Impressed Current Cathodic Protection System

or drydocking. The system must be reactivated within

HULL POTENTIAL SETTING OF SHIPS

2 hours after the activity is completed. You must

ENTERING BRACKISH OR FRESH WATER.--

NEVER energize the system if the ship is out of the

As a ship enters a port or bay that is river-fed, the

water (drydocked).

resistivity of the water will change as the salinity

changes. Operation of the ICCP system will be

Before the reference electrode is connected to the

affected by the changing water resistivity. The

controller, check the voltage between the reference

operator will notice the ICCP system operating at

electrode and the steel hull; it should be approximately

higher voltage outputs and lower current outputs. The

0.6 volt dc. The hull will be negative (-) and the

lower current output is caused by the higher

reference electrode will be positive (+). If the voltage

is zero, the reference electrode has an open lead, or the

impedance of the water. A higher voltage output is

lead or electrode is shorted to the hull. When the

required to drive the same current in the higher-

voltage is 0.6 volt or higher, the ship is receiving

resistivity electrolyte. The operator will record this

cathodic protection from an external source, which

condition on the ICCP log. Do not take action to

could be zinc anodes or an electrical leakage.

correct this condition by equipment recalibration

while the ship is in brackish water.

Inspect the controller and power supply wiring to

ensure the unit is properly grounded. Before

CATHODIC PROTECTION LOG.-- Normal

connecting the anode leads to the power supply, check

operating procedures require maintaining a Cathodic

for possible shorts. The voltage developed between a

Protection Log of the ICCP system operation on

disconnected platinum anode and the steel hull will

NAVSEA Form 9633/1 (fig. 11-14, view A, and

range from 1.0 to 2.0 volts dc. This can be read on a

11-14, view B). The readings will be recorded on these

high-impedance voltmeter. The polarity of the anode

logs daily and submitted to NAVSEA monthly, Logs

is positive (+) and the polarity of the hull is negative

submitted to NAVSEA are analyzed to identify those

(-). If this voltage is zero, you could have an open lead

systems that are not operating correctly. After analysis

wire or a shorted anode. When the voltage reads

of the logs is complete, a response is sent to the ship or

between 2.0 to 5.0 volts, it indicates that the anode lead

type command (TYCOM) indicating the operational

is immersed in seawater.

status of the equipment as interpreted from the logs.

HULL POTENTIAL SETTING OF SHIPS IN

This response will recommend corrective actions to be

SEAWATER.-- The ICCP system is designed to

taken, if required.

operate automatically and requires a minimum

Output Check.-- A particularly significant value

amount of maintenance. The operator normally sets

recorded on the log is the output check. The values

the hull potential at -0.85 volt. When the voltage

recorded will range from practically zero to 1.0 volt,

between the hull and the reference electrode is more

representing 100 percent current output. If the values

positive than the voltage set by the operator, the output

of the controller increases. This causes an increase in

range between 0.3 and 0.5 volt, the system is operating

the anode current output from the power supply until

at 30 to 50 percent capacity.

the voltage between the hull and the reference

Power Supply. --The daily current output is

electrode approaches the set voltage. A voltage

recorded for each power supply. Ampere values may

between the hull and the reference electrode that is

vary, depending on the power supply, maximum

negative to the set voltage causes a decrease in

output, and current demand. Two capacities of power

controller output, thereby decreasing the anode

supplies are used, 0 to 150 amperes and 0 to 300

current output.

amperes.

The optimum range of polarization or hull-to-

ICCP MAINTENANCE.-- The ICCP mainte-

reference electrode potential for a ship with an

nance will be performed according to the Planned

ordinary steel hull is from a -0.80 to a -0,90 volt to

Maintenance System (PMS). Take daily meter

the silver/silver chloride reference electrode.

readings on the panel and record them on the log. A

Increased anode current will result in hull potentials

quarterly check must be performed on the shaft

more negative than the optimum amount. Increasing

grounding assembly. Every 24 months the panel

the negative potential does not provide more

meters must be calibrated according to PMS require-

protection. If exceeded, this will result in hydrogen

generation at the hull surface.

ments.

11-14