Nader Al Otaibi - Managing SCC in Gas Pipelines

S a u d i A r a m c o

Managing SCC in Gas Pipelines

Nader Al-Otaibi Oct 4th, 2011

© Copyright 2011, Saudi Aramco. All rights reserved.

Managing SCC in Gas Pipelines

Contents

• Saudi Aramco Pipelines Network

• Part I: What is SCC?

• Part II: How to Predict and Manage SCC?

– Assessment Techniques

– Technology: EMAT Program

– Revalidation

– Case Study

• Conclusion

2

3

RIYADH

AL MADINAH

YANBU’

QAISUMAH

QASSIM

HAWTAH

KHURAIS

SHEDGUM

‘UTHMANIYAH

HARADH

SHAYBAH

DHAHRAN

ABQAIQ

QATIF

RAS TANURA

JUBAIL

SAFANIYA

HAWIYAH

Mothballed

In Operation

Rabigh

Pipelines Network Description

4

1940 1950 1970 1980 1990 2002 2009 2014

1000 1500 2500

5500

12500

18000 19300

22050

Pipelines Network Description

5

<20” 22-46” >46”

25% 40% 35% Sizes

35% 36% 29% Service

Crude Gas Product & NGL

44% 33% 23% Age

<20 Years 20-30 Year >30 Year

What is SCC?

6

SCC: what is it?

• SCC: Stress Corrosion Cracking

– Environment

– Susceptible Material

– Stress

• Typical: Older Pipelines!

• SCC Characteristics and Types:

– No significant metal loss

– Perpendicular to T.S.s

– Inter or trans-granular

– High PH vs. Near-Neutral

7

SCC Mechanism

• Active Path dissolution

– Accelerated localized

Corrosion: crack tip

– Material bulk Passive

– Inter-granular

– Active path: Grain boundary

– Stress helps open crack tip

8

• Hydrogen Embrittlement

– H2 dissolves in all materials

between atoms

– H2 weaken material

– H2 attack High tensile stresses

areas, notches and stress raisers

– H2 makes cleavage easier

SCC Types

• High PH SCC

– Carbonate/bi-Carbonate

– PH: 9.5-10

– Active path dissolution

– Inter-granular

– Sensitive to temperature (40 ᵒC)

9

• Near Neutral (Low) PH SCC

– Many species at reduced

concentrations

– PH: 6.4 (near neutral)

– Hydrogen embrittlement

– Trans-granular

Contributing Factors

• Environment

– Soil Condition

• Wet soil

• High salinity and water table (Subkha)

– Coating Conditions

• Tape wrap and Coal-tar coating

• No SCC in FBE coated pipelines

10


• Role of Stress

– Hoop stress 60% of SMYS

– Secondary loading

– Stress concentration

11


• Role of Temperature

– Distance from compressor

– 40 ᵒC

– Exponentially decrease

12

How to Predict and Manage SCC?

13

Demonstrated with a Case Study

SCC Management Program

• SCC Management Program

– Pipe Segment Susceptibility to SCC

• Identify segments

• Investigate for SCC

– Classification of Severity

• Plan and implement mitigation

• Re-assessment interval

– Manage SCC Failure

• Plan and implement mitigation

• Safe operating pressure

14

Assessment Techniques

• SCC Models

– Pipe Excavation Program

• Coating removal

• Visual inspection

• NDT

– Historical trends

– Effort vs. Accuracy

• In-Line Inspection

– Specialized tool

– Sufficiently reliable

– Recommended if coupled with verification digs

15

Assessment Techniques

• Hydro-test Program

– Fail critical and near-critical SCC

• Lower consequence

– Blunt non-mature SCC

• Might plastically deform crack tip which might accelerate failure!

– Requires Criteria

– Un-failed SCC

• Advantage to ILI

– Varying cost

• Very high if summed to pipeline outage cost

16

Lower Consequence

EMAT Technology

• Need Drives Technologies …

– Aramco runs a Master Sales Gas Network that supports growing gas local demand

– Reliable supply no interruption

– Aramco search of technology to revalidate pipelines integrity with respect to SCC

• Difficulties of hydro test

• ILI: EMAT (Electro-Magnet Acoustic Transducers)

17

EMAT Technology

• Working Principle:

– SCC detection

– Coating Disbonded

18

SCC Revalidation Criteria

• ILI Optimization Criteria

• Category A pipelines

– Pipelines History of Stress Corrosion Cracking

• Category B pipelines

– Similar Pipelines Environment (soil condition)

• Category C pipelines

– ASME B31.8S — MANAGING SYSTEM INTEGRITY OF GAS PIPELINES

– ANSI/NACE Standard RP0204 — Stress Corrosion Cracking (SCC) Direct Assessment Methodology

ASME B31.8S HCA Definition

• Identifying SCC Susceptible Areas (ASME

B31.8S)

– Operating stress > 60% SMYS

– Operating temperature > 100°F (for high pH SCC)

– Distance from compressor ≤ 20 miles (≤ 32 km)

– Pipeline age ≥ 10 years old

– Coating is other than FBE

Case Study: Gas Pipeline

• Verification Program

– Refine ILI tools findings and complement inadequacy

– Improve ILI Analysis (learning curve)

• MPI

• Shear Wave UT

• Phased Array

21


22

Section III, inspected : August 28, 2010 Summary: 4 (verified) SCC locations*

Section II, inspected: July 14, 2010 Summary: 3 (verified) SCC locations*

Section I, inspected March 14, 2010 Summary: 8 (verified) SCC locations*

40” Gas Pipeline (three segments) Built: 1971 (south to North) API 5L Gr. X52/60, Tape-Wrap Coated



23



24


• Failure Analysis

– Sample defect

– Lab Failure Analysis

– Longitudinal Cracks

– High PH

– Inter-granular Cracks

– Carbonate/bi-Carbonate

25


• Action Plan

26

Crack classification Type of repair

Open or leaking cracks >60% These cracks shall be replaced. If the replacement pipe cannot be found, then the sleeve installation option can be worked out, provided that the crack arrestor is used.

Cracks with a depth ranging from 20% to 60%

Or Colonies with more than three

linear parallel cracks

These should be repaired by installing a repair sleeve.

Cracks with a depth ranging from 10% to 20%

The cracks should be removed by grinding. The maximum length of cracks shall not exceed 24”.

Cracks with a depth less than 10%

The cracks should be removed by grinding

Tackling the Contributing Factors !

• New Coating Technologies

– Success of existing technologies

• Visco-Elastic; good track record within Saudi Aramco

– Realized Potential of some coating technologies

• Under Approval

27

To Recap

• What is SCC?

• What contributes to it?

• How to predict SCC?

• How to manage it?

• Case Study

28

SCC … Don’t Wait for it!

29

Thank You

30

Nader Al Otaibi - Managing SCC in Gas Pipelines

Technology

Transcript of Nader Al Otaibi - Managing SCC in Gas Pipelines