Hitachi ZX27U-2, Operator'S Manual

Page: 114 / 230

OPERATING THE MACHINE
5-26
3. Lower the boom in the following procedures.
If the front attachment is not loaded.
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.
Tool : 24 mm
Torque : 59 to 69 N
⋅
m
(6 to 7 kgf
⋅
m, 43 to 51 lbf
⋅
ft)
2. After checking that the boom is completely lowered,
tighten the overload relief valve.
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).
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.
Tool : 17 mm (Lock Nut)
Torque : 27 to 31 N
⋅
m
(2.8 to 3.2 kgf
⋅
m, 20 to 23 lbf
⋅
ft)
3. After checking that the boom is completely lowered,
align the matching marks and tighten the lock nut.
NOTE: Section A is not equipped for ZX27U
-2
in right
illustration Fig 1.
ZX27U
-2
/30U
-2
/35U
-2
T1LA-03-03-001
T152-03-03-015
ZX40U
-2
/50U
-2
T1M9-03-04-001
T566-03-03-018
Overload Relief Valve in
Boom Raise Circuit
Valve Body
Adjusting Screw
Lock Nut
Overload Relief
Valve in Boom
Raise Circuit
Adjusting Screw
Fig, 1
Lock Nut
A