Characterising thermal fatigue at mix points in industrial piping - NSIRC227 PhD Studentship - Sponsored by Lloyds Register Foundation

Background

Industrial pipelines are extensively used to transport fluids at high temperatures and pressures. This scope is crucial, especially for the Oil & Gas and Nuclear sectors, which are concerned about sharp temperature gradient fields. These temperature gradients are determined by flows mixing at different temperatures at the so-called mixing points. In addition, local geometry of pipes, such as elbows and T-junctions, can amplify the local thermal stresses which often result in fatigue cracking. Propagation of fatigue cracks is a phenomenon well understood in the nuclear industry but less so in other industries, and can lead to significant direct as well as indirect costs, such as pipe repair and replacement, loss of the contained fluid and disruption in the operational services. For the reasons mentioned above, it is important to identify a simple method to define the inspection regime and frequency, in order to detect thermal fatigue cracks, before their propagation can take place. In this way, an optimised maintenance of the pipeline would maximise life time and performance. Current guidelines in the petrochemical industry are broad and overly simplistic. When inspection regimes are not based on an understanding of the fundamental causes, components may be inspected too frequently (increasing costs), or critical regions may be not be inspected because they have not been identified (increasing risk of failure). Understanding of the key reasons and physical mechanisms leading to fatigue cracking is of paramount importance to extend the pipework life span and to optimise the working cycle.

Project Outline

Computational Fluid Dynamics (CFD) will be used in this project to:



• Characterise the thermal mixing process near the so-called mixing points;



• Identify suitable and measurable parameters to characterise thermal stresses in flow mixing;



• Develop a rule matrix through the above parameters which can be used by engineers to effectively identify high risk mixing points.

Therefore, this research will develop a broad understanding of the thermal flow mixing mechanism by making use of CFD to: a) identify critical regions in the pipework; b) assess severity of the thermal loads. The corresponding thermal fatigue load cycles in the pipework will therefore be used in fatigue assessments to predict the remaining life. Additionally, this research will define a validated rule matrix - to prioritise inspection modality, criticality and frequency as required. This can be used by engineers to define the overall inspection regime of industrial pipelines. This research will require an understanding of CFD, finite element analysis, fatigue assessment, and risk based inspection.

About NSIRC

NSIRC is a state-of-the-art postgraduate engineering facility established and managed by structural integrity specialist TWI, working closely with lead academic partner Brunel University, top UK and International Universities and a number of leading industrial partners. NSIRC aims to deliver cutting edge research and highly qualified personnel to its key industrial partners.

Candidate Requirements

Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree. Candidates with suitable work experience and strong capacity in numerical modelling and experimental skills are particularly welcome to apply. Overseas applicants should also submit IELTS results (minimum 6.5) if applicable