LOSS OF CABIN PRESSURE.

Narrative

IN CRUISE; AT FL270; THE FE ANNOUNCED THAT HE COULD NOT KEEP THE CABIN FROM CLBING. JUST PREVIOUS TO THIS; THE FE WAS WORKING ON WHAT WE THOUGHT TO BE A PACK PROB. A LOUD POP WAS THEN HEARD AND THE FE TRIED TO KEEP THE CABIN FROM CLBING. AFTER ANNOUNCING THAT THE CABIN WAS CLBING UNCTLABLY; HE SAID TAKE US DOWN. THE CAPT HAD ALREADY ASKED FOR LOWER AND WE WERE GIVEN A DSCNT TO FL240. WHILE DSNDING TO FL240 THE CAPT DECLARED AN EMER AND SET THE XPONDER TO 7700. THE EMER DSCNT CHKLIST WAS COMPLETED. THE REMAINDER OF THE FLT WAS FLOWN AT 10000 FT. AT 10000 FT THE PRESSURIZATION SYS MAINTAINED CABIN PRESSURE ON SCHEDULE. SUPPLEMENTAL INFO FROM ACN 290091: I NOTICED THE CABIN PRESSURE WAS STILL CLBING AT 200-300 FPM. WHILE TROUBLE-SHOOTING THE PROB; WE HEARD A LOUD 'BANG' AND THE CABIN CLBED UNCTLABLY AT 1500-1800 FPM. I ADVISED THE CAPT THAT THE CABIN WAS UNCTLABLE AND THAT WE NEEDED TO DSND IMMEDIATELY. THE CAPT GOT A DSCNT TO 240 AND HE DECLARED AN EMER; SQUAWKED 7700; RECEIVED A CLRNC TO DSND TO 10000 FT. THE CABIN PRESSURE NEVER EXCEEDED 6000 FT AND WAS CTLABLE AT 10000 FT AND LANDED ABOUT 20 MIN LATE.