+2 votes
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Anode Construction and Placement

asked Aug 28, 2014 in Engineering by redonetti (1,280 points)
Anode Construction and Placement on a Tension Leg Platform?

2 Answers

+1 vote
answered Aug 28, 2014 by Normandy (21,040 points) | selected Aug 30, 2014 by odadmin
 
Best answer
  • Anodes should be placed at generally uniform intervals on the surface of the structure to be protected. Consideration in anode placement should be given to compatibility with construction, load out, transportation and installation procedures, and with platform operations, inspection and maintenance requirements.
  • Interference (bucking) between anodes should be considered in anode placement.
  • Anode current output is substantially reduced if parallel anodes are not adequately separated.
  • Anodes should not be located in the splash zone. Anodes should be located with consideration to ROV/diver access for installation, operations, inspection and maintenance activities.
  • Special attention should be mitigated to areas which may be electrically shielded from cathodic protection current due to structure geometry. These include congested areas and inside ballast tanks. Where anodes are located in structurally reinforced areas such as inside ballast tanks, shielding by structural members should be considered.
  • In ballast tanks, consideration should be given to anticipated water levels since anodes are only effective in submerged areas.
  • Anode surfaces should not be located immediately adjacent to structure components constructed of materials that may be susceptible to hydrogen embrittlement, particularly where the structure is not coated.
  • Aluminum anodes should generally be weld-on stand-off type anodes in order to optimize current distribution to the structure to be protected. Use of flush mounted anodes should generally be limited to coated surfaces, and where space limitations and/or clearance requirements restrict the use of stand-off anodes.
  • The back face of all flush mounted anodes should be coated to prevent accumulation of anode corrosion products which can cause detachment of the anode due to pressure buildup behind the anode.
0 votes
answered Aug 28, 2014 by antonjoh (2,870 points)

I thought I want to add the ROV support when placing anodes during fabrication problems after installation and commissioning.

  • “ROV friendly” core configurations should be specified for external hull anodes and at all locations where ROV operations may be conducted.
  • In order to assure uniform anode depletion on each structure component over the system design life, all anodes should be of the same size and shape, except as required for corrosion protection in congested or shielded areas. Anode and core sizing should consider design life, current distribution, manufacturing requirements, attachment, and structural requirements. Doubler plates, gussets, or other means of reinforcement should be used, as required, to ensure structural integrity of the anode attachment over the design life.
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