Hitachi ZAXIS 30U-5N Operator's Manual page 171

If the front attachment is not loaded
d
WARNING: Loosen overload relief valve slowly. If it is
loosened rapidly, the boom may also lower rapidly. Do
not loosen it more than 3/4 turns, as the hydraulic oil
may spout.
1. Loosen the overload relief valve slowly by checking the
movement of boom.
2. After checking that the boom is completely lowered,
tighten the overload relief valve.
Model
ZX30U-5N, 35U-5N
ZX50U-5N
ZX60USB-5N
If the front attachment is loaded
1. Put the matching marks on lock nut in overload relief
valve and adjusting screw in the boom raise circuit
(cylinder bottom side).
d
WARNING: Loosen the adjusting screw slowly. If it is
loosened rapidly, the boom may also lower rapidly.
2. Loosen the lock nut. Loosen adjusting screw slowly by
checking the movement of boom.
3. After checking that the boom is completely lowered,
align the matching marks and tighten the lock nut.
Torque: 28 to 32 N·m
(2.8 to 3.2 kgf·m, 20 to 23 lbf·ft)
OPERATING THE MACHINE
Tightening Torque
70 to 80 N·m (7 to 8 kgf·m, 52 to
59 lbf·ft)
60 to 64 N·m (6 to 6.4 kgf·m, 44
to 47 lbf·ft)
60 to 70 N·m (6 to 7 kgf·m, 44 to
52 lbf·ft)
ZX30U-5N, 35U-5N
Overload Relief Valve in
Boom Raise Circuit
ZX50U-5N
Overload Relief Valve in Boom
Raise Circuit
5-29
Fig. 1
Valve Body
Adjusting screw
Lock Nut
ZX60USB-5N
Overload Relief Valve in Boom
Raise Circuit
MADG-05-001
Lock Nut
Adjusting screw
MADG-05-004
T152-03-03-015
MADG-05-005
T566-03-03-018