SYSTEM / Hydraulic System Combined Operation Circuit Swing and Boom Raise Operation 1. When the boom is raised while swinging, pilot pressure shifts the swing, boom 1 and boom 2 spools. 2. Pressure oil from pump 1 flows into the boom cyl- inders through the parallel circuit and the boom 1 spool, and raises the boom. 3. Pressure oil from pump 2 flows into the swing motor through the swing spool. 4. At the same time, pressure oil from pump 2 flows through the parallel circuit and flows into the boom cylinders is combined with pressure oil from pump 1, and raises the boom. T2-4-18