Filtration and circulation system

Abstract

This invention provides a filtration and circulation system and a drain tank that do not easily obstruct the flow of fluid used for backwashing. The filtration and circulation system of this invention filters and circulates contaminated fluid containing solid foreign matter due to its use in metalworking machinery. It comprises: a filtration device for filtering the contaminated fluid; a drain tank 3 for containing the fluid discharged during backwashing of the filtration device; and a backwash liquid outlet pipe L5 connected to the bottom surface of the drain tank 3, allowing the fluid inside the drain tank 3 to flow out. An outlet 33a is formed on the bottom plate 32 of the drain tank 3, connecting the internal space of the drain tank 3 to the backwash liquid outlet pipe L5; the opening area of ​​the outlet 33a is smaller than the cross-sectional area of ​​the backwash liquid outlet pipe L5.

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