Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 222222
Loughborough University

Centre for Innovative and Collaborative Construction Engineering


Dr Colum Holtam


Structural Integrity Assessment of C-Mn Pipeline Steels Exposed to Sour Environments

Project Title

Structural Integrity Assessment of C-Mn Pipeline Steel Exposed to Sour Environments




I Ashcroft
R Thomson

Mr D Baxter
Mr Ian Partridge

Director of Research:
Professor Dino Bouchlaghem

Research Period

2006 - 2010

Structural Integrity Assessment of C-Mn Pipeline Steel Exposed to Sour Environments


The topic of the project is in line with TWI' s ambitions to develop technical expertise and business in the area of fitness for assessment of ageing structures. The work will focus on the extension and validation of the current assessment procedures in BS 7910,

API RP579 and British Energy's R6 procedures. The project will focus on corroding structures suffering environmentally assisted cracking and corrosion fatigue (although other damage mechanisms may also be investigated).

Aims and Objectives

  • To review the latest materials test methods and fitness for service assessment approaches for determining the integrity of flaws in aggressive corroding environment
  • To undertake a limited experimental and numerical modelling programme to validate existing or new procedures with respect to safe assessment of damaged structures
  • To provide guidance on the limitations of test methods and assessment procedures, and recommendations for the enhancements of existing methods and procedures

A wide range of material/enviromnent problems will be investigated. CMn or stainless steel in sour environment; stainless steel in nuclear PWR/BWR environments; C-Mn steel in methanol; etc. The project will examine the developments in materials testing methods and in-service assessment procedures for corroding welded structures, in the following principles areas:

  1. stress corrosion cracking, with respect to short-crack qualification test methods
  2. corrosion fatigue crack growth testing, concerning growth rates in the short-crack regime at delta-K values below the measured long-crack threshold
  3. assessment of multiple environmental cracks (so-called craze-cracking), regarding the new recommendations from FITNET and in API RP 579.

Method and Current Status

It is envisaged that existing laboratory testing equipment will be utilised for this EngDoc project, including fracture and fatigue rigs and environmental programmes.  Small-scale and full-scale experimental work will be required for validation activities and this is entirely within TWI's capabilities. The EngDoc project will also be supported by finite element analysis using TWI's existing facilities.

• State of the art guidelines on the methods and procedures for managing the integrity of environmentally damaged structures.

Benefits/Expected Outcomes

This is a project aimed at the capital-intensive sectors such as power and oil and gas operators. Companies operating in this sector will benefit through the application of new validated test methods and assessment procedures arising from this work, to the extend that they may safely extend the life of ageing welded structures (avoiding the need to immediately replacement structures). TWI will benefit through developing staff expertise; revenues from consultancy projects as well as the sale of software tools arising from this work (to be incorporated in, for example, ENGFit Toolbox); and finally reputation enhancement via eg. publications, contributions to standards, etc.










Holtam C.M. … et al. (2011). A Survey of Fitness-for-Service Trends in Industry. ASME. J. Pressure Vessel Technol. 133(1). 014001.

Holtam C.M., … et al. (2009). The behaviour of shallow cracks in a pipeline steel operating in a sour environment, Journal of Offshore Mechanics and Arctic Engineering (OMAE), August 2009, Vol. 131, 3, 031302, ASME.

Holtam C.M. … et al. (2010). Effect of crack depth on fatigue crack growth rates for a C-Mn pipeline steel in a sour environment, International Journal of Fatigue, Vol. 32 (2), pp. 288-296, Elsevier. [doi:10.1016/j.ijfatigue.2009.06.013].

Holtam C.M. … et al. (2010). An investigation into fatigue crack growth test methods in a sour environment, International Journal of Offshore and Polar Engineering, Vol. 20 (2), pp. 103-109.

Holtam, C,M. … et al. (2009). Influence of fatigue loading on engineering critical assessment of steel catenary risers in sour deepwater oil and gas development. Key Engineering Materials, Vols 413-414, pp. 313-325.  Trans Tech Publications, Switzerland. [10.4028/www.scientific.net/KEM.413-414.313].



Holtam C M, Baxter D P, Ashcroft I A and Thomson R C, 2008: 'The Behaviour of Shallow Cracks in a Pipeline Steel Operating in a Sour Environment', OMAE2008-57083, 27th International Conference on Offshore Mechanics and Arctic Engineering, ISBN 0-7918-3827-8, ASME.

Holtam C M, Baxter D P, Ashcroft I A and Thomson R C, 2008: 'A Survey of Fitness-for-Service Trends in Industry', Pressure Vessels and Piping Conference, ISBN 0-7918-3828-5, ASME.

Holtam, C, Baxter, D, Thomson, R and Ashcroft, I (2009).  An investigation into fatigue crack growth test methods in a sour environment. ISOPE Conference 2009

Holtam, C.M. and Baxter, D.P. (2007). Environment Assisted Cracking Assessment Methods: The Behaviour of Shallow Cracks, Ninth International Conference on Engineering Structural Integrity: Research, Development and Application, China Machine Press.



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The Centre Administrator
Loughborough University
LE11 3TU

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