Hi Charles,

You are right as far as you go.

The loop should be designed to rise vertically up from the rack elevation for some design specific distance and then go back horizontal and perpendicular to the rack piping (the loop continues symmetrically back to the rack). There will have to be a rack "bent" (structure) positioned under the offset to support the leg of the loop that is parallel to the main rack piping. By rising up vertically from the rack elevation the loop gains more flexibility and it allows other rack piping to pass beneath it.

There should also be guides located near the beginning and the end of the loop. When you "nest" several loops together the hottest and largest diameter pipes should be on the outside with the coolest (less hot) and smaller diameter systems "nested" within. Spacing on the rack must accommodate the outside diameter of adjacent systems' flanges (and insulation). On the rack, the expansion/contraction movements perpendicular to the pipe centerline must be controlled to preclude interferences (typically these systems employ rigid guided sliding supports).

The Piping Guide (Syentek) has absolutely the best guidance that I have ever seen in one place for designing rack piping. Go here:

http://www.pipingguide.com/

I am leaving much unsaid for others to address here.

Regards, John.