Possible Use of New Materials for High Pressure Linepipe Construction

7/25/2019 Possible Use of New Materials for High Pressure Linepipe Construction

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EUROPIPE. The world trusts us.

Possible use of new materials for high pressure line pipe

construction:The experience of SNAM RETE GAS and EUROPIPE onX 100 grade steel

L.Barsanti, SNAM RETE GAS SpA

H.G. Hillenbrand, EUROPIPE GmbH


2/13

Copyright 2002 by ASME 1

Proceedings of IPC:

The International Pipeline Conference

September , 2002, Calgary, Alberta, Canada

POSSIBLE USE OF NEW MATERIALS

FOR HIGH PRESSURE LINEPIPE CONSTRUCTION:

THE EXPERIENCE OF SNAM RETE GAS AND EUROPIPE ON X100 GRADE STEEL

L. BarsantiSNAM RETE GAS SpA

Viale De Gasperi 2, San Donato Milanese 20097,Milano, Italy

H.G. HillenbrandEUROPIPE GmbH

Formerstrasse 49, 40878 Ratingen,Germany

ABSTRACT

The increasing needs of natural gas, foreseen for the

next years, makes more and more important the type of

transportation chosen, both from strategic and economic

point of view. The most important gas markets will be

Northern America, Europe, Asia and Russia but the

demand shall be fulfilled also by emerging producers as

Kazakhstan, Turkmenistan and Eastern Siberia that at the

moment are developing their resources in order to be

competitive on Gas market.

In this way producers and customers will be placed

at greater and greater distances implying realization of

complex gas transportation pipeline network, when use

of LNG tankers is impossible or uneconomic.

On the base of these considerations Eni groupsponsored in 1997 a feasibility study on X100 steel, given

that, comparing different design approaches, it has been

observed that consistent savings could be obtained by

means of using high grade steel and high pressure

linepipes. In this project, involving CSM and Corus

group for the laboratory and full-scale pipes testing,

played an important part also Europipe: the pipes

producer.

No technical breakthrough, but only improvements

in the existing expertise were involved in the X100

production; consequently, the production window is verynarrow.

However optimized steelmaking practices and

processes enabled the material to reach the desired

properties: strength, toughness and weldability.

This paper is intended to present the general results

arising from this project, in terms of steel properties

(chemical composition, mechanical properties), ductile

and brittle fracture resistance (results of full scale burst

tests, West Jefferson tests) and field weldability, but

above all the know-how stored till now on high grade

steel and its possible use from a Gas company and a Pipe

maker point of view.

INTERNATIONAL SCENARIO

The energetic scenario has been changing quickly

in these last years. International studies foresaw an

increasing demand of natural gas till doubling in 2030.

This statement is based on several issues:

The availability of natural gas fields is greater thanthat of verified oil fields.

The exploitation of these reserves is yet limited.

The need of substituting polluting fuels according

Kyoto agreement with the consequent increasing useof natural gas for electric energy production with

combined cycles.

This increasing demand will be satisfied not only by

major producers (Russia, Norway, Northern America

etc.) but also by emerging countries like Kazakhstan,

Turkmenistan and Eastern Siberia, that at the moment are

developing their resources in order to be competitive on

Gas market.

Also for this reason, producers and customers will be

placed at greater and greater distances implying

construction of complex gas transportation pipelinenetwork, when use of LNG tankers is impossible or

uneconomic.

This makes high pressure natural gas

transportation via pipelines more and more interesting

for gas companies.

On the base of these considerations Eni group

sponsored in 1997 a feasibility study on X100 steel grade

because this high strength steel could give consistent

savings in terms of CAPEX comparing it to an X80 high

pressure solution. Also other gas companies tried to


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ight 2002 by ASME 2

compare transportation costs and qualities of

conventional pipeline steels in contrast to new grades like

X100.

Costs have been evaluated under several

hypothesis:

Unit steel cost has been estimated accordingtrend extrapolated from lower grades.

Costs of fittings and valves have beenconsidered as a constant portion of the total

steel cost.

Transportation costs have been evaluated as

dependent from the steel weight.

Laying costs have been analyzed completely:trenching and field bending have been

considered constant for both solutions,

instead welding costs have been divided in

two parts, one constant and the other

proportional with the thickness; moreover it

has been taken care of the possible higher

costs of consumables and of the possible

greater difficulties for welders.

The other costs (coatings, cathodic protection) have been

considered equal for both solutions.

This preliminary economic evaluation

highlighted that X100 steel high pressure pipes could

give investment costs savings of about 7% with respect

to X80 grades (See Fig.1 for costs options comparison).Other studies claim cost savings of up to 30% when X70

and X100 is compared.

Given that in a complex pipeline network

operating at high pressure, capital expenditure is very

high, it is understandable how much attractive could be

high strength steel option.

A research program was conducted by Snam

Rete Gas (on behalf of Eni group) together with

Europipe and Centro Studi Materiali. This last actor also

assured partial contribution from ECSC.

MATERIALS

To cope with market requirements for enhancing

strength Europipe put its effort to the development of

grade X100. No technological breakthroughs, such as TM

rolling and accelerated cooling which increased the

strength and toughness respectively, but only

improvements in the existing technology were involved

in the production of grade X100 plate. As a result, the

production window is quite narrow. Heat treatment of

plate or pipe is obviously not advisable.

In the last 7 years, Europipe developed three

different approaches with respect to the selection of

chemical composition.

Approach A, which involves a relatively high

carbon content, has the disadvantage that the crack arrest

toughness requirements to prevent long-running cracks,

may not be fulfilled. Moreover, this approach is also

detrimental, e.g. to field weldability. Results of that

approach are as follows:

Approach B, which was used in combination

with fast cooling rates in the plate mill down to a very

low cooling-stop temperature, results in the formation of

uncontrolled fractions of martensite in the

microstructure, which have a detrimental effect on

toughness properties of base metal and leads additionally

to the softening in the heat affected zone. This effect

cannot be adequately compensated for extremely low

carbon contents, without adversely affecting

productivity.

Heatpipe size

OD X WTC Mn Si Mo Ni Cu Nb Ti N CEIIW PCM

I 30" x 19.1 mm 0.08 1.95 0.26 0.26 0.23 0.22 0.05 0.018 0.003 0.49 0.22

Approach A

Heat

I

CVN

(20C)

DWTT-

transition

temperature

739 MPa 792 MPa 0.93 18.4% 235 - 15 C

* transverse tensile tests by round bar specimens

yield strength

Rt0.5 *tensile strength

Rm*

yield to

tensile ratio

R t0.5/ R m*

Elongation

A5*

Heatpipe size


II

Approach B

Heat

II

CVN

(20C)

DWTT-transition

temperature

755 MPa 820 MPa 0.92 17.1 % 240 - 25 C

30" x 15.9 mm 0.07 1.89 0.28 0.15 0.16 - 0.05 0.015 0.004 0.43 0.19


yield strength

Rt0.5 *tensile strength

Rm*

yield totensile ratio

R t0.5/ R m*

Elongation

A5*


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ight 2002 by ASME 3

Experience gained meanwhile indicates that

Approach C is the best choice. This approach enables the

desired property profile to be achieved through an

optimized two-stage rolling process in conjunction with a

reduced carbon content, a relatively high carbon

equivalent and optimized cooling conditions. The special

potential of the existing rolling and cooling facilities

contributes significantly to the success of this approach.

Approach C, which involves a low carbon

content, ensures excellent toughness as well as fully

satisfactory field weldability, despite the relatively high

carbon equivalent of the chemical composition. The

chemical composition should therefore be consideredacceptable for the purpose of current standardization.

Europipe already produced hundreds of tons of

grade X100 according Approach C. The latest trials were

covering the wall thickness range between 12.7 and 25.4

mm. It was demonstrated that the same steel composition

could be used and only slight changes in the rolling

conditions are necessary.

(See Fig.2 for approaches comparison)

All production results have shown that the

strength properties can be easily reached when using

round bar specimens. Yield/Tensile ratios are still high

and elongation values lower than for grade X70.. Charpy

toughness was measured in excess of 200 J but it seems

to be impossible to guarantee values in excess of 300 J

for a big project. Due to the relatively high carbon

equivalent and the high strength level, the toughness of

the longitudinal weld seam and the HAZ is limited.

BRITTLE AND DUCTILE BEHAVIOUR

One of the paramount issues in terms of safety is

the assessment of the Battelle criteria regarding ductile

and brittle behaviour of high strength steel:

The fitness of 85% shear area Battelle criterion,based on the DWT Test, to define the ductile to

brittle transition temperature.

The existing predictive formulae for arresting ductile

propagation fracture behavior.

In order to do that laboratory DWT Tests have beencompared with four full scale West Jefferson tests, for

the first point, and two full-scale burst tests have been

carried out at the CSM Perdasdefogu shooting Test

Station in Sardinia.

Brittle Fracture

In these last years the Battelle approach for brittle

fracture assessment has been confirmed on large

diameter pipes built in steel grades from API X65 to X80.

In order to verify these results for the predictionof full scale behaviour in X100 steel pipes, the ductile to

brittle transition curves have been measured and the

results compared with those obtained by four West

Jefferson (WJ) tests carried out on two 56x19.1mm and

two 36x16mm samples; the test temperatures have been

chosen in order to have both full ductile and transition

behaviour.

The ductile/brittle transition curves have been

measured interpolating data from both Charpy V and full

thickness DWTT specimen with a pressed notch in

accordance with the API RP 5L3 Recommendations.The WJ tests were carried out by CSM at a

pressure equivalent to about 72% of the SMYS. The tests

were performed using water as a pressurising medium,

with a small percentage of air (about 5 %) to assure

enough energy to propagate the fracture.

In Figs. 3-4 the transition curves obtained by

DWT tests and Charpy V tests are compared with the WJ

tests results. It can be noted the Battelle criterion is

completely fulfilled and the DWT Test allows the

determination of the pipe transition temperature in a

Heatpipe size


III

Approach C

Heat

III

yield strengthRt0.5 *

tensile strength

Rm*

yield to

tensile ratioRt0.5/ Rm*

ElongationA5*

CVN

(20C)

DWTT-

transition

temperature

737 MPa 800 MPa 0.92 18 % 200 J - 20 C

56" x 19.1 mm 0.07 1.90 0.30 0.17 0.33 0.20 0.05 0.0180.005 0.46 0.20

IV

V

36" x 16.0 mm 0.06 1.90 0.35 0.28 0.25 - 0.05 0.018 0.004 0.46 0.19

36"x12.7 - 25 mm 0.06 1.93 0.32 0.30 0.24 - 0.05 0.018 0.005 0.46 0.19

IV 752 MPa 816 MPa 0.92 18 % 270 J - 50 C

V 767-799 MPa 796-836 MPa ~0.94 15-18 %200-

270 J

~-60 - -10C**


**-60C for WT 12.7mm -10C for WT 25mm


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ight 2002 by ASME 4

conservative way, even if the full-scale results show a

little spread.

Ductile fracture propagation

In order to assess the existing predictive

formulae for arresting ductile propagation fracture

behavior of API X100 pipeline, two full-scale burst tests

have been carried out at the CSM Perdasdefogu shooting

Test Station in Sardinia.

Seven pipes have been used for each full-scale

burst test: one initiation pipe, six test pipes and two

reservoirs to avoid the reflection of the pressure waves

and their interaction with fracture propagation.

In Figs. 5-6 the two tests lay-out, Charpy V shelfenergy at room temperature and predictive Battelle

formulae fracture behaviour, in terms of arrest (A) and

propagation (P) event of a running crack, are shown.

The main full-scale burst tests conditions were:

1 test 2 test

Nominal diameter 56 36

Nominal thickness 19.1 mm 16 mm

Pressurizing medium air air

Test pressure 126 bar 181 bar Usage Factor 68% 75%

In order to collect every data necessary for analysis

was installed instrumentation fit for purpose: timing

wires, internal pressure transducers and thermocouples.

The paths followed by the two fractures are shown

also in figures 5 and 6.

1 test

After the initiation, obtained by means of anexplosive shaped charge, the fracture propagated

on the upper pipe generatrix at a very high speed

in both test line sides.

West side : The crack, after the initiation,

propagated in the first pipe, but in correspondence

of the girth weld with the adjacent pipe it split in

two causing the severance of the test line and the

ejection of the pipe itself. So no information about

West test side were available.

East side :The crack propagated through the initiation

pipe and arrested at the end of the third pipe (260 J

of Charpy V energy) in correspondence of the girth

weld.

2 testIn this case two propagations and two clear arrests

were observed.

West side: the crack, after initiation, propagated with

a maximum speed of about 310 m/s and arrested

eventually in the last pipe (297 J of Charpy V energy)

after about 1.5 2 meters.

East side: the crack, after the initiation, propagated

with a maximum speed of about 300 m/s and entered in

the following pipe (259 J of Charpy V energy) where itarrested after about 5 meters.

On the base of these results, especially for the

second burst test, where we had two valid arrests, it can

be said a toughness level of about 260 J is sufficient to

arrest a long ductile propagating fracture in the tests

conditions chosen.

To tell the truth, on the west side, it arrested in a pipe

characterised by 297 J, but considering that in the

previous pipe (252 J ) we had a lower DWTT energy and

that fracture arrested at the very beginning of the last

pipe, we can subscribe previous statement.

This result is in agreement with previous tests

performed on high grade/high hoop stress pipelines.

Therefore in order to use the conventional Battelle Two

Curves Approach, based on CharpyV values, several

correction factors according the tests should be used: 1.5

for the first test and 1.7 for the second one (see Fig. 7).

FIELD WELDABILITY

One of the most important issue in gas transportation

industry is not only development of the steel but alsoappropriate welding procedures.

So in the present paper will be presented results obtained

by means of laboratory and full scale concerning three

main items:

Review on commercial availability of consumables

with suitable chemical composition and mechanical

properties in terms of tensile strength and hardness

to fulfil overmatching criterion ;

Definition of minimum welding requirements withreference to pre-heating temperatures in order to


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ight 2002 by ASME 5

avoid cold cracking problems. Execution of test girth

welds both with manual (SMAW) and mechanised

(GMAW) welding methods in order to collect as

much information as possible about every technical

problems arising from full scale welding of high

grade steel.

In order to define suitable preheating temperatures

laboratory tests have been performed: Implant and

Tekken type.

Implant tests, cause of the more severe costraint

conditions, gave temperatures too high in order to be

applied in field instead Tekken tests gave more

interesting results as can be observed in the following

table.

ROOT ELECTRODE IMPLANT TEKKEN

Basic el. E10018 200C 100C

Cellulosic el. E9010 250C 200C

Cellulosic el. E6010 n. d. 150C

Table 1: Minimum Preheating Temperatures established

from laboratory tests

Once chosen pre-heating temperatures two field welding

trials have been performed on two pipes (56"x19mm and36"x16mm) investigating on both most spread

techniques: GMAW (PASSO system) and SMAW.

In the tables 2-3 can be observed the welding procedures

followed for each geometry.

Both techniques gave good results even if GMAW

resulted less problematic because of its lower impact on

welders skill and training, in Fig.8-9 the appearance of

welds can be observed for each technique.

CONCLUSIONS

On the base of last previsions, gas quantities tobe transported will increase significantly making more

and more attractive natural gas transportation by means

of long distance high pressure pipelines.

X100 steel could be a material suitable for this

type of construction: it could combines high pressure and

reduced thickness of the pipe in order to minimize

CAPEX. But it will be necessary to reassess and redefine

some of the material requirements

Research developed by Snam Rete Gas, Europipe

and CSM showed it was possible also from the point of

view of safety: main results obtained are the following.

The pipe material shows a full ductile fracturebehavior down to -20C.

The validity of the Battelle criterion, in order toevaluate the full scale pipe ductile to brittle transition

temperature, has been assessed.

The toughness characteristics of the API X100 steelgrade line pipes, in terms of Charpy V energy,

proved enough to warrant the arrest of a long

running shear in the test conditions chosen.

As regard the correction factor to be used with the

Battelle two curves approaches for the API X100grade steel pipes tested in these burst tests, two

different correction factors must be used (1.5, 1.7).

For the weldability issue it is surely possible

welding X100 pipes with both manual and mechanised

technique. Best results have been obtained with the

mixed procedure which allowed to decrease cold

cracking susceptibility without any meaningful softening

of the joint. However the most important item is the

welders skill.

On the other hand GMAW gave good resultswithout any problems and this seems very promising

considering the type of application suitable for X100

pipes.

After results of this research and those that will

arise from Demopipe project (demonstrative project on

behalf of EPRG about X100 steel line pipes) the

following step could be creating specification and

codification of the steel.

ACKNOWLEDGMENTS

This research was performed also with the help

of Esab and Bohler for the consumables supplying and

with the collaboration of Bonatti and Sicim for pipe

welding.


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ight 2002 by ASME 6

REFERENCES

q H.-G. Hillenbrand et al. H igh Strength L ine Pipe for

Project Cost Reduction, World pipelines, Vol.2 No.1,

2002

q L. Barsanti, H.G. Hillenbrand Production and FieldWeldability Evaluation of X100 Line Pipe PRCI-EPRGMeeting, New Orleans Louisiana USA, 2001.

q G. Mannucci, G. Demofonti, L. Barsanti, H.G. Hillenbrand,D. Harris FRACTURE PROPERTIES OF API X100 GAS

PIPELINE STEELS PRCI-EPRG Meeting, New OrleansLouisiana USA, 2001.

q G. Mannucci, G. Demofonti, L. Barsanti, C.M. Spinelli, H.G.Hillenbrand, Fracture behaviour and defect evaluationof large diameter, HSLA steels, very high pressure

linepipesIPC, Calgary Alberta Canada, 2000.q Mannucci, G., Demofonti, G., Galli, M.R., Spinelli, C.

Structural Integrity of API 5L X70-X80 Steel GradePipeline for High Pressure Long Distance TransmissionGas Lines 12

th EPRG/PRCI Biennial Joint Technical

Meeting on Pipeline Research. Groningen, 1999, paper 13.

q G. Demofonti, G. Junker, V. Pistone TransitionTemperature Determination for Thick-Wall line Pipe ,

11th

EPRG/PRCI Biennial Joint Technical Meeting onPipeline Research, Arlington, 1997, paper 5.

q H.G. Hillenbrand et al. Development of linepipe in gradeup to X100, 11

thEPRG/PRCI Biennial Joint Technical

Meeting on Pipeline Research, Arlington, 1997, paper 6.

q API RP5 L3, Third edition February 1996,Recommendation Practice for Conducting Drop Weigth

Tear Tests on Line Pipe.

q Maxey, W. Fracture Initiation, Propagation and arrestPipeline Research Committee of the American Gas

association. 5th

Symposium on Line Pipe Research.Houston, 1974.

q Demofonti, G., Pistone, P, Re, G., Vogt, G., Jones, D.G.

EPRG Recommendation for Crack Arrest Toughness forHigh Strength Line Pipe Steels. 3R International 34,

1995.

q J.F. Kiefner, W.A. Maxey, R.J. Eiber, A.R. Duffy Failure

stress levels of flaws in pressurised cylinders ASTM STP536 (1973).


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ight 2002 by ASME 7

APPENDIX

Fig.1: Comparison between costs associated to X80 and X100 options for the same project construction.

Fig.2: Comparison between A, B, C approaches in order to obtain X100 steel target.

0

500

1000

1500

2000

2500

3000

API 5L X80 API 5L X100

C

osts

[USD/m]

Common costs

Welding

Laying

Materials


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ight 2002 by ASME 8

Fig.3: Comparison between WJ and DWTT results on pipe 56x 19mm

Fig.4: Comparison between WJ and DWTT results on pipe 36x 16mm

0

10

20

30

40

50

60

70

80

90

100

-160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (C)

Brittlefracture(%)

0

10

20

30

40

50

60

70

80

90

100

ShearArea(%)DWTT

Charpy V

WJ Results

Battelle Criterium

0

10

20

30

40

50

60

70

80

90

100

-160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (C)

Brittlefracture(%

0

10

20

30

40

50

60

70

80

90

100

ShearArea(%)

DWTT

Charpy V

WJ Results

Battelle Criterium


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ight 2002 by ASME 9

X100, 56" x19.1mm Burst Test L ayout

WEST Severance EAST

Reservoir Reservoir

Initiation pipe

Pipe number 846020 846038 846129 846113 846058 846157 846061

Tensile and YS (MPa) 707 719 780 773 755 663 722 Fracture

toughness TS (MPa) 766 766 832 858 829 762 778 Path

properties Y/T ratio 0.92 0.94 0.94 0.90 0.91 0.87 0.93

CharpyV (Joule) 271 245 200 151 170 263 284

Arrest predicted CharpyV toughness values with P=126 bar (hoop stress=469 MPa)

Battelle simpl. formula 188 J A A A P P A A "A" = predicted arrest

Battelle Two Curve appr. 176 J A A A P P A A "P" = predicted propagation

Fig.5: X100, 56x19.1mm burst test layout and results

X100, 36" x16mm Bur st Test L ayout

WEST EAST

Reservoir Reservoir

Initiation pipe

Pipe number 99447 99458 99460 99461 99456 99457 99446

Tensile and YS (MPa) 724 750 711 709 761 740 766 Fracture

toughness TS (MPa) 780 819 797 802 844 811 826 Pathproperties Y/T ratio 0.93 0.92 0.89 0.88 0.90 0.91 0.93

CharpyV (Joule) 297 252 202 165 259 253 274

Arrest predicted CharpyV toughness values with P=181 bar (hoop stress=517 MPa)

Battelle simpl. formula 186 J A A A P A A A "A" = predicted arrest

Battelle Two Curve appr. 154 J A A A A A A A "P" = predicted propagation

Fig.6: X100, 36x16mm burst test layout and results


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ight 2002 by ASME 10

Actual CharpyV energy Vs. Predicted by Battelle Two Curve Approach

[CSM Database 10 tests: g rade=API X80, OD=42-56"; thi ck=16-26mm , P=80-161bar,

Hoop s tress=336-440MPa, air and natural gas (not rich )]

0

50

100

150

200

250

300

350

0 50 100 150 200

Predicted CharpyV energy by Battelle Two Curve Approach (J)

ActualCharpyVenergy(J)

Database Arrest

Database Propagation

X100 56"x19.1mm Arrest

X100 56"x19.1mm Propagation

X100 36"X16mm Arrest

X100 36"x16mm Propagation

1:1.7

1:1

1:1.5

1:1.43

Fig.7: Actual vs. Predicted CharpyV energy (Battelle Two Curve Approach) for high-grade steel linepipes (CSM

database)

Fig.8: Appearance of a weld (test n.3 SMAW 36x16mm, mixed weld joint, vertical up welding)


12/13


Fig.9: Appearance of a weld (test n.10 GMAW 36x16mm, wire A 5.28 ER 100 S-G)

Table 2: Types of welding procedures, wires and electrodes used for 56x19mm pipe.

Snam specificationsTest

N.Root pass

(AWS)

Hot pass

(AWS)Filler

(AWS)

1 E6010 E9010 E10018-G

2 E8018-G E10018-G E10018-G

7 E6010 E10018 E10018Sal 1: SMAW Line

welding

8 E7016 E10018 E10018-G

3 E6010 E10018-G E10018-GSal 2: SMAW

Joining welding

(es: tie in) 4 E6010 E9010 E10018-G

9 ER 100 S-G / /

5 ER 90 S-G / /Sal 1: GMAW

(PASSO type)

6 ER 100 S-G / /


13/13


Table 3: Types of welding procedures, wires and electrodes used for 36x16mm pipe.

Sna m specif icationTest

N.

Root pass

(AWS)

Second

pass

(AWS)

Filling

(AWS)

1 E6010 E11018-G E11018-G

2 E8018-G E10018-G E10018-GSal 1: SMAW (line

welding)

6 E6010 E10018 E10018

3 E6010 E10018-G E10018-G

4 E6010 E10018-G E10018-GSal 2: SMAW

(linking welding )

9 E7016 E10018 E10018-G

5 ER 90 S-G / /Sal 1: GMAW

(PASSO type) 10 ER 100 S-G / /

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Possible Use of New Materials for High Pressure Linepipe Construction

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