EN
Marine biofouling is simply unwanted settlement of marine life upon sub-surface hardware. Whether that is microorganisms such as bacteria and diatoms, or indeed macro organisms in form of mussels, barnacles and seaweed, whether it's growing on ship hulls, sea chests, piping, or offshore infrastructure, biofouling causes issues. Over years, we've completed in excess of 500 retrofit and maintenance jobs per year, and in every case issue was determined by our team to be due to impact of marine biofouling.
Causes of Marine Biofouling
A predictable ecological sequence occurs, “conditioning” film of large organic molecules deposits onto an initially clean surface immediately after immersing component in water. Within 24 to 48 hours, microorganisms colonize surface, forming biofilm. Bacteria and diatoms soon follow. Within 4 to 6 days, macrofouling larvae, including barnacles, tube worms, and mussels, settle and develop, attracted by organic-rich microenvironment. Some of important parameters that affect foulness are:
Water Temperature: Biological growth is stimulated by increased amounts of heat due to warmer tropical and sub-tropical waters and level of bio-fouling in tropical areas may be as much as 10 times that encountered in temperate and cold areas.
Salinity and Nutrient Levels: High nutrient levels in estuaries and coastal areas promote algal blooms and increase larval abundance, accelerating fouling rates.
Vessel Activity: Non-moving or very slow moving ships will foul more seriously than continuously moving ships that encounter drag/friction that resists fouling organisms. Some common examples of immobile/slow moving vessels include offshore oil platforms, FPSOs, and other types of anchored ships.
Surface Material and Roughness: More chemically reactive or coarser surfaces will allow for better settling and nutrient holding that helps to facilitate colonization more quickly.
Understanding these triggers allows operators to anticipate fouling risk based on trade routes, operating patterns, and seasonality. SME uses this knowledge to tailor preventive measures for each customer.
Operational and Economic Risks
So biofouling isn't purely aesthetic issue either. Biofouling results in very real performance costs that can be clearly measured:
Increased Fuel Consumption: Even slight slime film increases hull roughness, and thereby increases friction resistance. The IMO considers that moderate fouling is causing 10 to 20% additional fuel consumption and heavy fouling (like barnacle bloom) may increase fuel consumption up to 40%. In high fuel price setting this is an important cost element.
Reduced Speed and Voyage Delays: When vessels' efficiency is reduced by fouled hulls they reduce speed, using more engine revs and longer voyages to meet their timelines.
Accelerated Corrosion: The presence of biofilms also develops differing aeration cells under settlement leading to localized pitting and crevice corrosion seen at sea chest regions of cooling water systems operating in sea water. These regions are problematic in that there are areas of poor flow or stagnation where environment will be even more attacking towards substrate material.
Blockage and Equipment Failure: In piping systems macro foulants could cause flow constriction thereby decreasing heat exchanger efficiency as well as raising pumping energy requirement. If these causes develop into partial or complete pipe blockages that can lead to severe overheating or plant outage/expensive breakdown and emergency repair costs, then action has to be taken.
Regulatory and Commercial Penalties: A biofouling vessel is major contributor to spread of invasive species. The regulatory regime enforced on ship calls under port state control, and increasingly via environmental agencies, now involves physical inspection of hulls and cleaning of vessel surfaces. Failure will result in detention, penalties, denial of access to port.
Many of SME's service projects involve clean of biofouled systems and restoration of their working condition.
Prevention Methods: A Multi-Layered Approach
Smart solutions for biofouling mitigation. Biofouling control strategy combines surface treatments, active systems and operating routines. No single option can fit all cases, choice of solution is largely related to vessel trade route, design and maintenance regime.
Antifouling Coatings: Today, initial barriers to settlement are SPCs and foul-release silicone-based paints. The leaching action of SPC paints' contained biocide (such as Copper, zinc) release mechanism limits amount of settlement. The low adhesion surfaces offered by silicone foul-release paint allow water movement to wash any organisms off and work well for high speed vessels. They do have to be replaced periodically while dry and may encounter biocide restrictions if used in areas with environmentally strict zones.
Marine Growth Preventing Systems (MGPS): Sea chest and box cooler application. MGPS system ultimate for sea chest & pipework MGPS controls fouling. Through electrolytic anodes in sea chest/ MGPS, controlled amounts of copper and aluminum ions released effectively control larval settlement and prevent biofilm build-up within pipe work and vessels. Unlike leaching of coatings ions are not released until MGPS system is activated, giving more controlled results. SME systems have been supplied to hundreds of ships worldwide to provide reliable protection.
Regular Inspection and Cleaning: Routine underwater cleaning (remotely operated vehicles or divers) removes biofilm in its incipient stage and prevent macrofouling. Care is needed during cleaning as coating can be damaged. Cleaning in-water using capture systems, is becoming more of requirement in eco sensitive ports, to prevent any biofouling, and/or coating particles dislodged, entering environment.
Operational Measures: Fouling accumulation is exacerbated by long idle periods. It can be delayed through optimized voyage planning, such as high speed transits to enhance hull shear, and mechanical sweeping. For longterm static installations, regular drying out is effective.
The SME Advantage in Biofouling Prevention
At SME, we treat biofouling as complete system challenge, addressing it with engineering expertise, quality components, and responsive service. Our 100+ teams of electrical, mechanical and support engineers, from our 5,000sqm Nantong workshops, are global deployers-to provide anti-fouling techniques for your asset. Amongst other products and services we offer MGPS supplies, cloat surveys, retrofit sea chest protection, cooling water system maintenance. Your project is covered by our 12month warranty and operated via our ISO 9001/14001/45001 systems. Our aim is to provide raw product support for over 500 projects annually and over 1,000 spares for vessels worldwide to SP Management Contractor’s offshore partners and Chinese dockyards so do contact us, our target is to go beyond your biofouling fears to provide clean, economic operation.