3. DRAIN CIRCUIT Travel motor Swing motor From return line Main pump Turning joint Dr#, dr# Hydraulic oil tank Drain filter Check valve 1.5 kgf/cm 2 220NL3CI02 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 drain 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 drain filter. 2) SWING MOTOR DRAIN CIRCUIT Oil leaked from the swing motor returns to the hydraulic tank passing through drain filter. 3) MAIN PUMP DRAIN CIRCUIT Oil leaked from main pump returns to the hydraulic tank passing through drain filter. 3-5