Installation & Verification Guidelines Verify the Hitachi part number and confirm main control valve assembly compatibility, including boom, arm, bucket, travel, and swing spools, as well as relief valves and holding valves. New or remanufactured valves must include hydraulic bench test reports covering pressure, flow, and internal leakage for each section. For remanufactured valves, confirm whether spools are honed, repaired, or new. Replace all O-rings. Inspect the valve