Cathodic Protection Retrofit System

Introduction to CP Retrofit System

CP (Cathodic protection) retrofit system is a system that is used
  • to extend the service life of a structure

  • when cathodic protection is becoming insufficient and when there are “hot spots” on a structure which need special treatment

  • when the depletion of cathodic protection is faster than originally anticipated

  • when cathodic protection is becoming insufficient

CP Retrofit Can Be Carried Out On
  • Onshore and offshore pipelines

  • Jetty piles

  • Sheet piles

  • Offshore jackets

  • Tank bottoms

  • Plant's underground structures

Retrofit Anode Sacrificial Magnesium System

Retrofit Anode Impressed Current System

Retrofit Anode Impressed Current System

Retrofit Anode Sacrificial Aluminium System

Typical example of cathodic protection retrofitting : pipeline case

  1. Pipeline installation date (year).

  2. Pipeline length & size.

  3. Pipeline ambient temperature.

  4. Hot section & the respective temperature.

  5. Type of pipeline coatings.

  6. Check for concrete coatings.

  7. Original anode type, dimensions, weight, spacing etc.

  8. Check the underwater ROV Survey Reports on the pipeline for:

  9. Video log - to spot the anodes

  10. Pipe Potentials – by ROV

  11. Current Output – calculate through the field gradient (FG) measured by ROV.

  12. Computed anode remaining life.

  13. Comments on the anode depletion percentage eg: 25-50%, 50-75%, 0-25%, 75-100% .

What input needed for evaluating the remaining pipeline anodes?

Typical examples of anode & sled dimension

Anodes specification
  1. Type: Galvalum III or equivalent

  2. Current capacity: 2500 A.Hr/kg

  3. Dimension: 1100 mm (L) x 225mm (W) x 200 mm (H)

  4. Utilisation: 0.8

Anodes sled
  1. Type: Galvalum III or equivalent

  2. Size: 2000 mm x 2000 mm (75mm x 9mm flat core)

  3. No. of anodes per sled : 4 (four)

  4. Total Anode Weight per sled : 524 kg (in air)

  5. Estimated Total Sled Weight : 1000-1200 kg

Typical anode sled

Basic concepts for anode sled design
  1. Stand anode weight.

  2. Maintain anodes at best operation conditions (e.g. in seawater).

  3. Stable, stationary underwater.

  4. Save space in the loading/working barge (e.g. can stack).

  5. Easy/quick underwater installation to reduce cost.

Typical anode sled

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