Anti-fouling systems foroffshore and coastal applications

● Electrochlorination● Copper Ion Generation

CathelcoOffshore

Cathelco are technological leaders in anti-fouling systems for marine applicationswith a record of over 10,000 installationson ships, offshore platforms and onshorelocations all over the world. Customersare supported through an internationalnetwork of agents in over 40 countries.

Cathelco specialise in electrochlorinationand copper ion generation and thus offerclients the best solution to their particularrequirements.

With our strong background andknowledge of bio-fouling, we can analyzefouling problems and design the mosteffective system for protection. Ourequipment is also engineered to thehighest standards of quality.

Beyond this, Cathelco can provide furthersupport for customers on corrosionsuppression and cathodic protectionthrough Corrintec, a division specialisingin sub sea pipeline cathodic protectionsurveys, and in the Asia Pacific region byIEV Ltd, the market leader in oceanpowered marine growth controltechnology.

By combining technical innovation withpractical experience, Cathelco offercustom designed solutions which providereliable performance and costeffectiveness.

Systems for offshore andonshore applications

Where seawater is used for coolingpurposes, down-hole injection for themaintenance of oil reservoir pressure orfor fire-fighting systems, bio-fouling canjeopardise the safe and efficient operationof equipment and processes. With theoption of electrochlorination or copper iongeneration, Cathelco can provide themost appropriate form of protection.

Cathelco design and engineer systems forall types of anti-fouling applications,material specifications and site conditions.Factors taken into consideration includespace restrictions, outdoor or indoorinstallations, safe or hazardous areas andhigh or low ambient temperatures.

For offshore applications, anti-foulingsystems are built as complete skid-mounted units with each componentstringently tested prior to assembly, readyfor immediate shipment, installation andcommissioning. Typical offshore

applications are:-

● Production Platforms & FPSO’s

● Drilling Platforms

● Marine Vessels

For onshore installations, Cathelcoexercise the same degree of skill indesign, engineering and projectmanagement, ensuring that anti-foulingsystems are supplied on schedule andoperate with maximum efficiency. Typicalonshore applications are:-

● Petrochemical Refineries

● Desalination/Reverse Osmosis Plants

● Power Stations

● Onshore Cement Plants

● Onshore Smelters

Macro & micro-fouling

Bio-fouling comes in two forms:

Macro-fouling: Barnacles and musselscan gradually restrict seawater flow andreduce the efficiency of cooling systems.In more extreme cases, pipes and valvescan become completely blocked, resultingin shut-down of systems and consequentloss of production time. This can result indamage to equipment and maycompromise standards of safety.

Micro-fouling: Comes in the form of alayer of slime over the surface of heatexchanger plates and tubes and canreduce heat transfer efficiency by asmuch as 25%. It can also acceleratecorrosion and result in a situation wheremaintenance is required more often thanusual with subsequent increases inrunning costs.

In water injection systems, the problem istwo-fold: firstly, the problem associatedwith fouling and secondly, the need for achlorine residual in the seawater to allowfor efficient operation of the dual mediafine filters.

Cathelco – effective solutions tobio-fouling problems

A complete service for anti-fouling ECS and CIGsystems:

● Budgetary estimations

● Detailed design

● Fabrication

● Installation

● Commissioning

● Maintenance

● New or retrofit

With fire fighting systems, which aremainly in a "standby/no flow" condition,anti-fouling at the intake caissons isessential for protection against macro-fouling to avoid blockages.

Electrochlorination

Seawater is electrolysed into sodiumhypochlorite (hypo, also known as"bleach"). It is the preferred chlorinealternative to replace conventionalhazardous chlorine products. Hypo isused to prevent the growth of slime,barnacles, mussels and to destroybacteria (disinfection). Continuous andshock dosing can be administeredintermittently for more effective control.

Benefits

● Effective protection against macro andmicro-fouling (continuous and shockdosing).

● Safe and reliable, also eliminating thehandling and storing of hazardouschlorine based chemicals.

● Ideal to be used as an anti-bacterialagent (disinfection).

● Suitable for offshore installations wherechlorine is required for fine filter (dualmedia) water injection packages.

● Essential to protect seawater intakeson desalination plants as well asproviding chlorine for drinking waterdisinfection.

● Minimum environmental impact(chlorine decomposes back intocommon salt again).

Copper Ion Generation

Copper ions are generated by means ofelectrolysis. Only very smallconcentrations are required to prevent thegrowth of slime, barnacles and mussels.Continuous and shock dosing can beadministered intermittently for moreeffective control.

Benefits

● Effective protection against macro andmicro-fouling.

● Safe and reliable.

● Intermittent dosing provides effectivecontrol against fouling.

● Low impact on the environment isassured by controlled dosing.

● Large caisson mounted units can besupplied to meet specific clientrequirements.

● Small basket mounted units for firepump and other applications.

Electrochlorination Systems (ECS)Cathelco specialise in the design andmanufacturing of electrochlorinators tooffer clients the best solution to theirparticular anti-fouling and disinfectionneeds.

Our electrochlorinators are designed togenerate hypo with the highest chlorineconcentration that is economicallypossible, for example: 2,000 PPM inseawater systems and 8,000 PPM in freshwater + salt systems. This ensures allhypo generation equipment(piping/fittings, hypo storage tanks andhypo dosing pumps) is of a minimum size,thus saving running and maintenancecosts as well as requiring the minimuminstallation space.

Electrochlorinators are also designed foreither safe or hazardous areas, and tomeet all the requirements of the client.

No need for commercialchlorine products

The purpose of electrochlorination is tooffer a safe, economical and independentchlorine alternative to hazardouscommercial chlorine products.Electrochlorination is the only 100% safechlorine technology and is generated:-

● on-site - at the point of application.

● on demand - only when required andalways "fresh", also eliminating bulkstorage.

● using only basic inputs - seawater +electricity, or, fresh water + salt +electricity.

Principles of electrolysis

Salt is composed of sodium and chloride.When direct current is passed through

Consumables and consumption

The generation of sodium hypochloriterequires only: seawater + electricity, or,fresh water + salt + electricity.Consumption, when generating a sodiumhypochlorite solution containing 1kgavailable chlorine is shown in the tablebelow.

SEA WATER SYSTEMS:- 4.2 kWh (AC)- 500 litres sea water(Where hypo @ 2,000 PPM)

FRESH WATER + SALT SYSTEMS:- 5.5 kWh (AC)- 125 litres fresh water- 3.5 kg salt

(Where hypo @ 8,000 PPM)

The electrolyser

The electrolyser consists of anodes andcathodes of solid titanium sheets that arearranged to form multiple cells inside ahorizontal PVC tube/casing. This design iscalled a "plate electrolyser" and is themost popular and most efficient design,representing approx. 95% of allelectrochlorinators world wide. Cathelco isonly offering plate electrolysers. Anodesare coated with Mixed Metal Oxides(MMO) of the platinum group of metals,which is essential for the generation ofchlorine.

Hydrogen and hypo de-gassing tank

Hydrogen is generated duringelectrochlorination. It is an inert by-product and does not participate in theoverall chemical reaction. It is dischargedalong with the hypo into the de-gassingtank where it is safely diluted andremoved using blower fans.

In order to ensure a fail safe operation,dilution air is measured with an air flowmeter and only after the set flow rate isachieved, is a signal sent to the controlpanel to enable the electrochlorinationprocess. Any “dilution air” low flowcondition will activate the emergency shut down system.

The purpose of the hypo de-gassing tankis to:-

● enable the safe dilution and removal ofhydrogen.

● act as a hypo retention tank.

titanium electrodes in seawater or a saltwater solution, the chlorides willdisassociate to form chlorine. The processis basically as follows:

● At the anode - oxidation of chlorideions to produce chlorine.

● At the cathode - reduction of water toproduce caustic soda and hydrogen.

● In the cell - chlorine reacts with thecaustic soda to produce sodiumhypochlorite instantly.

Applications of hypo (chlorine)

Chlorine in the form of hypo, also called"bleach", is a powerful oxidant and ismainly used for:

● anti-fouling to prevent sliming andmussel/barnacle growth.

● disinfection and anti-bacterialpurposes.

● water treatment to oxidise and removeiron and manganese.

Continuous and shock dosing

Continuous and shock dosing are usuallyconsidered for the effective control ofmicro and macro-fouling in sea waterapplications. During continuous dosing, alow chlorine dosing is maintained at alltimes. It provides protection against themajority of bio-fouling. Unfortunatelymacro organisms can become resistant tothis low chlorine dosing and require amuch higher chlorine dosing. Duringshock dosing, a much higher chlorinedosing is applied only for a short time andrepeated at certain fixed intervals. Thisensures complete protection against allmicro and macro-fouling

Cathelco offers a complete range ofdosing strategies to ensure optimum anti-fouling protection at the lowest chlorineusage.

Scaling and de-scaling

All water contains dissolved calcium andmagnesium. Calcium carbonate andmagnesium hydroxide will always depositon the cathode, a process commonlyreferred to as "scaling". It is a universalphenomenon with all electrochlorinators,without exception.

Scale is easily removed by flushing theelectrolyser with 5% diluted hydrochloricacid. The process takes approximately 1 hour and is required after every 10 daysof continuous electrochlorination.

The average down-time is therefore only0.4%. The consumption ofhydrochloric acid is verylow and is re-usedseveral times beforeadditional acid isrequired to restore theacid concentration.

Cathelco is offeringmanual and automaticacid washing systems.

The Flow Process

DC POWERSUPPLY

Transformer& Rectifier

ELECTROLYSER– +

ACIDWASHINGSYSTEM

HYPODEGASSING

TANK

FILTER

100XDILUTED H2

HYPO + H2

OUT

IN

SEAWATERor

FRESH WATER + SALT

BLOWER AIR(2x FANS)

HYPO toDOSINGPUMP(s)

As the result of experience gained overthe last 25 years as technological leadersin copper based anti-fouling systems,Cathelco has developed the Copper IonGenerator for controlling bio-fouling inoffshore oil and gas installations.

Unlike other copper based applications,the key principle of the offshore CopperIon Generator is to produce a relativelyhigh dose of copper ions. This is injectedinto the sea-water lift and fire-fightingcaissons via dedicated dosing lines. Tomaximise the anti-biofouling effect andminimise the environmental impact of the

treatment, the copper dose is applied on adiscontinuous basis.

This provides a level of copper sufficientto prevent the settlement of micro andmacro-fouling, whilst at the same time,due to the dilution effect, minimises thelevel of copper ions which eventually passto the environment.

A further advantage of applying adiscontinuous dose, is to prevent marineorganisms getting resistant to the applieddose. It also results in the most cost-effective way of controlling bio-fouling andminimises the operational costs of theCopper Ion Generation system.

Seawater feed to the skid mountedCopper Ion Generation package isregulated by way of pressure control andemergency shut-down valves with flowcontrol meters. All these systems aredesigned to operate in a "fail safe" mode.

The ion generator operates atatmospheric pressure and the hydrogenproduced as a natural part of theelectrolysis process, is vented to a safearea by way of a "fail safe" hydrogendilution and venting system.

The Copper Ion Generation package canbe designed to operate under "safe" or"hazardous" area conditions, and thecontrol panel unit can be skid mounted orremotely located to suit clientrequirements. The control of the packagecan be by local PLC or via the client’smain control network.

Copper Ion Generation (CIG)

Hydrogen Dilution Fans2 x 100% hydrogen dilutionfans arranged to work inseries, ensuring fail safehydrogen dilution at alltimes.

Thermal FlowSwitchesTwo thermal flowswitches monitor theflow of air in theventing duct to providea fail safe system.

Terminal BoxTo EE’xe’/EE’xd’specification suitablefor hazardous area classification.

ESD & PRVResponsible foremergency shut downand pressure control.All systems designed tooperate in fail safemode

Flow MeterContinuously monitorsflow through package.The electrolysis vesselscan be used eitherindividually oroperating in parallel.

ElectrolysisChamber

ElectrolysisChamber

Cathelco Ltd, Marine House, 18 Hipper Street SouthChesterfield S40 1SS United Kingdom

Telephone +44 1246 207702 Fax +44 1246 206519E-mail: sales@cathelco.co.ukWeb site: www.cathelco.co.uk

International Service NetworkOur international network of sales and service centres can provide immediate advice

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