Presented by Doug Gapp Pipeline Safety Planning Dept Southwest Gas Corporation August 19, 2014...
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Transcript of Presented by Doug Gapp Pipeline Safety Planning Dept Southwest Gas Corporation August 19, 2014...
Wall Thickness Data Collection
-Southern Nevada Division-Southern Arizona Division
Presented byDoug Gapp
Pipeline Safety Planning DeptSouthwest Gas Corporation
August 19, 2014 Western Region Gas Conference
San Bruno Incident, September 9, 2010 Pipeline Hazardous Materials Safety
Administration (PHMSA) Advisory Bulletin ADB 11-01, Jan 10, 2011 Evaluate risk – physical and operational characteristics
California Independent Review Panel San Bruno (Recommendation 5.6.4.2), June 24, 2011 Program to collect…construction and operating data
PHMSA 2011 Advanced Notice of Proposed Rulemaking (Section D), August 25, 2011 Requirements for collecting, validating, integrating and
reporting pipeline data
Timeline of Items Prompting Wall Thickness Data Collection Program
National Transportation Safety Board (NTSB), August 30, 2011 San Bruno 29 Recommendations Recommendations specific to Integrity Management
Program (IMP) Completeness/Accuracy Integrity Management Program Data
Federal legislation, January 3, 2012 Confirm material strength
Pipelines operating in high-consequence areas (HCAs) Greater than 30 % specified minimum yield strength (SMYS)
California Public Utilities Commission 17 Hazards Report (Item 4), March 14, 2012 Verifiable and traceable records
Timeline of Items Prompting Wall Thickness Data Collection Program
PHMSA Integrity Verification Process
Likely will require action on transmission pipe operating in HCAs and Class 3 and 4 locations
Timeline of Items Prompting Wall Thickness Data Collection Program
Focus of NTSB, federal legislators, regulatory agencies Transmission pipelines HCAs Data – Know your pipelines so you can properly
evaluate risk
Common Theme
1979 Acquired gas system from Tucson Gas and Electric
1984 Acquired gas system from Arizona Public Service
Southwest GasChallenges
November 2012 proposed field data collection initiative-wall thickness pilot
Goal: improve knowledge and records of company pipeline characteristics
Specifically: Collect wall thickness data where not documented Accurately classify pipeline Appropriate integrity management application
Transmission Integrity Management Program (TRIMP) Distribution Integrity Management Program (DIMP)
pipe that meets transmission classification by actual properties, not lack of records
SWG Proactive Approach
Conventional In-line Inspection (ILI) Other ILI tools
Pipetel Explorer – Southern Nevada Division (SND) Dig and inspects (D&Is)
Southern Arizona Division (SAD)
Approaches for obtaining wall thickness data
Explorer Inspection Tool
• Available for pipe sizes 6” to 36”
• Either live or de-gassed pipeline
• Wireless/battery operated
• ~ 3300 foot range
• Camera (front and back)
• Remote Field Eddy Current Sensor (RFEC)
• Magnetic Flux Leakage (MFL)
• Maneuver through standard fittings
Successful launch and recover robotic tool (tetherless)
Into a non-live natural gas pipeline Obtain wall thickness (WT) data Identify potential metal loss
First SWG commercial application
Objective
Crossing that prohibited conventional inline inspection tools from passing
Pipeline diameter – 6-inch Maximum operating pressure (MOP) – 125 psig
5522 feet unconfirmed wall thickness (WT) Conservative assumption of 0.083 inches WT 21 feet 0.156 inches WT Specified Minimum Yield Strength (SMYS) unknown
Conservative assumption of 24,000 psi 20.78% SMYS at MOP
Vintages 1964, 1968, and 1972
Southern Nevada Division-Commercial Application
ILI Overview
• Originally planned for 3 bellholes, ended up with 4• Tool run twice for each distance
• Wall thickness data• Metal loss data
Urban location traffic & noise Night work Crossing over storm drain Question: What if it gets stuck? Answer: Put a leash on the pig
Challenges
Pre excavate pits, larger than standard bell-holes
Horizontal launch Opted for out of service Night work due to heat of summer
Reduce project complexity Heat impacted equipment (no flow to cool)
Improvised air conditioning pipeline
Planning/Lessons Learned
Anomalies No Immediate or Scheduled repair required No metal loss locations 7 suspected dents 3 suspected dents or material deposits
Wall Thickness data Majority of pipe is 0.156 inches (11.1% SMYS) some 0.188 inches WT (9.2% SMYS)
Not the 0.083 inches WT
What did we find?
Validate data – field work Two locations for inspection
Dent Lowest WT reading
Updated WT attribute data Final follow-up with vendor
What’s next?
Experience with Explorer tool Once confirmatory digs completed able to
correctly classify pipe Avoided replacement
Explorer cost between $200K-$300K per mile Compared to $2+ million/mile to replace
Explorer Tool in So. NV-Results
Pipeline Diameter – 6-inch Maximum Operating pressure – 150 psig 1.3 miles Unconfirmed wall thickness (WT)
Conservative assumption of 0.083 inches 1.2 miles confirmed WT upstream classified as
transmission Specified Minimum Yield Strength (SMYS) unknown
Conservative assumption of 24,000 psi 24.9% SMYS
7 HCAs Vintages
1954, 1955
Southern Arizona Division Dig and Inspects -Yuma
Dig and Inspects in So. AZ-Results
1954 vintage changed to 0.250 wall – 8.3% SMYS
1955 vintage changed to 0.188 wall – 11.0% SMYS
Cost Comparison Actual cost was approximately $50K Allowed reclassification 2.5 miles of pipe to high-
pressure distribution Lowered comparative risk
What next?
Southern Arizona Division D&I: Yuma-Wellton Approximately 93,000 feet of 4-inch pipe
unknown WT 2 HCAs
Central Arizona Division Explorer ILI: Litchfield Ave Approximately 2500 feet of 6-inch pipe unknown
WT Almost entirely in an HCA
Summary
Pipe with: Unknown wall thickness? Operating at high % SMYS? Actual wall thickness likely higher? Unpiggable?
Determining actual wall thickness: Lowers relative risk in HCAs Accurately classify pipe Appropriate integrity management application