PURPOSE: To safely use a combustible cleaning solution by providing an inert gas supply means supplying inert gas to a cleaning tank on the basis of the concn. of oxygen in the cleaning tank and holding the concn. of oxygen to the lower explosion limit or less in the presence of the combustible cleaning solution.
CONSTITUTION: An inert gas supply means 11 consists of an oxygen densitometer 12 detecting the concn. of oxygen in a cleaning tank 2, a gas supply part 13 sending inert gas into the cleaning tank 2 and a partition chamber 3, and a control part 14 controlling the operation (the supply amount of the inert gas) of the gas supply part 13 on the basis of the detected value of the oxygen densitometer 12. When the oxygen concn. value from the oxygen densitometer 12 becomes higher than a predetermined concn. value, the inert gas is sent into the cleaning tank 2 and the partition chamber 3 from the gas supply part 13 so that the concn. of oxygen in the cleaning tank 2 does not reach a lower explosion limit or more, in the presence of a combustible cleaning solution. By this method, the combustible cleaning solution 4 can safely be used.
SAKURAI HIROSHI
YOSHIDA KENICHI
TAI SHOJI
