Locate one of the double master links prior to locking out the Spiral. This is done by setting the Spiral on manual mode and jogging it until you see the two slats/carrier plates with the yellow dot. Sometimes the dot has worn out, so you must look for either one dot and indentation or two indentation in the center
Once the two slats have been found (if possible), slowly jog the spiral so the slats end up in the back where the service window is. If not use hand crank to move into place.
Turn off the Spiral and Lock it out.
Using the lift, go up to the drive motor and remove the fan cover to gain access to the brake. It is possible to release the brake through the access hole in the cover. Using the 3mm Allen, screw in the set screw to release the brake. You can check by spinning the fan by hand.
Using the 4mm Allen, remove the cover for the chain oil maintenance window. Using the 8mm Allen, turn one of the bolts on either end to open up the slat track to be able to remove the slats.
Using 4mm Allen, open the rear service window.
Remove 5-6 slats to gain access to the chain. Hand crank would be needed to manually move the spiral to place slats in the right location to be removed.
Using the flathead and needle nose pliers undo and remove both master links.
Brink chain together, use of chain connection tool might be needed if not enough slack on chain. Add one of the master links back to close the chain.
Place back the slats, it is possible that one or a couple will break in the process as they need to be bent and pushed in. Use the extra slats as needed. Close service window afterwards.
Using the 8mm Allen close the track once again making sure it is just snugged, if tighten to much it will come loose and would have the tighten the other way again. Put maintenance cover back afterwards.
Going back up on the lift, engage the brake once again by loosening the set screw. Make sure to check by spinning the fan, you should not be able to spin the fan by hand once the brake is engaged. Place fan cover back on afterwards.
Remove lock out tag out, and turn spiral back on.
Source: GXO - H&M (Community Member)