Hitachi ZX27U-2 Operator's Manual page 114

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
illustration Fig 1.
OPERATING THE MACHINE
in right
-2
5-26
ZX27U /30U /35U
-2 -2 -2
A
Overload Relief Valve in
Boom Raise Circuit
ZX40U /50U
-2 -2
Overload Relief
Valve in Boom
Raise Circuit
Fig, 1
T1LA-03-03-001
Valve Body
Adjusting Screw
Lock Nut
T152-03-03-015
T1M9-03-04-001
Lock Nut
Adjusting Screw
T566-03-03-018