What is the correct method to install a feed-thru thru a wall?
I am envisioning a 6" square box with a cover, on each side of the wall and 2 short pieces of 2" EMT connecting the two boxes.
The feed-thru would be used to run temporary power, communication cables, liquid lines, etc. Obviously the covers would be installed when the pass-thru is not in use. One side of this feed-thru is in a conditioned space and the other side is the building's loading dock.
This is primarily a design issue, but a good one for discussion.
For a fire rated wall, the key is to restore / maintain the fire resistance of the wall. Even for a 'normal' wall, the idea is to keep noise, drafts, etc., from passing through.
The method you propose isn't bad ... though I would use 'running thread,' rather than trying to get nipples to to be the right size. I'm a bit puzzled as to why you would want two nipples though ... keep in mind that all conductors of a circuit need to be run in the same nipple, and that you need a partition between low voltage and power cables.
Easier to do, perhaps, is to install one of the commercially available fire-stop products. These are nicely made tubes, flanges on either side .... and large enough to pass your pipes through. You seal the remaining gaps with the appropriate products, and all is well.
How to make the necessary holes in the wall? A roto-hammer, with the appropriate core drill, makes easy work of the chore.