Thermal Bowing effect pressure vessel design

[abehong]

I have been working on vessel replacement job for a customer. Experience with the existing vessel ( 96"ID x 120' S/S ) with internal coil bundle has shown that ,during the wash cycle ( wash the internal coil bundle ) the temperature difference between the shell wall at the top and bottom of the reactor leads to the entire shell bowing with a high point in the middle . The middle of the shell rises by approximately 1.75" during the wash. The it bows downward during operating due to the weight of the water in the shall to about 0.75" below its neutral position when the shell is empty. It does not apprear to have any signs of cracks appearing around the saddles of the existing vessel after 20 years in service but a crack occurring on the vessel slid saddle side foundation. Customer expecting to ensure to incorporate thermal effect into design consideration for vessel and its saddle for the new vessel. However, they do not expect to conduct a precise FEA and also could not give more detail process information regarding thermal bowing effect except deflection and about 100 deg c temperature difference between top and bottom section.

I just want to check to see if anyone has experience on similar case before . Also I am wondering if there is any simplified design methods to simulate reflect the impact of thermal bowing effect into saddle design and also stress in the shell where saddle attached to. IS Zick Analysis still applicable for this case or not ?



It will be highly appreciated if anyone could give me a response.