Transcript DA Process for Cased Gas Transmission Pipelines

ECDA Process for Cased
Gas Transmission Pipelines
Charlie Hall
Manager, Special Projects
Mears, CPG
Objectives
• Review the ECDA Process From a
Technical and Regulatory Perspective
• Review On-Going Validation Efforts and
our Casing Test Facility
Technical Basis of the ECDA
Process for Cased Pipelines
• Fundamentally the ECDA process seeks to determine if
a corrosive situation potentially exists in the casing.
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Anode
Cathode
Metallic Path
Electrolytic Path
• If the coating is free of holidays, an external corrosion
cell cannot occur (absent disbonded coating issues).
• If a holiday is present, the highest risk of external
corrosion occurs when the holiday is in contact with
electrolyte.
Technical Basis of the ECDA
Process for Cased Pipelines
• If electrolyte is in contact with the holiday and
the casing, indirect inspection tools can detect
the holiday. Additionally, the holiday would be in
the CP circuit and may be receiving adequate
CP.
• If the casing is metallically shorted, the holiday
will likely not receive any available CP. Available
CP will seek the path of lowest resistance, which
most likely is the metallic contact.
• These same principles apply to buried un-cased
piping.
Technical Basis of the ECDA
Process for Cased Pipelines
• Situations that cause external corrosion in cased
pipelines
– Metallic contact between casing and pipeline
– Electrolytic contact between casing and pipeline
– Atmospheric Corrosion on pipeline in casing
Reference GRI-05/0200
“External Corrosion Probability Assessment for Carrier Pipes Inside
Casings”
Casing Corrosion Direct Assessment – ECDA
Larry G. Rankin and Hussain M. Al Mahrous
January 2005
Principles of ECDA Process
Development
• ECDA is a structured process that is
intended to improve safety by assessing
and reducing the impact of external
corrosion on pipeline integrity.
• ECDA is a continuous improvement
process targeted to identify and address
locations where corrosion activity has
occurred, is occurring, or may occur.
DOT Code Requirements for the
ECDA Process
• Per DOT Part 192.921, DA can be used to
assess the integrity of gas transmission
pipelines for the external, internal, and
SCC.
• Per DOT Part 192.921, DA must be
performed in accordance with 192.923,
192.925, 192.927, and 192.929, and
specifically ECDA in accordance with
NACE RP0502.
Application of NACE RP 0502 to
Cased Gas Transmission Pipelines
• Per NACE RP0502, Table 1, Cased crossings requires a
separate ECDA region.
• Per NACE RP0502, Table 2, indirect testing methods are
“applicable” for shorted casings.
• Per NACE RP0502, Table 2, indirect testing methods for
cased piping are “Not Applicable: Not applicable to this
tool or not applicable without additional considerations.
• The ECDA Process we have developed for Cased Piping
addresses the NACE RP0502 requirement for “additional
consideration” and fully complies with DOT part 192 and
NACE RP0502 protocols.
• Mears solicited a clarification to footnote
#3 Table 2 from PHMSA
• Quote from that clarification – one bullet
second clarification include in regards to
footnote #3
• Answer B – is intended to assess the
integrity of the pipe including cased
pipelines
The ECDA Process for Cased
Pipelines
• The Cased Pipeline ECDA Process looks
to find areas where corrosion may have or
may be occurring, just like the ECDA
process for buried uncased pipelines.
• The Cased Pipeline ECDA Process uses
the same 4 steps as used for buried
uncased pipelines.
The ECDA Process for Cased
Pipelines
• The Cased Pipeline ECDA Process meets the same
protocol requirements as for buried uncased pipelines
(ie. immediate, schedule, monitored conditions,
minimum excavation requirements, etc.).
• The Cased Pipeline ECDA Process utilizes Guided
Wave Ultrasonic Inspection as an additional Indirect
Inspection Tool concurrent with ALL Direct Examinations.
• The Cased Pipeline ECDA Process is being designed
using the knowledge gained from the smart pig results of
1201 cased pipelines
• The process is being validated both in the field and using
a newly constructed Casing Test Bed
Pre-Assessment
• Collect all required data elements (additional elements
have been identified for cased pipelines)
• Must be Feasible to perform ECDA on cased pipeline
– Must be able to indirectly examine
– Must be able to directly examine both ends (if
necessary) and comply with all of the PHMSA guided
wave target items
– Must establish meaningful segments and regions for
cased pipelines that pass the “red face test”
Indirect Inspection
Indirect inspection tools can detect metallic or
electrolytic shorted conditions
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PCM (NACE RP 0502)
PCM with A-FRAME (NACE RP 0502)
P/S & C/S Potentials (including CIS both sides)
Internal Resistance (NACE RP 0200)
Cycling the Rectifier (NACE RP 0200)
Pipe/Cable Locator (NACE RP 0200)
Panhandle Eastern Method (AGA)
Has the ability to detect corrosion wall loss
• Guided Wave (Guided Wave UT Target Items)
Are Tools Complimentary?
• The word complementary can mean different
things to different people.
• Typically “complimentary” suggests something
that adds value, reinforces, or supplements
something else.
• When someone says you and your spouse
compliment one another, it suggests that the two
of you are better as a whole, and you make up
for each others’ strengths and weaknesses.
Are Tools Complimentary?
• The IITs for Casings are complimentary.
• The tools look for the same potential
corrosive conditions, but they do so in
slightly different manners.
• This can help to account for the strengths
and limitations of each tool.
• This is also true for the IITs that are used
to assess buried pipelines.
Indirect Inspection Severity
Guide
CASED PIPELINE INDIRECT INSPECTION METHOD INDICATIONS & SEVERITY GUIDE
TYPE OF TOOL
MINOR
(NO PATH INDICATED)
MODERATE
(ELECTROLYTIC PATH)
SEVERE
(METALLIC
CONTACT)
P/S & C/S
POTENTIALS
ELECTRICAL
POTENTIAL
P/S & C/S "ON" DIFFER
BY MORE THAN 100 mV
P/S & C/S "ON" DIFFER
BY 10 mV TO 100 mV
P/S & C/S "ON"
DIFFER BY LESS
THAN 10 mV
PIPE CURRENT
MAPPER
AC CURRENT
ATTENUATION
CURRENT LOSS ACROSS
CASING < 5%
CURRENT LOSS ACROSS
CASING 5%-25%
CURRENT LOSS
ACROSS CASING >
25%
PCM WITH
A-FRAME
AC VOLTAGE
GRADIENT
NO INDICATION AT
EITHER END
INDICATION < 80 dBmA
INDICATION > 80
dBmA
INTERNAL
RESISTANCE
ELECTRICAL
RESISTANCE
PIPE-TO-CASING
RESISTANCE > 0.5 OHM
P-C RESISTANCE
0.01 TO 0.5 OHM
P-C RESISTANCE
< 0.01 OHM
CYCLING THE
RECTIFIER
COMPARE P/S &
C/S POTENTIAL
SHIFTS
>100 mV DIFFERENCE
C/S SHIFT < 25% P/S
SHIFT
10 mV-100 mV DIFF. &
C/S 25%-75% OF P/S SHIFT
< 10 mV DIFF. &
C/S > 75% OF P/S
SHIFT
PIPE/CABLE
LOCATOR
RADIO SIGNAL
NO SIGNIFICANT
SIGNAL LOSS
MODERATE
SIGNAL LOSS
NEAR TOTAL
SIGNAL LOSS
PANHANDLE
EASTERN
METHOD
REVERSE
CURRENT APPLIED
TO CASING
ADDITIONAL TESTING
REQUIRED TO DEFINE
ADDITIONAL TESTING
REQUIRED TO DEFINE
PIPE-TO-CASING RES.
< 0.01 OHM
CASING/PIPE
CAPACITANCE
TINKER & RASOR
MODEL CE-IT
"CLEAR" DISPLAY
NONE
"SHORTED" DISPLAY
COMMON NAME
OF TOOL
Indirect Inspection
Classification of Indirect Inspection Testing
Indirect Inspection Results
1For
DE Prioritization
Any indication of a Metallic
Short or Electrolytic Path
Immediate
NO indication of either a
Metallic Short or Electrolytic
Path
Monitored1
casings that were identified with some history of either a Metallic Short or Electrolytic
Path but are not presently indicating the same , the DE Priority will be moved to the
Immediate category and require direct examination during the first application of the ECDA
process..
Direct Examination
• Must be performed per NACE RP0502.
• Minimum direct examinations per NACE
RP0502 protocols (ie. All immediates, 2
worst case monitored for 1st time through)
• Guided Wave ultrasonic indirect
inspections must be performed during all
Direct Examinations. Any metallic shorts
or indications of electrolytic paths must be
cleared prior to inspection.
Direct Examination
• Guided Wave must comply with all of the
PHMSA Guided Wave Target Items, or
exceptions documented with technical
basis.
Post Assessment
• Must comply with NACE RP0502
Summary of Smart Pig Results
• 1201 cased pipelines smart pigged from
2004 to 2006.
• 144 of the 1201 cased pipelines (12%)
had anomalies with metal loss detected >
20%.
• 20 of the 144 cased pipelines with metal
loss >20% (1.6 % of all cased pipelines)
were found with anomalies > 80 feet from
the nearest end of the casing.
Summary of Smart Pig Results
• The lowest Pf/MAOP for any anomaly was
1.67, and the anomaly was within .1 feet of
the end of the casing.
• The lowest Pf/MAOP for all anomalies >
80 feet from the end of the casing was
1.79 (anomaly 27% deep, 5.3” long).
• The results strongly suggest that external
corrosion is not a significant threat to
cased pipelines.
Validating the Process - Casing Test
Facility
Validating the Process
Casing Test Facility
Example of IIT Results on
Casing Test Facility - PCM
North
South
Distance7 Clear
0
Condition
Simulated Simulated Actual
Elect Short Metallic
Elect
Short
Short
100 ft
231
760
1700
482
50 ft
217
680
1550
471
0 ft
194
593
1340
395
0 ft
191
231
0
218
50 ft
152
149
0
146
100 ft
104
89
0
80
All readings in milli-amps, out of a total of 2 amps
PCM A-Frame detected location of 20%, 50%, and 80% anomalies in shorted conditions
Summary
• The ECDA process and the NACE RP 0502 is
applicable to cased pipelines.
• The process will improve the safety of cased
pipelines by identifying when potential corrosive
conditions occur, requiring direct examinations
and remediation, in the same manner as
required when applying ECDA on buried
pipelines.
• The process will continue to improve, as the
tools and the process are continually improved.
Comments/Discussion
Thank You
Charlie Hall