A B757-200 FLIGHT CREW; WORKING WITH MEL FUEL SYSTEM LIMITATIONS; MISMANAGED THE FUEL SYSTEM; RESULTING IN A FUEL IMBALANCE BETWEEN MAIN TANKS.

Narrative

I SCREWED UP; BUT FOR THE BEST INTENTIONS. I ARRIVED AT MY DEPARTING ACFT TO FIND THAT IT WAS OPERATING UNDER AN MEL PLACARD REQUIRING A COMPLICATED INSPECTION OF THE FUEL SHUTOFF VALVES AFTER EVERY REFUELING OF THE CENTER FUEL TANKS. THIS HAD NOT BEEN DONE; AND AFTER CONSULTING WITH MAINT; I CALLED FOR A MECH. THE INSPECTION AND SIGNOFF RESULTED IN A 13 MIN DEP DELAY. I BRIEFED THE FO ENRTE THAT WE WERE GOING TO MAKE SURE THAT WE LANDED WITH AT LEAST 1000 LBS IN THE CENTER TANK (AD REQUIREMENT) SO WE COULD AVOID THE REFUELING AND THE ACCOMPANYING INSPECTION. I WAS THINKING THAT DESTINATION HAS CONTRACT MAINT AND WE WOULD PROBABLY END UP WITH A DELAY. I/WE THEN BECAME FIXATED WITH MONITORING/MANIPULATING THE CENTER FUEL QUANTITY TO GET OUR 1000 LBS. IN DOING SO; WE FAILED TO NOTICE AN INCREASING FUEL IMBAL BETWEEN THE MAINS. WHEN WE NOTICED IT; WE WERE OUT OF LIMITS. WE SPENT THE BALANCE FO THE FLT WORKING TO GET THE FUEL SYS BACK TO NORMAL. WE DID END UP WRITING THE AIRPLANE UP FOR AN UNCOMMANDED FUEL TRANSFER FROM; WE SUSPECT; THE RIGHT MAIN TO THE CENTER. WE DID CONSULT WITH MAINT. IN OUR ATTEMPT TO KEEP THE CENTER TANK ABOVE 1000 LBS; WE PROBABLY HID THE MALFUNCTION. NEITHER WEATHER NOR ATC ISSUES WERE EVER A FACTOR. EVERYTHING ELSE WAS NORMAL. NEXT TIME; I LET THE COST OF CONTRACT MAINT AND ANY DELAY ISSUES TAKE CARE OF THEMSELVES. I WILL TAKE CARE OF MY AIRPLANE/CREW.