Repost: My opinion on domestic pressure vessel manufacturing enterprises

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I am ignorant and talented, but I took advantage of the convenience of my job to travel all over the country and visited more than ten pressure vessel manufacturing companies. At the invitation of Daystar, I would like to summarize my personal views on this type of enterprise for everyone’s enjoyment. The companies I have visited include state-owned enterprises, foreign-funded companies, Taiwan-funded companies, Hong Kong-funded companies, and private companies. ； In terms of scale, there are small factories with dozens of people, and large units with 700 or 800 people. ； Judging from the company's expertise, there are those that specialize in heat exchangers or graphite equipment, and there are also comprehensive ones that include towers, kettles, furnaces, non-ferrous metals such as zirconium, titanium, etc., and there are also units that are responsible for the production of pressure-bearing equipment for naval submarines. Generally speaking, it basically covers various types of enterprises in this industry, including high, medium and low-end. Because my workplace has special requirements for equipment, I inspected the company mainly to look at the processing capabilities of its stainless steel equipment and the production level of double tube sheet heat exchangers. Below, the analysis will mainly focus on these two points. 1. Stainless steel processing The processing capacity of stainless steel equipment actually mainly refers to whether there is a dedicated processing site and processing equipment to avoid ferrite contamination. When my company ordered the equipment, due to some villain's obstruction, it produced four 316L 100-cubic storage tanks from a very poor company. Recently, when the goods arrived at the site, it was found that the ferrite contamination on the inner and outer surfaces of the tanks was very serious. The contamination in patches and large areas was very difficult to repair. Now they have to be downgraded to ordinary 304 tanks for use. Therefore, the partitioning and processing of stainless steel equipment is very important. Good companies can have specialized non-ferrous workshops, such as Shanghai Sensong, which also have clean workshops for processing titanium, zirconium and other materials. When entering, you need to change shoe covers and wear white work clothes. In slightly worse enterprises, it is also possible to perform partitioned processing, enclosing the white steel processing area and laying wooden boards or rubber mats on the floor. In the worst enterprises, there is no way to separate factories and process areas, and all equipment is mixed together. In terms of processing equipment, good companies have specialized stainless steel processing equipment, such as plate rolling machines, edge planing machines, edge milling machines, roller brackets, etc. The plate rolling machines and roller brackets are wrapped with paper or plastic film to avoid direct contact with the equipment and reduce pollution as much as possible. I didn't have much contact with non-standard equipment before and didn't understand the significance of doing so. Only when I encountered a problem this time did I understand it. In the company I mentioned earlier, the surface of the plate rolling machine was not smooth, causing dents to be pressed out on the surface of the main material of the equipment. ； The iron filings attached to the plate rolling machine are pressed into the main material, reaching a depth of 2~3mm in some places, which is too much to handle. In addition, the equipment was placed directly on the ground during processing, which was contaminated with a lot of iron filings. Finally, large areas of rust spots formed on the surface of the equipment. It was hard to believe that it was made of 316L. In terms of the storage of boards, this is the best company I have ever seen. All boards are placed on rubber mats or wooden boards. Each board is separated by wooden pads and stacked neatly and orderly. For thin plates or other non-ferrous metal plates, a film is attached to the surface to protect them. 2. Processing of double tube plate heat exchanger Single tube plate heat exchanger is a very simple and common equipment, so I won’t go into details. In chemical production, in order to prevent corrosion and dirt, or due to process and labor protection, safety and other requirements, double tube sheet structures are often used for some heat exchange equipment to solve the problem. There are three main connection methods for double tube sheet heat exchangers: rigid, flexible, and open. The so-called rigidity means that the liquid layer cylinder is directly processed from the inner and outer tube sheets. For example, if the width of the effusion layer is 50, then the inner and outer tube sheets each have a circle of bosses with a height of 25, and the excess material is removed directly from the tube sheet. My expression skills are relatively poor, and I don’t know if viewers understand. This structure has no welds between the liquid layer and the tube sheet, which makes it stronger, difficult to process, and wastes a lot of material. Moreover, the leakage test of the expansion joint of the inner tube sheet cannot be checked, so very few use this connection form. The so-called flexibility means that the liquid layer cylinder is a short joint, which is finally welded to the tube sheet after passing the expansion test. It is easy to make and most of them adopt this structure. The open type is simpler, as there is no cylinder in the effusion layer. But this cannot function as a fluid accumulation layer, so not many adopt this structure. This structure is adopted by Shanghai Bayer, and the distance between the inner and outer tube sheets reaches 7 or 800mm. The quality of double tube sheets depends largely on the processing equipment. For example, most manufacturers that can manufacture double tube sheets use CNG drilling machines to equip all baffles with drills and tube sheets with drills, which can improve accuracy and make pipe threading easier. In order to ensure the processing accuracy of the baffles, some manufacturers (such as Jiangsu Shuangliang) use the entire plate blanking process, and then cut off the notch part after the processing is completed. The expansion joint of the inner tube sheet is the most critical process. The best manufacturers can calculate the expansion relay and make corrections based on experiments and experience. ； A little less, determined based on experience and experiments. The controllability of the expansion force of hydraulic expansion is higher than that of mechanical expansion, but the purchase cost of hydraulic expansion heads is high and the loss is large (the average expansion head is more than 100, and a hydraulic expansion head needs to be replaced). The hydraulic expansion head is a one-time use and cannot be repaired. Therefore, few companies use the hydraulic tube expansion method to manufacture heat exchangers. Among the companies I have visited, Shanghai Morimatsu and Kunshan Yongsheng use hydraulic expansion. However, practice has proven that mechanical tube expansion can meet the requirements. Enterprise quality inspection regulations and inspection equipment also have a great impact on the quality of double tube sheets. For example, units with strict management will strictly carry out re-inspection of plates one by one and hydraulic pressure test of heat exchange tubes one by one. Companies with well-equipped equipment use helium leak detection for double tube sheets, but of course the cost will be much higher. Generally, companies use ammonia testing. Morimatsu and Shuangliang use helium testing, and Zhangjiagang Jiangnan Boiler uses ammonia testing. Yongsheng and Morimatsu strictly carried out the hydraulic pressure test of the heat exchange tubes one by one after entering the factory. Jiangnan Boiler omitted this step and only had visual inspection. Generally speaking, I think foreign-funded and Taiwan-funded enterprises have formal management, high technical level, and promising development prospects, but the prices are also very considerable. Compared with state-owned enterprises, private enterprises have better management, higher efficiency, better equipment, and similar technology. The best welding seam I have ever seen, more beautiful than the photos in textbooks, was in a Taiwan-funded enterprise. The equipment produced by this company is very beautiful, and the management is very formal. It is very reassuring to leave the equipment to them. It can be said that the future pressure vessel manufacturing industry will be dominated by such enterprises. After sorting it out a bit today, this is probably what I can recall. I hope you all can enlighten me and discuss it together.