Technician reported aircraft arrived at station APU duct pressure seal clamp not installed at aft bulkhead in wheel well keel beam area. The aircraft was removed from service for repair.

Narrative

Aircraft X arrived with APU duct pressure seal clamp not installed at aft bulkhead in wheel well keel beam. Aircraft goes out of service for a minimum of 4 hours anytime this clamp comes off. For more detailed info about duct design see previous reports.After further investigation it appears in most cases the clamp is being pushed off because of the bad design of the older style duct. Need to change out the older (bad design) duct. As long as the older duct is installed we will continue to have this issue when the clamp is not installed; or missing or comes off; it can lead to pressurization; air conditioning; cab temp control and overheating issues. Overheat sensing element is located directly beside this pressure seal. How will the overheat sensor ever work if cold air from the cabin is constantly being blown onto the sensor. Suggest issuing fleetwide directive to inspect pressure seal clamp and verify duct part number installed. The bad duct manufacturer part X needs [to be] removed from all aircraft and install good duct manufacturer part Y.