Base plate for vertical vessel
Base plate for vertical vessel
(OP)
For vertical vessels with skirts, the bottom base plate is
single for short vessels say 1m or 2m in height. however for tall vessels 2 ring plates with gussets are used.
Any suggestions on the significance and guidance on when 2 ring plates are required ?
thanks and regards
single for short vessels say 1m or 2m in height. however for tall vessels 2 ring plates with gussets are used.
Any suggestions on the significance and guidance on when 2 ring plates are required ?
thanks and regards





RE: Base plate for vertical vessel
Vessels that have especially large bending moments acting on them may require so many anchor bolts, consequently spaced close together, that the anchor bolt chairs may begin to run into each other. Or, there may be just so many anchor bolt chairs that the number of small pieces to assemble is a nuisance. In either case, placing a continuous ring as the top component of the anchor bolt chair relieves the problem.
RE: Base plate for vertical vessel
This is just my $0.02
Good luck.
RE: Base plate for vertical vessel
I don't understand your meaning of vessel height of 1 or 2 meters. Wow, these are short vessels.
The quick run down is you chose the top compression plate type when you have so many anchor chairs such that it would be simply easier to use a single compression ring instead of welding individual compression "plate", which cost a lot of money and time. Also compression plate is slected to help to reduce the local bending stresses in the skirt caused by the anchor chairs. This type is usually selected when you have a column taller than say > 80 ft tall and slender (read large H/D ratio > 10).
Suggest you read the excellent books such as the ones from Bednar, Brownell & young, etc. They will answer your question in detail via calculations and show you how to derive the equations.
Hope this helped.
RE: Base plate for vertical vessel
RE: Base plate for vertical vessel
Funny you mention this as an example. I just had a discussion with our Structural Eng. yesterday on setting rules for our standard on pipe support design. He mentioned on a project he was on, the "T" post type pipe support standard was shown with gussets to reinforce the horizontal support bar against the bending moment. Of course, in a large refinery project, there's many "T" posts. The Fabricator wants to charge double the cost to put in the gussets because it cost them time and manpower just to cut and weld on all those gussets. The vedor suggested to either pay for the gusset design or pay for a beam with thicker flange which has no cost increase on fab cost. The choice is obvious. Many Engineer and Designers in EPC and Owner side don't have shop experience and do not take fab cost into consideration when they design. I have to admit I'm guilty of this sometime. Relating this back to the subject of this post, it is cheaper to use a compression ring when you have 8 or more anchor chairs.
RE: Base plate for vertical vessel
One reason you often see larger vessels have a top ring instead of chairs is that when you are erecting a vertical vessel from the horizontal position to the vertical, the rigging at the bottom is usually attached to the baseplate. In some cases - frequently for larger vessels - this step will govern the design of the baseplate. When you add a continuous top ring you get substantially more section modulus from the baseplate/(part of the) skirt / top ring acting together.
jt
RE: Base plate for vertical vessel
The single base plate I'm talking about
1.5m dia vessel and 2m in height with skirt height of 0.8m
The number of bolts 4. There are no gussets. The 1/2" thk skirt and the baseplate 15mm are checked and found ok for the vertical/lateral loads.
There is another enquiry for a vessel 5m t/t with 1m skirt...which raised the question if the vessel baseplate and bolts can be designed for the same configuration.
Technically the skirt can be checked for the buckling and the chairs would not change the design of the skirt plate (except for the small change in the height)
not sure about the impact on baseplate design
RE: Base plate for vertical vessel
RE: Base plate for vertical vessel
A discussion of vertical tank/vessel supports, anchor bolts, loading definition etc is contained in:
"Pressure Vessel Design Handbook, Henry H. Bednar
"Pressure Vessel Handbook", 13th Edition: Eugene F. Megyesy
and other places...
Imposition of significant seismic and/or wind loadings affects the selection of anchorage and anchor bolt rings.
My opinion only..
-MJC