. For a roller with high quenching hardness, it can be made of carburized steel. The carburized or infiltrated alloy elements are used in the processed groove-shaped parts to improve the wear resistance of the groove-shaped working parts and achieve uniformity of wear resistance and strength. After wear, the grinding wheel can be used, supplemented by the forming method of the forming car) to improve the machining accuracy. The quality of the beading is avoided due to fluctuations in the geometry and geometry. I think this is a new way to improve the quality of the manufacturing of the hemming.
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