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HJ-241 / HSRX
feature which prevents the potential falling below -
1100mV referenced to a silver / silver chloride
reference electrode.Aluminium, G.R.P. and Wood
Hulls (Other Than Steel or Carbon Fibre)
4.2 Earth Bonding System -
(Not Normally Current
Conducting)
Refer Drawing:
85114 Earth Bonding System Recommendations and
Layout.
In the case of an aluminium Hull, an engine stringer
or any other continuous longitudinal member may
be used as the bonding strip. All junctions should
preferably be welded, but if bolted, should be clean,
have a good contact and be regularly inspected and
maintained.Steel Hulls and Carbon Fibre Reinforced
F.R.P. Hulls
For Steel hulls and Carbon Fibre
reinforced F.R.P Hulls, the Jet Unit
must be electrically insulated from
the Hull.
C
AUTION
An insulating kit is supplied with the Jet Unit for
steel Installations.
For Carbon Fibre Reinforced hulls, an alternative
reinforcing fibre (such as glass) must be used in the
area where the jet unit is mounted to ensure that
Carbon Fibre does not contact the jet unit or
fasteners.
4.3 Earth Bonding System (Not
Normally Current
Conducting)
Refer Drawing:
85114 Earth Bonding System Recommendations and
Layout
If a negative earth system is used on the vessel, it
Must Not be connected to the Jet Unit.
4.2 E
B
S
ARTH
ONDING
YSTEM
4. Every part of the vessel electrical system should
have Two wires to it, a positive and a negative
wire.
5. With electrical auxiliary equipment installation
be guided by your electrician. Do not earth
electrical equipment to the Jet Unit, but to a
separate earth.
4.3.1 Checking the Insulation
The insulation between the Jet Unit(s) and the steel
hull should be regularly checked.
1. With the vessel out of the Water
Rinse the sea salt from the jet/hull area using
fresh water.
The resistance between the Jet Unit(s) and the
Hull should be 1000 ohms or greater. If the
reading is below 1000 ohms, the fault should be
investigated and rectified.
2. With the Vessel in the Water
For Steel Hulls:
a) Place a silver / silver chloride half cell in the
seawater.
b) With the silver / silver chloride half cell
connected to the 'common' of a digital
voltmeter (set to read 0 to 2000 mV).
c) Connect the 'positive' terminal to the hull and
note the reading.
d) Repeat with the 'positive' terminal connected
to the Jet Unit(s) body.
e) Place a large zinc anode in the seawater and
electrically connect the hull to the anode.
f) Repeat the digital voltmeter readings.
g) If Jet Unit(s) is insulated from the hull, the mV
readings for the Jet Unit(s) should not change.
h) The mV readings for the hull should be more
negative (eg: The reading could be -800mV
without the large zinc anode connected and -
850mV with the large zinc anode connected to
the hull).
i) This test can also be carried out with a
Corrosion Monitor if fitted
3. In Service
The insulation between the Jet Unit(s) and the
steel hull should be regularly checked.
4 PRECAUTIONS AGAINST CORROSION
- (N
N
C
OT
ORMALLY
URRENT
C
)
ONDUCTING
4.5
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