Return to Master Table of Contents OPERATION OF WORKING COMPONENTS BOOM OPERATING CIRCUIT The boom operating circuit includes the right and left main hydraulic pumps (both halves of the main pump assembly), both sides of the control valve and the boom cylinder. The circuit operates in boom down mode through the first shift position and through the second shift position in boom up mode. Overload relief valves set at 360 kg/cm . (5,112 psi) protect the hydraulic system from damage as a result of overloads or shocks to the boom.
Additional protection - to prevent cavitation of the cylinder - is provided by a make-up valve and reservoir return circuit, which ensures that the volume of oil going to the cylinder will not exceed the volume of oil coming out. 2 BOOM UP CIRCUIT When you pull the boom control lever backward, the right side pilot valve generates secondary boom up pilot pressure that is transmitted to the BOOM1 and BOOM2 spools of the control valve simultaneously. When secondary pilot pressure reaches 7 - 10 kg/cm BOOM CYLINDER 2 (100 - 142 psi), boom spools open and oil from both pumps goes to the boom cylinder.
PUMP(L) PUMP(R) ATS0750L Figure 2 BOOM DOWN CIRCUIT When the boom control lever is pushed forward, the right side pilot valve generates secondary boom down pilot pressure that is transmitted only to BOOM1 spool of the valve. When secondary pilot pressure reaches 7 - 10 kg/cm BOOM CYLINDER (100 - 142 psi), the BOOM1 spool opens so that oil from only one pump (PUMP(L)) assembly goes to the boom cylinder for boom lowering. 2 PUMP(L) PUMP(R) ATS0760L Figure 3 Page 6 Hydraulic System Troubleshooting, Testing and Adjustment BOOM1 BOOM UP PILOT BOOM2 M DOWN ILOT BOOM1 BOOM2