How should the pressure generated by the insulation materials of LNG storage tanks be considered?

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The pressure on the inner tank due to the insulation layer consists of the static pressure exerted by the insulating material and the additional pressure applied when the inner tank expands. But I still don’t understand the principles and values behind these two pressures; could someone please help explain them? Thank you. 1. How is the static pressure generated by expanded perlite calculated? Is the value calculated using the formula for static liquid pressure too high? 2. How is the pressure generated by elastic felt calculated? When installing the elastic felt, it needs to be compressed to a certain thickness, at which point an initial pressure P1 is generated ； After liquid is introduced, the storage tank contracts, and the elastic felt compensates for this; as a result, P1 gradually decreases. Even if the tank is taken out of use in the future and the inner tank expands back to its original diameter, the pressure restored by the elastic felt will still be close to P1, right? So should the additional pressure from the insulation layer be taken as P1? It’s just my personal understanding; I’m not sure if it’s correct. Please advise, experts.