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Experimental Study and Theoretical Modelling of Pipeline Girth Welding

By

Krzysztof Borkowski

B. Eng.

A thesis submitted for the degree of Master of Philosophy at the

School of Mechanical Engineering

The University of Adelaide

Australia

Submitted: December 2014

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Abstract

The thermal field induced by arc welding has been the subject of numerous

experimental, analytical and numerical studies in the past. However, few studies have

focused on the effects of the local geometry and pipeline welding procedure on the transient

thermal field at or near the vicinity of the weldline. The local geometry and welding

procedures are often simplified in computational or analytical studies and normally

disregarded in quantitative assessments. The objective of this thesis is to evaluate the

significance of these effects in order to understand their possible influence on the weld

quality, pipeline integrity and weldability. In this thesis, simplified analytical models are

developed, compared against outcomes from previous investigations, and validated with data

obtained from a full-scale experimental study completed by the candidate. The conducted

research indicates that the effects of the weld preparatory geometry (which is within the

industry acceptable variations) and pipeline welding procedures might have a significant

impact on the thermal history, specifically at low heat inputs and no preheats, which are

characteristic for pipeline girth welding. Therefore, the account of these effects is very

important for the adequate evaluation of the weld quality and, potentially, the pipe integrity.

The results presented in this thesis can be utilised in the quality control, advanced modelling

procedures and other activities directed towards the further improvement of pipeline

construction procedures.

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Thesis Declaration

I certify that this work contains no material which has been accepted for the award of

any other degree or diploma in my name, in any university or other tertiary institution and, to

the best of my knowledge and belief, contains no material previously published or written by

another person, except where due reference has been made in the text. In addition, I certify

that no part of this work will, in the future, be used in a submission in my name, for any other

degree or diploma in any university or other tertiary institution without the prior approval of

the University of Adelaide and where applicable, any partner institution responsible for the

joint-award of this degree. I give consent to this copy of my thesis, when deposited in the

University Library, being made available for loan and photocopying, subject to the provisions

of the Copyright Act 1968. I also give permission for the digital version of my thesis to be

made available on the web, via the University’s digital research repository, the Library

Search and also through web search engines, unless permission has been granted by the

University to restrict access for a period of time.

Krzysztof Borkowski,

9th

December 2014

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Acknowledgements

I would like to thank A/Prof. Kotousov and A/Prof. Ghomashchi for their support and

guidance with this research project. Many thanks to Pascal Symons and Scott Letton from the

workshop for their fabrication and welding expertise as well as Alison-Jane Hunter for her

help with the editing of this thesis.

This research project was funded by the Energy Pipeline CRC and supported through

the Australian Government Cooperative Research Centre Program. The cash and In-kind

support from the APIA-RSC is gratefully acknowledged. I would also like to thank EPCRC

CEO, Prof. Valerie Linton and our industry advisors, Frank Barbaro, Leigh Fletcher, Chris

Jones, John Piper and Cameron Dinnis.

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Nomenclature

T - Temperature [°C]

V - Voltage [V]

I - Current [A]

η - Arc efficiency

Q - Power Input [W]

v - Weld travel speed [m s-1

]

h - Plate thickness [m]

λ - Thermal conductivity of steel [W m-1

K-1

]

κ - Thermal diffusivity of steel [m2

s-1

]

cp - Specific heat [J kg-1

°K-1

]

ρ - Density [kg m-3

]

b - Dimensionless heat transfer factor

T0 - Initial temperature [°C]

T∞ - Ambient temperature [°C]

Tph - Preheat temperature [°C]

𝑥 and 𝑦 - Rectangular coordinates [m]

r - Radial coordinate in polar coordinate system, r = √x2 + y2 [m]

w - Coordinate along the weld direction, w = x − vt [m]

ξ - Moving radial coordinate in polar coordinate system, ξ = √w2 + y2 [m]

rz - Radial coordinate in cylindrical coordinate system, rz = √w2 + y2 + z2 [m]

rn - Function, rn = √w2 + y2 + (2nh − z)2 [m]

rn′ - Function, rn

′ = √w2 + y2 + (2nh + z)2 [m]

Uw - Heat transfer coefficient of weld surface [W m-2

K-1

]

x

Up - Heat transfer coefficient of plate surface [W m-2

K-1

]

d - Heat transfer/conductivity coefficient [m-1

]

dw - Heat transfer/conductivity coefficient of weld, dw = Uw λ⁄ [m-1

]

dp - Heat transfer/conductivity coefficient of plate, dp = Up λ⁄ [m-1

]

uwn - Eigenvalues satisfying characteristic equation,

tan(uwn) = 2hduwn (uwn2 + h2dw

2 )⁄

upn - Eigenvalues satisfying characteristic equation,

tan(upn) = 2hdupn (upn2 + h2dp

2)⁄

Awn - Coefficients of Fourier series, Awn = uwn2 (uwn

2 + h2dw2 + 2hdw)⁄

Apn - Coefficients of Fourier series, Apn = upn2 (upn

2 + h2dp2 + 2hdp)⁄

qp - Dimensionless plate heat reflection rate

R - Pipe radius [m]

t8/5 - Time it takes for the weld seam and adjacent heat-affected zone to cool from

800 °C to 500 °C

t100 - Time it takes for weld seam and adjacent heat-affected zone to reach 100 °C

List of Figures

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List of Figures

Figure 1: V-groove preparatory joints as specified in (a) AWS D10.11M.D10.11:2007 and (b)

AS2885.2-2007 standards. ......................................................................................................... 2

Figure 2: A simplified illustration of field pipeline girth welding procedure............................ 4

Figure 3: Pipe-line girth welding in field conditions (Miller Welding Equipment, 2014). ....... 5

Figure 4: SMA welding process. ............................................................................................... 8

Figure 5: Root, Hot, Filling and Capping passes in a pipe weld joint. ...................................... 9

Figure 6: Pipeline construction (The Joyce Road Neighbourhood, 2012)............................... 10

Figure 7: Pipeline construction procedure (Dunstone, 2004). ................................................. 11

Figure 8: Typical temperature history of a weld and characteristic cooling times .................. 13

Figure 9: Prediction of dominant microstructure from temperature histories (solid lines) using

a CCT diagram for X70 (Onsoien et al., 2009). TH 1 leads to a Martensite microstructure

with VH 340 and TH 2 facilitates a Bainitic microstructure, which is less brittle (VH 212). . 14

Figure 10: Diffusion constant of hydrogen in Ferritic steels versus temperature (Coe and

Chano, 1975). The Figure clearly demonstrates that there is a sharp drop in diffusivity of

hydrogen when the temperature drops below 100 °C. ............................................................. 15

Figure 11: Heat loses and heat transfer in SMAW. ................................................................. 17

Figure 12: An example of the numerical modelling of the transient thermal field of a welded

pipe (Feli et al., 2011). ............................................................................................................. 21

List of Figures

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Figure 13: An example of numerical modelling of stress field of a welded pipe (Feli et al.,

2011). ....................................................................................................................................... 22

Figure 14: Heat conduction and convective heat transfer from surface resulting from a

moving heat source on the plate surface. ................................................................................. 26

Figure 15: 1D Gaussian heat source. ....................................................................................... 30

Figure 16: 2D Gaussian heat source. ....................................................................................... 31

Figure 17: Goldak et al.’s 3D heat source................................................................................ 32

Figure 18: Application of the method of Mirror Images to the fundamental solution (7). ...... 36

Figure 19: Thermocouple diagram........................................................................................... 38

Figure 20: Various types of thermocouple enclosure options. ................................................ 40

Figure 21: K-type thermocouple setup to record the thermal history of the welded plate

(Attarha and Sattari-Far, 2011). ............................................................................................... 40

Figure 22: Example of a plunged thermocouple in a weld seam (Moore, 2003). .................... 41

Figure 23: Components of the temperature measurement and recording system. .................. 42

Figure 24: Signal “Hockey Puck” Transmitter, a) and Signal Isolators, b)

(Ocean Controls, 2014; RS Australia, 2014). .......................................................................... 43

Figure 25: Wavelength sections within the Electromagnetic Spectrum (Heaviside, 2011). ... 44

Figure 26: Microbolometer Pixel. ............................................................................................ 45

List of Figures

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Figure 27: Typical examples of ZnSe (a) and Ge (b) optical windows (Knight Optical, 2014).

.................................................................................................................................................. 46

Figure 28: Typical transmissivity percentages of a variety of window materials against

wavelengths absorbed for SW and LW thermal cameras (Robinson, 2014). .......................... 47

Figure 29: Geometrical equivalence of the V groove and bead on plate welds with regard to

thermal distribution. ................................................................................................................. 52

Figure 30: Pipeline girth welding procedure. .......................................................................... 53

Figure 31: Schematic diagram to illustrate the mirror image method for pipes. ..................... 54

Figure 32: Representation of a pipe model (Equation (30)) which incorporates heat loss at the

free boundary surface. .............................................................................................................. 56

Figure 33: Lincoln Electric Invertec 415V, 3 Phase welding machine (WESS, 2014). .......... 60

Figure 34: Head Mount Signal “Hockey Puck” Transmitter (from PR Electronics 5331)

(RS Australia, 2014). ............................................................................................................... 60

Figure 35: Equipment setup for recording thermal history with thermocouples. .................... 61

Figure 36: Fitted ZnSe window to rubber manifold. ............................................................... 63

Figure 37: Transmissivity vs spectral range. ........................................................................... 63

Figure 38: Infrared Camera fitted with ZnSe window manifold. ............................................ 64

Figure 39: Infrared camera affixed to tripod............................................................................ 64

Figure 40: Plate test sample specifications. The R-type thermocouple is shown to illustrate

the temperature data acquisition technique. ............................................................................. 65

List of Figures

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Figure 41: Top view of plate test sample with run on/run off tabs. ......................................... 66

Figure 42: Plate sample with tabs mounted on welding jig. .................................................... 67

Figure 43: Complete plate test setup with data acquisition equipment. .................................. 68

Figure 44: Local joint geometry specification of pipe test sample. ......................................... 71

Figure 45: Axial locations of K-type thermocouples. .............................................................. 71

Figure 46: Setup and data acquisition equipment for the pipe test. ......................................... 72

Figures 47(a) and (b): Experimental setup of the pipe test sample.......................................... 73

Figure 48: Infrared camera and pipe test sample setup. ........................................................... 74

Figure 49: Typical thermal histories acquired with the K and R-type thermocouples from the

plate test. .................................................................................................................................. 76

Figure 50: Thermal history of point B30°, see Fig. 45. The pipe is welded with the weld start

angle, ϕ30°, Tph = 25 °C and h = 6 mm. ................................................................................... 76

Figure 51: Typical thermal images captured during welding (left image) and cooling (right

image) of the pipe test sample. ................................................................................................ 77

Figure 52: Thermal history of thermal image sequence generated with IRBIS 3.0 of point

B90° on pipe welded with weld start angle, ϕ90°, Tph = 25 °C and h = 6 mm. .......................... 78

Figure 53: Example of weld metal thermal history. Symbols represent experimental

measurements and the solid line is the theoretical prediction utilising Equations (13) and (26).

.................................................................................................................................................. 80

List of Figures

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Figure 54: Calculated t8/5 cooling times with correction for local geometry (filled symbols)

and without (un-filled symbols) plotted against measured t8/5 cooling times of V groove

welding tests............................................................................................................................. 81

Figure 55: Calculated t8/5 cooling times with the equivalent thickness approach and variable

arc efficiency (filled symbols) and without (un-filled symbols) plotted against measured t8/5

cooling times of previous V groove welding tests performed with various root gaps. ........... 83

Figure 56: Comparison of thermocouple measurements and modelling predictions for 220

OD pipe welded with pipeline welding procedure ϕ30° and ϕ90° at B30° (a) and B90° (b)

respectively. Tph = 25 °C and h = 6 mm. ................................................................................ 86

Figure 57: Comparison of thermocouple readings and modelled predictions for 220 mm OD

pipe welded with pipeline welding procedure ϕ90°, h = 12.5 mm for Tph = 25 °C (a) 70 °C (b)

and 100 °C, respectively (c). .................................................................................................... 87

Figure 58: Comparison of thermocouple and infrared camera data thermal histories for pipe

welding procedure using weld start angle ϕ90° at B90°. Tph = 25 °C and h = 6 mm. ............... 89

Figure 59: Cooling time t100 along the pipe circumference for ϕ30° and h = 12.5 mm. .......... 91

Figure 60: Cooling time t100 along the pipe circumference for ϕ90° and h =12.5 mm. ........... 91

Figure 61: Cooling time t100 along the pipe circumference for ϕ30° and h = 6 mm. ............... 92

Figure 62: Cooling time t100 along the pipe circumference for ϕ90° and h = 6 mm. ............... 92

Figure 63: Cooling time t100 along the pipe circumference for ϕ30° and heat input of 0. 8 kJ

mm-1

. ........................................................................................................................................ 93

List of Figures

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Figure 64: Cooling time t100 along the pipe circumference for ϕ90° and heat input of 0.4 kJ

mm-1

. ........................................................................................................................................ 93

List of Figures

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List of Tables

Table 1: Arc efficiencies of various welding processes, η. ..................................................... 18

Table 2: Classification of Analytical Thermal Field Models................................................... 23

Table 3: Joint characteristics of the plate test samples. ........................................................... 69

Table 4: Welding parameters applied to each sample in the plate test. ................................... 69

Table 5: Dimensions of pipe test samples................................................................................ 74

Table 6: Welding parameters applied to the pipe test samples in Table 5. .............................. 75

Table 7: General high temperature region thermal properties of most steels. ......................... 79

Table 8: Geometry factors for various test piece thicknesses used in V groove welding tests.

.................................................................................................................................................. 82

Table 9: Determined weld arc efficiencies for V groove welds of various nominal thicknesses

and root gap.............................................................................................................................. 82

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Table of Contents

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Table of Contents

Chapter 1: Introduction .......................................................................................................... 1

Chapter 2: Literature Review................................................................................................. 7

2.1 Welding ....................................................................................................................... 7

2.1.1 Pipeline construction ............................................................................................ 9

2.1.2 Effect of Temperature History on Weld Quality ............................................... 12

2.2 Thermal efficiency of welds ...................................................................................... 17

2.2.1 Comments on Numerical Approaches ............................................................... 20

2.3 Analytical Modelling of Thermal History ................................................................. 23

2.3.1 Point Heat Source Models ................................................................................. 24

2.3.2 Line heat source models..................................................................................... 28

2.3.3 Advanced heat source models ............................................................................ 29

2.4 Summary and Research Gap ..................................................................................... 33

Chapter 3: Research Methodology ...................................................................................... 35

3.1 Mathematical Modelling ........................................................................................... 35

3.2 Summary of Experimental Techniques ..................................................................... 37

3.2.2 Principles of thermal imaging ............................................................................ 44

Table of Contents

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Chapter 4: Development of Thermal Field Models for Pipeline Girth Welding ................. 49

4.1 Incorporation of the local preparatory joint geometry into a modelling approach ... 49

4.1.1 Thermal field model ........................................................................................... 50

4.1.2 Account for shape of V groove joint geometry: Equivalent thickness approach ..

............................................................................................................................ 52

4.2 Incorporation of pipeline girth welding procedure into modelling approach ........... 53

4.2.1 Development of thermal field model ................................................................. 54

4.3 Chapter Summary ...................................................................................................... 58

Chapter 5: Experimental studies .......................................................................................... 59

5.1 Experimental Equipment ........................................................................................... 59

5.1.1 Welding machine and consumables ................................................................... 59

5.1.2 Setup of temperature data recording equipment ................................................ 60

5.1.3 Software ............................................................................................................. 61

5.1.4 Thermocouple Calibration ................................................................................. 61

5.1.5 Temperature data acquisition with Infrared Camera ......................................... 62

5.2 Plate Tests ................................................................................................................. 65

5.3 Pipe Tests .................................................................................................................. 70

5.4 Selected examples of the recorded temperature history ............................................ 75

Table of Contents

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5.5 Chapter Summary ...................................................................................................... 78

Chapter 6: Thermal Field Model for Pipeline Girth Welding ............................................. 79

6.1 Evaluation of Thermal Arc Efficiency during Pipeline Girth Welding .................... 79

Chapter 7: Effect of Welding Procedure on Thermal History ............................................. 85

7.1 Validation of pipeline welding procedure model with temperature data .................. 85

7.1.1 Comparison of thermal histories obtained with different data acquisition

techniques ......................................................................................................................... 88

7.2 Temperature Variation across the Pipe Circumference ............................................. 89

7.3 Chapter Summary ...................................................................................................... 94

Chapter 8: Overall Conclusion ............................................................................................ 95

8.1 Publications from current research ............................................................................ 97

References……………………………………………………………………………………………………………...…99