The boom drift reduction valve is placed in the boom circuit between the boom control valve and the boom cylinders. When the joystick for the boom is in the NEUTRAL position, the boom drift reduction valve stops oil leakage from the head end of the boom cylinders. Stopping oil leakage prevents boom drift.
Boom Raise
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| Illustration 1 | g02712601 |
Boom drift reduction valve BOOM RAISE (1) Boom drift reduction valve (2) Drain port (3) Passage (4) Port (5) Valve (6) Passage (7) Spring (8) Spring chamber (9) Spool (10) Drain passage (11) Port (12) Port (13) Passage (14) Passage | |
When the joystick is moved to perform a BOOM RAISE operation, pilot oil is not sent from the pilot control valve to port (12) of boom drift reduction valve (1). Spool (9) does not shift.
The oil flow from the boom I and boom II control valves combines in the main control valve. The combined oil flow enters port (4) of the boom drift reduction valve. The combined oil flow flows into passage (3). As the oil pressure in passage (3) increases, valve (5) shifts against the force of spring (7). The oil in spring chamber (8) flows through passages (13) and (6) to passage (14). The oil delivery in passage (3) now flows through passage (14) to the head end of the boom cylinders.
Boom Lower
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| Illustration 2 | g02714923 |
Boom drift reduction valve BOOM LOWER (1) Boom drift reduction valve (2) Drain port (3) Passage (4) Port (5) Valve (6) Passage (7) Spring (8) Spring chamber (9) Spool (10) Drain passage (11) Port (12) Port (13) Passage (14) Passage (15) Spring chamber (16) Plug | |
When the joystick is moved to perform a BOOM LOWER operation, pilot oil is sent from the pilot control valve to port (12) of boom drift reduction valve (1). Spool (9) shifts until the spool contacts plug (16). The oil in spring chamber (8) flows through passage (13), the orifice in spool (9), spring chamber (15), and drain line (10). The oil then returns to the hydraulic tank.
The return oil from the boom cylinder head end enters passage (14). Since the pressure in spring chamber (8) is low, the oil in port (14) shifts valve (5) against the force of spring (7). The oil from the head end of the boom cylinders flows through passage (14), passage (3) and port (4) to the boom I control valve.