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
Pipeline installation date (year).
Pipeline length & size.
Pipeline ambient temperature.
Hot section & the respective temperature.
Type of pipeline coatings.
Check for concrete coatings.
Original anode type, dimensions, weight, spacing etc.
Check the underwater ROV Survey Reports on the pipeline for:
Video log - to spot the anodes
Pipe Potentials – by ROV
Current Output – calculate through the field gradient (FG) measured by ROV.
Computed anode remaining life.
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
Type: Galvalum III or equivalent
Current capacity: 2500 A.Hr/kg
Dimension: 1100 mm (L) x 225mm (W) x 200 mm (H)
Utilisation: 0.8
Anodes sled
Type: Galvalum III or equivalent
Size: 2000 mm x 2000 mm (75mm x 9mm flat core)
No. of anodes per sled : 4 (four)
Total Anode Weight per sled : 524 kg (in air)
Estimated Total Sled Weight : 1000-1200 kg
Typical anode sled
Basic concepts for anode sled design
Stand anode weight.
Maintain anodes at best operation conditions (e.g. in seawater).
Stable, stationary underwater.
Save space in the loading/working barge (e.g. can stack).
Easy/quick underwater installation to reduce cost.
