| 摘要 |
PROBLEM TO BE SOLVED: To provide a cleaning method for working liquid by which a cleaning performance of the working liquid is greatly enhanced, enabling repeated uses of the working liquid for a long period, and also a running cost and a waste liquid treating cost, etc., are reduced. SOLUTION: This cleaning method for the working liquid comprises a first cleaning process for removing impurities mixed in the working liquid flowing in a circulation path, and a second cleaning process for further more cleaning the working liquid. In the second cleaning process, the working liquid cleaned by the first cleaning process is diffused and flowed out to the lower part of a second storage tank 40 through a working liquid introduction cylinder 42a, and the working liquid diffused and flowed out to the lower part in the second storage tank 40 is filtered from the lower side to the upper side with a filter 44, and the working liquid filtered with the filter 44 is subjected to oil-liquid separation with an oil-liquid separation wall 46, and the resulting working liquid is collected with a liquid collection groove 47 arranged at the outer periphery of a weir 45.
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