EnglischaltGeiger Cathodic Protection

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  Geiger Ecotronic Cathodic protection Screening Technology Products & Service  21345 Products & Service Figure 1 Economy in the design of mechanical equipment forwater intakes does not only depend on the right choiceof the machines.For assuring continuous reliableoperation and value preservation,particularly whenthe equipment is installed in aggressive media,it ishighly recommendable to supplement careful andregular maintenance by a special plant protectionsystem.Cathodic corrosion protection is the mostefficient method of protecting steel and other heavymetals being installed in conductive media againstnatural corrosion.Its technology is firmly associatedwith the name of Geiger as for more than 30 years wehave been developing cathodic protection systems.These systems are patented and are installed inapprox.100 large-scale plants operating successfully. Reason for corrosion The reason for corroded metal surfaces – especiallysteel surfaces – is of electrical srcin.Between themetal parts and the surrounding electrolyte (water)there are electric circuits of differing extents.At the current emitting end of the anode,the metalis consumed according to Faraday’s laws of electrolysis(see figure 1).The driving voltage of these corrosioncurrents either comes from the different compositionof the metal surface itself (local element formation)or from the co-operation with another metal surfacewhen galvanic elements are formed between thedifferent metals,together with the electrolyte,accor-ding to the electrochemical series. Corrosion control The corrosion current and,thus,corrosion itself canbe reduced or even totally eliminated by insulation orby protective direct current of reversed polarity.The purpose of the protection current principle isnot only to prevent uncoated parts from corrosion,butespecially to protect bare spots on coated surfacesagainst damages due to corrosion.Because even thebest surface coating cannot ensure absolute insulationwhen being submerged for a long time. Function of the Cathodic Corrosion Protection(see Figure 2 and 3) The objects to be protected are connected by meansof metal strips or stainless steel ropes and – thus asone metal unit – connected with a cable to the negativeconnecting terminal of a rectifier.The submergedtitanium or niobium anodes are connected to thepositive terminal.According to the rules of spreadingof current in wide spaces,the current reaches practicallyall parts of the surfaces of the objects to be protected(except very small gaps),which are in contact withthe conductive water,and returns to the rectifier viathe cathode cable.The protective current penetratesthe objects to be protected and causes the followingeffects by modifying the potential ratio:ã Decrease or elimination of anodic corrosionã Reduction of oxygenã Increase of the pH valueã Formation of covering layers 43212 1 Dissolving iron ions (oxidation)2 Cathodic reaction by free oxygen (reduction)3 Ion flow in the electrolyte4 Electron flow in iron1 Impressed current anode2 Cathodic reaction on the whole iron surface3 Ion flow in the electrolyte4 Electron flow in iron5 Direct current supply unitCorrosion Element in an Electrolyte (SeaWater):Crevice Corrosion on an Iron SurfacePrinciple of Electrical Cathodic Protection withImpressed Current Anodes – Crevice Corrosion is Avoided.  Figure 3:Scheme of the Cathodic Corrosion Protection System for aTravelling Band Screen in a cooling water intake 1 2384756 1 Potential regulator KS 982 Ecotronic direct current supply ES013 Protective anode4 Reference measuring electrode5 Return wire for reference measurement6 Mass connection elements7 Travelling Band Screen8 Isolating equipment 1   1234567981010101011 12 1311 12 1311 12 1311 12 13 Direct current supply(principle)Object to be protected(scheme) Referencemeasuringpoint1Referencemeasuringpoint2Referencemeasuringpoint3Anode 1Anode 2Anode 3Anode 4Outputof measured valuecase history for evaluation withExcelOutput of warning-alarmand fault messagespotential-free 1 Supply line2 Control panel3 Main switch4 Protection device5 Transformer6 Rectifier7 Control device with processor8 Multifunctional display9 Push-button station10Direct current supply modules11 Single current meter12 Pre-setting potentiometer13 Three LED signals:operation,anode current,fault The Cathodic Corrosion Protection Systems aredimensioned by means of special optimisation soft-ware developed by Geiger. The components of Ecotronic (see Figure 2) ã Multifunctional potential regulator with trenddisplayand reportingsystemã Ecotronic direct current supply modules ES01,10 A,with analogue display of the protective current,potentiometer for the pre-setting of the protectivecurrent and logic signalling systemã Protective anodes,design depending on the field of applicationã Reference measuring electrodesã Mass connection elementsã Mobile reference measuring device for occasionalcontrol measurements Geiger Ecotronic – Reliable corrosion protection incooling water intakes Cooling water supply in power stations is among themost sensible tasks in mechanical water treatment.Desalination and other kinds of industrial plants,too,need to rely on a trouble-free operation of theirwaterintakes.Inabout 100large-scale plants all over theworld,Geiger Ecotronic corrosion protection systemscontribute considerably to assuring the availability of plants and systems.Versatile in its Application –Scheme of a Control System (Figure 2)  Passavant-Geiger GmbH Business Unit Geiger Hardeckstrasse 376185 Karlsruhe,GermanyPhone: +49 721 5001 - 0Telefax: +49 721 5001 - Advantages >  Multifunctional digital display >  Current supply units with protective current display andlogical signalling system >  Recognition of different materials >  Automatic measurement of the disadvantage potential >  Plausibility control >  Storage of measured value case history and interface fordata analysis >  Special anodes for guidings and chains >  Modular system >  Simple handling >  Easy servicing      T     h    e     t    e    c     h    n     i    c    a     l     d    a     t    a    s     t    a     t    e     d     i    n     t     h     i    s     b    r    o    c     h    u    r    e    a    r    e     i    n     d     i    c    a     t     i    v    e    o    n     l    y    a    n     d     h    a    v    e     t    o     b    e     d    e     t    e    r    m     i    n    e     d     f    o    r    e    a    c     h     i    n     d     i    v     i     d    u    a     l    c    a    s    e .
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