Auxiliary Engine Crank Case Explosion

Once an incident happened in my 1st ship sailing in Europe area, it was during my duty time, while me and motorman were taking round on bottom platform suddenly blackout happened. When I went to the auxiliary engine platform, generator area was filled with smoke. Found that generator No 1 had crankcase explosion, piston rod came out from crankcase door and generator platform was full of lubrication oil mist.