API 620 Table Q Material exemption process

[Krystal H-P]

I am currently working on a design for an insulation deck to be installed inside an LNG tank. The deck design consists of bolted connections not welded and therefore it is not necessary to adhere to the Material requirements in Table Q of the code which are tempered for welding. Are there any suggestions on how to go about submitting a material exemption for approval with the FERC inspectors or the certifying inspectors? The tank is being built in the US. I'm not sure if all that is required from an inspection process to obtain the API 620 certification is a FERC approval. Does anyone have any experience with obtaining material exemption approvals when it comes to API 620 tanks?

Thank you!