... Operation:Open inlet valve1, outlet valve 5, 6, 7 →close backblow valve 2, 3, 4, return valve 8→open inlet pump→ normal ... filter→ close inlet pump, inlet valve1 →open return valve8→close return valve after finish8→open air valve2Blow directly→ close direct-blow ... valve after finish2→open outlet valve6→backblow and ...