Managing Ageing Assets as Part of the Clean Energy Transition

As the UK reduces its reliance on coal and oil, Aniqah Majid speaks to the Health and Safety Executive (HSE) about risk factors to look out for as assets age and operators look to repurpose them

LAST September, the UK said farewell to the Ratcliffe-on-Soar Power Station in Nottingham (pictured below), the last coal-fired plant in the country, marking the end of 140 years of the British coal industry.

The shutdown, and upcoming decommissioning of the 2 GW capacity facility, comes as part of the UK’s commitment to the 2015 Paris Agreement, and its plan to completely phase out coal.

Dominated by its eight 114 m cooling towers, work at the plant is far from over, however, with operators Uniper devising a redevelopment plan.

The energy company is discussing with stakeholders and Rushcliffe Borough Council the potential use of the site for advanced manufacturing, low-carbon energy production, and energy storage.

The facility is one of many ageing UK assets and infrastructure previously used in the coal or oil and gas industry that could be repurposed for cleaner energy production.

Working with ageing assets, which account for more than 70% of world production across industries according to engineering consultancy Vysus Group, is a challenge in terms of process safety. Though ageing and near end-of-life assets are not directly linked with an increased risk of accidents, it is a relevant indicator for the likelihood of risks becoming more prevalent.

The UK regulator, the Health and Safety Executive (HSE), says that plant operators should be aware of “creeping changes”. The principal specialist inspectors in both mechanical engineering and process safety departments told IChemE that companies should have a process for managing change over time and identifying hazards.

The regulator lays out a series of precautions to look out for to ensure that the running of a plant remains efficient and, most importantly, safe, no matter what it produces.

Risk factors to look out for

Above all factors, the HSE says that primary containment should be the first consideration for operators running ageing plant assets.

Containment of materials is a crucial part of safe transport, storage, and use of hazardous chemicals in industry. If there is a loss of containment those materials could lead to environmental contamination, injuries, and even death.

The most common causes of loss of primary containment (LOPC) are often linked to equipment design flaws, material degradation (arising from defects during manufacture and construction or wear and tear), and operating beyond design limits, including overpressure or excessive heat input.

A study by the European Commission’s Joint Research Centre on major accidents involving ageing plants highlighted the 2005 explosion at BP’s Texas City refinery as a case where “exceedance of equipment limitations became the norm”. The incident, caused by an overpressurised distillation tower, claimed the lives of 15 workers.¹

The HSE says that in controlling primary containment, operators need to have an “end of life” approach, where more inspection and maintenance is required to keep the risk of failure to acceptable levels.

A spokesperson for the HSE said: “Degradation due to ageing may not be linear, and indeed new mechanisms may manifest as an asset ages. Many standards in the petrochemical sector work on a half-life principle; as assets deteriorate, the inspection interval is set at half the remaining predicted life; such an approach works well if risks are identified (by HAZOP etc) and there is confidence in the asset history.”

Applications in new energy

Since 2018, Shell has been repurposing its Goldeneye gas production field to support the Acorn CCS project. This initiative will use the existing pipeline infrastructure to transport emissions from the St Fergus gas terminal to storage sites in the North Sea. As such projects evolve, adapting infrastructure originally designed for different purposes becomes critical.

“The operating and inspection history are again crucial to assessing condition prior to the change, but the nature of the threat is also likely to change too. For example, the introduction of hydrogen can bring additional risks from embrittlement for plant constructed from standard steels, with implications for crack propagation, fatigue life etc, that in turn necessitate differing inspection regimes and potentially shortening asset life.”

The HSE spokesperson explained that where a plant is being repurposed, operators need a robust process in place that considers threats to integrity. The established hazard identification processes help, but additional thought is needed when considering asset reliability and safe operation.

Operators must also be aware of their own shortcomings when it comes to inspection, namely the limitations of their inspection techniques, which they should accommodate in their fitness for service calculations, applying the worst-case scenario and being conservative.

These regular inspections and critique of practices lead into what the HSE describes as the “creeping change” involved in managing ageing assets and how operators can prepare for them.

The spokesperson said: “Slow changes may be more difficult to discern but are important to recognise and manage; for example, the Covid pandemic saw change in use for some plant, slowing of processes or even stagnation, introducing different degradation threats – discrete changes.”

As the UK transitions towards cleaner energy, the challenge of managing ageing assets remains pivotal. Repurposing sites like Ratcliffe-on-Soar and Goldeneye demonstrates the potential for innovation, but it also underscores the need for rigorous safety measures and proactive risk management. As the HSE says: “UK infrastructure needs a balanced approach, necessitating safe operation of existing assets while moving to net zero in accordance with government-stated aims.”

By embracing careful planning and continuous monitoring, the industry can navigate the evolving energy landscape while mitigating risks and protecting both people and the environment.

Reference

1. Chemical Engineering Transactions: Lessons Learned from Major Accidents Relating to Ageing of Chemical Plants: https://bit.ly/4asb6XB