You did not tell us the size of the tank, the size of the nozzle/pipe, the amount of the expected settlement or the time frame of the alleged settlement so it is a bit hard to offer real help.
However before I retired I had more than 45 years in the process plant engineering, design, field engineering and pipe fabrication. During that time I never saw or installed a tank connection with an expansion joint.
I would love to be able to show you how to do it with nothing but simple pipe configuration.
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Jop