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Shipowners and Technical Superintendents, within SME Group, they have been trying to solve only this question for more than 20 years ago. This has not really changed, but the conversation, more the heated debate – is around MGPS vs the ultrasonic alternative – “ultrasonic antifouling”. Here’s the “layman’s guide” as we found it into each of the below solutions, based on the research on hundreds, if not thousands of yachts in excess of 500 vessels. Whether sailing at sea or at berth:
The Core Mechanics: How Each System Works
But the price comparison cannot be made until you understand that biofouling prevention takes different approaches.
MGPS systems are electrolytic and require an anode, usually copper and aluminum, to be installed in the sea chest or pipework. If a current of a low voltage is used in these anodes, metallic ions will be released into the seawater. These ions change the environment so that barnacles, mussels and algae cannot adhere to the internal pipe surfaces and near the hull at the intakes.
The difference between the two is that ultrasonic antifouling has transducers inside the hull or on the wall of pipes. They produce cavitation and pressure changes which are high-frequency. It is thought that this hinders the biological functions of the larvae and will not allow the release and attachment to surfaces. It produces no chemicals that are dumped into the water.
Cost Analysis: Initial Investment and Operational Expenditure
To our clients, at SME, we see costs divided into three parts: Capital expenditure (CAPEX), Installation and Long-term operational expenditure (OPEX).
Initial CAPEX and Installation: Generally, the first expense for an ultrasonic system is often less that of a fully functional MGPS where single anode and a control panel removed. When it comes to installation that figure changed. Installation of ultrasonic transducers to the hull would involve an area on the hull that would either need to be dry-docked or need to carefully welded in. Installation of MGPS, on completion, would happen alongside installation of anode manifold in relation to sea chest, and would occur during ship docking (which our service group performs for 1000 vessels every year). When it comes to installing an ultrasonic device on a new build it will be nearly cost equal to that of installing MGPS, and for retrofitting can often be effective replacement for the currently installed and far simpler through hull fittings.
Operational Expenditure (OPEX): The consumable anodes are required for the MGPS. The life span of these varies from between 12 and 18 months depending on water salinity and operating time. The annual expense of the anode is low, but small. Although Ultrasonic systems are slightly more energy consuming, they do not require any consumables (anodes). They also degrade in performance over time due to aging of transducers (which need replacing at 3-5 years). The problem with doing the numbers for our client is that the anode replacement problem can cost us more on the OPEX for our clients, but we can guarantee them their protection.
Performance: Coverage, Efficacy, and Reliability
When it comes to performance -- not on paper in sales literature, but actually in the real world -- the two technologies very rarely match up.
MGPS Performance: Our experience at shipyards worldwide is that MGPS can give an overall consistent, reliable protection of the entire seawater cooling system, including the pipework, heat exchanger and condenser. It has been especially useful to prevent hard-shell growth (barnacles and mussels). The vessel's speed and sound properties of water have no impact on the ion release. In a field that regards downtime as significant revenue, MGPS leads the way for high flow rate seawater applications in commercial ships.
Ultrasonic Limitations: Shadowing is a problem for an ultrasonic system. Passing sound waves do not flex around corners and are highly effective in pipes that have no bends or obstructions, but less effective in pipes with bends or obstructions or in long pipe runs with many bends or obstructions. In addition, turbidity, salinity, and water temperature play a significant role in the performance of the system. When the ship is moving slowly, or in port, the cavitation effect proves less significant. We have seen vessels where ultrasonic systems left the sea chest totally clean and yet the distal end of the cooling line did not get protected resulting in overheating.
Limitations and Operational Drawbacks
All technology has a vulnerability. It is important for fleet managers to know these.
The MGPS Drawback: The major restriction is the environmental and operational restriction on release of copper in the MGPS. The concentration is low; some ports with environmental laws are not suitable for copper based anodes. Further, anodes are less efficient when running a long time in freshwater or brackish water and will consume more. Periodic calibration and hull potential testing are also necessary in the system, along with the ability to correct for stray current corrosion a service our technical support engineers provide routinely.
The Ultrasonic Drawback: Another problem associated with ultrasonic transducers is fouling (beyond the shadowing effect). Whenever the face of the transducer becomes covered with slime or a biofilm, the output of the transducer falls significantly. In addition, such systems are not very effective in assuring and minimize the possibility of hard-shell growth, only in restraining the settlement of larvae on the surface. Waves of ultrasound are not strong enough to shed a barnacle once it attaches. This will definitely have to be in conjunction with a Deep-Sea MGPS on the ship, and not in place of it.
The SME Verdict: Which One Should You Choose?
No 'one size fits all'. From our warranty data across vessels and post-service feedback from the past 12 months, we have collated service recommendations by vessel and by trade routes below:
MGPS remains the only proven cost effective and guaranteed system across the world, on large ocean going vessels, running at high speed, and high flow rates, for example bulk carriers, tankers, containerships etc as this gives a life-long application system for the entire sea water cooling system. It ensures that our clients have a functioning sea water cooling system. An ultrasonic sea chest would be extremely useful on ships doing short voyages within an environmentally sensitive area, however, will not serve for the entirety of the sea water system. SME lives by the mantra of "Aim Beyond Your Concern."
Rather than buy the box off the shelf, we analyze your vessel's operational profile and then go through a complete and comprehensive risk analysis to ensure we propose the very best solution for your fleet. This may be a completely new MGPS system with latest controller logic or to convert and to optimize anode life. The retrofit solution helps reduce anode consumption on a year-on-year basis, and will considerably increase their lifespan. SME has what you need whether it comes to installing new systems, upgrading and troubleshooting old equipment or performing routine maintenance – we have all aspects of electrically and mechanically operated equipment covered, managed by the experienced team here.
We employ over 100 staff and carry out all our operations under our strict ISO procedure; consequently, we are able to guarantee an effective, environmentally friendly and antifouling management, while ensuring maximum operational uptime and safeguarding your future investment. Still struggling to understand what would work perfectly for your fleet? Why not call our team, whose team members will readily assist you with a real time effective cost benefits calculation to your fleet with the aid of the available data for what it's all about, a well-applied hands on practice!