1、ICCP Hull Corrosion Protection SystemsPitting corrosion around exhaust discharge. General corrosion on hull plate.Corrosion around bow thruster. Corrosion blisters on hull plate.Background image Corrosion on propeller shaft bracket armThe Problem of CorrosionCorrosion takes many forms in the marine
2、environment. It can be seen as pitting on hull plates; in the disintegration of weld seams; around bow thrusters and on the surfaces of rudders and other vital components.A well designed ICCP system can eliminate these problems, safeguarding the structural integrity of the vessel and significantly r
3、educing maintenance costs throughout its operational life.By installing a Cathelco system you can have the advantage of world leading ICCP technology combined with the expertise which goes with wide understanding of corrosion problems and the most effective way of solving them.Cathelco C-Shield impr
4、essed current cathodic protection (ICCP) systems have now been fitted to more than 10,000 vessels around the world, establishing a record of effective performance and reliability on ships of every type:- Cruise Ships Container Vessels VLCCs Ferries FPSOs Ice Class VesselsCathelco have recently intro
5、duced C-Max anodes, a new range of linear and disc anodes which combine high performance with a number of features to simplify installation.The most important feature is that they are diver changeable enabling them to be replaced without drydocking. The linear anodes are exceptionally lightweight an
6、d can be easily carried by one man. They are fitted using self-snapping torque nuts to speed up installation.Other developments have included the introduction of ICCP systems which are specifically designed to protect bow and stern thruster tunnels. Alongside this has gone the design of more sophist
7、icated shaft earthing systems and rudder bonding equipment to provide reliable protection for propulsion and steering systems on todays vessels.In the case of smaller vessels, the Minitek and Alutek systems are compactly designed to protect steel and aluminium hulls, respectively.Cathelco serves cus
8、tomers globally through a well established network of over 40 agents who can provide on-the-spot access to technical advice and commercial support.Following a series of takeovers, Cathelco incorporates the following product ranges:- Cathelco Corrintec Jotun Morgan Berkeley Wilson Taylor F.A.HughesCa
9、thelco ICCP systems for vessels of every typeRUDDER BONDINGREFERENCE ELECTRODEC-MAX LINEAR ANODEREMOTE MONITORING UNITSHAFT EARTHING ASSEMBLYCONTROL PANEL50-75A & 100A Linear AnodesDesigned with a single current emitting element either 25 or 32mm diameter, these anodes are exceptionally lightweight
10、and versatile.Size: 740mm x 400mm Weight: 7 Kg125-200A Linear AnodesProduced with two 32mm diameter elements these high performance anodes are easy to install.Size: 740mm x 400mm Weight: 7 Kg225-300A Linear AnodesDesigned for the largest vessels, these anodes have three elements to produce outputs o
11、f up to 300A.Size: 1380mm x 400mm Weight: 14kgImpressed Current Cathodic Protection SystemsREFERENCE ELECTRODECONTROL PANELC-MAX DISC ANODEREFERENCE ELECTRODEDisc AnodesGenerally used on forward systems, these are produced in two sizes:-50-100A. Size 370mm diameter. Weight: 4kg125-175A. Size 526mm d
12、iameter. Weight 9kgReference ElectrodesCathelco zinc reference electrodes are fully diver changeable. They are also available with silver/silver chloride elements.Size: 125mm diameter Weight: 9kgMost operators recognise the need to combine modern hull coatings with a purpose designed impressed curre
13、nt cathodic protection system. The C-Shield system suppresses corrosion on the wetted surface of the hull using an arrangement of hull mounted anodes and reference electrodes connected to a control panel. This neutralises corrosion cells and eliminates problems that arise through dissimilar metals a
14、nd the proximity of components such as propellers.Impressed Current Cathodic Protection SystemsHow ICCP systems operateThe most important feature of an ICCP system is that it automatically detects the electrical potential at the hull/seawater interface and raises or lowers the output to the anodes a
15、ccordingly. In this way, the ship receives the optimum level of protection at all times.The electrical potential is monitored by reference electrodes which are fitted port and starboard between the anodes where the lowest potential is likely to occur. This reading is fed back to the control panel wh
16、ich automatically adjusts the anode output.On larger installations, above 350 amps, thyristor control panels are generally used which provide a low voltage controlled and rectified d.c. power source to the anodes. On smaller installations, Cathelco provide modular control panels with computerised el
17、ectronics with the advantages of space and weight savings.The new generation of C-Max anodes are available in linear and disc designs with outputs from 50 to 300 amps covering the requirements of all types of vessels from small ferries to the largest VLCCs and container ships.The linear anode elemen
18、ts are produced from titanium with a coating of mixed metal oxide. They are mounted on an integral backing shield made from strong, but lightweight ABS plastic. The design ensures a streamlined flow over the hull with minimal weight and drag. The electrical connection is made with a single rod, simp
19、lifying replacement by a diver.Disc anodes, generally used for forward installations, are also diver changeable. This is made possible through a unique cofferdam design which enables the disc anode to be easily removed with the assistance of an on-board technician.It is also essential to bring the s
20、haft and rudder within the scope of the system using shaft earthing and rudder bonding equipment which is described on page 9.ICCP Linear AnodesDouble headed self torquing snap nut on stud.Nut is tightened using ordinary wrench. Top section breaks off when correct torque is achieved.The lower head a
21、llows the anode to be removed when replacement is necessary.321Faster and more reliable installation with self-torquing snap nutsSmaller footprint fewer fixingsC-Max anodes have been developed by Cathelco to combine maximum performance with numerous features which speed-up installation. The advanced
22、 design means they are exceptionally lightweight and can be easily carried by one man. They also have a small footprint which means that fewer fixings are required, reducing installation time. Diver changeability is another key feature enabling them to be replaced without the need for drydocking.Sel
23、f torquing snap-nuts save time and effortOne of the most important advances with C-Max anodes is the use of self-snapping torque nuts. When the correct torque is achieved using an ordinary wrench, the top section of the nut snaps off leaving the lower section intact for future use. No torque wrenche
24、s are required, greatly reducing the time and effort taken by divers when anodes are changed at sea. In addition, the nuts are yellow for increased visibility underwater.Another advantage is that the plastic fixing nuts have a rubber sleeve which allows for minor discrepancies in the weld area surro
25、unding the stud. Once tightened, they create a sealed environment around the stud which avoids the risk of stray current damage.The electrical connection is made through a single connecting rod which simplifies the task for the diver at installation and when the anode needs to be changed.Rigorous te
26、st protocolsThe stability of C-Max anodes has been modelled using computerised fluid dynamic (CFD) techniques. This focuses on the effects caused by the velocity of the seawater passing over the hull surface and the pressure exerted on the anode by the moving water.Velocity plot at back board surfac
27、e +30mm The image illustrates the flow dynamics of the anode, showing a streamlined profile with minimal turbulence as the water flows over the surface making the anode inherently stable.Pressure plot at anode back board surfaceThe green areas indicate that there is positive pressure across the fron
28、t surface of the anode. The pressure prevents the anode from flexing as the ship moves forward.Designed to be easily diver changeableEasier installation higher performanceC-Max disc anodes are generally used for forward ICCP systems where their circular shape reduces the risk of physical damage and
29、helps to maintain the flow dynamics at the bow of the vessel. Their low profile also avoids the problem of rubbing by anchor chains. The current emitting face of the C-Max disc anode is made from mixed metal oxide (MMO) on a titanium substrate. This is contained within a rubber over-moulding which c
30、reates a watertight seal with the hull and protects the edge of the anode.Special diver change toolThe C-Max disc anode has been designed to be easily changed by a diver with the assistance of a shipboard technician. Working from the inside of the ship, the first step is to unscrew the cofferdam bol
31、ts, then remove the gland assembly and disconnect the wiring. The blanking plug is removed from the cofferdam cover and used to seal the side pipe exist boss.The cofferdam lid is then put back into position and the special diver change tool is screwed into place. As the handle is turned, the barrel
32、presses on the anode stud and pushes the anode away from the outside surface of the hull.The diver lifts the old anode away and replaces it with the new one. Water pressure pushes the new anode against the hull enabling the studs to be located in the cofferdam.The diver change tool is removed allowi
33、ng any remaining water to drain from the cofferdam. At this point the cofferdam lid can be removed and the anode bolted in place. All that remains is to remake the electrical connections and replace the cofferdam lid.ICCP Disc AnodesPicture showing blanking plug in cofferdam cover.Blanking plug used
34、 to seal the boss exit.Special diver change tool is screwed in place. Handle is turned to push anode away from exterior hull surface.321A choice of control panelsThyristor PanelsC-Shield thyristor control panels combine cost effectiveness with rugged reliability that has been proved on vessels of al
35、l sizes worldwide. They also incorporate the latest computerised information systems enabling the status of the ICCP system to be monitored by ships computers.Thyristor control panels can be used for systems of up to 1,000 amps with 8 anodes and 4 reference electrodes being controlled by an individu
36、al panel. They are ideal for the requirements of cruise ships, VLCCs and many types of container and cargo vessels.The popularity of these panels means that they can generally supplied within relatively short lead times. For ICCP systems of up to 1,000 amps. Reliable performance with minimum attenti
37、on. Economical control for systems of all sizes. Combines computerised output displays, alarms and information systems. Up to 8 anodes and 4 reference electrodes per panel. Easily configured to clients requirements.Modular PanelsThe C-Shield modular control panel, based on advanced computerised elec
38、tronics, is designed for installations of up to 350 amps.Extremely lightweight and compact in design, it can be easily installed in engine rooms and requires the minimum of attention from the crew.One of the major advantages of the unit is that the modules are interchangeable and can be quickly remo
39、ved and replaced if necessary, thereby offering greater reliability. For ICCP systems of up to 350 amps. Modular design for greater reliability and flexibility. Extremely lightweight and compact. Clear digital output displays. Incorporates under and over protection alarms Can be linked to bridge inf
40、ormation systemsMinitek PanelsThe Minitek system has been designed to protect smaller steel hulled vessels against corrosion. It has been widely installed on tugs, fishing vessels and workboats where engine room space is at a premium. Operates from 230V a.c. electrical supply. Control panel measures
41、 600mm x 600mm x 210mm Far superior to sacrificial anode systems where output cannot be verified.Alutek PanelsThe Alutek system provides carefully controlled protection for aluminium hulls using an arrangement of flush mounted anodes, monitoring electrodes, controlling electrodes and di-electric shi
42、eld sensors. Operates from 230V or 115V a.c. electrical supply. Control panel measures 400mm x 500mm x 210mm. Lower yard installation cost than recessed sacrificial anode systemsCurrent FlowHull AnodeEarthing CableBrush HolderBrushSilver Inlay TrackStern SealCathelco Shaft Earthing ArrangementSlip R
43、ing assemblyBearingsGear BoxPropulsion System Manufacturers Shaft Earthing Arrangement(if supplied)Shaft EarthingPropeller shaft potential monitoringCathelco supply compact millivolt meters to monitor the potential between the shaft and the hull and verify the effectiveness of the system. The meters
44、 can be located in a convenient position for monitoring by the crew.Even on ships fitted with ICCP or sacrificial anode systems, propeller shaft bearings are vulnerable to corrosion.This is because turning propeller shafts are electrically insulated from the hull by the lubricating oil film in the b
45、earings and by the use of non-metallic bearing materials in the tail shaft.The problem can be eliminated if the shaft is earthed to the hull using a propeller shaft slipring. Cathelco supply complete shaft earthing assemblies consisting of a pair of high silver content/graphite compound brushes moun
46、ted in a balanced brush holder, running on a copper slipring with a solid silver inlay track. This combination has been proved to give the optimum electrical continuity. The number of brushes depends on the size of the vessel. Smaller craft have a single brush holder.InstallationThe shaft slipring i
47、s supplied as two matched halves, complete with band and clamping arrangement and can be readily installed by competent engineering personnel.The balanced brush holder is supplied ready for fitting to a shipyard-supplied 20mm diameter rod and mounting bracket.Each brush holder has an adjustable tens
48、ioner to ensure good electrical contact and maximum brush utilisation.Bow and stern thruster protection is a specialised area where Cathelco have developed a system which is uniquely effective in providing corrosion protection.Problems of corrosion arise because of the dissimilarity of the materials
49、 used in the hull and thruster tunnel construction and remain unchecked because they are outside the scope of conventional ICCP systems.Cathelcos thruster tunnel systems are installed on ocean going vessels, harbour tugs and in offshore oil and gas applications. The equipment consists of a power unit/controller and an arrangement of reference electrodes and anodes positioned on either side of the tunnel. The anodes and reference electrodes are flush mounted to maintain the optimum performance of the thrusters and reduce the effects of
