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

Southern Nevada Division

Explorer ProjectLas Vegas

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

Work site congestion

Manual Tether

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

PATENT

PENDING

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

Questions on Explorer project?

Southern Arizona Division

Dig and Inspect (D&I)

ProjectYuma

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 Inspect Overview

• 35 D&I Bellholes• Wall thickness data

Dig and Inspects in So. AZ

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

Questions???

Thank

You