System Operation

The ClearFlo system has been specially developed to:

Control biofouling in seawater lines.
Reduce corrosion of metals in contact with seawater.

Each Wilson Walton ClearFlo system is custom designed for maximum performance, however, it should not be regarded as a panacea to all problems requiring no further attention. A small amount of supervision and maintenance is required and we therefore ask the user to strictly adhere to the instructions on these pages to ensure satisfactory operation.

Background

In the last few decades, marine fouling and seawater-produced corrosion have become major concerns to ship owners and industrialists in the maritime sector. ClearFlo is a single system that solves both problems. With ClearFlo, vessels and industrial facilities can substantially reduce their costs of operation, maintenance and periodic replacement of worn out parts.

The system is fabricated from the most up-to-date and sophisticated electronic components to guarantee precision, safety and robustness.

General Description

ClearFlo is an Impressed Current Cathodic Protection System and Marine Growth Prevention System employing special aluminum, iron and copper alloy anodes for excellent efficiency in combating corrosion and fouling. ClearFlo eliminates marine biofouling and considerably reduces corrosion (by more than 90%) in seawater circulation systems (e.g. sea boxes, grilles, suction scoops, piping, tanks, heat exchangers, condensers, etc.). ClearFlo assures continuous, low maintenance protection and is easily mounted in both new facilities and those already in service.

Incrustation (Marine Fouling) Protection

Overview
The elimination of biofouling is achieved by the use of copper anodes. Electrolytically-generated ions combine with the ions in seawater to form an adverse environment for the survival and growth of larvae and other organisms that may be sucked into lines, thus preventing adherence in areas previously favorable to development.

In Detail
Marine incrustation occurs when certain sedentary organisms, ranging from fungi and bacteria to simple plants and animals, attach themselves to underwater structures and affect their operation and maintenance.

The adhering organisms may alter corrosion processes and block condensers, piping, valves, etc. Biofouling greatly increases frictional resistance, fuel consumption and loss of performance while considerably raising cleaning bills.

Until the introduction of ClearFlo, many methods were tried to combat biofouling, always with undesirable side-effects. Chemical methods produce high intensity localized pitting and considerably increase the risk of contamination. For this reason, the methods called for must be able to inhibit primary incrustation organisms, must be insoluble, must have low pipe pitting aggressiveness and must be compatible with existing equipment without risk of contamination.

ClearFlo easily meets these requirements because it functions through the slow dissolution of special alloy anodes in electrolytic products to create a medium that is hostile to colonization by marine incrustation larvae. Moreover, it considerably reduces corrosion.

Owing to the action of the Impressed Current, the anticorrosion anodes generate aluminum hydroxide (alumina) while the antifouling anodes release copper ions into solution. The aluminum hydroxide maintains the copper ions in suspension and the resultant highly gelatinous compound spreads to the areas of low turbulence in sea boxes where the larvae responsible for incrustation are most likely to adhere. Where Cupronickel piping is fitted, iron anodes are used which deposit an iron film in place of the aluminum hydroxide.

The treatment product concentrates in these areas before penetrating into service lines through the movement of seawater, which acts as a mixing agent: The seawater flow eventually carries the suspension throughout the whole system. Use of ClearFlo means that organisms are carried from inlet to outlet with the assurance that no water is left untreated at any point in the circuit. The absence of biofouling is assured.

Anticorrosion anode action is not limited to the production of a colloidal suspension, as this component also acts as a current-dispersing anode, protecting the structure from the adverse reaction resulting from copper ion deposition. This double ClearFlo system ensures the absence of marine bioincrustation, substantially reduces corrosion, does not cause pitting in pipes, and is also a safe non-contaminant.

Corrosion Protection

Overview
As mentioned above, the dramatic reduction in corrosion is achieved by aluminum, or alternatively iron, anodes. They act as small Impressed Current Cathodic Protection anodes generating ions which suppress the corrosive environment of the internal areas of the sea chest. Aluminum is used when piping material is ferrous, whereas iron is used in all other types of piping systems, such as Cupronickel and aluminum brass.

In Detail
The corrosion of metals is an electrochemical reaction taking place in an electrolyte, in this case seawater, between two electrically coupled zones: an anode and a cathode.

The principle on which the ClearFlo Protection System operates is the introduction into a galvanic circuit of a metal that is more electronegative than the existing anodic and cathodic areas. The protective current needed to convert the cathode structure is obtained by rectifying the on-board alternating current supply. This AC current is fed into a transformer rectifier that supplies continuous DC current to the special alloy anodes.

As described in the previous section, ClearFlo deposits a fine film of gel over the whole inner surface of the cooling system. This film forms a protective, though not thermally insulating, coating throughout the whole system. In practice, the pipes look like their inner surface has been newly painted. This coating acts in unison with the galvanic action to effectively inhibit corrosion in seawater circulation systems.

The Importance of Proper Settings

ClearFlo is designed to give continuous, trouble-free protection against marine biofouling and corrosion with a minimum of maintenance. It will provide full protection throughout anode life, provided that the current through anodes is properly set.

Excess current increases the rate of anode consumption, resulting in reduced anode life and the attendant risk of leaving seawater lines unprotected until new anodes can be installed. Insufficient current allows marine organisms to adhere to surfaces because the adverse environment preventing biofouling cannot be established.

Wilson Walton programs anode output prior to installation using a proven formula that considers:

Flow Rates through pumps
Anode Mass
Desired Anode Life (usually drydock interval)

Pre-programming eliminates the need for adjustments by the user, simplifying system operation and avoiding erroneous modifications that would adversely affect performance.

Should it be determined that a change in anode output is necessary, it can be made by simply exchanging the control modules with modules pre-programmed by Wilson Walton to the new optimal settings. The microprocessor-based control modules ensure against the tendency of analog meters and digital control modules to “drift”, thus eliminating the need for calibration.

Safely Used with Evaporators

If the treated seawater is fed afterwards into evaporators to produce drinking water, the electric current flowing through the anodes at the seawater suction scoop is limited to the point at which the water enters the evaporators. The level of the copper ion concentration is well below the maximum allowable values laid down by the World Health Organization (WHO) and will not contaminate the water.

Maritime Installations

ClearFlo is compatible with a wide range of vessels, offshore platforms, etc. The anodes located in sea boxes treat the water before it is distributed to the plant services. Components receiving protection include sea boxes, tanks, shaft trunks, piping, condensers, heat exchangers, valves, fire pumps, etc. Each ClearFlo system that is installed must therefore be specifically configured for the system and service to be protected. By eliminating marine bioincrustation and corrosion, ClearFlo ensures free circulation of water and the maintenance of initial operating conditions.

ClearFlo is also applicable to coastal facilities that use seawater as a coolant. The main applications are:

Generating plants
Cement works
Paper industry
Marine air conditioning equipment, etc.

Owing to the large number of systems used in industrial seawater circulation circuits, each project must be studied individually to determine the most suitable design.

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