I haven't done a lot of offshore work lately, so I am not sure about if any new insulations have been developed, but in the past it was usual to enclose thermal insulation in an annular space between an inside pipe product-carrying "core" and an outside pipe "casing", due to waterlogging of the thermal insulation if exposed to water under deep water pressues, which renders it almost totally ineffective.
Honestly, I've never heard about this in offshore Brazil. In my opinion, the concrete coating acts as a insulation for the pipeline. So, you might wanna go back to the insulation calculation and review it.
In addition, I don't think the strength of the insulation is capable of holding the concrete coating in place during the installation of the pipeline.
Thanks for your reply.
when you need to reach high value of thermal insulation (below 4W/m2K), the concrete cannot be used as insulation so you would need to add a proper layer.
After the post of SJones I got in contact with that Company and they states that is possible to do that without major issue (in terms of applicable thicknesses).