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A ship's ICCP system is composed of several silent sentinels: the underwater fittings, propeller and ship hull. These lessen costly corrosion and extend drydocking time and maintain structural integrity. For many ship owners and technical superintendents, however, ICCP is the “fit and forget” kind of equipment, until it activates an alarm or there is a problem with the shaft earthing. But it's really quite easy – proactive, efficient monitoring – to ensure a system's lifespan is optimised, unwanted off hire is avoided and total ownership cost minimised.
Define Clear Performance Baselines
The very first step to effective monitoring is to not to compare readings until the monitoring begins. There needs to be a baseline for every vessel's ICCP configuration. This includes:
Mostly steel hulls can be found, and are usually provided with reference electrode potential between -800 mV and -900 mV vs. Ag/AgCl.
Current produced by anodes (in amperes per anode).
Normally operating transformer voltage and current rectifiers.
Shaft grounding current (in case of shaft earthing system).
Document these values immediately after a successful system commissioning or immediately after a maintenance overhaul scheduled for the system. Keep them in a common logbook or computer-generated sheet; available to all engineers. Without this reference there is no way to distinguish between drift and degradation. According to SME's service records over 70% of sudden failures are actually a slow drift and are not detected as there is no baseline.
Implement a Structured Visual and Digital Inspection Routine
It's not essential to be running costly remote IoT systems on every ship to monitor (although it does help). A solution that is cost effective and reliable will include a combination of:
Weekly visual checks, carried out by the ship's electrician:
Test for unusual overheating, smoke or loose terminals of transformer rectifier.
Look for moisture or corrosion in reference electrode junction boxes.
Check all the panel LEDs and meters are working and functional.
Readings taken each month by the chief engineer:
Record and record anode current, voltage and reference potential with constant load (steady steaming/at berth).
Record variation related to speed, sea water temperature – this is a normal variation and trend very important.
Quarterly trend analysis:
Record your reading each month on the baseline. As the potential is held constant and the anode current is slowly increased, degradation of the coating (more bare steel to be protected) is indicated. A decrease (drop) in current with a decrease in potential (voltage) is caused by depletion of the anode or increased conductivity or fouling of the reference electrode.
SME's technical support engineers suggest to use an easy to use Excel template that has conditional formatting (Green/Amber/Red) to identify "out of range" values as they occur in real-time. This is the process of transforming raw data into actionable intelligence, without relying on special software..
Leverage Shaft Earthing and Hull Potential Correlation
A relationship that is not always monitored is the relationship between ICCP performance and the earthing current for the shaft. If the ICCP system is working properly, the shaft earthing unit should pass very little direct current (usually < 5 A). An increasing shaft grounding current and a decreasing hull potential are usually indicative of a faulty reference electrode or a polarisation problem, rather than a shaft fault. These two parameters are tested weekly and can be used to identify reference electrode drift early, before it becomes excessive and results in over protection of the ICCP and anodes are wasted with blistering of the paint or under protection and leads to accelerated pitting. Simple cross check process, described in SME's field data, can reduce troubleshooting time by 40%.
Adopt a ConditionBased Maintenance (CBM) Mindset
Old-fashioned fixed interval overhauls are wasteful. Instead, rely on your monitoring information to take corrective measures:
Replace anodes only when the output current is measured and is below 80% of the initial reading for three consecutive readings (excluding wiring error).
Change or clean reference electrodes if potential readings change or fail to react to changes in current.
If the voltage current characteristics are more than ±5% away from the commissioning curve, adjust the transformer rectifier.
This aligns nicely with SME's 12-month warranty approach, under which we promise a guarantee for our retrofit/repair work and we educate your crew on the early warning signs. On an annual basis, we review your logs with our high precision portable meters to ensure that the logs are accurate on board. False alarm and missed fault are eliminated with the dual layer verification.
Use Alarm Management, Not Alarm Fatigue
These days, ICCP panels have high/low potential alarms, anode overcurrent alarms and the ground fault indicator. However, nuisance alarms (fast speed changes, brackish water intrusion etc.) can cause desensitized team members. Efficient monitoring means:
Delay alarm (e.g., 30 second trip delay) to prevent from triggering when it isn't supposed to.
Maintaining record of every alarm event, such as the vessel's operating condition (speed, seawater salinity/draft). Over time you will begin to know the difference between “informational” alarms and “critical” alarms.
Hand testing alarm function for every port stay, either by setting the self test mode on the panel or by momentarily changing the setpoint. This means the alarms in the circuit are working properly—all the other crews who do not do this are not.
SME's service engineers have had cases where they were called in to replace a shaft bearing that had been destroyed because of ICCP but the service started with the alarm relay failure, while the service crew was ignoring the alarm panel for months. Active alarm management takes care of such expensive misdiagnoses.
Conclusion
There's no point in spending the most money on the most expensive gadget when it is a matter of discipline, correlation and timely intervention. Baselines, structured visual/logged inspections, cross checking the shaft earthing data, condition based triggers and careful management of the alarms, combined with commissioning the ship for annual professional audits can help provide the vessel with a minimum of crew workload and a maximum of reliability.
With more than 500 projects completed annually, throughout world wide shipyards, SME is convinced that any ship with a systematic monitoring plan will have 60% fewer delays due to ICCP and a much lower usage of spares. With over 100 technicians and engineers at your service, we are on hand for anything from emergency repairs to scheduled overhauls or to look at your monitoring logs. As a reminder, it's not to respond to a problem, but to plan ahead and look beyond your concern to the problem. So begin to hone your monitoring process now, and your hull will thank you for it for years.