Corrosion Control A PHMSA Perspective
description
Transcript of Corrosion Control A PHMSA Perspective
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Corrosion ControlA PHMSA Perspective
Pipeline Safety Trust ConferenceNew Orleans, LA
November 17, 2011
Joe MataichCATS Program ManagerPHMSA, Southern Region
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Definition of Corrosion
The Deterioration of a Material, Usually a Metal, that Results from a Reaction with its Environment.
Galvanic Corrosion of a Metal Occurs because of an Electrical Contact with a More Noble (Positive) Metal or Non-metallic Conductor in a Corrosive Electrolyte.
- 2 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Basic Corrosion Cell
Fe
Fe
Fe
Metallic Path
Ionic Path
- 3 -
4
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Pipeline Corrosion
Anodic Area Cathodic Area
Metallic Path
- 5 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Cathodic Protection
Ano
de
Cathode
- 6 -
Galvanic Anode CP SystemRelies on potential difference between steel
and anode (Mg, Zn, Al)
- 7 -
8
Impressed Current Cathodic ProtectionHas DC power source (rectifier)
underground pipeline
-975
Reference electrode (Cu/CuSO4)
Voltmeter
Pipe-to-Soil Potential MeasurementUsed to evaluate adequacy of Cathodic
Protection
- 9 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Cathodic Protection Criteria
• §192.463 Requires Cathodic Protection to a Level that Complies with Appendix D of Part 192
• §195.571 Requires Cathodic Protection to a Level that Complies with section 6.2 and 6.3 of NACE SP0169-2007
- 10 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Cathodic Protection Criteria
• - 850 mV• 100 mV Polarization • Negative 300 mV Shift • Net Protective Current• E log I
* Gas and Liquid * Gas Only- 11 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Regulatory Inspections
• All PHMSA and State Inspectors are trained– PHMSA T&Q Corrosion Course in OKC
• Corrosion Control Requirements are checked during inspections– Records – Field Inspections
- 12 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Cathodic Protection Monitoring Regulatory Requirements
• Pipe-to-Soil Potentials measured once per calendar year, not to exceed 15 months
• Rectifiers checked six times per calendar year, not to exceed 2.5 months
- 13 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
What can go Wrong?
• Pipe-to-Soil Potentials/Rectifier tests– Measurement error– Improperly calibrated measurement equipment– Broken or defective test leads
• How PHMSA addresses these– Both are OQ Covered Tasks– PHMSA/State Inspectors trained to identify deficiencies– Potentials and Rectifiers are checked during PHMSA/State field
inspections
- 14 -
Shielding of CP CurrentCurrent is blocked by disbonded coating, rocks etc.Addressed in HCA’s through Integrity Management
- 15 -
Interference CurrentsDC currents from foreign rectifier, transit systems etc.
Addressed by regulatory requirements for interference mitigation program
- 16 -
U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Questions?
- 17 -