Field Testing for Shorted Casings AUCSC May 2019 System Diagnostics J. Block

DOT Regulations for Natural Gas Transmission Line Title 49 CFR 192 DOT Regulations for Natural Gas Transmission Line Title 49 CFR 192.467 External corrosion control: Electrical isolation –(c) Except for unprotected copper inserted in ferrous pipe, each pipeline must be electrically isolated from metallic casings that are a part of the underground system. However, if isolation is not achieved because it is impractical, other measures must be taken to minimize corrosion of the pipeline inside the casing. –(d) Inspection and electrical tests must be made to assure that electrical isolation is adequate.

DOT Regulations for Hazardous Liquid Lines Title 49 CFR 195.575 (a) electrically isolate each buried or submerged pipeline from other metallic structures, unless you electrically interconnect and cathodically protect the pipeline and the other structures as a single unit. (c) inspect and electrically test each electrical isolation to assure the isolation is adequate.

NACE Standard SP0169 Requirements 10.4.4 effectiveness of isolating fittings, continuity bonds, and casing isolation should be evaluated during periodic surveys. This may be accomplished by electrical measurements.

NACE Standard SP0200 Requirements 6.2 Monitoring: One or more of the following basic electrical test methods should be used to monitor pipelines and casings on an annual basis. –6.2.1 Potential Survey –6.2.2 Internal Resistance –6.2.3 Four-Wire IR Drop –6.2.4 Cycling Rectifier –6.2.5 Casing Depolarization –6.2.6 Direct Resistance Measurement –6.2.7 Pipe/Cable Locator

Casing Testing: One LDC Approach

CIS Pipe-to-Soil Survey

CIS Survey - 0.90 - 0.68 - 0.65 - 0.71 - 0.73 - 0.69 - 0.70 - 0.78 - 0.95 - 0.96 - 0.72 - 0.93 - 0.83 NACE International (National Association of Corrosion Engineers) recommends connection to the structure under test (pipeline) in this convention. Steel pipe

- 0.95 - 0.85 - 0.75

- 0.98 - 0.90 - 1.47 - 0.44 - 0.93 - 0.52 - 0.11 - 0.33 - 0.77 - 0.22 - 0.95 - 0.66 - 0.71 - 0.83 - 0.23 - 0.85 - 1.67 - 0.93 - 0.69 - 0.65 - 0.50 - 0.68 Steel pipe Steel pipe

Coated Steel Pipe with coating defects The effects of stray current from an electrified transit system can be extremely detrimental to buried metallic structures in the vicinity of the rail tracks. A well coated pipeline can reduce interference current from entering or exiting the pipe surface. Defects in the coating (coating holidays) can provide a path for stray current damage to the pipeline. Coated Steel Pipe Coated Steel Pipe with coating defects

Casing Test: C = clear E = electrolytic M = metallic Structure-to-soil readings that have similar value may indicate an electrolytic condition or metallic short between the pipe and casing. Structure-to-soil readings that have the same value may indicate a metallic short P/S C E M DC Voltage Shift DC current applied to one structure drives the other structure more negative, may indicate a metallic short. DC current applied to one structure drives the other structure less negative or none, indicates a cleared casing C E M PΩ-earth & CΩ - earth Calculated resistance to earth values that are similar may indicate an electrolytic condition. Calculated resistance to earth values that have the same value may indicate a metallic short C E M Calculated resistance between pipe and casing that is ≤ to 1 Ω may indicate an electrolytic condition or possibly a metallic short. If resistance value is ≤ the sum of the pipe-to-earth and casing-to-earth, this may indicate an electrolytic condition or metallic short. PΩ - CΩ C E M Application of a signal locator between the casing and the pipeline that is greatly reduce or lost may indicate a metallic short. Application of a signal locator between the casing and the pipeline that is maintained along the pipeline indicates a cleared crossing. Signal Locator C E M Head-Set Connecting a head-set between the casing and the pipeline will present an audible tone. Tone indicates a voltage potential which may indicate a cleared casing or an electrolytic condition. Lack of an audible tone may indicate a metallic short. C E M

Structure to Soil Potential Structure-to-soil readings that have similar value may indicate an electrolytic condition or metallic short between the pipe and casing. Structure-to-soil readings that have the same value may indicate a metallic short

- .71 - .76

DC VOLTAGE SHIFT DC current applied to one structure drives the other structure more negative, may indicate a metallic short. DC current applied to one structure drives the other structure less negative or none, indicates a cleared casing

- 0.87 - 0.73 - 0.76 - 0.76 External Current Source Temporary Ground Bed

- 0.70 - 0.71 - 0.95 - 0.71

Pipe Ω-earth & Casing Ω-earth Calculated structure resistance-to- earth values that are similar may indicate an electrolytic condition. Calculated structure resistance- to- earth values that have the same value may indicate a metallic short

AMPS I On Off ∆ V Ω I On Off ∆ V Ω 3.01 - 1.30 - .76 .54 .18 2.96 - 0.76 - 1.30 - 1.18 - 0.71 External Current Source Temporary Ground Bed AMPS I On Off ∆ V Ω I On Off ∆ V Ω 3.01 - 1.30 - .76 .54 .18 2.96 - 1.18 - .71 .47 .16

Pipe Ω vs. Casing Ω Calculated resistance between pipe and casing that is ≤ to 1Ω may indicate an electrolytic condition or possibly a metallic short. If resistance value is ≤ the sum of the pipe-to-earth and casing-to-earth, this may indicate an electrolytic condition or metallic short.

Clear

Casing and Carrier Clear -0.05 -1.59 1.12 Battery Casing and Carrier Clear I On Off ∆ V Ω 1.12 - 1.59 - .05 1.54 1.39

Electrolytic

Possible Electrolytic condition between Casing and Carrier -0.05 -1.02 1.28 Battery Possible Electrolytic condition between Casing and Carrier I On Off ∆ V Ω 1.28 - 1.02 - .05 0.97 .75

Shorted

Suspect Metallic Short between Casing and Carrier -0.76 -0.03 3.89 Battery Suspect Metallic Short between Casing and Carrier I On Off ∆ V Ω 3.89 - 0.76 - .03 0.73 .18

Soil Resistivity Meter P 1 P 2 C 2 C 1

Signal Locator Application of a signal locator between the casing and the pipeline. A signal that is greatly reduced or lost, may indicate a metallic short. Application of a signal locator between the casing and the pipeline that is maintained along the pipeline indicates a cleared crossing.

Brand X Pipe & Cable Locator

ACVG

700 A 600 A 500 A 400 A

700 A 600 A 500 A 400 A

Vent Line or Coating Holiday ?

Head-Set Connecting a head-set between the casing and the pipeline will present an audible tone. Tone indicates a voltage potential which may indicate a cleared casing or an electrolytic condition. Lack of an audible tone may indicate a metallic short.

Battery

Gas Main 90 ° at top Gas Main 90 ° at bottom Steam Conduit 170 ° Ground Water 120 °

54” Casing 12” Casing 8” Gas Main Support Bracket 32” Steam Conduit 6” Condensate Line 12” Steam Pipe