Boom raise position (2) B2 A2 b2 a2 P T LS Pst T Hydraulic circuit 75796WE52 When the pilot pressure is led to the port b2, the boom spool moved to raise position. Oil from the pump flows to the cylinder port B2 through the load holding valve and oil from the cylinder flows into the tank passage through the cylinder port A2. ц Load holding valve When the load pressure is higher than the pump pressure, the load holding valve shuts off the passage between the high pressure feed passage and the center bypass passage and prevents the reverse flow from the cylinder. 6-28 a1 P a2 A1B1 A2 B2 Floating Down Bucket Load holding Up valve Dump Roll back Floating own Boom Up D b1 b2