2-49
4.13.4 COUNTERBALANCE VALVE (IDENTIFICATION STAMP “D” FOR DERRICKING
CYLINDER)
Specifications
Max. working pressure 20.6 MPa (210 kgf/cm
2
)
Withstand pressure 30.9 MPa (315 kgf/cm
2
)
Max. flow rate 50 L/min
Rated flow rate 40 L/min
Allowable leak amount 0.05 cc/min or less (pressurizing 20.6 MPa [210 kgf/cm
2
] from B port)
Pilot pressure 1.18
+0.3
MPa [12
+3
kgf/cm²] with the valve open
Spool aperture area Equivalent to 2.6 (in spool stroke)
Check cracking pressure 0.098 MPa [1 kgf/ cm
2
]
Operating temperature range -10 - +80ºC
Troubleshooting and countermeasures
Abnormal Phenomenon Cause Remedy
During service, the derrick
cylinder is retracted (the
boom being lowered)
･ Defect in check seat (1) or (2), or
inclusion of foreign matter
･ Damage to O-ring (1), (2), (3) or (4)
･ The pilot hole (0.3) is clogged with
foreign matter and the spool remains
in the moved state, resulting in the
check seat (2) being left open
･ Removal of foreign matter
･ Replacement of O-ring
･ Removal of foreign matter from the
pilot hole
The derrick cylinder fails to
retract (boom not lowered).
･ Pilot hole (0.3) is clogged with foreign
matter
･ Removal of foreign matter from the
pilot hole
65200-01000
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