What was found
NR 1 PACK FLOW DISAGREE IN CRUISE. LOUD NOISE FROM PACK, CYCLED CONTROLLERS WITH NO HELP. SELECTED AIR SYS MANUALLY OFF/ON SEVERAL TRIES, NO HELP. RAN QRH CHECKLIST, NO HELP. TURNED PACK ONE OFF. RETURN TO DEPARTURE. NO FAULT FOUND IN CFDS. TROUBLESHOT IAW FIM 21-50-13, NO FAULT FOUND, NO HISTORY FOR LAST FLIGHT FOUND. ON AIRCON CONTROLLER NR1, FAULT HISTORY FOUND, FAILED INTERMITENT SEVERAL LEGS, R & R AIR CON CONTROLLER NR 1 IAW MM 21-62-01-4. TEST PASSED. OPENED NR 1 PACK COMPARTMENT FOR VISUAL INSPECTION, FOUND HOSE ON TURBINE BYPASS DUCT DISCONNECTED AND HEAT PROTECTION BLOW OUT. NO DAMAGE TO THE DUCT FOUND. ONE CLAMP HOLDING HOSE WAS OUT. REPAIRED DAMAGE AND AND REPLACE BYPASS DUCT.