Yes, originally the expansion valve insulation was a dry foam. The standard field insulation is Presstite tape. It is important to insulate it.

The mercury tube on many expansion valves clamp to the low side line with insulation, but the mercury tube on these H Block expansion valves is self contained and makes contact with the block.

I guess there may be some aftermarket units with longer mercury tubes that can or should be fixed in place.

Good luck,