bmoorthy
Mechanical
- May 29, 2003
- 457
Hello All
Recently i came accross a user specification for Sub Sea Pipe Line when there was a statement that was perplexing. I could be very wrong as am not a corrosion expert, hence this question.
The specification calls for various tests for Carbon steel line pipe and the same specification is also applicable for cladded Pipe (Cladded on the inside with Incolloy 825). The longitudincal joint are welded with Carbonsteel electrode (In the carbon steel Portion) and in the inside the clad is restored with ER NI Cr Mo-3.
Some of the Girth seams are welded with CS electrodes and clad restored from inside where as some joints are welded fully with Er Ni Cr Mo-3.
Where as there are some additional requirements for Carbon steel (Uncladed) pipes and some different additional requiremtns for Claded pipe line, many of the requirments are common.
The Pipe Line is essentially Carbon steel Pipe line and in some unpiggable portion of the pipe line the pipe line is Cladded.
Amongts the EXCLUSIONS for the claded pipe there is one notable exclusion that is Galvanic Corrosion test.
This Galvanic Corrosion test is called for in the CS pipe and is excluded for (Internally) Cladded pipe)
The whole pipe line system is protected with Sacrificial brace let anode (Frequency and distribution of Anodes are as per DNV RP 103 and DNV RP 401.
It is my understanding that the galvanic corrosion occurs because of Contact of two different material in the presence of electrolyte, in this case the electrolyte being sea water, what could be rationale for excluding the galvanic corrosion test from cladded pipe weld ment specification?
Recently i came accross a user specification for Sub Sea Pipe Line when there was a statement that was perplexing. I could be very wrong as am not a corrosion expert, hence this question.
The specification calls for various tests for Carbon steel line pipe and the same specification is also applicable for cladded Pipe (Cladded on the inside with Incolloy 825). The longitudincal joint are welded with Carbonsteel electrode (In the carbon steel Portion) and in the inside the clad is restored with ER NI Cr Mo-3.
Some of the Girth seams are welded with CS electrodes and clad restored from inside where as some joints are welded fully with Er Ni Cr Mo-3.
Where as there are some additional requirements for Carbon steel (Uncladed) pipes and some different additional requiremtns for Claded pipe line, many of the requirments are common.
The Pipe Line is essentially Carbon steel Pipe line and in some unpiggable portion of the pipe line the pipe line is Cladded.
Amongts the EXCLUSIONS for the claded pipe there is one notable exclusion that is Galvanic Corrosion test.
This Galvanic Corrosion test is called for in the CS pipe and is excluded for (Internally) Cladded pipe)
The whole pipe line system is protected with Sacrificial brace let anode (Frequency and distribution of Anodes are as per DNV RP 103 and DNV RP 401.
It is my understanding that the galvanic corrosion occurs because of Contact of two different material in the presence of electrolyte, in this case the electrolyte being sea water, what could be rationale for excluding the galvanic corrosion test from cladded pipe weld ment specification?
