Boom Raise
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| Illustration 1 | g02162836 |
Boom drift reduction / regeneration valve (BOOM RAISE) (1) Boom drift reduction / regeneration valve (2) Passage (3) Passage (4) Check valve (5) Spool (6) Passage (7) Manual lowering valve (8) Line relief valve (9) Passage (10) Spring (11) Spool (12) Solenoid valve (13) Passage (14) Spring chamber (15) Spring (16) Passage (17) Line (18) Passage (oil flow to rod end of boom cylinders) (19) Passage (oil flow to head end of boom cylinders) | |
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| Illustration 2 | g02162994 |
Main control valve (1) Boom drift reduction valve (7) Manual lowering valve (8) Line relief valve (12) Solenoid valve (18) Passage (oil flow to rod end of boom cylinders) (19) Passage (oil flow to head end of boom cylinders) | |
During a boom raise operation, oil enters boom drift reduction / regeneration valve (1). Oil flows from the boom control valve to passage (2). The oil pushes against spool (5). Spool (5) shifts downward against spring (15). Oil then flows to passage (6) and into passage (13). Oil then flows to passage (19) and to the head end of the boom cylinders.
The oil from the rod end of the boom cylinders flows to line (17) and passage (18). Return oil in passage (18) is blocked by spool (11). Return oil in line (17) flows to the boom control valve and then to the return hydraulic system and the hydraulic tank. The boom raises.
Boom Lower (Without Regeneration)
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| Illustration 3 | g02163755 |
Boom drift reduction / regeneration valve (BOOM LOWER without regeneration) (1) Boom drift reduction / regeneration valve (2) Passage (3) Passage (4) Check valve (5) Spool (6) Passage (7) Manual lowering valve (8) Line relief valve (9) Passage (10) Spring (11) Spool (12) Solenoid valve (13) Passage (14) Spring chamber (15) Spring (16) Passage (17) Line (18) Passage (oil flow to rod end of boom cylinders) (19) Passage (oil flow to head end of boom cylinders) | |
When the boom joystick is moved for a BOOM LOWER operation, solenoid valve (12) is energized. Pilot oil flows through solenoid valve (12) and shifts spool (11). Spool (11) shifts to the left against spring (10) .
During a boom lower operation, oil flows from the boom control valve to line (17) and passage (18). Oil flows from passage (18) to spool (11). Oil flows through spool (11) to passage (9) and is blocked by check valve (4). Oil in line (17) flows to the rod end of the boom cylinders.
Passage (16) is open to the return circuit. The oil in spring chamber (14) flows through passage (16) and spool (11) to the return circuit.
Return oil flows from the head end of the boom cylinders to passage (19), passage (13), and to passage (6). Since the oil pressure in spring chamber (14) is low, the oil flow from passage (6) causes spool (5) to shift downward. The oil now flows from passage (6) and passage (2) to the boom control valve. Return oil flows from the boom control valve to the return hydraulic system and the hydraulic tank. The boom lowers.
Note: Boom drift reduction / regeneration valve (1) has a regeneration circuit.
ReferenceFor more information about the regeneration circuit, refer to Systems Operation, "Boom Hydraulic System".
Manual Boom Lower
Spool (5) prevents oil pressure in passage (19) from flowing to the return system when the boom is suspended from the ground. The mass of the boom, stick, and work tool creates pressure in the head end of the boom cylinders. In case the boom cannot be lowered because of engine problems or hydraulic system problems, the boom can be manually lowered. The boom can be lowered by opening manual lowering valve (7). Opening manual lowering valve (7) causes the pressurized oil in passage (19), passage (13), and passage (6) to be routed to the return system. The boom lowers when the pressure in passage (19), passage (13), and passage (6) flows to the return system.
ReferenceFor more information about manually lowering the boom, refer to Systems Operation, "Boom Hydraulic System".