Question regarding the material of the skirt seat and foot bolt seat
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The material of the tower bottom for the tower equipment is 304, and the height of the skirt is 2000 mm. According to SH3098, the material for the skirt is also specified as 304. Then should the foundation ring, reinforcement plates, and cover plate for the anchor bolts also be made of 304?
Take another good look at 3098. It is not necessary to use 304 material for the entire skirt base; a transition section can be incorporated, and the material of this transition section must be the same as that of the tower. The skirt base shell below the transition section can be made of carbon steel (depending on the design temperature), while the foundation ring, reinforcement plates, and cover plates of the anchor bolts are all made of carbon steel as well.
This isn’t necessary. A transition section can be added above the skirt base; 304 material can be used for this section, while Q245R can be used below it. For the foundation ring plates, cover plates, and gusset plates, Q245R is a more reliable choice, though Q235B can also be used. The length of the transition section is generally selected to be no less than 300 mm; if the temperature is too low, it should be no less than 500 mm. You can look up specific information; there are requirements specified in 3098.
Thank you! According to Section 3.3.3 of SH3098, for skirt bases that meet the requirements for having a transition section but whose height is less than 2.5 m, it is not necessary to provide such a transition section; in this case, the material of the skirt base shell should be the same as or similar to that of the head of the tower reactor. What I want to ask is about the material selection in this situation.
Thank you! Perhaps my question wasn’t expressed clearly enough; see floor 4 for details.
If the temperature is extremely low or high, could there be problems with the bolt material Q235B?
The design temperature for the foundation bolts is determined based on the ambient temperature, namely the average monthly minimum temperature plus 20°C; it has nothing to do with the operating temperature of the tower bottom
A transition section can also be provided when the skirt seat height is less than 2.5 m; the length of this transition section should be 4 to 6 times the thickness of the insulation layer, with a minimum length of 500 mm.
You can take a look at the appendix of JB/T4710-2005, which specifies the materials for foundation bolts in detail. Other standards can also be referred to. For example, SH/T3098-2011.
Stainless steel is also recommended for anchor bolts, as carbon steel is prone to corrosion
Is this used in actual projects upstairs? Using stainless steel for anchor bolts is too costly; the corrosion rate in soil is generally very low, so a corrosion margin of 3–6 mm is sufficient. It is estimated that stainless steel anchor bolts are only used in extremely rare soil conditions