【Weekly Topic】Key points in the design and manufacturing of floating-head heat exchangers:
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This post was last edited by gn_1984 on 2015-12-14 at 16:23. To increase the popularity of the heat exchange section, a 【Weekly Topic】 activity is organized there; this helps to foster an active atmosphere for technical exchanges while also providing members with certain financial rewards. Key points in the design and manufacturing of floating-head heat exchangers: These focus on aspects that need attention during the design process, including structure and calculations. We hope everyone will share their opinions on what they consider to be important during the design or manufacturing process, as well as areas where mistakes are likely to occur. We will give points and encouragement to everyone based on the content. Thank you all for your support. Other content: AC version of heat exchange equipment – “One question per day” competition post (prizes for participation; valid indefinitely) http://bbs.hcbbs.com/thread-1320941-1-1.html. The selection process for active users and “Weekly Stars” in the “Mechanical Section” has begun http://bbs.hcbbs.com/thread-1489069-1-1.html. Recruitment for moderators and technicians in the [Mechanical Section] – applications and referrals are welcome. [Valid indefinitely] – Come if you’re interested! 】http://bbs.hcbbs.com/thread-1288857-1-1.ht【Mechanical Section】In-depth Guide to Preventing Freezing of Equipment Over Winter http://bbs.hcbbs.com/thread-1502793-1-1.html Chemical Equipment and Machinery
This post was last edited by gn_1984 on 2015-12-14 at 16:24. The structural design of the floating-head heat exchanger: The single-pass floating-head tube structure consists of a hemispherical head, corrugated expansion joints, tube sections, a flat cover, Flange A, Flange B, Flange C, fasteners AB, fasteners BC, a cone, and the tube-side outlet flange, as shown in Figure 1. An opening is made in the dome-shaped cover, and a short section is provided; this short section connects to the corrugated expansion joint, which in turn is connected to flange A through another short section. Flange A and flange B are joined together using fasteners AB. Flange C is pressed by fasteners BC against the front and rear sealing surfaces of flange B, thereby forming an integrated structure with the flat cover. This design not only facilitates installation and disassembly but also effectively addresses the thermal stress differences between the tube side and the shell side. http://www.360bhe.cn/uploadFile/fckuploads/image/jg20130219110858.jpg Given that the pressure and temperature in both the tube side and shell side of the feed gas preheater are quite high, the tube sheet, floating head, and floating head connections (including the expansion joint sections) were designed to withstand a maximum pressure difference of 1.0 MPa between these two sides. This approach ensures the safety of the equipment while also helping to minimize costs. The design parameters for the bellows expansion joint are: design pressure of 1.0 MPa, design temperature of 400°C, and material of 0Cr18Ni9. The structural dimensions of the bellows expansion joint are as follows: the outer diameter of the wave root is 510 mm, the wave height is 50 mm, the number of waves is 6, there are 2 layers, and the thickness of each layer is 2.5 mm. The displacement amount of the expansion joint is determined using the following formula: e = L. In this formula, αt represents the average linear expansion coefficient of the heat exchange tube material between the design temperature and 20°C, while αs represents the average linear expansion coefficient of the shell material between the design temperature and 20°C, both in units of 10 mm/(mm·°C). tt is the design temperature of the heat exchange tube, ts is the design temperature of the shell, and to is the temperature of the manufacturing environment, all in degrees Celsius. L represents the length of the fixed ends on either side of the expansion joint, in millimeters. By substituting the values from this example into the above formula, we obtain e=3.2mm. In this example, the material of the bellows is 0Cr18Ni9, with a tensile strength of t = 111 MPa. Based on equations (6-1) to (6-7) in the literature, it can be concluded that the circumferential film stress σz caused by internal pressure in the straight section of the bellows is less than 3.9 MPa
The single-pass floating head tube structure consists of a spherical crown head, corrugated expansion joints, tube sections, a flat cover, Flange A, Flange B, Flange C, fasteners AB, fasteners BC, a cone, and a tube-side outlet flange, as shown in Figure 1. An opening is made in the dome-shaped cover, and a short section is provided; this short section connects to the corrugated expansion joint, which in turn is connected to flange A through another short section. Flange A and flange B are joined together using fasteners AB. Flange C is pressed against the front and rear sealing surfaces of flange B by fasteners BC
Key points in the design and manufacturing of floating-head heat exchangers
When designing floating-head heat exchangers, it is necessary to take into account corrosion allowances on both sides of components such as the tube sheet, spherical floating head, and floating-head flanges； No corrosion margin is considered for heat exchange tubes, etc ； During manufacturing: The pressure testing fixture is quite special and requires specialized design and fabrication. The pressure testing process should be carried out in at least three steps ； The outer cap portion belongs to the shell side ；
When designing floating-head heat exchangers, it is necessary to take into account corrosion allowances on both sides of components such as the tube sheet, spherical floating head, and floating-head flanges； No corrosion margin is considered for heat exchange tubes, etc ； During manufacturing: The pressure testing fixture is quite special and requires specialized design and fabrication. The pressure testing process should be carried out in at least three steps ； The outer cap portion belongs to the shell side ；
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