FLT CREW OF A320 MISINTERPRET MEL AND WT AND BAL COMPUTATIONS AND DEPART WITH ZERO FUEL WT IN EXCESS OF STRUCTURAL MAX.

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UPON ARRIVING AT THE ACFT WE ROUND THAT THE R CTR TANK FUEL PUMP HAD BEEN DEFERRED INOP. CAPT DEALT WITH MAINT CTL AND DISPATCH ON THE PHONE IN OPS WHILE I DID THE WALKAROUND AND COCKPIT SET UP. CAPT ARRIVED AND INFORMED ME THAT WE WOULD BE LOADING LESS FUEL; BUT WOULD STILL ARRIVE AT DEST WITH APPROX 7000 LBS. JUST PRIOR TO PUSHBACK; AS WE WERE READING THE INITIAL CHKLIST; WE NOTICED ABOUT 6000 MORE LBS OF FUEL WAS ADDED THAN NEEDED. THE PLANNED TKOF DATA MESSAGE STATED THAT 6700 LBS OF STRUCTURAL CHK FUEL WAS ON BOARD. WE READ THE MEL CARD FOR THE INOP PUMP AND DETERMINED THAT THE 6700 LBS OF STRUCTURAL CHK FUEL SHOULD BE ADDED INTO ZFW WHICH GAVE US A ZFW OF 134200 LBS; WITHIN LIMITS. WE CONTINUED AND AFTER TKOF THE CAPT SENT AN ACARS TO DISPATCH WONDERING WHY MORE FUEL WAS ADDED AND WE WOULD ACTUALLY LAND AT DEST WITH 14000 LBS RATHER THAN THE 7000 LBS. DISPATCH EXPLAINED THAT LOAD PLANNING HAD MADE AN ERROR AND ADDED AN ADDITIONAL 7000 LBS OF FUEL. WE HAD NOTICED THAT BUT THOUGHT THAT WAS CONSIDERING STRUCTURAL CHK FUEL AND NECESSARY FOR WT AND BAL. DISPATCH THEN NOTIFIED US THAT DUE TO THE MEL LIMITATION OF ADDING ALL CTR TANK FUEL TO THE ZFW WE EXCEEDED ZFW LIMITATIONS BY 4000 LBS. THIS ONLY WOULD HAVE BEEN A PROB HAD THE OTHER CTR TANK PUMP FAILED EARLY IN THE FLT. CONTRIBUTING FACTORS: LOAD PLANNING MISTAKE; FAILURE OF DISPATCH TO RECOGNIZE MISTAKE; FAILURE OF PLTS TO RECOGNIZE MISTAKE. UNFAMILIARITY WITH MEL; WHICH STATES ALL CTR TANK FUEL WILL BE ADDED TO ZFW. BEING RUSHED TO DEPART ON TIME. CONFUSION ON MEL CARD THAT STATED 'CTR TANK FUEL IS TO BE CONSIDERED STRUCTURAL CHK FUEL WHEN IN FACT ONLY PART OF THE CTR TANK FUEL WAS STRUCTURAL CHK FUEL; AND 'CTR TANK FUEL IS STRUCTURAL CHK FUEL AND IS INCLUDED IN ZFW' IMPLYING THAT IT MAY ALREADY BE INCLUDED IN THE ZFW LINE OF THE PLANNED DATA TKOF MESSAGE. WE DID THE MATH AND FIGURED IT WASN'T; BUT THAT WAS JUST ONE MORE AREA OF CONFUSION WE CAME UPON. LESSONS LEARNED: READ MEL VERY CAREFULLY AND DON'T ASSUME LOAD PLANNING AND DISPATCH AREA ALWAYS CORRECT. IF IT DOESN'T MAKE SENSE; QUERY WHY RATHER THAN MAKE IT MAKE SENSE BY TRYING TO JUSTIFY THE OTHER INFO GIVEN TO YOU.