MD80 SUPER 80 HAD TO RETURN LAND DFW BECAUSE A DOOR IMPROPERLY SEALED MADE IT IMPOSSIBLE TO PRESSURIZE THE ACFT.

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DEPARTING DFW FOR PDX NOTICED PRESSURE FLUCTUATIONS; ADJUSTED RATE KNOB AND CHKED CTL LEVER IN AUTOFLT. WAS CLRED TO 14000 FT; CLBING THROUGH 10000 FT I REALIZED PRESSURE CTLR HAD TRANSFERRED TO STANDBY AND FLOW LIGHT ILLUMINATED. CABIN ALT WAS 7000 FT AND CLBING; OUTFLOW VALVE WAS FULL CLOSED. I INSTRUCTED FO; PF; TO LEVEL OFF BELOW 14000 FT AND REQUESTED LOWER ALT FOR PRESSURE PROBS. ATC CLRED US TO 10000 FT. CABIN ALT WARNING ILLUMINATED AS CABIN CLBED SLOWLY THROUGH 10000 FT; HOWEVER; AUTO MASK DEPLOYMENT WAS AVERTED. #4 FLT ATTENDANT CALLED FROM AFT CABIN. AFT GALLEY DOOR SEAL APPEARED PARTLY OUT/TWISTED; BUT DOOR HANDLE APPEARED LOCKED. AIR NOISE FROM DOOR WAS SO LOUD THAT COM WAS ALMOST IMPOSSIBLE. PRESSURE COULD NOT BE RESTORED BY OM PROC. I REQUESTED VECTORS BACK TO DFW FOR A PRECAUTIONARY LNDG AT A NORMAL LDNG WT OF 127000 LBS. MAINT MET ACFT AT GATE; RECYCLED DOOR; RESET SEAL. PRESSURE SYS CHKED NORMAL AND ACFT WAS REDISPATCHED WITH SAME CREW TO PDX. NEXT FLT UNEVENTFUL. DO NOT BELIEVE ANY FAR VIOLATIONS OCCURRED.