Selection of the length of the tower skirt transition section
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In the book on chemical processing equipment, \"Tower Equipment,\" there is a passage regarding the length of the transition section at the base of towers:..... When the design temperature is below zero degrees or above 350 degrees, the length of the transition section should be determined based on the range affected by that temperature. If this calculation is not performed, the length of the transition section shall be not less than 4 times the thickness of its insulation layer or not less than 500. Regarding this passage, can it be understood as follows: regardless of the design temperature or whether it falls within the aforementioned temperature range, the length of the transition section should not be less than 500, provided that no calculations are carried out.
It should be understood in this way. If not counted, it should be no less than 500
The principle is as follows: heat transfer calculations should be used to determine the equilibrium temperature, thereby yielding the appropriate length. However, this calculation must take into account convective heat transfer and radiative heat transfer, as well as environmental factors such as wind, making it difficult to compute. Reference HG20652 for value selection. When designing low-temperature towers, we use low-temperature materials for the transition section, over a length of 1000 mm.
The length of the transition section at the base of the tower should generally be ≥500 mm and <1000 mm.
According to clause 3.3.5 of SH3098-2000, \"the length of the skirt transition section shall not be less than 300 MM. However, when the design temperature of the tower or its bottom is equal to or lower than -20°C or higher than 350°C, the length of this transition section shall be 4 to 6 times the thickness of the insulation layer, and shall not be less than 500 MM.\" The standard is quite clear on this point
Regardless of the design temperature, as long as it falls within the aforementioned range, the length of the transition section should not be less than 500, provided that no calculations are performed. This is necessary, but not sufficient. For example, it can be 600, but not 450.