What was found
WHILE LEVEL FL240, CABIN ALTITUDE BEGAN TO CLIMB, UNABLE TO MAINTAIN PRESSURIZATION. RT PACK & RT 10TH STAGE PRESS APPEARED NORMAL, NO AIRFLOW FROM VENTS. DECLARED AN EMER, PERFORMED QRH, LEVELED AT 10,000 FT UNPRESSURIZED. INSP ALL DUCTING & PRESS LINES IN AFT EQUIP BAY. FOUND RT DUAL HEAT EXCHANGER DUCT BLOWN OFF & FLANGE DAMAGED. REMOVED DAMAGED HEAT EXCHANGER IAW AMM 21-51-07. REPLACED RT HEAT EXCHANGER & DUCT IAW AMM 21-51-07, WORK ORDER WC 22. OPERATIONS CHECK & LEAK CHECK. SN OFF 200304092 & SN ON 200209170.