What was found
AFTER TAKEOFF, THE AIRCRAFT FAILED TO PRESSURIZE. THE CAPTAIN RETURNED TO DEPARTURE WITHOUT INCIDENT. SUBSEQUENT INSPECTION FOUND THAT THE EDC DISCHARGE DUCT HAD BECOME DISCONNECTED FROM THE EDC ALLOWING THE PRESSURIZATION AIR TO OVERBOARD. CORRECTIVE ACTION WAS TO REINSTALL THE DISCHARGE DUCT AND REPLACE THE CLAMP. THE AIRCRAFT WAS PRESSURIZED ON THE GROUND TO 3 PSI DIFFERENTIAL AND ALL SYSTEMS CHECKED NORMAL. (K)