Hydraulic system

A hydraulic system comprising:

• a main hydraulic pump discharging a hydraulic fluid;
• a plurality of driving apparatuses operating by receiving a hydraulic fluid;
• a parallel flow path through which the hydraulic fluid discharged by the main hydraulic pump moves;
• a plurality of control spools connected in parallel to the parallel flow path, respectively, and controlling supply of a hydraulic fluid to the plurality of driving apparatuses;
• a plurality of electronic proportional pressure reducing valves adjusting a pilot pressure that is applied to an end of each of the plurality of control spools in proportion to an input current signal;
• a bypass valve connected in parallel to the parallel flow path;
• and
• an additional valve block accommodating the plurality of control spools and detachably coupled to a main control valve housing in which the parallel flow path is formed,
• wherein when the plurality of control spools are not operated, the hydraulic fluid discharged by the main hydraulic pump is drained into an oil tank through the parallel flow path without passing through the plurality of control spools, and
• wherein the additional valve block has:
• an additional parallel flow path connected with the parallel flow path;
• one or more additional control spools each connected in parallel to the additional parallel flow path;
• and
• a plurality of additional electronic proportional pressure reducing valves adjusting a pilot pressure that is applied to an end of each of the one or more additional control spools in proportion to an input current signal.