A330 Captain experiences Green Hydraulic System failure as the gear is retracted after takeoff. The gear remains extended with the gear doors open; an emergency is declared and the flight returns to departure airport for an overweight landing. The G Hydraulic system had failed on the in bound flight and was repaired prior to this flight.

Narrative

We departed after a lengthly maintenance delay to repair HYD G system. On initial climb; when we raised the landing gear we totally lost pressure in the HYD G system. The gear remained extended with the gear doors now open. We performed the ECAM actions that we could and began procedures to return. We contacted Dispatch via SATCOM and asked if they wanted us to do an overweight landing. They replied; YES. We declared an emergency with ATC and asked to have emergency equipment standing by for our overweight landing and that we would not be able to clear the runway after landing due loss of NWS. We performed QRH overweight landing checklist; then landed uneventfully. Touchdown rate of descent was <300 FPM. With accumulator pressure we were able to clear the runway onto a very large paved area that we could have evacuated the aircraft from. Max brake temperature was 580. We were inspected by airport emergency personnel who found no brake fire or anything else amiss. After releasing those emergency personnel we were towed to parking and deplaned normally.We were told by maintenance personnel that the most likely cause for the loss of pressure was air trapped in the system. Perhaps a change to maintenance procedures as HYD G system fluid was nearly depleted on the previous flight.