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HOUSTON, TEXAS 1

Corrosion Control and Monitoring

ENGINEERING SERVICES LP

HOUSTON, TEXAS

Engineering Specification

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Corrosion Control & Monitoring

SCOPE– This Engineering Specification includes

external and internal corrosion control and monitoring for DOT regulated pipelines.

– Design, construction, construction inspection, construction acceptance, operation, and maintenance of DOT regulated pipelines are covered by this Engineering Specification.

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Corrosion Control &Monitoring

GENERAL– All DOT regulated LCCC pipelines require

protection from the environment.– Corrosive elements in the pipeline stream must

be neutralized or the pipe material must be resistant to the stream.

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Minimum requirements for corrosion control:– External Corrosion Control

» Buried DOT regulated pipelines will be coated and cathodically protected

– Internal Corrosion Control» Known corrosion rate based on historical data

» Corrosion rate from a national standard data base

» Data collected from laboratory prototype testing

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Minimum requirements for corrosion control (Continued):– Above Ground External Corrosion Control

» Coat with an approved system with resistance to the soil and internal fluid temperature

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REFERENCES– NACE RP 0169-92– Surface Preparation:

» NACE No. 1, SSPC-SP 5, White Metal Blast Cleaning

» NACE No. 2, SSPC-SP 10, Near White Metal Blast

» NACE No. 3, SSPC-SP6, Commercial Blast

» NACE No. 4, SSPC-SP 7, Brush-Off Blast

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PERSONNEL REQUIREMENTS– Engineering design will be performed by a

Corrosion Engineer with training and experience in the proposed corrosion control system.

– Coating, lining, and painting inspection will be performed by an inspector with appropriate training and experience.

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PERSONNEL REQUIREMENTS (Cont..)– Cathodic protection installations will be

inspected by an inspector with training and experience in cathodic protection inspection.

– Internal corrosion monitoring installations will be inspected by an inspector with training and experience in internal corrosion monitoring inspection.

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DESIGN REQUIREMENTS, EXTERNAL– Cathodic Protection Criteria

» Buried Onshore Pipelines: Pipe-to-soil potential equal to or more negative than -0.85 volts referenced to copper-copper sulfate electrode and recorded immediately after current interruption (Instant-off potential).

» Offshore Pipelines: Pipe-to-water potential equal to or more negative than -0.80 volts referenced to a silver-silver chloride electrode with “instant off” potential reading.

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» Tank Bottoms: Steel-to-soil potential equal to or more negative than -0.85 volts with a copper-copper sulfate half cell and “instant off” potential.

» Maximum pipeline potential: Equal to or less than -1.5 volts to a standard copper-copper sulfate half cell with the current temporarily interrupted.

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– Coating Requirements» New buried pipe sections shall be coated with one

of the following types: Fusion bonded epoxy Coal tar epoxy Polyolefin tape Prefabricated films Other coating systems approved by Central Engineering

» Surface preparation shall be in accordance with manufacturer’s recommendation and Appendix B.

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Methods Used for Cathodic Protection– Galvanic Anode Systems

» Provide protection to the structure by the potential difference generated by the electrochemical reaction between the structure and the anode through a soil or water electrolyte.

» Typically used in soil or water with resistivity less than 5000 ohm-cm.

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– Methods Used For Cathodic Protection (Cont)» Impressed Current Systems

Uses external source of DC power, usually an AC trans-former with an AC to DC rectifier, to provide the driving voltage to the structure to be protected.

Potential difference between the anode and the structure creates current flow from the anode into the soil and onto the pipeline.

Used when the soil resistivity exceeds 5000 ohm-cm and/or more than 5 amperes of impressed current are required.

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– Equipment» Galvanic Anode Systems

Anode: Magnesium onshore, Galvalum III offshore. Junction box to connect leads from structure and anode.

» Impressed Current Systems DC transformer/rectifier (supplied as a unit). Anode(s) with inert or low reactivity characteristics. Terminal box with resistors to adjust current flow to each

anode or anode string.

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– Miscellaneous» Install lightning arrestors.

» Provide electrical isolation: Insulating flanges or spools.

» Minimize interference with bonding stations.

» Install test stations to measure potentials.

» Complete the following documentation: Bonding and/or anode bed data sheet. Bonding station data sheet. Test station data sheet.

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– Impact on Operating Equipment» Apply NEMA electrical-class safety requirements to

all equipment associated with impressed current installations.

» Install CP equipment in areas not requiring intrinsically safe design.

» Locate anode beds to minimize effect on other structures and to minimize mechanical damage from foreign construction.

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» Perform interference testing on all equipment that may be damaged by the new CP installation. Testing shall include, but is not limited to, the following situations:

Pipelines crossing within 5 feet. Metal Structures within 5 feet of the pipeline. Metal Structures within 200 feet of the anode bed.

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– Impact on Operating Equipment» Design CP systems with capacity for current loss

through interference bonds and future current loss due to coating deterioration.

» Minimize casing installations for protection of the carrier pipe. Perform interference testing as shown in Company Corrosion Control & Monitoring Specification Appendix E. Provide bonding stations for each casing installation.

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DESIGN REQUIREMENTS, INTERNAL– Corrosive chemicals in the pipeline stream

» May reduce stream (liquid or gas) quality or

» Cause general thinning or pitting attack

» Shall be handled by one of the following methods: Neutralization or removal of the corrosive chemicals. Select a pipe material which is resistant. Coat the internal surfaces of the pipe.

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– Design package will contain:» Provisions for upset/emergency conditions.

» Recommended corrosion monitoring program.

» Recommended corrosion monitoring equipment.

» Installation of personnel safety devices and platforms required for safe performance of duties.

» Pigging procedure when pigging facilities are included in the design package.

» Compliance with regulations of local, state, and federal jurisdiction for pigging procedures.

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– Documentation Requirements» Determine thickness measurement locations (TML’s)

based on the most probable locations for corrosion or erosion-corrosion damage. Select TML’s with the assistance of the Corrosion Engineer.

» Collect baseline thickness readings on all new installations.

» Install corrosion monitoring equipment where the “worst case” corrosion attack is expected.

» Provide corrosion monitoring data sheets.

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DESIGN REQUIREMENTS, ABOVE GROUND EXTERNAL– Coat with a coating system that is recom-

mended for the environment.– Prepare surface in accordance with external-

coating-system manufacturer’s recommendations. See Company Corrosion Control & Monitoring Specification Appendix B.

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INSTALLATION– Quality Control, External Systems

» Coatings Qualified Inspector presence - 100%. Field applied coating systems - 100% inspection. Shop applied coating systems - 100% inspection. Coating repairs - 100% inspection. Protect all stored coating materials at the construction site

from weather, particularly directly sunlight and heat.

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Corrosion Control & Monitoring» Pad in the pipe trench

Inspect just prior to laying the pipe in the trench. Remove all trash and construction debris.

» Cables Inspect upon receipt at job site to detect nicks and damage. 100% inspection at the mill with proper mill cert.. Avoid damaging cable insulation during installation. Splice cables aboveground in terminal boxes. Use non-conductive conduits for cable installation. Make cathode cable connections aboveground, if possible. Repair buried connection in accordance with the original coating

manufacturer’s recommendations.

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– Transformer/Rectifier Systems» Install by a qualified electrician.

» Test rectifier at maximum design load to assure the DC output meets the manufacturer’s specifications including the maximum AC ripple.

» Calculate rectifier efficiency and record on the rectifier data sheet.

» Verify the positive cable is attached to the anode bed and the negative cable is attached to the protected structure or pipe.

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Corrosion Control & Monitoring» Miscellaneous Considerations

Inspect cables in terminal boxes to assure correct labels. Verify test stations, bonding stations, and associated hardware

for cathodic protection service. Contact owners/operators of foreign pipelines to enable testing

before and after new cathodic protection project commissioning. Record base readings on the new pipeline or structure prior to

cathodic protection system energizing. Record potentials at all interference bonds and test stations.

Energize system in small current increments and record potentials with each increase until protection is achieved.

Check bonding stations for interference problems. File all commissioning data in the original equipment file.

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– Quality Control Requirements, Internal Surface» Inspect corrosion monitoring installations with the services

of a qualified Corrosion Technician.» Take baseline data prior to pipeline commissioning.» Install lined pipelines per design.» Repair lining of field joints as recommended.» Install corrosion monitoring devices per design.» Complete electrical installations with qualified electricians.» Document commissioning information as a part of the

original equipment file.

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– Quality Control Requirements, Internal Surface» Delay work initiation pending review of design

package by coating inspector.

» Protect coating material from weather.

» Prepare surface for coating per manufacturer’s recommendation immediately before coating installation.

» Follow manufacturer’s recommendation for dew point and humidity.

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OPERATIONS– Perform cathodic protection surveys annually in

accordance with Company CP procedure.– Monitor bonding and test stations annually.– Read and record rectifier output monthly with

changes reported to the SR. Inspector for evaluation and action.

– Correct deficiencies in a timely manner.

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MAINTENANCE– Test rectifier stacks for proper performance

annually.– Check anode bed resistance annually.– Check insulating flanges and spools annually.– Document all maintenance tests and add to the

equipment file.

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Corrosion Control & MonitoringAppendices

A - Coating Reference Index B - Surface Preparation C - Sample Data Sheets

» Rectifier Data Sheet

» Anode Bed Data Sheet

» Galvanic Anode Data Sheet

» Potential Survey Data Sheet

Predesign Testing

houston, texas1 corrosion control and monitoring engineering services lp houston, texas engineering...

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