Lifting issues for mixing tanks
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A mixing tank with a diameter of 4000×6000, classified as Category 2 container; the shells and heads are made of 304 steel, while the components used for sealing are made of 345 steel. The total weight, not including the mixing shaft, is around 30 tons. Originally, I provided lifting lugs on one of the side walls. Now the client is asking whether it’s possible to install a cover on the flange at the mixing port, with lifting lugs welded to that cover; after lifting, the cover could be removed and the mixing shaft installed on site. Is this feasible? If so, how should the lugs be designed? If not, how can I convince the client?
For such heavy equipment, if it is to be lifted using the mixing port flange, it is necessary to carry out calculations of the local stresses on the flange and the pipe connection; local reinforcement might be required. It would be better to try to persuade the owner not to proceed with this approach.
Based on the diagram, your device is not heavy.
I’m just too lazy to do these calculations; going with the standard option is simpler, and what’s important is having a convincing reason for it
** May I ask which book this is from?
This type of structure, which uses holes at the top as lifting points for connection, is generally used for hydrogenation equipment; due to the special material of such equipment, welding lifting lugs onto it is not appropriate, so this is a last resort. It is completely unnecessary for equipment such as mixers; moreover, aspects such as the perpendicularity of the flange surface at the mixing port and the center position of the opening all have specific requirements. If not handled properly, deformation may occur due to lifting forces, which can affect the installation and use of the mixing equipment, resulting in losses that outweigh any benefits.
My initial plan is to reject the owner’s request on these grounds: what should be done if the flange of such equipment becomes deformed during lifting? Moreover, our experienced workers also say that the flange wasn’t meant to be used as a lifting point, and it has other functions as well.