PURPOSE: To certainly stop stationarily mounted type diesel engines fallen into over-running condition.

CONSTITUTION: A over rotation preventing device 4 is provided for preventing over-run by stopping feed of fuel into diesel engines when rotational speeds of stationarily mounted type diesel engines 1a to 1c exceed a speed set for preventing over rotation. An emergency stopping device 5 is provided to supply non-combustible gas into the combustion chamber of an engine when rotational speed of the engine exceeds the speed set for emergency stopping higher than the speed set for preventing over-rotation. When the rotational speed of the engine exceeds the speed set for emergency stopping, an emergency stopping signal is generated by an emergency stopping signal generating means 6. When any emergency stopping signal is generated, valves 17a, 17b and control valves 14a to 14c corresponding to a stopping engine are opened by a control valve driving means 11, and non-combustible gas is supplied from non-combustible gas reserving tanks 16a, 16b into an intake pipe for supplying air into the combustion chamber of the engine.