Service Information Document Title: Boom float description
Function Group: position,
Information Type: Service Information
Date: 2014/7/15
Profile: EXC, EC480D L [GB]
Boom float position, description Floating position means that both the piston and piston rod sides of the boom cylinders are connected to the hydraulic tank. The boom can float freely and it is only the weight of the digging equipment and the load that lowers the boom when the control lever is moved forward. The raising of the boom is not affected by the floating position. Floating position results in fuel saving, faster excavating cycle and less wear and vibrations. When the floating position is engaged, the pump flow can be used for purposes other than lowering the boom, e.g. dipper arm and bucket movements. These functions will therefore be faster. The floating position is only active when button has been actuated and the right hand control lever is being held in the forward position. If the attachment is to follow the ground, the right hand control lever must be constantly held in the forward position, while the dipper arm and the attachment are being operated. The boom can then move freely upward or downward depending on the ground conditions. When button switch is actuated and the control lamp for floating position lights up on the instrument control unit I-ECU, a signal is sent to machine control unit V-ECU, which energizes solenoid valve. During the "boom down" movement, the control pressure passes from control valve via solenoid valve and actuates floating valve. The control pressure also passes from control valve and actuates the spools in line-rupture valves. The return oil from the piston sides passes via the line rupture valves in through port B in the floating position valve and out through port A to the piston rod sides of the cylinders. The surplus oil from the piston sides passes via port T in the floating position valve and then through the pressure back-up valves of the main valve block to the hydraulic tank.