Experts say the nation’s more than 10,000 grain elevators are safer than ever, despite a weekend explosion that killed six people in Kansas. Fine, highly combustible dust flows through grain elevator buildings as the grain is moved, and a spark from equipment or an overheated bearing can ignite it. The nation saw an average of 25 grain elevator explosions a year in the late 1970s. That dropped to fewer than nine explosions per year between 2001 and 2005. Experts say a key to reducing explosions has been simple rules, such as banning welding when grain is being moved, and keeping machines well-oiled to make sure they don’t overheat. The last grain elevator explosion in the local area was in October of 2005 in Vernon Center. Six people were injured in that blast.