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Operating a vessel with a marine growth prevention system (MGPS) is not simply about compliance, it is a real-world operational necessity. Here at SME Group we have spent over 20 years supporting operations personnel and superintendents on board ships – and the impact of an ineffectively managed MGPS we have seen in ships is nothing short of phenomenal, resulting in condenser fouling, increased fuel efficiency and unscheduled dry docking. To put it simply, seawater cooling is the vascular system of your ship and an MGPS acts as your immune system, if left unchecked it will rapidly result in micro-organisms, barnacles and mussels colonising the internal pipework decreasing fluid flow and the efficiency of the cooling process.
Over the years our team at SME have completed over 500 retrofits and service projects annually from our Nantong facility, in Nantong servicing a range of more than 1,000 ships annually. The benefit of working with experienced engineers is that we have observed the most cost effective way to keep your MGPS running efficiently is to be proactive and utilise our simple checklist to minimise the chances of an ineffectively managed system; the list provides you with all you need in a clear and easy format for Chief Engineers and their teams.
Pre-Inspection Safety and System Isolation
The first thing that is foremost is safety: before any physical intervention. The MGPS is electrically energised and is housed in the sea chest or strainer area where strict lock out/tag out (LOTO) procedures must be followed. Start your checklist checking the power supply to the MGPS control panel is fully isolated and system is de-energised. Check that seawater inlet valve is closed and tagged. Monitor oxygen levels and ensure the absence of toxic gases in the compartment—especially if the vessel has been in stagnant or brackish water for an extended period. Note ambient temperature and humidity in the log book; these have an effect on the performance of the electrodes. Lastly, which is not an optional step, require your mechanical and electricians to wear the proper personal protective equipment for all face, hands and body contact with the mineral deposits on the electrodes—such as chemical-resistant gloves and face shields.
Visual Inspection of the Control Panel and Power Unit
MGPS brain is stored in its control panel. Take the panel down and give it a thorough visual examination. Check for signs of overheating, which include burnt terminals, colour changes in the terminals, or burning smells to the electrical insulation. Match all LED lights up with your Manufacturer's reference sheet: if any lights aren't shining fully or are blinking they could be because of the rectifier blowing out or the fuse failing out. Check the earth leakage relay; this can trip too early in a vessel with a lot of vibration, such as in a commercial vessel. Note down the incoming AC voltage and output DC current and voltage. If the output current decreases abruptly (more than 15% below nominal) although there is no change in the conductivity of the water, there is a problem with the anode and it is likely to fail soon. Make sure all cables are secured and there are no moisture entry points into the cabinet, especially when the mounted panel is mounted in an engine room area that may be exposed to moisture. Additionally, SME's technical support engineers always suggest thermal imaging scan of the panel terminals to identify hot spots that are not visible from the outside.
Electrode (Anode) Inspection, Cleaning, and Measurement
The anodes are the first line of defense of your MGPS. Remove anode assembly from sea chest and ascertain even consumption. Pitting on one side only is caused by incorrect mounting procedures or loose electrical connections. Gently remove the oxide and calcareous layer, which has formed on the active surface, using a non-metallic brush (nylon or brass). Avoid using steel wire brushes since they can catch foreign particles and worsen localised corrosion. Using the calibrated callipers, measure the remaining anode length and diameter and record these measurements relative to that read off on the previous dry-docking. Replace immediately if greater than 60% of the mass has been lost from the anode or the core wire shows signs of exposure. In addition, check the insulating bushings of the electrode holder; cracks or carbon tracking are a frequent and common failure mode which can cause short-circuits.
Reference Electrode Calibration and Functionality Testing
The protective current output is determined by the reference electrode (usually silver/silver-chloride). The maloperation of a reference electrode would lead to an over protection or under protection (e.g. excessive hypochlorite production or growth) of the system. To test, remove the reference electrode lead and place it in a bucket filled with the same seawater and connect it to a portable copper copper-sulphate reference electrode, and measure the potential of the reference electrode. Reading should be within the indicated millivolt (mV) range.If deviation exceeds ±20mV a complete cleaning of the porous tip of the reference electrode is necessary using distilled water and never with any form of scratching or sanding. Connect the test bucket and pour in a little bit of saltwater into the test bucket to create a high conductivity situation; watch the control panel change by adjusting the output current. This may be the most important of these dynamic tests, but is frequently not included in assessments of overall system health.
Seawater Strainer and Flow Verification
The highest grade of protection means little when the target area is out of reach. Ensure the main seawater strainer is clear, free of all shellfish, plastics and debris, etc. in the baskets. A blocked strainer can lead to slower sea flow and consequently altered contact times with the anodes, reduced levels of the key species on injection to the condenser etc. Clean the sea strainer, and read the pressure differential across the sea strainer on the differential pressure gauge on the front of the unit - if this exceeds your base " clean" reading (usually 0.5 bar) there's a block before the sea strainer. Once this is re assembled (with fresh gasket, and tighten the nuts to an even torque value to stop any warping) you may open up the sea valve slowly ( if it had to be closed ) and then bleed air from the sea inlet valve as the air can cause a variance in MGPS current readings. Using the pressure on the pump discharge read the flow rate of sea, if its 10% more than a known reading, even with sea strainer cleaned, then a chemical cleaning is probably needed.
Conclusion: A Culture of Proactive Care
One aspect we know more certainly than anything else about a successful engineering team is how diligently they complete their MGPS maintenance list. At SME Group we get better than concerned by giving your people processes that remove the risk of crisis occurring. With our 12-month warranty on project services and our over 100 employees’ combined years of experience, time after time SME has already proven that a thorough and managed inspection round leads to a more than 40% reduction in unplanned operational shutdowns. If your team takes such thorough precautions your system is capable of lasting for the entire voyage life of a ship. Keep this in mind when your system requires refurbishment or a whole new strategic approach to operations. When the winds turn unfavorable, SME and more than 100 other technicians, like us, are available and ready. All across China’s mainland and at countless yards overseas, 24/7 whenever there is any need of an instant solution and the proper part/service for your yacht or vessel, SME stands ready to execute promptly so that it always maintains the highest of commercial capabilities, voyage after voyage after voyage after voyage.