A conveyor having conveyor chain 100 adapted to be engaged and driven by drums 180 and 190 having spiral flights. The conveyor chain has a number of interconnected conveying modules 120, 140, 150 and 160. Selected modules 120 are aligned in the direction of travel parallel to the axis of rotation of the drums. Each of the aligned modules has a traveling guide socket 122 on the back surface, which engages with flight portions 180a and 190a of the spiral drums, so that the chain is advanced by the rotation of the drums. The modules are rectangular and are interconnected in columns and rows, preferably in a brick pattern.