Wall Thickness Data Collection
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Transcript Wall Thickness Data Collection
Presented by
Doug Gapp
Pipeline Safety Planning Dept
Southwest 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
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
PHMSA
Integrity Verification Process
Likely will require action on transmission pipe
operating in HCAs and Class 3 and 4 locations
Focus of NTSB, federal legislators, regulatory
agencies
Transmission pipelines
HCAs
Data – Know your pipelines so you can properly
evaluate risk
1979 Acquired
gas system
from Tucson
Gas and
Electric
1984 Acquired
gas system
from Arizona
Public Service
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
Conventional In-line Inspection (ILI)
Other ILI tools
Pipetel Explorer – Southern Nevada Division (SND)
Dig and inspects (D&Is)
Southern Arizona Division (SAD)
•
•
Available for pipe sizes 6” to 36”
•
Wireless/battery operated
•
~ 3300 foot range
•
Camera (front and back)
•
Remote Field Eddy Current Sensor (RFEC)
•
Magnetic Flux Leakage (MFL)
•
Maneuver through standard fittings
Either live or de-gassed pipeline
Explorer Project
Las 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
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
• 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
Manual
Tether
Pre excavate pits, larger than standard bellholes
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
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
Validate data – field work
Two locations for inspection
Dent
Lowest WT reading
Updated WT attribute data
Final follow-up with vendor
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
Questions on Explorer project?
Dig and
Inspect (D&I)
Project
Yuma
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
• 35 D&I Bellholes
• Wall thickness data
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 highpressure distribution
Lowered comparative risk
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
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???