AT least seven workers were injured and damage expected to run into millions of rands incurred, after a massive explosion rocked South Africa's second-largest crude oil refinery in Durban today. Emergency personnel rushed to the scene and workers at the refinery were ordered off the premises as firefighters battled to control the blaze. Residents in the suburbs near the refinery said they heard loud explosions and saw flames and smoke. A Reuters photographer saw several fire engines spraying foam onto the affected part of the refinery, which is operated by African energy company Engen. Ambulances, metropolitan police and national police…