ECDA · 2016-08-04 · Slide 3 METHODOLOGY ECDA is conducted in 4 steps Step Key Actions 1...

Contents

• Methodology

• Application

• Pre-assessment

• Indirect Inspection

• Detailed Examination

• Post-assessment

• Questions

EXTERNAL CORROSION DIRECT ASSESSMENT

METHODOLOGY

ECDA is conducted in 4 steps

Step Key Actions

1 Pre-assessment

● Feasibility study

● Data collection

● Identification of ECDA regions

● ECDA indirect assessment tool selection

2 Indirect Inspection

● Above ground inspections

● Identification of critical sites, i.e. those considered most likely susceptible to external corrosion

● Ranking of sites

3 Detailed Examination ● Excavation of critical sites

● Infield data collection and measurements

4 Post Assessment

● Immediate / future fitness-for-purpose assessment

● Determination of re-assessment interval

● Evaluation of ECDA effectiveness

• Feasibility

• Applicability of the methodology

• Data gathering

• Data

• Availability

• Input

• Definition of ECDA regions

• Parameters used to define ECDA regions are not prescribed by

NACE

• NACE define ‘data elements’ which may or may not be

considered.

• Goal orientated process that recognises common differences

METHODOLOGY: PRE-ASSESSMENT

• ECDA Tool Selection, how and where?

• Based on ground conditions / detection capability, and;

• Based on the results of the region definition and perceived threat, so;

• May be done on an isolated region or whole of line.

METHODOLOGY: PRE-ASSESSMENT

• Conducting of above ground inspections

• Interpretation of results

• Severity of results

• Identification of potential dig sites

• Refinement of potential dig sites

METHODOLOGY: INDIRECT ASSESSMENT

To satisfy the requirements of the pre-assessment and form the basis of the

region identification and ranking, an adaptation of the established MACAW

‘QPRAM’ threat model has been used.

QPRAM uses a tri-matrix system to and assess threats:

APPLICATION

Matrix Type Threat Mitigation Interaction

Content Mechanistic parameters

which assess the threat

severity

Survey and condition

monitoring results

Effectiveness of mitigation

activities in relation to

specific threat parameters

Examples

Pipe/coating age

Soil analyses

AC/DC interference

Casings

CIPS/CIS

DCVG

Current attenuation

Combined mitigation of

coating and CP

Threat Matrix Mitigation Matrix

APPLICATION

QPRAM Threat Algorithm

APPLICATION

𝑆𝑒𝑣𝑒𝑟𝑖𝑡𝑦 𝑅𝑎𝑡𝑖𝑜 = 𝑆𝑛

1 − 1 −𝑀1𝐸1 …(1 −𝑀𝑛𝐸𝑛)

𝑃𝑜𝐹 = 𝐵𝑃𝑜𝐹 𝑆𝑒𝑣𝑒𝑟𝑖𝑡𝑦 𝑅𝑎𝑡𝑖𝑜𝑠

𝑆𝑒𝑣𝑒𝑟𝑖𝑡𝑦 𝑅𝑎𝑡𝑖𝑜 = 𝑇ℎ𝑟𝑒𝑎𝑡 𝑃𝑎𝑟𝑎𝑚𝑒𝑡𝑒𝑟

𝐴𝑝𝑝𝑙𝑖𝑐𝑎𝑏𝑙𝑒 𝑀𝑖𝑡𝑖𝑔𝑎𝑡𝑖𝑜𝑛𝑠

APPLICATION


1 − 1 −𝑀1𝐸1 …(1 −𝑀𝑛𝐸𝑛)

APPLICATION


1 − 1 −𝑀1𝐸1 …(1 −𝑀𝑛𝐸𝑛)

Co

atin

g Ty

pe

Mill

or

fiel

d a

pp

lied

Co

atin

g A

ge

Soil

Res

isti

vity

No coating >25 years

<=1000

Ohm.cm or

Unknown

100%

95%

20-25 years 90%

85%

Asphalt /

Bitumen /

Coaltar

80%

15-20 years1000 - 5000

ohm.cm75%

Tape wrap 70%

65%

10-15 years5001-10000

ohm.cm60%

55%

Epoxy Paint 50%

45%

THREAT MATRIX - THREAT DRIVER

Ver

y H

igh

Hig

hM

ediu

m H

igh

Med

ium

Threat Matrix

APPLICATION


1 − 1 −𝑀1𝐸1 …(1 −𝑀𝑛𝐸𝑛)

Co

atin

g Ty

pe

Mill

or

fiel

d a

pp

lied

Co

atin

g A

ge

Soil

Res

isti

vity


<=1000

Ohm.cm or

Unknown

100%

95%

20-25 years 90%

85%

Asphalt /

Bitumen /

Coaltar

80%

15-20 years1000 - 5000

ohm.cm75%

Tape wrap 70%

65%

10-15 years5001-10000

ohm.cm60%

55%

Epoxy Paint 50%

45%


Ver

y H

igh

Hig

hM

ediu

m H

igh

Med

ium

Threat Matrix

Mitigation Matrix

APPLICATION


1 − 1 −𝑀1𝐸1 …(1 −𝑀𝑛𝐸𝑛)

Co

atin

g Ty

pe

Mill

or

fiel

d a

pp

lied

Co

atin

g A

ge

Soil

Res

isti

vity


<=1000

Ohm.cm or

Unknown

100%

95%

20-25 years 90%

85%

Asphalt /

Bitumen /

Coaltar

80%

15-20 years1000 - 5000

ohm.cm75%

Tape wrap 70%

65%

10-15 years5001-10000

ohm.cm60%

55%

Epoxy Paint 50%

45%


Ver

y H

igh

Hig

hM

ediu

m H

igh

Med

ium

Co

atin

g Ty

pe

Mill

or

fiel

d a

pp

lied

Co

atin

g A

ge

Soil

Res

isti

vity

An

earo

bic

So

il

Soil

Co

rro

sivi

ty

An

y ev

iden

ce o

f D

C

inte

rfer

ence

Do

es t

he

pip

elin

e ru

n

par

alle

l to

HV

AC

po

wer

lines

Cas

ing

insu

lati

on

sta

te

Esti

mat

ed C

oat

ing

Co

nd

itio

n

Exte

rnal

Co

rro

sio

n

Failu

res

in t

he

last

yea

r

Coating Survey date 60% 60% 60% 60% 50% 50% 50% 70%Results of coating Survey (e.g. highest IR% drop,

DCVG)

Were necessary coating repairs completed?

CP system fitted and active 80% 80% 80% 80% 80% 20%

CP Minimum Protection Criteria

Date of inspection (CIPS)

CIPS Survey Results

Date of Test post ON/OFF inspection

Test Post ON/OFF CP Survey Results

Isolation Joints fitted 50% 50%

Isolation Joint Inspection

Has any DC remediation been necessary 80%

Casing Inspection 50%

Bug Count 60%

Has any AC remediation been necessary 80%

Compliance with the external corrosion program

according to the PAI30%

External Corrosion

THREAT DRIVERS

MIT

IGA

TIO

N M

EASU

RES

Threat Matrix

Interaction Matrix Mitigation Matrix

The adaption of the model is as follows:

• The pre-assessment is an index based on the average threat severity

parameter from the threat matrix

• Regions will be defined based on changes in threat parameter and pipe

dimensions/properties

• Indirect inspection results are characterised according to the mitigation matrix

• The QPRAM algorithm will be used to determine those section most likely to

contain external corrosion

APPLICATION

• Start

• Feasibility Assessment

• Data Requirements

Data is entered in tabular format as follows:

PRE-ASSESSMENT

❸ Any sections of above ground or bare pipe

No ✓ Sections of bare pipe should be assessed in accordance with guidelines contained in NACE SP0207. Similarly, above ground

sections of the pipeline cannot be assessed using the ECDA indirect inspection process and should be treated seperately.

• Pipeline Data

PRE-ASSESSMENT

• Coating Type & Age

• Pipeline Equipment

• Soil Resistivity

PRE-ASSESSMENT

• Anaerobic Soil

• DC Interference

• AC Interference

PRE-ASSESSMENT

Start Distance (m) End Distance (m) Comment

21 300

351 363

DC Interference

Please identify any known sections of the pipeline where possible DC interference may

be an issue e.g. in common wayleaves

Start Distance (m) End Distance (m) AC Source

21 250 Power lines (>10 KVAC)

301 399 Other AC Source

AC Interference

Please identify any known sections of the pipeline where possible AC interference may

be an issue e.g. HVAC power lines

• Casings

• Previous Failures (EC)

PRE-ASSESSMENT

Start Distance (m) End Distance (m) Last Inspection Date Status

11 45 01/05/2010 Short metallic

220 263 01/01/2013 Isolated

Casings

please identify the locations of any casing and their insulation state (most recent inspection)

Distance (m) Status

11 Full Root Cause Analysis

220 Repair Only

Previous Failures due to External Corrosion

please identify the locations of any failures due to external

corrosion. The model will apply a higher likelihood to all

sections within 100 m of the

A new ECDA region will be defined wherever a change in following occurs:

• Diameter

• Wall Thickness

• Pipe Type and Age

• Coating Type & Age

• Areas of Anaerobic Soil

• Areas with known AC/DC interference

• Crossings (Casings)

An index score will be assigned to each region

based on the threat severity

ECDA REGION DEFINITION

INDIRECT INSPECTION

Indirect inspection may be carried out in specified areas as per the region

definition and index score or along the whole length of the line.

4 elements of indirect inspection have been defined within the model:

• Close Interval (Protection) Survey – CIS/CIPS

• Direct Current Voltage Gradient – DCVG

• Pipeline Current Mapping – PCM

• Results of historical digs/investigations

The minimum data requirements are CIPS/CIS and DCVG or PCM

Data is entered as follows

• Coating Survey Date

• DCVG Results

INDIRECT ASSESSMENT

• PCM Results

• CIS/CIPS Date

INDIRECT INSPECTION

• CIS/CIPS Results

• AC/DC Remediation

POST ASSESSMENT

• Previous Dig Results

Once all the data has been entered, the results of the indirect inspections are

compared to the threat severity as a ratio, suggestion for dig sites will be ranked

as follows:

• High threat / poor inspection results – high

• Low threat / good inspection results - low

INDIRECT INSPECTION

Site Ranking

List Chart

INDIRECT INSPECTION RESULTS

DETAILED EXAMINATION

Data Element When Collected Field Measurement / Comment Use and Interpretation of Results

Pipe-to-soil potential Prior to coating removal.

Useful for comparison with ground surface pipe-to-soil

potential measurements.

Soil resistivity Prior to coating removal.

Related to soil corrosiveness and soluble cation

concentration of soil. Useful for comparison with results of

soil and groundwater analyses.

Soil samples Prior to coating removal.

Useful in confirming terrain conditions. Soil analysis

results can be trended in predictive model.

Groundwater samples Prior to coating removal. Chemistry results can be trended in predictive model.

Underfilm liquid pH Prior to coating removal. Useful for detemining the corrosivity of the soil

ECDA Field Investigation Data Sheet

Data Element When Collected Field Measurement / Comment Use and Interpretation of Results

Photograph of dig site Prior to coating removal.

Useful in confirming terrain conditions, coating system, and

coating condition.

Data for other integrity

analyses Before and after coating removal. Data for other analyses (e.g. SCCDA)

Assessment of coating

condition Prior to coating removal. Can be related to extent of EC found.

Assessment of coating

degradation (blisters,

disbondment, etc) Prior to coating removal. Can be related to extent of EC found.

Corrosion product data

collection After coating removal. Can assist in precise diagnosis of corrosion mechanism

Corrosion Mapping After coating removal. Required for integrity assessment


Corrosion Features:


Additional Notes


POST ASSESSMENT

Step 4: Post Assessment (Guidelines Only)

Immediate Integrity Assessment

• Category 1 - Superficial corrosion or surface rusting

• Category 2 - Estimated Repair Factor (ERF) >0.7

• Category 3 - ERF >0.9

• Category 4 - ERF ≥1

Future Integrity Assessment

• Category 1 - Failure life exceeds 10 years



• Category 4 - Failure may be imminent

Actions

• No Corrosion or Category 1 - Establish re-assessment period

• Category 2 to 3 - Engineering Critical Assessment (ECA)

• Category 4 - Immediate pressure reduction and inline inspection or hydrotest

Questions

ECDA · 2016-08-04 · Slide 3 METHODOLOGY ECDA is conducted in 4 steps Step Key Actions 1...

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Transcript of ECDA · 2016-08-04 · Slide 3 METHODOLOGY ECDA is conducted in 4 steps Step Key Actions 1...