deltak2
Structural
- May 14, 2022
- 2
Dear all,
I’m working on the support design of a vertical vessel, as a beginner with little engineering experiences in this field. A short skirt support was finally chosen after some considerations. However, the expansion behavior caused by both the internal pressure and thermal load, the latter in particular, is a big design concern. So my question is how we can minimize the thermal stresses by designing carefully the skirt support, especially the “interface” between the skirt and the base structure which is not a concrete foundation but a steel platform. The skirt would be welded to the lower head of the vessel.
I noticed that similar topics had been discussed in this forum, see e.g. thread794-449461 ( and thread404-224428 (
Apparently the skirt should be not welded to the platform, so it’s my understanding that it can still be anchored using bolts, as for the concrete foundation, maybe with some low-friction pads inserted between the skirt flange and the steel platform. The first questions is, should the bolt holes be slotted radially? If yes, can the vessel be fixed effectively? As far as I know, a fixed support is always needed in saddle design for a horizontal vessel, even if a sliding saddle with slotted holes is present. In the first thread mentioned above, suggested using “a center bolt to locate the vessel”, but I'm not sure what the center bolt is and where it is anchored. Also in that thread, pointed out the problem related to the radially slotted holes. In the second thread, recommended a paper on this point maybe, but the paper link is invalid now.
The second question is about the bolt pretension. I got very little information in the literature on how to determine the required pretension. So what are the potential considerations when we choose the pretension? Maybe it should exceed the axial force which tries to separate the joint during operation? Or it should be large enough to generate a static friction force which is sufficient to prevent the vessel from moving under some lateral load? Of course, the induced stress in the bolt should not exceed the allowable value.
In summary, my question is related to the design of the bolted joint between a short skirt support of a vertical vessel whose expansion is a concern and the steel base of the vessel-skirt structure. Any comments and advice are highly appreciated.
I’m working on the support design of a vertical vessel, as a beginner with little engineering experiences in this field. A short skirt support was finally chosen after some considerations. However, the expansion behavior caused by both the internal pressure and thermal load, the latter in particular, is a big design concern. So my question is how we can minimize the thermal stresses by designing carefully the skirt support, especially the “interface” between the skirt and the base structure which is not a concrete foundation but a steel platform. The skirt would be welded to the lower head of the vessel.
I noticed that similar topics had been discussed in this forum, see e.g. thread794-449461 ( and thread404-224428 (
Apparently the skirt should be not welded to the platform, so it’s my understanding that it can still be anchored using bolts, as for the concrete foundation, maybe with some low-friction pads inserted between the skirt flange and the steel platform. The first questions is, should the bolt holes be slotted radially? If yes, can the vessel be fixed effectively? As far as I know, a fixed support is always needed in saddle design for a horizontal vessel, even if a sliding saddle with slotted holes is present. In the first thread mentioned above, suggested using “a center bolt to locate the vessel”, but I'm not sure what the center bolt is and where it is anchored. Also in that thread, pointed out the problem related to the radially slotted holes. In the second thread, recommended a paper on this point maybe, but the paper link is invalid now.
The second question is about the bolt pretension. I got very little information in the literature on how to determine the required pretension. So what are the potential considerations when we choose the pretension? Maybe it should exceed the axial force which tries to separate the joint during operation? Or it should be large enough to generate a static friction force which is sufficient to prevent the vessel from moving under some lateral load? Of course, the induced stress in the bolt should not exceed the allowable value.
In summary, my question is related to the design of the bolted joint between a short skirt support of a vertical vessel whose expansion is a concern and the steel base of the vessel-skirt structure. Any comments and advice are highly appreciated.