3. DRAIN CIRCUIT Travel motor Swing motor Turning joint Main pump From return line dr2 ~ dr8 Hydraulic oil tank Spin filter dr1 Check valve 1.5kgf/cm 2 21073CI02 Besides internal leaks from the motors and main pump, the oil for lubrication circulates. These oil have to be fed to the hydraulic tank passing through spin filter. When the drain oil pressure exceed 1.5 kgf/cm 2 (21 psi ), the oil returns to the hydraulic tank directly. 1) TRAVEL MOTOR DRAIN CIRCUIT Oil leaked from the right and left travel motors comes out of the drain ports provided in the respective motor casing and join with each other.
These oils pass through the turning joint and return to the hydraulic tank after being filtered by spin filter. 2) SWING MOTOR DRAIN CIRCUIT Oil leaked from the swing motor returns to the hydraulic tank passing through a spin filter with oil drained from the travel circuit . 3) MAIN PUMP DRAIN CIRCUIT Oil leaked from main pump returns to the hydraulic tank passing through spin filter. 3-4