understanding+graphitization+risk+iron+is+a+combination+of+iron+and+graphite+ +...
TRANSCRIPT
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Understanding Graphitization Risk
Pennsylvania Public Utility Commission 2014 GAS SAFETY SEMINAR
OCTOBER 8, 2104
Author and Presenter: James Datesh, WATTA Inc.
Pittsburgh, PA With Special Thanks to:
Mehrooz Zamanzadeh, PhD. Matco Services, Inc.
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Understanding Graphitization Risk
Who needs to focus graphitization risk
What is graphitization
How to identify it
Assessing the Risk
Why this is important
Outline
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The Who Is Simple
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The Who
Whoever has cast iron pipes in their systems that are old or subject to corrosive conditions
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The Who
Prior to steel, cast iron was widely used for pipeline construction
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The Who
In 2012: 34,000 miles of cast iron main lines and 15,000 miles of service lines
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The Who
Cast iron pipe now found mostly in:
NJ, NY, MA, PA, MI (main lines)
large cities (service lines) e.g., NYC, Boston, Washington, Philadelphia
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What Is Graphitization
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What Is Graphitization
Selective leaching of iron from cast iron
Cast iron is a combination of iron and graphite
When the iron exits, that leaves graphite behind
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What Is Graphitization
The result is a weakened and brittle pipe
But to the eye, the pipe may look unaffected
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What Is Graphitization
Maybe we should rename it, de-‐ironification
Then it would be easier to understand
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What Is Graphitization
Other examples of selective leaching:
the de-‐zincification of brass
the de-‐calcification of bones (better known as osteoporosis)
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How to Measure Graphitization
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How to Measure Graphitization
The HAMMER method
“Clang and Clunck”
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Sensing Graphitization Non-‐Destructively
Localized leaching of iron during graphitization changes the magnetic
permeability of the pipe
This can be used to detect graphitized areas
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The Method
Prototype sensor being
used to measure the thickness of
inset graphite patches
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Measured voltage varies as
the graphite
layer gets thicker
The Output
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Sensing Graphitization Non-‐Destructively
Dr. Zee’s patent : US 7719266 B1
Pipes undergoing graphitization may appear sound.
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Sensing Graphitization Non-‐Destructively
Dr. Zee’s patent : US 7719266 B1
Graphitized regions of pipe wall will be brittle and subject to failure under load as the result of
temperature variation, heavy traffic, or shock.
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Sensing Graphitization Non-‐Destructively
Dr. Zee’s patent : US 7719266 B1
A sensor measures the interaction of an applied magnetic field to a sample surface that includes magnetic materials to determine whether the
samples surface has been corroded.
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How to Measure Graphitization
. . . when the pipe is underground ?
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What is Risk
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What is Risk
The nature of risk is uncertainty
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What is Risk
The nature of risk is uncertainty
Desired outcomes are inherently under threat of failure due to events that may occur during the
asset life-‐cycles
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What is Risk
The nature of risk is uncertainty
Desired outcomes are inherently under threat of failure due to events that may occur during the
asset life-‐cycles
Such events vary in their degree of probabilistic occurrence, magnitude of impact (severity), and
manageability
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Key Risk Factors in Graphitization
Age
Soil chemistry
Soil resistivity (soil conductivity)
Stray current
Corrosion rate
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Key Risk Factors in Graphitization
Age
Cast iron pipe has been in use in the U.S. for 0ver 150 years
Ductile iron pipe could be up to 6o years
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Key Risk Factors in Graphitization
Soil chemistry Soil resistivity (soil conductivity)
Chlorides, sulfates, sulfides
Low soil resistivity (high conductivity) Acidity (low pH)
Wet-‐dry fluctuations Differential aeration
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Key Risk Factors in Graphitization
Stray current
Corrosion rate
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Proactive Steps
Comprehensive surveys e.g., correlate by age, soil conditions, impact,
priority test, access, history, electrical test
Cathodic protection
Pipe replacement
Risk-‐based inspection program
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Proactive Steps
Comprehensive surveys e.g., correlate by age, soil conditions, impact,
priority test, access, history, electrical test
Cathodic protection
Pipe replacement
Risk-‐based inspection program
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Proactive Steps
Comprehensive surveys e.g., correlate by age, soil conditions, impact,
priority test, access, history, electrical test
Cathodic protection
Pipe replacement
Risk-‐based inspection program
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Proactive Steps
Comprehensive surveys e.g., correlate by age, soil conditions, impact,
priority test, access, history, electrical test
Cathodic protection
Pipe replacement
Risk-‐based inspection program
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Proactive Steps
Comprehensive surveys e.g., correlate by age, soil conditions, impact,
priority test, access, history, electrical test
Cathodic protection
Pipe replacement
Risk-‐based inspection program
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Why Is This Important
There are widely recognized risks associated with cast iron pipe in natural gas systems
Graphitization is a dominant factor
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“About every other day over the past decade, a gas leak in the United States has destroyed property, hurt someone or killed someone”
“cast-‐iron pipe — some of it more than a
century old — . . . is the chief suspect”
(USA TODAY Network)
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A Notice by the PHMA on 03/23/2012
Pipeline Safety: Cast Iron Pipe (Supplementary Advisory Bulletin)
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the need for continued safety improvements to aging gas pipeline systems
urges owners and operators to conduct a
comprehensive review of their cast iron distribution pipelines
and replacement programs
(PHMA)
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Summary
Who needs to focus graphitization risk
What is graphitization
How to identify it
Assessing the Risk
Why this is important
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Conclusions
Graphitization introduces serious risk
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Conclusions
Graphitization introduces serious risk
Non-‐destructive magnetic detection of graphitization is feasible
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Conclusions
Graphitization introduces serious risk
Non-‐destructive magnetic detection of graphitization is feasible
Risk assessment should be applied
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Understanding Graphitization Risk
Pennsylvania Public Utility Commission 2014 GAS SAFETY SEMINAR
OCTOBER 8, 2104
Author and Presenter: James Datesh, WATTA Inc.
Pittsburgh, PA With Special Thanks to:
Mehrooz Zamanzadeh, PhD. Matco Services, Inc.
Thank you for attending
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Question & Answer