Risks of Failure in Aging Pipelines.pdf
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S.S.Gupta
Chief Inspection Manager
Indian Oil Corporation Limited
Pipelines Division, Noida
Risks of Failure in Aging
Pipeline: Repairs and Replacement
IOC Pipeline Details
About 35% of our
pipelines are more than
20yrs old
About 18% have served
more than the design life
i,e 30 years
26/4/2013 2 Petrofed, New Delhi
4% 14%
18%
65%
Grouping by Age of Pipelines
> 40 yrs 30-40 yrs 20-30 yrs <20 yrs
435
2014
3980
5423 6364
7730 8951 9273
10899 11214
0
2000
4000
6000
8000
10000
12000
1964 1974 1984 1995 1999 2003 2005 2007 2010 2013
Le
ng
th,
km
Year
Growth of Pipeline
Inspection of Ageing Pipelines
26/4/2013 Petrofed, New Delhi 3
ILI (MFL,UT) has been highly effective
CAT/DCVG/CIPS are usually effective.
Pressure test is done only for Low frequency ERW pipes
Inline inspection
Geometry tools
CAT/DCVG;
CIPS; Bell hole
Pressure test
5550
2730
2905
Intelligent Pig Survey
Completed
Planned 2013-14
IPS in subsequent years
Figures in KM
Assessment/Repair/Replacement
ERF and wall loss criteria
• Anomalies with ERF>1
• Anomalies >30% wall loss
• Anomalies in high pressure zone
• Pipeline sections with very high concentration of defects
High Consequence
Areas
• Very high population density
• Water bodies
• Unusually sensitive areas
Others
• Expansion of public utility corridors
• Washouts
• Sabotage
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Failure Trend of Pipelines
Pipeline (built with old technology) failures are limited within 1st 20 years
Pipeline failure increase towards end of design life.
Highly Effective inspection followed by repair/ replacements could extend the service life
26/4/2013 Petrofed, New Delhi 5
0
1
2
3
4
5
6
7
8
No
. o
f fa
ilu
res
Year
Failures in section PL-1
Nil
Failures Observed
Increased failures after 2003 were due to ageing and due to growth of unreported critical defects in IPS-1998.
Some of the sections were cathodically unprotected.
26/4/2013 Petrofed, New Delhi 6
Reasons for Increased Failures - 2004
Significant growth of
corrosion features
form year 1998 to
2009.
Some of critical metal
loss features were
unreported.
These features grew
over time from 1998 to
2004 and yielded.
26/4/2013 Petrofed, New Delhi 7
0
100
200
300
400
500
600
700
800
900
Sec-1 Sec-2 Sec-3 Sec-4 Sec-5 Sec-6 Sec-7 Sec-8
No
. o
f w
all
lo
ss
fea
ture
s
Pipeline sections
Growth of Corrosion Features (WL>30%) 1998 2009
0
10000
20000
30000
40000
50000
Sec-1 Sec-2 Sec-3 Sec-4 Sec-5 Sec-6 Sec-7 Sec-8No
. o
f w
all lo
ss
fe
atu
res
Pipeline sections
Growth of Corrosion Features (WL-10 to 30%) 1998 2009
REPAIR AND
MAINTENANCE
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R&M Methods Adopted
Repairs based on ERF, wall loss criteria and HCA’s
• Metallic sleeves (Type A and Type B)
• Composite sleeves and wraps
• Leak clamps
Replacements based on very high defect concentration or expansion of public utility corridor
• Hot-tapping and cold cutting
• Water flushing and cold cutting
• Using weld plus ends
26/4/2013 Petrofed, New Delhi 9
Time bound inspection followed by assessment
based on ASME-B31G / Modified ASME-B31G
Risk Based Inspection
R&M Policy is Based Around In-line Inspection (ILI)
Dealing with In-Line Inspection Report
What Do I Do when I get an ILI report in hand ?
• This question is to be answered as soon as you decide to carry out ILI, Not after you get ILI report
Repair Replace Do not do anything
Prioritize Anomalies
On
th
e b
asi
s o
f O
pe
rati
ng
P
ress
ure
On
th
e b
asi
s o
f %
wa
ll lo
ss
On
th
e b
asi
s o
f R
isk
On
th
e b
asi
s o
f D
efe
ct
Po
pu
lati
on
D
en
sity
Prioritize Zones to be replaced
On
th
e b
asi
s o
f Li
fe e
xte
nsi
on
o
f p
ipe
lin
e
To c
om
ply
wit
h
reg
ula
tory
re
qu
ire
me
nt
/ R
isk
Nei
ther
rep
air
no
r re
pla
ce
Str
eng
then
co
rro
sio
n c
on
tro
l d
evic
es
Getting Maximum Out of ILI
26/4/2013 Petrofed, New Delhi
CORROSION ASSESSMENT CRITERIACORROSION ASSESSMENT CRITERIA
SF = S 1 - A/AO
1 - A/AO M-1
B31G* A =2/3 Ld 1.1 SMYS FOR L2/Dt < 20, M= 1 - 0.8(L2/Dt)
RSTRENG 85% A = 0.85 Ld SMYS+
10000 PSI L2
Dt < 50, M=1- 0.6275L2/Dt - 0.003375(L2/Dt)
FOR
FOR L/Dt2 › 50, M=0.032L2/Dt + 3.3RSTRENG
EFFECTIVE
AREA
A ESTABLISHED
FROM CORR
PROFILE
* FOR L2/ DT > 20, SF = S{ 1- d/t }
SF = PREDICTED FAILURE STRESS, S = FLOW STRESS ,
SMYS= Specified minimum yield stress
A = Area of missing Meta, Ao= Area prior to metal loss (L x t)
M = Folias Factor, f {L, D, t} , L = axial length of corrosion
D= nominal out side diameter , t = nominal wall thickness of pipe
CriteriaArea of
Missing metal
Flow Stress,
psi ( S)Folias faxtor, M
26/4/2013 Petrofed, New Delhi
0
10
20
30
40
50
60
3.7 4.2 4.7 5.2 5.7 6.2 6.7 7.2 7.7 8.2 8.7 9.2 9.7 10.2 10.7 11.2 11.7 12.2 12.7 13.2 13.7 14.2 14.7 15.2 15.7
Pre
ssu
re (
Kg
/sq
.cm
)
Defect Length (Inch)
Pressure Chart*
30% Metal Loss
40% Metal Loss
50% Metal Loss
60% Metal Loss
70% Metal Loss
T" W0.281, Dia" 24XYZ Pipeline
G31Based on ANSI B *
26/4/2013 Petrofed, New Delhi
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
defe
ct depth
(d)
/WT
L , Defect Length(in.)
DEFECT SENTENCING CURVE XYZ Pipeline
100 % SMYS Line
Hydro test Line ( 80% SMYS)
MAOP= 52.8 KCS, Design Factor = 0.72, SMYS = 52,000 psi
O.D.= 28 inch , NWT = 0.281 in.
Repair Zone
Failure Zone
Monitoring Zone
Acceptance Zone
MAOP Line
Re-assessment
zone d WT
L
Minimum required
Safety Margin
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Pipeline Repairs and Replacement
4.9km section (Ch. 73.0 to 77.9km) is considered for replacement due to very high concentration of defects.
All other defects (ERF>1 and wall loss>30%) were repaired.
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0
25
50
75
100
125
150
175
0 3 6 9 13 15 17 19 26 28 42 44 46 50 52 54 63 65 67 69 71 73 75 77 79 86 95 97
No
. o
f an
om
alies
Pipeline Chainage
PL-1 Section
Very high defect density
Extensive Coating Refurbishment
Large scale coating refurbishment since 2008
Improved coating materials as compared to earlier CTE
coating
26/4/2013 Petrofed, New Delhi 17
158
292
139
463
0
50
100
150
200
250
300
350
400
450
500
1996-2000 2000-2004 2004-2008 2008-2013
Pip
eli
ne
Le
ng
th, k
m
Year
Coating Refurbishment
Effect of R&M on service life
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RBI-Risk Based Inspection
Safety
class
Annual failure
probability
High <10-5
Normal <10-4
Low <10-3
26/4/2013 Petrofed, New Delhi 19
0.E+00
1.E-05
2.E-05
3.E-05
4.E-05
5.E-05
6.E-05
7.E-05
8.E-05
9.E-05
0 5 10 15 20 25 30 35
Fa
ilu
re p
rob
ab
ilit
y
In service years
Probability of Failure
PL sec-1 PL sec-3
Two pipeline sections are compared based on failure probability
Probability of failure increases with ageing of pipeline
Highly effective inspections combined with proper R&M practice
helps keep the failures low.
RBI is one of the key approach to keep failure probability low
even with ageing pipelines.
Repairs / Replacements -REFERENCES
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– API 1104
» Welding of Pipelines and
Related Facilities
– API 1107
» Pipeline Maintenance Welding
Practices
– ASME B31.8
» Gas Transmission and
Distribution Piping Systems
– ASME B31.4
» Liquid Transportation Systems
for Hazardous Chemicals and
Hydrocarbons
Pipeline Repair - Issues
– Initial Inspection
» Determine soundness of the pipe adjacent to the defect
prior to work
» Inspect external surface of the pipe by one of the
following methods:
Inspect exterior of pipe visually aided by a pit gage.
Use magnetic particle inspection if cracking is
suspected.
Determine pipe wall thickness with ultrasonic testing.
Use radiographic inspection as required for definition.
Deciding Need For Repair
Pipeline Repair
» Repair dents deeper than 1/4” on pipe to NPS 12
or more than 2% greater than NPS 12.
» Repair dents that affect the curvature of the pipe with removal of a cylindrical section containing the defect and replacement with an equivalent section.
» Repair dents not meeting the above restrictions by filling the dent with a hardenable material and installing a full encirclement welded split sleeve.
– Leak Repair - Gouges, Grooves, and Dents
» Repair by cutting out a section of the pipeline containing the defect and replace with a new section of equivalent or higher strength and composition.
» Reduce pressure to 20%SMYS or less if line cannot be removed from service. Use one of the following methods for repair:
Install a full encirclement welded split sleeve.
Repair with installation of a full encirclement welded hot tap sleeve providing the entire defect can be removed with the hot tap coupon.
Pipeline Repair
Caliper survey report
Reported Actual
Dent depth 45.7mm 40mm
% ID
reduction
8.36 7.32
Length 586mm 600mm
Location 6’O Clock 6’O Clock
Handling Dents
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Handling Dents
DP test of dent
area
• DP test showed no
indication of crack.
• UT showed thickness
ranging from 5.9 to 7.0mm
(original wall thk is
6.35mm).
Handling Dents
Pipeline Repair – Basic Requirement
» Welder Qualifications
Use Company welding procedure for qualification of
Company employees to make weld repairs.
Use Contractor welding procedure (Company approved)
for qualification of Contract employees to make repairs.
» Burn through control
Burn through during welding is not expected when
welding parameters do not exceed 20 volts and 100
amperes, if the remaining wall thickness is greater than
0.320 inches (See ASME/ANSI B31.8, paragraph
851.43f). Welding performed outside these limits must be
approved by the Plant Engineer.
– Welding
» Check for hardness on hydrogen lines and maintain a hardness equal to or less than BHN 235.
» Welding Procedures
Perform all weld repairs by Company employees using Company Welding Procedure Specification (WPS) 1.2.
Perform all weld repairs by Contract employees using Company-approved welding procedures provided by the Contractor.
Pipeline Repair
– Methods of Repair - Corroded Areas
» Repair, if possible, by cutting out a cylindrical pipe section and replacing it with a pipe of equal or greater design strength.
» Do not weld on LPG or ethylene pipelines before shutdown/purging operations are complete.
» Acceptable repairs on a pipeline during operation:
Weld a nipple over a small leak and install fitting.
Install a leak clamp over a corrosion pit.
Repair with full encirclement welded split sleeve.
Pipeline Repair
– Leak Repair - Cracks or Tears
» Replace a cylindrical section containing the crack or tear with an equivalent pipe section.
» Reduce the pressure to 20%SMYS equivalent or less if the line cannot be removed from service.
Determine the pipe condition by visual and NDE methods.
Stop welding or heating operations on the pipe.
Drill the ends of the crack and test by NDE
Repair with a full encirclement welded split sleeve.
Request Unit Manager approval to return to service.
Pipeline Repair
RECONDITIONING OF PIPE
– Pipelines that cannot be removed from service » Repair with replacement of an equivalent section.
» Repair cracks in welds by grinding and rewelding.
» Repair small corroded areas by weld metal overlay.
» Repair small pitted areas by weld metal overlay with a welded patch or full encirclement sleeve
» Repair large corroded area with a full encirclement welded split sleeve.
» Repair all gouges or grooves deeper than 10% wall thickness. Use a full encirclement welded sleeve.
Weld Less Repair- Type A Sleeve
Typically a pressure reduction is
not necessary if it can be shown
that the defect is not at or near
its predicted failure pressure.
For example , if calculations
based on the size of the defect
show that its predicted failure
pressure is 33.33% or more
above the current pressure, a
type A sleeve can effectively
repair it without reduction in
pressure
How much Stress does a Type A Sleeve
Take ?
Composite Reinforcement
Leak clamp – When to Use
It is not necessary that Leak
Clamp is used when ever there
is a leak
Neither it is necessary to weld
the Leak Clamp immediately
after the flow is restored
One can use welded sleeves
(Type B) sleeves as well in
place of a leak clamp
How a Corroded Pipeline look when
You Daylight
Take Measurement Carefully and
Correctly
Welding Procedures and Precautions are
necessary while welding a Leak Clamp
Fabrication of Type B Sleeve is Critical
to get a Perfect Fit
A Case of Pipeline Replacement
Old Road New Road
Pipelines
PL1
Road
26/4/2013 44 Petrofed, New Delhi
Feeble Pipe Support
26/4/2013 45 Petrofed, New Delhi
Activities at Sidhpur Side
26/4/2013 46 Petrofed, New Delhi
Abu Road Side 26/4/2013 47 Petrofed, New Delhi
Activities in Sidhpur Side 26/4/2013 48 Petrofed, New Delhi
Activities in Abu Road Side
26/4/2013 49 Petrofed, New Delhi
26/4/2013 50 Petrofed, New Delhi
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Risk of Operating Low
Frequency Electric
Resistance Welded Pipes
26/4/2013 Petrofed, New Delhi 52
Risk of Operating Low Frequency Electric
Resistance Welded Pipes (LF-ERW)
ERW pipes of late sixties and early seventies are made by Low
Frequency (LF) welders in the pipe mills, which was the state of art at
that time
Weld seam of LF-ERW pipes are prone to cold welding (due inconsistent
weld temperature) and presence of inclusion (higher sulphur content) in
the seam area
Electric Resistance Welded (ERW) pipes fabricated in late sixties and
early seventies in India are prone to seam failure
Commonly used magnetic flux leakage type Intelligent pigs are unable to
identify weld seam of ERW pipes.
Experience indicate presence of even 10% of corrosion across or near
the weld seam can cause seam opening.
Only method for evaluating integrity of such pipeline is through hydro
static pressure testing.
LF-ERW Pipe Seam Failure
26.4.2013 Petrofed, New Delhi 53
Weld Seam
Hydrostatic Pressure Testing
Ensure leak tightness of pipeline at 1.25 times of MOP
(Maximum Operating Pressure) for at least 4 hours.
– Time dependent threats i.e. internal / external corrosion
and stress corrosion cracking
– Stable threats i.e. manufacturing related particularly
pipe seams.
Limitations:
– Destructively removes critical size defects
– Sub-critical flaws are not identified
– May initiate a crack growth
26/4/2013 Petrofed, New Delhi 54
Failure Pipe Replacement
Weld Plus ends being used for replacement burst pipe
Seam failure at Ch. 0.55km of 18” KV section of KSPL
Pipeline Repair- Other Key Points
– Coating Repair
» Repair pipe coating damaged during pipeline
repair activities in accordance with the original
coating manufacturer’s recommendations.
» Hydrotest pipe replacement sections to 1.5
times MAOP prior to installation. Hold for one
hour.
» Test all field welds with 100% NDE coverage
using the best method for the weld
configuration.
» Grade and repair weld defects in accordance
with API 1104 and API 1107 requirements.
Pipeline Repair
– Documentation
» Include the location of the leak, location class,
grade of the leak, and action taken when writing
leak reports.
» Add repair reports to the original equipment file, the
inspection file, and the OISD coordinators file.
» The OISD -141 shall determine if the leak is
classified as an incident that requires reporting to
the regulatory authorities like OISD and others.
Thank You
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