STT113 TOWER CRANE OPERATION AND SERVICE MANUAL
4B 2
2. Earthing
Attention
：
The earth wire of tower crane mustn’t be replaced by fuse or the core of
switch and cable.
There are three kinds of earthing modes
：
A.
The earth substance adopts the standard earth stake,
either use φ33x4.5, 1.5m long steel tube or L70x70,
1.5m long angle steel.
B.
The earth plate is made of steel plate or other stretched
metal plate with an area of 1m
2
. It was vertically inearthed
1.5m depth from the ground surface.
C.
Copper conductor with cross section more than 28 mm
2
or iron conductor with cross section more than 50 mm
2
is
inearthed in the wire casing. The inearthed depth is to be
determined by earth resistance.
In above earthing modes, the copper conductor section coming from the earth
substance should be more than
25mm
2
. If the soil conduction is poor, inearth sodium
chloride (salt) in the soil and pour some water. For traveling type of tower crane, each
section of rails must be electrical connected, and the two rails must be electrical
connected. The earth resistance is less than
4Ω
.
