Pipelaying Tender-VOL II - WorleyParsons.com

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PageEPMC SERVICES FOR REWARI – KANPUR PIPELINE PROJECTBASIS OF DESIGN (PIPELINE)5.10.3 Corrosion Coating – Joints, Bends and FittingsA suitable joint coating system compatible with the primary coating system shall be selected such asan epoxy primed 3 layer heat shrink sleeves (HSS), e.g. DIN EN C HT (60) UVIt is essential that the joint coatings are fully compatible with the linepipe coating and have a goodbond to it. They should have the same performance as the linepipe coating in their protection of thesteel, resistance to cathodic disbonding, and resistance to mechanical damage.A suitable coating system compatible with the primary coating system shall be selected for hot formedbends, fittings and buried valves.5.10.4 Cathodic ProtectionImpressed Current Cathodic Protection (ICCP)The pipeline shall be protected by ICCP systems located at the pump stations, Intermediate stationreceiving stations and selected sectionalising valve (SV) stations. Power supply shall be from thestation power supplies.Design of the CP system shall be in accordance with the following principles:• The design life for permanent impressed current ground beds is 35 years at maximum currentoutput. The actual life will be a function of ground bed operating current output. The designlife for temporary sacrificial anode ground beds is 2 years. Other CP system componentsshall be designed to conform to the pipeline facilities design life.• Inline insulating joints shall be installed in the pipeline at pump stations between the pipelineand each offtake and at selected SV’s, wherever ICCP stations are installed, to break thepipeline into separate electrical entities. The ICCP system shall be optimally designed so asto minimise insulating joints at SV’s.• Generally ICCP systems shall be installed at the start and end of the pipeline, at each end ofthe electrically separate pipeline sections and at selected locations between these sections.• Except for the start and end of the pipeline, and selected locations between the ends ofelectrically separate pipeline sections, the impressed current system shall be based on dualoutputconstant potential CP units, one output powering the upstream pipeline and one outputpowering the downstream pipeline.• At the start and end of the pipeline and selected locations between the ends of electricallyseparate pipeline sections, only one CP unit shall be installed.• Sufficiently short electrically separate pipeline sections shall be protected from one end,should design calculations show that this may be achieved.n:\513-mh-2145-rkpl\11 engineering\11.8 pipelines\02 bod\working\mh2145-c000-pl-bod-0001_rev 0 .doc EV435-JH0902-00-GEN-BOD-0001 Rev 023 of 34
PageEPMC SERVICES FOR REWARI – KANPUR PIPELINE PROJECTBASIS OF DESIGN (PIPELINE)• The requirement for CP systems between the ends of electrically separate pipeline sectionsshall be based on the findings of soil resistivity testing and an assessment of the risks posedby telluric and stray currents.• The location of all other CP systems at pump and SV stations shall be subject to the findingsof detailed soil resistivity testing at these sites. If deepwell groundbeds are required, resistivitydata shall be obtained from exploratory boreholes or site resistivity testing.• The output current and pipeline potential from each CP unit shall be monitored by the pipelinecontrol system and displayed in the Pipeline Control Centre. Each CP unit shall be capableof operating in constant CP potential, constant current, or constant voltage mode.• Unless design studies show there is to be no requirement, CP units shall be sized andspaced so that should an adjacent unit fail, the neighbouring units shall be able to provideprotection as far as the failed unit until such time that the failed unit is restored to service.• The CP groundbeds shall be installed as either shallow horizontal beds or as deepwellboreholes so that the anodes are located in soil with a uniform resistivity throughout the year.A single suitably sized ICCP groundbed shall be installed at both single and dual ICCP stationlocations. Groundbed sites will satisfy the criteria below:- Average soil resistivities will typically be less than 10,000Ω.cm.- Sites for shallow, horizontal groundbeds will be approximately 200m perpendicularlydistant from the pipelines.- Sites will be remote from foreign metallic structures, such as buried pipelines, and willnot be situated between foreign metallic structures and the pipelines.- Sites will not be located in areas that are at obvious risk of disturbance, vandalism andtheft.• Provision shall be made to comply with the cathodic protection regulations which are in forceat the time of design:The design for the CP current demand is based on the following parameters:• The pipeline current density on the pipeline at the current injection point, shall not exceed four(4) times the current density at the least protected location, and• The minimum current density required for protection shall be 6.0μA/m 2 .• The casing pipes shall be cathodically protected.• Anodes for casing piping shall be provided if other methods of corrosion mitigation are notpossible for the given condition.Temporary Cathodic Protection (TCP)TCP shall be provided principally by magnesium ribbon anodes.n:\513-mh-2145-rkpl\11 engineering\11.8 pipelines\02 bod\working\mh2145-c000-pl-bod-0001_rev 0 .doc EV435-JH0902-00-GEN-BOD-0001 Rev 024 of 34
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Pipelaying Tender-VOL II - WorleyParsons.com

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