Loughborough University Featured PhD Programmes
Sheffield Hallam University Featured PhD Programmes
Loughborough University Featured PhD Programmes

Characterization and early detection of hydrogen embrittlement in offshore boltsusing Acoustic Emission - funded by Lloyd’s Register Foundation (NSIRC228 PhD Studentship)


Applications accepted all year round Funded PhD Project (Students Worldwide)

About the Project


The effect of hydrogen on steel has been the subject of several investigations due to its ability to cause corrosion and cracking which has costly consequences on several industries. Absorption of hydrogen quantities as low as 0.0001 wt% into some metals can result in significant cracking and hence, considerations for this are required.

Large bolts and other connectors such as studs and fasteners, typically used in the offshore Energy and the oil and gas industries, have been reported to fail prematurely. A typical subsea O&G asset has a minimum of 10,000 bolted connections with larger assets having in excess of 100,000 joints. The failure of a bolted joint can result in catastrophic loss of the asset and loss of life, particularly those subjected to corrosive subsea environments. To prevent failure, a set of guidelines was published by the Energy Institute (an independent, not-for-profit, safe space for evidence-based collaboration) which outline the management of the integrity of bolted joints through non-destructive testing (NDT) techniques. These techniques are time consuming, costly and can require specialist equipment and personnel particularly when inspecting subsea equipment such as blow-out preventers. Despite this, failures still occur resulting from undetected HIC and international communities are working to reduce risk of failure in bolts related to bolts.

Hydrogen-Induced Cracking (HIC) (which is difficult to detect by conventional means) in bolts can lead to catastrophic failure such as the 2012 failure in the Gulf of Mexico which resulted in a leak of 432 barrels of drilling fluid.

Acoustic Emission (AE) is the spontaneous release of strain energy which is emitted during a damage event (such as corrosion or cracking). By placing sensors on a structure, AE emitted from damage can be detected and located and thus, the damage can be detected, located and characterised. By monitoring for AE over time, an assessment of a structures condition can be made and an estimate on the useful remaining life can be made.

AE has been demonstrated to detect HIC and other hydrogen embrittlement mechanisms early. Therefore, there is much interest to develop AE technology to explore the relationship between hydrogen embrittlement and AE for the monitoring of critical bolts, fastenings and connections.

Project Outline

The objective of this project will be to develop a methodology for using AE to monitor bolts for hydrogen embrittlement under representative in-service conditions. This will required the PhD candidate to conduct an in-depth review of the literature regarding hydrogen embrittlement and AE studies previously conducted.

This will lead on to the design and development of an experimental test program that will aim to establish the parameters and conditions for successfully detecting AE from hydrogen embrittlement. This will include establishing sensors with appropriate sensitivity and frequency response to maximise the probability of detection.

Through a process of experimental investigation, complexity in the structural monitoring will be increased (starting from simply structures leading to a fully bolted connection) with representative loading and conditions.

This process will acquire a large volume of data that will require the candidate to develop the data handling and processing methodologies in order to achieve successful detection. Data trend analysis, signal processing and data clustering techniques will be employed to differentiate AE from hydrogen embrittlement sources from sources resulting from background noise. The key aim of this will be to establish from the AE the exact point in which the different hydrogen embrittlement mechanisms occur and relate them to theory. This will enable a predictive model to be built which will determine the current condition of a bolt and its remaining useful life.

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

Funding Notes

This project is funded by TWI and Warwick University. The studentship will provide successful Home/EU students with a minimum stipend of £16k/year and will cover the cost of tuition fees. Overseas applicants are welcome to apply, with total funding capped at £24k per year

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