risks of failure in aging pipelines.pdf

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


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


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.


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.


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


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


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


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 *


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


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.


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


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


RBI-Risk Based Inspection

Safety

class

Annual failure

probability

High <10-5

Normal <10-4

Low <10-3


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


– 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


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

Feeble Pipe Support


Activities at Sidhpur Side


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



Risk of Operating Low

Frequency Electric

Resistance Welded Pipes


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


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

risks of failure in aging pipelines.pdf

Documents

new delhi

wall loss anomalies

effective inspection

line inspection ili

wall loss criteria anomalies

line inspection report

critical metal loss

inspection rm policy