CNPC TUBULAR GOODS RESEARCH INSTITUTE · Gas transmission line is over 100,000km in China ... Coupons: the samples were machined from X80 Φ 1219×18.4 (LSAW), one group without residual

中国石油集团石油管工程技术研究院

C N P C T U B U L A R G O O D S R E S E A R C H I N S T I T U T E

Gazprom VNIIGAZ IV International Scientific and Technical Seminar

Improvement of Reliability of Main Gas Pipelines Subject to Stress Corrosion Cracking

Introduction

TGRI is directly affiliated to CNPC, founded in 1981 in City of Xi’an, the only one research institute

focusing on tubular goods research and technology in China;

80% with Master Degree under the age of 40, 46 with PhD degree, one CEA and 6 national and

provincial experts.

Pipeline & OCTG

Material science and engineering

Mechanics and fracture control

Corrosion and protection

Failure analysis

Safety assessment and risk management

Full scale testing

NDT and inspection

Oil and Gas Field

Pipeline Operation Company

Steel & Pipe Company

Petroleum chemical Company

Refinery

Tools Company

……

CNPC＋SINOPEC+CNOOC

Where We Are?

Great Wild Goose Pagoda

Terra Cotta Warriors

TGRI’s Roles

Tubular Goods

Engineering

Quality & Inspection Center

Innovative R&D Center

Tubular Goods Engineering Service

Technical Service Center

International Communications & Collaborations

C-FER (Canada)

TRANSCANADA (Canada)

CSM (Italy)

Ohio University (US)

STRESS (US)

BATTELLE (US)

EMCC (US)

MICROALLOYING(US)

CBMM(BRAZIL)

TWI (UK)

Nippon Steel (Japan)

JFE (Japan)

TENARIS (Argentina)

V&M、GL (Germany)

POSCO (South Korea)

International Conference hosted by TGRI

Ultra High Strength Line Pipe Technology International Conference

High strength Line Pipe Technology and Application International Conference

Pipeline and Material International Conference

Tubing String and Material International Conference

High strength Line Pipe Technology and Application International Conference

Tubing String and Material International Conference

International Conference for Petroleum Tubular Goods, Equipment and Materials

International Conference for Petroleum Tubular

Goods, Equipment and Materials was held in April

annually, which was co-hosted by TGRI and API. Hope

to meet you in 2019 in Xi’an.

Key Facilities at TGRI

With capacity of testing metallic materials, non-metallic materials, composite materials

Full-scale equipment for testing tubing/casing, Line pipe, valves, tools.

Key Facilities at TGRI (cont.)

Research Background

Gas transmission line is over 100,000km in China

1996—OD660 X60 6.4MPa—Shaanjing pipeline

2001---OD1016 X70 10MPa---West-East Pipeline I

2007---OD1219 X80 12MPa---West-East Pipeline II

2017---OD1422 X80 12MPa---Sino-Russia East line

X90/X100 are developed and trial section are planning

Gas pipeline from Middle Asia Gas pipeline from Russia

Gas pipeline from Myanmar

OUTLINE

Effect of small-amplitude stress fluctuation on high grade pipeline SCC 1

2

Effect of residual stress on high grade pipeline SCC 3 3

4 4

Effect of cathodic Protection on high grade pipeline SCC

Pipeline research activities at TGRI

Experimental

Coupons: the samples were machined from Φ 1219×18.4 mm LSAW X80 pipe, one group was cut from pipe

body and one group from weld joint.

Pre-crack: The depth of wire-cut is 2mm, the length of pre-crack is 1mm, length of residual ligament is 5mm.

Applied load: The Maximum applied load is 100%δs and 85%δs, R ratio is 0.85 and 0.75, the frequency is 0.02Hz.

Solution: NS 4 solution, purged with 5%CO2+95%N2.

Schematic diagram of pre-crack sample Instron8810 for fatigue test

Composition KCl NaHCO3 CaCl2·2H2O MgSO4·2H2O pH

Content (mg/l) 122 483 181 131 6.8

100%δs

100%δs×0.75

85%δs

85%δs×0.75

100%δs

100%δs×0.85

85%δs

85%δs×0.85

Condition 1: S100R75

Experimental: Small-amplitude stress fluctuation

Condition 2: S85R75

Condition 3: S100R85 Condition4: S85R85

The crack propagation is directly associated with stress ratio and stress level, the crack propagation

rate (da/dN) is in order: S100R75>S85R75>S100R85>S85R85. .

Results and discussion

Influence of small-amplitude stress fluctuation on cracking behavior of X80 weld joint


Test duration is 336h Crack propagation rate is da/dN=2.23×10-5mm/N

Condition1: S100R75 Condition2: S85R75


Test duration is 180h Crack propagation rate is da/dN is 1.98×10-4mm/N

Condition3: S100R85 Condition4: S85R85


Fracture! Fracture!

Influence of small-amplitude stress fluctuation on cracking behavior of X80 weld joint

100%δs 85%δs

Condition 1: Weld joint 100%δs Condition 2: Weld joint 85%δs

100%δs 85%δs

Condition 3: Pipe body 100%δs Condition 4: Pipe body 85%δs

Experimental: Static stress

Weld Joint Weld Joint


Influence of static stress on cracking behavior of X80 weld joint

Weld joint 100%δs Weld joint 85%δs Pipe body 100%δs Pipe body 85%δs

Weld joint 100%δs Weld joint 85%δs Pipe body 100%δs Pipe body 85%δs

The crack propagation is directly associated with stress level and material type, the crack propagation rate (da/dN) is in order: Weld joint 100%δs>> Weld joint 85%δs >Pipe body 100% δs> Pipe body 85% δs .



Condition1: Weld joint 100%δs Condition2: Weld joint 85%δs



Condition3: Pipe body 100%δs Condition4: Pipe body 85%δs


Influence of static stress on cracking behavior of X80 weld joint

Summary-1

Stress ratio value has the greatest influence on crack propagation rate of LSAW X80 pipeline, the

crack propagation rate increased with the decreasing of stress ratio value.

The crack propagation rates of S100R75, S85R75, S100R85, S85R85 are in orders of 1.98×10-4

mm/N>1.27×10-4 mm/N>2.23×10-5 mm/N>8.3×10-6 mm/N。

Small-amplitude stress fluctuation

Static Stress

Under static stress of 100%δs, the crack propagation rate of weld joint is four times of pipe body;

Under static stress of 85%δs, the crack propagation rate of weld joint is three times of pipe body.

The SCC susceptibility of LSAW X80 pipe weld joint is higher than that of pipe body.

Small-amplitude stress fluctuation VS Static Stress

Compared to static stress, the small-amplitude stress fluctuation has enhanced effect on crack

propagation rate on LSAW X80 Pipeline.

OUTLINE


2


4 4



Experimental

Coupons: the samples were machined from X90 Φ 1219×16.3 (LSAW) and X90 Φ 1219×16.3mm (SSAW), one

group was cut from pipe body, one group from weld joint (LSAW), and one group from weld joint (SSAW).

Test condition: strain rate is 10-6mm/s, applied cathodic potentials are OCP, -1000mV, -1200mV (SCE).


Schematic diagram sample Instron8810 for fatigue test

Composition KCl NaHCO3 CaCl2·2H2O MgSO4·2H2O pH

Content (mg/l) 122 483 181 131 6.8


SCC susceptibility of X90 (LSAW)

Pipe body

Weld joint

The strain after fracture(δ) and percentage reduction of area (Ψ) decreased with the negative shift of applied potential, while SCC susceptibility in terms of Iδ and IΨ increased with the negative shift of applied potential.

OCP -1000 -1200

OCP -1000 -1200



Pipe body Weld joint Pipe body Weld joint

OCP -1000 -1200 OCP -1000 -1200

According to the values of Iδ and IΨ, SCC susceptibility of weld joint is higher than that of pipe body with the negative shift of applied potential.



Pip

e b

od

y

Weld

jo

int

In air OCP -1000mV -1200mV


SCC susceptibility of X90 (SSAW)

Pipe body

Weld joint

The strain after fracture(δ) and percentage reduction of area (Ψ) decreased with the negative shift of applied potential, while SCC susceptibility in terms of Iδ and IΨ increased with the negative shift of applied potential.

OCP -1000 -1200

OCP -1000 -1200



Pipe body Weld joint Pipe body Weld joint

OCP -1000 -1200 OCP -1000 -1200

According to the values of Iδ and IΨ, SCC susceptibility of weld joint is higher than that of pipe body with the negative shift of applied potential.



Pip

e b

od

y

Weld

jo

int

In air OCP -1000mV -1200mV

Summary-2

The strain after fracture(δ) and percentage reduction of area (Ψ) decreased with the negative shift of

applied potential, while SCC susceptibility in terms of Iδ and IΨ increased with the negative shift of

applied potential.

SCC susceptibility of weld joint is higher than that of pipe body with the negative shift of applied

potential.

X90 (LSAW)

X90 (SSAW)

X90 (LSAW) VS X90 (SSAW)

The susceptibility of X90 (SSAW) is somewhat higher than that of X90 (LSAW).

The strain after fracture(δ) and percentage reduction of area (Ψ) decreased with the negative shift of

applied potential, while SCC susceptibility in terms of Iδ and IΨ increased with the negative shift of

applied potential.

SCC susceptibility of weld joint is higher than that of pipe body with the negative shift of applied

potential.

OUTLINE


2


4 4



Experimental

Coupons: the samples were machined from X80 Φ 1219×18.4 (LSAW), one group without residual stress, and

three groups with different levels of residual stress.

Test method: FPB (90%δs ,70%δs, and 50%δs ) and SSRT (strain rate is 4.57×10-6m/s to 5.67×10-5m/s).

Residual stress test: SHIMADZU XRD-7000.


Preparation of FPB sample with residual stress Preparation of SSRT sample with residual stress


Residual stress of X80 (LSAW)

130° 150° 170°

Residual stress of pipe body:210~236MPa

Residual stress of weld joint: 250~318MPa






SCC susceptibility of X80 (LSAW)-FPB Method

Applied stress Residual stress Samples Results

50%σs

130°Pre-deformation Pipe body 2 Weld joint 2

No crack


No crack


No crack

No Pre-deformation Pipe body 2 Weld joint 2

No crack

70%σs


No crack


No crack


No crack


No crack

90%σs


No crack


No crack


No crack


No crack

No SCC was observed on X80 (LSAW) with

different levels of residual stress(130°, 150°,

170°) and applied stress (50%σs, 70%σs,

90%σs).


SCC susceptibility of X80 (LSAW)-SSRT Method

Pipe Body Weld Joint

① 130°-1# -NS4 ⑥ 170°-2# -NS4

② 130°-2# -NS4 ⑦ No pre-deformation-1# -NS4

③ 150°-1# -NS4 ⑧ No pre-deformation-1# -NS4

④ 150°-2# -NS4 ⑨ No pre-deformation-1# -Air

⑤ 170°-1# -NS4 ⑩ No pre-deformation-1# -Air

① 130°-1# -NS4 ⑥ 170°-2# -NS4

② 130°-2# -NS4 ⑦ No pre-deformation-1# -NS4

③ 150°-1# -NS4 ⑧ No pre-deformation-1# -NS4

④ 150°-2# -NS4 ⑨ No pre-deformation-1# -Air

⑤ 170°-1# -NS4 ⑩ No pre-deformation-1# -Air

Strain (%) Strain (%)

Stre

ss (

MP

a)

Stre

ss (

MP

a)


SCC susceptibility of X80 (LSAW)-SSRT Method

Samples Test Time Ratio Strain Ratio PRA Ratio Fracture Energy Ratio

130°Pre-deformation in NS4 0.914 0.727 0.598 0.717



No Pre-deformation In NS4 0.994 0.982 0.663 1.020

No Pre-deformation In air 1.000 1.000 1.000 1.000

Samples Test Time Ratio Strain Ratio PRA Ratio Fracture Energy Ratio




No Pre-deformation In NS4 0.967 0.883 0.740 0.837

No Pre-deformation In air 1.000 1.000 1.000 1.000

Pip

e b

od

y

Weld

jo

int

SCC susceptibility of X80 (LSAW) increased with residual stress introduced, weld joint is more susceptible to SCC

under residual stress condition.

Summary-3

No SCC was observed on X80 (LSAW) with different levels of residual stress(130°, 150°, 170°) and

applied stress (50%σs, 70%σs, 90%σs).

SCC susceptibility of X80 (LSAW) increased with residual stress introduced, weld joint is more

susceptible to SCC under residual stress condition.

OUTLINE


2


4 4



High performance pipeline R&D:

Material selection and microstructure

Fracture control: low temperature brittle fracture, ductile fracture arrest.

Strain based design, high deformation pipeline and strain aging

Corrosion and SCC control

DC/AC stray current induced corrosion

Inspection and integrity assessment

Standard and specifications



High strength pipeline(X70 and X80): from a follower to leader in world wide

X70/X80 high strength pipe applied in large diamete

r high pressure pipeline project, West-East Gas Pipeli

ne I and II.

Pipe grade from X52 to X80, diameter from Φ508 to

Φ1219mm, and pressure from 6.4MPa to 12MPa.

Greatly reduced pipeline purchase and construction

cost, 10 billions RMB was saved in West-East Gas Pip

eline II.


Crack propagation and arrest: full-scale burst test

X80 pipelines (48”) X80 pipelines (56”)

Full-scale pipe burst test field in China


Crack propagation and arrest: full-scale burst test

Field image of parallel pipeline and burst pipeline Deformation measurement on

parallel pipeline

Influence on parallel pipeline from full-scale burst test of main pipeline


Tensile strain capacity assessment

Strain field on crack tip Crack driving force (CTOD)

Tensile strain capacity assessment (tangency approach)


CWP specimens

Fracture appearance

Load/CMOD vs. strain

R-curve from CWP test

Tensile strain capacity assessment: Curved wide plate tensile test


Tensile strain capacity assessment: Single-notched tensile test

Multiple specimen or single specimen/unload

compliance method.

SY/T 7318.2-2016 Standard test method for

special properties of line pipe – Part 2:

single-edge notched tensile test (SENT).

Single specimen/unload compliance method

Multiple specimens method

Fracture growth path


Tensile strain capacity assessment: Sino-Myanmar pipelines

Crack Driving Force

Tensile Strain assessment by tangency approach

(3.8% for WM, 5.4 for FL)

Test No. Peak stress

(MPa) Strain

（%,LT-1）

Strain （%,LB-1）

WM 631 4.07 3.89

FL 640 4.86 4.60

Test No. Remote strain

(%) Total crack growth

（mm）

CMOD （mm）

WM 3.89 10.1 3.30

FL 4.60 5.41 6.66


Sino-Russia East pipeline 1422mm X80 pipe and induction heating bend pipe

Developed D1422×33.8mm X80 induction heating bend pipe used in low temperature (-

45℃), composition design, fire bending, smelt and rolling technologies.

0.6%-1.0%Ni-based micro-alloy steel X80 three-way elbow was developed, which is 58mm

in thickness using in low temperature of -45℃, the toughness and strength is satisfied

with the standard requirements for Sino-Russia East pipeline.

The variation of strength and impact energy of DN1400×1400×1200 X80 three-way elbow (68mm in thickness)

If you would like to learn more about TGRI, please visit http://tgrc.cnpc.com.cn/

Offering Energy Creating Harmony

CNPC TGRI hopes to collaborate with GAZPROM VNIIGAZ in

future, share pipeline research ideas and experiences.

Documents

CNPC TUBULAR GOODS RESEARCH INSTITUTE · Gas transmission line is over 100,000km in China ... Coupons: the samples were machined from X80 Φ 1219×18.4 (LSAW), one group without residual