- Calcareous (shells, worms, shells)
- Non-calcareous (sea grass, algae and biofilm mucus).
Biofouling leads to a critical narrowing of the pipeline inner space and eventually leads to the shutdown of vessel’s systems, the shutdown of machinery, clogging of intake water openings and reduction of heat exchanger performance. In this case,
cleaning the internal cavities of pipelines or box-coolers is impossible by any means - mechanical, chemical, or sound... etc., and usually subject to disassembly and replacement. Therefore, the biofouling topic is well-known and crucial.
There is an extensive research knowledge base on the biological fouling in Russia and worldwide. Researchers agree that there are no existing submerged in seawater surfaces that could be free of biological life. Bioorganic colonization of the surface, e.g. in the pipe cavity is consistent and sustainable, and passes conditionally three stages
1st stage
Formation of macromolecular layer in presence of molecules of proteins, fats, polysaccharides in water. This is the so-called substrate for further biofouling. It takes seconds and occurs immediately when the surface is in contact with water, unless there is an obstruction impact.Stage 2
Formation of bacterial algal film, bacterial adhesion. In this case, microorganisms secrete extracellular polymers that provide a strong attachment to the surface. The biofouling process becomes irreversible if there is no counter-actionpreventing biomass attachment to the surface. Takes hours and days.
Stage 3
Colonization of a surface covered with biofilm by calcareous and noncalcareous macro-organisms. It takes weeks to months. At this stage, it is impossible to counteract the colonization process, except with a mechanical removal of biomass.Most of the seawater fouling research on marine structures has been done for temperate and warm seas. Unfortunately, the same research in the northern seas is not sufficient for the world science, perhaps that is why there is still the opinion that bioactivity, associated with the biofouling of submerged objects at high latitudes is reduced to zero due to low temperature. However, the research carried out by the P.P. Shirshov Institute, Russia argues this conclusion. Microflora samples collected at different times from the White and Kara Seas show that, together with increasing of human activity in the
Arctic zone, the amount of bioflora capable of forming a substrate of biofilm on submerged structures has increased as well in the recent decades. As well as the number of microorganisms types capable of expanding and colonizing the internal and external surfaces of objects under water.
In addition to research in the sphere of biofouling of both offshore structures and internal surfaces of supporting systems, Scientific and practical developments have been carried out in the field of methods of counteracting this biological process using various physical and chemical principles. Many theoretical and practical methods have been developed to prevent the biofouling of cooling systems and seawater supply systems. These methods for controlling the formation of harmful sediments include mechanical, electrochemical, ultraviolet and ultrasonic effects on biomass.
In our view, the simplest and most versatile way to prevent bio-fouling is an electrolytic method. This prevention mode is activated at the very first stage of biofouling while the process is reversible. The electrolytic anti-fouling method is based on the negative effect of certain metals free ions on the seawater bioorganism’s ability to attach themselves to the pipeline walls, as well as in suppressing the microflora’s ability to grow and reproduce. Extensive research has established that
copper ions are able to inhibit of bioflora life even in the smallest concentrations. At the same time, aluminum hydroxide ions forming because of flocculation copperaluminum flakes, evenly spread along the pipelines and prevent microorganism’s adhesion to their walls. Moreover, the resulting copper and aluminum ion film protects the piping surface from corrosion.
This method uses two anodes made from copper and aluminum, located either in the seawater pump filter, or near the piping inlet in the sea chest or in the cooling box. The anodes are supplied with direct current, which leads to releasing copper ions and aluminum hydroxide ions, which negatively affect biological microorganisms and prevent corrosion processes in the inner spaces of pipelines and other ship systems.
In general, the anti-fouling system consists of a power supply unit with a control panel, pair of copper and aluminum anodes, junction box and cables (pic 1). Anti-Fouling unit works on the principle of electrolysis, which consists of simple electrolytic cell having anode and a cathode and a D.C voltage applied between the two, the output voltage is automatically adjusted to maintain the current requirements. The process results in copper ions generation which is further transported within the system through water flow. It is well known phenomenon that the main fouling organisms can be inhibited from growing by the introduction of very small quantities of copper into the water. The required dosage per litre is only a few parts per billion and since the sea water is a good electrolyte, a low DC voltage is sufficient to provide the necessary current. The controlled electrolytic dissolution of copper to inhibit macrofouling in the seawater intakes and piping systems has been employed for many years and has been known as effective substance to marine organisms. Controlled release of copper at parts per billion (ppb) levels effectively inhibits the attachment and growth of algae, mussels, oyster, barnacles and other calcareous and non-calcareous species. Furthermore, maturing (live) organisms have a threshold tolerance to copper and by exceeding ambient levels they will exfoliate, thereby gradually cleaning out and already fouled system.
The system operates automatically and does not require constant monitoring or special start-up mode. This anti-fouling system design provides continuous protection without using any toxic substances, complex mechanical or ultrasonic systems.
Such anti-fouling and inner pipeline surfaces protection equipment can be installed on both large-tonnage vessels and small boats. In this case, all pairs of anodes from all sea chests are commuted to one multichannel panel.
PSS Corporation, Russia, Perm city, has obtained a vast experience in design and manufacturing of the biofouling prevention systems for ships of all classes. The manufacturing cycle for such equipment, together with testing and preparation for delivery to the customer takes from 6 to 12 weeks, depending on the number of anodes and seawater pump characteristics. The larger pump capacity, the larger size of anode units is required. Anti-fouling systems of the PSS Corporation have already been delivered to many shipyards and installed on ships of different classes. The PSS Corporation also provides installation and commissioning of equipment.
The PSS Corporation offers full service support to the supplied equipment during the life cycle providing continuous monitoring of the individual components functioning and accumulate statistics on the units efficiency. Experience of work with anti-fouling systems proves that such equipment reduces the cost of dry dock maintenance several times.
For 30 years now, the company has been supplying electrical equipment for vessels oil and gas and energysaving industries. PSS Corporation provides Russian and foreign partners with electrics, corrosion protection equipment and antifouling complete systems for shipbuilding industry, offshore and onshore objects, charging stations for electric vehicles. PSS Corporation always ready to technical cooperation with customers, to deliver complete systems and would be glad to share production technologies and to launch the production on abroad relevant producing capacity.