Impressed Current Protection; Steel Hulls And Carbon Fibre Reinforced F.r.p. Hulls; Earth Bonding System (Not Normally Current Conducting); Checking The Insulation - Hamilton Jet HJ212 Installation And Service Manual

Precautions Against Corrosion

Impressed Current Protection

Impressed current protection may be used if desired. Follow the supplier's instructions. Impressed current
systems should have a "fail safe" feature which prevents the potential falling below -1100mV referenced to a
silver / silver chloride reference electrode.

Steel Hulls and Carbon Fibre Reinforced F.R.P. Hulls

For steel and carbon fibre reinforced (F.R.P) hulls, the jet unit must be electrically
insulated from the hull.
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.

Earth Bonding System (Not Normally Current Conducting)

If a negative earth system is used on the vessel, it must not be connected to the jet unit.
Each part of the vessel electrical system should use two wires, a positive and a negative.
With electrical auxiliary equipment installation be guided by your electrician. Do not earth electrical
equipment to the jet unit, but to a separate earth.

Checking the Insulation

The insulation between the jet unit(s) and the steel hull should be regularly checked.
With the vessel out of the water
Rinse the sea salt from the jet unit/hull area using fresh water.
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The resistance between the jet unit(s) and the hull should be greater than 1000Ohms.

With the vessel in the water
For steel hulls:
Place a silver / silver chloride half-cell in the sea water.

Connected the half-cell to the common of a digital voltmeter (set to read 0 to 2000mV).
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Connect the positive terminal of the voltmeter to the hull and note the reading.

Repeat with the positive terminal of the voltmeter connected to the jet unit(s) body.
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Place a large anode in the sea water and electrically connect the hull to the anode.

Repeat the voltmeter readings.
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If jet unit(s) is insulated from the hull, the mV readings for the jet unit(s) should not change.
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The mV readings for the hull should be more negative (e.g. if the reading is -800mV without the anode
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connected then with the anode connected the reading should be approx. -850mV).
This test can also be carried out with a corrosion monitor if fitted.
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Installation and Service Manual